Non-synchronised time difference of arrival localisation scheme with time drift compensation capability

Location finding is a major application for indoor wireless sensor networks. Some of these applications include, but not limited to, logistic tracking for goods, monitoring of patients in hospitals, security application and location aware advertising. In practice, there are many factors such as noise, non-line of sight (NLOS) influence, device crystal clock time drift and accurate synchronisation among sensor nodes that can affect the ranging accuracy. In this study, the authors first propose how non-synchronised sensor nodes can apply a time difference of arrival localisation technique to compute the position of the tags. Next, the authors discuss the impact of crystal clock time drift on localisation accuracy and propose a scheme to compensate them among the sensor nodes in order to reduce its influence on localisation errors. This allows low-cost devices to operate in the network with low crystal clock qualities.