doc.: ieee 802.11-05/0006r1 submission january 2005 tsuguhide aoki, toshiba corporation, et....

January 2005

Tsuguhide Aoki, Toshiba Corporation, et. al.

Slide 1

doc.: IEEE 802.11-05/0006r1

Submission

Backward compatibility of CDD preambles

Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

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Date: 2005-01-17

Name Company Address Phone email Tsuguhide Aoki Toshiba

Corporation 1, Komukai Toshiba-

cho, Saiwai-ku, Kawasaki

+81-44-549-2433 [email protected]

Daisuke Takeda Toshiba Corporation

1, Komukai Toshiba-cho, Saiwai-ku,

Kawasaki

+81-44-549-2433 [email protected]

Authors:

January 2005


Slide 2

doc.: IEEE 802.11-05/0006r1

Submission

Abstract

• The backward compatibility of the WWiSE and TGnSync preambles is examined by laboratory test.

• Results show that the WWiSE preamble is not fully backwards compatible, and that the TGnSync preamble is much more robust.

January 2005


Slide 3

doc.: IEEE 802.11-05/0006r1

Submission

L-STF L-LTF L-SIGL-STF(400ns) L-LTF(3100ns) L-SIG(3100ns)

Tx1Tx2

L-STF

.11a preambleL-LTF L-SIGTx1

WWiSE preamble (2TX Mixed-mode)


Tx1Tx2

TGn Sync preamble (2TX)

Preamble structures (first 3 fields)

Values shown in brackets indicate the amount of CDD delay

January 2005


Slide 4

doc.: IEEE 802.11-05/0006r1

Submission

Problem with WWiSE preamble

• Some legacy devices use the auto-correlation technique for synchronization whilst other legacy devices use the cross-correlation technique.

• The large cyclic shift (400nsec) on the WWiSE L-STF can affect the time synchronization of legacy devices that use the cross-correlation technique.


Tx1Tx2

WWiSE preamble (2TX Mixed-mode)

January 2005


Slide 5

doc.: IEEE 802.11-05/0006r1

Submission

Cross-correlation in Legacy devices

Cross Correlation with STS

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5

microseconds

Ab

so

lute

Va

lue

of

Cro

ss

Co

rre

lati

on

Cross Correlation with STS

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5

microseconds

Ab

so

lute

Va

lue

of

Cro

ss

Co

rre

lati

on

Cross-correlation of .11a L-STS

with .11a L-STS

Cross-correlation of WWiSE L-STS

with .11a L-STS

Period = 800ns

Period = 400ns

Potential issues with cross-correlation receivers with WWiSE preamble

January 2005


Slide 6

doc.: IEEE 802.11-05/0006r1

Submission

Rx1Packet

generatorTGn

Channel model

Tx1

Tx2

C simulator Agilent E4438C

Single inputsingle output

signal generatorNormalized

Test setup

• Test packets generated in C simulator

• TX signals are convolved with a simulated TGn channel

• Signal generator is used for up-conversion

January 2005


Slide 7

doc.: IEEE 802.11-05/0006r1

Submission

Measurement Setup

Compare the RATE and LENGTH

TGn simulator

WLAN cardunder test

Aeropeek NX

Agilent E4438CEnhanced Signal Generator (ESG)

Wireless

5.19GHz10cm apartOmni transmit antenna

RATELENGTH RATE

LENGTH

January 2005


Slide 8

doc.: IEEE 802.11-05/0006r1

Submission

Preamble performance with Auto-correlation Legacy RX

"Auto Correl ati on Vendor" (Channel B)

1. 00E-03

1. 00E-02

1. 00E-01

1. 00E+00

-30 -25 -20 -15 -10 -5 0Normal i zed Tx power f rom ESG [dB]

Meas

ured

SIG

err

or

1TX - . 11a preambl e2TX - TGn Sync (50ns)2TX - WWi SE (400ns)

January 2005


Slide 9

doc.: IEEE 802.11-05/0006r1

Submission

Preamble performance with Cross-correlation Legacy RX

"Cross Correl ati on Vendor" (Channel B)

1. 00E-03

1. 00E-02

1. 00E-01

1. 00E+00


Meas

ured

SIG

err

or

1TX - . 11a2TX - TGnSync (50ns)2TX - WWi SE (400ns)

January 2005


Slide 10

doc.: IEEE 802.11-05/0006r1

Submission

Preamble performance with Auto-correlation Legacy RX

"Auto Correl ati on Vendor" (Channel D)

1. 00E-03

1. 00E-02

1. 00E-01

1. 00E+00


Meas

ured

SIG

err

or


January 2005


Slide 11

doc.: IEEE 802.11-05/0006r1

Submission

"Cross Correl ati on Vendor" (Channel D)

1. 00E-03

1. 00E-02

1. 00E-01

1. 00E+00

-30 -25 -20 -15 -10 -5 0 Normal i zed Tx power f rom ESG [dB]

Meas

ured

SIG

err

or


Preamble performance with Cross-correlation Legacy RX

Error Floor!Error Floor!

Performance limitation with a WWiSE preamble

January 2005


Slide 12

doc.: IEEE 802.11-05/0006r1

Submission

Implication of using WWiSE preambles

• Legacy devices with a cross-correlation RX will not correctly decode a WWiSE preamble

• Hence, such legacy devices will not defer to a WWiSE HT transmission, potentially creating collisions in the BSS– BSS throughput would drop, and latency would increase

• WWiSE preamble is not legacy compatible• Lab test reinforces TGn Sync’s decision to use a 100%

backwards compatible legacy preamble

January 2005


Slide 13

doc.: IEEE 802.11-05/0006r1

Submission

Backup

January 2005


Slide 14

doc.: IEEE 802.11-05/0006r1

Submission

Test procedure• Test packets created in C simulator.

– Rate= 6Mbps, Date=42bytes, broadcast address and data packet.

– IFS = 1msec

• 100 packets created in C simulator, each convolved with randomly generated TGn channel and saved in the ESG.

• Total 18369 packets transmitted in 20 seconds.

January 2005


Slide 15

doc.: IEEE 802.11-05/0006r1

Submission

Test procedure (cont’d)• Measure the Rate and Length (bytes) in the Signal Field at

Aeropeek, and compare them with the predetermined value.– Aeropeek: can observe Signal field and MAC information decoded by the

WLAN card.

• Calculate Signal Field Error Rate (SFER) by using Rate and Length.

seconds 20in ed transmittPackets

length) and (rate detected correctlly Packets1RateError SIG

January 2005


Slide 16

doc.: IEEE 802.11-05/0006r1

Submission

Aeropeek NX

doc.: ieee 802.11-05/0006r1 submission january 2005 tsuguhide aoki, toshiba corporation, et....

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