Self-calibration of TOA/distance relationship for wireless localization in harsh environments

The success of location-based services in open areas, mainly driven by Global Navigation Satellite Systems (GNSS), has pushed the research community towards the development of robust systems that provide a similar localization accuracy in harsh environments, where there is no line-of-sight (LOS) to satellites. Techniques based on time-of-arrival (TOA) measurements are the most promising since they can offer an appropriate balance between accuracy and complexity. However, their performance is commonly compromised by the knowledge of an accurate model relating TOA measurements and distance, which can involve an arduous task of calibration. In this paper, we present a method for real-time self-calibration of the model relating TOA and distance, based on TOA measurements exchanged among the anchors in the wireless network. Simulation and empirical results show the appropriateness of the derived models for a TOA-based localization system, since the obtained errors are remarkably close to the ones achieved with pre-calibrated parameters.