Irregular SCMA Codebook Design Approaches

The recent scenario for 5G communication demands major rise in user connectivity. To address this issue 5G communication makes use of sparse code multiple access (SCMA) techniques with multi-user-detection. SCMA employs codebook design techniques to enhance the performance parameters which in turn improve the multi user detection. Due to dynamic requirements of the users in 5G a modified version of SCMA: Irregular SCMA is proposed serve dynamic business requirements of the users. This method enforces codebook design with non-uniform degree distribution for the factor matrix. The degree distribution is a matrix that explains the interconnectivity between the users and the resources. To satisfy the performance requirements of a communication system, Irregular SCMA: with non-uniform degree distribution proves to be an optimal solution. The number of codebooks assigned to each user is also non-uniform. For better spreading gain with multi-user connectivity the number of non-zero elements can be increased, whereas for improved connectivity, in case of small packets the number of non-zero elements in the factor matrix is decreased. This article aims at explaining different methods used to design the codebook for Irregular SCMA with its decoding techniques. Considering these methods, an optimal codebook design of irregular SCMA is proposed in this article that yields a better symbol error rate for higher values of SNR.