Active Reconfigurable Intelligent Surface-Aided Terahertz Wireless Communications

TL;DR

The paper tackles THz wireless links where molecular absorption and beam misalignment cause severe path loss and RIS-induced multiplicative fading. It introduces active RIS with per-element amplification β and active noise to mitigate fading and develops an ergodic rate framework that accounts for path loss, absorption, and misalignment, via h_L = h_P h_A with h_P = \frac{c^2 \sqrt{G_a G_b}}{(4\pi f)^2 d_a d_b} and h_A = exp(-\kappa(f)(d_a+d_b)/2). A Gamma approximation for χ = (\sum_{m=1}^M |f_m||g_m|)^2 via moment matching yields the CDFs F_χ and F_γ and the ergodic capacity C_u = \frac{1}{\ln 2} \int_0^\infty \frac{1 - F_\gamma(s)}{1+s} ds. Numerical results validate the accuracy and show that active RIS can substantially improve THz link performance and coverage, supporting more reliable deployments in 6G networks.

Abstract

Terahertz (THz) communication is expected to be a key technology for future sixth-generation (6G) wireless networks. Furthermore, reconfigurable intelligent surfaces (RIS) have been proposed to modify the wireless propagation environment and enhance system performance. Given the sensitivity to blockages and limited coverage range, RIS is particularly promising for THz communications. Active RIS can overcome the multiplicative fading effect in RIS-aided communications. In this paper, we explore active RIS-assisted THz communications. We formulate the ergodic rate, considering factors associated with active RIS, including active noise and signal amplification, and THz signals, including molecular absorption and beam misalignment

Figures (1)

• Figure 1: System model of the active RIS-assisted THz communications.