Beamforming algorithms for multiuser MIMO uplink systems: Parallel and serial approaches

Joint transmitter and receiver beamforming algorithms for uplink multiuser multi-input multi-output (MIMO) communication systems are proposed in this paper based on maximizing an utility function, which is defined based on the difference between desired signal power and interference plus noise power. Two iterative beamforming algorithms are developed by maximizing the utility function of each user via parallel and serial methods. In parallel method, the transmitter and receiver beamforming vectors of each user are iteratively updated by maximizing its utility function. However in serial method, at first step, the transmitter beamforming vectors of all users are iteratively updated by maximizing the utility function of each user and then receiver beamforming vectors of users are calculated. By computer simulations, the performances of the proposed beamforming algorithms are evaluated and also compared with the performance of the duality method (DM) based beamforming algorithm. With respect to bit error rate (BER) and convergence rate, the results show that the new proposed beamforming algorithms have superior performances in comparison with the DM based beamforming algorithm. Also, for some cases, the serial method achieves better performances in comparison with the parallel method.