A Fixed Low Complexity Message Pass Algorithm Detector for Up-Link SCMA System

Sparse code multiple access (SCMA) is a new modulation and non-orthogonal multiple access scheme for 5G systems, in which the coded bits are mapped to multi-dimensional sparse codewords, and the message passing algorithm (MPA) is employed to detect multi-user signals. However, the relative high computational complexity of MPA detection is still a big concern for practical implementation, even the sparse structure has already been employed. In this letter, a novel fixed low complexity detector for uplink SCMA system is proposed, based on partial marginalization (PM). Our analysis and simulation results show that, compared with the existing MPA detector, the implementation complexity of the new PM-based detector is reduced substantially, while the bit error ratio (BER) performance degrades unnoticeably (less than 0.3 dB).