A MULTI AWARE MULTI-LEVELS HETEROGENOUS ROUTING (MAMHR) PROTOCOL FOR WIRELESS SENSOR NETWORKS

Wireless Sensor Networks (WSNs) are generally set out in a remote workplace, since the sensor nodes are tiny in size, cost-proficient, low-power gadgets, and have restricted battery supply. Due to the constrained availability of power sources, energy utilization has been considered as the most crucial factor for proposing network routing protocols. The fundamental concern is to improve the lifetime of the network based on the energy constraints. Several homogenous cluster-based routing protocols have been proposed in literature for lifetime improvement of the sensor network but many of them fail to function effectively in heterogeneous environment and moreover, these protocols have not considered any other awareness parameters than lifetime and energy consumption. In this work, a Multi Aware Multi-Levels Heterogeneous Routing (MAMHR) protocol, focusing on the principle of multi-level heterogeneity by considering multiple awareness parameters of the network such as Quality of Service (QoS), shortest path estimation and suitable localization technique, is proposed. Scoped Bellman Ford Routing (SBFR) algorithm is used for shortest path estimation, Reliability, Availability, and Serviceability (RAS) factors are considered for QoS awareness and Time Difference of Arrival (TDOA) technique is used for location estimation. Lifetime awareness parameters of the proposed scheme were compared with already existing prominent protocols LEACH, SEP and ZSEP and a significant improvement in lifetime of entire network was obtained. Simulation results corresponding to the respective multiple awareness parameters also shows that these parameters can be incorporated into the selected heterogeneous environment without affecting the energy consumption constraints of the proposed scheme

Availability modeling and evaluation of web-based services - A pragmatic approach

Cette thèse porte sur le développement d’une approche de modélisation pragmatique permettant aux concepteurs d’applications et systèmes mis en oeuvre sur le web d’évaluer la disponibilité du service fourni aux utilisateurs. Plusieurs sources d’indisponibilité du service sont prises en compte, en particulier i) les défaillances matérielles ou logicielles affectant les serveurs et ii) des dégradations de performance (surcharge des serveurs, temps de réponse trop long, etc.). Une approche hiérarchique multi-niveau basée sur une modélisation de type performabilité est proposée, combinant des chaînes de Markov et des modèles de files d’attente. Les principaux concepts et la faisabilité de cette approche sont illustrés à travers l’exemple d’une agence de voyage. Plusieurs modèles analytiques et études de sensibilité sont présentés en considérant différentes hypothèses concernant l’architecture, les stratégies de recouvrement, les fautes, les profils d’utilisateurs, et les caractéristiques du trafic. ABSTRACT : This thesis presents a pragmatic modeling approach allowing designers of web-based applications and systems to evaluate the service availability provided to the users. Multiple sources of service unavailability are taken into account, in particular i) hardware and software failures affecting the servers, and ii) performance degradation (overload of servers, very long response time, etc.). An hierarchical multi-level approach is proposed based on performability modeling, combining Markov chains and queueing models. The main concepts and the feasibility of this approach are illustrated using a web-based travel agency. Various analytical models and sensitivity studies are presented considering different assumptions with respect to the architectures, recovery strategies, faults, users profile and traffic characteristics

Reliability models and analyses of the computing systems

Ph.DDOCTOR OF PHILOSOPH