A Novel Sample Selection based Detection Algorithm for Asynchronous SCMA Systems

As a promising contender within non-orthogonal multiple access (NOMA), sparse code multiple access (SCMA) stands out as a potential cornerstone in future-generation wireless communication systems. However, while most SCMA research assumes ideal synchronization among multiple users, the reality of non-ideal synchronization introduces multi-user access inter-ference (MAI), leading to significant performance degradation. In fact, this interference can be severe enough to cause traditional SCMA detection methods to falter in convergence. This paper delves into the theoretical analysis of MAI and introduces an innovative solution: a sample selection-based message passing algorithm (SS-MPA). The aim is to tackle this issue head-on. Through error rate performance simulations and complex-ity evaluations, our results showcase that the proposed SS-MPA algorithm, designed for asynchronous conditions, closely approaches the optimal performance of MPA in synchronous settings, all while maintaining comparable complexity levels. This breakthrough marks a significant step toward resolving MAI-related challenges in SCMA systems.