Precise location tracking system based on time difference of arrival over LR-WPAN

As the era of ubiquitous computing approaches, there is a growing need for a reliable, efficient positioning and tracking system. Localization involves continuous determination and tracking of the location of assets and personnel. Localization using time difference of arrival (TDOA) involves determining the location of a tag by calculating the time difference of arrival of the signal received from the tag. In order to calculate the time difference of the signal, TDOA-based methods require precision time synchronization of within a few nanoseconds. This paper presents a location tracking system(LTS), which consists of readers, tags, and an engine, based on TDOA in IEEE 802.15.4. In addition, we propose a precise time measurement method and a precision time synchronization protocol which provides a common clock with an accuracy of within a few nanoseconds. The proposed precision time synchronization protocol results in accurate locating services. The performance shows that readers achieve precision time synchronization of within 5 nanoseconds from a reference clock, and the location tracking system has a location error of within 2 meters.