doc.: ieee 802.11-03/567r1 submission july 2003 youngsoo kim, samsung/snu and s. choi, snu slide 1...

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)

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 2

doc.: IEEE 802.11-03/567r1

Submission

ContentsContents

• Introduction

• Frame aggregation

• New Results– Numerical throughput analysis with channel

error

– Performance measurement using TCP and UDP traffic

• Conclusion

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 3

doc.: IEEE 802.11-03/567r1

Submission

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 4

doc.: IEEE 802.11-03/567r1

Submission

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 5

doc.: IEEE 802.11-03/567r1

Submission

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 6

doc.: IEEE 802.11-03/567r1

Submission

Packet Size StatisticsPacket Size Statistics

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 7

doc.: IEEE 802.11-03/567r1

Submission

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 8

doc.: IEEE 802.11-03/567r1

Submission

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 9

doc.: IEEE 802.11-03/567r1

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 10

doc.: IEEE 802.11-03/567r1

Submission

Numerical Analysis ResultNumerical Analysis Result

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 11

doc.: IEEE 802.11-03/567r1

Submission

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 !

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 12

doc.: IEEE 802.11-03/567r1

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 13

doc.: IEEE 802.11-03/567r1

Submission

New Measurement Results - UDPNew Measurement Results - UDP

Packet aggregation, RTP, 10Mbps

0

1

2

3

4

5

6

7

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 14

doc.: IEEE 802.11-03/567r1

Submission

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 15

doc.: IEEE 802.11-03/567r1

Submission

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

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 16

doc.: IEEE 802.11-03/567r1

Submission

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)

July 2003

Youngsoo Kim, Samsung/SNU and S. Choi, SNU Slide 17

doc.: IEEE 802.11-03/567r1

Submission

Any Comments or Questions ?Any Comments or Questions ?