Research On QoS Routing Technology In Mobile Ad Hoc Networks

A Mobile Ad Hoc Network (MANET) is an autonomous multi-hop system of mobile nodes connected by wireless links without the support of static infrastructure such as base station. Each node in an Ad Hoc network can work as a router. With the characters of distributed operating, dynamically self-organized and self-configured, Mobile Ad Hoc Networks have good applied perspective in such fields as military applications and urgent rescue. However, the traditional protocols such as OSPF, RIP in wired networks cannot be used in such a dynamic changed network. At the same time, because of the limited energy, small size of memory and weak computing ability of the mobile nodes, the routing protocols used in Ad Hoc networks should be as possible as simple and efficient. But to design such protocols is very difficult. Therefore routing algorithms and protocols are hotspot in current research on Ad Hoc networks.Multipath means build multi paths between original and destination according to some rules, which can realize rapid routing by reasonable distributing traffic among different paths or being restored paths. There are some advantages by using multipath in Ad Hoc networks. First of all, Ad Hoc network dynamic topology architecture makes paths breakout continually. Multipath can start restored paths or redistribute traffic among other paths other than rebuild route that reduce the delay and package lost. Secondly, multipath can distribute traffic reasonably solve the problem of limited transfer bandwidth of Ad Hoe network. At last, multipath can use multi sub-optimize path to share the load of single optimize path which can efficiently reduce network congestion and distribute network resources reasonably.Multicast can efficiently decrease network and server loads and improve transfer capability. Since wireless Ad Hoc network needs multi-to-multi exchange and highly cooperation among each end, multicast will play a more and more important role on wireless Ad Hoc network. For example, multimedia communication and some other application with bandwidth limitation need effective multicast services. Meanwhile, multicast is an important way to enhance the working efficiency.With the development of Ad Hoc networks, the demands of providing QoS (Quality of Service) support for some real-time traffic in a dynamic, multi-hop environment is another research hotspot in Ad Hoc networks. The stability of the route is the foundation of the QoS routing. Entropy is an effective metric to denote the routing stability. The smaller the route entropy is, the steadier the route is.Ant Colony Optimization algorithms are one of the most successful biologic optimization algorithms. Positive feedback, distributed computing and hierarchical search have become the hotspot in the fields of intelligent optimization and been widely used in solving combination optimization problems.In this dissertation, based on summarizing previous research, a systematical and in-depth study has been done in solving the problems of QoS routing in Ad Hoc networks by using ant colony optimization algorithms.1) Ad Hoc multi-path routing algorithms based on ant colony optimization algorithmThis dissertation points out an algorithm named ADAR and its improved one, ADAA. ADAR is a way to build multi-path routing by demands based on ant colony optimization algorithm, which decreases congestion frequency and end-to-end delay. This algorithm updates the pheromone by local and global updating rules to enhance updating efficiency, highly cuts down the cost to re-find the route and route exchange, which chooses route and balances communication load by bottleneck bandwidth and delay. Simulation experiments show it is better than traditional single path protocols. Considering the relativity among multi-paths, ADAA builds up multi-path routing with uncorrelated nodes. Simulation experiments display it is better than ADAR.2) Multi QoS constraint routing algorithm based on ant colony optimizationStudying the math model of multi QoS constraint routing and using ant colony optimization algorithm, this dissertation points out an algorithm named AAMQ, which uses ant colony optimization algorithm to solve multi QoS constraint problems in Ad Hoc. This algorithm considers some QoS metrics such as node battery energy, link bandwidth, delay and packet lost rate. Furthermore, it also uses entropy in the pheromone global updating rule, which can display routing stability. Simulation experiments prove this algorithm has good capability on multi QoS constraint problems.3) Ad Hoc multicast routing algorithm base on ant colony optimization algorithmThis dissertation points out an algorithm named MARA for hybrid structure, which is improved from typical multicast routing protocol ODMRP based on mesh by ant colony optimization algorithm. The improved algorithm MARA considers some QoS metrics such as link expiation time (LET), delay, link bandwidth and node surplus energy. Simulation experiments testify this algorithm improve nodes capability and have better performance than ODMRP.This dissertation is supported by National Natural Science Foundation of China (No. 60172035, 90304018), Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20060497015), NSF of Hubei Province of China (No.2004ABA023).