Doc.: IEEE 802.11-04/1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 1 Enhanced...

September 2004

Hiroyuki Nakase, Tohoku Univ.Slide 1

doc.: IEEE 802.11-04/1032r1

Submission

Enhanced MAC proposal for high throughput.

Tohoku University

Hiroyuki Nakase and Hiroshi Oguma

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Outline

• Background• Frame aggregation for high throughput single link

using UDP – Simulation –• New MAC procedure

– EDCF with CW definition for AP

– Polling with static frame control

– Polling with MAC frame aggregation of different IP link

– Dual PHY method

• Development of PHY

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Introduction

• Throughput of MAC SAP was limited by connection procedure based on CSMA/CA.

• SIFS, DIFS and backoff for every packet

• 802.11 task group n is aiming to high throughput of more than 100Mbps.→ New PHY and MAC proposal is needed

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Proposal 1: Frame aggregation

• Frame format for aggregation– Aggregation of MAC frame to send same destinatio

n STA. – Aggregation Header is defined in addition to MAC

header.– Aggregation header has informations of number of

aggregation,

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Frame structure• Aggregation flag is defined in subtype field of MAC header.• Aggregation header is defined.

– Number of aggregation frames

• Subheader is added to each aggregated frame.– Length of frame

MAC Header

Aggregation Header

SubHeader

Frame 1

FCSData Body

SubHeader

Frame2 SubHeader

Frame n

Less than 9000 bytes

SIGNAL Frame BodyPreamble

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Throughput with frame aggregation

• Simulation results• Frame size of 1500x6 = 9,000 Byte by aggregation

• Point-to-point connection using UDP packet

• Wireless data rate is 324 Mbps

• Throughput of more than 180 Mbps was obtained

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

0

50

100

150

200

250

300

350

3000 4000 5000 6000 7000 8000 9000

Throughput 3Throughput 4Throughput 5 AP-STA 　 Point-to-Point

UDP packetACK : 54MbpsSIFS: 16usecDIFS: 32usec

Throughput using aggregation

Frame aggregation is effective to improve MAC throughput in the case of P-P connection.

324Mbps (54 x 6ch)

216Mbps (54 x 4ch)

162Mbps (54 x 3ch)

274.8Mbps (84.8%)

191.2Mbps (88.5%)

142.9Mbps (88.2%)

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

MAC throughput using Scenario

• Scenario 1 of usage model– Conventional DCF– Enhanced DCF with unfair contention window

setting– Proposal of employment of polling connection– Proposal of FDD mode using dual PHY

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

System throughput using EDCF• PHY data rate of 216Mbps and 324Mbps• CW setting of AP and STA is the same.• Frame aggregation was employed.

6Ch,　 4000Byte/CHThroughput: 32.4 Mbps

4Ch,　 4000Byte/CHThroughput: 28.4 Mbps

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

System throughput using EDCF

• Unfair CW setting for advantage of AP– CWmin_AP=15

50.8Mbps (Downlink : 49Mbps , Uplink: 1Mbps) at CWmin_STA=255

47.8Mbps (Downlink : 47Mbps , Uplink: 0.3Mbps) at CWmin_STA=255

6Ch(324Mbps),　 4000Byte/CH

4Ch(216Mbps),　 4000Byte/CH

Improvement of Throughput : 157%

Improvement of Throughput : 168%

Usage efficiency of PHY data rate is less than 60%

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Proposal of Enhanced PCF• Three Types of MAC procedure

1) Static Beacon Timing HCF① Individual polling

② MAC frame aggregation for multicast polling

2) Advanced HCF with dual PHY

• ConceptImprovement of system throughput

AP acts full traffic control in BSS

Suppression of overhead in low data rate traffic

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Enhanced PCF with static beacon timing

• Beacon interval is fixed. (Ex. 10 msec) : Easy control with power saving

• Transmission available by only AP in guard duration• Duration of alternate EPCF and EDCF• Length of EPCF is defined by AP due to request• AP broadcast information for EPCF using Beacon pac

ket • All STAs are controlled by AP even if STA adhoc com

munication

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Example procedureGuard duration

Beacon

CF-end

PCF Data Poll-request

Poll-acceptDCF Data

EPCF duration EDCF durationSTA-STA communication is also controlled b

y AP

During EDCF duration, STAs are operated as standard DCF mode.

Polling request is transmitted on the rule of

DCF.

EPCF duration is started from Beacon signal

from AP.

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Definition of frame format (I)

• Polling request and accept– STA sends a request frame to AP during DCF when ST

A has an application with fixed data rate streaming.– EX: HDTV, SDTV, VoIP, etc.

– AP assigns on the polling list table for the STA, and send a acceptance frame to the SAT.

Polling List TableAP has a polling list table for management of PDF duration.Data rate, sequence number, STA’s address, etc.

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Numerical results of EPCF

• Scenario 1• 10msec Beacon interval is assumed.

– HDTV, SDTV, VoIP, MP3, VideoPhone is communicated under polling streaming.

– Internet file transfer is under DCF.

• Necessary duration for polling : 4.8 msec• Without re-transmission for packet error

• Estimated throughput more than 81Mbps.• MAC efficiency is more than 96%.

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Problem

• Waste duration of PHY preamble and SIGNAL field of 16+4usec in low data rate frame.– Ex: 0.096Mbps (VoIP)

• Preamble and SIGNAL: 20usec

• MAC Header + Data + FCS @ 216Mbps: 16usec• (36Byte + 120Byte + 4Byte)/(216Mbps)

• Solution :Reduce the number of PHY preamble– Merging downstream for low data rate!!

• MAC frame Aggregation for low data stream of < 1Mbps

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Enhanced PCF with MAC frame merging• Employment of MAC frame aggregation of AP-to-STAs frame during EPCF

• STA-to-AP frame is sending by reserved slot in Poll-accept packet

• Expansion of duration for EDCF due to suppression of EPCF overhead Guard duration

Beacon

CF-end

PCF Data Poll-request

Poll-acceptDCF Data

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Frame format

• Merge header has four fields of Frame Control, Duration, Source Address, BSSID and Sequence Control.

Preamble SIGNAL Merging MAC Header

MAC SubHeader 1

Body + FCS MAC SubHeader 2

Body + FCS

MAC SubHeader 3

Body + FCS FCS

Frame Control

2

Duration

2

Source Address

6

BSSID

6

MAC SubHeader has fields of Sequence Number, Duration and Destination Address

Duration

2

Destination Address

6

Sequence Control

1

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Control Field Definition• Frame Control Field

– First 1 Byte is the same as conventional MAC header.

– Number of aggregated MAC frames is represented.

• Sequence Control Field– Sequence number for identification

– MAC information for individual terminal

Protocol Version

2

Type

2

Subtype

4

Sequence Number

4

Retry

1

PwrMgt

1

Order

1

WEP

1

Number of Aggregation

4

Researved

4

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Throughput Estimation (Scenario 1)

• 10msec Beacon interval is assumed.– HDTV, SDTV, VoIP, MP3, VideoPhone is co

mmunicated under polling streaming.– Internet file transfer is under DCF.

• Necessary duration for polling : 4.4 msec• Without re-transmission for packet error

• Estimated throughput more than 82Mbps.

• MAC efficiency is more than 98%.

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Dual PHY communication• IFS for ACK, low rate AP-STA are wasted durati

on for 11n.– AP-STA and STA-AP connection are used the same fr

equency band : Time Division Duplex (TDD)

• In order to increase throughput, different band is used for STA-AP connection : Employment of Freqency Division Duplex (FDD) using 11a/b/g– Ack, low rate packet for STA-AP connection

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Dual PHY protocol stack

• Definition of MAC sub-layer for merging different PHY

PHY

11n

PHY

11b/g/n

MAC

11b/g/n

MAC

11n

MAC

STA-AP AP-STA

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Dual PHY communication• Employment of 11b/g/n PHY for low data rate traffic of less than 1 Mbps

• High data rate of 11n PHY for large streaming such as HDTV, Gaming, etc.

• AP-to-STA streaming without IFS to achieve higher throughput.

IFS is not needed for AP-STA

ACK is transmitted immediately from STA

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

PHY and MAC implementation

• We have a national project to implement 5GHz high throughput WLAN terminal.– Development with Mitsubishi Electric Co. and

NetCleus Systems Co.

• Band expansion based on 11a PHY format.– 6 channels expansion available– Xillinx VertexIIPro was used for MAC implem

entation.

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Block diagram of implemented modem

Gbit Ethernet

PHY LSIMAC

Wireless LAN

MAC

Modulation

Demodulation

TX RF/IF

RX RF/IF

DAC

ADC

RJ45

Implemented on Virtex2ProWith dual processor of PowerPC450

14bit 160Msps

12bit 160Msps

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Implementation of 5GHz modem

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Implementation of modem• MAC board : throughput of more than 100Mbps

September 2004


doc.: IEEE 802.11-04/1032r1

Submission

Conclusion

• New MAC Proposal with effective polling procedure is indispensable for high system throughput using 11n.

• Our proposals are based on1 Enhanced DCF with unfair contention window setting

2 Proposal of employment of polling connection

3 Proposal of FDD mode using dual PHY

Every proposal has improvement of MAC-SAP throughput superior to conventional MAC procedure.

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Doc.: IEEE 802.11-04/1032r1 Submission September 2004 Hiroyuki Nakase, Tohoku Univ.Slide 1 Enhanced...

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