A novel evidence theory based row message passing algorithm for LDS systems

The low density signature (LDS) technique which is able to support massive connectivity with non-orthogonal low density signatures is a promising multiple access (MA) scheme in future 5G systems. We firstly examine the theory of evidence to illustrate the weakness of the update rule for the message passing algorithm in LDS detection process. The combination results against the common sense (RACS) deteriorate the performance of LDS systems with high order modulation schemes considerably. To reduce the occurrence of the RACS, we propose a novel row message passing (RMP) algorithm by gradually updating the a posteriori probability (APP) messages of all variable nodes in each iteration. Hence, the RMP algorithm benefits from the turbo-effect on the rows of indicator matrix which results in fast convergence with moderate complexity. Simulations prove the reduction of iteration times and the effectiveness of the RMP algorithm for LDS systems with high order modulation schemes.