CALO: Constraint-Aware Learning Optimization for Joint Resource Allocation in Double-Active RIS-Assisted Wireless Networks

Alaa S. Arabiyat, Mohammad J. Abdel-Rahman

Double-active reconfigurable intelligent surface (RIS)-assisted wireless systems can improve coverage and achievable rate in blockage-dominated environments. Still, their joint resource allocation is challenging due to the coupling among RIS placement, amplification power allocation, and reflecting-element assignment. The resulting problem is linearly constrained, non-convex, and involves both continuous and discrete variables, making conventional iterative solvers such as block coordinate descent (BCD) computationally expensive for real-time deployment. This paper proposes a \underline{c}onstraint-\underline{a}ware \underline{l}earning \underline{o}ptimization (CALO) framework for data-driven joint resource allocation in double-active RIS-assisted networks. CALO reformulates the decision variables into grouped fractional representations and maps them to physical resources through constraint-preserving transformations, ensuring that distance, power, and element-budget constraints are satisfied by construction. A straight-through estimator is incorporated to enable differentiable learning over discrete reflecting-element assignments, while a regret-driven hinge objective uses the BCD solution as a reference and encourages performance improvement beyond solver imitation. Simulation results show that CALO achieves $100\%$ feasibility across all tested configurations, improves the achievable rate over BCD in both urban and rural scenarios, and reduces online inference time by orders of magnitude. These results demonstrate the effectiveness of structure-aware learning for feasible and real-time optimization in active multi-RIS wireless systems.