SCMA Codebook Design
SCMA Codebook Design
复制标题
DOI：
10.1109/vtcfall.2014.6966170
复制
发表时间：
2014-08
期刊：
影响因子：
--
通讯作者：
M. Taherzadeh;Hosein Nikopour;A. Bayesteh;H. Baligh
中科院分区：
文献类型：
--
作者：
M. Taherzadeh;Hosein Nikopour;A. Bayesteh;H. Baligh
多载波CDMA是一种多址方案，其中调制的QAM符号通过使用一般复杂的传播序列在OFDMA音调上传播。实际上，QAM符号在多个音调中重复。低密度签名（LDS）是具有低密度扩展序列的CDMA版本，允许我们利用具有实际可行复杂性的近最优消息传递算法（MPA）接收器。稀疏码多址(SCMA)是一种基于多维码本的非正交扩展技术。在SCMA中，将比特到QAM的符号映射和扩展过程结合在一起，将输入的比特直接映射到SCMA码本集的多维码字中。每一层都有自己的专用密码本。与LDS中QAM符号的简单重复相比，多维星座的整形增益是性能提高的主要来源之一。同时，由于码字的稀疏性，SCMA与LDS一样具有低复杂度的接收技术。本文提出了一种系统的基于格子星座设计原理的SCMA码本设计方法。仿真结果显示了SCMA相对于LDS和OFDMA的性能增益。
Multicarrier CDMA is a multiple access scheme in which modulated QAM symbols are spread over OFDMA tones by using a generally complex spreading sequence. Effectively, a QAM symbol is repeated over multiple tones. Low density signature (LDS) is a version of CDMA with low density spreading sequences allowing us to take advantage of a near optimal message passing algorithm (MPA) receiver with practically feasible complexity. Sparse code multiple access (SCMA) is a multi-dimensional codebook-based non-orthogonal spreading technique. In SCMA, the procedure of bit to QAM symbol mapping and spreading are combined together and incoming bits are directly mapped to multi-dimensional codewords of SCMA codebook sets. Each layer has its dedicated codebook. Shaping gain of a multi-dimensional constellation is one of the main sources of the performance improvement in comparison to the simple repetition of QAM symbols in LDS. Meanwhile, like LDS, SCMA enjoys the low complexity reception techniques due to the sparsity of SCMA codewords. In this paper a systematic approach is proposed to design SCMA codebooks mainly based on the design principles of lattice constellations. Simulation results are presented to show the performance gain of SCMA compared to LDS and OFDMA.