Research On FSO Directional Routing Based On Ant-Colony-Optimization

Because of the high bandwidth,rich spectrum resources,high confidentiality,flexible networking etc.,free-space optical communication(FSO)is widely used in military and civilian fields.Whereas,the topology of the networks changes from time to time,also accompanied with the various link state,current network routing technology can not meet the requirements of the mobile FSO networks.In this paper,in conference to traditional wireless directional routing technology,we make the direction massage as routing information and take advantage of the ant colony optimization algorism on multiple objective function optimization problem.Based on this,we propose a routing algorithm,ant-colony-optimization-based directional routing(ABDR),for FSO-MANET.We study the characteristics of the ant colony routing technology and the directional routing technology,and compare their advantages and disadvantages.Making the point-to-point link characteristic as the breakthrough point,we analyze the difficulty of the present routing and put forward the corresponding resolve solutions.Based on YG graph,we initialize the network topology,then divide the routing process into three steps according to source routing: route discovery,route selection and route maintenance.In the routing discovery phase,in order to reduce the routing overhead,we use half flooding method and design corresponding ant packet.Meanwhile,we introduce path different degree increment,and set upper and lower for pheromone concentration to prevent local excessive accumulation.In the route selection phase,the principle of “maximum pheromone” is adopted.In the routing maintenance phase,we use global and local updating to expand the search space and improve the speed of convergence.In order to improve the robustness of the algorithm,we also maintain a kind of local neighbor table to provide cache and recovery mechanism.Finally,we reasonably set the parameters of the simulation model by experimental and empirical methods.We verify the rationality of topology by MATLAB.Then by NS2,we simulate and verify the performance of different routing metrics,such as data delivery rate,end-to-end average delay and the first packet arrival time.The comparisons with AODV and DSR are also made.The result shows that high data delivery rates are obtained in a fast moving environment at the cost of a certain delay.The ABDR algorithm is effective and feasible.