無線通訊協定 - 國立中興大學hwtseng/Wireless Networks/2CSMA_CA.pdfCSMA/CA - 34 Four PHYs • Frequency Hopping Spread Spectrum (FHSS)Frequency Hopping Spread Spectrum (FHSS)

CSMACA CSMACA -- 11

無線通訊協定無線通訊協定

CSMACA CSMACA -- 22

Outline

1 80211 Architecture and Overview2 Baseband Infrared (IR) Physical Layer

Specification3 Direct Sequence Spread Spectrum (DSSS)

Physical Layer Specification4 Orthogonal Frequency Division Multiplexing

(OFDM) Physical Layer Specification5 IEEE 80211g Extended Rate PHY (ERP)

Specification6 Frequency Hopping Spread Spectrum PHY

of the 80211 Wireless LAN Standard7 IEEE 80211 Wireless LAN MAC Standard

CSMACA CSMACA -- 33

1 80211 Architectureand Overview

CSMACA CSMACA -- 44

Technology Tree for Wireless LAN

HomeRFHomeRFBluetoothBluetooth

CSMACA CSMACA -- 55

What is unique about wireless

bullbull Difficult mediaDifficult mediandash interference and noisendash quality varies over space and timendash shared with Unwanted 80211 devicesndash shared with non-802 devices (unlicensed

spectrum microwave ovens microwave ovens bluetoothbluetooth etc etc)bull Full connectivity cannot be assumed

ndash Hidden node problemHidden node problembull Multiple international regulatory requirements

CSMACA CSMACA -- 66

Medium Variations

CSMACA CSMACA -- 77

Uniqueness of Wireless (continued)

bull Mobilityndash variation in link reliabilityndash battery usage requires power managementpower managementndash want seamless connections

bull Securityndash no physical boundariesndash overlapping LANs

CSMACA CSMACA -- 88

Requirements

bull Single MAC to support multiple PHYsndash Support single and multiple channel PHYsndash PHYs with different medium sense characteristics

bull Should allow overlap of multiple networks in the same area and channel space

bull Need to be Robust for Interferencendash ISM band (Industry Science and Medicine)

raquo 1356 MHz 2755 MHz 303 MHz 315 MHz 404 MHz 433 MHz 868 MHz (Europe) 915 MHz (North America) 245 GHz 52 GHz (North America) 53 GHz and 57 GHz (North America)

raquo Microwave other non-80211 interferersraquo Co-channel interference

bull Need mechanisms to deal with Hidden Nodes

bull Need provisions for Time Bounded Services

CSMACA CSMACA -- 99

Architecture Overview

bull One MAC supporting multiple PHYsndashndash Frequency Hopping Spread SpectrumFrequency Hopping Spread Spectrumndashndash Direct Sequence Spread SpectrumDirect Sequence Spread Spectrumndashndash InfraredInfraredndashndash Orthogonal Frequency Division Multiplexing Orthogonal Frequency Division Multiplexing

bull Two configurations ndashndash Independent Independent (ad hocad hoc) and InfrastructureInfrastructurendashndash Hybrid configuration has being studiedHybrid configuration has being studied

bullbull CSMACA (collision avoidance)CSMACA (collision avoidance) with optional Point Coordination Function (PCF)

CSMACA CSMACA -- 1010

80211 Protocol Entities

LLCLLC SAPSAP

MAC MAC SublayerSublayer

PLCP PLCP SublayerSublayer

PMD PMD SublayerSublayer

MAC LayerMAC LayerManagementManagement

PHY LayerPHY LayerManagementManagement

StationStationManagementManagement

MACMAC

PHYPHY


80211 Protocol Architecture

bull MAC Entityndash basic access mechanismndash fragmentationdefragmentationndash encryptiondecryption

bull MAC Layer Management Entityndash synchronizationndash power managementndash roamingndash MAC MIB

bull Physical Layer Convergence Protocol (PLCP)ndash PHY-specific supports common PHY SAPndash provides Clear Channel Assessment signal (carrier

sense)


80211 Protocol Architecture (cont)

bull Physical Medium Dependent Sublayer (PMD)ndash modulation and encoding

bull PHY Layer Managementndash channel tuning (channel switching delay 224us224us in

80211b)ndash PHY MIB

bull Station Managementndash interacts with both MAC Management and PHY

Management


80211 Configurations - Independent

bull Independentndash one Basic Service Set (BSS)ndashndash Ad HocAd Hoc networkndash direct communicationndash limited coverage area

bull Current research topicsndash Multi-Hop Routing (IETF MANET)ndash Multicastingndash Multi-channel Accessndash Securityndash QoS

StationAH3

Station

Station

AH1

AH2

Ad Hoc NetworkAd Hoc Network

Mobile Station STA


Commercial Products WLAN Cardsbull One piecebull Two pieces


80211 Configurations - Infrastructure

Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server

DISTRIBUTION SYSTEM (DS) Ethernet orInternet

bullbull InfrastructureInfrastructurendash Access Points (AP) and stations (STA)

bull Distribution System interconnects Multiple Cells via Access Points to form a single Network

ndash extends wireless coverage areabullbull Wireless bridgeWireless bridge application


Commercial Products AP


Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line

Data RateData RateCost Cost Legal Legal

Security Security Range Range

Building B Building A


Outdoor Application


Outdoor Application - Antenna


Outdoor Application


Long Distances

bull Security Issue ndash The transmission distance can be up to

25Miles25Miles

ndash If the AP is distanced from the street or on a high floor of a building users will be safe from network trespassers


Distribution System

bull Used to interconnect wireless cells ndash multiple BSS connected together form an ESS (Extended

Service Set)ndash Allows mobile stations to access fixed resources

bull Not part of 80211 standardndash could be bridged IEEE LANs wireless other networks ndashndash Only Distribution System Services are definedOnly Distribution System Services are defined


BSS vs ESS


Collocated Coverage Areas

DS Distribution System


Complete Architecture

DSS Distribution System Service


Access Points

bull Stations select an AP and Associate with it

bullbull Support Support roamingroamingndashndash IAPP (Inter Access Point Protocol) IAPP (Inter Access Point Protocol) IEEE 80211fIEEE 80211fndashndash Mobile IP Mobile IP

bull Provide other functionsndashndash time synchronizationtime synchronization (beaconing)ndashndash power managementpower management support (if any)ndashndash point coordination functionpoint coordination function (PCF) (if any)

bull Traffic typically (but not always) flows through APndash direct communication possible


Access Points

bull In an Infrastructure BSS all mobile stations communicate with the AP

ndash quoted from ldquoIEEE 80211 HandbookIEEE 80211 Handbookrdquordquo Bob OBob OrsquorsquoHara and Hara and AI AI PetrickPetrick

ndash Disadvantage raquo bandwidth is consumed twicetwice than directional

communication between STAsraquo more contentions and more collisions

ndash Advantage raquo easily solve hidden terminal problemraquo provide power saving functionraquo meet the AAA (authentication authorized accounting)

architectureraquo provide per flow bandwidth control QoS guarantee (in the

near future)


80211 Defines the Airwaves IF

bull The airwaves interface between stations (including that between station and AP) is standardized

ndash PHY and MAC

bull No exposed MACPHY interface specified

bull No exposed interface to Distribution Systemndash only required DS services are defined

bull Internals of Distribution System not defined


MAC Servicesbull Asynchronous MSDU Data Delivery

ndash provided to LLCLLC (2304 octets maximum)

bull Time Bounded Servicesndash optional point coordination function (PCF)ndash Existing in commercial products

raquo Bandwidth is not enough for supporting real-time serviceraquo Not necessary CSMACA works well (likes Ethernet history)raquo Digitalocean Corp ldquoStarfish IIrdquo AP raquo IEEE 80211e draft enhances QoS

bull Security Servicesndash confidentiality authentication access control

bull Management Servicesndash scanning joining roaming power management


MAC Functionality

bull Independent and Infrastructure configuration support

ndash Each BSS has a unique 4848 bit addressndash Each ESS has a variablevariable length address

bull CSMA with collision avoidance (CSMACA)ndash MAC level acknowledgment (positive acknowledgement)acknowledgment (positive acknowledgement)ndash allows for RTSRTSCTSCTS exchanges

raquoraquo hidden node protectionhidden node protectionraquoraquo virtual carrier sensevirtual carrier senseraquoraquo bandwidth savingbandwidth saving

ndash MSDU fragmentationndash Point Coordination Function option

raquo AP polling


MAC Functionality (continued)

bull Roaming support within an ESSndash station scansscans for APs associationassociation handshakes

bull Power management supportndash stations may power themselves downndashndash AP bufferingAP buffering distributed approach for IBSS

bull Authentication and privacyndash Optional support of Wired Equivalent Privacy (WEPWEP)ndash Key exchangendash Authentication handshakes definedndash IEEE 8021x spec enhances authentication controlndash IEEE 80211i draft enhances security


PHY Layer Services

bull PHY_DATA transfersndashndash multiple rates (1 2 55 11Mbps)multiple rates (1 2 55 11Mbps)ndashndash extended rates (22 33 or 6 9 12 19 24 36 48 extended rates (22 33 or 6 9 12 19 24 36 48

54Mbps)54Mbps)ndashndash The algorithm for performing rate switching is beyond The algorithm for performing rate switching is beyond

the scope of the standard (p6 80211b)the scope of the standard (p6 80211b)raquoraquo Question how to decide the proper data rate Question how to decide the proper data rate

bull Clear Channel Assessment (CCA)ndash carrier sensendash detect start frame delimiter

bull PHY Managementndash channel tuning


Data Rate vs Range


Four PHYs

bullbull Frequency Hopping Spread Spectrum (FHSS)Frequency Hopping Spread Spectrum (FHSS)ndashndash 24 GHz24 GHz band 11 and 22 Mbps transmission

raquo 2GFSK 4GFSK raquo 25 hopssec over 79 1MHz channels (North America)

bullbull Direct Sequence Spread Spectrum (DSSS)Direct Sequence Spread Spectrum (DSSS)ndashndash 24 GHz24 GHz band 11 and 22 Mbps transmission

raquo 11 chip Barker sequenceraquo DBPSK DQPSK (Differential BinaryQuadrature Phase Shift Keying)

ndashndash 24 GHz24 GHz band 5555 and 1111 Mbps transmission raquo CCK (Complementary Code Keying) PBCC (Packet Binary

Convolutional Code)raquo CCK DQPSK(55Mbps 11Mbps)raquo PBCC BPSK(55Mbps) QPSK(11Mbps) (optional)raquo Sep 1999 (80211b)

ndashndash 24 GHz24 GHz band 2222 and 3333 Mbps transmissionraquo PBCC-22 PBCC-33raquo Jan 2002 (80211g D21 - optional)


Four PHYsbullbull BasebandBaseband IR (Infrared)IR (Infrared)

ndash Diffuse infraredndashndash 1 1 and 22 Mbps transmission 16-PPM and 4-PPM

raquo PPM Pulse Position Modulationbullbull Orthogonal Frequency Division Multiplexing (OFDM)Orthogonal Frequency Division Multiplexing (OFDM)

ndashndash 24 GHz24 GHz band (IEEE 80211g D21 DSSS-OFDM OFDM)ndashndash 5 GHz5 GHz band (IEEE 80211a)

raquo Similar ETSI HIPERLANII PHY Specndashndash 66 99 1212 1818 2424 3636 4848 and 5454 Mbps

raquo BPSK(69Mbps) QPSK(1218Mbps) 16-QAM(2436Mbps) 64-QAM(4854Mbps)

raquo Convolutional Code with coding rates frac1223frac34 raquo 20MHz64 subcarriers per channel

bull 52 subcarriers occupy 166MHzbull 12 additional subcarriers are used to normalized the average power of

OFDM symbolraquo Mandatory 6 12 24 Mbpsraquo Extended (turbo mode 5-UP protocol) 72108Mbps (proposed by

Atheros Corp)


Unlicensed Operation RF Bands

bull 902MHzndash 26MHz BW (902-928MHz)ndash Crowded and Worldwide limitedndash IEEE 80211 WLAN IEEE 802154 LR-WPAN coreless phone etc

bull 24GHzndash 835MHz BW (2400-24835MHz)ndash Available worldwide ndash IEEE 80211(bg) WLAN Bluetooth IEEE 802154 LR-WPAN and HomeRF

etc

bull 51GHzndash 300MHz (three 100MHz segments) ndash Unlicensed NIIndash 80211a WLAN

raquo OFDM 6121824364854Mbps BPSKQPSK16-QAM 64-QAMndash HiperLAN I and HiperLAN II

raquo 235MbpsGMSK and 6-54MbpsBPSKQPSK16-QAM 64-QAM

ps 27MHz


2 Baseband Infrared (IR) Physical Layer Specification


PPM Modulationbull OOKPPM

ndash Reduce the optical power


3 Direct Sequence Spread Spectrum (DSSS) Physical Layer Specification


What is DSSS

bull Signal symbol is spread with a sequence

bull Wider Bandwidthbull Less power density

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency


11 chip BARKER sequencebull Good autocorrelation propertiesbull Minimal sequence allowed by FCCbull Coding gain 104 dB

+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion

Received chip stream at time (t-1)

Received chip stream at time (t)

Received chip stream at time (t+1)


DSSS benefits

bull 10 dB coding gainndash Robust against interferers and noise (10 dB

suppression)bull Robust against time delay spread

ndash Resolution of echoes

echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime


DSSS hardware block diagramDBPSKDBPSKDQPSKDQPSK


IEEE 80211 DSSS PHY characteristics

bullbull 24 GHz24 GHz ISM band (FCC 15247)bull 1 and 2 Mbs datarate

ndash DBPSK and DQPSK modulationndash Chipping rate 11 MHz11 MHz with 11 chip Barker sequence11 chip Barker sequence

bull 55 and 11Mbps (80211b)ndashndash CCKCCK (QPSK DQPSK modulations ndash mandatory)ndashndash PBCCPBCC (BPSK QPSK modulations ndash optional)

bull 22 and 33Mbps (80211g80211g))ndashndash PBCCPBCC--2222 PBCCPBCC--3333 modulation (TI proposal (TI proposal ndashndash optional)

bull Multiple channels in 24 to 24835 GHz band


DSSS Channels

CHNL_ID FrequenciesFCC

Channel Frequencies

ETSI ChannelFrequencies

Japan Frequency

(MKK)

Japan Frequency(New MKK)

1 2412 MHz X X - X 2 2417 MHz X X - X 3 2422 MHz X X - X 4 2427 MHz X X - X 5 2432 MHz X X - X 6 2437 MHz X X - X 7 2442 MHz X X - X 8 2447 MHz X X - X 9 2452 MHz X X - X

10 2457 MHz X X - X 11 2462 MHz X X - X 12 2467 MHz - X - X 13 2472 MHz - X - X 14 2484 MHz - - X X

Table 1 DSSS PHY Frequency Channel Plan

bull FCC(US) IC(Canada) and ETSI(Europe) 24GHz - 24835GHzbull Japan 2471GHz - 2497GHz (MKK channel 14 new MKK channels 1-14)bull France 24465GHz - 24835GHz (channels 10 11 12 13)bull Spain 2445GHz - 2475GHz (channels 10 11)bull Adjacent cells using different channels ge 30MHz (25MHz in

80211b)bull FCC pushes the unused unlicensed TV broadcasting band 365GHz-

370GHz as WLAN band


IEEE 80211 PHY Terminology in Spec(s)

bullbull 1 Mbps Basic Rate (BR)1 Mbps Basic Rate (BR)bullbull 2 Mbps Extended Rate (ER)2 Mbps Extended Rate (ER)bullbull 5511 Mbps High Rate (HR)5511 Mbps High Rate (HR)bullbull 22~336~54 Mbps Extended Rate PHY (ERP)22~336~54 Mbps Extended Rate PHY (ERP)


PLCP Frame Formats in IEEE 80211b

bull Two different preamble and header formats

ndashndash Long PLCP PPDU formatLong PLCP PPDU format (Mandatory in 80211bMandatory in 80211b)raquo 144-bit preamble 1Mbps DBPSKraquo 48-bit header 1Mbps DBPSKraquo Spend 192usraquo PSDU 1 2 55 11Mbpsraquo Compatible with 1 and 2 Mbps

ndashndash Short PLCP PPDU formatShort PLCP PPDU format (Optional in 80211bOptional in 80211b)raquo Minimize overhead maximize data throughputraquoraquo 7272-bit preamble 1Mbps DBPSKraquo 48-bit header 2Mbps DQPSKraquo Spend 96usraquo PSDU 2 55 11 Mbps


PLCP (PHY Convergence) Sublayer

LLCLLC SAPSAP







MACMAC

PHYPHY


Long PLCP Frame Format

Preamble and Header always at 1Mbs DBPSK Barker

1Mbps DBPSK Barker 2Mbps DQPSK Barker55 11Mbps DQPSK CCK

1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits

Long PLCP Preamble144 bits in 1 Mbps

Long PLCP Header48 bits in 1 Mbps

PSDUMPDU1 2 55 11 Mbps

bull Mandatory in 80211b


DBPSK Modulation

I

Q

I

Q

Bit Input Phase Change (+jω)0 01 π

Table 1 1 Mbs DBPSK Encoding Table


DQPSK Modulation

I

Q

Dibit pattern (d0d1)d0 is first in time Phase Change (+jω)

00 001 π211 π10 3π2 (-π2)

Table 1 2 Mbs DQPSK Encoding Table


PLCP synchronization

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits




bull 128 one bits (lsquo1rsquo)bull scrambled by scramblerbull Used for receiver to clock on to the signal and to correlate

to the PN code


Start Frame Delimiter

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits




bull 16 bit field (hF3A0)bull used for

ndash bit synchronization


Signal Field

bull 8 bitsbull Rate indication

ndash h0A 1Mbs DBPSKndash h14 2Mbs DQPSKndash h37 55Mbs CCK or PBCCndash h6E 11Mbps CCK or PBCC

bull Other values reserved for future use (100 kbs quantities)

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits




bull Reserved for future usendash Bit 2 locked clock bit

raquo Indicate transmit freq (mixer) amp symbol clocks (baseband) derived from same oscillator

raquo optional in 80211b and mandatory in 80211gndash Bit 3 modulation selection

raquo 0 CCK 1 PBCC ndash Bit 7 length extension bit (in the case datarate gt 8Mbps)

bull h00 signifies 80211 compliant


Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits



PSDUMPDUPSDUMPDU1 2 55 11 Mbps 1 2 55 11 Mbps

bull Indicates number of micosceonds to be transmitted in PSDUMPDU

ndash Decided by Length and datarate (in TXvector)bull Used for

ndash End of frame detectionndash Perform Virtual Carrier Sense (for those with lower datarate)ndash MPDU CRC sync


CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits




bull CCITT CRC-16bull Protects Signal Service and Length Field


CRC Implementation


Short PLCP Frame Format in 80211b

2Mbps DQBSK5511Mbps CCK

1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits

Short PLCP Preamble72 bits in 1 Mbps

Short PLCP Header48 bits in 2 Mbps

PSDUMPDU2 55 11 Mbps

bull Optional in 80211b

2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits




bull 56 zero bits (lsquo0rsquo)bull scrambled by scrambler with seed lsquo0011011rsquobull Used for receiver to clock on to the signal and to correlate

to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits




bull 16 bit field (h05CF)bull used for



Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits




bull Rate indicationndash h14 2Mbs DQPSKndash h37 55Mbs CCK or PBCCndash h6E 11Mbps CCK or PBCC



Data ScramblerDescrambler

bull ALL bits transmittedreceived by the DSSS PHY are scrambleddescrambled


PLCP Transmit Procedure


PLCP Receive Procedure


Complementary Code Keying (CCK)

bull HRDSSS adopts 88--chipchip CCK as the modulation scheme with 11MHz11MHz chipping ratechipping rate

bull It provides a path for interoperability with existing 12 Mbps Spec

8-chip1375MHz = 11MHz chipping rate



bull Spreading code length = 8 c=c0-c7 and

where ϕ1 is added to all code chips ϕ2 is added to all odd code chips ϕ3 is added to all odd pairs of code chips and ϕ4 is added to all odd quads of code chips

Cover codeCover code c4 and c7 chips are rotated 180deg (with -) by a cover sequence to optimize the sequence correlation properties and minimize dc offsets in the codes


Complementary Code Keying (CCK) 55Mbps

bull At 55Mbps CCK 4 data bits (d0d1d2d3) are transmitted per symbol

bull (d0d1) is DQPSK modulated to yield ϕ1 which the information is bear on the ldquophase changerdquo between two adjacent symbols

bull (118)(4 data bits per symbol)1Mbps = 55Mbps



bull (d2d3) encodes the basic symbol where



bull At 11Mbps CCK 8 data bits (d0-d7) are transmitted per symbol


bull (d2d3)(d4d5)(d6d7) encode ϕ2 ϕ3 ϕ4 respectively based on QPSK





Packet Binary Convolutional Code (PBCC)

bull 64-state BCC

QPSK 11MbpsBPSK 55Mbps


Packet Binary Convolutional Code (PBCC)bull PBCC convolutional encoder

ndash Provide encoder the ldquoknown staterdquoraquo 6 memory elements are needed and raquo one octet containing all zeros is appended to the end of

the PPDU prior to transmissionbullbull One more octet than CCKOne more octet than CCK

ndash For every data bit input two output bits are generated


Packet Binary Convolutional Code (PBCC)bull For 11Mbps two output bits (y0y1) produce one symbol via

QPSKndash one data bit per symbol

bull For 55Mbps each output bit (y0 or y1) produces two symbols via BPSK

ndash One-half a bit per symbol


Packet Binary Convolutional Code (PBCC)bull Pseudo-random cover sequence

ndash use 16-bit seed sequence (0011001110001011) ndash to generate 256-bit pseudo-random cover sequence


Transmit Spectrum Mask

fcfc -11 MHzfc -22 MHz

Sinxx

fc +11 MHz fc +22 Mhz

0 dBr

-30 dBr

-50 dBr

UnfilteredTransmitSpectrumMask


Clear Channel Assessment

bull Five methodsndash CCA mode 1 Energy above threshold (detect energy) (11b-

HR 11g-ERP)ndash CCA mode 2 Carrier sense only (detect DSSS signal)ndash CCA mode 3 Carrier sense with energy above threshold

(2Mbps)ndash CCA mode 4 Carrier sense with timer (11b-HR)

raquo 365ms is the duration of the longest possible 55Mbps PSDUndash CCA mode 5 Carrier sense (detect DSSS signal) with

energy above threshold (55Mbps 11Mbps) (11b-HR 11g-ERP)

bull Energy detection function of TX power in modes 1 amp 3ndash Tx power gt 100mW -80 dBm (-76dBm in mode 5)ndash Tx power gt 50mW -76 dBm (-73dBm in mode 5)ndash Tx power lt= 50mW -70 dBm (-70dBm in mode 5)

bull Energy detect time 15 microsbull Correct PLCP header --gt CCA busy for full (intended)

duration of frame as indicated by PLCP Length field


DSSS Specification Summary

bull Slottime 20 us20 usbull TX to Rx turnaround time 10 usbull Rx to Tx turnaround time 5 us bull Operating temperature range

raquo type 1 0 - 40 oCraquo type 2 -30 - 70 oC

bull Tx Power Levelsraquo 1000 mW USA (FCC 15274)raquo 100 mW Europe (ETS 300-328) (=20dbm)raquo 10 mWMHz Japan (MPT ordinance 49-20)

bull Minimum Transmitted Power 1 mWbull Tx power level control required above 100 mW

ndash four power levels


DSSS Specification Summary (cont)

bull Tx Center Frequency Tolerance ++-- 25 25 ppmppmbull Chip Clock Frequency Tolerance ++-- 25 25 ppmppmbull Tx Power On Ramp 2 microsbull Tx Power Down Ramp 2 microsbull RF Carrier suppression 15 dBbull Transmit modulation accuracy test procedurebull Rx sensitivity -80 dB (-76dbm)

008FER (1024 Bytes)lt 010FER (1000 Bytes) in 11g

bull Rx max input level -4 dB (-10dbm)bull Rx adjacent channel rejection gt35 dB

gt 30(25)30(25) MHz separation between channels


4 Orthogonal Frequency Division Multiplexing (OFDM) Physical Layer Specification


IEEE 80211a PLCPbull TxVector RxVector

ndash length 1-4095 octetsndash Mandatory data rates 6 12 24 Mbpsndash 8 power levels


IEEE 80211a PLCP


IEEE 80211a PLCP frame format

PLCP Header

CodedOFDM(BPSK r =12)

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits

PLCP PreamblePLCP Preamble12 Training Symbols

SIGNALSIGNALOne OFDM Symbol

DATADATAVariable Number of OFDM Symbols

Reserved1 bit

Tail6 bits

PSDU

CodedOFDM(RATE is indicated in SIGNAL)

6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits

PLCP PreamblePreamble12 Training Symbols



Reserved1 bit

Tail6 bits

PSDU

1 preamble field contains ndashndash 10 short training sequence10 short training sequence

raquo used for AGC convergence diversity selection timing acquisition and coarse frequency acquisition in the receiver

ndashndash 2 long training sequence2 long training sequenceraquo used for channel estimation and fine frequency acquisition in the receiver

ndash and a guard interval (GI)


PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU

RATERATE4 bits4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits

PLCP Preamble12 Training Symbols



Reserved1 bit

Tail6 bits

PSDU

bull Data Rates (determined from TXVECTOR)ndash 1101 6Mbps (M)ndash 1111 9Mbpsndash 0101 12Mbps (M) ndash 0111 18Mbpsndash 1001 24Mbps (M)ndash 1011 36Mbpsndash 0001 48Mbpsndash 0011 54Mbps


Rate-dependent Parameters

(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

TailTail6 bits6 bits

PSDU

bull 6 lsquozerorsquo bitbullbull to make the length of SIGNAL field to be 24 bits to make the length of SIGNAL field to be 24 bits

(for the (for the NNDBPSDBPS=24=24 in 6Mbps mode)in 6Mbps mode)bull to facilitate a reliable and timely detection of the

RATE and LENGTH fields


PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDUSERVICESERVICE16 bits16 bits

For synchronizationFor synchronization


PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit

TailTail6 bits6 bits Pad BitsPad Bits




Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits

bull Append 6 non-scrambled tail bits for PSDU to return the convolutional code to the ldquozero staterdquo

bull Add pad bitspad bits (with ldquozerordquo and at least 6 bits) such that the length of DATA field is a multiple of NNDBPSDBPS


PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUPSDUSERVICE16 bits

11 encodeencode data string with convolutional encoder (include punctured coding)22 dividedivide encoded bit string into groups of NNCBPSCBPS bits3 within each group perform data interleavinginterleaving4 For each of the groups convert convert bit string group into a complex number according to

the modulation tables (see next page)5 divide the complex number string into groups of 4848 complex numbers each such

group will be associated with one OFDM symbolone OFDM symbolbullbull map to map to subcarrierssubcarriers ndashndash2626~~--22 22 --20~20~--8 8 --6~6~--1 1~6 8~20 22~261 1~6 8~20 22~26bullbull 44 sucarrierssucarriers ndashndash21 21 --7 7 21 are used for pilot7 7 21 are used for pilotbullbull subcarriersubcarrier 0 is useless0 is useless

66 convert convert subcarrierssubcarriers to time domain using inverse Fast Fourier transform (IFFT)to time domain using inverse Fast Fourier transform (IFFT)77 append OFDM symbols after SINGNAL and unappend OFDM symbols after SINGNAL and un--convert to RF freqconvert to RF freq


Modulation Tables


Convolutional Encoder

bull use the industry-standard generator polynomials ndash g0 = 1338 and g1 = 1718 of rate R = 12

(first output)

(second output)


Punctured Codingbull to omit some of the encoded bits in the transmitter

ndash thus reducing the number of transmitted bits and increasing the coding rate

ndash inserting a dummy ldquozerordquo metric into the convolutional decoder on the receive side

ndash decoding by the Viterbi algorithm is recommended


Timing-related Parameters

bull Slot time 9usbull CCA detect time lt 4us


OFDM PHY Characteristics

bull OFDMbull Slottime 9 us9 usbullbull SIFSSIFS 16 us (6us for decoder)16 us (6us for decoder)bull CCA Time lt 4 usbull TX to Rx turnaround time lt 10 usbull Rx to Tx turnaround time lt 5 us bull Preamble Length 16 usbull PLCP Header Length 4 usbull MPDUmax Length 4095bull aCWmin 15 bull aCWmax 1023


Channelizationbullbull 8 independent channels in 515GHz8 independent channels in 515GHz--535GHz535GHzbullbull 4 independent channels in 57254 independent channels in 5725--5825GHz5825GHz


PCLP Transmit Procedure


PCLP Receive Procedure


IEEE 80211a vs IEEE 80211b (max)1500 bytes per frame1500 bytes per frame

Refer from Refer from ldquoldquoAtherosRangeCapacityPaperpdfAtherosRangeCapacityPaperpdfrdquordquo


IEEE 80211a vs IEEE 80211b (average)1500 bytes per frame1500 bytes per frame



IEEE 80211a vs IEEE 80211b (average)for a cell radius of 65 feet

Cell allocation


IEEE 80211a vs IEEE 80211b (average)






5 IEEE 80211g Extended Rate PHY (ERP) Specification


IEEE 80211g bullbull Extended Rate PHY (ERP) Goal Extended Rate PHY (ERP) Goal

ndashndash coexists with 80211b coexists with 80211b ((helliphellip))ndashndash enhances the ability of interference protectionenhances the ability of interference protection

bullbull ERPERP--DSSSCCK (Mandatory) DSSSCCK (Mandatory) (125511 Mbps)(125511 Mbps)ndash short PLCP PPDU is mandatoryndash transmit center frequency and symbol clock frequency shall refer the

same oscillator (locked oscillator mandatory)

bullbull ERPERP--OFDM (Mandatory) OFDM (Mandatory) (69121824364854 Mbps)(69121824364854 Mbps)ndash Optional 9 us slot time when the BSS consists of only ERP devices

bullbull ERER--PBCC (Optional) PBCC (Optional) (55112233 Mbps)(55112233 Mbps)ndash 256-state binary convolutional code

bullbull ERPERP--DSSSDSSS--OFDM (Optional) OFDM (Optional) (69121824364854 Mbps)(69121824364854 Mbps)ndash Hybrid modulation ndash DSSS for preamble and headerpreamble and headerndash OFDM for data payloaddata payload


IEEE 80211g PCLP

bullbull ThreeThree different mandatorymandatory PLCP PPDU formatndash Long Preamble and header (same as 11b) (for DSSS-OFDM and

ERP-PBCC)

ndash Short Preamble and header (same as 11b) (for DSSS-CCK)

raquo Differences in SERVICE fieldbull Diff 1 a bit in SERVICE field is used to indicate DSSS-OFDMbull Diff 2 two bits in SERVICE field are used to resolve the length

ambiguity for PBCC-22 and PBCC-33

ndash OFDM preamble and header (similar as 11a) (for ERP-OFDM)

b0b0 B1B1 b2b2 b3b3 b4b4 b5b5 b6b6 b7b7

Modulation Modulation selectionselection0 = Not 0 = Not DSSSDSSS--OFDMOFDM1 = DSSS1 = DSSS--OFDMOFDM

ReservedReserved Locked Locked Clock BitClock Bit0 = not 0 = not lockedlocked1 = locked1 = locked

ModulationModulationSelectionSelection0 = CCK0 = CCK1 = PBCC1 = PBCC

ReservedReserved Length Length ExtensionExtensionBitBit(PBCC)(PBCC)

Length Length Extension Extension Bit Bit (PBCC)(PBCC)

Length Length Extension Extension BitBit


LongShort PLCP for PBCC-22 and PBCC-33

PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits


Long PLCP Header48 bits


bull Rate indicationndash h0A 1Mbs DBPSK (for long only)ndash h14 2Mbs DQPSK ndash h37 55Mbs CCK or PBCCndash h6E 11Mbps CCK or PBCCndash hDC 22Mbps PBCC-22ndash h21 33Mbps PBCC-33


PBCC-22 in 80211gbull 256-state binary convolutional code of rate R=23bull PBCC-22 convolutional encoder



ndash For every pair of data bits input three output bits are generated (R=23)

Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g

bull For 22Mbps three output bits (y0y1y2) produce one symbol via 88--PSKPSK

ndash two data bits per symbol


PBCC-33 in 80211g

bull Upgrade the 80211b 11Msps (in 20MHz bandwidth)11Msps (in 20MHz bandwidth) as 165Msps165Msps

bull by using pulse shaping and adaptive equalizationbull enhance 50 data rate

Preamble Encoded Data

11Msps11Msps

Shift

165Msps165Msps

Clock Switch

(10 clock cycles10 clock cycles)

ReSyncTail Head

Clock Switch

11Msps11Msps 165Msps165Msps


Long PLCP for 80211g DSSS-OFDM

SYNC(128 bits --Scrambled

Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)

PLCPPreamble(144 bits)

PLCP Header(48 bits)

PPDUPPDU

PSDU(Data Modulation)

OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps

OFDMModulation6-54 Mbps

80211Long PLCP


Short PLCP for 80211g DSSS-OFDM

SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits --Reversed

SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP


DSSS-OFDM PLCP PSDU Encoding

GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU

Data SymbolsDSSS-OFDM

Signal Extension(6 useconds)

LongTrainingSymbol(32us)

GuardInterval(08 us)

Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)

Quiet time no transmission

OFDM DataSymbols at 6 912 18 24 3648 or 54 Mbps

rate


PLCP PreambleHeaderPLCP PreambleHeader


Single-Carrier to Multi-carrier transition

Barker Preamble1 Mbps

Barker Header1 or 2 Mbps

OFDMat 6 9 12 18 24 36 48 and 54 Mbps

Single Carrier Segment at 11 MHz QPSK Symbol Rate

Multi-carrier Carrier Segment at 20 MHz kernel sample rate

Ideal Transition Specificationbull Constant Powerbull Constant Spectrumbull Constant Frequency and Phasebull Constant Timing



OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

bull The signals are easily aligned by first aligning the 11 MHz clock and the 20 MHz clock on 1 us boundaries

111vs

120


Single-Carrier to Multi-carrier transitionbull The signals are easily aligned by first aligning the 11 MHz

clock and the 20 MHz clock on 1 us boundaries

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec

Single-CarrierLast BarkerWordOf Header

Pulses AlignedOn Zero-PhasePeaks

Multi-CarrierOFDM RampUp

time

time

20 MHz Samples ofOFDM as described in Annex G of the 80211a standard

11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate


Single-Carrier to Multi-carrier transitionbull The single carrier segment of a packet should terminate in

nominally 01 us (100ns)

Single CarrierBPSKQPSKBarker Codes

Multi-CarrierOFDM

time

ShapedIdentical to 80211a

Shaped Consistent With 80211a

~100nsecs


Extended Rate PHY Characteristics

bull ERP-OFDMbull Slottime Long Long 20 us (DSSS)20 us (DSSS)

Short 9 usShort 9 us (OFDM)(OFDM)SIFS 10SIFS 1016 us16 usbull CCA Time Long lt 15 us

Short lt 4 usbull TX to Rx turnaround time lt 10 usbull Rx to Tx turnaround time lt 5 us bull Preamble Length 20 usbull PLCP Header Length 4 usbull MPDUmax Length 4095bull aCWmin(0) 31 (for 11b)bull aCWmin(1) 15 (for 11g OFDM)bull aCWmax 1023


6 Frequency Hopping Spread Spectrum PHY of the 80211 Wireless LAN Standard


Why Frequency Hopping

bull Frequency Hopping is one of the variants of Spread Spectrum- a technique which enables coexistence of multiple networks (or other devices) in same area

bull FCC recognizes Frequency Hopping as one of the techniques withstanding Fairness requirements for unlicensed operation in the ISM bands

bull 80211 Frequency Hopping PHY uses 7979 nonoverlappingfrequency channels with 1 MHz1 MHz channel spacing

bull FH enables operation of up to 26 collocated networksup to 26 collocated networks enabling therefore high aggregate throughput

bull Frequency Hopping is resistant to multipath fading through the inherent frequency diversity mechanism


Regulatory requirements for FH

bull North America (CFR47 Parts 15247 15205 15209)ndash Frequency band 2400-24835 MHzndash At most 1 MHz bandwidth (at -20 dB re peak)ndash At least 75 hopping channels pseudorandom hopping patternndash At most 1 W transmit power and 4 W EIRP (including antenna)

bull Europe (ETS 300-328 ETS 300-339)ndash Frequency band 2400-24835 MHzndash At least 20 hopping channelsndash At most 100 mW EIRP

bull Japan (RCR STD-33A)ndash Frequency band 2471-2497 MHzndash At least 10 hopping channels


80211 FH PHY vs Regulations

bullbull 1 MHz1 MHz Bandwidthbullbull 7979 hopping channels in North America and

Europe pseudorandom hopping pattern (2402-2480GHz)

bullbull 2323 hopping channels in Japan (2473-2495GHz)bull At most 1 W power devices capable of more than

100 mW have to support at least one power level not exceeding 100 mW


80211 FHSS Modulation Objectives

bull Achieving at least 1 Mbitsec ratebull Familiar field proven low cost technology - FSK

ndash Constant Envelope- Saturated Amplifiersndash Limiter-Discriminator detection

bull Multichannel operation transmit signal shaping to reduce adjacent channel interference


80211 FHSS Modulation

bull Gaussian shaped FSK (GFSK) at Fclk = 1 Msymbolsec

ndash NRZ data is filtered with BT=05 low-pass Gaussian filter (500 KHz bandwidth at 3 dB) and then FM modulates a carrier

bull 1 or 2 Mbitsec with multilevel GFSKndash 1 Mbitsec 2 level GFSK h2=034ndash 2 Mbitsec 4 level GFSK h4=045h2=015

bull 1 Mbitsec operation mandatory 2 Mbitsec-optional

ndash facilitates production of interoperable lower-ratelower-cost and higher-ratehigher-cost equipment


80211 FHSS Frame Format

80 16 12 4 16 variable length

rampup

rampdown

PLCP preamble PLCP headerPLWPSF CRC

PLCP_PDUpayload data


Always at 2GFSK At 2GFSK or 4GFSK

bull PHY header indicates payload rate and length CRC16 protected

bull Data is whitened by a synchronous scrambler and formatted to limit DC offset variations

bull Preamble and Header always at 1 Mbitsec Data at 1 or 2 Mbitsec


PLCP Preamble

bull PLCP preamble starts with 80 bitsndash 0101 sync patternndash detect presence of signalndash to resolve antenna diversityndash to acquire symbol timing

bull Follows 16 bit Start Frame Delimiter (SFD)ndash h0CBD ndash the SFD provides symbol-level frame synchronizationndash the SFD pattern is balanced


PLCP Header

bull A 32 bit PLCP header consists of ndash PLW (PLCP_PDU Length Word) is 12 bit field

raquo indicating the length of PLCP_PDU in octets including the 32 bit CRC at the PLCP_PDU end in the range 0 4095 (the same as IEEE 80211a)(the same as IEEE 80211a)

ndash PSF (PLCP Signaling Field) is 4 bit field raquo Bits 0 is reservedraquo Bit 1-3 indicates the PLCP_PDU data rate

bull (1 15 2 25 3 35 4 45 Mbits)

ndash HEC is a 16 bit CRC


PLCP_PDU Formatting

bull Dividing serial bit stream into symbolsndash at 1 Mbps each bit is converted into 2FSK symbolndash at 2 Mbps each 2 bits are encoded into 4FSK symbol

using Gray mapping


Indoor Environment - Multipath Fading

bull Multiple propagation paths interfering with each other create a frequency selective fading

bull The fades are correlated at adjacent frequencies and get decorrelated after few megahertz in an indoor environment


Frequency Hopping Sequences (1)

bull Design Criteriandash Assured minimum hop distance for multipath diversity

performance (6 channels in North America and Europe 5 channels in Japan)

ndash Minimizing hits and adjacent channel hits between different hopping patterns

ndash Minimizing consecutive hits between different hopping patterns

bull FCC 15247 requirement Pseudorandomlyordered frequency list



bull Hop Sequence ndash 1amp2Mbps hopping patterns are divided into three sets

raquo 26 sequences per set for North America and Europeraquo 4 sequences per set for Japan

ndash High rate (channel agility in 80211b) hopping patterns are divided into two sets

raquo first set uses non-overlapping frequency channelsbull minimize interference degradationbull 2530MHz center frequency spacing for North AmericaEuropebull 3 sequences per set for North America and Europe

raquo second set uses half overlapping frequency channelsbull 10MHz center frequency spacingbull 67 sequences per set for North AmericaEuropebull interoperability with 1amp2Mbps FH systems


7 IEEE 80211n Next Generation WLAN


IEEE 80211n

bull Next Generation Wireless LAN expectationsndash Over 100Mbpsndash Maybe standardized in 2007-2008

bull Increasing channel sizendashndash SpectrallySpectrally - Wider bandwidth channels

raquo 40MHz per channel (vs 20MHz)ndashndash SpatiallySpatially - MIMOMIMO Smart Antenna spatial streams

bull Improving channel utilization

bull Industry activities


MIMO - Smart Antenna Multiplexing

bull Use multiple antennas to digitally process multiple signals

bull Distinct spatial streams simultaneously transfer unique data

bull Theoretical performance increases linearly with number of antennas


Smart Antenna - Spatial Diversitybull Digital Maximal Ratio Combining (MRC)bull Signals coherently combined (unlike noise) to improve

signal gainbull Diversity can incrementally enhance spatial multiplexing

and wider bandwidth channelsbull Spatial differences between antennas enable recombining

MRC can improve range up to 14 times


100 Mbps Implementation Comparisons

(1085448)times2=243


7 IEEE 80211 Wireless LAN MAC Standard


Wireless LAN Architecture

bull Major differences between Wireless LAN and Wired LANs

ndash Destination Address Does not Equal Destination Location

raquo In wired LANs an address is equivalent to a physical address In 80211 the addressable unit is a station (STA) The STA is a message destination but not a fixed location

ndash The Media Impacts the Designraquo The PHY layers used in 80211 are fundamentally different

from wired media 80211 PHYsbull Have limited physical point to point connection rangesbull Use a medium sharedbull Are unprotected from outside signalsbull Are significantly less reliable than wired PHYsbull Have dynamic topologies



bull Impact of Handling Mobile Stationsndash A portable station is one that is moved from location to

location but is only used while at a fixed locationndash Mobile stations actually access the LAN while in motionndash Propagation effects blur the distinction between

portable and mobile stationsbull Interaction With Other 802 Layers

ndash 80211 is required to appear to higher layers (LLC) as a current 802 style LAN Station mobility has to be handled within the MAC layer


80211 Wirelss LAN Characteristics

bull 1 2 55 11 22 33 6 9 12 18 24 36 48 54 Mbpsbull IEEE 80211 CSMACA Framebull Transmission Medium Radiobull CSMACA (Carrier Sense Multiple Access with Collision

Avoidance) Protocolndash Provides priority scheme

bull Provides delay guaranteed transmission service CSMACA avoids most of the collisions so that the transmission delay can be guaranteed

bull Bandwidth Fairness is not guaranteed By employing the CSMACA protocol the bandwidth employed by each station may be different

ndash Needs load sharing scheme in the near future



bull Changes and additions to IEEE Std 80211-1999

bull (1) IEEE Std 80211a80211a-1999--High-speed Physical Layer Extension in the 5 GHz Band

ndash Frequency range 515-525 525-535 and 5725-5825 GHzndash System orthogonal frequency division multiplexing (OFDM)ndash Data payload communication capability 6 9 12 18 24 36 48 and 54

Mbps

bull (2) IEEE Std 80211b80211b-1999--High-speed Physical Layer Extension in the 24 GHz Band

ndash Frequency range 24 - 24835 GHzndash System Direct Sequence Spread Spectrum (DSSS)ndash Data payload communication capability 1 2 55 and 11Mbps



bull (3) IEEE Std 80211g80211g-2003mdashFurther Higher-Speed Physical Layer Extension in the 24GHz Band

ndash Frequency range 24 GHzndash System hybrid DSSS and OFDMndash Data payload communication capability 22 33 6 9 12 18 24

36 48 and 54 Mbps

bull (4) IEEE Std 80211e80211e-2003mdashMedium Access Control (MAC) Enhancements for Quality of Services (QoS)

bull (5) IEEE Std 80211i80211i-2003mdashEnhanced Securityndash WEPndash TKIPndash WRAPndash CCMP


80211 Architecture Components

bull Wireless Medium (WM) ndash The medium used to implement a wireless LAN

bull Station (STA)ndash Any device that contains an 80211 conformant MAC and PHY interface

to the wireless medium

bull Station Services (SS) ndash The set of services that support transport of MSDUs (MAC Service Data

Units) between Stations within a BSS

bull Basic Service Set (BSS) ndash A set of STAs controlled by a single CF (Co-ordination Function)ndash The BSS is the basic building block of an 80211 LAN The members of

a BSS can communicate to each other directly ndash If a station moves out of its BSS coverage area it can no longer

directly communicate with other members of the BSS

bull The Independent BSS as an Ad-Hoc Networkndash This mode of operation is possible when 80211 LAN stations are close

enough to form a direct connection (without pre-planning)



bull Distribution System (DS)ndash A system used to interconnect a set of BSSs to create an ESSndash Used in Infrastructure Network

bull Distribution System Medium (DSM)ndash The medium used by a DS (for BSS interconnections)ndash 80211 logically separates the WM from the DSM Each logical medium

is used for different purposes by a different component of the architecture

ndash The DS enables mobile device support by providing the logical services necessary to handle address to destination mapping and seamless integration of multiple BSSs



bull Distribution System Services (DSS)ndash The set of services provided by the DS

which enable the MAC to transport MSDUsbetween BSSs within an ESS

bull Access Point (AP)ndash Any entity that has STA functionality and

provides access to the DSndash An AP is a STA which provides access to

the DS by providing DS services in addition to Station Services

ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1BSS 2BSS 2

AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點



bull STA to AP Association is Dynamicndash The association between a station and a BSS is dynamic (STAs turn

on turn off come within range and go out of range)ndash To become a member of an infrastructure BSS a station must become

Associated

bull Distributed System Conceptsndash Extend an 80211 network with multiple BSSs named as ESSndash The architecture component used to interconnect BSSs is the

Distributed System



bull ESS The large coverage networkndash The DS and BSSs allow 80211 to create a wireless network of

arbitrary size and complexity

bull Extended Service Set (ESS)ndash A set of interconnected BSSs which appears as a single BSSndash The ESS network appears the same to an LLC layer as an

independent BSS networkndash Stations within an ESS can communicate and mobile stations

may move from one BSS to another (within the same ESS) transparently to LLC

bull Basic Service Area (BSA)ndash The area within which members of a BSS can communicate

bull Extended Service Area (ESA)ndash The area within which members of a ESS can communicate An

ESA is larger than or equal to a BSA



bull The following are possiblendash The BSSs may partially overlap This is commonly

used to arrange contiguous coverage within a physical volume

ndash The BSSs could be physically disjointndash The BSSs may be physically collocated

This might be done to provide redundancy

bull Max number of overlapping BSSsndash 3 in DSSS 24GHzndash 26 in FHSS 24GHzndash 12 in OFDM 5GHz

bullbull Question Is it possible for a single Question Is it possible for a single BSS to utilizes multiple channels STA 4STA 4

BSS 2BSS 2 STA 6STA 6

DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5

BSS to utilizes multiple channels



ndash One (or more) independent BSS or ESS networks may be physically present in the same space as one (or more) ESS networks

raquo An ad-hoc network is operating in a location which also has an ESS network

raquo Physically adjacent 80211 networks have been set up by different organizations


Integration with Wired LANsbull To integrate the 80211 architecture with a traditional

wired LAN a logical architecture component (Portal) is introduced

bull All data from non-80211 LANs enters the 80211architecture via a portal

STA 4STA 4

BSS 2BSS 2

IEEE 802X區域網路

DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges

bull Bridges were originally designed to provide range extension between like-type MAC layers

bull In 80211 arbitrary range (coverage) is provided by the ESS architecture (via the DS and APs) making the PHY range extension aspects of bridges unnecessary

bull Bridges are also used to interconnect MAC layers of different types Bridging to the 80211 architecture raises the questions of which logical medium to bridge to the DSM or the WM

bull The portal must also consider the dynamic membership of BSSs and the mapping of address and location required by mobility

bull Physically a portal may or may not include bridging functionality depending on the physical implementation of the DS


Logical Service Interface

bull The DS may not be identical to an existing wired LAN and can be created from many different technologiesincluding current 802x wired LANs

bull 80211 does not constrain the DS to be either Data Link or Network Layer based Nor constrain a DS to be either centralized or distributed

bull 80211 specifies services instead of specific DS implementations Two categories of services are defined Station Service (SS) and Distribution System Service (DSS)

bull The complete set of 80211 architectural services are1 Authentication2 Association3 Disassociation4 Distribution5 Integration

6 Reassociation7 Deauthentication8 Privacy9 MSDU delivery


Logical Service Interfacebull Station Service (SS)

ndash Present in every 80211 station including APsndash Are specified for use by MAC layer entitiesndash The SS subset is

raquo Authenticationraquo Deauthenticationraquo Privacyraquo MSDU delivery

bull Distribution System Servicesndash Used to cross media and address space

logical boundariesndash Provided by the DSndash They are accessed via a STA which also

provides DSSndash The DSS subset is raquoAssociation

raquoDisassociationraquoDistributionraquoIntegrationraquoReassociation

STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution


Multiple Logical Address Spaces

bull The WM DSM and an integrated wired LAN may all be different physical media Each of these components may be operating within different address spaces

bull 80211 only uses and specifies the use of WM addressspace

bull Each 80211 PHY operates in a single medium WMbull 80211 has chosen to use the IEEE 802 48-bit address

spacebull A multiple address space example is one where DS uses

network layer addressing In this case the WM address space and the DS address space would be different


Overview of the Services

bull There are nine services specified by 80211 Six to support MSDU delivery between stations and three to control 80211 access and confidentiality

bull Each of the services is supported by one or more MAC frames

bull Some of the services are supported by MAC Managementmessages and some by MAC Data messages

bull 80211 MAC layer uses three types of messagesndash Data handled via the MAC data service pathndash Management handled via the MAC Management Service

data pathndash Control

bull The following examples assume an ESS network environment


Distribution of Message Within a DS

bull Distributionndash The service which (by using Association information)

delivers delivers MSDUsMSDUs within the DSwithin the DSbull Consider a data message being sent from STA1 to STA4

via STA2 (Input AP) and STA3 (Output AP) The input AP gives the message to the Distribution Service of the DS

bull How the message is delivered within the DS is not specified by 80211

bull All 80211 is required is to provide the DS with enough information for the DS to be able to determine the output point which corresponds to the desired recipient The necessary information is provided to the DS by the three Association related services

ndash Associationndash Reassociationndash Disassociation



bull Integrationndash The service which enables delivery of delivery of MSDUsMSDUs between between

the DS and an existing networkthe DS and an existing networkbull If the Distribution Service determines that the intended

recipient of a message is a member of an integrated LAN the output point would be a Portal instead of an AP

bull Messages which are distributed to a Portal cause the DS to invoke the Integration service (conceptually after the Distribution Service)

bull The Integration service is responsible for accomplishing whatever is needed to deliver a message from the DSM to the integrated LAN media including any required media or address translation


Distribution Services (14)

bull The information required for the Distribution service to operate is provided by the Association services

bull Before a data message can be handled by the Distribution service a STA must be Associated

bull Mobility typesndash No-transition

raquo Static - no motionraquo Local movement - movement within a Basic Service Area

ndash BSS-transition movement from one BSS in one ESS to another BSS within the same ESS

ndash ESS-transition movement from one BSS in one ESS to another BSS in an independent ESS

bull Different Association services support the different categories of mobility


Distribution Services (24)bull Association

ndash The service which establishes an initial Association between a station and an access point

bull Before a STA is allowed to send via an AP it must first become associated with the AP

bull At any given time a mobile STA may be associated with no more than one AP This ensures that the DS can determine which AP is serving a specified STA

bull An AP may be associated with many mobile STAs at one time

bull A station learns what APs are present and requests to establish an association by invoking the Association service

bull Association is always initiated by the mobile STAbull Association is sufficient to support no-transition mobilitybull Association is necessary but not sufficient to support

BSS-transition mobility



bull Reassociationndash The service which enables an established Association (of a

STA) to be transferred from one AP to another AP (within an ESS)

bull The Reassociation Service is invoked to move a current association from one AP to another This keeps the DS informed of the current mapping between AP and STA as the station moves from BSS to BSS within an ESS

bull Reassociation also enables changing association attributes of an established association while the STA remains associated with the same AP

bull Reassociation is always initiated by the mobile STA



bull Disassociation ndash The service which deletes an existing Association

bull The Disassociation Service is invoked whenever an existing Association must be terminated and can be invoked by either party to an Association (mobile STA or AP)

bull Disassociation is a notification (not a request) and can not be refused by either party to the association

bull APs might need to disassociate STAs to enable the AP to be removed from a network for service or for other reasons

bull STAs are encouraged to Disassociate whenever they leave a network


Access and Confidentiality Control Services (12)

bull Wired LAN design assume the closed non-shared nature of wired media The open shared medium nature of an 80211 LAN violates those assumptions

bull Two services are required for 80211 to provide functionality equivalent to that which is inherent to wired LANs

ndash Authentication used instead of the wired media physical connection

raquo Now be further enhanced with IEEE 8021x port-based authentication

ndash Privacy used to provide the confidential aspects of closed wired media

raquo Now be further extended IEEE 80211i enhanced sceuritybull Authentication

ndash The service used to establish the identity of Stations to each other



bull In a wired LAN access to a physical connection conveys authority to connect to the LAN This is not a valid assumption for a wireless LAN

bull An equivalent ability to control LAN access is provided via the Authentication service which is used by all stations to establish their identity with stations they wish to communicate with

bull If a mutually acceptable level of authentication has not been established between two stations an association shall not be established


Authentication Service

bull 80211 supports a general authentication ability which is sufficient to handle authentication protocols ranging from unsecured to public key cryptographic authentication schemes (OPEN systemOPEN system and Shared KeyShared Key)

bull 80211 provides link level (not end-to-end or user-to-user) authentication between 80211 stations

bull 80211 authentication is simply used to bring the wireless link up to the assumed physical standards of a wired link If desired an 80211 network can be run without authentication

bull 80211 provides support for challengeresponse (CR) authentication The three steps of a CR exchange are

ndash Assertion of identityndash Challenge of Assertionndash Response to Challenge



bull Examples of a CR exchange arebull An open system example

(a) Assertion Im station 4(b) Challenge Null(c) Response Null(d) Result Station becomes Authenticated

bull A password based example(a) Assertion Im station 4(b) Challenge Prove your identity(c) Response Here is my password(d) Result If password OK station becomes Authenticated

bull A Cryptographic challengeresponse based example(a) Assertion Im station 4(b) Challenge Here is some information (X) I encrypted with

your public key what is it (c) Response The contents of the challenge is X (only station

4s private key could have recovered the challenge contents)(d) Result OK I believe that you are station 4



bull 80211 uses 80210 services to perform the actual challenge and response calculations A Management Information Base (MIB) function is provided to support inquires into the authentication algorithms supported by a STA

bull 80211 requires mutually acceptable successful bi-directionalauthentication

bull A STA can be authenticated with many other STAs (and hence APs) at any given instant

bull The Authentication service (could be time consuming) can be invoked independently of the Association service

bull Pre-authentication is typically done by a STA while it is already associated with an AP which it previously authenticated with

bull 80211 does not require that STAs pre- authenticate with APs bull However Authentication is required before an Association

can be established Thus pre-authentication can speedup the reassociation process


Privacy and Access Control

bull Goal of 80211 is to provide Wired Equivalent Privacy (WEP)ndash Usable worldwide

bull 80211 provides for an Authentication mechanismndash To aid in access controlndash Has provisions for OPEN Shared Key or proprietary

authentication extensionsbull Optional (WEP) Privacy mechanism defined by 80211

ndash Limited for Station-to-Station traffic so not ldquoend to endrdquoraquo Embedded in the MAC entity

ndash Only implements Confidentiality functionndash Uses RC4 PRNG algorithm based on

raquo a 40-bit secret key (No Key distribution standardized) bull by external key management service

raquo and a 24-bit IV that is send with the dataraquo 40+24 = 64-bit PRNG seed (new 128 152 bits - performane)raquo includes an ICV to allow integrity check

ndash Only payload of Data frames are encryptedraquo Encryption on per MPDU basis


Privacy MechanismWEP encipherment WEP decipherment

WEPPRNG

Initialization Vector (IV)

IV

Secret KeyCiphertext

ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV

Preamble PLCP Header MAC Header CRC

Encrypted

IV (4) ICV (4)Cyphertext

Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload

bull WEP bit in Frame Control Field indicates WEP usedndash Each frame can have a new IV or IV can be reused for a limited

timendash If integrity check fails then frame is ACKed but discarded


Privacy Service (12)

bull Privacyndash The service used to prevent the contents of messages

from being reading by other than the intended recipient

bull In a wired LAN only those stations physically connected to the wire can hear LAN traffic This is not true for the 80211 wireless LAN

bull 80211 provides the ability to encrypt the contents of messages

bull IEEE 80210 SDE clause 2 is used to perform the encryption A MIB function is provided to inquire the encryption algorithms supported by a station

bull A mutually acceptable privacy algorithm must be agreed upon before an Association can be established



bull The default privacy algorithm for all 80211 stations is in the clear If the privacy service is not invoked to set up a privacy algorithm all messages will be sent unencrypted

bull If a privacy algorithm is set up then the algorithm will be used for all subsequent transmissions

bull Even if an Association is successful a later Reassociationmay be refused

bull 80211 specifies an optional privacy algorithm that is designed to satisfy the goal of wired LAN equivalent privacy


Relationship Between Servicesbull For a station two state variables are required to keep track

ndash Authentication State Unauthenticated and Authenticated

ndash Association State Unassociated and Associatedbull Three station states are possible

ndash State 1 Initial start state Unauthenticated Unassociated

ndash State 2 Authenticated not Associatedndash State 3 Authenticated and Associated

bull These states determine the 80211 frame types (grouped into classes) which may be sent by a station

ndash State 1 Only Class 1 frames are allowedndash State 2 Either Class1 or Class 2 are allowedndash State 3 All frames (Class 3) are allowed


Relationship Between State Variables and Services

State 1Unauthenticated

Unassociated

State 2AuthenticatedUnassociated

State 3Authenticated

Associated

SuccessfulAuthentication

SuccessfulAssociation or Reassociation

DisassociationNotification

DeAuthenticationNotification

Class 1 framesClass 1 frames

Classes 1 2 framesClasses 1 2 frames Classes 1 2 3 framesClasses 1 2 3 frames


Frame Types

bull Class 1 framesndash Control Frames

(1) RTS(2) CTS(3) ACK(4) CF-End+ACK(5) CF-End

ndash Management Frames(1) Probe RequestResponse(2) Beacon(3) Authentication

raquo Successful association enables Class 2 framesraquo Unsuccessful association leaves STA in State 1

(4) DeauthenticationReturn State 1

(5) Announcement traffic indication message (ATIM)ndash Data Frames

(1) In IBSS direct data frames only (FC control bits To DS and from DS both false)

Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types

bull Class 2 Framesndash Data Frames

(1) Asynchronous data Direct data frames only (FC control bits To DS and from DS both false)

ndash Management Frames(1) Association RequestResponse


(2) Reassociation requestresponseraquo Successful association enables Class 3 framesraquo Unsuccessful association leaves STA in State 2

(3) DisassociationReturn State 2

PS When STA A receives a non-authenticated frame from STA BSTA A sends a deauthentication to STA B


Frame Typesbull Class 3 Frames

ndash Data Frames(1) Asynchronous data Indirect data frames allowed (FC

control bits To DS and from DS may be set to utilize DS Services)

ndash Management Frames(1) Deauthentication

raquo Return state 1

ndash Control Frames (1) PS-Poll


Differences Between ESS and Independent BSS LANs

bull An independent BSS (IBSS) is often used to support an Ad-Hoc network in which a STA communicates directly with one or more other STAs

bull IBSS is a logical subset of an ESS and consists of STAs which are directly connected

bull Since there is no physical DS there cannot be a Portal an integrated wired LAN or the DS Services

bull In an IBSS only class 1 frames are allowed since there is no DS in an IBSS

bull The services which apply to an IBSS are the Station Services

STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3


Frame and MPDU Formats

bull Each frame should consist of three basic components

ndash A MAC Header which includes control information addressing sequencing fragmentation identification duration and QoS information

ndash A variable length Frame Body which contains information specify to the frame type

ndash A frame check sequence (FCS) which contains an IEEE 32-bit cyclic redundancy code (CRC)


Frame Formats

FrameControl

DurationID

Addr 1 Addr 2 Addr 3 Addr 4SequenceControl CRCFrame

Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag

bull MAC Header format differs per Typendash Control Frames (several fields are omitted)ndash Management Framesndash Data Frames

bull Includes Sequence Control Field for filtering of duplicate caused by ACK mechanism


Address Field Description

To DS From DS Address 1 Address 2 Address 3 Address 40 0 DA SA BSSID NA 0 1 DA BSSID SA NA 1 0 BSSID SA DA NA 1 1 RA TA DA SA

bull Addr 1 = All stations filter on this addressbull Addr 2 = Transmitter Address (TA)

ndash Identifies transmitter to address the ACK frame tobull Addr 3 = Dependent on To and From DS bitsbull Addr 4 = Only needed to identify the original source of

WDS ((Wireless Distribution System)Wireless Distribution System) framesbull BSSID

ndash infrastructure AP MAC addressndash Ad Hoc 01 + 46-bit random number (may set as lsquo1rsquo)


Frame Fields

bull Frame Control Field ndash Protocol Version the value of the protocol version is zero

A device that receives a frame with a higher revision level than it supports will discard the frame without indication to the sending STA or to LLC

ndash Type and Subtype used to identify the function of the framendash To DS is set to 1 in data type frames destined for the DS via

APAP ndash From DS is set to 1 in data type frames existing the DSndash More Fragment is set to 1 if there has another fragment of the

current MSDU or MMSDUndash Retry Indicates that the frame is a retransmission of an earlier

frame A station may use this indication to eliminate duplicate frames

ndash Power Management Indicates power management mode of a STA A value of 1 indicates that the STA will be in power-save mode A value of 0 indicates that the STA will be in active mode This field is always set to 0 in frames transmitted by an AP


Frame Fields

ndash More Data is used to indicate to a STA in power-save mode that more MSDUs or MMSDUs are buffered for that STA at the AP or indicate that at least one additional MSDU buffered atSTA available for transmission in response to a subsequent CF-Poll

ndash WEP It is set to 1 if the Frame Body field contains information that has been processed by the WEP algorithm

ndash Order is set to 1 in any data type frame that contains an MSDU or fragment which is being transferred using the Strictly Ordered service class

bull Duration or Connection ID Used to distribute a value (us) that shall update the Network Allocation VectorNetwork Allocation Vector (NAV)(NAV) in stations receiving the frame


DurationID Field

bull In PS-Poll control frame DurationID carries association ID (AID) with the 2 MSB set as 1 (AID range 1-2007)

bull other types carries duration in usbull Transmitted frames in CFP duration is set as 32768

Bit 15 Bit 14 Bits 13-0 Usage0 0-32767 Duration (us)

1 0 0 Fixed value within framestransmitted during the CFP

1 0 1-16383 Reserved

1 1 0 Reserved

1 1 1-2007 AID in PS-Poll frames

1 1 2008-16383 Reserved


Frame Fieldsbull Address Fields Indicate the BSSID SA DA TA

(Transmitter address) RA (Receiver address) each of 48-bit address

bull Sequence Controlndash Sequence Number (12-bit) An incrementing value The same

value shall be used for all fragments of the same MSDUndash Fragment Number (4-bit) Indicates the number of each

individual fragmentbull Frame Body 0 ndash 2312(2310) bytesbull CRC (4 octets)

MSDU

MACHDR CRCFrame BodyFrame Body MAC

HDR CRCFrame Body MACHDR CRCFrame Body MAC

HDR CRCFrame Body

Fragment 1 Fragment 2 Fragment 3 Fragment 4


Format of Individual Frame Types

bull Control Framesndashndash Immediately previous Immediately previous frameframe means a frame the reception of which

concluded within the prior SIFS interval

bull RTS Frame Formatndash In an infrastructure LAN the DA shall be the address of the AP with

which the station is associated In an ad hoc LAN the DA shall be the destination of the subsequent data or management frame

bull CTS Frame Formatndash The DA shall be taken from the source address field of the RTS frame

to which the CTS is a response

bull ACK Frame Formatndash The DA shall be the address contained in the Address 2 field of the

immediately previous Data or Management frame

bull PS-Poll Frame Formatndash The BSS ID shall be the address of the AP The AID shall be the value

assigned by the AP in the Association Response frame The AID value always has its two significant bits set to 1


Format of Individual Frame Types (control frames)

Frame Control Duration RA TA FCS

MAC HeaderBit 7654

Subtype 1011 RTS Frame

Frame Control Duration RA FCS

MAC Header

Subtype 1100 CTS Frame

Frame Control

Duration RA FCS

MAC Header

Subtype 1101 ACK Frame

Frame Control

AID BSSID TA FCS

MAC Header

Subtype 1010 PS-Poll Frame



Frame Control Duration RA BSSID FCS

MAC Header

Bit 7654Subtype1110 CF-End Frame

MAC Header

Frame Control Duration RA BSSID FCSSubtype1111 CF-End+CF-Ack Frame

The BSSID is the address of the STA contained in the AP The RA is the broadcast group addressThe Duration field is set to 0



bull Data Framesndash The contents of the Address fields shall be dependent upon

the values of the To DS and From DS bitsndash A station shall use the contents of Address 1 to perform

address matching for receive decisionsndash The DA shall be the destination of the frame (MSDU)ndash The RA shall be the address of the AP in the wireless DS that

is the next immediate intended recipient of the framendash The TA shall be the address of the AP in the wireless DS that

is transmitting the framendash The BSSID

raquo The AP address if the station is an AP or associated with an APraquo The BSS ID of the ad hoc LAN if the station is a member of an

ad hoc LANndash The frame body is null(0 octets in length) in data frames of

subtype null function (no data) CF-Ack (no data) CF-Poll (no data) and CF-Ack+CF-Poll (no data)


Data Frames

Frame Control

DurationConn ID Addr 1 Addr 2

Sequence Number

Fragment Number Addr 4 FCSData

MAC Header

Addr 3

02312

To DS From DS Addr 1 Addr 2 Addr 3 Addr 40 0 DA SA BSSID NA0 1 DA BSSID SA NA1 0 BSSID SA DA NA1 1 RA TA DA SA


Frame Exchange Sequences

bull The following frame sequences are possiblendash Datandash Data - ACKndash RTS - CTS - Data - ACKndash Data - ACK - Data - ACK (Fragmented MSDU)ndash RTS - CTS - Data - ACK - Data - ACK (Fragmented MSDU)ndash Poll - Data - ACKndash Poll - Data - ACK - Data - ACK (Fragmented MSDU)ndash Poll - ACK (No data)ndash ATIM ndash ACKndash Request (management Probe Request)ndash Request - ACK (management)ndash Response - ACK (management)ndash CTS - Data (11g)ndash CTS - Management (11g)ndash CTS - Data - ACK (11g)ndash CTS - Data - ACK - Data - ACK (Fragmented MSDU) (11g)



bull Management Framesndash The BSSID

raquo The AP address if the station is an AP or associated with an AP

raquo The BSS ID of the ad hoc LAN if the station is a member of an ad hoc LAN

ndash The Frame body shall be the information elementsinformation elements

Frame Control

DurationAID

DA SA Sequence Control CRCFrame Body

MAC Header

BSSID


Management Frames (Frame Body)ndash BEACON Frame Time stamp beacon intervalCapability

information SSID supported rates FH Parameter Set DS parameter Set CF Parameter Set IBSS Parameter Set and TIM ( the parameter sets are present only when the functions are used)

raquo In 80211g new ldquoERP InformationERP Information ElementElementrdquo and ldquoExtended Extended Supported RatesSupported Rates ElementElementrdquoare added

ndash ATIM Frame Nullndash Disassociation Frame Reason codendash Association Request Frame Capability information Listen

Interval SSID and Supported Ratesndash Association Response Frame Capability information Status

code Association ID (AID) and the supported ratesndash Reassociation Request Frame Capability information Listen

Interval Current AP address SSID and Supported Ratesndash Reassociation Response Frame Capability information status

code Association ID (AID) and supported ratesndash Deauthentication Reason code


Management Frames (Frame Body)

ndash Probe Request Frame SSID and The supported ratesndash Probe Response Frame Time stamp beacon interval

capability information supported rates and parameter sets

raquo Omit ldquoTIMrdquo fieldraquo In 80211g new ldquoERP InformationERP Information ElementElementrdquo and

ldquoExtended Supported RatesExtended Supported Rates ElementElementrdquoare added ndash Authentication Frame Authentication algorithm

number (0Open system 1 Shared Key) Authentication transaction sequence number Status code (if reserved set to 0) and Challenge text

Authentication algorithm

Authentication Transaction

sequence numberStatus code Challenge text

Open System 1 Reserved Not present Open System 2 Status Not present Shared Key 1 Reserved Not present Shared Key 2 Status Present Shared Key 3 Reserved Present Shared Key 4 Status Not present


Capability Information field 1

ESS IBSS CFPollable

CF-PollRequest

Privacy

2 octetsB0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B13 B15

ShortPreamble PBCCPBCC Channel

AgilityShortShort

Slot timeSlot time hellip DSSSDSSS--OFDMOFDM

bull APs set the ESS subfiled to 1 and IBSS subfield to 0 within transmitted Beacon or Probe Responsemanagement frame

bull STAs within an IBSS set the ESS subfield to 0 and IBSS subfield to 1 in transmitted Beacon or Probe Response management frame

bull Bit 10 is used to indicate 9us9us slot time is used (IEEE 80211g)

bull Bit 13 is used to indicate the new option of DSSS-OFDM (IEEE 80211g)

80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g

bull STAs set the CF-Pollable and CF-Poll Request subfields in Association RequestAssociation Request and ReassociationReassociationRequestRequest management frames according to

CF-Pollable CF-Pollrequest Meaning

0 0 STA is not CF-Pollable

0 1 STA is CF-Pollable not requesting to be placed on the CF-Polling list

1 0 STA is CF-Pollable requesting to be placed on the CF-Polling list

1 1 STA is CF-Pollable requesting never to be Polled



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g

bullbull APsAPs set the CF-Pollable and CF-Poll Request subfields in BeaconBeacon Probe ResponseProbe Response and Association ResponseAssociation Response ReassociationReassociation ResponseResponsemanagement frames according to

CF-Pollable CF-Poll request Meaning

0 0 No point coordinator at AP

0 1 Point coordinator at AP for delivery only

1 0 Point coordinator at AP for delivery and polling

1 1 Reserved



ESS IBSS Privacy


ShortPreamble PBCCPBCC ShortShort


CFPollable

CF-PollRequest

ChannelAgility

80111gbull Optional frequency hoppingfrequency hopping for solve the shortcoming of

static channel assignment in DSSS ndash Example Tone jammer

bull Goal without added costbull Interoperability with 80211 FHSS 12Mbps

ndash Use same frequency hopping patterns

bull (Ref Page 121)


Channel Agility (optional)bull Two Sets for frequency hopping patterns (224us224us per hopper hop)

ndash North American

Set Number of Channels HRDSSS Channel Number 1 3 1611

2 6 1357911

NonNon--overlapping Channels Selection (overlapping Channels Selection (25MHz25MHz gap)gap)

HalfHalf--overlapping Channels Selection (overlapping Channels Selection (10MHz10MHz gap)gap)


Channel Agility (optional)bull Two Sets for frequency hopping patterns

ndash Europe (except Spain and France)


2 7 135791113




Information Element

LengthLength InformationInformation

octets

1 1 length

Element IDElement ID

Information Element Element ID

SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5

IBSS Parameter Set 6

Country 7

Legacy Indication (11g) 8

Reserved 9-15

Challenge Text 16

Reserved for challenge text extension 17-31

Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID

Length Supported Rates

octets 1 1 1-8

Element IDSupported Rate

Length

octets 1 1 2 1 1 1

Element ID Dwell time Hop Set Hop IndexHop PatternFH Parameter Set

DS Parameter Set Length

octets 1 1 1

Element ID currentchannel

Length

octets 1 1 1 1 2 2

Element ID CF Count CFP Maxduration CFP DurRemainingCF PeriodCF Parameter Set

Length

octets 1 1 1 1 1 1-251

Element ID DTIM Count

BitmapControl Partial Virtual Map

DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication

bullbull indicates the identity of an ESS or IBSSindicates the identity of an ESS or IBSSbullbull a a lsquolsquo00rsquorsquo length information field indicates the broadcast length information field indicates the broadcast SSID SSID


Supported Rate Elements

Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates

Extended Supported rates

bullbull The number of supported rates is The number of supported rates is 14 14 (abg)(abg)bullbull EEach ach supported ratesupported rate belonging to the belonging to the BSSBasicRateSetBSSBasicRateSet is encoded as an is encoded as an

octet with the octet with the msbmsb (bit 7) set to 1(bit 7) set to 1ndashndash eg a 1 eg a 1 MbitsMbits rate is encoded as X82rate is encoded as X82lsquolsquo (in 500kbps)(in 500kbps)

bullbull Rates Rates not belongingnot belonging to the to the BSSBasicRateSetBSSBasicRateSet are encoded with the are encoded with the msbmsbset to 0set to 0

ndashndash eg a 2 eg a 2 MbitsMbits rate is encoded as X04rate is encoded as X04


ERP Information Elements

Length=1

octets 1 1

Element IDNonERP Indication b0 b1

1

r r r r r r

Bit b0 NonERP_Present

0 No NonERP stations are within the BSS

1 There are NonERP stations within the BSS

Bit b1 Use_Protection

0 STAs with an ERP should not use protection mechanisms for MPDUs transmitted at one of the ERP-OFDM rates

1 STAs with an ERP shall use protection mechanisms for MPDUstransmitted at one of the ERP-OFDM rates

bullbull transmitted from AP in BSS or STA in IBSStransmitted from AP in BSS or STA in IBSSbullbull defined in defined in IEEE 80211g IEEE 80211g bull Protection mechanism

Use CTS frame to update the NAV of all receiving STAs prior to the transmission of a frame that may or may not be understood by receivers The updated NAV period shall be longer than or equal to the total time required to send the data and any required response frames


MAC Architecture

Required for Contention Free

Services

PointCoordination

Function(PCF)

Used for Contention Services and basis

for PCF

MACextension

DistributedCoordination Function

(DCF)

PHYPHY


MAC Architecture

bull Distributed Coordination Function (DCF)ndash The fundamental access method for the 80211 MAC known as

Carrier Sense Multiple Access with Collision Avoidance (CSMACA)

ndash Shall be implemented in all stations and APsndash Used within both ad hoc and infrastructure configurations

bull Point Coordination Function (PCF)ndash An alternative access methodndash Shall be implemented on top of the DCFndash A point coordinator (polling master) is used to determine

which station currently has the right to transmitndash Shall be built up from the DCF through the use of an access

priority mechanismndash Different accesses of traffic can be defined through the use of

different values of IFSndashndash Shall use a Point IFS (PIFS) lt Distributed IFS (DIFS)Shall use a Point IFS (PIFS) lt Distributed IFS (DIFS)


MAC Architecturendash Point coordinated traffic shall have higher priority to

access the medium which may be used to provide a contention-free access method

ndash The priority access of the PIFS allows the point coordinator to seize control of the medium away from the other stations

bull Coexistence of DCF and PCFndash Both the DCF and PCF shall coexist without

interferencendash They are integrated in a superframe in which a

contention-free burst occurs at the beginning followed by a contention period

Contention-free frames

Super frame

Contention frames


Distributed Coordination Function

bull Allows for automatic medium sharing between similar and dissimilar PHYs through the use of CSMACA and a random backoff time following a busy medium condition

bull All directed traffic uses immediate positive ack (ACK frame) where retransmission is scheduled by the sender if no ACK is received

bull Carrier Sense shall be performed both through physical and virtual mechanisms

bull The virtual Carrier Sense mechanism is achieved by distributing medium busy reservation information through an exchange of special small RTS and CTS frames (contain a duration field) prior to the actual data frame Unicast only not used in multicastbroadcast

bull The use of RTSCTS is under control of RTS_Threshold (payload length under which without any RTSCTS prefix)

bull All stations are required to be able to receive any frame transmitted on a given set of rates and must be able to transmit at (at least) one of these rates This assures that the Virtual Carrier Sense mechanism still works on multiple rates environments



bull Physical Carrier Sense Mechanismndash A physical carrier sense mechanism shall be provided by the

PHYbull Virtual Carrier Sense Mechanism

ndash Provided by the MAC named Net Allocation Vector (NAV) which maintains a prediction of future traffic based on durationinformation announced in RTSCTS frames

bull MAC-Level Acknowledgments (Positive Acknowledgment)ndash To allow detection of a lost or errored frame an ACK frame

shall be returned immediately following a successfully received frame The gap between the received frame and ACK frame shall be SIFS

ndash The frame types should be acknowledged with an ACK frameraquo Dataraquo Pollraquo Requestraquo Response

ndash The lack of an ACK frame means that an error has occurred


Distributed Coordination Function --Inter-Frame Space (IFS)

bull A station shall determine that the medium is free through the use of carrier sense function for the interval specified

bull Three different IFSs are defined to provide priority levelsbull Short-IFS (SIFS)

ndash Shall be used for an ACK frame a CTS frame by a station responding to any polling It may also be used by a PC for any types of frames during the CFP

ndash Any STA intending to send only these frame types shall be allowed to transmit after the SIFS time has elapsed following a busy medium

bull PCF-IFS (PIFS)ndash Shall be used only by the PCF to send any of the Contention Free Period

framesndash The PCF shall be allowed to transmit after it detects the medium free for

the period PIFS at the start of and during a CF-Burstbull DCF-IFS (DIFS)

ndash Shall be used by the DCF to transmit asynchronous MPDUs ndash A STA using the DCF is allowed to transmit after it detects the medium

free for the period DIFS as long as it is not in a backoff periodbull Extended IFS (EIFS)


Time Intervals SIFSPIFSDIFS


EIFS

bull The EIFS shall begin following indication by the PHY that the medium is idle after detection of the erroneous frame without regard to the virtual carrier-sense mechanism

bull The EIFS is defined to provide enough time for another STA to acknowledge what was to this STA an incorrect received frame before this STA commences transmission

bull EIFS = aSIFSTime + (8timesACKsize) + aPreambleLength + PLCPHeaderLength + DIFS where ACKsize is computed based on 1Mbps data rate


Distributed Coordination Function --Random Backoff Time

bull Before transmitting asynchronous MPDUs a STA shall use the carrier sense function to determine the medium state If busy the STA shall defer until after a DIFS gap is detected and then generate a random backoff period for an additional deferral time (resolve contention)

BackoffBackoff time = Random() Slot timetime = Random() Slot time where

Random() = Pseudorandom integer drawn from a uniform distribution over the interval [0 CW]

CW = An integer between CWmin and CWmaxSlot Time = Transmitter turn-on delay +

medium propagation delay +medium busy detect response time


Binary Exponentional Backoff Window

15~1023 for FHSS PHYSource IEEE Std 80211-19971482 FH PHY attributes Table 49

63~1023 for IR PHYSource IEEE Std 80211-1997164 PHY attributes Table 74

31~1023 for DSSS PHYSource IEEE Std 80211-19971532 DSSS PHY MIB Table 58

15~1023 for DSSS ERP PHY (gt20Mbs)31 ~1023 for DSSS ERP PHY (le20Mbs)Source IEEE Std 80211g-2001194385 PHY Page 12


Basic Access Protocol Featuresbull Use Distributed Coordination Function (DCF) for efficient medium

sharing without overlap restrictionsndash Use CSMA with Collision Avoidance derivativendash Based on Carrier Sense function in PHY called ClearClear ChannelChannel AssessmentAssessment

(CCA)bull Robust for interference (use positive acknowledge)

ndashndash CSMACA + ACK CSMACA + ACK for unicast frames with MAC level recoveryndash CSMACA for Broadcast frames

bull Parameterized use of RTS CTS to provide a VirtualVirtual CarrierCarrier SenseSensefunction to protect against Hidden Nodes

ndashndash DurationDuration information is distributed by both transmitter and receiver through separate RTS and CTS Control Frames

bull Includes fragmentation to cope with different PHY characteristicsbull Frame formats to support the access scheme

ndash For Infrastructure and Ad-Hoc Network supportndash and Wireless Distribution System


CSMACA ExplainedDIFS Contention Window

Slot time

Defer Access

Backoff-Window Next Frame

Select Slot and Decrement Backoff as long as medium is idle

SIFS

PIFSDIFS

Free access when mediumis free longer than DIFS

Busy Medium

bull Reduce collision probability where mostly neededndash Stations are waiting for medium to become freendash Select Random Backoff after a Defer resolving contention to

avoid collisionsbull Efficient Backoff algorithm stable at high loads

ndash Exponential Backoff window increases for retransmissionsndash Backoff timer elapses only when medium is idle

bull Implement different fixed priority levelsndash To allow immediate responses and PCF coexistence


CSMACA + ACK protocol

Next MPDU

Src

Dest

Other

Contention Window

Defer Access Backoff after Defer

DIFS

SIFS

DIFS

Data

Ack

bull Defer access based on Carrier Sensendash CCA from PHY and Virtual Carrier Sense state

bull Direct access when medium is sensed free longer then DIFS otherwise defer and backoff

bull Receiver of directed frames to return an ACK immediately when CRC correct

ndash When no ACK received then retransmit frame after a random backoff (up to maximum limit)


Throughput Efficiency

Throughput as function of Load

0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305

Load as function of channel speed

Thro

ughp

ut K

Byte

sec

576 Byte frames

60 Short 40 Long frames

64 Byte Frames

23 usec Slot time

bull Efficient and stable throughputndash Stable throughput at overload conditionsndash To support Bursty Traffic characteristics


Hidden Node Problem

bull Transmitters contending for the medium may not ldquoldquoHear Hear each othereach otherrdquordquo as shown below

bull Separate Control frame exchange (RTS CTS) between transmitter and receiver will Reserve the MediumReserve the Medium for

AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack

Stations do not hear each otherBut they hear the AP

subsequent data accessndash Duration is distributed around both Tx and Rx station


Hidden Node Provisions

RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS

bull Duration field in RTS and CTS frames distribute Medium Reservation information which is stored in a Net Allocation Net Allocation Vector (NAV)Vector (NAV)

bull Defer on either NAV or CCA indicating Medium BusyMedium Busybull Use of RTS CTS is optional but must be implementedbull Use is controlled by a RTS_ThresholdRTS_Threshold parameter per station

ndash To limit overhead for short frames (200 bytes)


RTSCTS Overhead Impact

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305

Load As factor of channel speed

Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

60 Short 40 Long Frames

Good mixed Throughput (long inbound frames) efficiency


Distributed Coordination Function --DCF Access Procedurebull Backoff Procedure

ndash A backoff time is selected first The Backoff Timer shall be frozen while the medium is sensed busy and shall decrement only when the medium is free (resume whenever free period gt DIFS)

ndash Transmission whenever the Backoff Timer reaches zerondash A STA that has just transmitted a frame and has another frame

ready to transmit (queued) shall perform the backoff procedure (fairness concern)

ndash Tends toward fair access on a FCFSFCFS basis

Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame

CWindow = Contention Window= Backoff= Remaining Backoff


Distributed Coordination Function --DCF Access Procedure

bull RTSCTS Recovery Procedure and Retransmit Limitsndash After an RTS is transmitted if the CTS fails in any manner

within a predetermined CTS_Timeout (T1) then a new RTS shall be generated (the CW shall be doubled)

ndash This procedure shall continue until the RTS_Re-Transmit_Counter reaches an RTS_Re-Transmit_Limit

ndash The same backoff mechanism shall be used when no ACK is received within a predetermined ACK_Window(T3) after a directed DATA frame has been transmitted

ndash This procedure shall be continue until the ACK_Re-Transmit_Counter reaches an ACK_Re-Transmit_Limit

ndash STAs shall maintain a short retry count (for MAC frame lt= RTS_Threshold) and a long retry count (for MAC frame gt RTS_Threshold) for each MSDU and MMPDU awaiting transmission These counts are incremented and reset independently of each other


Distributed Coordination Function --DCF Access Procedurebull Control of the Channel

ndash The IFS is used to provide an efficient MSDU delivery mechanism

ndash Once a station has contended for the channel it will continue to send fragments until either all fragments of a MSDU have been sent an ack is not received or the station can not send any additional fragments due to a dwell time boundary

ndash If the source station does not receive an ack frame it will attempt to retransmit the fragment at a later time (according tothe backoff algorithm) When the time arrives to retransmit the fragment the source station will contend for access in the contention window

DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window


Distributed Coordination Function --DCF Access Procedurebull RTSCTS Usage with Fragmentation

ndash The RTSCTS frames define the duration of the first frame and ack The durationduration field in the data and ack frames specifies the total duration of the next fragment and ack

ndash The last Fragment and ACK will have the duration set to zerondash Each Fragment and ACK acts as a virtual RTS and CTSndash In the case where an ack is not received by the source station

the NAV will be marked busy for next frame exchange This is the worst case situation

ndash If the ack is not sent by the destination stations that can only hear the destination will not update their NAV and be free to access the channel

ndash All stations that hear the source will be free to access the channel after the NAV from Fragment 1 has expired

ndash The source must wait until the NAV (Fragment 1) expires before attempting to contend for the channel after not receiving the ack


RTSCTS Usage with FragmentationDIFS

PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS

NAV(RTS) NAV(Fragment 1) NAV(Fragment 2)

NAV(CTS) NAV(ACK 1) NAV(ACK 2)

Other Backoff-Window

DIFS

PIFS

SIFSNAV(RTS) NAV(Fragment 1)

NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0

bull Burst of Fragments which are individually acknowledgedndash For Unicast frames only

bull Random backoff and retransmission of failing fragment when no ACK is returned

bull Duration information in data fragments and Ack frames causes NAV to be set for medium reservation mechanism


Fragmentation (22)bull The length of a fragment MPDU shall be an equal number of

octets for all fragments except the last which may be smaller

bull The length of a fragment MPDU shall always be an even number of octets except for the last fragment

bull The length of a fragment shall never be larger than aFragmentationThresholdaFragmentationThreshold unless WEP is invoked for the MPDU Because the MPDU shall be expanded by IV and ICV

bull The sequence number shall remain the same for all fragments of a MSDU or MMPDU

bull The fragments shall be sent in order of lowest fragment number to highest fragment number (start at zero and increased by one)

bull More Fragments bit is used to indicate the last (or only) fragment of the MSDU or MMPDU


Defragmentationbull The header of each fragment contains the following

information that is used by the destination STA to reassemble the MSDU or MMPDU

ndash Frame typendash Address of the senderndash Destination addressndash Sequence Control field

bull More Fragments indicator If WEP has been applied it shall be decrypted before the defragmentation

bull All STAs shall support the concurrent reception of fragments of at least three MSDUs or MMPDUs

bull All STAs shall maintain a Receive Timer for each MSDU or MMPDU If the a timer is not maintained all the fragments belong to the part of an MSDU or MMPDU are discarded

bull If the receive MSDU timer exceeds aMaxReceiveLifetimeaMaxReceiveLifetime then all received fragments of this MSDU or MMPDU are discarded


Distributed Coordination Function --DCF Access Procedurebullbull BroadcastBroadcast and multicastmulticast MPDU transfer procedure

ndash In the absence of a PCF when broadcast or multicast MPDUsare transferred from a STA with the ToDS bit clear only the basic access procedure shall be used Regardless of the length of the frame no RTSCTS exchange shall be used

ndash In addition no ACK shall be transmitted by any of the recipients of the frame

ndash Any broadcast or multicast MPDUs transferred from a STA with a ToDS bit set shall obey the rules for RTSCTS exchange because the MPDU is directed to the AP

ndash The broadcastmulticast message shall be distributed into the BSS so the STA originating the message will also receive the message Therefore all STAs must filter out broadcastmulticast messages that contain their address as the source address

ndash Broadcastmulticast MSDUs shall be propagated throughout the ESS

ndash This no MAC-level recovery on broadcast or multicast frames except for those frames sent with ToDS bit set


Optional Point Coordination Function (PCF)

(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF

Contention Free AsyncTime Bounded Async

bull Contention Free Service uses Point Coordination Function (PCF) on a DCF Foundation

ndash PCF can provide lower transfer delay variations to support Time Bounded ServicesTime Bounded Services

ndash Async Data Voice or mixed implementations possiblendash Point Coordinator resides in AP

bull Coexistence between Contention and optional Contention Free does not burden the implementation


Point Coordination Function(PCF)bull The PCF provides contention free servicesbull It is an option for a station to become the Point

Coordinator(PC) which generates the Superframe (SF)bull The PC shall reside in the AP bull The SF consists of a Contention Free (CF) period and a

Contention Periodbull The length of a SF is a manageable parameter and that of

the CF period may be variable on a per SF basis

免競爭訊框

超級訊框

需競爭訊框


PCF Burst

bull CF-Burst by Polling bit in CF-Down framebull Immediate response by Station on a CF_Pollbull Stations to maintain NAV to protect CF-traffic bull Responses can be variable lengthbull Reset NAV by last (CF_End) frame from APbull ACK Previous Frame bit in Header (piggyback)

D3

U1

D2

U2

D1

U4

D4

CFP repetition interval

Reset NAV

No Up

Contention Period

Contention Free Burst

Dx = AP-FrameUx = Station-Frame

CF_End

Min Contention Period

Busy Medium

PIFS

SIFS

NAV


Valid TypeSubtype combinations 12

Type valueb3 b2 Type description Subtype Value

b7 b6 b5 b4 Subtype description

00 Management 0000 Association request

00 Management 0001 Association response

00 Management 0010 Reassociation request

00 Management 0011 Reassociation response

00 Management 0100 Probe request

00 Management 0101 Probe response

00 Management 0110-0111 Reserved

00 Management 1000 Beacon

00 Management 1001 Announcement trafficindication message (ATIM)

00 Management 1010 Disassociation

00 Management 1011 Authentication

00 Management 1100 Deauthentication






01 Control 000-1001 Reserved01 Control 1010 Power Save (PS-Poll)01 Control 1011 RTS01 Control 1100 CTS01 Control 1101 ACK01 Control 1110 CF-End01 Control 1111 CF-End + CF-Ack10 Data 0000 Data10 Data 0001 Data + CF-Ack10 Data 0010 Data + CF-Poll10 Data 0011 Data + CF-Ack + CF-Poll10 Data 0100 Null function (no data)10 Data 0101 CF-Ack (no data)10 Data 0110 CF-Poll (no data)10 Data 0111 CF-Ack + CF-Poll (no data)10 Data 1000-1111 Reserved11 Reserved 0000-1111 Reserved


Point Coordination Function-- CFP structure and timing (12)bull The PC generates CFPs at the contention-free repetition rate

(CFPRate) which is defined as a number of DTIM intervals

Contention Free Period Contention Period


Variable Length

PCF

PCF Defers for Busy Medium

Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons

CFP Repetition Interval

CFP_Dur_remainingValue in beacon


Infrastructure Beacon Generation

Time Axis

Beacon Interval

X X X X

Actual time stamp in Beacon

Beacon Busy Medium

bull APs send Beacons in infrastructure networks bull Beacons scheduled at Beacon Interval bull Transmission may be delayed by CSMA deferral

ndash subsequent transmissions at expected Beacon Intervalndash not relative to last Beacon transmissionndash next Beacon sent at Target Beacon Transmission TimeTarget Beacon Transmission Time

bull Timestamp contains timer value at transmit time


Point Coordination Function-- CFP structure and timing (22)bull The length of the CFP is controlled by the PC with

maximum duration specified by the value of the CFPCFP--MaxDurationMaxDuration Parameter Set at the PC (broadcast by Beacon amp probe response)

bull Because the transmission of any beacon may be delayed due to a medium busy a CFP may be foreshortened by the amount of the delay

bull The CFPDurRemainingCFPDurRemaining value in the beacon shall let the CFP end time no later than TBTT plus the value of CF MaxDuration

CF MaxDuration

Nominal CF repetition interval

Beacon Frame

DCF Traffic B

Max RTS+CTS+MPDU+ACK

Contention-Free Period(foreshortened)

Contention Period

Target Beacon Transmission Time


Point Coordination Function-- PCF Access Procedure (12)

bull The PCF protocol is based on a polling schemepolling schemecontrolled by one special STA per BSS called the Point Coordinator

bull The PC gains control of the medium at the beginning of the CF and maintains control for the entire CF period by waiting a shorter time between transmissions

bull At the beginning of the CF the PCF shall sense the medium If it is free the PCF shall wait a PIFS time and transmit

ndash a Data frame with the CFCF--PollPoll Subtype bit set to the next station on the polling list or

ndash a CF-End frame if a null CF period is desired



bull The PCF uses the PCF priority level of the CSMACA protocol The shorter PIFS gap causes a burst traffic with inter-frame gaps that are shorter than the DIFS gap needed by stations using the Contention period

bull Each station except the station with the PCF shall preset its NAV to the maximum CF-Period length at the beginning of every SF The PCF shall transmit a CF-End or CF-End+Ack frame at the end of the CF-Period to reset the NAV of all stations in the BSS


Point Coordination Function-- PCF Transfer Procedurebull PCF Transfers When the PCF Station is Transmitter or

Recipientndash Stations shall respond to the CF-Poll immediately when a

frame is queued by sending this frame after an SIFS gap This results in a burst of Contention Free traffic (CF-Burst)

ndash For services that require MAC level ack the ack is preferably done through the CF-Ack bit in the Subtype field of the responding CF-Up frame

NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration

Dx = Down TrafficUx = Up Traffic

B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack


MAC Management Layerbull Synchronization

ndash finding and staying with a WLANndash Synchronization functions

raquo TSF Timer Beacon Generation

bull Power Managementndash sleeping without missing any messagesndash Power Management functions

raquo periodic sleep frame buffering Traffic Indication Map

bull Association and Reassociationndash Joining a networkndash Roaming moving from one AP to anotherndash Scanning

bull Management Information Base


Synchronization in 80211bull Timing Synchronization Function (TSFTSF)

bull Used for Power Managementndash Beacons sent at well known intervalsndash All station timers in BSS are synchronized

bull Used for Point Coordination Timingndash TSF Timer used to predict start of Contention Free burst

bull Used for Hop Timing for FH PHYndash TSF Timer used to time Dwell Intervalndash All Stations are synchronized so they hop at same time


Synchronization Approach

bull All stations maintain a local timerbull Timing Synchronization Function

ndash keeps timers from all stations in synchndash AP controls timing in infrastructure networksndash distributed function for Independent BSS

bull Timing conveyed by periodic BeaconBeacon transmissionsndash Beacons contain TimestampTimestamp for the entire BSSndash Timestamp from Beacons used to calibrate local clocksndash not required to hear every Beacon to stay in synchndash Beacons contain other management information

raquo also used for Power Management Roaming


Beacon Generation ()bull In Infrastructure

ndash AP defines the aBeaconPeriodaBeaconPeriod for transmitting beaconsndashndash aBeaconPeriodaBeaconPeriod is broadcast by beacon and probe responsendash may delayed by CSMACA

bull In IBSSndash all members participate in beacon generationndash The IBSS initiator defines the aBeaconPeriodaBeaconPeriodndash At each TBTT STA shall

raquo suspend the decrementing backoff timer for any non-beacon or non-ATIM transmission

raquo calculate a random delay from [0 2(CWminSlot_time)]raquo backoff the selected random delayraquo If a beacon is detected give up sending beacon and

decrementing backoff timerraquo otherwise transmit beacon


Power Management

bull Mobile devices are battery poweredndash Power Management is important for mobility

bull Current LAN protocols assume stations are always ready to receive

ndash Idle receive state dominates LAN adapter power consumption over time

bull How can we power off during idle periods yet maintain an active session

bull 80211 Power Management Protocolndash allows transceiver to be off as much as possiblendash is transparent to existing protocolsndash is flexible to support different applications

raquo possible to trade off throughput for battery life


Power Management Approach

bull Allow idle stations to go to sleepndash station power save mode stored in AP

bull APs buffer packets for sleeping stationsndash AP announces which stations have frames bufferedndash Traffic Indication Map (TIM) sent with every Beacon

bull Power Saving stations wake up periodicallyndash listen for Beacons

bull TSF assures AP and Power Save stations are synchronizedndash stations will wake up to hear a Beaconndash TSF timer keeps running when stations are sleepingndash synchronization allows extreme low power operation

bull Independent BSS also have Power Managementndash similar in concept distributed approach


Infrastructure Power Management

TIM

TIM-Interval

Time-axis

Busy Medium

AP activity

TIM TIM TIM DTIMDTIM

DTIM interval

BroadcastBroadcast

bull Broadcast frames are also buffered in APndash all broadcastsmulticasts are bufferedndash broadcastsmulticasts are only sent after DTIM

raquo DTIM Delivery Traffic Indication Messagendashndash DTIM interval is a multiple of TIM intervalDTIM interval is a multiple of TIM interval



TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast

bull Broadcast frames are also buffered in APndash all broadcastsmulticasts are bufferedndash broadcastsmulticasts are only sent after DTIMndash DTIM interval is a multiple of TIM interval

bull Stations wake up prior to an expected (D)TIM




bull Stations wake up prior to an expected (D)TIMbull If TIM indicates frame buffered

ndash station sends PSPS--PollPoll (with AIDAID) and stays awake to receive data

ndash else station sleeps again

TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast


IBSS Power Management

bullbull ATIMATIM Ad Hoc (Announced) Traffic Indication Messagebull If a STA is PS it shall enter the Awake state prior to each

TBTTbull If received a ATIM a STA shall remain in the Awake state

until the end of the next ATIM windowbull If a STA transmits a Beacon or an ATIM management frame

it shall remain in the Awake state until the end of the next ATIM window

bull Use RTSCTS to detect if a STA is in PS-modebull A STA shall transmit no frame types other than RTS CTS

and ACK Control frames and Beacon ATIM management frames in ATIM window

bull Transmission is begin following the ATIM window backoff DCF is used



Station C

Station B

Station A

Beacon

ATIMWindow

Beacon Interval Beacon IntervalTarget BeaconTime

ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State


IBSS Beacon Transmission


Scanningbull Scanning required for many functions

ndash finding and joining a networkndash finding a new AP while roamingndash initializing an Independent BSS (ad hoc) network

bull 80211 MAC uses a common mechanism for all PHYndash single or multi channelndash passive or active scanning

bullbull Passive ScanningPassive Scanningndash Find networks simply by listening for Beacons

bullbull Active ScanningActive Scanningndash On each channel

raquo Send a Probe Wait for a Probe Response

bull Beacon or Probe Response contains information necessary to join new network


Channel Scanningbull A STA shall operate in either a Passive Scanning mode or

an Active Scanning modebull For Passive scanning the STA shall scan for Beacon

frames containing the desired SSID (or broadcast SSID) The STA shall listen to each channel scanned for no longer than a maximum duration defined by the ChannelTimeparameter

bull For Active scanning the STA shall transmit Probe request containing the desired SSID (also can use broadcast SSID)

bull If a STArsquos scanning does not result in finding a BSS with the desired SSID or does not result in finding any BSS the STA may start an IBSS

bull A STA may start its own BSS without first scanning for a BSS to join


Active Scanning Example

Steps to Association

Access Point CAccess Point A

Station sends Probe RequestAPs send Probe Response

Station selects best AP

Station sends AssociationRequest to selected AP

AP sends AssociationResponse

Initial connection to an Access Point- Reassociation follows a similar process


Active ScanningbullFor each channel to be scanned

bullSend a Probe request with the broadcast destination SSID and broadcast BSSID bullStart a ProbeTimerbullIf the response has not been received before the Min_Probe_Response_timeMin_Probe_Response_time then clear NAV and scan the next channel else when ProbeTimer reaches Max_Probe_response_timeMax_Probe_response_time process all received probe responses and scan the next channel

PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK

Min_Probe_Response_Time Max_Probe_Response_Time

DIFS SIFS

DIFS

SIFS


Wireless LAN Infrastructure Network

Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7

bull Each Station is Associated with a particular APndash Stations 1 2 and 3 are associated with Access Point Andash Stations 4 and 5 are associated with Access Point Bndash Stations 6 and 7 are associated with Access Point C


Roaming

bull Mobile stations may movendash beyond the coverage area of their Access Pointndash but within range of another Access Point

bull Reassociation allows station to continue operation

Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach

bull Station decides that link to its current AP is poorbull Station uses scanning function to find another AP

ndash or uses information from previous scansbull Station sends Reassociation Request to new APbull If Reassociation Response is successful

ndash then station has roamed to the new APndash else station scans for another AP

bull If AP accepts Reassociation Requestndash AP indicates Reassociation to the Distribution Systemndash Distribution System information is updatedndash normally old AP is notified through Distribution System

CSMACA CSMACA -- 22

Outline

1 80211 Architecture and Overview2 Baseband Infrared (IR) Physical Layer

Specification3 Direct Sequence Spread Spectrum (DSSS)

Physical Layer Specification4 Orthogonal Frequency Division Multiplexing

(OFDM) Physical Layer Specification5 IEEE 80211g Extended Rate PHY (ERP)

Specification6 Frequency Hopping Spread Spectrum PHY

of the 80211 Wireless LAN Standard7 IEEE 80211 Wireless LAN MAC Standard

CSMACA CSMACA -- 33


CSMACA CSMACA -- 44



CSMACA CSMACA -- 55





CSMACA CSMACA -- 66

Medium Variations

CSMACA CSMACA -- 77




CSMACA CSMACA -- 88

Requirements








CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





CSMACA CSMACA -- 33


CSMACA CSMACA -- 44



CSMACA CSMACA -- 55





CSMACA CSMACA -- 66

Medium Variations

CSMACA CSMACA -- 77




CSMACA CSMACA -- 88

Requirements








CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





CSMACA CSMACA -- 44



CSMACA CSMACA -- 55





CSMACA CSMACA -- 66

Medium Variations

CSMACA CSMACA -- 77




CSMACA CSMACA -- 88

Requirements








CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





CSMACA CSMACA -- 55





CSMACA CSMACA -- 66

Medium Variations

CSMACA CSMACA -- 77




CSMACA CSMACA -- 88

Requirements








CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





CSMACA CSMACA -- 66

Medium Variations

CSMACA CSMACA -- 77




CSMACA CSMACA -- 88

Requirements








CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





CSMACA CSMACA -- 77




CSMACA CSMACA -- 88

Requirements








CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





CSMACA CSMACA -- 88

Requirements








CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





CSMACA CSMACA -- 99







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach







LLCLLC SAPSAP







MACMAC

PHYPHY






sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach










sense)







Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach











Management





StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach









StationAH3

Station

Station

AH1

AH2


Mobile Station STA





Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach









Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach







Station

Station Station

StationA1

A2 B1

B2BSS-A

BSS-B

AAP AP

B

Server








Wireless Bridging

APB A

AP

StationB2Station

B1

StationB3

Ethernet

StationA1

StationA3

Ethernet

A2Station

private lease line





Outdoor Application




Outdoor Application


Long Distances


25Miles25Miles



Distribution System





BSS vs ESS








Access Points






Access Points







near future)




ndash PHY and MAC












MAC Functionality






raquo AP polling







PHY Layer Services







Data Rate vs Range


Four PHYs


















Atheros Corp)





etc




ps 27MHz









What is DSSS



+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

+1-1

+1 -1 -1 -1 -1 -1+1 +1 +1 +1 +1

Power

Frequency

Power

Frequency

Power

Frequency

Power

Frequency



+11

-11

+1

-1

+11

-11

+1

-1

timetime

auto

corr

elat

ion

auto

corr

elat

ion





DSSS benefits




echo

echo

peak

echo

echo

peak

auto

corr

elat

ion

auto

corr

elat

ion

timetime











DSSS Channels


Channel Frequencies


Japan Frequency

(MKK)







370GHz as WLAN band











LLCLLC SAPSAP







MACMAC

PHYPHY





1Mbps DBPSK

192us

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






DBPSK Modulation

I

Q

I

Q




DQPSK Modulation

I

Q


00 001 π211 π10 3π2 (-π2)




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field




PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





Service Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Length Field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits








CRC field

PPDU

SYNC128 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits






CRC Implementation




1Mbps DBPSK

96us

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





2Mbps DQPSK



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits





to the PN code



PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits







Signal Field

PPDU

SYNC56 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits









































bull 64-state BCC


















Sinxx


0 dBr

-30 dBr

-50 dBr































IEEE 80211a PLCP



PLCP Header


PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU


6Mbps24 bits


PCLP Preamble

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU






PCLP Preamble

PLCP Preamble


PCLP RateLength

PPDU


Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits

PSDU




(for SIGNAL field)


PCLP Tail Subfield

24 bits

PPDU

RATE4 bits

Length12 bits

Parity1 bit

SERVICE16 bits

Tail6 bits

Pad Bits




Reserved1 bit


PSDU





PCLP Service

PPDU

RATE4 bits

Length12 bits

Parity1 bit

Tail6 bits

Pad Bits




Reserved1 bit

Tail6 bits




PCLP PSDU tail

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits

PSDUSERVICE16 bits




PCLP DATA encoding

PPDU

RATE4 bits

Length12 bits

Parity1 bit





Reserved1 bit

Tail6 bits







Modulation Tables




(first output)

(second output)


























Cell allocation


















IEEE 80211g PCLP


ERP-PBCC)














PPDU

SYNC12864 bits

SFD16 bits

SIGNAL8 bits

SERVICE8 bits

LENGTH16 bits

CRC16 bits










Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1Z-1 Z-1 Z-1 Z-1

Z-1 Z-1 Z-1Z-1

y0

y2

y1

b2j

b2j-1


PBCC-22 in 80211g




PBCC-33 in 80211g




11Msps11Msps

Shift

165Msps165Msps

Clock Switch


ReSyncTail Head

Clock Switch





Ones)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)

SFD(16 bits)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DBPSKModulation

1 Mbps


80211Long PLCP



SYNC(56 bits --

ScrambledOnes)

CRC(16 b its)

Length(16 bits)

Serv ice(8 bits)

Signal(8 bits)


SFD)



PPDUPPDU


OFDMSync(Long

Sync -- 8usecs)

OFDMSignalField

(4usecs)

OFDMData

Symbols

OFDMSignal

Extension(6 usecs)

DBPSKModulation

1 Mbps

DQPSKModulation

2Mbps


80211bShort PLCP



GuardInterval(16us)

Long TrainingSymbol

(8 useconds)

OFDM SignalField

(4 useconds)

PSDU





Signal(32us)

6 MbpsOFDM

Modulation(4us)

52 BPSKModulated

Subcarriers(8us)



rate







OFDMat 6 9 12 18 24 36 48 and 54 Mbps






OFDMat 6 9 12 18 24 36 48 and 54 Mbps






AlignmentEpoch

AlignmentEpoch

AlignmentEpoch

AlignmentEpoch


111vs

120




1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate

1 2 3 4 5 6 7 8 9 10 11Barker Chip

1 usec




time

time


11 MHz ChipRate





Multi-CarrierOFDM

time



~100nsecs









































rampup

rampdown









PLCP Preamble




PLCP Header




bull (1 15 2 25 3 35 4 45 Mbits)



PLCP_PDU Formatting


using Gray mapping






















IEEE 80211n


















(1085448)times2=243




























Mbps







36 48 and 54 Mbps




























ndash figure

STA 4STA 4

DS分散式系統

STA 2STA 2

STA 1STA 1


AP 擷取點

ESSESS

STA 3STA 3

AP 擷取點





Associated


Distributed System




















DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

BSS 3BSS 3

AP 擷取點

STA 7STA 7

AP 擷取點

STA 3STA 3

AP 擷取點

STA 5STA 5











STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點


Portals and Bridges





















STA 4STA 4

BSS 2BSS 2


DS分散式系統

STA 2STA 2

STA 1STA 1

BSS 1BSS 1

AP 擷取點

Portal 埠接器

STA 3STA 3

AP 擷取點

integration

distribution

















































































































WEPPRNG


IV


ICV

WEPPRNGIV

+

Secret Key

Ciphertext

ICV

Integrity Alg

Plaintext

ICV=ICV

Plaintext

TX

Integrity Alg

seed Key Sequence

seedKey Sequence

ICV

ICV


Encrypted


Init Vector(3)

Pad(6 bits)

Key ID(2 bits)

Payload




























Unassociated



Associated








Frame Types








Sender Receiver

RTS

CTS

Data

ACK

Optional


Frame Types






















STA 2STA 2

IBSSIBSS

STA 1STA 1

STA 3STA 3








Frame Formats

FrameControl

DurationID


Body

2 2 6 6 6 62 0-2312 4Octets

80211 MAC Header

ProtocolVersion

Type SubTypeToDS

RetryPwrMgt

MoreData

WEP Order rsrv

Frame Control Field

Bits 2 2 4 1 1 1 1 1 1 1 1

DSFrom More

Frag











Frame Fields









Frame Fields






DurationID Field






1 1 0 Reserved


1 1 2008-16383 Reserved







MSDU



HDR CRCFrame Body

















MAC HeaderBit 7654



MAC Header


Frame Control

Duration RA FCS

MAC Header


Frame Control

AID BSSID TA FCS

MAC Header





MAC Header


MAC Header














Data Frames

Frame Control


Sequence Number


MAC Header

Addr 3

02312











Frame Control

DurationAID


MAC Header

BSSID























ESS IBSS CFPollable

CF-PollRequest

Privacy



AgilityShortShort






80211g80211b 80211g



ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g









ESS IBSS Privacy



AgilityShortShort


CFPollable

CF-PollRequest

80111g






1 1 Reserved



ESS IBSS Privacy




CFPollable

CF-PollRequest

ChannelAgility





bull (Ref Page 121)





2 6 1357911







2 7 135791113




Information Element


octets

1 1 length



SSID 0

Supported rates 1

FH Parameter Set 2

DS Parameter Set 3

CF Parameter Set 4

TIM 5


Country 7


Reserved 9-15

Challenge Text 16


Reserved 32-255


Elements

Length SSID

octets 1 1 0-32

Element IDSSID


octets 1 1 1-8


Length

octets 1 1 2 1 1 1



octets 1 1 1


Length

octets 1 1 1 1 2 2


Length

octets 1 1 1 1 1 1-251



DTIM PeriodTIM


SSID Elements

Length

octets 1 1

Element ID SSID

0-32

SSID Indication




Length=1

octets 1 1

Element ID80211

(a b only)

1-8

Length=1

octets 1 1

Element ID

80211gExtended

supported rate

1-255

Supported rates








Length=1

octets 1 1


1

r r r r r r










MAC Architecture


Services

PointCoordination

Function(PCF)


for PCF

MACextension


(DCF)

PHYPHY


MAC Architecture
















Super frame

Contention frames
































EIFS




























Slot time

Defer Access



SIFS

PIFSDIFS


Busy Medium







Next MPDU

Src

Dest

Other

Contention Window


DIFS

SIFS

DIFS

Data

Ack








0

50

100

150

200

250

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thro

ughp

ut K

Byte

sec

576 Byte frames


64 Byte Frames

23 usec Slot time



Hidden Node Problem



AP

STA

STA

CTS-RangeRTS-Range

STA APRTS

CTS

Data

Ack





RTS

CTS

Data

Ack

NAV Next MPDU

Src

Dest

Other

CW


NAV

(RTS)

(CTS)

DIFS






RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS

RTSCTS Throughput

0

20

40

60

80

100

120

140

160

180

200

005 025 045 065 085 105 125 145 165 185 205 225 245 265 285 305


Thr

ough

put K

Byt

ese

c Plain CSMACAMixed

RTSCTS









Frame

A

B

C

D

E

DIFS

CWindow

CWindow

CWindow

CWindow

Backoff

Frame

Frame

Frame

Frame















DIFS

PIFSFragment Burst

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS SIFS

Src

Dst

Backoff-Window











PIFS

Fragment 1

Ack 1

SIFS SIFSFragment 2

Ack 2

SIFS SIFSFragment 3

Ack 3

SIFS

SIFS

Src

Dst

RTS

CTS

SIFS SIFS




DIFS

PIFS


NAV(CTS) NAV(ACK 1)

Backoff-WindowOther

Fragment 1

Ack 1

SIFS

Src

Dst

RTS

CTS

SIFS SIFS


Fragmentation (12)

Src

Dest ACK 0

SIFS

CTS

RTS

NAV (RTS)

NAV (CTS)

Other

PIFS

DIFS

Backoff-Window

ACK 1

Fragment 1

NAV (Fragment 0)

NAV (ACK 0)

SIFS

Fragment 0






























(CSMACA )

ContentionService

Service

PHY

MACPCF

Optional

DCF











免競爭訊框

超級訊框

需競爭訊框


PCF Burst


D3

U1

D2

U2

D1

U4

D4


Reset NAV

No Up

Contention Period



CF_End


Busy Medium

PIFS

SIFS

NAV




























Variable Length

PCF


Busy mediumPCF DCF

(Optional)

NAV

Reset NAV


Foreshortened CFP

B B

CFP CFP

DTIM DTIM DTIM

CPBeacons





Time Axis

Beacon Interval

X X X X


Beacon Busy Medium









CF MaxDuration


Beacon Frame

DCF Traffic B



Contention Period


















NAVNAV

SIFS

SIFS

Busy CF-D1

CF-U1

CF-D2

SIFS

CF-U2

CF-D3

SIFS

SIFS SIFS

CF-D4

CF-U4

CF-End

PIFS

SIFS

CFPCFP

Super Frame

CPCP

Reset NAV

CF_Max_Duration


B

PIFS

D1+Poll

U1+Ack

D2+Ack+Poll

U2+Ack

Ack+Poll

D4+Poll

U4+Ack

CF-End+Ack




























Power Management
















TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

BroadcastBroadcast





TIM

TIM-Interval

Time-axis

Busy Medium

AP activity


DTIM interval

PS Station

BroadcastBroadcast









TIM

TIM-Interval

Time-axis

Busy Medium

Tx operation

AP activity


DTIM interval

PS Station

Broadcast

PS-Poll

Broadcast












Station C

Station B

Station A

Beacon

ATIMWindow


ATIMWindow

ATIMWindow

Xmit ATIMRcv ACK

Xmit FrameRcv ACK

Rcv ATIMXmit ACK

Rcv FrameXmit ACK

Power-Saving State






























PROBE

P RESPONSE

ACK

P RESPONSE

Scanning STA

Responder 1

Responder 2

ACK


DIFS SIFS

DIFS

SIFS



Access Point A

Access Point B

Station 4

Access Point C

Station 1 Station 2

Station 3

Station 5Station 6

Station 7



Roaming



Access Point A

Access Point B

Station 4

Access Point C

Station 1

Station 2

Station 3

Station 5Station 6

Station 7

Reassocication


Roaming Approach





Documents

無線通訊協定 - 國立中興大學hwtseng/Wireless Networks/2CSMA_CA.pdfCSMA/CA - 34 Four PHYs • Frequency Hopping Spread Spectrum (FHSS)Frequency Hopping Spread Spectrum (FHSS)