Ant Colony Algorithm And Its Applied Research In Qos Multicast Routing

With fast development of network technologies, increase of network bandwidth and processing power makes the network provide more multimedia applications, and also makes the multicast communication that supports"one-to-many", or"many-to-many", become an necessary mode of multimedia services fundamental issue in multicast communication is how to determine an efficient multieast routing, and finding simple, effective and robust multicast routing algorithms is unsolved problem in network fields. In addition, many distributed multimedia applications have various demands on delay, delay variation, bandwidth and packet loss, which requires network to transmit real-time multimedia information with these Quality of Service(QoS) constraints. So, as an indispensable component in a QoS-centric network are hitecture,research on multicast routing algorithms based on QoS constraint becomes an important part and hotspot issue of network research fields.The characteristics of ant colony algorithm are distributed computing, positive feedback and constructive greedy heuristic. With inherent advantage such as robustness, parallelism of and easiness of combination with other heuristic algorithm, the ant colony algorithm is widely used to solve various different NP-hard problems in the last few years, which has empirically shown its excellent performance and huge potential of application in the fields of combinatorial optimization.This thesis concentrates on researching multicast routing algorithm based on ant colony algorithm with QoS constraints, applies an improved colony algorithm to solve QoS multicast routing problems with NP difficulty. If the appropriate parameters are selected in the ant colony algorithm, a rather optimistic performance can be obtained. A detailed research of the selection of parameters is carried out in ant colony algorithm, including theoretical analysis, simulation, and analysis of results. The method of the optimal combination of the parameters is brought forward.The ant colony algorithm is improved on in view of problem that its premature partial restrain and convergence. The new ant motion rules and mechanism of pheromone update are designed in the improved ant colony algorithm. A parameter of global best tour in strategies of pheromone strength updating is mainly presented. According to the judgment of a parameter of global best tour to dynamically update pheromone volatile factor and the transfer state factor, the algorithm ensures that global searching abilities are improved adaptively and avoid falling in local peak.The actual network model is researched in detail based on the analysis of applying the ant colony algorithm to solve combinatorial optimization problem. Improved ant colony algorithm is applied to solve the QoS multicast routing problem.Simulation results demonstrate that this algorithm is effective,feasible and steady for solving QoS multicast routing problem with multiple constrains.