A low-complexity SCMA detector for AWGN channel based on solving overdetermined systems of linear equations

Sparse code multiple access (SCMA) is one of proposed non-orthogonal multiple access schemes for Fifth generation (5G) wireless communication standard. Maximum likelihood (ML) algorithm for SCMA detection has very high complexity and can not be implemented in real-time applications. Message Passing Algorithm (MPA) has smaller complexity, but it is still high. In this paper, we propose a new SCMA detector for AWGN channel which complexity is smaller than that of simplified log-domain MPA. This algorithm is based on antipodal symmetry of codewords in codebooks. Because of this property decoding process is reduced to the solution of a small number of overdetermined systems of linear equations. The performance of the proposed algorithm is equivalent to Max-Log-MPA with 2-3 iterations. The implementation of the algorithm is well parallelized, calculations of inverse matrices are performed in advance and obtained results are stored in memory, i. e. operations with very high computational complexity need not be performed in real-time application.