Doc.: IEEE 802.15-02/138r0 Submission March 2002 Steve Shellhammer, Symbol TechnologiesSlide 1 Steve Shellhammer, Nada Golmie, Robert Van Dyck, Jie Liang,

March 2002

Steve Shellhammer, Symbol TechnologiesSlide 1

doc.: IEEE 802.15-02/138r0

Submission

Steve Shellhammer, Nada Golmie, Robert Van Dyck, Jie Liang, Y.C. Maa,

Anuj Batra, Jim Lansford, and Arun Arunachalam

Tutorial on 802.15.2 Draft

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Outline of 802.15.2 Draft• Interference Modeling

– Physical Layer Modeling– MAC Layer Modeling

• Collaborative Coexistence Mechanisms– AWMA– PTA

• Noncollaborative Coexistence Mechanisms – BT Packet Scheduling and Selection– BT Adaptive Frequency Hopping

March 2002


doc.: IEEE 802.15-02/138r0

Submission

System Simulation Modeling

March 2002


doc.: IEEE 802.15-02/138r0

Submission

• Additive White Gaussian Noise

• Path loss model

• Received power and SIR depend on topology and device parameters:

mdd

mddLp

8)8/log(335.58

85.0)log(202.40

PTR LPP IR PPSIR

Channel Modeling

March 2002


doc.: IEEE 802.15-02/138r0

Submission

• DSP based implementation of transceivers• Design using typical parameters (goal is to

remain non-implementation specific)• Bluetooth

– Non-coherent Limiter Discriminator receiver

• IEEE 802.11– Direct Sequence Spread Spectrum (1 & 2 Mbits/s)– Complementary Code Keying (5.5 & 11 Mbits/s)– Frequency Hopping (1 Mbits/s)

Physical Layer Modeling

March 2002


doc.: IEEE 802.15-02/138r0

Submission

• MAC behavioral implementation for Bluetooth and IEEE 802.11 (connection mode)

• Frequency hopping • Error detection and correction

– Different error correction schemes applied to packet segments (Bluetooth)

– FCS (802.11)

• Performance statistics collection– Access delay, packet loss, residual error, throughput

MAC Layer Modeling

March 2002


doc.: IEEE 802.15-02/138r0

Submission

BluetoothData PacketsDM5, 2871 bitsOffered Load 50%SCO Packets HV1, 366 bitsTx Power 1 mW

802.11Data Rate 11 Mbits/s, 1 Mbits/sModes Direct Sequence, FHPacket Size 12000 bitsOffered Load 50%Tx Power 25 mW

Bluetooth Slave

Bluetooth Master

802.11 AP

802.11 Mobile d=1m

582.5Voice

4412Voice

9012Voice

132.3Data1 Mbit/s FH

1 Mbit/s DS

11 Mbit/s DS1518Data

3814Data

802.11BTBT Traffic802.11 Type

Percentage of Packet Loss

Typical Modeling Results

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Collaborative Coexistence Mechanisms

802.11MAC

802.15.1Link Manager

802.11 PLCP+ PHY

802.15.1Baseband

PTAControl

Status Status

Tx Confirm(status)

Tx Confirm(status)

Tx RequestTx Request

CollaborativeCoexistenceMechanism

802.11 Device 802.15.1 Device

AWMAMedium FreeGeneration

Medum Free

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Alternating Wireless Medium Access (AWMA)

• Collaborate Coexistence Mechanism for Collocated IEEE 802.11b and Bluetooth– Both in the same laptop or handheld

• Coordinated MAC Layer• Subdivide WLAN Beacon Interval

– WLAN Interval– WPAN Interval

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Alternating Wireless Medium Access

• Synchronization of all units connected to the same WLAN Access Point

• Eliminates WLAN/WPAN interference due to no temporal overlap

• Good for high-density of WLAN/WPAN units.

• Does not support Bluetooth SCO link

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Packet Traffic Arbitration

This proposal does not address PHY or antenna issues

BluetoothBluetoothBasebandBaseband(up to HCI)(up to HCI)

802.11b MAC802.11b MAC

Bluetooth Bluetooth RadioRadio 802.11b PHY802.11b PHY

PTAPTA

BT TrafficBT Traffic 802.11 traffic802.11 trafficPTA-802.11 PTA-802.11

InterfaceInterface

PTA-PTA-Bluetooth Bluetooth InterfaceInterface

March 2002


doc.: IEEE 802.15-02/138r0

Submission


• Collaborative techniques define rules in advance for traffic management by direct communication between systems…no learning• Traffic light (TDMA) totally prevents

collisions• Yield, 4-way stop, etc. are also valid

rules• Maximizes traffic while avoiding

collisions

March 2002


doc.: IEEE 802.15-02/138r0

Submission


• Dynamic algorithm schedules traffic• Knowledge of time-frequency collisions is key

– Simultaneous transmission or reception allowed– Tx simultaneous with Rx allowed if not in-band

(requires good LNA and REALLY good channel filters)

– Critical for SCO operation-WLAN can work around in-band collisions

• This figure does not show polls/nulls, which often dominates Bluetooth traffic

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Packet Traffic Arbitration• Assumed MAC structure

– At most one message pending for BT– At most two messages pending for WLAN

PTAEngine

FrequencyCollision

Map

WLAN Stack

WLAN FIFO2

WLAN FIFO1

WLANModem

WLANModem

DecisionLogic

DecisionLogic

Bluetooth Stack

Backoff &CCA

TxEvent

Enable

Enable

SwitchMatrix

Bluetooth FIFO

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Adaptive Packet Selection• Bluetooth provides a wide range of packet

types to select from: payload length, FEC options

• DM1, DM3, DM5, DH1, DH3, DH5,AUX1

– Guidelines:– range limited situation: use DM packet for its FEC– interference

• Adaptive packet payload length selection: – Adaptive fragmentation

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Adaptive Packet Scheduling

• Interference Estimation • Maintain a Frequency Usage Table at

master and slave nodes.• Slave updates master’s Frequency Usage

Table every update interval.

• Master Scheduling Policy• Use “good” frequencies for master / slave

transmission (upstream and downstream)

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Channel Classification

• Draft provides an example algorithm for determining the quality of the channels. Actual implementation is left to the vendor.

• Metrics that could be used by the vendors include:– RSSI, PER, Carrier Sensing, and Packet ACK.

• Measurements can be made using:– Batch (block) techniques.– Online or offline techniques.

March 2002


doc.: IEEE 802.15-02/138r0

Submission


Advantages:• It does not require changes to the Bluetooth

specifications.• It conforms to FCC rules. • It saves power since no transmission is

wasted in bad channels• It is neighbor-friendly and mitigates

interference on other systems.

March 2002


doc.: IEEE 802.15-02/138r0

Submission


FrequencyOffset

Frequency Status

01 23...

787776

Master Slave

Update Messagefrom Slave

Frequency Hopping Pattern

f1 f2

Slave Rx Master Rx

f3 f4

Slave Rx Master Rx

Delay PacketTransmission

Packet to Transmit

good good

bad bad

bad good

bad bad

good bad

good

good bad

bad

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Simulation Results

• Bluetooth Performance

0.25

0.2

0.15

0.1

0.05

0

BT Slave Pr [ Packet Loss]

0 1 2 3 4 5

Distance between Bluetooth Slave and 802.11 Mobile (meters)

No Scheduling, DM1

Scheduling, DM1, DM3, DM5

No Scheduling, DM3

No Scheduling, DM5

0 1 2 3 4 5


BT Slave Mean Access Delay (seconds)0.008

0.006

0.004

0.002

0

Scheduling, DM1

No Scheduling, DM1

Scheduling, DM5

No Scheduling, DM5

Scheduling, DM3No Scheduling, DM3

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Simulation Results• IEEE 802.11 Performance

0.05

0.04

0.03

0.02

0.01

0

802.11 Mobile Pr [ Packet Loss]

0 1 2 3 4 5


No Scheduling, DM1

Scheduling, DM1, DM3, DM5

No Scheduling, DM3

No Scheduling, DM5

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Adaptive Frequency Hopping• Adaptive frequency hopping (AFH) is a non-

collaborative mechanism that enables the coexistence of IEEE 802.15.1 devices with frequency static devices in the 2.4 GHz ISM band such as IEEE 802.11b.

• This mechanism dynamically changes the frequency hopping sequence in order to avoid or mitigate the interference seen by both 802.11b and the 802.15.1 device.

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Adaptive Frequency Hopping• There are 4 main elements of Adaptive Hopping:

– AFH Capability Discovery– Channel Classification– Channel Quality Information Exchange– Adaptive Hopping Mechanism

• Channel classification is a mechanism for determining the quality of a channel. The channel is classified as either good or bad based on predefined metrics.– Used by both AFH and packet scheduling.

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Adaptive Frequency Hopping

min

min

when }1,0{

when 1

NN

NN

G

G

UAP/LAP

PartitionSequenceGenerator

Traffic type(ACL or SCO)

LegacyHop

KernelCLK

FrequencyRe-mapper

p(k)

fhopfadp

Channel Conditions(SG, SBK, NG, NBK)

CLKAM_ADDR

March 2002


doc.: IEEE 802.15-02/138r0

Submission


• The legacy hop kernel generates the hopping sequence defined in the IEEE 802.15.1 standard. This hopping sequence is referred to as the original hopping sequence.

March 2002


doc.: IEEE 802.15-02/138r0

Submission


• Partition sequence generator imposes a structure on the original hopping sequence without changing pseudo-random properties.– For SCO+ACL, good slots are first assigned to

voice slots.– For ACL only, good and bad channels are grouped

together. Reduces the effects of transitions from good-to-bad channels (retransmissions) and bad-to-good channels (idle slots). Maximizes throughput.

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Adaptive Frequency Hopping• The frequency re-mapping function

uses the partition sequence to generate the new hopping sequence. If necessary, this block uniformly re-maps the original hopping channel onto the set defined by the partition sequence.– When p(k) = 1, the re-mapping function

only hops over the good channels (reduced frequency hopping).

March 2002


doc.: IEEE 802.15-02/138r0

Submission

LMP Commands

• The following LMP commands are needed for the AFH mechanism:

Check to ensure that device is using the correct hopping sequence

LMP_AFH_check_req/res

Forces device back to regular hopping setLMP_regular_hopping_req

Forces device to start adaptive hoppingLMP_AFH_start

Request and Return of Slave’s Classification

LMP_channel_metrics_req/res

Identifies AFH-capable devicesLMP_features_req/res

DescriptionLMP Command

March 2002


doc.: IEEE 802.15-02/138r0

Submission

Summary

• Draft D05 will be available on the server by Thursday AM.

• Motion to go to letter ballot on 802.11 and 802.15 on Friday AM.

• 40 day letter ballot to start no later than March 22, 2002.

Documents

Doc.: IEEE 802.15-02/138r0 Submission March 2002 Steve Shellhammer, Symbol TechnologiesSlide 1 Steve Shellhammer, Nada Golmie, Robert Van Dyck, Jie Liang,