Beyond conventional wireless: exact closed-form insights into IRS-aided dual-hop systems over MFTR-Rayleigh channels

This paper presents an accurate closed-form approximation for the end-to-end SNR of dual-hop Intelligent Reflecting Surface (IRS)-assisted wireless communication systems. Unlike prior studies, the proposed framework remains accurate for both small and large numbers of IRS elements, addressing a critical gap in performance modelling. The analysis considers a multi-cluster fluctuating two-ray (MFTR) fading model for the IRS-to-receiver link and Rayleigh fading for the BS-to-IRS link, ensuring applicability to conventional, non-conventional, and Terahertz communication environments. Closed-form expressions for outage probability (OP), bit error rate (BER), and average channel capacity (ACC) are derived, providing comprehensive insights into system performance under diverse fading conditions. Results show nearly a 50% reduction in transmit power to achieve the same BER as a non-IRS system. Extensive Monte Carlo simulations validate the analytical expressions, offering a reliable benchmark for evaluating IRS-aided networks. This work establishes an analytical foundation for optimized IRS deployment and next-generation wireless system design.