Refined Anchor Free Localisation for Wireless Sensor Monitoring in Wireless Sensor Networks

Localisation is required for many ad-hoc sensor network applications. In this paper we look at the limitations of the existing localisation technique, Anchor Free Localisation (AFL) with regards to coping with non-uniform anchor distributions and errors in ranging information. We present a refined approach called Refined Anchor Free Localisation (R-AFL) that uses a combination of mobile anchor scenarios for anchor information distribution, along with statistical techniques for performing localisation with inaccurate range data. This algorithm is a centralized incremental algorithm. In this algorithm we sue actual distance information instead of hop counts. Since hop counts does not reflect the true distances existing between them. Our algorithm stays in a base station and starts as soon as all the sensors send their local information to its base station. Simulations with our refined approach have shown significant reductions (in the order of magnitude range) to the required processing for performing statistical localisation over previous attempts, as well as improving the generated location information in situations with nontotal anchor information coverage, making possible a wider range of applications.