Beam Selection for Wideband Millimeter Wave MIMO Relying on Lens Antenna Arrays

Beamspace multi-input-multi-output (MIMO) relying on lens antenna arrays can significantly reduce the number of radio-frequency chains in millimeter-wave (mmWave) communication systems through beam selection. However, the beamforming gain is actually frequency-dependent in wideband mmWave MIMO systems. This phenomenon is called beam squint which will deteriorate the system's performance when traditional beam selection methods are used. To solve this problem, we propose a wideband beam selection method for mmWave MIMO systems relying on lens antenna arrays. First, we select one beam with the maximal energy averaged over the whole band for each user and then we sequentially select the beams that contribute the most to the sum-rate. The performance analysis of the proposed wideband beam selection method is also presented. Numerical results show that the proposed method achieves higher sum-rate and energy efficiency compared with its traditional counterparts.