The Scheme Design And Simulation Of The Satellite Mobile Communications System On MF-CDMA/CWTDM

This thesis studies the MF-CDMA(Multi-frequency Code Division Multiple Access) multibeam satellite mobile communication system based on CWTDM(Continuous Wave Time Division Multiple). The MF-TDMA system based on CWTDM despreads the signal onboard without demodulating it, then transforms the signal into CWTDM form and the downlink signal uses a direct spreading method. It can decrease the noise accumulation between uplink and downlink, the volume and power of mobile stations, and the complexity of the onboard processing transponder, and it also can increase the ability of anti-intercepting and anti-interferance . Therefore, it's great importance to study its applications of such satellite systems.This thesis mainly deals with the joint technology of CWTDM and onboard despreading. The main contributions of this thesis are as follows:1. A scheme of MF-CDMA multi-beam satellite mobile communication system based on CWTDM is proposed. The scheme take both the advantages of FDMA and CDMA, and can decrease the complexity of the onboard processing for there is no onboard demodulation processing..2. A detailed analysis of the principle and process of the uplink is given, include of coding, spreading and modulate techniques.3. A thorough study is made on key techniques of onboard processing, such as polyphase array FFT demultiplex technology, CWTDM multiplex/demultiplex technology, CWTDM frame synchronization and the synchronization catching of spreaded signal.4. Matlab/Simulink simulations of the CWTDM multi-beam satellite mobile communication system uplinks have been made, and the BER curve of the uplik is given.