Node Positioning in Ad Hoc Wireless Sensor Networks

Locating the sensor nodes in an ad hoc wireless sensor network (WSN) is a very challenging task. In general, the network nodes are not synchronised and the internal delays within the sensor nodes may be unknown. As a result, the positioning problem can not be solved by simply using the triangulation method and certain prior information must be provided. In this paper, we consider a scenario where there are a number of nodes whose positions are known, and it is required to locate the other mobile or static sensor nodes within the radio range of each other by measuring the time of arrival (TOA) in the whole system. Two algorithms are employed, the direct method and the linear least squares (LS) estimator. The performance of the two algorithms is investigated. In particular an analytical formula is derived to estimate the performance of the LS estimator. Simulation results agree well with theoretical predictions.