From the Characterization of Ranging Error to the Enhancement of Nodes Localization for Group of Wireless Body Area Networks

International audienceTime-based localization in Wireless Body Area Networks (WBANs), has attracted growing research interest for the last past years. Nodes positions can be estimated based on peer-to-peer radio transactions between devices. Indeed, the accuracy of the localization process could be highly affected by different factors , such as the WBAN channels where the signal is propagating through, as well as the nodes mobility that bias the peer-to-peer range estimation, and thus, the final achieved localization accuracy. The goal of this paper consists in characterizing the impact of mobility and WBAN channel on the ranging and localization estimation, based on real mobility traces acquired through a motion capture system. More specifically, the ranging error is evaluated over all the WBANs links (i.e. on-body, off-body and body-to-body links), while an impulse Radio Ultra-Wideband (IR-UWB) physical layer, as well as a TDMA-based Medium Access Control (MAC) are playing on. The simulation results show that the range measurement error can be modeled as a Gaussian distribution. To deal with the gaus-sianity observation of ranging error and to provide high positioning accuracy, an adjustable extended Kalman Filter (EKF) is proposed

A Framework for UWB-Based Communication and Location Tracking Systems for Wireless Sensor Networks

Ultra wideband (UWB) radio technology is nowadays one of the most promising technologies for medium-short range communications. It has a wide range of applications including Wireless Sensor Networks (WSN) with simultaneous data transmission and location tracking. The combination of location and data transmission is important in order to increase flexibility and reduce the cost and complexity of the system deployment. In this scenario, accuracy is not the only evaluation criteria, but also the amount of resources associated to the location service, as it has an impact not only on the location capacity of the system but also on the sensor data transmission capacity. Although several studies can be found in the literature addressing UWB-based localization, these studies mainly focus on distance estimation and position calculation algorithms. Practical aspects such as the design of the functional architecture, the procedure for the transmission of the associated information between the different elements of the system, and the need of tracking multiple terminals simultaneously in various application scenarios, are generally omitted. This paper provides a complete system level evaluation of a UWB-based communication and location system for Wireless Sensor Networks, including aspects such as UWB-based ranging, tracking algorithms, latency, target mobility and MAC layer design. With this purpose, a custom simulator has been developed, and results with real UWB equipment are presented too

Tracking in Wireless Sensor Network Using Blind Source Separation Algorithms

This thesis describes an approach to track multiple targets using wireless sensor networks. In most of previously proposed approaches, tracking algorithms have access to the signal from individual target for tracking by assuming (a) there is only one target in a field, (b) signals from different targets can be differentiated, or (c) interference caused by signals from other targets is negligible because of attenuation. We propose a general tracking approach based on blind source separation, a statistical signal processing technique widely used to recover individual signals from mixtures of signals. By applying blind source separation algorithms to mixture signals collected from sensors, signals from individual targets can be recovered. By correlating individual signals recovered from different sensors, the proposed approach can estimate paths taken by multiple targets. Our approach fully utilizes both temporal information and spatial information available for tracking. We evaluate the proposed approach through extensive experiments. Experiment results show that the proposed approach can track multiple objects both accurately and precisely. We also propose cluster topologies to improve tracking performance in low-density sensor networks. Parameter selection guidelines for the proposed topologies are given in this Thesis. We evaluate proposed cluster topologies with extensive experiments. Our empirical experiments also show that BSS-based tracking algorithm can achieve comparable tracking performance in comparison with algorithms assuming access to individual signal

Arquitecturas para la adquisición y distribución de la información de localización en sistemas de seguimiento en interiores basados en UWB

El presente trabajo fin de máster se enmarca dentro de la participación de la Universidad de Zaragoza, a través del Grupo de Tecnologías de las Comunicaciones (GTC) del Instituto de Investigación en Ingeniería de Aragón (I3A), en el proyecto integrado EUWB del VII Programa Marco. La tecnología radio Ultra-Wideband es una de las tecnologías más prometedoras de cara a su uso en aplicaciones de localización y seguimiento en interiores, combinando un bajo consumo de potencia, complejidad y coste con una precisión del orden de centímetros en la estimación de las distancias, proporcionando buenas prestaciones en entornos multicamino y NLOS y permitiendo el despliegue de redes de transmisión de datos combinada con localización. Sin embargo, Ultra-Wideband presenta una serie de limitaciones tales como su corto alcance, y su limitada tasa de transmisión. Cualquier sistema de localización basado en la estimación del tiempo de llegada conlleva el intercambio de tramas de ranging entre el nodo a localizar y una serie de nodos de referencia. Esto implica que una serie de recursos temporales (timeslots) deberán dedicarse a la localización, con la consiguiente reducción de la capacidad disponible para la transmisión de datos. Por ello la cantidad de recursos dedicados a la aplicación de localización debe evaluarse cuidadosamente y minimizarse en la medida de lo posible. El objetivo principal de este trabajo es analizar la viabilidad de sistemas combinados de transmisión de datos y localización en entornos interiores basados en tecnología Ultra-Wideband mediante la evaluación de los recursos utilizados para la localización. Por ello, en el presente trabajo se proponen y evalúan diversas arquitecturas del sistema de seguimiento, así como diferentes estrategias para la adquisición y distribución de información de localización. También se analizará el impacto de otros parámetros de diseño tales como el número de nodos fijos utilizados en el cálculo de la posición, el método de selección de los nodos fijos y la tasa de actualización de la posición. Para ello, se ha desarrollado una aplicación de simulación específica que permita evaluar las prestaciones de cada una de las arquitecturas y estrategias propuestas en términos de recursos utilizados para la localización (timeslots necesarios para la adquisición y distribución de la información de localización) y error de posicionamiento

A policy-based architecture for virtual network embedding (PhD thesis)

Network virtualization is a technology that enables multiple virtual instances to coexist on a common physical network infrastructure. This paradigm fostered new business models, allowing infrastructure providers to lease or share their physical resources. Each virtual network is isolated and can be customized to support a new class of customers and applications. To this end, infrastructure providers need to embed virtual networks on their infrastructure. The virtual network embedding is the (NP-hard) problem of matching constrained virtual networks onto a physical network. Heuristics to solve the embedding problem have exploited several policies under different settings. For example, centralized solutions have been devised for small enterprise physical networks, while distributed solutions have been proposed over larger federated wide-area networks. In this thesis we present a policy-based architecture for the virtual network embedding problem. By policy, we mean a variant aspect of any of the three (invariant) embedding mechanisms: physical resource discovery, virtual network mapping, and allocation on the physical infrastructure. Our architecture adapts to different scenarios by instantiating appropriate policies, and has bounds on embedding enablesciency, and on convergence embedding time, over a single provider, or across multiple federated providers. The performance of representative novel and existing policy configuration are compared via extensive simulations, and over a prototype implementation. We also present an object model as a foundation for a protocol specification, and we release a testbed to enable users to test their own embedding policies, and to run applications within their virtual networks. The testbed uses a Linux system architecture to reserve virtual node and link capacities