Adaptive beam alignment method for millimeter-wave massive MIMO communication systems

To compensate the severe path loss of millimeter-wave channel, large-scale antenna arrays are required to provide beamforming gains for millimeter wave communication systems. Since the millimeter wave (mmWave) MIMO channel has strong directional selectivity, it is necessary for transmitter and receiver to perform beam alignment for obtaining maximum beamforming gains. In this paper, we first propose an adaptive beam alignment scheme. Based on the proposed scheme, adaptive hierarchical traversal beam search algorithm and adaptive hierarchical iterative beam search algorithm are proposed for beam alignment. Both of the algorithms adjust the training time adaptively by exploiting the beam detection algorithm to improve the success rate of beam alignment and reduce beam training overhead. Furthermore, in order to improve the transmission data rate and the beam alignment reliability of the system, maximum transmission data rate is adopted as the termination criterion of beam training. Simulation results show that the proposed algorithms have higher transmission data rate and beam alignment success rate compared with the existing beam search algorithms under both line-of-sight (LOS) and non-line-of-sight (NLOS) channels. Moreover, the proposed algorithms are more reliable to dynamic scenarios, especially the short distance between transmitter and receiver.