Research On The Integrated Transmission System Of Satellite Navigation And Communication

Traditional satellite navigation systems usually only provide users with navigation services,and their functions are simplistic.The integrated satellite navigation and communication system can provide users with navigation and positioning services and data communication services at the same time.Compared with traditional navigation systems,the integrated navigation and communication systems provide users with more comprehensive services,so satellite mobile Navigation communication integration has become a hot research direction.So far,almost all mainstream satellite navigation systems have deployed signals in the Lfrequency band.There are many coexisting signals in the L-frequency band,and the problem of interference between signals is more and more serious.Therefore,it is very important to seek new frequency bands to develop satellite services.The International Telecommunication Union allocates the Cn frequency band(5010～5030MHz)to the downlink signal frequency band for navigation services.This frequency band has been considered by many countries as a candidate frequency band for global satellite navigation systems.Therefore,this thsis designs a forward link(The ground station sends signals to the user terminal via satellite)and a reverse link(The user sends a signal to the ground station via satellite)integrated navigation and communication system,This thsis focuses on key technologies such as the modulation method suitable for the channel coding method of the system,the modulation method that meets the compatibility of the Cn frequency band and the constant envelope characteristics of the modulated signal,and the signal processing flow at the user terminal.The main contents of this thsis include:1)The overall design of the system is given,including: The protocol stack of the system is introduced,the frame structure of the physical layer of the data communication signal is designed,and the link budget of the forward link and the reverse link is completed.2)The design of the forward link signal system of this system is presented,mainly introduces the key techniques such as puncturing polarization code,spreading code optimization,and look-up GMSK orthogonal modulation method in the forward link signal system design.Under the background of this system,the performance simulation of each of the abovementioned key techniques has been carried out.Among them,the thesis proposes a coding and decoding scheme of punctured polarization codes with non-standard polarization code length suitable for this system.The simulation results show that this code has a larger coding gain compared with the commonly used LDPC codes in navigation systems.This thesis also proposes a look-up table GMSK quadrature modulation method.The simulation shows that the modulated signal can meet the out-of-band compatibility requirements of the Cn frequency band and exhibit constant envelope characteristics.Compared with the conventional GMSK modulation method,the calculation amount of this modulation method is lower3)The signal synchronization scheme design at the receiving end of the forward link and the performance simulation of each module in the scheme are completed.Firstly,the signal frequency offset at the receiving end of the forward link is estimated;then the PMF-FFT acquisition method,FFT frequency offset estimation,lock Performance simulation of different modules in the forward link signal reception processing flow such as phase loop steady-state tracking,frame synchronization,and bit synchronization.4)The signal transmission scheme design of the reverse link and the performance simulation of each module are completed.Firstly,the design of the reverse link signal system is completed,including the signal encoding method,the spreading code used,and the modulation method.Then the signal processing flow of the receiver of the reverse link is designed,and the performance simulation of each module are given.