Novel LoS $\beta-\gamma$ THz Channel Unifying Molecular Re-radiation Manifestations

TL;DR

This paper develops a comprehensive LoS $eta-\gamma$ THz channel model incorporating molecular re-radiation effects, providing new analytical tools for system design and demonstrating improved SER performance with optimal detection.

Contribution

It introduces a novel physical channel model for THz communications that includes molecular re-radiation and derives new ML-based detection thresholds with accurate SER expressions.

Findings

The $eta-\gamma$ model accurately reflects physical THz channel behavior.

Analytical SER closely matches simulated results under optimal detection.

Maximum molecular re-radiation reduces SER compared to suboptimal detectors.

Abstract

This paper introduces a novel line-of-sight (LoS) $\beta-\gamma$ terahertz (THz) channel model that closely mirrors physical reality by considering radiation trapping. Our channel model provides an exhaustive modeling of the physical phenomena including the amount of re-radiation available at the receiver, parametrized by $\beta$, and the balance between scattering and noise contributions, parametrized by $\gamma$, respectively. Our findings indicate a nontrivial relationship between average limiting received signal-to-noise ratio (SNR) and distance emphasizing the significance of $\gamma$ in THz system design. We further propose new maximum likelihood (ML) thresholds for pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) schemes, resulting in analytical symbol error rate (SER) expressions that account for different noise variances across constellation points. The results confirm that the analytical SER closely matches the true simulated SER when using an optimal detector. As expected, under maximum molecular re-radiation, the true SER is shown to be lower than that produced by a suboptimal detector that assumes equal noise variances.