A two-stage particle swarm optimization based cooperative transmit beamforming for multiuser MIMO systems

In this paper, we present a simple, yet effective two-stage particle swarm optimization (PSO) based cooperative transmit beamforming (CTBF) scheme for the uplink of multiuser multiple-input multiple-output (MIMO) systems. The proposed scheme first uses the conventional PSO method to iteratively update the CTBF for the maximization of system capacity. After that, the proposed scheme conducts the second stage´s PSO mechanism to find the final results of the CTBF. Especially, for the initialization of the second stage´s PSO, the proposed scheme remains the results of the global best CTBF found in the first stage´s PSO unchanged. In addition, other settings such as each particle´s velocity are reset to the initial values of the first stage´s PSO. The proposed scheme adopts this reset step in the second stage in order to avoid the CTBF updates of the PSO to trap into the local solutions. Simulation results show that the proposed new two-stage PSO scheme provides better bit error rate (BER) performance than the previous works.