Doc.: IEEE 802.11-03/567r1 Submission July 2003 Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 1 Throughput Enhancement via Frame Aggregation – A Sequel

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 1

doc.: IEEE 802.11-03/567r1

Submission

Throughput Enhancement Throughput Enhancement via Frame Aggregation – A Sequelvia Frame Aggregation – A Sequel

Youngsoo Kim*+, Sunghyun Choi*,

Hyosun Hwang+, and Kyunghun Jang+

+Samsung Advance Institute of Technology (SAIT) and *Seoul National University (SNU)

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ContentsContents

• Introduction

• Frame aggregation

• New Results– Numerical throughput analysis with channel

error

– Performance measurement using TCP and UDP traffic

• Conclusion

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IntroductionIntroduction

• Objective– To achieve high throughput/efficient schemes to

improve the current 802.11 MAC/PHY

• Background– 802.11 MAC/PHY has fixed overheads irrespective of

packet size

– The small-size packet can cause more throughput degradation

– To reduce the overheads is the one of main concerns to enhance current 802.11 WLAN

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Throughput Performance AnalysisThroughput Performance Analysis

• Assumptions– There are a single transmitter and a single rec

eiver– The 802.11 DCF is used– All the datagrams have a fixed size– The transmitter has infinite number of datagra

ms– Channel error is not considered– Throughput is determined at the LLC SAP betw

een LLC and IP

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0

5

10

15

20

25

30

35

40

Datagram Size (octets)

Thro

ughp

ut (

Mbp

s)

Theoretical Throughput for 54 MbpsTheoretical Throughput for 54 Mbps

Preferred

Operation Range

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Packet Size StatisticsPacket Size Statistics

This statistics is from the measurement taken in this room in the morning of July 22nd 2003

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Frame AggregationFrame Aggregation

• Aggregation of multiple frames in order to reduce the fixed overheads relatively!

• Our frame aggregation approach was originally presented at the May 2003 meeting – Ref.

11-03-376r0-HTSG-Throughput Enhancement via Frame Aggregation

• Multiple frames are aggregated above the MAC SAP– The aggregated frame is transmitted via a data frame

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Frame Formats (Example)Frame Formats (Example)

octets: 2 2 6 6 6 2 variable 4

octets: 3 5 variable IP

datagramSNAP

HeaderLLC

Header

Frame Control

Duration / ID Addr 1 Addr 2 Addr 3

Seq. Control Data FCS

802.2 LLC

802.11 MAC

octets: 2 2 6 6 6 2 variable 4

octets: 1 1 1 1 2 2 2 variable variable

Frame Control

Duration / ID

Addr 1

Addr 2

Addr 3

Seq. Control Data FCS

802.2 LLC with aggregation

802.11 MAC

Control(0x03)

Count(n)

Size 1 ... Size nEtherframe

1Etherframe

n...

octets: 6 6 2 variableSource

Addr.Type IP datagram

DestinationAddr.

SSAP(0xdd)

DSAP(0xdd)

Reserved

Original

With aggregation

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Submission

Numerical Analysis with Channel ErrorNumerical Analysis with Channel Error

• Compare throughput performance vs. distance– Without aggregation

• One 1000 bytes frame (IP datagram size)

– With aggregation • Two 1000 bytes frames are aggregated

• Assumptions– Ideal rate-adaptation (maximizing throughput)

• Path loss exponent = 4 & Tx_power = 200 mW

– Based on error performance analysis assuming• Hard-decision Viterbi decoding with AWGN at the receiver

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Numerical Analysis ResultNumerical Analysis Result

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Some Lessons from Error PerformanceSome Lessons from Error Performance

Short distance (high Tx rate)

Long distance(low Tx rate)

Throughput gain

High Low

Error performance loss

Low High

• Frame aggregation seems always a good solution to improve throughput when the distance between sender and receiver is relatively short !

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Submission

Performance MeasurementPerformance Measurement• Implement frame aggregation in real platform• Linux & Intersil-based platform (11b)• Measure the throughput performance of UDP

and TCP traffic• Note: Frame aggregation is only applied when

there are multiple frames in the queue

Traffic generator AP STA

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New Measurement Results - UDPNew Measurement Results - UDP

Packet aggregation, RTP, 10Mbps

0

1

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3

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5

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8

0 200 400 600 800 1000 1200 1400 1600Packet Size (bytes, application-level)

Thr

ough

put (

Mbp

s)

original

aggregation

Theoretical

• Throughput performance of packet aggregation with fixed rate UDP

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New Measurement Results - TCPNew Measurement Results - TCP• Throughput performance of packet aggregation with

TCP

Packet Aggregation, TCP

0

1

2

3

4

5

6

7

0 200 400 600 800 1000 1200 1400 1600Packet Size (bytes, application-level)

Thr

ough

put (

Mbp

s)

original

aggregation

Theoretical

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ConclusionConclusion

• Shown via analysis that frame aggregation is a good way to improve 802.11 MAC efficiency

• Measurements from real implementation also show the performance enhancement

• Frame aggregation can be done above the MAC SAP very easily

• Frame aggregation can be considered an enhanced mechanism

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Future WorkFuture Work

• Measurement/simulations with more realistic traffic scenarios– Considering usage scenarios developed in

this group

• Incorporating the PHY channel error performance – Based on a more realistic simulation, not an

analysis (given here)

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Submission

Any Comments or Questions ?Any Comments or Questions ?

Documents

Doc.: IEEE 802.11-03/567r1 Submission July 2003 Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 1 Throughput Enhancement via Frame Aggregation – A Sequel