Low-to-Zero-Overhead IRS Reconfiguration: Decoupling Illumination and Channel Estimation

TL;DR

This paper introduces a low-overhead IRS reconfiguration method that decouples illumination from channel estimation by focusing on MU position, enabling efficient IRS optimization without full CSI, suitable for blockage scenarios.

Contribution

It proposes a novel IRS phase-shift design that estimates MU position instead of full CSI, reducing reconfiguration overhead and applicable in both near- and far-field regimes.

Findings

Zero overhead IRS reconfiguration in blockage scenarios.

A tunable IRS illumination area design.

Effective IRS optimization based on MU position estimation.

Abstract

Most algorithms developed so far for the optimization of Intelligent Reflecting Surfaces (IRSs) require knowledge of full Channel State Information (CSI). However, the resulting acquisition overhead constitutes a major bottleneck for the realization of IRS-assisted wireless systems in practice. In contrast, in this paper, focusing on downlink transmissions from a Base Station (BS) to a Mobile User (MU) that is located in a blockage region, we propose to optimize the IRS for illumination of the area centered around the MU. Hence, the proposed design requires the estimation of the MU's position and not the full CSI. For a given IRS phase-shift configuration, the end-to-end BS-IRS-MU channel can then be estimated using conventional channel estimation techniques. The IRS reconfiguration overhead for the proposed scheme depends on the MU mobility as well as how wide the coverage of the IRS illumination is. Therefore, we develop a general IRS phase-shift design, which is valid for both the near- and far-field regimes and features a parameter for tuning the size of the illumination area. Moreover, we study a special case where the IRS illuminates the entire blockage area, which implies that the IRS phase shifts do not change over time leading to zero overhead for IRS reconfiguration.