Research On The Clock Synchronization And Self-calibration Technology Of Satellite MF-TDMA Network Based On Terminal Location

MF-TDMA(Multi-Frequency Time Division Multiple Access)satellite communication is a new type of broadband VSAT network(Very Small Aperture Terminal System)developed on the basis of the TDMA(Time Division Multiple Access)technical system.It has large communication capacity and propagation distance.It is the mainstream system adopted by the current broadband multimedia satellite communication system,it has been widely used in military,civilian,medical and health,emergency rescue and other fields in recent years.In the basic construction of the MF-TDMA satellite communication system,the clock synchronization technology is one of the necessary conditions for applications of satellite communication,and the accuracy of clock synchronization will directly affect the quality of its communication applications,which is the practical significance of the research in this thesis.The ETSI EN 301 790 V1.3.1 protocol puted forward the clock synchronization principle of DVB-RCS(Digital Video Broadcasting-Return Channel Satellite)interactive satellite communication system,that is,the master station encodes and broadcasts NCR(Network Clock Reference),and each terminal calculates the deviation value of the master-slave according to NCR and adjusts the local clock,so as to realize the clock synchronization of the whole network.This thesis summarizes the latest research progress of clock synchronization technology at home and abroad,and studies the implementation of the MF-TDMA system clock synchronization based on the principle of DVB-RCS system clock synchronization.Research the communication system of MF-TDMA,mainly including the system organization structure,the organization of the return link resources,etc,and analyzes the common clock synchronization methods and the clock synchronization principle of DVB-RCS system,the terminal access process,the synchronization maintaining process lay a foundation for the study of the MF-TDMA satellite communication system clock synchronization technology for the entire network.Research the implementation scheme based on the MF-TDMA satellite communication system clock synchronization of the entire network,and introducing the inroute frame fine calibration program to correct the synchronization error caused by the link transmission delay,and improve the synchronization accuracy.In the scheme,the influence factors such as: transmission delay of timing synchronization frame,the difference between the crystal oscillator frequency of the master station and the terminal,and the relative movement of the satellite are taken into account.The error analysis is carried out,and using the terminal self-calibration to compensate clock error under these influence factors.Finally,the simulation verifies the feasibility of the clock synchronization scheme.Considering the influence of clock frequency offset on synchronization accuracy,a clock frequency offset compensation technique for satellite communication based on gradient descent method(GDCS)is proposed.Aiming at the phase offset of the time value difference and the frequency offset representing the speed of time caused by the characteristic of the clock crystal oscillator,the clock synchronization solution introduces a clock frequency offset prediction and compensation mechanism to synchronize the clock frequency offset and phase offset of the terminal,and the performance of least square algorithm and GDCS algorithm are compared through simulation.