Beamforming in Integrated Sensing and Communication Systems with Reconfigurable Intelligent Surfaces

TL;DR

This paper explores beamforming and reflection pattern design in RIS-assisted integrated sensing and communication systems, optimizing for user SINR and radar illumination, with two configurations using one or two RISs.

Contribution

It introduces novel beamforming algorithms for RIS-assisted ISAC systems with single and dual RIS setups, enhancing communication and radar performance.

Findings

Single-RIS system improves minimum user SINR with moderate radar power loss.

Dual-RIS system enhances both user SINR and radar illumination, especially with non-visible targets.

Proposes alternating optimization algorithms for non-convex design problems.

Abstract

We consider transmit beamforming and reflection pattern design in reconfigurable intelligent surface (RIS)-assisted integrated sensing and communication (ISAC) systems to jointly precode communication symbols and radar waveforms. We treat two settings of multiple users and targets. In the first, we use a single RIS to enhance the communication performance of the ISAC system and design beams with good cross-correlation properties to match a desired beam pattern while guaranteeing a desired signal-to-interference plus noise ratio (SINR) for each user. In the second setting, we use two dedicated RISs to aid the ISAC system, wherein the beams are designed to maximize the worst-case target illumination power while guaranteeing a desired SINR for each user. We propose solvers based on alternating optimization as the design problems in both cases are non-convex optimization problems. Through a number of numerical simulations, we demonstrate the advantages of RIS-assisted ISAC systems. In particular, we show that the proposed single-RIS assisted ISAC system improves the minimum user SINR while suffering from a moderate loss in radar target illumination power. On the other hand, the dual-RIS assisted ISAC system improves both minimum user SINR as well as worst-case target illumination power at the targets, especially when the users and targets are not directly visible.