Particle swarm optimisation with embedded/cascaded parallel update for cooperative transmit beamforming in multiuser multiple‐input multiple‐output systems

Abstract

The authors present a cooperative transmit beamforming (CTBF) technique for the uplink of multiuser multiple-input multiple-output (MIMO) systems. To maximise MIMO channel capacity, the proposed technique embeds a parallel update (PU) mechanism into the particle swarm optimisation (PSO) scheme to concurrently search and refine each user's CTBF weights at every iteration in the PSO, thus named the embedded PU/PSO. Moreover, a reduced complexity and yet effective scheme is also proposed, which cascades the conventional PSO with the PU mechanism, thus called the cascaded PU/PSO. Simulation results demonstrate that the proposed CTBF schemes overcome the bit-error-rate floor phenomenon problem at higher signal-to-noise ratios, which appears in the existing works, at the expense of moderately higher complexity if the cascaded PU/PSO is used.