A low complexity SCMA detector based on dynamic factor graph reduction

Abstract

Sparse code multiple access (SCMA), a competitive air-interface technology with the message passing algorithm (MPA) employed at the receiver, has a broad application prospect. However, the computational complexity of MPA is still an extreme challenge for SCMA detection. A low complexity multiuser detection algorithm, dynamic factor graph reduction based MPA (DFGR-MPA), is proposed for the SCMA uplink system in this paper. The algorithm classifies the variable nodes according to the convergence of the codeword probability, and reconstructs a new factor graph with the variable nodes whose codeword probability has not reached the target convergence and the related function nodes for subsequent iteration. The DFGR-MPA algorithm can reduce the detection complexity by reducing the number of nodes involved in message iterations and the average number of iterations. Numerical results demonstrate that the proposed scheme can achieve an affordable trade-off between bit error ratio (BER) performance and detection complexity for SCMA system.