Multi-User Cooperative Communications with Relay-Coding for Uplink IMT-Advanced 4G Systems

Adoption of relay stations has been commonly accepted as a key technique for future IMT-advanced 4G systems to improve the link performance. While study in relay systems is often carried out for individual users independently, in this paper, we present a design termed as relay-based multi-user cooperative communication specifically for the uplink of 4G systems. In this system, data streams from multiple users are coded at the relay with an invertible matrix in finite field. These coded data, with information of one user being spread into other data streams, are forwarded by the RS to the base station (BS). The relayed data received at the BS will work together with those received through the direct links between mobile stations (MS) and BS to implement a cooperative process. This is carried out using a turbo decoding process that alternates the decoding between a multi-user decoder and a number of single-user decoders. It is shown through the simulations that the decoding converges within two or three iterations, yet indeed provides significant gains compared with a reference relay system where each user is processed individually.