Practical Multi-Panel Beam Selection for Higher Rank LoS-MIMO with Joint Phase-Time Array

This paper proposes a practical multi-panel beam selection for higher rank line-of-sight (LoS) multiple input multiple output (MIMO) with joint phase-time array (JPTA). In multi-panel millimeter wave (mmWave) LoS-MIMO, spatial correlation varies significantly depending on the link distance between the transmitter (TX) and receiver (RX). Therefore, if a beam aligned with the LoS path is consistently selected across all panels, it can lead to a significant degradation in channel capacity (CC). To alleviate this issue, we have proposed a per-panel beamforming scheme that selects beams directing towards reflective paths at some panels, while the remaining panels select the direction of the direct path. However, it takes larger training overhead (OH) since beam switching is required to calculate the CC for possible beam pairs of panels. Our proposed solution in this paper involves leveraging JPTA that can form frequency dependent beam, a set of multiple beams for each frequency subband, in one orthogonal frequency division multiplexing (OFDM) symbol, leading to reduction of the training OH. Furthermore, a practical beam selection algorithm for each panel with JPTA is concretized for operating in 3GPP compliant systems with taking its reference signals, beam measurement reports and frame structure into account for the first time. The effectiveness of the proposed method is demonstrated through computer simulations, which show that the beam training (BT) algorithm utilizing JPTA can achieve high CC performance while significantly reducing the training OH.