GPS-less location algorithm for wireless sensor networks

The node location problem in wireless networks has been a research interest in the last years. In environments where GPS is not an option (e.g., for consumption reasons or because there is no direct link with the satellite constellation), the estimation of a node position using only RF signals is not a trivial task. Although some other systems have been proposed (ultrasonic signals, IR, etc.), these require additional hardware that is only useful for location purposes. According to this point, some algorithms have been proposed for providing sensible position estimations in the presence of distance errors. These methods normally require heavy computational processes to overcome the presence of these errors or easily degrade when the distance measurements have a certain magnitude. This paper describes an algorithm to compute the location of a node in the presence of severe distance estimation errors and analyzes its performance and computational cost. To make the implementation of this algorithm feasible in wireless sensor networks, different optimization techniques are proposed, in order to speed-up the location estimation of a node, without losing its estimating power.