# FALP: Fast beam alignment in mmWave systems with low-resolution phase shifters

## TL;DR

FALP introduces a rapid beam alignment method for mmWave systems using low-resolution phase shifters, significantly reducing training overhead and leveraging compressed sensing and Fourier transforms for efficient channel acquisition.

## Contribution

The paper presents a novel framework called FALP that enables fast beam alignment in mmWave systems with ultra-low power, low-resolution phase shifters, and establishes a new link to magnetic resonance imaging.

## Key findings

- FALP achieves faster beam alignment than exhaustive search methods.
- The CS matrix in FALP satisfies the restricted isometry property.
- FALP exploits FFT for efficient channel measurement processing.

## Abstract

Millimeter wave (mmWave) systems can enable high data rates if the link between the transmitting and receiving radios is configured properly. Fast configuration of mmWave links, however, is challenging due to the use of large antenna arrays and hardware constraints. For example, a large amount of training overhead is incurred by exhaustive search-based beam alignment in typical mmWave phased arrays. In this paper, we present a framework called FALP for Fast beam Alignment with Low-resolution Phase shifters. FALP uses an efficient set of antenna weight vectors to acquire channel measurements, and allows faster beam alignment when compared to exhaustive scan. The antenna weight vectors in FALP can be realized in ultra-low power phase shifters whose resolution can be as low as one-bit. From a compressed sensing (CS) perspective, the CS matrix designed in FALP satisfies the restricted isometry property and allows CS algorithms to exploit the fast Fourier transform. The proposed framework also establishes a new connection between channel acquisition in phased arrays and magnetic resonance imaging.