1. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 1 Serial CTS-to-SELF (CTS2SELF) Proposal: 20/40 MHz Coexistence in 2.4 GHz 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: 2006-12-11 Authors: NameCompanyAddressPhoneemail Matthew FischerBroadcom mfischer@broadcom.com Vinko Erceg Jason Trachewsky Broadcom verceg@broadcom.com jat@broadcom.com

2. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 2 Introduction For legacy devices to properly defer in 2.4 GHz spectrum in the presence of 40 MHz transmissions, two CTS-to-Self (CTS2SELF) transmissions can be employed by the 40 MHz devices. First transmission is on the primary channel followed by the second one on on the secondary channel after verifying that the secondary channel is idle. This solution solves the legacy deferral 20-40MHz coexistence issue without adding additional modes such as Duplicate CCK/DSSS transmission or mandating 25 MHz channel separation between primary and secondary channel.

3. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 3 Serial CTS2SELF Principle The sequence of 20 MHz transmissions is performed as two CTS2SELF frame transmissions, the first of which is transmitted on the primary channel. Examination of the CCA condition on the secondary channel follows. If the secondary channel CCA indicates an IDLE channel for a period of PIFS time following the end of the transmission of the primary channel CTS2SELF transmission, then the 40 MHz device can send a second CTS2SELF frame on the secondary channel. These two transmissions serve to inform 20 MHz devices of the pending occupancy of 40 MHz spectrum. This is accomplished by providing, a duration of time that conveys to the 20 MHz only device, the amount of time that it must remain idle in order to allow the subsequent 40 MHz transmissions to proceed uninterrupted.

4. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 4 Serial CTS2SELF Principle CTS2SELF may be sent using OFDM modulation in which case time-on-the-air is significantly shorter. CCK/DSSS modulation may be used on the secondary channel if the legacy device is 1 or 2 channel away.

5. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 5 Serial CTS2SELF example 1 A 40 MHz device’s 802.11 MAC function gains medium access and sends a pair of CTS2SELF frames in sequence, then follows those transmissions with a sequence of 40 MHz transmissions and receptions PIFS value depends on format of CTS2SELF, using 20 + 10 usec for DSSS/CCK format and 18 + 9 usec for ERP-OFDM format C2 = 20 MHz CTS2SELF frame transmission = 40 MHz transmissions and/or receptions and/or idle gaps CTS2SELF-receiving devices do not initiate transmissions during this time, but they may send response transmissions Time reserved by Duration/ID field of CTS2SELF for 40 MHz transmissions Secondary 20 MHz channel Primary 20 MHz channel C2 40 MHz device checks condition of secondary channel before transmitting IFS PIFS PIFS time value based on format of CTS2SELF frame Extent of Duration/ID NAV protection from the CTS2SELF frame

6. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 6 Serial CTS2SELF example 2 After transmitting the first CTS2SELF, the 40 MHz device finds that the secondary channel is BUSY, and therefore, decides to send only 20 MHz transmissions on the primary 20 MHz channel. The second CTS2SELF transmission is aborted. C2 = 20 MHz CTS2SELF frame transmission = 20 MHz transmissions and/or receptions and/or idle gaps in the primary 20 MHz channel CTS2SELF-receiving devices do not initiate transmissions during this time, but they may send response transmissions Time reserved by Duration/ID field of CTS2SELF for 40 MHz transmissions Secondary 20 MHz channel Primary 20 MHz channel 40 MHz device checks condition of secondary channel before transmitting, and it is found to be BUSY PIFS PIFS time value based on format of CTS2SELF frame Extent of Duration/ID NAV protection from the CTS2SELF frame Unrelated activity

7. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 7 Serial CTS2SELF example 3 The 40 MHz device finds that the secondary channel is BUSY, and decides to delay the transmission of the second CTS2SELF frame Not efficient, but does avoid collisions C2 = 20 MHz CTS2SELF frame transmission = 40 MHz transmissions and/or receptions and/or idle gaps CTS2SELF-receiving devices do not initiate transmissions during this time, but they may send response transmissions Time reserved by Duration/ID field of CTS2SELF for 40 MHz transmissions Secondary 20 MHz channel Primary 20 MHz channel C2 40 MHz device checks condition of secondary channel before transmitting, and it is found to be BUSY IFS PIFS PIFS time value based on format of CTS2SELF frame Extent of Duration/ID NAV protection from the CTS2SELF frame Unrelated activity

8. doc.: IEEE 802.11-06/1711r0 Submission November 2006 Matthew Fischer (Broadcom)Slide 8 Duplicate CKK/DSSS Disadvantages 1999-802.11b standard is not being followed because of the 20 MHz separation between the two CCK/DSSS channels. The standard recommendation is 25 MHz. It was not shown that the Duplicate CCK/DSSS mode actually works with legacy devices. It was not shown that the legacy devices will be OK with 20 MHz ACI and potential aliasing due to the 802.11b devices internal sampling at 11 MHz. Duplicate CCK/DSSS adds yet another mode to the standard that has to specified, discussed, implemented and tested while there were many LB84 comments to remove some of the modes.