# Message passing-based link configuration in short range millimeter wave systems

## TL;DR

This paper introduces a message passing framework for short-range millimeter wave systems that exploits channel structure to improve beam alignment with fewer measurements, addressing limitations of far-field assumptions.

## Contribution

A novel message passing-based method that models short-range mmWave channels by dividing them into subchannels, leveraging structure and antenna geometry for efficient beam alignment.

## Key findings

- Achieves better beam alignment with fewer measurements.
- Outperforms standard compressed sensing techniques.
- Effectively exploits channel structure across subchannels.

## Abstract

Millimeter wave (mmWave) communication in typical wearable and data center settings is short range. As the distance between the transmitter and the receiver in short range scenarios can be comparable to the length of the antenna arrays, the common far field approximation for the channel may not be applicable. As a result, dictionaries that result in a sparse channel representation in the far field setting may not be appropriate for short distances. In this paper, we develop a novel framework to exploit the structure in short range mmWave channels. The proposed method splits the channel into several subchannels for which the far field approximation can be applied. Then, the structure within and across different subchannels is leveraged using message passing. We show how information about the antenna array geometry can be used to design message passing factors that incorporate structure across successive subchannels. Simulation results indicate that our framework can be used to achieve better beam alignment with fewer channel measurements when compared to standard compressed sensing-based techniques that do not exploit structure across subchannels.