Optimal Beamforming Design for ISAC with Sensor-Aided Active RIS

TL;DR

This paper introduces a sensor-aided active RIS to enhance ISAC system performance, especially when the LoS link is blocked, by optimizing beamforming to improve sensing and communication quality.

Contribution

It proposes a novel sensor-aided active RIS framework with a closed-form receive beamforming solution and an iterative method for transmit and reflection beamforming design.

Findings

Sensor-aided active RIS significantly improves sensing performance.

The proposed optimization method outperforms non-sensor-aided systems.

Simulation results validate the effectiveness of the proposed system.

Abstract

Active reconfigurable intelligent surfaces (RISs) can improve the performance of integrated sensing and communication (ISAC), and therefore enable simultaneous data transmission and target sensing. However, when the line-of-sight (LoS) link between the base station and the sensing target is blocked, the sensing signals suffer from severe path loss, resulting in an inferior sensing performance. To address this issue, this paper employs a sensor-aided active RIS to enhance ISAC system performance. The goal is to maximize the signal-to-noise ratio of the echo signal from the target at the sensor-array while meeting constraints on communication signal quality, power budgets, and RIS amplification limits. The optimization problem is challenging due to its non-convex nature and the coupling between the optimization variables. We propose a closed-form solution for receive beamforming, and a successive convex approximation based iterative method for transmit and reflection beamforming design. Simulation results demonstrate the advantage of the proposed sensor-aided active RIS-assisted system model over its non-sensor-aided counterpart.