Multiuser Detection for Uplink DS-CDMA Amplify-and-Forward Relaying Systems

We consider the uplink of a cooperative DS-CDMA communication system, where each user communicates with the base station through a direct link and with the help of relays. A multiuser detection approach for the joint estimation of spatial signatures, channel gains and transmitted symbols of all the users is proposed. Such an approach is derived from a trilinear tensor model for the received signal that combines the source-destination and relay-destination links. The proposed multiuser receiver provides an extension of the traditional trilinear DS-CDMA receiver to cooperative relaying systems, by including the users' relay-assisted links into the trilinear model. Moreover, in contrast to a previous work by the authors, where the relays of a cluster transmit over orthogonal channels, the proposed receiver operates in a more attractive scenario where all the relays simultaneously transmit towards the base station without requiring orthogonal codes. Simulation results illustrate the performance of the proposed receiver in comparison with alternative approaches.