1. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 1 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. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at.http:// ieee802.org/guides/bylaws/sb-bylaws.pdfstuart.kerry@philips.compatcom@ieee.org Date: 2005-01-17 Authors:

2. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 2 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.

3. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 3 L-STFL-LTFL-SIG L-STF(400ns)L-LTF(3100ns)L-SIG(3100ns) Tx1 Tx2 L-STF.11a preamble L-LTFL-SIG Tx1 WWiSE preamble (2TX Mixed-mode) L-STFL-LTFL-SIG L-STF(50ns)L-LTF(50ns)L-SIG(50ns) Tx1 Tx2 TGn Sync preamble (2TX) Preamble structures (first 3 fields) Values shown in brackets indicate the amount of CDD delay

4. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 4 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. L-STFL-LTFL-SIG L-STF(400ns)L-LTF(3100ns)L-SIG(3100ns) Tx1 Tx2 WWiSE preamble (2TX Mixed-mode)

5. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 5 Cross-correlation in Legacy devices 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

6. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 6 Rx1 Packet generator TGn Channel model Tx1 Tx2 C simulator Agilent E4438C Single input single output signal generator Normalized Test setup Test packets generated in C simulator TX signals are convolved with a simulated TGn channel Signal generator is used for up-conversion

7. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 7 Measurement Setup Compare the RATE and LENGTH TGn simulator WLAN card under test Aeropeek NX Agilent E4438C Enhanced Signal Generator (ESG) Wireless 5.19GHz 10cm apart Omni transmit antenna RATE LENGTH RATE LENGTH

8. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 8 Preamble performance with Auto-correlation Legacy RX

9. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 9 Preamble performance with Cross-correlation Legacy RX

10. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 10 Preamble performance with Auto-correlation Legacy RX

11. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 11 Preamble performance with Cross-correlation Legacy RX Error Floor! Performance limitation with a WWiSE preamble

12. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 12 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

13. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 13 Backup

14. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 14 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.

15. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 15 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.

16. doc.: IEEE 802.11-05/0006r1 Submission January 2005 Tsuguhide Aoki, Toshiba Corporation, et. al.Slide 16 Aeropeek NX