A Novel Codebook Design Scheme for Sparse Code Multiple Access

The sparse code multiple access (SCMA) technology proposed by Huawei has become a very competitive one of many NOMA solutions due to its high overload capability. SCMA maps the user’s binary bit data input by the system’s sending end into a multi-dimensional complex number sequence through a pre-designed codebook, instead of the modulation and spreading in the orthogonal multiple access scheme. Based on the sparsity of codewords, the receiving end uses the Message Passing Algorithm (MPA) for multi-user detection. Among them, the excellent SCMA codebook can effectively improve the performance of the system under limited spectrum resources. Therefore, this paper conducts detailed research on the SCMA codebook design scheme. First, this article introduces the principle of the SCMA system in detail, and then proposes a SCMA codebook design method, including the design of the mapping matrix, the design of the mother constellation and the constellation operator. Among them, the mother constellation design adopts a reorganized multi-dimensional constellation scheme. The constellation operator obtains the user constellations of different users through phase rotation, and then maps the designed user constellations into a codebook through a mapping matrix. The simulation results show that the performance of this design is better than the sample codebook given by Huawei.