On the Packet Error Rate of Correlated Shadowing Links in Body-Area Networks

International audienceBody Area Networks (BAN) offer amazing perspectives to instrument and support humans in many aspects of their lives. In this paper, we consider on-body BAN nodes transmitting information towards a common sink, in a star topology. While this setup is usual in wireless networks, the high instability of the BAN radio channel and the proximity of the body make classical communication protocols inefficient. These networks are further constrained by the low transmission power required for both battery life and health concerns. Opportunistic cooperation techniques are of great interest in such environment to ensure reliable communications. In previous works, we studied simple opportunistic relaying schemes under independent BAN links, using a packet error outage criterion. In this paper, we introduce a more realistic case where shadowing variations around the body are now assumed strongly correlated. Generally speaking, here is a lack of definitive measurements and models for the shadowing correlation in multi-hop networks, while it can play a crucial role at the higher layers. Based on the measurement and simulation results of the French BANET project, we use the BAN context as an illustrative example to exhibit how shadowing correlations have a strong impact on relaying approaches performance

WBANs for live sport monitoring : an experimental approach, early results and perspectives

International audienceIn this paper we present a simple Body Area Network (BAN) platform that was built to monitor the performance of a marathon athlete all along the race, meeting real-time and QoS constraints, under good transmission conditions. Data collected during the event (packet loss, signal strength) allowed us to obtain a primary knowledge about the behavior of the radio transmissions between the different links in the network. The results of this experiment and the important disparities observed between the links point out the need to improve the transmission strategy

Full mesh channel measurements on Body Area Networks under walking scenarios

International audienceBody Area Networks (BANs) exhibit a unique form of channel variations and traditional propagation models fail to adequately match the behavior of BAN communication links. We present here the results of a measurement campaign whose primary objective was to characterize the complete mesh of a BAN and simultaneous analyze the quality of every radio link between the different nodes. We performed several measurement campaigns with indoor and outdoor walking scenarios. The data harvested allows us to highlight symmetry issues in the communications, and we prove that it is due in part to hardware variations in the sensors. Furthermore, the simultaneous measurements of the link quality allows us to extract the correlation in their temporal evolution. We show that scenario-based link correlation matrices cannot be considered, but their evolution over time is stable enough to consider that practical protocols may estimate them with sufficient precision

Wireless Cognitive Networks Technologies and Protocols

International audienceSoftware Defined Radio and Cognitive Radio applied to Wireless Sensor Networks and Body Area Networks represent an intriguing and really recent paradigm, which represents an objective of study of several researchers. In order to make this technology effective, it is necessary to consider an analytical model of communication capacity, energy consumption and congestion, to effectively exploit the Software Defined Radio and Cognitive Radio in this type of systems. This chapter discusses on the analytical modeling to make this kind of technologies effective for wireless networks, by focusing on Cognitive Wireless Sensor Networks and Cognitive Wireless Body Area Networks. Moreover, we consider some routing approaches proposed for Cognitive Wireless Sensor Networks and Cognitive Wireless Body Area Networks, and evaluated by means of simulation. Finally, we address additional issues that this type of networks presents by comparing them with “traditional” routing protocols

Performances de l'optique sans fil pour les réseaux de capteurs corporels

This thesis deals with the performance of optical girelles communications for body area networks (BAN) as an alternative solution to the radiofrequency one, in the context of mobile healthcare monitoring. After presenting the main characteristics of a BAN using the radiofrequency technology, specifically in the UWB band, we explain the advantages of the optical wireless technology. Diffuse propagation based on infrared technology is then considered for BAN, exploiting optical reflections from environment surfaces. Several optical wireless channel modeling methods are introduced, and we consider two solutions for the link between two on-body nodes: a classical method named “one reflection model”, used to estimate performance variations, and a ray-launching method, used to take into account a great amount of optical reflections. Considering several scenarios, we determine the outage probability, and show that the diffuse optical wireless technology is able to achieve an on-body link, with the data rates and the quality of service required by health monitoring applications, for a transmitted power far lower than the limit defined in standards. Then, we evaluate the theoretical performance, in terms of error probability, of an optical wireless BAN, considering the optical code division multiple access technique. Finally, we show that a BAN using optical wireless technology is theoretically feasible, regarding a health monitoring application, and considering the mobility of the patient in indoor environment.Cette thèse aborde les performances d’un réseau corporel utilisant la technologie optique sans fil, comme alternative aux radiofréquences. L’application visée concerne la télésurveillance de patients mobiles, en milieu hospitalier. Après avoir défini les principales caractéristiques des réseaux corporels radiofréquences, notamment dans le cas de l’ultra large bande, nous présentons les avantages à utiliser la technologie optique sans fil. Nous considérons ensuite cette technologie en infrarouge, avec une méthode de propagation dite diffuse, exploitant les réflexions des rayons optiques dans l’environnement du réseau corporel. Les différentes méthodes de modélisation d’un canal optique diffus sont introduites, et nous utilisons deux types de méthodes pour modéliser le canal entre deux noeuds portés : un modèle classique dit « à une réflexion », permettant d’évaluer rapidement des variations de performances, et une méthode de lancer de rayon pour considérer un grand nombre de réflexions. En utilisant différents scénarios, ainsi que la notion de probabilité de rupture, nous montrons que l’optique diffuse permet de réaliser un lien corporel, pour les débits et la qualité de service requise par une application de télésurveillance médicale, et pour une puissance de transmission très inférieure à la limite imposée par la sécurité oculaire. Finalement, nous étudions les performances théoriques d’un réseau corporel en optique diffuse en termes de probabilité d’erreur, avec une gestion de l’accès multiple réalisé par répartition de codes optiques. Nous concluons qu’un réseau de capteurs corporels en optique diffuse est théoriquement réalisable, pour une application médicale de surveillance de patients mobiles dans l’environnement

Performance evaluation of direct and cooperative transmissions in body area networks

International audienceBody area networks (BAN) offer amazing perspectives to instrument and support humans in many aspects of their life. Among all possible applications, this paper focuses on body monitoring applications having a body equipped with a set of sensors transmitting in real time their measures to a common sink. In this context, at the application level, the network fits with a star topology, which is quite usual in the broad scope of wireless networks. Unfortunately, the structure of the network at the physical layer is totally different. Indeed, due to the specificity of BAN radio channel features, all radio links are not stationary and all sensors suffer from link losses during independent time frames. In wireless networks, link losses are often coped with multi-hop transmission schemes to ensure a good connectivity. However, since the radio links are not stationary, the multi-hop routes should adapt quickly to BAN changes. We instead propose in this work a different approach based on opportunistic relaying. The concept relies on electing some sensors to support the transmission of other ones having a worst connection. Instead of changing the relay time to time, we rather select a relay node from a statistical perspective. We evaluate this approach from a theoretical point of view and on realistic simulations using the packet error rate outage probability as a performance criterion