An Energy Efficient Tracking algorithm in UWB-based sensor networks

This paper presents a novel `Energy Efficient Tracking´ (EET) algorithm that tries to meet the localization accuracy requirement, P<sub>a</sub>, imposed by a generic location-based application while the energy consumption for ranging and communication is optimized. More specifically, given the set of range measurements performed by a mobile node with respect to its neighboring anchors (i.e., nodes whose exact positions are known a priori), the proposed EET algorithm selects, on the basis of the Cramér-Rao lower bound (CRLB), the closest set of anchors such that the resulting positioning error is lower than the required P<sub>a</sub>. At the same time, the EET approach minimizes the average energy consumption by dynamically adapting the transmitted power, P<sub>t</sub>, to be used in the next positioning estimation step. Based on time-of-arrival (TOA) estimation with ultra-wide bandwidth (UWB) nodes, the EET approach uses an Extended Kalman Filter (EKF) to track the mobile node´s position. Simulation results show that the EET algorithm effectively reduces the energy consumption while the achieved positioning performance is almost identical to the one achieved by a classical EKF with fixed P<sub>t</sub>, named `Energy Fixed Tracking´ (EFT) algorithm.