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 Ghozlan
E-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
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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.
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.
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).
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.