Optimal Two-way TOA Localization and Synchronization for Moving User Devices with Clock Drift

TL;DR

This paper introduces TWLAS, an optimal two-way TOA localization and synchronization method that accounts for user device mobility, significantly improving accuracy over traditional stationary assumptions and approaching theoretical limits.

Contribution

It proposes a maximum likelihood-based approach for moving user devices in two-way TOA systems, extending existing methods to include mobility compensation and error analysis.

Findings

TWLAS achieves estimation accuracy close to the CRLB for moving UDs.

It outperforms conventional one-way TOA methods in accuracy.

The method remains robust even with velocity estimation deviations.

Abstract

In two-way time-of-arrival (TOA) systems, a user device (UD) obtains its position and timing information by round-trip communications to a number of anchor nodes (ANs) at known locations. Compared with the one-way TOA technique, the two-way TOA scheme is easy to implement and has higher localization and synchronization accuracy. Existing two-way TOA methods assume a stationary UD. This will cause uncompensated position and timing errors. In this article, we propose an optimal maximum likelihood (ML) based two-way TOA localization and synchronization method, namely TWLAS. Different from the existing methods, it takes the UD mobility into account to compensate the error caused by the UD motion. We analyze its estimation error and derive the Cramer-Rao lower bound (CRLB). We show that the conventional two-way TOA method is a special case of the TWLAS when the UD is stationary, and the TWLAS has high estimation accuracy than the conventional one-way TOA method. We also derive the estimation error in the case of deviated UD velocity information. Numerical result demonstrates that the estimation accuracy of the new TWLAS for a moving UD reaches CRLB, better than that of the conventional one-way TOA method, and the estimation error caused by the deviated UD velocity information is consistent with the theoretical analysis.