Research On Key Technologies Of Uplink For Satellite Mobile Communication Based On LTE

With the rapid development of global broadband mobile communication,it is of great significance to construct high-speed broadband network covering the whole world.Long Term Evolution(LTE)technology has matured,and it can provide users with high-speed broadband network services,but it has not yet been deployed in some remote areas.Satellite communication system can achieve global coverage,but most of the current satellite communication systems are narrowband,whose data transmission rate is low.Therefore,it is important to combine the advantages of LTE technology with satellite communications.However,satellite communication has many problems,such as long transmission delay,large Doppler frequency shift,high dynamic,power amplifier nonlinear distortion,which bring challenges to the application of LTE to satellite communications.For example,the long transmission delay leads to the lag of the relevant information,which affects the timeliness of the relevant processes.The traditional frequency synchronization algorithm can’t make an effective estimation of the maximum Doppler frequency shift in the Low Earth Orbit(LEO)satellite environment.The impact of these problems on the uplink of the satellite mobile communication system based on LTE is unavoidable.Therefore,it is of great significance to study the uplink technology of satellite mobile communication system based on LTE.In this dissertation,the random access and frequency synchronization technologies of uplink in the satellite mobile communication system based on LTE are deeply studied.Firstly,the existing problems and development status of the satellite mobile communication system based on LTE are introduced.The research status of random access and frequency synchronization technologies are analyzed in the satellite mobile communication system based on LTE.Secondly,the satellite channel model is established and the LTE uplink transmission model is analyzed.Thirdly,the LTE random access procedure and the traditional preamble sequence detection methods in LTE random access are introduced.Aiming at solving the problem of multiple access interference when many users initiate random access process at the same time in the Geostationary Earth Orbit(GEO)satellite environment,a new LTE preamble detection algorithm based on serial interference cancellation(SIC)is proposed in random access process.Compared with the traditional detection algorithm,the SIC algorithm reduces the probability of missed detection and improves the success rate of satellite random access process.Then,according to the influence of Doppler shift on the peak size,position of the random access preamble correlation detection,this dissertation proposes a rough frequency estimation algorithm,which can realize the frequency preliminary estimation in the random access process when ground terminal initiate access satellite.Finally,in order to solve the problem of large Doppler frequency shift range in LEO satellite communication system,a Maximum a Posteriori estimation based on Doppler characterization algorithm for Doppler frequency shift estimation in satellite LTE uplink is proposed.This algorithm has a greater range of frequency offset estimation and higher estimation accuracy.