Green Field Compromise October 2006 doc.: IEEE 802.11-06/1560r1 December 2006 Green Field Compromise Date: 2006-12-08 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>. Eldad Perahia (Intel) Matthew Fischer (Broadcom)

October 2006 doc.: IEEE 802.11-06/1560r1 December 2006 Introduction There are 32 CIDs with Proposed Change of “make GF mandatory” Straw Poll Held on July 18, 2006 (06/968)– Shall the ability to process GF preambles be mandatory; Yes = 48, No = 78, Abstain = 9 There does not appear to be 75% support for making GF mandatory However, there does not appear to be 75% support for rejecting these comments We need a compromise Eldad Perahia (Intel) Matthew Fischer (Broadcom)

Currently Accepted Modifications to D1.0 October 2006 doc.: IEEE 802.11-06/1560r1 December 2006 Currently Accepted Modifications to D1.0 In D1.0: Green Field – … An HT device which does not support the reception of a GF packet shall be able to detect that GF transmissions are HT transmissions (as opposed to non-HT transmissions) and treat them as HT packets with a failing HT-SIG cyclic redundancy check (CRC). In D1.05: Green Field – … An HT STA that does not support the reception of a Greenfield packet shall be able to detect that Greenfield transmissions are HT transmissions (as opposed to non-HT transmissions). In this case the receiver shall decode the HT-SIG and determine if the HT-SIG cyclic redundancy check (CRC) passes.(Ed: CID 130, 7379) Eldad Perahia (Intel) Matthew Fischer (Broadcom)

Accepted Compromise in 06/1571r7 October 2006 doc.: IEEE 802.11-06/1560r1 December 2006 Accepted Compromise in 06/1571r7 Given that a non-GF HT device must check the validity of the GF HT-SIG CRC, it enables two options for the non-GF HT device Evaluate the contents of the HT-SIG and defer based on TXTIME Keep CCA busy until the received level drops below the CCA sensitivity level as adopted in 06-1571r7 (minimum modulation and coding rate sensitivity + 10 dB) Compromise: CRC check can be performed without evaluating the contents of the HT-SIG, so non-GF HT devices are not required to evaluate the contents of the GF HT-SIG GF packets will be robustly protected from non-GF devices based on the CCA procedure adopted in 06-1571r7 Given that the receive procedure in 06-1571r7 enhances the CCA threshold post a valid 8-bit CRC, the non-GF HT device is very well protected against false alarms Eldad Perahia (Intel) Matthew Fischer (Broadcom)

October 2006 doc.: IEEE 802.11-06/1560r1 December 2006 Proposed Resolution Counter all the “GF Mandatory” comments based on 06/1571r7 CIDs: 3150, 1665, 10377, 7474, 8283, 1731, 7171, 105, 289, 1494, 3617, 4185, 4572, 7011, 1502, 1513, 1612, 7183, 4679, 109, 134, 1725, 135, 10376, 136, 3430, 6766, 2131, 8171, 11242, 811, 7425 Eldad Perahia (Intel) Matthew Fischer (Broadcom)