An optimized ant colony algorithm based on the gradual changing orientation factor for multi-constraint QoS routing

The ad hoc network has been attracting increasing attention of researchers owing to its good performance and special application. The search of route that satisfies such multi-constraints as delay, jitter and bandwidth in ad hoc network can facilitate the solution to multi-media transmission. The problem of multi-constraint is generally an NP-Hard problem. This paper deals with the problem by adding an orientation heuristic factor to the conventional ant colony algorithm, which enables the ant to get rid of the blindness at the initial stage of path searching. The ant in the modified algorithm not only makes use of the previous search findings, but also reduces the misguiding effect of pheromones on the irrelevant paths, thus overcoming the problem of slow convergence. The choice and the extent of the effect of the orientation heuristic factor in the modified algorithm is our focus, and the gradual changing orientation factors is also studied. The gradual changing orientation factor not only enables the ant to take advantage of direction to assist path search, but also adjust convergence speed and exactitude. Simulation results indicate that the modified algorithm can quickly find the feasible solution to the network routing problem. The method adopted can help find better solutions in shorter time.