Middleware support for delay-tolerant service provision in disconnected mobile ad hoc networks

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The SATIN component system - a metamodel for engineering adaptable mobile systems

Mobile computing devices, such as personal digital assistants and mobile phones, are becoming increasingly popular, smaller, and more capable. We argue that mobile systems should be able to adapt to changing requirements and execution environments. Adaptation requires the ability-to reconfigure the deployed code base on a mobile device. Such reconfiguration is considerably simplified if mobile applications are component-oriented rather than monolithic blocks of code. We present the SATIN (system adaptation targeting integrated networks) component metamodel, a lightweight local component metamodel that offers the flexible use of logical mobility primitives to reconfigure the software system by dynamically transferring code. The metamodel is implemented in the SATIN middleware system, a component-based mobile computing middleware that uses the mobility primitives defined in the metamodel to reconfigure both itself and applications that it hosts. We demonstrate the suitability of SATIN in terms of lightweightedness, flexibility, and reusability for the creation of adaptable mobile systems by using it to implement, port, and evaluate a number of existing and new applications, including an active network platform developed for satellite communication at the European space agency. These applications exhibit different aspects of adaptation and demonstrate the flexibility of the approach and the advantages gaine

Enhanced Distributed File Replication Protocol for Efficient File Sharing in Wireless Mobile Ad-Hoc Networks.

File sharing applications in mobile unintended networks (MANETs) have attracted additional and additional attention in recent years. The potency of file querying suffers from the distinctive properties of such networks as well as node quality and restricted communication vary and resource. associate degree intuitive methodology to alleviate this drawback is to form file replicas within the network. However, despite the efforts on file replication, no analysis has targeted on the worldwide optimum duplicate creation with minimum average querying delay. Specifically, current file replication protocols in mobile unintended networks have 2 shortcomings. First, they lack a rule to portion restricted resources to completely different files so as to reduce the typical querying delay. Second, they merely contemplate storage as offered resources for replicas, however neglect the actual fact that the file holders’ frequency of meeting different nodes additionally plays a crucial role in deciding file availableness. Actually, a node that contains a higher meeting frequency with others provides higher availableness to its files. This becomes even additional evident in sparsely distributed MANETs, during which nodes meet disruptively. during this paper, we have a tendency to introduce a replacement conception of resource for file replication, that considers each node storage and meeting frequency. we have a tendency to on paper study the influence of resource allocation on the typical querying delay and derive a resource allocation rule to reduce the typical querying delay. we have a tendency to additional propose a distributed file replication protocol to appreciate the projected rule. intensive trace-driven experiments with synthesized traces and real traces show that our protocol are able to do shorter average querying delay at a lower value than current replication protocols

Middleware Services for Network Disruption Tolerant Mobile Applications

Abstract The demand fo r mobile application services has increased recently. However mob ile wireless access technologies so far are not mature enough to address concerns with the reliab ility of mob ile services. Therefore, mobile services are prone to failures caused by disruption of active wireless access network connections due to device movement. It is important to have proper mechanisms for managing mobile application services in case of loss of network connections. In this paper, we propose a middleware services that transparently performs required functionality to users in order to provide efficient mobile services in case of network disruption. Such middleware service provides an effective disconnection tolerant mobile application services

Relying on Safe Distance to Achieve Strong Partitionable Group Membership in Ad Hoc Networks

The design of ad hoc mobile applications often requires the availability of a consistent view of the application state among the participating hosts. Such views are important because they simplify both the programming and verification tasks. We argue that preventing the occurrence of unannounced disconnection is essential to constructing and maintaining a consistent view in the ad hoc mobile environment. In this light, we provide the specification for a partitionable group membership service supporting ad hoc mobile applications and propose a protocol for implementing the service. A unique property of this partitionable group membership is that messages sent between group members are guaranteed to be delivered successfully, given appropriate system assumptions. This property is preserved over time despite movement and frequent disconnections. The protocol splits and merges groups and maintains a logical connectivity graph based on a notion of safe-distance. An implementation of the protocol in Java is available for testing. The implementation is used to implement Lime 1, a middleware for mobility that supports transparent sharing of data in both wired and ad hoc wireless environments

Conception d’un support de communication opportuniste pour les services pervasifs

The vision of pervasive computing of building interactive smart spaces in the physical environment is gradually heading from the research domain to reality. Computing capacity is moving beyond personal computers to many day-to-day devices, and these devices become, thanks to multiple interfaces, capable of communicating directly with one another or of connecting to the Internet.In this thesis, we are interested in a kind of pervasive computing environment that forms what we call an Intermittently Connected Hybrid Network (ICHN). An ICHN is a network composed of two parts: a fixed and a mobile part. The fixed part is formed of some fixed infostations (potentially connected together with some fixed infrastructure, typically the Internet). The mobile part, on the other hand, is formed of smartphones carried by nomadic people. While the fixed part is mainly stable, the mobile part is considered challenging and form what is called an Opportunistic Network. Indeed, relying on short-range communication means coupled with the free movements of people and radio interferences lead to frequent disconnections. To perform a network-wide communication, the "store, carry and forward" approach is usually applied. With this approach, a message can be stored temporarily on a device, in order to be forwarded later when circumstances permit. Any device can opportunistically be used as an intermediate relay to facilitate the propagation of a message from one part of the network to another. In this context, the provisioning of pervasive services is particularly challenging, and requires revisiting important components of the provisioning process, such as performing pervasive service discovery and invocation with the presence of connectivity disruptions and absence of both end-to-end paths and access continuity due to user mobility. This thesis addresses the problems of providing network-wide service provisioning in ICHNs and proposes solutions for pervasive service discovery, invocation and access continuity. Concerning service discovery challenge, we propose TAO-DIS, a service discovery protocol that performs an automatic and fast service discovery mechanism. TAO-DIS takes into account the hybrid nature of an ICHN and that the majority of services are provided by infostations. It permits mobile users to discover all the services in the surrounding environment in order to identify and choose the most convenient ones. To allow users to interact with the discovered services, we introduce TAO-INV. TAO-INV is a service invocation protocol specifically designed for ICHNs. It relies on a set of heuristics and mechanisms that ensures performing efficient routing of messages (both service requests and responses) between fixed infostations and mobile clients while preserving both low values of overhead and round trip delays. Since some infostations in the network might be connected, we propose a soft handover mechanism that modifies the invocation process in order to reduce service delivery delays. This handover mechanism takes into consideration the opportunistic nature of the mobile part of the ICHN. We have performed various experiments to evaluate our solutions and compare them with other protocols designed for ad hoc and opportunistic networks. The obtained results tend to prove that our solutions outperform these protocols, namely thanks to the optimizations we have developed for ICHNs. In our opinion, building specialized protocols that benefit from techniques specifically designed for ICHNs is an approach that should be pursued, in complement with research works on general-purpose communication protocolsLa vision de l'informatique ubiquitaire permettant de construire des espaces intelligents interactifs dans l'environnement physique passe, peu à peu, du domaine de la recherche à la réalité. La capacité de calcul ne se limite plus à l'ordinateur personnel mais s'intègre dans de multiples appareils du quotidien, et ces appareils deviennent, grâce à plusieurs interfaces, capables de communiquer directement les uns avec les autres ou bien de se connecter à Internet.Dans cette thèse, nous nous sommes intéressés à un type d'environnement cible de l'informatique ubiquitaire qui forme ce que nous appelons un réseau hybride à connexions intermittentes (ICHN). Un ICHN est un réseau composé de deux parties : une partie fixe et une partie mobile. La partie fixe est constituée de plusieurs infostations fixes (potentiellement reliées entre elles avec une infrastructure fixe, typiquement l'Internet). La partie mobile, quant à elle, est constituée de smartphones portés par des personnes nomades. Tandis que la partie fixe est principalement stable, la partie mobile pose un certain nombre de défis propres aux réseaux opportunistes. En effet, l'utilisation de moyens de communication à courte portée couplée à des déplacements de personnes non contraints et à des interférences radio induit des déconnexions fréquentes. Le concept du "store, carry and forward" est alors habituellement appliqué pour permettre la communication sur l'ensemble du réseau. Avec cette approche, un message peut être stocké temporairement sur un appareil avant d'être transféré plus tard quand les circonstances sont plus favorables. Ainsi, n'importe quel appareil devient un relai de transmission opportuniste qui permet de faciliter la propagation d'un message dans le réseau. Dans ce contexte, la fourniture de services est particulièrement problématique, et exige de revisiter les composants principaux du processus de fourniture, tels que la découverte et l'invocation de service, en présence de ruptures de connectivité et en l'absence de chemins de bout en bout. Cette thèse aborde les problèmes de fourniture de service sur l'ensemble d'un ICHN et propose des solutions pour la découverte de services, l'invocation et la continuité d'accès. En ce qui concerne le défi de la découverte de services, nous proposons TAO-DIS, un protocole qui met en œuvre un mécanisme automatique et rapide de découverte de services. TAO-DIS tient compte de la nature hybride d'un ICHN et du fait que la majorité des services sont fournis par des infostations. Il permet aux utilisateurs mobiles de découvrir tous les services dans l'environnement afin d'identifier et de choisir les plus intéressants. Pour permettre aux utilisateurs d'interagir avec les services découverts, nous introduisons TAO-INV. TAO-INV est un protocole d'invocation de service spécialement conçu pour les ICHN. Il se fonde sur un ensemble d'heuristiques et de mécanismes qui assurent un acheminement efficace des messages (des requêtes et des réponses de services) entre les infostations fixes et les clients mobiles tout en conservant un surcoût et des temps de réponses réduits. Puisque certaines infostations dans le réseau peuvent être reliées entre elles, nous proposons un mécanisme de continuité d'accès (handover) qui modifie le processus d'invocation pour réduire les délais de délivrance. Dans sa définition, il est tenu compte de la nature opportuniste de la partie mobile de l'ICHN. Nous avons mené diverses expérimentations pour évaluer nos solutions et les comparer à d'autres protocoles conçus pour des réseaux ad hoc et des réseaux opportunistes. Les résultats obtenus tendent à montrer que nos solutions surpassent ces autres protocoles, notamment grâce aux optimisations que nous avons développées pour les ICHN. À notre avis, construire des protocoles spécialisés qui tirent parti des techniques spécifiquement conçues pour les ICHN est une approche à poursuivre en complément des recherches sur des protocoles de communication polyvalent

Cross-layer design of multi-hop wireless networks

MULTI -hop wireless networks are usually defined as a collection of nodes equipped with radio transmitters, which not only have the capability to communicate each other in a multi-hop fashion, but also to route each others’ data packets. The distributed nature of such networks makes them suitable for a variety of applications where there are no assumed reliable central entities, or controllers, and may significantly improve the scalability issues of conventional single-hop wireless networks. This Ph.D. dissertation mainly investigates two aspects of the research issues related to the efficient multi-hop wireless networks design, namely: (a) network protocols and (b) network management, both in cross-layer design paradigms to ensure the notion of service quality, such as quality of service (QoS) in wireless mesh networks (WMNs) for backhaul applications and quality of information (QoI) in wireless sensor networks (WSNs) for sensing tasks. Throughout the presentation of this Ph.D. dissertation, different network settings are used as illustrative examples, however the proposed algorithms, methodologies, protocols, and models are not restricted in the considered networks, but rather have wide applicability. First, this dissertation proposes a cross-layer design framework integrating a distributed proportional-fair scheduler and a QoS routing algorithm, while using WMNs as an illustrative example. The proposed approach has significant performance gain compared with other network protocols. Second, this dissertation proposes a generic admission control methodology for any packet network, wired and wireless, by modeling the network as a black box, and using a generic mathematical 0. Abstract 3 function and Taylor expansion to capture the admission impact. Third, this dissertation further enhances the previous designs by proposing a negotiation process, to bridge the applications’ service quality demands and the resource management, while using WSNs as an illustrative example. This approach allows the negotiation among different service classes and WSN resource allocations to reach the optimal operational status. Finally, the guarantees of the service quality are extended to the environment of multiple, disconnected, mobile subnetworks, where the question of how to maintain communications using dynamically controlled, unmanned data ferries is investigated