An Improved EPA-Based Receiver Design for Uplink LDPC Coded SCMA System

Sparse code multiple access (SCMA) is an emerging paradigm for efficient enabling of massive connectivity in future machine-type communications (MTC). In this letter, we conceive the uplink transmissions low-density parity check (LDPC) coded SCMA system. Traditional receiver design LDPC-SCMA system, which based on message passing algorithm (MPA) multiuser detection followed by individual LDPC decoding, may suffer from drawback high complexity and large decoding latency, especially when system has codebook size and/or overloading factor. To address problem, introduce a novel applying expectation propagation (EPA) to joint (JDD) involving aggregated factor graph sparse codebooks. Our numerical results demonstrate superiority proposed EPA JDD over conventional Turbo terms both significantly lower faster convergence rate without noticeable error performance degradation.