A Topology Based Localization in Ad Hoc Mobile Sensor Networks

Localization in an ad hoc mobile sensor network is an important requirement as most of the applications that use sensor data require sensor location information to complete the processing. A typical sensor network has over hundred to thousand sensor nodes, and considering the size and cost of a sensor, using only GPS for localization is not very attractive. The mobility of sensor nodes could lead to network topologies wherein accurate computation of absolute position of all the sensor nodes may not be possible. In this paper, we propose a topology based localization approach that suggests a best possible approximate position for sensor nodes for which computation of exact absolute position is not possible. We have identified four basic topological configurations that help compute position with varied degree of accuracy. These atomic configurations have been identified keeping in mind the simplicity of the computational procedures associated with these configurations. In order to put less demand on a computational capability of a sensor node, we suggest that only a pre-defined number of sensor nodes are compute-enabled (c-nodes) in the sense that they have adequate computational power. Similarly, only a predefined number of sensor nodes are GPS-enabled. In such a sensor network, the distributed computation of localization is achieved by distributing the computational requirements of individual sensor nodes across the c-nodes. Each sensor node strives to improve its localization by constantly monitoring its neighborhood and requesting an associated c-node to recompute position whenever neighborhood topology changes. We provide some initial results that bring out the merits of the proposed approach.