Joint Beamforming and Interference Management for Active RIS-Assisted RSMA-ISAC Systems

초록

Integrated sensing and communication (ISAC) improves spectrum utilization by enabling joint sensing and communication functionalities, but its performance in multi-user scenarios is limited by severe path loss and multi-user interference. To address these challenges, this paper proposes an active reconfigurable intelligent surface (RIS)-assisted rate-splitting multiple access (RSMA)-ISAC system, where an active RIS is employed to mitigate reflection-link attenuation and RSMA is adopted at the dual-functional base station to manage multi-user interference. We formulate a coupled non-convex optimization problem to maximize the received-echo signal-to-noise ratio (SNR) by jointly optimizing the BS precoding, active RIS beamforming, and rate-splitting variables under communication quality-of-service and active RIS power constraints. To solve this problem, an alternating optimization algorithm is developed by reformulating the original problem into tractable convex subproblems, thereby reducing redundant iterations and ensuring efficient convergence. Simulation results show that the proposed system improves radar sensing performance while maintaining the user-rate requirements, and achieves superior radar SNR, detection probability, system sum rate, and energy efficiency compared with the passive RIS-assisted, spatial division multiple access (SDMA)-assisted, and non-orthogonal multiple access (NOMA)-assisted ISAC benchmarks.

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