THz Channel Characteristics and Path Loss Modeling for IRS-Assisted Communication Systems

The terahertz (THz) band offers tremendous potential for next-generation wireless communication systems, but its unique propagation characteristics pose significant modeling challenges. This paper investigates the fundamental behaviors of the THz channel and provides a comprehensive study on path loss modeling with a focus on frequency-selective molecular absorption effects. We first examine unique features of THz signal propagation, including spectral windows and frequency/distance-dependent absorption behavior. Several empirical path loss models are reviewed, followed by the introduction of data-driven molecular absorption models that more accurately capture THz band attenuation. Furthermore, we analyze the path loss of the signal propagated through the reflection of the intelligent reflecting surface (IRS) under different scenarios, revealing the dependence of path loss on transmission distance and operating frequency. This work offers a foundational perspective for understanding and modeling the path loss in IRS-assisted THz communications.