Multi-BS Cooperative and Coordinated ISAC Mechanism With Assistance of STAR-RIS

Multi-node ISAC mechanisms are promising to improve sensing performance by overcoming the limited sensing capabilities of a single ISAC node. STAR-RIS can help expand sensing coverage while assisting in communication by dividing incident signals into refracted and reflected spaces surrounding the surfaces. This paper proposes a STAR-RIS-assisted multi-base station (SRMB) ISAC mechanism. Available sensing and communication links are established with the help of STAR-RISs. The collaboration and interference across multiple ISAC BSs remain to be balanced in the SRMB ISAC mechanism. As a result, this paper jointly optimizes the active and passive beamforming of BSs and STAR-RISs to maximize the minimal sensing performance of ISAC BSs, while satisfying communication performance and transmission power constraints. The alternating optimization method and semi-definite relaxation technique are adopted to solve the non-convex optimization problem. Simulation results indicate that the proposed SRMB ISAC mechanism outperforms benchmark RIS-assisted multi-BS ISAC mechanisms in enhancing sensing performance while ensuring communication performance by effectively coordinating cooperation and interference among ISAC BSs.