A Low Complexity Reliability-Aware Based Expectation Propagation Algorithm for Uplink SCMA Systems

摘要

Sparse code multiple access (SCMA) is considered to be a promising technology of non-orthogonal multiple access (NOMA) for the fifth generation (5G) wireless communications. Due to the sparse property of the SCMA, the message passing algorithm (MPA) can be utilized at the receiver to realize quasi-maximum likelihood (QML) performance, but the MPA detector with exponential complexity is still difficult to implement in practice. To tackle the issue, the expectation propagation algorithm (EPA) has been proposed to achieve close-to-MPA detection performance, but it is still unsatisfactory in aspect of complexity. In this paper, we propose the reliability-aware based EPA (REPA) which predefines a posterior probability threshold for each variable node (VN) to avoid the inefficient computation of reliable nodes. Simulation results illustrate that the proposed REPA method achieves almost the same block error rate (BLER) performance as the conventional EPA with significantly reduced complexity.