Opnet Simulation Of Low Earth Orbit Satellite Communication System

Satellite mobile communication systems play a major role in military and civilian use and are an important part of information globalization,With the acceleration of the global integration process.Depending on their orbital altitude,satellite systems can be divided into geostationary orbit satellites(GEO),medium earth orbit satellites(MEO),and low earth orbit satellites(LEO),etc.Each satellite system has different spatial characteristics and network characteristics.The LEO satellite constellation mobile communication system has the characteristics of low delay and high throughput.The satellites establish connections t hrough inter-satellite links(ISL)to achieve global communication coverage,such as in mountains,deserts,oceans,etc.In the LEO satellite communication system,the satellite moves faster than the ground,the network topology changes frequently,and the terrestrial netw ork protocol is not suitable for the low-orbit satellite communication system.This paper mainly studies the design of low-orbit satellite constellation multiple access technology and routing addressing technology,the low-orbit satellite constellation orbit design based on STK and the low-orbit satellite simulation platform design based on OPNET.According to the motion characteristics of low-orbit satellites and the limitations of terrestrial network,a satellite adaptive time division multiple access protocol(SSAT)was proposed.The SSAT protocol utilizes the space advantage of the satellite to manage the time resources of the users under the stars,and the traffic channel and the control channel is combined,and the user reserves the channel resource in the idle time slot by using the parity access method.In this way,The SSAT protocol has higher access success rate and channel utilization than the traditional ALOHA slot reservation protocol.The multiple access protocol is responsible for controlling the link between the user and the satellite,and the routing protocol is responsible for the addressing of the data packets in the satellite network.Low-orbit satellites cover the globe through constellation networking,and satellites establish connections through Inter-satellite links(ISL).In the satellite communication network,there is a large propagation delay between nodes,and the satellite constellation keeps moving at a high speed,so the traditional mobile Ad-hoc Networks(MANET)is not Suitable for LEO satellite networks.The geographical routing protocol uses the location information of nodes for data forwarding,and has the characteristics of no link state control and distributed invisible forwarding.In this paper,geographic routing is applied to the LEO satellite constellation communication system,and a greedy routing algorithm based on minimum elevation angle is proposed.The source node queries the spatial location information of the destination node through the gateway,and the satellite performs data forwarding by searching for the satellite with the lowest elevation angle of communication with the destination node.