Collaborative Localization Algorithms for Wireless Sensor Networks with Reduced Localization Error

Localization is an important research issue in Wireless Sensor Networks (WSNs). Though Global Positioning System (GPS) can be used to locate the position of the sensors, unfortunately it is limited to outdoor applications and is costly and power consuming. In order to find location of sensor nodes without help of GPS, collaboration among nodes is highly essential so that localization can be accomplished efficiently. In this paper, novel localization algorithms are proposed to find out possible location information of the normal nodes in a collaborative manner for an outdoor environment with help of few beacons and anchor nodes. In our localization scheme, at most three beacon nodes should be collaborated to find out the accurate location information of any normal node. Besides, analytical methods are designed to calculate and reduce the localization error using probability distribution function. Performance evaluation of our algorithm shows that there is a tradeoff between deployed number of beacon nodes and localization error, and average localization time of the network can be increased with increase in the number of normal nodes deployed over a region

Towards the deployment and adoption of Location-based services for optimal mobile communication operations in Africa

Africa is the world’s second largest and second most populous continent with about one billion people. Mobile phones are a major source of communication and means of taking information and technology to rural and remote areas of the continent. With low-cost and readily available mobile phones, underprivileged, low-income earners and rural dwellers can also participate in the Information and Communication Technology (ICT) revolution. Services are introduced by mobile operators and vendors to enhance and optimize this mobile evolution. One of such service is location-based services (LBS); LBS make available personalized services based on the geographical location of the subscriber’s phone. LBS will be of great technological advantage in Africa optimizing operators’ networks and bringing location information and services closer to the people. This paper offers some suggestions on effective deployment and adoption of LBS in Africa based on case studies from developed and developing countries

Intégration d'un système radio à bande ultra-large pour la navigation de robots mobiles

RÉSUMÉ: La localisation revêt une grande importance dans les applications de robotique mobile. Cette tâche devient plus compliquée quand il s'agit d’une localisation d'un groupe de robots évoluant dans un environnement partagé. Un élément clé dans ce type d'application est le système de mesure des distances qui permet de localiser chaque robot en se basant sur les mesures des distances qui les séparent. Les travaux réalisés, dans la plupart des algorithmes multi-robots, supposent qu'il existe une solution efficace pour effectuer ces mesures de distance. Cependant, avoir une bonne précision dans le système de mesures représente un vrai problème, en particulier dans un environnement intérieur. Le travail réalisé dans le cadre de cette maîtrise a pour objectif le déploiement d'un système permettant à un robot mobile d'effectuer des mesures de distance avec d'autres robots ou un certain nombre de points de référence. Ceci est fait en intégrant aux robots un système de communication Ultra Wideband (UWB) pour les mesures de distance. Cette technologie est l'une des plus intéressantes pour ce type d'application. Son avantage majeur est sa forte résolution temporelle pour effectuer des mesures assez précises du temps de propagation d'un signal. Le système de mesure de distance développé a été également exploité dans la navigation robotique ce qui devrait être utile dans nombreuses applications. En effet, la fusion des mesures de distance UWB avec un système de navigation inertielle permet d'avoir un système de localisation haute précision qui peut être déployé autant à l'intérieur qu'à l'extérieur. Les résultats expérimentaux montrent que ce système de localisation hybride peut être intégré dans plusieurs types de plate-formes robotiques, tels que les drones et les robots au sol. En outre, le système conçu peut servir également à la communication courte portée entre les robots. Mots clés : Ultra Wideband, système de mesure de distance, localisation, robotique mobile.---------- ABSTRACT Localization is one of the most important tasks in mobile robotics applications. The complexity of this task increases when it comes to multi-robot localization. For such applications, a ranging system could be used to perform range measurements between robots and enable cooperative localization of the robots based on range measurements. Much of the work carried in multi-robot localization assumes that there is an efficient solution to perform ranging measurements. However, such a system is not easy to deploy, especially in an indoor environment. In this report, we introduce a design of a ranging system based on Ultra-wideband technology. This system is able to provide effective tools for mobile robots to perform ranging measurements with other robots. UWB technology has important advantages for such applications due to its good ability to resolve the temporal features of signals. The developed ranging measurement system is also used for robotic localization, which is useful in many applications, such as autonomous navigation. In fact, merging the UWB ranging system with an inertial navigation system allows us to achieve cm-level accuracy at high update rates. Merging these two systems makes up for the shortcomings of each, and gives a better performance than what is possible with a single system. The experimental results show that the hybrid positioning system can be used with several types of robotic platforms, such as drones and unmanned ground robots. In addition, the proposed system could be useful for the short-range communication between robots. Keywords : Ultra Wideband, ranging measurements system , localization, mobile robotics

Combining Mobile Technologies For Accurate, Open Source, Privacy Sensitive, Zero Cost, Location Determination

Determining the location of an object or individual using a mobile device (e.g. cell phone) is an important aspect of modern information gathering. Various solutions have been proposed which all have their strengths and weaknesses. To date, no solution has been devised for a mobile device that will work effectively in multiple environments and without assistance from network-provider connections1. To address this, it is argued that the current state of the art can be advanced using a hybrid approach that combines a number of sensor technologies to provide a more reliable, and accurate mobile location determination that functions in multiple environments (indoors and outdoors). This thesis examines in detail current relevant available technology, calculation techniques for location determination, the Global Navigation Satellite System (GNSS) and other noteworthy location determination research. It then introduces our solution of a hybrid positioning system that is an open-source, provider-network independent, privacy sensitive, zero-cost and accurate software component. First the overall system design is described and then individual modules are described in detail. It describes in full an algorithm that intelligently combines signals from various technologies, applies weights to these signals and also leverages past signal readings to enhance current calculations. Next, the evaluation section is introduced which discusses how and why the test bed was chosen and deployed. It then discusses individual test results and finally the overall tests are analysed, discussed and summarised. Finally, the conclusions are prepared in detail, the three initial questions raised in the introduction are answered and discussed and the contributions to the body of knowledge are reaffirmed. Future work finishes the thesis and looks at several research paths that can be pursued from this research

A Hybrid Localization Approach in Wireless Sensor Networks by Resolving Flip Ambiguity

Localization has received considerable attention because many wireless sensor network applications require accurate knowledge of the locations of the sensors in the network. In the process the location calculation is achieved by either distance measurements or angle-of‐arrival measurement. However, the former technique suffers from flip ambiguity due to either the presence of insufficient reference points or uncertainties in the inter‐nodal distance measurements in a triangular network structure. A recently proposed quadrilateral structure (an extended complex version of a trilateration structure) can resolve flip ambiguity of a node in dense deployments under restricted orientations for anchors. However, the technique leaves open issues to consider imprecise inter‐nodal distances between all pairs of nodes as complexity increases due to measurement uncertainties in determining the locations. Moreover, both the structures (trilateral and quadrilateral) completely fail to resolve flip ambiguity in sparse node deployments as sufficient nodes are not available in order to determine the signs in calculated angles. On the other hand, AOA can provide the sign of the angles but requires expensive hardware calibration to provide a high‐level of accuracy in the measured angles. Therefore, there is a need of a localization technique that is cheaper, less complex, and robust by considering measurement uncertainties between all pair of nodes and more importantly, involves fewer reference nodes. The primary contributions of this thesis include a hybrid technique that uses low‐accuracy (cheap) AOA measurements along with erroneous distance measurements between each pair of nodes in a much simpler triangular network that corresponds to a sparse deployment. In our initial phase we develop mathematical models involving only two reference nodes that are able to resolve flip ambiguity a unknown node with a high probability of success even with an RMS error as high as 150 in the line‐of‐bearing estimate, which avoids the need for calibration in many practical situations. In later phases, we modelled our hybrid localization technique to accommodate imprecise inter‐nodal measurements between all pairs of nodes. In the final phase, we intend our localization technique to solve ambiguity in extremely sparse scenarios with non‐closed network structure that are yet to be solved by existing localizations approaches. Resolution of flip ambiguity is useful, not only to develop lower‐complexity localization techniques, but also for many lower‐layer network functionalities such as geographic routing, topology control, coverage and tracking, and controlled mobility when a large number of these nodes have to be deployed

Location of mobile terminals using time measurements and survey points

Abstract—Mobile terminal location has attracted much interest for its applications in emergency communications, location-sensitive browsing, and resource allocation. This paper introduces the use of nonparametric kernel-based estimators for location of mobile terminals using measurements of propagation delays. It is demonstrated that these estimators perform better than the previously used parametric maximum likelihood estimators for the case of a simulated microcell environment with line-of-sight (LOS) and non-line-of-sight (NLOS) radio propagation at several different levels of measurement noise. Their performance is not greatly degraded by NLOS effects. Methods for calculating good values for parameters of the kernel functions are demonstrated, as well as the robustness of the estimators when the values of the parameters vary from the optimal points. A lower bound on the mean square error of location estimation that considers the transition between LOS to NLOS propagation over short distances is presented. It is demonstrated the proposed location estimation method comes close to meeting this bound. Index Terms—Land mobile radio cellular systems, position measurement, road–vehicle location monitoring. I