Intelligent Omni-Surfaces Aided Wireless Communications: Does the Reciprocity Hold?

TL;DR

This paper investigates whether channel reciprocity holds in intelligent omni-surfaces (IOS)-aided wireless communications, revealing angle-dependent electromagnetic responses that lead to beam non-reciprocity, supported by simulations and experiments.

Contribution

It introduces a physics-based channel model for IOS and analyzes the non-reciprocal behavior caused by angle-dependent responses, providing new insights into IOS channel characteristics.

Findings

Channel reciprocity does not hold in IOS-aided systems due to beam non-reciprocity.

The electromagnetic response of IOS elements depends on incident and departure angles.

Simulation and experimental results confirm the theoretical non-reciprocity analysis.

Abstract

Intelligent omni-surfaces (IOS) have attracted great attention recently due to its potential to achieve full-dimensional communications by simultaneously reflecting and refracting signals toward both sides of the surface. However, it still remains an open question whether the reciprocity holds between the uplink and downlink channels in the IOS-aided wireless communications. In this work, we first present a physics-compliant IOS related channel model, based on which the channel reciprocity is investigated. We then demonstrate the angle-dependent electromagnetic response of the IOS element in terms of both incident and departure angles. This serves as the key feature of IOS that drives our analytical results on beam non-reciprocity. Finally, simulation and experimental results are provided to verify our theoretical analyses.