Exact Analysis of RIS-Aided THz Wireless Systems Over α-μ Fading With Pointing Errors

Abstract

Reconfigurable intelligent surfaces (RIS) can have an excellent use case for terahertz (THz) wireless transmissions. In this letter, we analyze the performance of a RIS-empowered THz system over the combined effect of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> fading and pointing errors. We derive exact closed-form expressions of density and distribution functions of the resultant signal-to-noise ratio (SNR) considering an independent and not identically distributed (i.ni.d.) channel model. Using the derived statistical results, we present an exact analysis on outage probability, ergodic capacity, and average bit-error-rate (BER) of the considered system. We also develop asymptotic analysis on the outage probability and average BER to derive diversity order in terms of system parameters. The proposed analysis provides insights to mitigate the effect of pointing errors and shows that the RIS can significantly improve the performance of THz communications. We validate the analytical results using numerical and Monte Carlo simulations and demonstrate the scaling of system performance with an increase in the number of RIS elements.