Backward compatibility of CDD preambles January 2005 doc.: IEEE 802.11-05/xxxxr0 January 2005 Backward compatibility of CDD preambles Date: 2005-01-xx Authors: 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 <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, 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 <stuart.kerry@philips.com> 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 <patcom@ieee.org>. Tsuguhide Aoki, Toshiba Corporation, et. al. Tomoko Adachi, Toshiba Corporation, et. al.

January 2005 doc.: IEEE 802.11-05/xxxxr0 January 2005 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. Tsuguhide Aoki, Toshiba Corporation, et. al. Tomoko Adachi, Toshiba Corporation, et. al.

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

Problem with WWiSE preamble January 2005 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-STF L-LTF L-SIG L-STF(400ns) L-LTF(3100ns) L-SIG(3100ns) Tx1 Tx2 WWiSE preamble (2TX Mixed-mode) Tsuguhide Aoki, Toshiba Corporation, et. al.

Cross-correlation in Legacy devices January 2005 Cross-correlation in Legacy devices Cross-correlation of .11a L-STS with .11a L-STS Period = 800ns Cross-correlation of WWiSE L-STS with .11a L-STS Period = 400ns Potential issues with cross-correlation receivers with WWiSE preamble Tsuguhide Aoki, Toshiba Corporation, et. al.

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

Measurement Setup TGn simulator Aeropeek NX RATE January 2005 Measurement Setup TGn simulator Aeropeek NX RATE LENGTH Compare the RATE and LENGTH RATE LENGTH Wireless 5.19GHz 10cm apart Omni transmit antenna WLAN card under test Agilent E4438C Enhanced Signal Generator (ESG) Tsuguhide Aoki, Toshiba Corporation, et. al.

Preamble performance with Auto-correlation Legacy RX January 2005 Preamble performance with Auto-correlation Legacy RX Tsuguhide Aoki, Toshiba Corporation, et. al.

Preamble performance with Cross-correlation Legacy RX January 2005 Preamble performance with Cross-correlation Legacy RX Tsuguhide Aoki, Toshiba Corporation, et. al.

Preamble performance with Auto-correlation Legacy RX January 2005 Preamble performance with Auto-correlation Legacy RX Tsuguhide Aoki, Toshiba Corporation, et. al.

Preamble performance with Cross-correlation Legacy RX January 2005 Preamble performance with Cross-correlation Legacy RX Performance limitation with a WWiSE preamble Error Floor! Tsuguhide Aoki, Toshiba Corporation, et. al.

Implication of using WWiSE preambles January 2005 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 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 Backup Tsuguhide Aoki, Toshiba Corporation, et. al.

Test procedure Test packets created in C simulator. January 2005 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. Tsuguhide Aoki, Toshiba Corporation, et. al.

Test procedure (cont’d) January 2005 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. Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 Aeropeek NX Tsuguhide Aoki, Toshiba Corporation, et. al.