Random/Fixed Hybrid Multiple Access Algorithm For Space-sky Information Networks

With the popularization of the application of satellite data communication services,single satellite-working mode can not meet the exponential growth of the data transmission needs,the Aerospace Information Network based on multiple platform structure came into being.Information Network's special environment makes each terminal node be in the real-time state of motion,therefore the intermittent network connectivity.So it is of great significance to study the multiple access protocol based on multiple platform network communication.Moreover,a data access with low delay and high efficiency is also the necessary guarantee for the current emergency incidents' response and the establishment and promotion of the air base station communication service in the future.S-ALOHA random multiple access protocol is relatively flexible.When the terminal wants to send data,it can be sent at the beginning of the slot,which is suitable for the data transmission with relatively strong burst under multiple platform network environment.But when the network load increases,the throughput of data transmission will be fierce decline.Delay capture mechanism S-ALOHA multiple access algorithm is based on the S-ALOHA,although its performance index has improved compared with the S-ALOHA,its access success rate still decline seriously or to 0 when the network load is heavy,so it can not meet the business requirements of aerospace time-varying network.In summary,two improved algorithms based on S-ALOHA random multiple access protocol are proposed in this dissertation.In this dissertation,by analyzing the difficulties of using S-ALOHA multiple access protocol in the multiple platform aerospace network communication environment,and starting from data access process,it designs a multiple access algorithm based on reservation mechanism.The algorithm uses slot reservation mechanism based on different transmission rates,instantaneous power increase mechanism,joint delay-power capture mechanism and uniform back-off mechanism,considering the influence factors of Rician fading channels,the reservation mechanism algorithm model and working flow chart is established based on space information network environment,and the algorithm derives the expressions of the average transmission delay and access success rate.Through experimental simulation,the consistency between algorithm principle and formula deduction is ensured.Under the real-time changing network topology environment,the access success rate and average transmission delay characteristic of data transmission have been improved.At the same time,it isconsidered that the access success rate of the reservation mechanism multiple access algorithm falls seriously in the case of heavy load or even 0.the spread spectrum mechanism is added to the original reservation mechanism algorithm,and the basic model of the hybrid multiple access protocol algorithm based on spread spectrum mechanism is designed,and the corresponding expression is derived.Simulation results show that the access success rate of the algorithm is also improved compared with the reservation mechanism algorithm.After this dissertation compares the reservation mechanism and the spread spectrum mechanism multiple access algorithm from different aspects,and gives the different application scenarios of the two algorithms models,on this basis,according to the satellite constellation constructed by STK software,the actual access model of an aerospace multiple platform structure networking environment is simulated,and the reliability of the two access algorithms is verified.