1. doc.: IEEE 802.11-06/0854r1 Submission July 2006 Tom Kenney (Intel), Eldad Perahia (Intel)Slide 1 Regarding Protecting the Legacy Signal Field with the HT-SIG CRC in Mixed-Mode Packet 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 IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs 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: 2006-06-20 Authors: NameCompanyAddressPhoneemail Tom KenneyIntel JF3-336 2111 NE 25th Ave Hillsboro, OR 97124 503-712-8082 thomas.j.kenne y@intel.com Eldad PerahiaIntel JF3-336 2111 NE 25th Ave Hillsboro, OR 97124 503-712-8081 eldad.perahia @intel.com

2. doc.: IEEE 802.11-06/0854r1 Submission July 2006 Tom Kenney (Intel), Eldad Perahia (Intel)Slide 2 Abstract This presentation addresses the following letter ballot comments: –VK Jones; cid 3487 –Anuj Batra; cid 232 –Richard Van Nee; cid 8146 –Ali Raissinia; cid 7258 These comments propose to change the HT-SIG CRC to cover the L-SIG for L-SIG TXOP Protection support These comments should be rejected based on the analysis given in this presentation

3. doc.: IEEE 802.11-06/0854r1 Submission July 2006 Tom Kenney (Intel), Eldad Perahia (Intel)Slide 3 Introduction L-SIG length and rate field are used for spoofing and L-SIG TXOP Protection –Comments propose to change the HT-SIG CRC to cover the L-SIG for L- SIG TXOP Protection support –Note that this change will NOT provide any improved signal field detection for legacy devices The following analysis was conducted to provide statistics related to whether it is necessary to extend MM HT-SIG CRC to protect the L-SIG The specific intent of this analysis is to provide statistics of the various HT-SIG and L-SIG error event combinations The events were attained by simulating a HT Mixed Mode transmission and gathering the receiver statistics

4. doc.: IEEE 802.11-06/0854r1 Submission July 2006 Tom Kenney (Intel), Eldad Perahia (Intel)Slide 4 Classification Cases HT-SIG CRC failures due to HT-SIG bit errors have no impact on whether to extend the HT-SIG CRC to protect the L-SIG, the HT-SIG CRC would fail regardless Only the condition of HT-SIG CRC passing requires investigation Statistics for four L-SIG classification cases are collected, based on a HT-SIG CRC passing: case 1) L-SIG has no errors, and parity passes –there is no L-SIG error, so no additional protection would be provided by the HT-SIG CRC case 2) L-SIG parity passes, rate decoded correctly as 6Mbps, length decoded incorrectly –additional protection would be provided by the HT-SIG CRC case 3) L-SIG parity passes, rate decoded incorrectly –Rate field error is detectable by HT device, so no additional protection would be provided by the HT-SIG CRC case 4) L-SIG parity fails –Proper behavior of L-SIG, so no additional protection would be provided by the HT-SIG CRC Only case 2 benefits from additional protection by the HT-SIG CRC However, case 3 and 4 would unnecessarily cause the HT-SIG CRC to fail and cause a MM packet to fail

5. doc.: IEEE 802.11-06/0854r1 Submission July 2006 Tom Kenney (Intel), Eldad Perahia (Intel)Slide 5 Simulation Results – HT-SIG CRC Pass *Percent of HT-SIG CRC Pass As an example, for a 1x1 system, channel model B, 3 dB SNR, the probability of a HT-SIG CRC Pass is 66.3%. Given the occurrence of a HT-SIG CRC Pass: 98.8% of the events will have no L-SIG errors (case 1). 0.60% of the events will have an L-SIG parity bit failure (case 4). 0.29% of the events will have an L-SIG rate failure with L-SIG parity passing (case 3). 0.29% of the events will have an L-SIG length error with L-SIG parity passing (case 2). HT-SIGNo L-SIGL-LengthL-RateL-Parity Tx/RxCh.SNRCRC PassErrors*Error Only*Error*Fail* Model(dB)(%)( Case 1 )( Case 2 )( Case 3 )( Case 4 ) 1x1D369.9998.160.380.391.07 1x1B366.3098.820.29 0.60 2x2B069.7299.060.180.240.52 2x2D077.0698.870.240.200.69

6. doc.: IEEE 802.11-06/0854r1 Submission July 2006 Tom Kenney (Intel), Eldad Perahia (Intel)Slide 6 Summary It is not necessary to protect the L-SIG with the MM HT-SIG CRC –Protection of the L-SIG increases error events for HT demodulation since the additional error events in the L-SIG would cause a HT-SIG CRC error This increase is the sum of cases 2-4 of the HT-SIG CRC pass events 1% - 2% of the HT-SIG CRC pass events become CRC failures –Case 2 (L-SIG parity error), legacy length errors that go undetected without further protection These occur ONLY 0.2% - 0.4% of the HT-SIG CRC pass events Legacy devices do NOT benefit from any improved signal field detection with this proposed change