Handling systematic node biases in TDoA positioning systems

TL;DR

This paper introduces a method to mitigate node-specific hardware biases in TDoA positioning systems by adapting GNSS bias correction techniques, demonstrating that these biases are stable enough to be treated as constants for improved indoor navigation accuracy.

Contribution

The work proposes the concept of Differential Transmitter Bias (DTB) for wireless TDoA systems, adapting GNSS bias correction methods to indoor positioning, and shows DTB stability for effective bias calibration.

Findings

DTB are stable over entire sessions with minimal variation (~2m).

Treating DTB as constants improves TDoA positioning accuracy.

Method enables meter-level error correction in indoor navigation.

Abstract

Node-specific hardware biases represent significant error source in wireless Time of Arrival (ToA) and Time Difference of Arrival (TDoA) positioning. While bias estimation and treatment are well-established in Global Navigation Satellite Systems (GNSS), their application in wireless Positioning, Navigation, and Timing (PNT) remains a significant challenge. This work proposes a methodology, based on GNSS data processing, to mitigate these systematic biases. Specifically, the concept of Differential Transmitter Bias (DTB) is introduced to account for node-specific hardware variations. These DTB are in fact analogous to the Differential Code Bias (DCB) used in GNSS. This paper includes an analysis based on real data from a network of wireless nodes employed in an indoor navigation context and shows that the DTB exhibits remarkable stability, allowing it to be treated as a constant during an entire positioning session, with small variations as low as 2m, which is in the same uncertainty level as the noise of the measurements used by a TDoA-based positioning engine. In an operating positioning service context, these DTB would be transmitted to the user, similarly to GNSS, where satellite clock corrections are provided through navigation messages. This would allow the user to callibrate the TDoA measurements in order to obtain positioning with errors on the meter level.