The Study On Some Key Routing Problems In Wireless Ad Hoc Network

Ad hoc network is a new kind of wireless network that does not rely on fixednetwork infrastructure. In ad hoc network, nodes can quickly build a communicationnetwork through a self-organizing way to achieve inter-node communication,information collection, information processing and information distribution. With adhoc networks, people make the dream possible to freely communicate in anyenvironment, as well as provide effective solutions for military communication, disasterrelief and temporary communication. In ad hoc networks, due to the constraints of nodetransmission capacity, distant nodes must adopt a routing protocol to exchangeinformation through multi-hop communication. The quality of routing protocol greatlyinfluences and even determines the performance of the ad hoc network. Therefore, therouting technology is a key technology of the ad hoc network, but also one hot spot oncommunication field of ad hoc network. since the proposed of wireless ad hoc network,the routing technology is always being a key technology of the ad hoc network, but alsoone hot spot on communication field of ad hoc network, widespread concerned by theresearchers.This dissertation takes depth study on some crucial and fundamental routingproblems in wireless ad hoc networks. These problems include modeling node mobilitymodel of wireless ad hoc network, performance analysis and improvement of routingprotocol for wireless ad hoc network, and new routing protocol design method andframework.Based on the study of these problems, we make some contributions which arelisted as follows:1. The dissertation proposes a node mobility model which is suitable forapplications to the region with multi-entrances. In ad hoc networks, the key study ofprotocols analysis and simulation is to choose a practical node mobility model. In thispaper, we propose an optimal and realistic node mobility model, Semi-Markov Smoothwith Entrances (SMSWE), which is used in the region with multi-entrances. In thismodel, the nodes definitely pass from one of the multi-entrances at the boundary of the region to enter the region, and then move according to the SMS in the region. Theresidence probability is introduced to decide the moving transform from interior toexternal of the region. SMSWE inherits fine-grained control to nodal movement fromSMS, also gives sufficient consideration to the influence of entrances. Theoreticalanalysis and simulation show that SMSWE model is more close to reality with smoothmobility and consideration of influence of entrances. SMSWE overcomes the defect thatnodes gather to the regional center in RWPWE. With SMSWE model, we can describeand simulate nodal mobility patterns and ad hoc network topology in the region withentrances better, and make more accurate analysis and evaluation to network protocols.2. The dissertation proposes a practical network-coding aware routing protocol forunicast sessions in wireless networks. The selection of routes is an important issue inwireless networks when network coding is used. Existing research formulatenetwork-coding-aware routing as a linear optimization program. However, deployingsuch method in real wireless networks is impractical. To solve this issue, in this paper, apractical network-coding aware routing protocol is proposed for unicast sessions inwireless networks. The protocol is based on a novel routing metric design that capturesthe characteristics of network coding and unicast sessions. To ensure the novel routingmetric can operate with practical and widely available path calculation mechanisms, aunique mapping process is used to map a real wireless network to a virtual network. Themapping process ensures that the paths with the biggest coding opportunities will beselected by commonly used path calculation mechanisms. Simulation results show thatthe proposed routing protocol is effective.3. A mathematical model is derived based on the the cached routing repairmechanism, and a route repair strategy for large-scale heterogeneous wirelessself-organizing network is proposed. Real-time applications in ad hoc networks requirefast route repair mechanisms to minimize the interruptions to their communications.Cache-based route repair schemes are popular choices since they can quickly resumecommunications using cached backup paths after a route break. In this paper, throughtheoretical modeling of the cache-based route repair process, we derive the optimalcache-based route repair policy. This optimal policy considers both the overhead of theroute repair schemes and the promptness of the repair action. The correctness andadvantages of our optimal policy are validated by extensive simulations. 4. The dissertation combines routing protocol design with genetic algorithms androuting algebra theory, and proposes an open network routing protocol designframework, called as Orchestra. Orchestra can fully reuse the working results of theresearchers related to routing protocol, which greatly improve working efficiency of therouting protocol designers and greatly simplify the design of routing protocols.Orchestra is also designed as a platform for the study and simulation of wirelessnetwork routing protocols with high openness and high compatibility. In the beginningof the framework design, to be compatible with the variety of existed routing protocolswidely deployed and used has been taken into account. Orchestra framework can helpresearchers to easily design and implement routing protocols, and also support someautomation work as follows: automatically test new modules, automatically combinedifferent modules developed by researches, and automatically find the optimum routingprotocol and operating parameters suitable for the current network status.