Active RIS-Assisted Integrated Sensing and Communication Systems: Joint Receive-Transmit Beamforming and Reflection Design

Active reconfigurable intelligent surface (RIS) acts as an enhancement of signal transmitted by the base station (BS) to overcome the effects of multiplicative fading and provide communication services for users. In this paper, we investigate an active RIS-assisted integrated sensing and communication (ISAC) system in which the BS senses the target in the presence of interference and establishes communication with multiple users assisted by the RIS. The optimization problem is formulated to jointly design the BS’s sensing transceiver beamforming, communication beamforming, and the RIS’s reflection coefficients to maximize the sensing SINR while satisfying the communication SINR requirements of users. An algorithm based on the ideas of quadratic transformation (QT), Karush-Kuhn-Tucker (KKT) conditions, semidefinite relaxation (SDR), and alternating optimization (AO) is designed to transform and solve the non-convex problem optimally. Simulation results verify the effectiveness and superiority of active RIS-assisted ISAC systems in improving sensing performance with communication SINR constraints.

I. Introduction

Integrated sensing and communication (ISAC) and reconfigurable intelligent surface (RIS) are two promising technologies with significant implications for future autonomous driving and the sixth generation (6G) wireless communication systems. ISAC technology allows communication and radar systems to share spectrum resources, offering high spectral efficiency and low costs, making it a potential technology for Vehicle-to-Everything (V2X) [1]. RIS is composed of many passive reflection elements that can dynamically adjust the phase of incident signals, establishing a reliable virtual link between the base station (BS) and users, making it a significant research hotspot.