Reconfigurable and Static EM Skins on Vehicles for Localization

TL;DR

This paper proposes using reconfigurable and static electromagnetic skins on vehicle roofs to enhance localization accuracy by transforming vehicles into point targets, reducing perspective errors and increasing reflectivity for better sensing.

Contribution

It introduces a novel EMS design for vehicles that improves localization by acting as high-reflectivity retro-reflectors, addressing perspective deformation and reflectivity challenges.

Findings

EMS on vehicles improves localization accuracy.

Reconfigurable and static EMS designs are analyzed.

Cramér-Rao bound confirms performance gains.

Abstract

Electromagnetic skins (EMSs) have been recently considered as a booster for wireless sensing, but their usage on mobile targets is relatively novel and could be of interest when the target reflectivity can/must be increased to improve its detection or the estimation of parameters. In particular, when illuminated by a wide-bandwidth signal (e.g., from a radar operating at millimeter waves), vehicles behave like \textit{extended targets}, since multiple parts of the vehicle's body effectively contribute to the back-scattering. Moreover, in some cases perspective deformations challenge the correct localization of the vehicle. To address these issues, we propose lodging EMSs on vehicles' roof to act as high-reflectivity planar retro-reflectors toward the sensing terminal. The advantage is twofold: \textit{(i)} by introducing a compact high-reflectivity structure on the target, we make vehicles behave like \textit{point targets}, avoiding perspective deformations and related ranging biases and \textit{(ii)} we increase the reflectivity the vehicle, improving localization performance. We detail the EMS design from the system-level to the full-wave-level considering both reconfigurable intelligent surfaces (RIS) and cost-effective static passive electromagnetic skins (SP-EMSs). Localization performance of the EMS-aided sensing system is also assessed by Cram\'er-Rao bound analysis in both narrowband and spatially wideband operating conditions.