PSO Assisted Multiuser Detection for DS-CDMA Communication Systems

In this chapter, a heuristic perspective for the multiuser detection problem in the uplink of direct sequence code division multiple access (DS-CDMA) systems is discussed. In particular, the particle swarm optimization multiuser detector (PSO-MuD) is analyzed regarding several figures of merit, such as symbol error rate, near-far and channel error estimation robustness, and computational complexity aspects. The PSO-MuD is extensively evaluated and characterized under different channel scenarios: additive white Gaussian noise (AWGN), single input single/multiple output (SISO/SIMO) flat Rayleigh, and frequency selective (multipath) Rayleigh channels. Although literature presents single-objective (SOO) and multi-objective optimization (MOO) approaches to deal with multiuser detection problem, in this chapter the single-objective optimization criterion is extensively used, since its application requirement is simpler than the MOO, and its performance results for the proposed optimization problem are quite satisfactory. Nevertheless, the MOO is shortly addressed as an alternative approach. Furthermore, the complexity × performance trade-off of the PSOMuD is carefully analyzed via Monte-Carlo simulation (MCS), and the complexity reduction concerning the optimum multiuser detector (MuD) is quantified. Simulation results show that, after convergence, the performance reached by the PSO-MuD is much better than the conventional detector (CD), and somewhat close to the single user bound (SuB), having computational complexity substantially lower than OMuD.