Single-Anchor Two-Way Localization Bounds for 5G mmWave Systems

TL;DR

This paper investigates two-way localization protocols for 5G mmWave systems without assuming synchronization, deriving error bounds and showing that collaborative localization outperforms round-trip methods, with angular estimation being the main limiting factor.

Contribution

It introduces and analyzes two two-way localization protocols for mmWave 5G systems without synchronization, providing new bounds and performance insights.

Findings

Collaborative localization significantly outperforms round-trip localization.

Angular estimation limits localization accuracy more than temporal estimation.

More antennas at the base station improve localization performance.

Abstract

Recently, millimeter-wave (mmWave) 5G localization has been shown to be to provide centimeter-level accuracy, lending itself to many location-aware applications, e.g., connected autonomous vehicles (CAVs). One assumption usually made in the investigation of localization methods is that the user equipment (UE), i.e., a CAV, and the base station (BS) are {time} synchronized. In this paper, we remove this assumption and investigate two two-way localization protocols: (i) a round-trip localization protocol (RLP), whereby the BS and UE exchange signals in two rounds of transmission and then localization is achieved using the signal received in the second round; (ii) a collaborative localization protocol (CLP), whereby localization is achieved using the signals received in the two rounds. We derive the position and orientation error bounds applying beamforming at both ends and compare them to the traditional one-way localization. Our results show that mmWave localization is mainly limited by the angular rather than the temporal estimation and that CLP significantly outperforms RLP. Our simulations also show that it is more beneficial to have more antennas at the BS than at the UE.