Local Positioning for Wireless Sensor Networks

2008

In this paper we address the problem of localizing, tracking and navigating mobile nodes associated to operators acting in a fixed wireless sensor network (WSN) using only RF information. We propose two alternative and somehow complementary strategies: the first one is based on an empirical map of the Radio Signal Strength (RSS) distribution generated by the WSN and on the stochastic model of the behavior of the mobile nodes, while the second one is based on a maximum likelihood estimator and a radio channel model for the RSS. We compare the two approaches and highlight pros and cons for each of them. Finally, after implementing them into two real-time tracking systems, we analyze their performance on an experimental testbed in an industrial indoor environment.

IEEE Signal Processing Magazine, 2005

A look at positioning aspects of future sensor networks.

2000

This paper presents a new method for rectifying low ambient radiation sources to supply autonomous measurement systems such as microsystems. An impedance transformation with high quality factor (Q) in front of a Schottky-Diode using a quartz resonator at 24 MHz is presented. In addition to an analytic computation and nonlinear simulation of the rectifier circuit with Advanced Design System (ADS)

Proceedings of the ImmersCom, 2007

The increasing interest in systems able to provide users with immersive services (e.g., domotics, context-aware applications, and immersive distance learning tools) has encouraged the development of cheap and effective platforms aimed at tracking objects and people within a certain space. In this context, wireless sensor networks (WSNs) can play a very important role, since specialized sensors can be fruitfully exploited in order to generate/receive signals by means of which the WSN can derive the position of nodes joined to the objects to be tracked. The paper presents an original localization platform that exploits a single-hop WSN, based on a Microchip MCU and a Cypress RF device, to track its moving nodes. Specifically, the nodes of the network are divided into three sets: the first set consists of anchor nodes that, according to the commands from the sink (the central node of the WSN), generate ultrasonic pulses. These pulses are received by the second set of (moving) nodes, which estimate the pulse time trip and communicate it to the sink. Finally, the last set is constituted by general purpose nodes that collect any kind of data from the surrounding field. The sink gathers all the data, computes the position of moving nodes, and transfers information to external users on the Internet. The algorithms adopted to manage the network and to localize moving nodes are discussed. A working prototype based upon the hardware platform, software, and protocol described in this paper has been deployed and tested, and some results are shown. Simulation results of the localization system are presented to show system scalability.

2007

The real-world implementation of a just theoretically elaborated idea is sometimes cumbersome, often a couple of obstacles have to be overcome. That's likewise in the area of Wireless Sensor Networks (WSN), but complicated by some further restrictions, e.g. little memory or low power consumption. One well-known and often required application within WSN is the geographical localization of several sensor nodes. That's why this paper deals with some problems arising during the development of a WSN using the time difference of arrival (TDoA) of ultrasound and radio signals for positioning. Its focus is on handling of microcontroller difficulties like little memory, low computational power or low energy consumption as well as hardware driven failures like inaccurate measurements or node failures.

Sensor radars (SRs) are important for a variety of applications requiring passive tracking of moving targets. The accuracy of passive tracking is severely degraded by wireless propagation impairments such as multipath, clutter, and non line-of-sight conditions, especially in indoor environments. These impairments can be alleviated by exploiting the multiple sensing and smart processing of radar signals. In this letter, we aim to illustrate the dependence of sensor topologies, waveform processing methods, and tracking algorithm parameters on SR performance. A case study involving both monostatic and multistatic ultra-wideband SRs for indoor environments is presented by jointly considering the wireless medium, ranging technique, and tracking algorithm.

2007

This paper describes the current efforts to develop an open source, privacy sensitive, location determination software component for mobile devices. Currently in mobile computing, the ability of a mobile device to determine its own location is becoming increasingly desirable as the usefulness of such a feature enhances many commercial applications. There have been numerous attempts to achieve this from both the network positioning perspective and also from the wireless beacon angle not to mention the integration of GPS into mobile devices. There are two important aspects to consider when using such a system which are privacy and cost. This paper describes the development of a software component that is sensitive to these issues. The ICiNG Location Client (ILC) is based on some pioneering work carried out by the Place Lab Project at Intel. (Hightower et al., 2006) The ILC advances this research to make it available on mobile devices and attempts to integrate GSM, WiFi, Bluetooth and ...

2012 IEEE International Conference on RFID-Technologies and Applications (RFID-TA), 2012

An accurate ranging system based on FMCW (Frequency Modulated Continuous Wave) Radar is presented. The system ensures a centimetre precision even in environments with high multipath, such as warehouses packed with metallic objects or extremely dusty sites where conventional RF, laser, ultrasonic or video technologies present severe limitations. The proposed solution has been experimentally applied in Automatic Guided Vehicle for warehouses. The architecture of the system and the obtained results are presented in detail.

Journal of Positioning, Navigation, and Timing

A positioning method using radio frequency (RF) was used to identify the location of soldiers in emergency during the World War II for the first time. In the Vietnam War, a global positioning system (GPS) was introduced. Since then, GPS has been used in various commercial areas from 1990s. Although GPS is the most widely used positioning system in outdoor environments, it is limited to be used in indoor environments (Pahlavan et al. 2002, Sayed et al. 2005, Fang & Lin 2008). Thus, it is highly important to develop indoor positioning technologies using RF (Sayed et al. 2005). Indoor positioning technologies can be utilized in various fields such as commercial, military, and public safety (Gustafsson & Gunnarsson 2005). For example, in commercial fields, demand on tracking locations of children, the elderly, and visually impaired people has increased consistently in

2011

A wideband radio location system for 3D applications with high precision is introduced. For different test scenarios, the system is evaluated with respect to precision, resolution, and reproducibility. Based on ultra wideband direct sequence spread spectrum transmission at 24GHz, the radio location system shows high robustness against interference as well as suppression of the effects of reflections. Distance measurements are processed in a two-stage Kalman filter allowing object tracking with millimeter accuracy even in highly reflective scenarios.