Beam Alignment Using Trajectory Information in Mobile Millimeter-wave Networks

TL;DR

This paper proposes a trajectory-based beam alignment method for mobile millimeter-wave networks that reduces overhead and improves SNR by optimizing region division based on device movement.

Contribution

It introduces an optimization framework for dividing user trajectories into regions to minimize beam search overhead while maintaining high SNR in mobile mmWave systems.

Findings

High SNR achieved with fewer regions.

More robust to location inaccuracies than baselines.

Outperforms lookup table and fixed region methods.

Abstract

Millimeter-wave and terahertz systems rely on beamforming/combining codebooks to determine the best beam directions during the initial access and data transmission. Existing approaches suffer from large codebook sizes and high beam searching overhead in the presence of mobile devices. To address this issue, we utilize the similarity of the channel in adjacent locations to divide the user trajectory into a set of separate regions and maintain a set of candidate beams for each region in a database. Due to the tradeoff between the number of regions and the signalling overhead, i.e., the greater number of regions results in a higher signal-to-noise ratio (SNR) but also a larger signalling overhead for the database, we propose an optimization framework to find the minimum number of regions based on the trajectory of a mobile device. Using a ray tracing tool, we demonstrate that the proposed method provides high SNR while being more robust to the location information accuracy in comparison to the lookup table baseline and fixed size region baseline.