Joao Figueiras

Mobile Positioning and Tracking: From Conventional to Cooperative Techniques

This book presents the most recent state of the art in mobile positioning and tracking techniques. This book discusses mobile positioning solutions applied on top of current wireless communication networks. In addition, the authors introduce advanced and novel topics such as localization in heterogeneous and cooperative networks, providing a unified treatment of the topic for researchers and industry professionals alike. Furthermore, the book focuses on application areas of positioning, basics of wireless communications for positioning, data fusion and filtering techniques, fundamentals of tracking, error mitigation techniques, positioning systems and technologies, and cooperative mobile positioning systems. Key Features: Covers the state of the art of satellite- and terrestrial-based positioning systems, spanning from outdoor to indoor environments and from wide area networks to short-range networks Discusses a whole range of topics related to mobile positioning: from fundamentals of positioning to the description of a wide spectrum of mobility models for tracking, from details on data fusion and filtering techniques to error mitigation techniques (including aspects of signal processing) Provides a solid bridge between research and industry envisaging a potential implementation of the presented solutions Fills the gap between positioning and communication systems, showing how features of communication systems can be used for positioning purposes and how the retrieved location information can be used to enhance the performance of wireless networks. Includes an accompanying website This book will be a valuable guide for advanced students studying related courses. Professionals and practitioners in the field of positioning and mobile technologies, and software and service developers will also find this book of interest.

Cooperative Positioning Techniques for Mobile Localization in 4G Cellular Networks

In this paper, we exploit the concept of cooperative localization by utilizing the additional information obtained from short-range links to enhance the location estimation accuracy in forthcoming cellular systems. Simulations for a hybrid WiMAX/Wi-Fi system are carried out considering an outdoor environment, where time difference of arrival (TDOA) and received signal strength (RSS) measurements are combined thanks to advanced data fusion techniques. Results show that the proposed system allows to meet the federal Communications Commission (FCC) requirements and overcome the ever changing channel conditions.

Accuracy and timing aspects of location information based on signal-strength measurements in Bluetooth

Accurate positioning of wireless devices using short-range link-technologies is interesting for a number of applications including tracking, location-based services, and context sensitive networking. In this paper, accuracy and timing aspects for an indoor positioning method based on triangulation using signal strength measurements of Bluetooth links are analyzed experimentally and via simulation models. In the approach chosen in this paper, the delay to obtain signal strength measurements is determined by complex interactions of the Bluetooth inquiry procedure, which are analyzed in detailed simulation experiments. The location accuracy analysis is performed experimentally for the setting of an indoor corridor scenario including multi-path propagation properties

Design and Implementation of Real-Time Wearable Devices for a Safety-Critical Track Warning System

Trackside railway workers can benefit of intelligent systems for automatic track warning, that are able to safely (i) detect trains or rolling stock approaching the worksite, and (ii) notify their arrival to the workers. The usage of wearable mobile devices to monitor workers positions and notify trains arrivals requires to face serious challenges mainly in terms of service timeliness, safety, security and ergonomics (this last one to define notification signals to the workers that are always perceivable). This paper presents the design and the prototype of the Mobile Terminal (MT), a wearable, real time, wireless, safety-critical device which exploits information received from track monitoring devices to inform a worker about trains or rolling stock approaching the worksite. The MT design concept is based on a hybrid architecture to favor the apportionment of different requirements, in terms of timing and security, to the different parts of the MT. Additionally, the MT includes novel solutions to interface with the worker, to realize an accurate localization service and to achieve safety-critical real-time communication.

Experimental Activity on Cooperative Mobile Positioning in Indoor Environments

Traditional localization systems are based on the information obtained from some fixed reference points (e.g., Access Points (APs)) to Mobile Station (MS) links; typically for short-range, Received Signal Strength Difference (RSSD) or Received Signal Strength (RSS) measurements are used. In order to enhance the accuracy of localization systems indoors, the innovative solution presented in this paper considers also the information obtained from MS-MS links. A proof of concept in a real scenario is implemented in an indoor environment by using a Wireless Local Area Network (WLAN), and the results show that the accuracy is enhanced with respect to non-cooperative schemes. Non-Linear Least Square (NLLS) and Extended Kalman Filter (EKF) are used as data fusion algorithms to combine RSSD measurements from AP-MS links and RSS measurements from MS-MS links.

Hybrid Data Fusion and Cooperative Schemes for Wireless Positioning

The wireless hybrid enhanced mobile radio estimators (WHERE) consortium researches radio positioning techniques to improve various aspects of communications systems. In order to provide the benefits of position information available to communications systems, hybrid data fusion (HDF) techniques estimate reliable position information. Within this paper, we first present the scenarios and radio technologies evaluated by the WHERE consortium for wireless positioning. We compare conventional HDF approaches with two novel approaches developed within the framework of WHERE. Yet, HDF may still provide insufficient localization accuracy and reliability. Hence, we will research and develop new cooperative positioning algorithms, which exploit the available communications links among mobile terminals of heterogeneous wireless networks, to further enhance the positioning accuracy and reliability.

Enhancement of localization accuracy in cellular networks via cooperative ad-hoc links

Positioning information enables new applications for cellular phones, personal communication systems, and specialized mobile radios. The network heterogeneity emerging in the fourth generation (4G) of mobile networks can be utilized for enhancements of the location estimation accuracy. In this paper, we propose a method to perform the localization in a system based on the coexistence of the cellular and the ad-hoc links. The main contribution of this paper is the implementation and evaluation of an Extended Kalman Filter, which merges two available domains of measurements: the time difference of arrival and the received signal strength, respectively retrieved from the long- and the short-range segments. The simulation results show that the proposed localization system outperforms a stand-alone cellular system in the considered scenarios.

GPS and Electronic Fence Data Fusion for Positioning within Railway Worksite Scenarios

Context-dependent decisions in safety-critical applications require careful consideration of accuracy and timeliness of the underlying context information. Relevant examples include location-dependent actions in mobile distributed systems. This paper considers localization functions for personalized warning systems for railway workers, where the safety aspects require timely and precise identification whether a worker is located in a dangerous (red) or safe (green) zone within the worksite. The paper proposes and analyzes a data fusion approach based on low-cost GPS receivers integrated on mobile devices, combined with electronic fences strategically placed in the adjacent boundaries between safe and unsafe geographic zones. An approach based on the combination of a Kalman Filter for GPS-based trajectory estimation and a Hidden Markov Model for inclusion of mobility constraints and fusion with information from the electronic fences is developed and analyzed. Different accuracy metrics are proposed and the benefit obtained from the fusion with electronic fences is quantitatively analyzed in the scenarios of a single mobile entity: By having fence information, the correct zone estimation can increase by 30%, while false alarms can be reduced one order of magnitude in the tested scenario.

Decoupling Estimators in Mobile Cooperative Positioning for Heterogeneous Networks

Positioning in wireless communications represents nowadays an important topic in the research community. The main reason is the increasing number of new location based services available on the market. Since some types of these services require accurate positioning information, research has evolved in the direction of overcoming the adverse propagation effects that commonly degrade accuracy of positioning solutions. One approach to overcome propagation effects is to consider cooperative schemes where close-by users share information regarding their links. However, due to the coexistence of numerous technologies, heterogeneity and interaction between technologies shall be regarded as an additional problem. This paper proposes and analyzes a positioning framework for cooperative schemes, which is specifically beneficial for scenarios with heterogeneous link technologies.

Emerging Directions in Wireless Location: Vista from the COMET Project

In this paper, we give an overview of the emerging directions in wireless location according to the Cooperative Mobile Positioning (COMET) project. The latter proposes innovative solutions for the fourth generation (4G) mobile localization, which directly originate from investigating the impact of cooperation among heterogeneous terminals in hybrid cellular ad-hoc networks. Besides launching a promising new branch of wireless location, the main focus of COMET is on the design of the required protocols (link layer) and algorithms (clustering, positioning and tracking) that would support what we regard as a cooperative mobile positioning system. Moreover, in order to highlight the practical potential of our findings, we will also implement a demonstrator in a WLAN 802.11b/g network environment, where a real-time indoor navigation application will run on a group of heterogeneous wireless devices.