Research On Reliable Service In Wireless Ad-hoc Networks

In modern society, computer networks are widely used. Computer software and hardware not only function on one single machine, but gradually becoming available in a distributed computing environment, which have been playing an important role in both academia and industry. A wireless ad-hoc network (WAN) is a wireless network with distributed, uncentralized and dynamic topology. It is infrastructureless, so as to be easily organized, and able to provide computing power and network accessibility to the users. A WAN is usually comprised of a set of independent wireless devices, and supports the cooperation of the intermediate nodes to achieve a peer-to-peer dynamic interconnection. In regions where no fixed infrastructures are available, such as business, military and disaster relief scenarios, WANs have broad application prospects.In WANs, it is not enough for the nodes to cooperate on the data transmission tier to accomplish the network interconnection, cooperation on application tier is also needed to enhance the ability of the entire network as the resources and functions of a single node are always limited. Service technology provides a proper and important technique for the abstraction and universal interface of the heterogeneous resources held by the independent nodes in WANs. However, the uncentralized and dynamic topology of WANs yields a huge challenge to the reliability of the services. How to deploy reliable services in the complex and changeable WANs is of great value from the aspects of theory and application.This thesis presents a definition of the reliability of services, and studies how to guarantee the reliability of the services from the service life cycle aspect. We discuss approaches for reliable service discovery and selection, strategies for service recovery, and methods to guarantee the credibility of services. The main contribution of this thesis includes:First, we propose a "Service-Magnetic-Field (SMF)" based service discovery protocol. This protocol allows service requesters (service consumers) to discover and selects more reliable services, and is of high efficiency and scalability.Next, we focus on the possible failures or exceptions in the process of service execution and present two service recovery approaches, one is based on the backup strategy, and another is an extension on the basis of the SMF protocol.In the end, we propose a reputation-based credible service model for WANs. We discuss the conversion from the reputation space to the trust space, and propose a credible service evaluation algorithm basing on a reputation and trust model. Additionally, some core issues are also analyzed in this thesis.