1. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 1 Simplified ‘Express’ Forwarding for single-channel wireless mesh 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: 2007-11-15 Authors: NameAddressCompanyPhoneEmail Mathilde Benveniste 233 Mt Airy Road Basking Ridge, NJ 07920, US Avaya Labs- Research 973-761-6105benveniste@iee e.org

2. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 2 Simplified‘Express’ Forwarding for Single-Channel Wireless Mesh Simplified ‘Express’ Forwarding for Single-Channel Wireless Mesh Mathilde Benveniste Avaya Labs - Research

3. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 3 Introduction The express forwarding method has been simplified as follows: The forwarding node does not have to set a NAV

4. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 4 Single channel ‘express’ forwarding

5. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 5 Express Forwarding procedure A known time increment DT0 (MIB variable Dot11MeshDTC) is added to the value of the Duration field when a TSQ frame is forwarded to a node other than the final destination The Duration field of the ACK (if any) returned for the TSQ frame received at the destination node is set based on the Duration field of the received frame All nodes that hear the transmission other than the receiving node set their NAV according to the Duration field of the received transmission If the receiving node forwards the frame, it attempts transmission with no backoff (after an AIFS idle) –DT0 is at least one timeslot long; it would not be more than a couple of timeslots –It allows for the forwarding node to process the received frame DT0 >= 1 timeslot + node processing delay – AckTime - SIFS

6. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 6 Express Forwarding Illustration The Duration field is set at value longer than usual when a TSQ frame is transmitted to a forwarding node of a multi-hop path; the increment DT0 >= 1 timeslot + IP processing delay – AckTime - SIFS The forwarding nodes, 2 and 3, transmit after an AIFS idle following Ack The non-forwarding neighbor nodes (e.g. 5) set NAV according to Duration field NAV setting at all other neighbor nodes NAV setting at receiving node Channel time ACK Value in Duration field of TSQ frame 12 1-2 Frame 3 4 2-3 DT0 3-hop path 1-4 3-4 5 ANIMATED

7. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 7 Express Retransmission Retransmission typically involves backoff using a wider contention window With express retransmission, a frame is retransmitted by dispensing with backoff and transmitting after SIFS following AckTimeout, within DT0 time period An express forwarded frame is less likely to collide on retransmission because of its prioritization Only the first retransmission attempt receives priority treatment Subsequent retransmission attempts use backoff from contention window expanded according to the standard

8. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 8 Express Retransmission Only the first retransmission attempt receives priority treatment Prevents two express-forwarded frames from colliding repeatedly Subsequent retransmission attempts less likely to lead to collision when using large CWmax Channel time ACKtimeout TSQ Frame DT0 TSQ Retransmission NAV setting at all other neighbor nodes NAV setting at receiving node Value in Duration field of TSQ frame

9. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 9 Straw Poll Do you oppose the change to remove time-critical frame handling? Yes No

10. doc.: IEEE 802.11-07/2910r0 Submission November 2007 Mathilde Benveniste, Avaya LabsSlide 10 Motion Move to adopt the changes in Doc 11-07-2453r1 into the TGs Draft D1.07