Performance Analysis of SCMA System Based on Polar Codes

Low latency and high reliability have become two major concerns in the design of future wireless networks. Non-orthogonal multiple access (NOMA) can achieve the high spectral efficiency and massive connectivity requirements for the fifth generation (5G) wireless networks, and the sparse code multiple access (SCMA) is the typical form of these techniques. Whats more, the NOMA has low transmission latency and signaling cost. In addition, the common characteristic of 5G URLLC networks is that the coding block length for wireless transmission are quite short due to the low latency constraint. In short block length, the Polar codes has performance advantage over the LDPC codes. In this paper, we propose an uplink Polar-coded SCMA system. The extrinsic information of successive cancellation list (SCL) decoder is calculated and be fed into the message passing algorithm (MPA) detector as prior information at the next outer-loop iteration. Furthermore, simulations are carried out for the block-error-rate performance evaluation of Polar-coded SCMA and LDPC-coded SCMA schemes. By comparing the performance and decoding complexity of these schemes, some promising are suggested.