Increasing Capacity in MIMO Systems Using Reconfigurable Array Antennas

Reconfigurable antennas are capable of having several states of frequency response, polarization or radiation patterns. In order to benefit from this reconfigurability, we should choose the best state of antennas, regarding estimated values for communication channel. The main purpose of this work is to show capacity enhancement of a multi user multiple input multiple output (MU-MIMO) system by means of pattern reconfigurable antennas. Firstly, for a base station antenna array consisting of reconfigurable antenna elements and several single antenna users, an optimization problem is devised to find the best state in which system capacity is maximized. Afterwards, considering a 5×5 antenna array in the base station and 20 single antenna UEs, the achievable rate per UE versus SNR is obtained and plotted for non-reconfigurable to 5-state reconfigurable antenna elements. Based on these results, it is concluded that by means of reconfigurable antennas in the base station array, the achievable rate per user can be increased by 40% (0.045 bps/Hz) without beamforming and 5% (0.052 bps/Hz) with MRC beamforming.