Author : Roméo Said
Publisher :
ISBN 13 :
Total Pages : 111 pages
Book Rating : 4.:/5 (758 download)
Book Synopsis Middleware for Service Provision in Disconnected Mobile Ad Hoc Networks by : Roméo Said
Download or read book Middleware for Service Provision in Disconnected Mobile Ad Hoc Networks written by Roméo Said and published by . This book was released on 2011 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mobile ad hoc networks (MANETs) are spontaneously formed out of a number of mobile devices that communicate thanks to short-range wireless communication capabilities (e.g. Wi-Fi, Bluetooth). In many ad hoc networks deployed in real conditions, mobile nodes can exhibit highly dynamic behaviors of mobility and volatility. Because of their behavior, the devices in such network environments form so-called "islands" whose topology evolves continuously, rather than a single fully connected network. In this work, I focus on this class of MANETs which I refer to as disconnected MANETs. Network-wide communication in disconnected MANETs is still a challenge, namely because routing techniques designed for fully connected MANETs cannot be applied. The store-carry-and-forward approach provides a solution. With this approach, a message can be stored temporarily on a node, in order to be forwarded later when circumstances permit. Mobility then becomes an advantage as it facilitates message propagation. Messages are therefore forwarded from one network node to another when these nodes have the opportunity to meet. The service-oriented computing (SOC) model seems suited for ad hoc environments because it emphasizes the decoupled nature of its entities. Effectively, the decoupling between a client entity and a provider entity becomes essential in mobile environments with a fluctuating availability of providers, and where end-to-end communications are not guaranteed. Still, in existing service-oriented systems, providers are usually supposed to be always available (e.g. Web services). Providers are also assumed to be continuously reachable in wireless mobile environments, where local connected networks can be created using Wi-Fi hotspots, or by creating ad hoc networks using proximity one-hop or routed multi-hop protocols. Therefore, implementing distributed services for such networks still poses several challenges. Not only network-wide communication features must be provided, in spite of constant network fragmentation, but aspects such as the unpredictable reachability of the providers, or potential communication delays, must be taken into account at the service level. I propose a service platform for mobile nodes that supports the execution of service-oriented applications in disconnected MANETs. The service platform is implemented as a middleware composed of two layers: a communication layer, and a service layer. The communication layer provides mechanisms to decouple two service entities in terms of temporaneous interaction, synchronous behavior, and mutual knowledge. For this layer, I use an opportunistic and content-driven protocol (DoDWAN). The service layer provides mechanisms that decouple service providers and clients in terms of interoperability and service contract. For this layer, I propose solutions for service discovery and invocation. The elements that construct the discovery protocol are the description and advertisement at the provider side, and collection and selection at the client side. Description uses functional and non-functional service properties, as well as context properties. Discovery is based on a peer-to-peer architecture, where a client collects only interesting services. Content-based invocations are used to benefit from the service replication, where a multitude of providers can be offering the same business service. A client creates a functional request according to a discovered provider, then publishes its content-based request message to the attention of all compatible providers. After being satisfied, the client can initiate the healing of residual request and response messages from the network. The healing of response messages can also be initiated by the providers themselves according to the reliability of these responses. Using a prototype implementation of the middleware, I conducted simulations in a disconnected MANET environment. The performances of discovery is directly related to those of the underlying communication layer. Simulations confirm the benefits of content-based invocations in providing faster response times and better client satisfaction. Simulations also show the drastic reduction of redundant and leftover messages when applying the healing mechanisms.
