Research And Implementation Of Satellite Network Routing Protocol

With the wide coverage and being immune to geographical conditions on Earth,satellite network has become an effective means to provide communication service in areas where terrestrial communication facilities are not available.In addition,the satellite network is also an important means to provide emergency communications when the major natural disaters happen.In recent years,many countries and companies have proposed to build new generation of satellite networks,which arouse the upsurge of the research and construction for satellite networks.Routing protocol is the key to the efficient operation of satellite network.However,since the satellite network is featured for the fast topology changes,the large scale variation of link delays,the high link-failure probability,the limited node resouce volume and dynamic change of service load,it is quite challenging to design efficient,reliable and adaptive routing protocols.Topology discovery and routing construction is an important part of the routing protocol,which directly affects the function and efficiency of the routing protocol.In this paper,topology discovery and adaptation to traffic change in satellite networks are studied,The contributions of this paper are listed as follows:Firstly,because the nodes in the satellite network are always in high speed motion,and the difference of the speed of different nodes,leading to connections between nodes change constantly,always in a rapidly changing network topology.Therefore,Therefore,the dynamic topology discovery and maintenance of satellite network is difficult.At the same time,the topology discovery and maintenance algorithms of the existing routing protocols are directly applied to the satellite network,which leads to the problem of high signaling overhead and low link utilization.Aiming at the problems above,a topology discovery and maintenance algorithm based on prediction is proposed.The algorithm realizes the dynamic topology discovery and maintenance function of any satellite network and maintains the lower signaling overhead.by introducing the link mechanism and the adaptive hello message sending mechanism.Secondly,the distribution of the service carried by the satellite network is not uniform and is dynamically changing.It is easy to make the load of some part network too heavy load and load of other part too light which only relies on the shortest path to construct the route,resulting in the degradation of the network performance.Therefore,the load and traffice of the network are taken into account in the route construction procedure.The reinforcement learning mechanism is used to dynamically perceive the traffice of the network,and a satellite network routing algorithm based on Q-learning is designed.In this algorithm,the Q value is used to estimate the change of the network path cost due to the traffice transmission,and the transmission path of the datagram is dynamically adjusted according to the network traffic volume,resulting in improved transmission efficiency in the network.The algorithm adopts the time aggregation graph to initialise the estimated Q value and adjust the estimated Q value when network topology is changed.With this,the network looping resulting from link failures can be prevented and the occurrence of route concussion caused by network topology change can be avoided.In the algorithm,the residual buffer is introduced as a penalty factor,which could help to realize the load balancing and congestion avoidance in the satellite network,improving the performance of the network.Finally,a routing protocol simulation platform of satellite network is desigend and implemented in this paper.This platform is consisted of three subsystems,the link simulation system,node simulation system and the performance evaluation system.Based on the two algorithms proposed in this paper,a distributed routing protocol for satellite network is implemented in this testbed.Several testing scenarios are designed and constructed on the simulation platform to test the functions and performance of the propsoed routing protocol.