SER and Outage Probability Analysis of Double RIS Assisted Wireless Communication System

Reconfigurable Intelligent Surface (RIS) can enhance the performance of wireless communication systems in scenarios where there is an obstruction in the direct Line-of-Sight between transceivers. In this paper, we propose a double RIS assisted wireless communication system with no direct link present between source and destination with first RIS (R1) near to the source, second RIS (R2) near to the destination, and both RIS will independently assist the communication between source and destination. The analysis includes moment generating function-based symbol error rate evaluation and the derivation of simplified closed-form expression for the outage probability (OP) in terms of the Q-function over Rician and Rayleigh fading channels. A fair comparative performance evaluation, considering an identical number of RIS elements in two systems, is conducted against a single RIS-assisted system with the RIS positioned midway between the source and destination. The analytical findings are corroborated through Monte Carlo simulations and an in-depth examination of the energy consumption gain reveals that the proposed double RIS-assisted system surpasses the single RIS-assisted system in terms of SER and OP while exhibiting lower energy requirements.