THz-Band Near-Field RIS Channel Modeling for Linear Channel Estimation

TL;DR

This paper develops a comprehensive THz-band RIS channel model considering near-field effects, mutual coupling, and spatial correlation, and analyzes linear estimation techniques to improve accuracy in ultra-massive array scenarios.

Contribution

It introduces a novel THz-specific channel model incorporating absorption, near-field, and mutual coupling effects, and evaluates linear estimation performance with these factors.

Findings

Accounting for spatial correlation and mutual coupling improves estimation accuracy.

Near-field effects are significant for ultra-massive arrays and short-range scenarios.

The proposed model enhances physical realism and estimation precision.

Abstract

Reconfigurable intelligent surface (RIS)-aided terahertz (THz)-band communications are promising enablers for future wireless networks. However, array densification at high frequencies introduces significant challenges in accurate channel modeling and estimation, particularly with THz-specific fading, mutual coupling (MC), spatial correlation, and near-field effects. In this work, we model THz outdoor small-scale fading channels using the mixture gamma (MG) distribution, considering absorption losses, spherical wave propagation, MC, and spatial correlation across large base stations and RISs. We derive the distribution of the cascaded RIS-aided channel and investigate linear channel estimation techniques, analyzing the impact of various channel parameters. Numerical results based on precise THz parameters reveal that accounting for spatial correlation, MC, and near-field modeling substantially enhances estimation accuracy, especially in ultra-massive arrays and short-range scenarios. These results underscore the importance of incorporating these effects for precise, physically consistent channel modeling.