Multiuser detection assisted near-real-time symbol transmission for relay CDMA systems

In this paper, we present a two-stage multiuser detection (MUD) scheme for near-real-time relay CDMA systems. Relay communications have received intensive research attention recently because of their benefit of spatial diversity. However, existing works generally have serious latency problems, which will reduce transmission rates. To solve the problems, we consider a near-real-time transmission strategy for relay CDMA systems. Also, a two-stage MUD scheme is proposed for the detectors at the relays and the destination node to ensure the feasibility of the transmission strategy. The proposed MUD scheme first conducts the zero forcing (ZF) method to suppress the multiple access interfere and then uses the maximum likelihood (ML) mechanism to estimate the transmitted symbols. Specially, the two-stage MUD scheme only requires few computations to conduct the ML mechanism. Simulation results and complexity analysis show that the proposed scheme can not only provide significant diversity gain with a modest computational complexity but also assist relay CDMAs to facilitate the near-real-time transmission.