基于因子图的SCMA和LDPC联合检测和译码

稀疏码分多址（SCMA）和低密度奇偶校验码（LDPC）是未来移动通信系统中重要的多用户接入和信道编码备选方案。针对SCMA多用户检测性能不理想的问题，该文提出了基于因子图的SCMA和LDPC联合检测和译码方案（JDD），利用LDPC译码的外信息辅助SCMA的多用户检测，仿真结果表明，JDD方案能够获得显著的SCMA检测和LDPC译码性能增益，并使得译码性能逼近理想的单用户传输系统。为了实现算法性能与复杂度之间的折中，该文还提出了基于Jacobi对数近似和消息阻尼（Damping）技术的低复杂度联合检测和译码方案（RC-JDD），仿真和复杂度分析结果表明RC-JDD方案能够在保证译码性能的同时显著降低算法复杂度。

A Factor Graph Based Joint Detection and Decoding Scheme for LDPC Coded SCMA System

Sparse code multiple access (SCMA) and low density parity check (LDPC) are the promising candidate multiple access and channel code technology for the future mobile communication systems. In order to enhance the multi-user detection performance of SCMA, a factor graph based joint detection and decoding (JDD) for SCMA and LDPC is proposed in this paper. In the proposed scheme, the multi-user detection of SCMA is aided by the extrinsic information of LDPC decoding. Simulation results show that the JDD scheme has obvious performance gains compared with traditional methods, and approximates to the performance of a single user transmission system. In order to trade off the performance and complexity, a reduced complexity joint detection and decoding (RC-JDD) scheme based on Jacobi logarithm approximation and message damping is proposed. The simulation and analysis results show that the JDD scheme has a much lower complexity with an acceptable performance.