Performance Analysis of Stacked Reconfigurable Intelligent Surfaces (RIS)-aided Wireless Communication Systems

Abstract

Stacked reconfigurable intelligent surfaces (RISs) extend conventional planar reconfigurable intelligent surfaces by exploiting multi-layer metasurface structures to provide additional electromagnetic degrees of freedom. This study investigates the theoretical performance of stacked RIS-aided wireless communication systems, where we show that under random phase control (RPC), the effective channel power follows an exponential distribution, while for practical discrete phase control (DPC), it can be characterized by Gamma-based approximation when the block coordinate ascent (BCA) optimization scheme is adopted. Based on the derived probability density and cumulative distribution functions, analytical and approximate expressions for the outage probability (OP) are obtained. The results demonstrate that SIM-aided transmission with BCA-based DPC significantly improves the overall system performance.