Sparse code multiple access (SCMA) is one of the non-orthogonal multiple access schemes to meet the demands of massive connection and high spectral efficiency in the 5G communications. Since the sparsity of the codebook, the message passing algorithm (MPA) can be utilised for multi-user detection. However, the high computational complexity of MPA hinders the practical application of SCMA. The extended Max-Log MPA (EML-MPA) and the channel-adaptive extended Max-Log MPA (CAD-EML-MPA) help to reduce the complexity of conventional Log-MPA with trellis representation. On this basis, the authors propose a dynamic trellis based MPA (DT-MPA) in this study. DT-MPA selects symbols dynamically according to a specific threshold in each iteration of MPA. The impact of the threshold on the complexity and convergence behaviour is analysed. Simulation results show that the DT-MPA with variable which is related to bit signal-to-noise can achieve better bit error rate performance and lower complexity than EML-MPA and CAD-EML-MPA.

中文翻译：

---

基于动态网格的稀疏码多址低复杂度接收机

稀疏码多址（SCMA）是非正交多址方案之一，可满足5G通信中大规模连接和高频谱效率的需求。由于密码本的稀疏性，因此可以将消息传递算法（MPA）用于多用户检测。但是，MPA的高计算复杂性阻碍了SCMA的实际应用。扩展的Max-Log MPA（EML-MPA）和通道自适应的扩展Max-Log MPA（CAD-EML-MPA）有助于降低具有网格表示形式的传统Log-MPA的复杂性。在此基础上，作者在本研究中提出了基于动态网格的MPA（DT-MPA）。DT-MPA根据特定阈值动态选择符号在每次MPA迭代中。分析了阈值对复杂性和收敛行为的影响。仿真结果表明DT-MPA具有可变性 与EML-MPA和CAD-EML-MPA相比，与比特信噪比有关的信号可以实现更好的误码率性能和更低的复杂度。