Targeting the requirements of 6G, this paper investigates a semi-passive dual-reconfigurable intelligent surface (RIS)-assisted integrated sensing and communication (ISAC) system, tackling the max-min user signal-to-interference-plus-noise ratio (SINR) problem via joint active and passive beamforming to enhance system performance and ensure user fairness. Addressing this challenge, we first utilize dual RISs for user angle estimation to simplify the solution process of the formulated problem, an efficient alternating optimization algorithm is then developed. Specifically, semi-definite relaxation and the bisection method are employed to solve the transmit beamforming optimization subproblem. For the RIS discrete phase shifts, a sensing-assisted approach is adopted to constrain the optimization search space, with two distinct low-complexity search strategies introduced for different RIS sizes. Numerical simulation results demonstrate that the proposed algorithm achieves performance close to the ideal continuous phase shift benchmark, outperforms conventional discrete phase shift optimization algorithms, and exhibits a significant improvement over single-RIS systems.

翻译：针对6G通信需求，本文研究了一种半被动双可重构智能表面辅助的集成感知与通信系统，通过联合主动与被动波束成形解决最大-最小用户信干噪比问题，以提升系统性能并保障用户公平性。针对该挑战，我们首先利用双RIS进行用户角度估计以简化所构建问题的求解过程，随后提出一种高效的交替优化算法。具体而言，采用半定松弛与二分法求解发射波束成形优化子问题；对于RIS离散相位偏移，采用感知辅助方法约束优化搜索空间，并针对不同RIS尺寸引入两种低复杂度搜索策略。数值仿真结果表明，所提算法性能接近理想连续相位偏移基准，优于传统离散相位偏移优化算法，且较单RIS系统展现出显著性能提升。