Ad Hoc Network Routing. Multi-objective Optimization Selection Algorithm

Wireless Mobile Self-Organized Network namely Ad Hoc network is a non-central node, multi-hop, self-organization, energy-constrained network. The characteristics of the network make it face more secious challenges than traditional centralized network in routing. By the increasing of the network business, traditional single-goal routing algotithms are difficult to totally satisfy the needs of the Ad Hoc network. How to consider several optimization goals together and find out the optimal path in distributed wireless mobile self-organized network environment has become a focal point in wireless mobile self-organized network routing, and it is also the focal point of this paper.Aiming at the load-balancing problem in wireless mobile self-organized network, this paper raises a distributed and centralized selection combined, multi-objective optimal routing algorithm. Its main tasks include: (1) Compares the advantages and disadvantages of three multi-path algorithms (node-disjoint, link-disjoint and joint multipath). In some specific network environment, the number of node-disjoint paths is small and it is difficult to complete the objective of multpath. However, there are too many shared links in joint multipath, so, in this paper, we choose the link-disjoint method. At the initial stage of routing lookups, we try to find out several paths that are the shortest and link-disjoint. (2) By collecting back-to-back TCP packets passively, we use a link loss rate estimate algorithm which is suit to Ad Hoc network to compute the link loss rate. (3) At the stage of routing maintenance, the source node estimates the link loss rate periodically and uses link local-repair technique. When the source node finds a link whose packet loss rate exceeds the threshold, a new path will be found as possible as it can to replace the link according to the route information to other destination nodes which is recorded in the source node route table. (4) At the stage of flow distribution, the source node considers the packet loss rate of the paths as a measure of load and distributes flows to the paths according to it.Aiming at the load-balancing and secure problem in wireless mobile self-organized network, this paper raises a distributed multi-objective optimal routing algorithm. Its main tasks include: (1) Deeply studies in the theory of the ant algorithm and several dynamic trust models that are suit to Ad Hoc network and considers the load (link loss rate), secure (trust) and path hops as three optimization goals. It combines the ant algorithm and considers the load as the algorithm's pheromone, the countdown of the hop as the algorithm's stimulating factor and the secure as the algorithm's third parameter. It also sets wights for the three goals and the wight size determines the importance of the goal. (2) Selecting the route by the way of probability. When the algorithm runs, the nodes in the network create a probability table for each routing entry. The probability table contains the probability of the nodes that can be choosed as the next hop to the related destination node, and the value of the probability is determined by three parameters: the packet loss rate of the link which connects the current node and the related next hop, the trust level of the current node to the related next hop and the hop count of the related next hop to the destination. When the node receives a data packet, it sends the packet to the node which has the maximum probability to be the next hop in the probability table. (3) All nodes in the network update the trust level of the neighbor nodes of them and the packet loss rate of the links that connect the node to its neighbor periodically and then update the probability table.At last, we simulate the above-mentioned two algorithms using NS2. We compare the first algorithm to the DSMR which is expaned into multipath in traditional way from the DSR, the result shows our algorithm reduces the packet loss rate and the network overhead effectively. We alse compare the second algorithm to the AODV, the result shows our algorithm can balance the network load and enhance the security of data transmition by setting the weight of the goals appropriately.