Cooperative Cross-Layer Communication Month Year doc.: IEEE 802.11-06/1767r0 November 2006 Cooperative Cross-Layer Communication Date: 2006-11-14 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>. Monisha Ghosh, Philips John Doe, Some Company

November 2006 Abstract This presentation introduces various PHY layer cooperative communication concepts to the 802.11 community. Significant performance (throughput, range, reliability, etc.) enhancements are possible by the “cooperative” use of STAs in a 802.11 network, as opposed to “combative” use. Monisha Ghosh, Philips

Cooperative Communication Vs. Multihop November 2006 Cooperative Communication Vs. Multihop Direct Transmission Multi-hop Cooperative Monisha Ghosh, Philips

Advantages Of Cooperative Communications November 2006 Advantages Of Cooperative Communications Space diversity is achieved without the use of additional antennae – each station acts as a diversity transmitter for its partner: all stations benefit. Robustness against shadow fading. Reduced interference /lower transmission power: increased battery life, better frequency reuse. Greater range for the same transmitted power. Increased reliability and QOS. Higher throughput/lower delay: fewer retransmissions For 802.11, minor modifications needed to implement cooperative communications between stations. Monisha Ghosh, Philips

Some Cooperative Methods November 2006 Some Cooperative Methods Amplify and Forward Cooperative Coding Cooperative Symbol Rotation Cooperative HARQ Network Coding Monisha Ghosh, Philips

Amplify And Forward November 2006 Relay simply amplifies received signal and retransmits to destination. Destination processes signal from source AND relay. Drawback: noise is amplified as well. Nevertheless, has performance advantages. Equivalent channel model: Monisha Ghosh, Philips

Cooperative Coding Convolutional code, rate 1/4 November 2006 Source (S) transmits half the coded bits. Relay (R) receives, and if it can decode correctly, transmits the remaining coded bits. Destination receives all coded bits. Source and Relay can use different modulations to maximize throughput. Convolutional code, rate 1/4 Bits transmitted by S Bits transmitted by R for S Monisha Ghosh, Philips

Cooperative Coding: Performance November 2006 Cooperative Coding: Performance Ref.: Z. Lin, E, Erkip and M. Ghosh, “Adaptive Modulation For Coded Cooperative Systems,” SPAWC 2005 Monisha Ghosh, Philips

Cooperative Symbol Rotation November 2006 Cooperative Symbol Rotation Cooperation at the symbol level based on fully decode-and-forward at the bit level. Rotation matrices for QAM signal constellations and lattice-based modulation scheme can be applied. D-ReM-F: an application of linear modulation from integer rotation matrices to cooperative communications. Equivalent channel model: Monisha Ghosh, Philips

Cooperative Symbol Rotation: Performance November 2006 Cooperative Symbol Rotation: Performance Fast Rayleigh Fading channel. Symmetric case: source and relay have equal distance to destination Source-relay channel SNR = 20dB Block inter-leaver after CC BER performance D-ReM-F can provide signal space diversity Monisha Ghosh, Philips

Cooperative HARQ: concept November 2006 Cooperative HARQ: concept Cooperator selection Select the best relay as potential cooperator Cooperative HARQ If direct link (DATA) fails, relay transmits ARQ packet (DATA2) Receive combining If DATA2 = DATA Maximal-ratio combining of source and relay packets to get diversity gain If DATA2 = function (DATA) Optimal combining of source and relay packets to get coding and diversity gains DATA DATA2 Monisha Ghosh, Philips

Cooperative HARQ: performance November 2006 Cooperative HARQ: performance 50% gain over direct Best application scenario Diversity-limited channels and devices: low diversity available in space, time or frequency, e.g. single antenna devices in flat fading channels Dense networks: can leverage user density as a resource, capacity scales linearly as in MIMO (Ozgur, Leveque and Tse, “How does the information capacity of ad-hoc networks scale,” Allerton 2006.) Monisha Ghosh, Philips

Network coding: concept November 2006 Network coding: concept XOR in the air: Takes 3 slots 1 2 Current approach: Takes 4 slots 2 1 XOR the two packets, then broadcast 4 3 3 Decode, and then XOR with old packet Simple idea, can be extended to more complex configurations S. Katti, H. Rahul, W. Hu, D. Katabi, M. Medard, J. Crowcroft, “XORs in the air: practical wireless network coding,” ACM SIGCOMM’06 Monisha Ghosh, Philips

November 2006 Conclusions Multiple cooperative modes, at both PHY and MAC levels, can provide improved performance. In-home as well as enterprise deployments of 802.11 are perfectly suited for cooperative modes. Real-time applications, e.g. video would benefit from the higher throughput capabilities of cooperative methods. Monisha Ghosh, Philips