Research On Load Balancing Routing Algorithm For Low-orbit Satellite Network Based On Ant Colony Optimization

In recent years,with the rapid development of the satellite and the carrier rocket technology,satellite network systems such as Low earth orbit(LEO)satellite systems are becoming a reality.Satellite networks can provide a wider service range and lower delay than traditional terrestrial optical fiber networks.Based on these advantages,LEO satellite networks can play an important role in the next generation Internet.Effective load balancing routing strategies for LEO satellite networks need to be designed,due to the bursty characteristic of the Internet traffic and the distributive feature of satellite links.Traffic-intensive areas often suffer from link congestion while links in other areas are underutilized,i.e.,the traffic imbalance problem in LEO satellite networks.Moreover,the fast movement of LEO satellites results in frequent change in network topology.At last,satellites are with limited computing power and energy.These factors make the design of LEO satellite network routing a real challenge.In this thesis,an Ant Colony Optimization Routing Algorithm with Window Reduction for LEO satellite networks,ACORA-WR,was proposed to achieve load balancing.In ACORAWR,we designed congestion-avoiding heuristic information and combined it with pheromone to improve the local search ability of ants and avoid stagnation.The pheromone update rule was also optimized based on path length and buffer status to improve the convergence speed to the global optimal solution.Furthermore,we designed a window-reduction mechanism to restrict the explore range of ants,which improved search efficiency and reduced the transmission overhead ratio.At last,ACORA-WR comprehensively considered the path distance,transmission direction and link load to find a path with low delay and overhead.The Iridium system is a mature and popular LEO satellite network system.We used the NS2 simulation platform to simulate an Iridium-like system and evaluate the performance of our proposed ACORA-WR routing algorithm.Simulation results verified that,compared with popular exisiting distributed algorithms,e.g.,LBRA-CP,LCRA,and centralized shortest path algorithms,the proposed ACORA-WR scheme demonstrated high data delivery ratio and network throughput,while ensuring low average delay and network transmission overhead.