A Novel MAI Reduction Method Using Longer ...

In this paper, we consider the problem of Multiuser Detection (MUD) in Direct Sequence/Code Division Multiple Access (DS/CDMA) communication systems. The optimum detector for MUD is the Maximum Likelihood (ML) detector, but its complexity is very high and involves an exhaustive search to reach the best fitness of the transmitted and received data. Thus, there has been considerable interest in suboptimal multiuser detectors with less complexity and reasonable performance. If we look to the problem from an optimization viewpoint, what makes our work difficult is high interaction and Epistasis among variables which should be optimized. We propose to work on the problem and try to reduce its complexity instead of using more complex and powerful optimization algorithms. To do so, we analyze problem carefully and propose a new method to overcome Epistasis. In this paper, by using sign detector and longer code lengths in DS/CDMA system, a simple detector will be proposed. This method is compared with ML and two model-free optimization methods: Particle Swarm Optimization (PSO) and Ant Colony Optimization (ACO) algorithms which have been used for MUD in DS/CDMA. Simulation results show our method dramatic efficiency.