Low Complexity MPA Detector Based on Sphere Decoding for SCMA

Abstract

Sparse code multiple access (SCMA) has been proposed to obtain high capacity and support massive connections. Due to the sparse feature of codewords, SCMA achieves low complexity multiuser detection by utilizing message passing algorithm (MPA). However, the complexity reduction of MPA is still a significant issue. In this letter, a novel MPA based on sphere decoding, called SD-MPA, is proposed, which narrows down the range of believable superposed constellation points. Furthermore, simulation results show that SD-MPA detector can reach low complexity detection and maintain negligible bit error ratio performance decline compared with conventional MPA.