Performance Analysis of Multi-RIS-Assisted Dual-Hop THz Communication Systems

Abstract

This paper investigates the performance of a dual-hop terahertz (THz) communication system assisted by multiple reconfigurable intelligent surfaces (RISs). In the proposed system, multiple RISs are deployed to enhance the signal propagation in the THz band, and at the receiver end, the optimal RIS link is selected based on the maximum instantaneous signal-To-noise ratio (SNR). The THz-RIS channel is characterized using the generalized α-μ fading model, which effectively captures the small-scale fading behavior in THz environments. To evaluate system performance under practical impairments of the THz link, we derive the closed-form expressions for probability density function (PDF) and cumulative distribution function (CDF) of the end-To-end instantaneous SNR. Using these expressions, we further analyze key performance metrics, including outage probability (OP), average symbol error rate (ASER), and ergodic capacity (EC). To gain deeper insights, asymptotic analyses of OP and ASER are also performed in the high-SNR regime, revealing the achievable diversity gain of the system. Monte-Carlo simulations are performed to validate the analytical results and compare the proposed multi-RIS-Assisted system with benchmark configurations. The findings demonstrate that the use of multiple RISs significantly enhances the reliability and spectral efficiency of THz communication, making it a promising solution for next-generation wireless networks. © 2025 IEEE.