Wireless WANCase Study: WiMAX/802.16

W.wan.6

Dr.M.Y.Wu@CSEShanghai Jiaotong University

Shanghai, China

Dr.W.Shu@ECEUniversity of New Mexico

Albuquerque, NM, USA

@ by Dr.Shu@UNM & Dr.Wu@SJTU

W.wan.6-2

WiMAX/802.16

IEEE 802 suiteWiMAX/802.16

PHYMAC802.16ePast & future

802.16 vs 802.11WiMAX vs 3GEnd

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W.wan.6-3

IEEE 802 suite

IEEE 802 --- PAN/LAN/MAN StandardsWired

802.3 (Ethernet)Wireless

802.11: Wireless LANWiFi

802.15: Wireless PANBluetooth

802.16: Wireless MANWiMAX

802.20: Vehicular Mobility ?MobilFi

Standard downloads (free 6 months after publication)http://standards.ieee.org/getieee802

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W.wan.6-4

IEEE802 suite

IEEE 802 --- PAN/LAN/MAN Standards

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W.wan.6-5

WiMAX & 802.16

WiMAX = WLL + IEEE StandardizationUse point-to-multipoint architecture with stationary rooftop or tower-mounted antennasWorldwide interoperability for Microwave Access WiMAXStandard: IEEE 802.16Frequency spectrum

around 30 GHz, LMDS, LOS, licensedaround 3 GHz, MMDS, NLOS, licensed

Last-mile technology: metropolitan area in scaleCan serve as backhaul for wireless LANs (802.11)

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W.wan.6-6

WiMAX & 802.16

802.1610 – 66 GHz

LOSSep 2000

802.16eSome Mobility

Feb 2006 802.16a2 – 11 GHz

NLOSJan 2003

WiMAX = interoperable subset of this (< 6 GHz)

802.16dSimilar to .16a

Jul 2004

802.16 20042 – 66 GHzLOS/NLOS

Jul 2004

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W.wan.6-7

1.25 to 20 MHz1.25 to 20 MHz20, 25 and 28 MHz Channel Bandwidth

2-5 km

Portable

Scalable OFDMA128 to 2048 FFT

Up to 15 Mbps in 5MHz

NLOS

< 6 GHz

February 2006

802.16e

FixedFixedMobility

NLOSLOSChannel Conditions

< 11 GHz10 - 66 GHzSpectrum

June 2004 (16d)December 2001Completed

5-8 km, max 50km based on tower, antenna, tran power

2-5 km Cell size

OFDM 256 FFT QPSK, 16QAM, 64QAM

QPSK, 16QAM and 64QAM

Modulation

Up to 75 Mbps in 20MHz

32 – 134 Mbps in 28MHz

Bit Rate

802.16a/d802.16WiMAX

WiMAX & 802.16

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W.wan.6-8

WiMAX & 802.16

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W.wan.6-9

WiMAX & 802.16 PHY

Air Interface (PHYs with common MAC)802.16: 10-66 GHz, 2002802.16a: 2-11 GHz, 2003

SpecificationIncluding the MAC layer and PHY layer, of fixed point-to-multipoint broadband wireless access systemsproviding multiple services.

The MAC layer is capable of supporting multiple PHY layer specifications optimized for the frequency bands of the application. The standard includes a particular PHY layer specification broadly applicable to systems operating between 10 and 66 GHz.

@ by Dr.Shu@UNM & Dr.Wu@SJTU

W.wan.6-10

WiMAX & 802.16 PHY

Multipath signal (NLOS problem, not in LOS)The composition of a primary signal plus duplicate or echoed images caused by reflections of signals off objects between the transmitter and the receiverThe echoed signal is delayed in time and reduced in power, and it causes ISI (inter-symbol interface)

Solution? (to overcoming multipath signals)Adaptive modulationFEC (Forward Error Correction)Spread Spectrum, OFDMAdvanced antenna systemPower control

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W.wan.6-11

WiMAX & 802.16 PHY

Adaptive modulationThe further the subscriber is from the base station, the greater the likelihood of a lower form of modulation and a higher amount of coding and thus a lower bit-rate

22dB64 QAM16dB16 QAM9dBQPSK6dBBPSKSNRModulation

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W.wan.6-12

WiMAX raw bandwidth (Mbps), in theory

WiMAX & 802.16 PHY

73.1965.0548.7932.5324.4016.2620.0 MHz

52.3646.5534.9123.2717.4511.6414.0 MHz

26.1823.2717.4511.648.735.827.0 MHz

13.0911.648.735.824.362.913.5 MHz

6.555.824.362.912.181.451.75 MHz

64 QAM 3/4

64 QAM 2/3

16 QAM 3/4

16 QAM 1/2

QPSK 3/4

QPSK 1/2

Modulation code rate

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W.wan.6-13

WiMAX & 802.16 PHY

WiMAX coverage (Km), in theory

<1 km<2 kmN/AUrban

<2 km<4 kmN/ASuburban

< 4km<8 km<20 km, NLOS*Rural

Indoor/portable antenna

Window/fixed antenna

Rooftop antennaType of area

* <50 Km is the theoretical maximum for LOS. Assumption is a NLOS base station and a rooftop antenna for better reception and maximum uplink power

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W.wan.6-14

WiMAX & 802.16 PHY

OFDM = Orthogonal FDMA technique to increase transmission speed by multiplexing Uses one wide frequency channel by breaking it up into several sub-channelsORTHOGONALITY overlapping but distinguishable

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W.wan.6-15

WiMAX & 802.16 MAC

PMP (Point-to-Multipoint), Connection orientedSupport multiple 802.16 PHYsDynamic TDMA-based MAC with on-demand bandwidth allocation. (low cost: SS doesn’t Tx/Rx simultaneously)

FDDDownlink & uplink on separate RF channelsUnframed FDD for full-duplex SSFramed FDD, downlink in burstsStatic asymmetry

TDDDownlink & uplink time share the same RF channelDynamic asymmetry

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W.wan.6-16

WiMAX/802.16 MAC

UplinkUses a DAMA-TDMA techniqueError correction uses Reed-Solomon codeModulation scheme based on QPSK

DownlinkContinuous downstream mode for A/V

Simple TDM scheme is used for channel accessDuplexing technique is frequency division duplex (FDD)

Burst downstream mode for IP trafficDAMA-TDMA scheme is used for channel accessDuplexing techniques are FDD with adaptive modulation, frequency shift division duplexing (FSDD), time division duplexing(TDD)

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W.wan.6-17

WiMAX & 802.16

Technology considerationsLicensed vs unlicensedLOS vs NLOSHalf-duplex vs full-duplexP2P, PMP, MeshFixed, portable, mobileCost performance

throughput = channel bandwidth (Hz) X bits/HzLast-mile tech?

T1 replacementWiFi backhaul3G/4G?

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W.wan.6-18

WiMAX/802.16e

Fixed PortableIEEE 802.16-2004 standard is designed for fixed-access usageIt uses a mounted antenna at the subscriber’s site.Fixed model is an alternative to

cable modem, DSL,802.16e

Targets the mobile market by adding portability. Mobile clients with IEEE 802.16e adapters can connect directly to the WiMAX network.802.16e uses Orthogonal Frequency Division Multiple Access (OFDMA)

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W.wan.6-19

Mobility in 802.16e: PHY LayerSleep mode, paging enabled.Fast time alignment (ranging) mechanismFlexible FFT sizes depending on channel bandwidth to ensure OFDM symbol duration is compatible with mobility requirementsSoft handover, i.e., transmit/receive from multiple BSFast channel feedbackFast BSS handover involving maintenance of sync to multiple BS’while transmitting/receiving from anchor BSNew MIMO, STC modes

MIMO soft-handoff based macro-diversity transmissionSpace-time codes for 3 antenna configurations. Fixed version has 2 and 4 antenna modes.

WiMAX/802.16e

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W.wan.6-20

Mobility in 802.16e: MAC Layer Handover (HO) process defined in MAC including

cell reselectiontarget BS scanningnetwork re-entryHO decision and initiation and HO cancellation.

Newly defined:MAC messages for each of the handover functionsBroadcast paging messageNeighbor topology advertisement messagesOption of using mobile IP provided

Full QoS supported. All four GSM/WCDMA classes.

WiMAX/802.16e

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W.wan.6-21

WiMax past & future

Evolution of 802.16Originally was for bands above 10 GHZ

Corporate access, and back haul only, but no mass market802.16a revision was added for bands below 10 GHZ and NLOSThe current revision is 802.16 2004 which combines prior revisions into one802.16e will extend the standard to cover mobile applications

Estimate equipment availability and cost1st generation: Fixed outdoor antenna/radio, 2005,~$3502nd generation: Indoor directional antenna/radio, 2006,~$2503rd generation: Integrated system in laptops, 2007 ~$100

Incoming802.16g/i --- Network Management802.16j --- Multihop relay specification802.16k --- MAC layer bridging

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W.wan.6-22

WiMax past & future

Bandwidth vs mobility

802.11

802.16WiMAX

802.16e

802.203G

50Mbps

20Mbps

10Mbps

nomadicfixed

1Mbps

mobile

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W.wan.6-23

WiMAX/802.16 vs WiFi/802.11

2.4 GHzunlicensed

Spectrum2-11 GHzLicensed, unlicensed

ConnectionlessConnection typeConnection orientedNoFull duplexTDD/FDD

CSMA/CAMultiple accessTDMA

NoQoSOn demand: A/V,dataTens CPEScalabilityHundreds CPE

2.7bps/Hz peak< 54Mbps in 20MHz

Data rate5bps/Hz peak< 100Mbps in 20 MHz

Indoor short rangeCoverageOutdoor LOS & NLOS< 200mRange < 50 km (typical 5km)

WiFi/802.11b/gTechnologyWiMAX/802.16

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W.wan.6-24

WiMAX/802.16 vs WiFi/802.11

Tropos Networks: Integration of 802.16 & 820.11WiMAX as backhaul

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W.wan.6-25

WiMAX/802.16 vs WiFi/802.11

Tropos Networks: Integration of 802.16 & 820.11WiMAX as transport within the mesh

@ by Dr.Shu@UNM & Dr.Wu@SJTU

W.wan.6-26

WiMAX/802.16 vs WiFi/802.11

Tropos Networks: Integration of 802.16 & 820.11WiMAX as client connection

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W.wan.6-27

WiMAX/802.16 vs 3G

Mobile broadbandBroadbandWireless broadband

WiMAX potential 4G???Optimized for voiceServicesOptimized for data

NLOSChannelsLOS or NLOSRoaming / mobilitymobilityFixed to portablePhones & laptopsClientLaptop centric

3GTechnologyWiMAX/802.16

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W.wan.6-28

WiMAX in China

BWA/802.16 in ChinaBWA = Broadband Wireless Access广带无线接入标准