Range-free Area Localization Scheme for Wireless Sensor Networks

Abstract

For large wireless sensor networks, identifying the exact location of every sensor may not be feasible and the cost may be very high.A coarse estimate of the sensors' locations is usually sufficient for many applications.In this chapter, we describe an efficient Area Localization Scheme (ALS) for wireless sensor networks.ALS is a range-free scheme that tries to estimate the position of every sensor within a certain area rather than its exact location.Furthermore, the powerful sinks instead of the sensors handle all complex calculations.This reduces the energy consumed by the sensors and helps extend the lifetime of the network.The granularity of the areas estimated for each node can be easily adjusted by varying some system parameters, thus making the scheme very flexible.We first study ALS under ideal two-ray physical layer conditions (as a benchmark) before proceeding to test the scheme in more realistic non-ideal conditions modelled by the two-ray physical layer model, Rayleigh fading and lognormal shadowing.We compare the performance of ALS to range-free localization schemes like APIT (Approximate Point In Triangle) and DV (Distance Vector) Hop, and observe that the ALS outperforms them.We also implement ALS on an experimental testbed and, show that at least 80% of nodes lie within a one-hop region of their estimated areas.Both simulation and experimental results have verified that ALS is a promising technique for range-free localization in large sensor networks.