Performance Enhancement of MC–CDMA system through Evolutionary Programming algorithm based Turbo Multiuser detection

Multi carrier modulation (MCM) technique is essential for next generation wireless mobile communication system, which achieves high data rate with high spectral efficiency and high flexibility. Orthogonal Frequency Division multiplexing (OFDM) introduces multicarrier concept in Code Division Multiple Access (CDMA) to give rise to novel concept of MC-CDMA system. The OFDM mitigates multiple access interference (MAI) and inter symbol interference (ISI) effects and CDMA enlarge capacity and spreading gain. Advantages of this technique are its robustness in case of multipath propagation, improve security and minimize the ISI. Nevertheless, due to the poor orthogonality at the receiver in a mobile environment, MAI appears which severely degrades the reception quality. The turbo multiuser detection (MUD) emerged as a solution of overcome to MAI. The best performance is acquired by the turbo MUD with Evolutionary programming (EP). In this paper a novel modified Particle Swarm Optimisation (PSO) algorithm is proposed for MC-CDMA system based turbo MUD. The modified PSO algorithm has been combined with Turbo MUD to detect a feasible and efficient data bit by optimizing an objective function. The proposed modified PSO algorithm is efficient to search for the candidate list, and then produce the approximate a posteriori probability (APP) information. The complexity of the Turbo MUD can be reduced by the virtue of fast convergence of modified PSO. The modified PSO algorithm aided Turbo MUD scheme can provide a better BER performance than other Turbo MUD with a lower computational complexity.