Beam Training of LoS-MIMO Systems Using Subarray-Based Beamforming in the Presence of Ground Reflection

This paper proposes a beam training algorithm for line-of-sight (LoS) multi-input and multi-output (MIMO) system with subarray-based beamforming functionality at both the transmitter (Tx) and receiver (Rx). In general, a conventional beam training algorithm is conducted to maximize the signal power of each pair of the Tx and Rx subarray. As a result, each pair of subarrays directs its beam towards each other. In LoS-MIMO regime, however, the selected beams are not always adequate to obtain better channel capacity due to its spatial correlation dependency on a distance among Tx and Rx. To address the issue, we suggest to utilize ground reflection paths according to the situation, and propose an efficient beam training algorithm to operate that concept in real situation without knowledge about the distance. The simulation results show that the proposed algorithm can obtain better channel capacity regardless of the distance among Tx and Rx.