Fair and protected DLS July 2007 Date:2007-07-17 LG Electronics 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>. LG Electronics

Outline Intuitive motivation of direct link protection July 2007 Outline Intuitive motivation of direct link protection Substantiation: simulation results RTS/CTS approach DL protection – only the tip of the iceberg Towards protection, spatial reuse and fairness LG Electronics

QSTAs use 11e tools We assume legacy AP and QSTAs July 2007 QSTAs use 11e tools We assume legacy AP and QSTAs QSTAs use state-of-the-art 11e data transmission scheme: QSTAs get TXOPs to transmit data and use Block ACK mechanism with Immediate ACK policy LG Electronics

Intuitive motivation of direct link protection July 2007 Intuitive motivation of direct link protection 3->4 RTS 4->3 CTS 1 heard nothing 2 heard RTS but not CTS While 3->4 DATA: 1->2 RTS 2 doesn’t reply CW of 1 increases 1->2 retry RTS, no answer CW of 1 increases again … In contention between 3 and 1, 3 wins almost always 3->4 DATA: 1 drops the packet (lifetime) LG Electronics

We are going to consider the following cases July 2007 We are going to consider the following cases 2 1 3 4 LG Electronics

Simulation assumptions July 2007 Simulation assumptions QSTAs use: legacy data transmission mechanism 11e block data transmission mechanism Initiators of direct transmissions (QSTAs 1 and 3) work in saturation 11a PHY, 54 Mbps LG Electronics

Case 1 July 2007 All four QSTAs are in TX-range of one another LG Electronics

Case 2 July 2007 QSTAs 1 and 4 are in CS-range of one another LG Electronics

July 2007 Case 3 QSTAs 1 and 4 don’t hear one another LG Electronics

Case 4 July 2007 QSTAs 1 and 4 don’t hear one another QSTAs 1 and 3, and 2 and 4 are in CS-range of one another LG Electronics

Case 5 July 2007 QSTAs 2 and 3 are in TX-range of one another LG Electronics

Case 6 July 2007 QSTAs 2 and 3 are in CS-range of one another LG Electronics

Case 7 July 2007 Two pairs of QSTAs cannot hear one another LG Electronics

RTS/CTS approach July 2007 It’s a good approach: RTS CTS But… DATA Simple Standard frames Reliable protection of direct links RTS CTS But… DATA LG Electronics

RTS/CTS approach July 2007 But it allows NO spatial reuse 3->AP RTS AP->3 CTS (broadcast) The CTS from AP prohibits all other transmissions However, transmissions 1->2 and 3->4 would be possible at the same time Solution? LG Electronics

Another problem: unfairness July 2007 Another problem: unfairness Non-direct: AP queues DATA First contention: 1->AP Queueing delay at AP Second contention: AP->2 AP is a bottleneck for several non-direct links 2 Direct: The only contention 3->4 So, direct link gets much more of total throughput at the expense of non-direct link Solution? LG Electronics

Unfairness: Case A Simulation results: Links: July 2007 In non-saturation: See Figure below In saturation: Link 3->4 throughput: 27.2 Mbps Links 1->2 and 5->6 throughput: 0.7 Mbps each Reasons: The same as in Case 5 AP is a bottleneck Links: DL connection: 3->4 Non-DL connections: 1->AP->2 and 5->AP->6 LG Electronics

Unfairness: Case B Simulation results: July 2007 Links: DL connection 3->4 Non-DL connections between legacy stations: 1->AP->2 and 5->AP->6 No obstacles Simulation results: In non-saturation: See Figure below In saturation Link 3->4 throughput: 7.5 Mbps Links 1->2 and 5->6 throughput: 3.4 Mbps each Reason: AP is a bottleneck LG Electronics

Solution towards protection, spatial reuse and fairness July 2007 Solution towards protection, spatial reuse and fairness We propose to introduce a special Direct Link Announcement (DLA) action frame Basic idea: the source QSTA shall broadcast/multicast the DLA frame over the AP LG Electronics

DLA payload Direct transmission source and its destination July 2007 DLA payload Direct transmission source and its destination Duration of the planning direct transmission (a-lá NAV) DLA expiration time; after the time, DLA should be ignored LG Electronics

Our approach: Scheme 1 July 2007 AP queues the DLA Protection: All QSTAs are informed of the planning direct transmission and its duration Upon receiving DLA back, QSTA 3 starts DATA after PIFS without contention Fairness: It takes two contention phases and queueing delay at the AP to start transmissions, equally direct or non-direct DLA DLA ACK DATA LG Electronics

Our approach: Scheme 1(continue) July 2007 Our approach: Scheme 1(continue) Spatial reuse : During DL Setup or by other radio measurement procedures, QSTAs collect a list of neighbors which it may interfere with The list is included into the DLA QSTAs which are not in the list may communicate during the direct transmission without sending DLA frames DLA DATA 5 DATA LG Electronics

Our approach: Scheme 2 July 2007 Spatial reuse : QSTAs don’t need to rely on knowledge of the list of neighbors which it may interfere with Upon receiving DLA back from the AP, 3 starts RTS/CTS with 4 without contention QSTAs which heard DLA, but neither RTS nor CTS, may communicate during the direct transmission DLA DATA 5 CTS DATA RTS LG Electronics

Combination with RTS/CTS approach July 2007 Combination with RTS/CTS approach DLA timeout: RTS/CTS approach upon DLA timeout expiration Protection from legacy STAs LG Electronics

Our approach: Scheme 3 July 2007 Combination of Scheme 1 and RTS/CTS approach Aim: to improve the direct link protection from legacy STAs DLA DATA 5 RTS CTS DATA LG Electronics

Our approach: Scheme 4 July 2007 Combination of Scheme 2 and RTS/CTS approach Aim: to improve the direct link protection from legacy STAs DLA DATA 5 RTS CTS CTS DATA RTS LG Electronics

Thanks for your kind attention! July 2007 Thanks for your kind attention! LG Electronics

July 2007 Call for interest Who’s interested in getting together to work on this? What should be the next steps: Preparation the normative text ? LG Electronics