Downlink Multiple Input Multiple Output Mixed Sparse Code Multiple Access for 5G System

For downlink multiple-input multiple-output-sparse code multiple access (MIMO-SCMA) system, the convergence reliability of the detected codeword in each decision process is unsatisfactory at the message passing algorithm receiver. To address this problem, a downlink MIMO-mixed sparse code multiple access (MIMO-MSCMA) system is proposed in this paper. For each user of the downlink MIMO-MSCMA, the transmitted codewords at different antennas come from different codebooks of MSCMA, respectively. On the other side, a novel basic complex multi-dimension constellation design is proposed in the MSCMA codebook design. Simulation results show that the bit error rate performance of the downlink MIMO-MSCMA outperforms than that of downlink MIMO-SCMA.