Low-complexity Hybrid Interference Cancellation for Sparse Code Multiple Access

Abstract Sparse code multiple access (SCMA) is one of Non Orthogonal Multiple Access (NOMA) candidate for 5G mobile communications. Multiple overlapped blocks of SCMA code are transmitted per frequency layer which compels the receiver to cancel unwanted SCMA code blocks. Thanks to the sparsity of SCMA, Message Passing Algorithm (MPA) achieves near-optimal performance. Nevertheless process is time-consuming and has a high degree of complexity even if Max-Log algorithm is used. In this paper we propose a Hybrid Interference Cancellation with Log Domain MPA algorithm (HIC-MPA) which uses either hard interference cancellation or soft interference cancellation following by a LDPC decoder. The choice of interference cancellation decoder depends on a threshold value based on power measurements. Results show a significant reduction in terms of complexity as compared to the traditional MPA process for the same values of Bit Error Rate (BER).