An Uplink SCMA Scheme Combined with Interleaving

SCMA is a novel, promising non-orthogonal multiple-access technique which adopts iterative detecting algorithms with affordable complexity. Current multiuser detection algorithms are mostly based on factor graph, which usually has a small number of variable nodes and function nodes and makes the girth of the factor graph small. Because the performance of an iterative detection algorithm based on factor graph is closely related to the minimum cycle length (girth) of the graph, we propose a novel uplink SCMA scheme where independent factor graphs corresponding to different SCMA blocks are connected together by using interleaving technique. Numerical results show the proposed scheme has a substantial gain over current detection algorithm over AWGN channels. Meanwhile, the diversity effect introduced by channel coefficients in different resource elements is also considered. The diversity effect combined with interleaving is analyzed. Simulation results demonstrate interleaving can affect BER performance under some circumstances related to channel coefficients diversity.