Hardware Design and Implementation of Sparse Code Multiple Access

Sparse code multiple access (SCMA) has recently emerged as one of the most favorable multiple access schemes for 5G networks, which allows overloading with a large number of users so as to enable massive connectivity. In this paper, we design a hardware framework of a uplink system for SCMA. First, we propose a unified quantization scheme based on density evolution optimization which is independent of signal-to-noise ratios (SNR). Second, we apply a fast convergence message passing algorithm (FC-MPA) in SCMA multiuser detection, in which the function nodes updating and variable nodes updating are processed synchronously so as to make the FC-MPA converge about 2 times faster than standard MPA. Finally, based on FC- MPA, we design a pipelined decoding structure for SCMA so as to increase throughput. FPGA results demonstrate that the fix- point performance achieve a near floating-point performance for different SNR and the pipelined hardware structure we design is feasible.