Range Free Localization Schemes for Wireless Sensor Networks

Wireless sensor networks have become a hot research area due to their numerous applications in monitoring inaccessible areas, which are difficult to be monitored by conventional methods. A large number of wireless sensor network based applications are location dependent, where the sensed data is meaningless without accurate location of its origin. Some of these applications require highly accurate location information of sensor nodes. However, in many applications, knowledge of coarse accuracy of sensor node localization is sufficient. In such applications, range-free localization techniques are being used as low cost alternative to the range based localization techniques. All nodes in a sensor network cannot be made location aware, as it may escalate the cost of sensor network deployment. Therefore, to reduce the cost, very few location aware nodes, known as anchor nodes are deployed in the sensor network, all other nodes need to determine their location with the help of anchor nodes. Therefore, localization in wireless sensor network is to determine the geographical position of sensor nodes, based on the known position of anchor nodes. In this paper, range-free centroid schemes, based on fuzzy logic inference approach have been proposed. The proposed schemes have been compared with existing rangefree centroid based localization schemes through extensive simulations. A new cooperative localization technique based on fuzzy logic inference approach has also been proposed, which require deployment of very less number of anchor nodes in sensing field as compared to the conventional techniques; yet it provides required accuracy in localization of sensor nodes. The cooperative scheme requires very small number of location aware anchor nodes to be deployed, which reduces the cost of sensor network deployment. The simulation results demonstrate that through proposed cooperative localization technique, the desired accuracy in localization can be achieved even by use of few number of anchor nodes.