1. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 1 Access Point Collaboration 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 stuart@ok-brit.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.http:// ieee802.org/guides/bylaws/sb-bylaws.pdf stuart@ok-brit.compatcom@ieee.org Date: 2007-07-16 Authors:

2. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 2 Abstract This presentation describes a mechanism to allow multiple APs on the same channel to cooperatively share time on the wireless medium This enables enhanced QoS by allowing collaborating APs to avoid allocating overlapping CFPs and reduced probability of EDCA collisions Proposal fulfils requirement 2050 “Access Point Coordination” of the TGV objectives

3. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 3 Introduction We want to use 802.11 for “carrier grade” wireless voice & video distribution system Current QoS solutions not well suited to multiple BSS on the same channel –In some bands there are insufficient channels for every home to have its own channel –Enterprise environment may have even higher AP densities Fulfils requirement 2050 “Access Point Coordination” of the TGV objectives –TGv shall facilitate Access Point Coordination in order to meet various objectives.

4. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 4 Scope Improved throughput & QoS for multiple BSS on same channel within RF range –In both domestic and enterprise environments Domestic –Over-the-air communication –No central management entity Enterprise –Wireless or DS used for communication –Possibly a central management entity

5. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 5 Example Domestic Application Multiple dwelling unit Many homes within radio range of each other Homes share channels either due to insufficient channels or imperfect channel selection

6. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 6 A Typical Enterprise Application

7. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 7 Design Requirements Provide benefits in all QoS modes and even non-QoS BSS Simple to implement –Simple to implement in AP –No changes to non-AP STAs Compatible with legacy equipment Robust to rogue STAs Allows for dynamic changes in each BSS –Number of active streams in a BSS changes –Channel conditions change

8. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 8 Proposal Genesis EDCA, PCF and HCCA all have the concept of giving a TXOP to a STA STA can decline TXOP STA can use TXOP for a specified duration –But doesn’t have to use all of it AP has handed medium access to the STA –But with a defined process for AP to regain control Why not allow APs to do the same? –Just not with only SIFS notice!

9. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 9 AP Collaboration Proposal AP advertises that it supports collaboration –A new capability bit (from Extended Capabilities IE) in beacons and probe responses An AP can choose to offer silent time to another AP –If accepted, the AP silences its self and associated STAs for the specified time AP silences its BSS using a feature added in 11h –If there are associated STAs without spectrum management support, an additional protection mechanism using CF-Poll is used The recipient AP can detect if the offering AP “cheats” –By checking beacon frames from offering AP The recipient AP can end the silence time early if not required NEW

10. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 10 Over-the-air Collaboration SME MAC Initiating APRecipient AP CF-Offer CF-Response MLME- CFOFFER.request MLME- CFOFFER.indication MAC SME MLME- CFRESPONSE.request MLME- CFRESPONSE.indication MLME- CFOFFER.confirm MLME- CFRESPONSE.confirm

11. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 11 Via-DS Sharing Diagram Beacon AP #1 Beacon AP #2 Beacon Offset Silent Period Offset Exclusive Use - AP #2 CFP AP #2 Silent Period Duration Grant Period Offset Grant Period Duration CF-Poll-to-self AP #1

12. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 12 Beacon Silence Period Active Period TBTT AP1 AP2 AP3 AP4 After receiving either a quiet element or a CF-Poll-to-Self, STAs in the silence period optionally turnoff the NIC to further reduce the energy consumption. AP collaboration using a centralized management entity can provide both a throughput enhancement and a power saving. Example via-DS Scheduling

13. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 13 Simulation Results Based on “medium” house model –House size based on typical UK housing –Based on typical UK construction materials Two video streams –At rates between 1Mbit/sec and 10Mbit 2.4GHz band –11g, no throughput extensions –No DLS, 2 hops per packet –EDCA and HCCA modes Each combination repeated 20 times with different random number seed –800 simulation runs, ≈6 simulated hours

14. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 14 Simulation Results For EDCA, average gain was 9% (peak gain 34%) For HCCA, average gain was 6% (peak gain 22%)

15. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 15 When is collaboration beneficial? 1.On a lightly loaded network, no need for collaboration 2.As network load increases, chances of inter-BSS collisions increase. Collaboration reduces these collisions to allow greater throughout 3.As network load exceeds achievable throughput, benefits from collaboration reduce 4.At close distances, maximum probability of collisions. 5.Eventually a sufficient distance is reached so that BSS no longer overlap 1 2 4 3 5

16. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 16 Summary The proposal described in this presentation: Improves efficiency and QoS –Reduces chances of collisions for CSMA/CA traffic Collisions cause back-offs and PHY rate adaptation –Reduces chances of CFP collisions when using PCF or HCCA –Could be used to trigger an HCCA CAP –Could be used for power saving Simple to implement –Largely based on existing 802.11 features –A simple Tit-for-tat algorithm provides fairness for WM distribution –A simple round-robin scheduler provides fairness for DS distribution

17. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 17 Motion Motion: “Instruct the editor to include the changes in document 11-07-2074-00-000v-access-point- collaboration.doc into the TGv draft” Mover/Seconder: Result –Yes –No –Abstain

18. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 18 References

19. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 19 (Backup Material) Simulation Parameters

20. doc.: IEEE 802.11-07/2115r0 Submission July 2007 Alex Ashley (NDS Ltd), Robert Miller (AT&T)Slide 20 Simulation Parameters House –Size 27’ x 27’ (729 sq feet) –Brick outer wall construction with plaster on inside face –2 layers drywall inner wall construction –Plaster & wood floor construction –2 floors –8 rooms Network –2.4GHz (11bg) in European regulatory domain (ETSI EN 300 328) –100ms beacon interval –Dynamic PHY rate adjustment –Fixed transmit power –1 AP per home –6 STAs per home –2 RTP UDP video streams, each from non-AP STA to non-AP STA –7 MPEG-2 TS packets (of 188 bytes) per RTP packet Collaboration –owMin=1 –owMax=16 –offerDuration = 20ms