Revisiting Beamforming Design for Stable Millimeter-Wave Communications Under Blockages

Abstract

This paper investigates robust analog beamforming for millimeter-wave (mmWave) communications under stochastic path blockages using multi-panel arrays. Conventional designs concentrate beams on the line-of-sight (LoS) path to maximize array gain, but this approach is highly vulnerable to sudden disconnections when the LoS path is blocked. To overcome this limitation, we propose a multi-beam design that exploits both LoS and non-line-of-sight (NLoS) paths for stable communications. The major contribution of this work is to establish a theoretical foundation for multi-beam design, where closed-form expressions for the cumulative distribution function (CDF) and outage probability of the spectral efficiency (SE) are derived. To design the optimal multi-beam based on the derived outage probability, we formulate a panel allocation problem to determine the assignment of panels to specific paths. The optimization problem can be solved by two algorithms based on brute-force search. Through computer simulations, the validity of the theoretical analysis for multi-beam design is confirmed, and the proposed algorithms substantially reduce the outage probability while maintaining average SE performance, thereby achieving stable communication.

This work has been submitted to the IEEE for possible publication