Localization in Wireless Sensor Networks (WSNs) is an important research topic: readings come from sensors scattered in the environment, and most of applications assume that the exact position of the sensors is known. Due to power restrictions, WSN nodes are not usually equipped with a global positioning system—hence, many techniques have been developed in order to estimate the position of nodes according to some measurements over the radio channel. In this paper, we propose a new technique to track a moving target by combining distance measurements obtained from both narrowband IEEE 802.15.4 and Ultrawideband (UWB) radios, and then exploiting a novel speed-based algorithm for bounding the error. This process is applied to a real dataset collected during a measurement campaign, and its performance is compared against a Kalman filter. Results show that our algorithm is able to track target path with good accuracy and low computational impact. 1. Introduction A Wireless Sensor Network (WSN) consists of a number of autonomous elements spatially distributed in an environment to monitor physical parameters, detect events, or track objects. These core elements of a WSN are called nodes, and each of them has a radio transceiver, a microcontroller, and a power source like an energy harvester or a battery. In addition, a node is connected to a number of sensors, and the acquired values are cooperatively processed and delivered wirelessly through the network. Size, energy, and cost constraints of the nodes result in corresponding limits on the available resources, namely, memory, communications bandwidth, and computational power—these limits must always be considered while developing and designing new algorithms. The development of WSNs was initially motivated by military applications, such as battlefield surveillance, and in the last years they have received considerable attention from many computer science, electronics, and telecommunications researchers. Nowadays, WSNs are used in many industrial and consumer applications, such as home automation, industrial control, structural monitoring, pedestrian navigation, and assets tracking. In all these applications, positional information about one or more devices of the network is a crucial aspect and has motivated a lot of research efforts. A common approach for estimating the unknown position of a sensor node is to exploit ranging information obtained from some fixed-position nodes, hereafter referred as “anchors” [1, 2]. Distance estimation between two antennas is made possible by the received radio waves
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