Hybrid Precoding for Physical Layer Multicasting

TL;DR

This paper proposes a hybrid precoding scheme for physical layer multicasting that efficiently maximizes the minimum user SNR under RF hardware constraints, with algorithms and conditions ensuring near-optimal performance.

Contribution

It introduces a low complexity hybrid precoding algorithm and identifies conditions where limited RF chains do not compromise optimality.

Findings

The proposed algorithm achieves near-optimal max-min SNR performance.

A simple condition guarantees no loss of optimality with limited RF chains.

Numerical results validate the effectiveness of the hybrid precoding approach.

Abstract

This work investigates the problem of downlink transmit precoding for physical layer multicasting with a limited number of radio-frequency (RF) chains. To tackle the RF hardware constraint, we consider a hybrid precoder that is partitioned into a high-dimensional RF precoder and a low-dimensional baseband precoder. Considering a total transmit power constraint over the RF chains, the goal is to maximize the minimum (max-min) received signal-to-noise ratio (SNR) among all users. We propose a low complexity algorithm to compute the RF precoder that achieves near-optimal max-min performance. Moreover, we derive a simple condition under which the hybrid precoding driven by a limited number of RF chains incurs no loss of optimality with respect to the fully digital precoding case. Finally, numerical results validate the effectiveness of the proposed algorithm and theoretical findings.