Design and evaluation of a real-time locating system for wireless sensor networks

Abstract

Evaluating target-tracking protocols for wireless sensor networks that can localise multiple mobile assets can be a very challenging task. Such protocols usually aim at the minimisation of communication overhead, data processing for the participating nodes and delivering adequate tracking information of the mobile assets in a timely manner. Simulations on such protocols are performed using theoretical models that are based on unrealistic assumptions like the unit disc graph communication model, ideal network localisation and perfect distance estimations. With these assumptions taken for granted, theoretical models claim various performance milestones that cannot be achieved in realistic conditions. In this paper, we design a new localisation protocol, where mobile assets can be tracked passively via software agents. Moreover, we address and mitigate issues that hinder performance over the wireless medium and provide a fully deployable protocol. The design, implementation and experimentation of this new protocol along with further optimisations were performed using the WISEBED framework. We apply our protocol in a real indoor wireless sensor testbed with multiple experimental scenarios to showcase scalability and trade-offs between network properties and configurable protocol parameters. By analysis of the real-world experimental output, we present results that depict a more realistic view of the target tracking problem, regarding power consumption and the quality of tracking information. Finally, we also conduct some much focused simulations to assess the scalability of our protocol in very large networks and multiple mobile assets.