Online Path Optimization in Cascaded RIS Networks Via Mixed Integer Programming

Reconfigurable Intelligent Surfaces (RIS) have recently emerged as a key enabling technology for future 6 G networks, offering the capability to manipulate the wireless propagation environment intelligently. Here, we investigate the use of multiple RIS panels to establish Line-of-Sight (LOS) connectivity between a transmitter and a receiver via successive signal reflections. A core challenge lies in selecting the optimal RIS-assisted reflection path that maximizes end-to-end channel quality. To address this, we formulate the path selection problem as a Mixed-Integer Programming (MIP) optimization task, where the cost of each link depends on the selection of preceding links, introducing significant computational complexity. Simulation results demonstrate that the proposed scheme achieves near-optimal performance with minimal loss, validating its practical feasibility. Our results indicate minimal performance loss using Follow-The-Leader (FTL) and Follow-the-Perturbed-Leader (FTPL) schemes.