# Fast Accurate Beam and Channel Tracking for Two-dimensional Phased Antenna Arrays

## TL;DR

This paper develops fast, accurate 2D beam and channel tracking algorithms for mmWave systems with large phased arrays, reducing overhead and approaching theoretical limits, especially for dynamic channels.

## Contribution

It introduces novel tracking algorithms optimized for different channel dynamics that minimize exploration overhead and achieve near-optimal accuracy.

## Key findings

- Algorithms approach the Cramer-Rao lower bound for certain channels.
- Simulation shows improved tracking accuracy and speed.
- Efficient algorithms with low computational complexity.

## Abstract

The sparsity and the severe attenuation of millimeter-wave (mmWave) channel imply that highly directional communication is needed. The narrow beam produced by large array requires accurate alignment, which is difficult to achieve when serving fast-moving users. In this paper, we focus on accurate two-dimensional (2D) beam and channel tracking problem aiming at minimizing exploration overhead and tracking error. Using a typical frame structure with periodic exploration and communication, a proven minimum overhead of exploration is provided first. Then tracking algorithms are designed for three types of channels with different dynamic properties. It is proved that the algorithms for quasi-static channels and channels in Dynamic Case I are optimal in approaching the minimum Cramer-Rao lower bound (CRLB). The computational complexity of our algorithms is analyzed showing their efficiency, and simulation results verify their advantages in both tracking error and tracking speed.