SWIPT with Intelligent Reflecting Surfaces under Spatial Correlation

TL;DR

This paper investigates how spatial correlation among IRS elements affects simultaneous wireless information and power transfer, deriving analytical expressions and analyzing performance under different correlation scenarios.

Contribution

It provides the first analytical framework for evaluating IRS performance with spatial correlation in SWIPT systems, including optimal correlation cases.

Findings

Correlation improves energy transfer performance.

Uncorrelated elements with random phases have similar performance to equal phases.

Correlation degrades information transfer under certain configurations.

Abstract

Intelligent reflecting surfaces (IRSs) can be beneficial to both information and energy transfer, due to the gains achieved by their multiple elements. In this work, we deal with the impact of spatial correlation between the IRS elements, in the context of simultaneous wireless information and power transfer. The performance is evaluated in terms of the average harvested energy and the outage probability for random and equal phase shifts. Closed-form analytical expressions for both metrics under spatial correlation are derived. Moreover, the optimal case is considered when the elements are uncorrelated and fully correlated. In the uncorrelated case, random and equal phase shifts provide the same performance. However, the performance of correlated elements attains significant gains when there are equal phase shifts. Finally, we show that correlation is always beneficial to energy transfer, whereas it is a degrading factor for information transfer under random and optimal configurations.