PERFORMANCE ANALYSIS OF CASCADED RIS-BASED COMMUNICATIONS

Abstract

This thesis presents a comprehensive performance analysis of cascaded Reconfigurable Intelligent Surface (RIS)-aided communication systems under Nakagami-m fading. It consider a multi-hop (cascaded) RIS architecture, where multiple RIS layers are deployed in series, and incorporate a practical phase shift model that captures the dependency of each reflecting element’s amplitude response on its phase adjustment. The aim of this paper is to derive exact analytical expressions for the end-to-end signal-to-noise ratio (SNR) distribution and use them to obtain closed-form formulas for the outage probability (OP) and ergodic capacity (EC) of the cascaded RIS system. To handle the products of multiple fading coefficients and phase responses, the derivations leverage advanced analytical tools such as the Fox H-function and moment-generating function (MGF) methods, yielding tractable expressions for these performance metrics. Monte Carlo simulations validate the accuracy of the derived results across various system configurations. The results demonstrate that imperfect phase alignment due to practical hardware introduces performance degradation compared to the ideal case. Nevertheless, increasing the number of RIS layers and reflecting elements significantly improves SNR, resulting in lower OP and higher EC. These findings highlight the trade-offs between RIS network density (number of layers/elements) and achievable performance under practical phase shift limitations, providing valuable design insights for future beyond 5G (B5G) and sixth generation (6G) cellular networks and cascaded RIS-based wireless networks.