RIS-Enabled and Access-Point-Free Simultaneous Radio Localization and Mapping

TL;DR

This paper introduces a RIS-enabled radio SLAM framework for 6G systems that operates without access points, utilizing RIS phase profiles and advanced filtering to estimate user location and environment mapping.

Contribution

It presents a novel RIS-based SLAM approach that eliminates the need for access points and incorporates Doppler shift considerations for improved accuracy.

Findings

RIS enables AP-free radio SLAM

The proposed method achieves accurate localization and mapping

Doppler shift improves user speed estimation

Abstract

In the upcoming sixth generation (6G) of wireless communication systems, reconfigurable intelligent surfaces~(RISs) are regarded as one of the promising technological enablers, which can provide programmable signal propagation. Therefore, simultaneous radio localization and mapping(SLAM) with RISs appears as an emerging research direction within the 6G ecosystem. In this paper, we propose a novel framework of RIS-enabled radio SLAM for wireless operation without the intervention of access points (APs). We first design the RIS phase profiles leveraging prior information for the user equipment~(UE), such that they uniformly illuminate the angular sector where the UE is probabilistically located. Second, we modify the marginal Poisson multi-Bernoulli SLAM filter and estimate the UE state and landmarks, which enables efficient mapping of the radio propagation environment. Third, we derive the theoretical Cram\'er-Rao lower bounds on the estimators for the channel parameters and the UE state. We finally evaluate the performance of the proposed method under scenarios with a limited number of transmissions, taking into account the channel coherence time. Our results demonstrate that the RIS enables solving the radio SLAM problem with zero APs, and that the consideration of the Doppler shift contributes to improving the UE speed estimates.