Low Complexity Iterative Receiver Design for Sparse Code Multiple Access
Abstract: Sparse code multiple access (SCMA) is one of the most promising methods among all the non-orthogonal orthogonal multiple access techniques in the future 5G communication. Compared with some other non non-orthogonal orthogonal multiple access techniques, such as low density signatur signature, e, SCMA can achieve better performance due to the shaping gain of the SCMA code words. However, despite the sparsity of the code words, the decoding complexity of the current message passing algorithm utilized by SCMA is still prohibitively high. In this p paper, aper, by exploring the lattice structure of SCMA code words, we propose a low low-complexity complexity decoding algorithm based on list sphere decoding (LSD). The LSD avoids the exhaustive search for all possible hypotheses and only considers signal within a hypersphere. hypersphere As LSD can be viewed a depth depth-first first tree search algorithm, we further propose several methods to prune the redundancy redundancy-visited visited nodes in order to reduce the size of the search tree. Simulation results show that the proposed algorithm can reduce the decoding complexity substantially while the performance loss compared with the existing algorithm is negligible.