Sparse Code Multiple Access Asynchronous Uplink Multiuser Detection Algorithm

Sparse code multiple access (SCMA) is one type of non-orthogonal multiple access techniques for the fifth generation (5G) wireless communication networks. Existing multiuser detection algorithms for SCMA uplink systems are based on the assumption that signals are synchronization. However, asynchrony cannot be neglected due to the propagation delays in practical environments. In this paper, we present three detection algorithms for asynchronous uplink SCMA systems, namely the belief propagation message passing (BP-MPA), belief propagation with equal gain combining message passing algorithm (BP-EGCMPA) and partial phase-coherent algorithms. Simulation results show that our proposed asynchronous detection algorithms are able to offer descent bit error rate (BER) performances, with only a small performances loss compared to the synchronous case. Moreover, our proposed algorithms converge well in the asynchronous SCMA uplink system.