Thèse : Improving Medium Access in Dynamic Wireless Sensor Networks

Soutenance de thèse : Georgios PAPADOPOULOS

Équipe : Réseaux

Titre : Improving Medium Access in Dynamic Wireless Sensor Networks

Résumé : Ad-Hoc and Wireless Sensor Networks (WSNs) have enabled a large variety of applications. Environmental and wildlife monitoring, clinical medical and home-care monitoring, monitoring and control of industrial processes including agriculture, smart houses and cities are just some of the examples of Ad-Hoc and WSN applications, where low-cost, and easily deployed multi- functional sensor nodes is the ideal solution. As a result, during the last years we experience the emergence of a new paradigm called Internet of Things (IoT) in which smart and connected objects cooperatively construct a (wireless) network of things.
However, the unique features of these technologies can pose significant challenges. In clinical medical and home-care applications, requirements such as mobility, bursty traffic and energy- efficiency are appear to be essential. In contrary to the traditional a priori known time-driven traffic patterns, event-driven, where nodes transmit their readings upon detection of a specific event determined by the application layer, networks face occasional, bursty and unanticipated multi-hop data packet transmissions. In wildlife monitoring for instance, the nodes (usually with limited-memory devices) operate under limited internet access for the majority of the time. When a network connection is detected, a surge of traffic should be handled. More specifically, the mobile wireless nodes should immediately upload their stored readings (bursts) at a more powerful device (i.e. sink) before losing again the connection. Such sudden dynamic and bursty traffic cause certain anomalies in the network and fuel the research community to find appropriate solutions.
Since, the Medium Access Control (MAC) layer is in charge for coordinating the commu- nication between wireless sensor nodes. Furthermore, among all operations of a sensor node, Transmission, Reception, Central Processing Unit and Low-power-mode, the communication is the most energy consumed. We therefore, in this dissertation, have focused on improving the access to the wireless medium for low-delay communication in energy efficient manner.
My thesis shows that these competing goals can be balanced by the use of effective algorithms and schemes that enable the protocols (and hence the network) to adapt to current application (i.e. varying traffic load) and network conditions (i.e. mobility). In support of this dissertation, we first have i) studied the role of simulators/emulators and testbeds in the research process cy- cle, and we identified the means to strengthen their complementarity, ii) designed, developed and evaluated an algorithm that dynamically and automatically reconfigures the MAC parameters depending on the actual and expected traffic load, iii) proposed MAC layer protocol to coordi- nate the communication between mobile and static nodes even in very dense networks, iv) finally, we demonstrated the advantages of employing low-power MAC protocols in a WSN in terms of latency, reliability, energy consumption and congestion in the network. With mobility-oriented preamble-sampling schemes provided by our new architecture, and the protocol adaptation pro- vided in this dissertation, one can envision new designs at all protocol levels, making wireless sensor networks truly adaptive to changes in both application requirements and network dynam- ics.

Cette thèse a été dirigée par Thomas Noël et co-encadrée par Antoine Gallais (Université de Strasbourg).

La présentation aura lieu le lundi 28 septembre 2015 à 10h30 dans l'amphithéâtre du Collège doctoral européen situé 46 Boulevard de la Victoire.