基于低密度叠加编码调制的新型上行非正交多址接入方案

A Novel Low Density Superposition Modulation Scheme for Uplink NOMA

稀疏码分多址接入（SCMA）方案映射矩阵维度太小时,短环和规则度分布的SCMA映射矩阵与存在远近效应的环境不能很好地匹配,为此,提出一种新型的非正交多址接入方案——低密度叠加编码调制（LDSM）.该方案设计了更加稀疏的非规则度分布映射矩阵,带来分集增益和编码增益,提高整体方案性能的同时,对边缘用户的性能也有所提高.在独立瑞利衰落信道下,通过平均互信息的分析,从理论上证明了LDSM方案较SCMA方案有一定的信噪比增益.仿真结果证明,在远近功率差为10 d B,过载为150%时,小规模的LDSM方案和大规模LDSM方案较SCMA方案的整体用户性能分别能获得2.3 d B和2.46 d B的增益.

There may exist short cycles if the matrix dimensions of sparse code multiple access（SCMA）are small,and the regular mapping matrix of SCMA doesn ＇t take near-far effect into consideration.Therefore,a novel uplink non-orthogonal multiple access scheme named low density superposition modulation（LDSM） scheme is proposed to construct a sparser and irregular mapping matrix. The proposed scheme can improve the overall performance and the edge users＇ performance for it can get diversity gain and coding gain. The analysis of the average mutual information demonstrates LDSM can get signal to noise ratio（SNR） gains over SCMA in theory. Simulation results show that when power difference is10 d B and overloading is 150%,small dimensional and large dimensional LDSM can get 2. 3 d B and2. 46 d B SNR gains over SCMA for overall performance. Both theoretic analysis and simulation results prove the performance of LDSM outperforms that of SCMA.