Multiple RIS Transmissions With Multihop Relaying for THz Wireless System

Existing research on multiple reconfigurable intel-ligent surfaces (RIS) assisted wireless systems suffers from the multiplicative channel effects. In this paper, we propose multiple RIS combined with multihop relaying (MRIS-MH) to enhance the performance of THz wireless communications. We develop exact analytical expressions for the density and distribution functions of the resultant signal-to-noise ratio (SNR) for the proposed MRIS- MH system by deriving statistical results of the double α- μ fading combined with the THz pointing error (TPE) and phase error. We analyze the exact and asymptotic expressions for the considered system's outage probability and average bit-error rate (BER) using the derived statistical results. The diversity order of the system is independent of phase error, depends on the channel fading parameters $a$ and μ, and depends on the $β$ parameter of the TPE. The proposed scheme illustrates that employing multihop relaying supports multiple RIS in extending the range of THz transmission.