中文摘要：

稀疏码多址接入（SCMA）是一种码域非正交多址接入技术,以其优异性能成为5G多址接入技术的热门候选方案。上行SCMA系统一般采用消息传递算法（MPA）接收机,检测过程中存在由先验信息带来的误差。针对这一问题提出一种新型接收机,称为环MPA（R-MPA）接收机,其通过一种联合检测方案来消除上述误差对最终检测结果的影响。理论分析和仿真验证表明,与现有的log-MPA接收机及经典MPA接收机相比,所提R-MPA接收机是一种检测精度更高而实施复杂度较低的上行SCMA系统接收机。

英文摘要：

Sparse code multiple access（SCMA） is a type of code domain non-orthogonal multiple access technology, which is regarded as a promising multiple access technology for 5G due to its excellent performance. The uplink SCMA system generally uses a message passing algorithm（MPA） in the receiver. The priori information can be inaccurated to cause an increased detection error. A novel receiver for the uplink SCMA system, called ring-MPA（R-MPA） receiver, was proposed to solve this problem, by using a joint detection process. The proposed R-MPA receiver was compared with the log-MPA receiver and the classic MPA receiver, two state-of-the-art existing schemes. Both theoretical analysis and computer simulation results show that the proposed receiver not only has a superior error performance, but also has a lower implementation complexity than these existing schemes.