January 2005 doc IEEE 802 11 050006 r

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Backward compatibility of CDD preambles Authors: Date: 2005 -01 -17 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: // ieee 802. 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>. Submission 1 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Abstract • The backward compatibility of the WWi. SE and TGn. Sync preambles is examined by laboratory test. • Results show that the WWi. SE preamble is not fully backwards compatible, and that the TGn. Sync preamble is much more robust. Submission 2 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Preamble structures (first 3 fields). 11 a preamble Tx 1 L-STF L-LTF L-SIG TGn Sync preamble (2 TX) Tx 1 Tx 2 L-STF(50 ns) L-LTF(50 ns) L-SIG(50 ns) WWi. SE preamble (2 TX Mixed-mode) L-STF(400 ns) L-LTF L-SIG L-LTF(3100 ns) L-SIG(3100 ns) Values shown in brackets indicate the amount of CDD delay Submission 3 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Problem with WWi. SE preamble • Some legacy devices use the auto-correlation technique for synchronization whilst other legacy devices use the crosscorrelation technique. • The large cyclic shift (400 nsec) on the WWi. SE L-STF can affect the time synchronization of legacy devices that use the crosscorrelation technique. Tx 1 Tx 2 Submission WWi. SE preamble (2 TX Mixed-mode) L-STF(400 ns) L-LTF L-SIG L-LTF(3100 ns) L-SIG(3100 ns) 4 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Cross-correlation in Legacy devices Cross-correlation of. 11 a L-STS with. 11 a L-STS Period = 800 ns Cross-correlation of WWi. SE L-STS with. 11 a L-STS Period = 400 ns Potential issues with cross-correlation receivers with WWi. SE preamble Submission 5 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 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 Tx 1 Packet TGn generator Tx 2 Channel model Submission Agilent E 4438 C Rx 1 6 Single input single output Normalized signal generator Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Measurement Setup TGn simulator Aeropeek NX Compare the RATE and LENGTH RATE LENGTH Wireless 5. 19 GHz 10 cm apart Omni transmit antenna Agilent E 4438 C Enhanced Signal Generator (ESG) Submission 7 WLAN card under test Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Preamble performance with Auto-correlation Legacy RX Submission 8 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Preamble performance with Cross-correlation Legacy RX Submission 9 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Preamble performance with Auto-correlation Legacy RX Submission 10 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Preamble performance with Cross-correlation Legacy RX Performance limitation with a WWi. SE preamble Error Floor! Submission 11 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Implication of using WWi. SE preambles • Legacy devices with a cross-correlation RX will not correctly decode a WWi. SE preamble • Hence, such legacy devices will not defer to a WWi. SE HT transmission, potentially creating collisions in the BSS – BSS throughput would drop, and latency would increase • WWi. SE preamble is not legacy compatible • Lab test reinforces TGn Sync’s decision to use a 100% backwards compatible legacy preamble Submission 12 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Backup Submission 13 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Test procedure • Test packets created in C simulator. – Rate= 6 Mbps, Date=42 bytes, broadcast address and data packet. – IFS = 1 msec • 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. Submission 14 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 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. Submission 15 Tsuguhide Aoki, Toshiba Corporation, et. al.

January 2005 doc. : IEEE 802. 11 -05/0006 r 1 Aeropeek NX Submission 16 Tsuguhide Aoki, Toshiba Corporation, et. al.