关键词: 服务质量, 单播路由, 双向搜索, 蚁群算法

Abstract: In recent years，the QoS routing of the network has been a focus.Considering the disadvantages of the existing algorithms，an improved ant colony algorithm is proposed in this paper and applied to the unicast routing with QoS constraints.The proposed algorithm has made some modifications in the pheromone updating rule，at the same time；it has combined the policies of network simplifying and bi-directional searching.The simulation results based on the comparison with other existing heuristic algorithms show that this algorithm has the advantages in terms of better global searching ability，higher convergence speed，and stronger robust.

Key words: Quality of Service（QoS）, unicast routing, bi-directional search, Ant Colony Algorithm（ACA）