Aiming at the high complexity of codebook design of sparse code multiple access(SCMA),this paper proposed a design scheme for SCMA codebook in AWGN channels.Firstly,it designed the constellations for each resource block of all users.Secondly,it generated the corresponding constellations for each user by using the subset segmentation method of trellis coded modulation (TCM).Then,the generated constellations composed constellation matrix with the low density spreading sequence.Finally,constellation matrix was converted to users' codebook.The proposed scheme could maximize the minimum Euclidean distance of constellation points not only between the users,but also within one user.Simulation results demonstrate that the designed codebook based on the proposed method can improve the BER performance of system.The system also performs well even if under high overload.%针对稀疏码多址接入(SCMA)码本设计复杂度高的问题,提出了一种基于高斯信道下的码本设计方案,先设计每个资源块上所有用户的总星座图,然后利用网格编码调制(TCM)中的子集分割法生成各用户对应的星座,结合低密度扩频序列生成星座矩阵,最后由星座矩阵对应生成用户码本.该方案不仅保证了用户之间的星座点间最小欧氏距离最大化,同时保证了用户自身星座点间最小欧氏距离最大化.仿真结果表明,应用所设计的码本,系统的BER低,且在高过载率条件下系统性能也表现良好.
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