RIS-aided Joint Localization and Synchronization with a Single-Antenna MmWave Receiver

TL;DR

This paper demonstrates that RIS can enable joint localization and synchronization in single-antenna mmWave MISO systems using only downlink transmissions, achieving near-optimal accuracy.

Contribution

It introduces a novel RIS-assisted method for joint localization and synchronization in single-antenna mmWave MISO systems, eliminating the need for two-way transmissions.

Findings

Achieves Cramér-Rao lower bound accuracy.

Effective initialization with a relaxed estimator.

Works well with moderate system parameters.

Abstract

MmWave multiple-input single-output (MISO) systems using a single-antenna receiver are regarded as promising solution for the near future, before the full-fledged 5G MIMO will be widespread. However, for MISO systems synchronization cannot be performed jointly with user localization unless two-way transmissions are used. In this paper we show that thanks to the use of a reconfigurable intelligent surface (RIS), joint localization and synchronization is possible with only downlink MISO transmissions. The direct maximum likelihood (ML) estimator for the position and clock offset is derived. To obtain a good initialization for the ML optimization, a decoupled, relaxed estimator of position and delays is also devised, which does not require knowledge of the clock offset. Results show that the proposed approach attains the Cram\'er-Rao lower bound even for moderate values of the system parameters.