1. MIMO Relaying for Universal Frequency Reuse in IEEE 802.16m Document Number: IEEE C802.16m-08/1370 Date Submitted: 2008-10-31 Source: Hesham El Gamal E-mail:helgamal@ece.osu.edu The Ohio State University Hassan GhozlanE-mail:hassan.ghozlan@nileu.edu.eg Nile University Mohamed Nafie Cairo University Re: TGm SDD: Relay IEEE 802.16m-08/040, Call for Contributions and Comments on Project 802.16m System Description Document SDD)”. - Target topic: “Support for Relay (Relaying Model)” Abstract : This contribution proposes a relaying technique Purpose: For discussion and approval by TGm Note: This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who 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 802.16. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. IEEE C802.16m-08/1370 The Fundamental Idea Users at the cell edges suffer from high interference levels. Using low reuse factors for such users solves the interference problem at the expense of a significant price in throughput. Here, we propose a novel approach to allow universal frequency reuse at the cell edges using MIMO relays.

3. IEEE C802.16m-08/1370 Spatial Multiplexing for MIMO Relaying Let’s consider two edge users (U1,U2) communicating with two neighboring base-stations (B1, B2). The MIMO relay node (M)is assumed to be equipped with 4 antennas. The communication is divided in two phases In the multiple access phase, the four nodes (U1,U2,B1,B2) send their messages to M. In the broadcast phase, M broadcasts four messages to the four nodes simultaneously. This way, four messages are exchanged in two time slots resulting in a reuse factor of one for the two cells.

4. IEEE C802.16m-08/1370 The Effect of Channel State Information The TDD approach described in the previous slide assumes that the MIMO relay has accurate CSI about the four channels to enable multi-use beamforming (or dirty paper coding) in the broadcast phase. Using a simple network coding approach, one can get around this assumption at the price of one more time slots. Still, the resulting reuse factor will be 2/3 (significantly higher than the current approach).

5. IEEE C802.16m-08/1370 Summary This contribution overviews a novel approach for utilizing MIMO relaying to enhance the frequency re-use factor at the cell edges. The proposed approach avoids the complexity of the cooperative base-station approach. Here, we offered an architectural example demonstrating the power of the idea in a simple two cell scenarios. More algorithmic details, simulations studies, and experimental results will be provided in future contributions.