A Stochastic Optimization Framework for RIS-Aided Wireless Network Design
This work addresses the challenge of rapidly escalating computational complexity in large-scale non-convex reconfigurable intelligent surface (RIS) configuration optimization, which intensifies with the number of scattering elements and architectural intricacy. To tackle this, the paper proposes a stochastic optimization framework that integrates continuous cross-entropy (CE) methods with Metropolis–Hastings (MH) sampling. The approach operates directly on continuous variables and incorporates relaxation and projection mechanisms to accommodate discrete RIS configurations, making it applicable to both nearly passive and active RIS architectures for optimizing spectral efficiency and energy efficiency. As the first systematic application of continuous stochastic optimization to RIS network design, the proposed method transcends the limitations of conventional discrete optimization, offering theoretical guarantees on convergence and computational efficiency. In representative scenarios, it achieves performance comparable to or better than state-of-the-art deterministic algorithms while reducing runtime by up to an order of magnitude.