Research And Verification Of Wireless Signal Synchronization And Equalization Technology For 800mbps Satellite-to-Earth Communications

The low-orbit satellite-to-earth mobile communications gradually shifted from providing voice message services to broadband Internet access services.To meet the demand for broadband services,Ka-band satellites began to be applied to satellite-to-earth mobile communication systems by using OFDM technology.Low-orbit satellites move fast and the channel conditions are relatively complex,which restricts the development of broadband low-orbit satellite communications.In order to overcome the influence of Doppler frequency shift,multipath effect and shadow fading,the paper studies the time-frequency synchronization and channel equalization techniques which is suitable for Ka-Band satellites mobile communications.The main contents are as follows:Firstly,the paper introduces the satellite-to-earth propagation environment and establishes a satellite-ground channel model,then investigates the synchronization and equalization techniques suitable for the application scenario.The channel model consists of Ka-band satellite channel statistical model,Doppler frequency offset,multipath effect,shadow fading,and AWGN channel.In synchronization algorithm,the auto-correlation and cross-correlation time synchronization algorithms are introduced,self-synchronization and external synchronization methods are investigated;in equalization algorithm,the time domain equalization and frequency domain equalization algorithms are described.Secondly,based on the research details of synchronization and equalization techniques,the synchronization and equalization algorithms are designed for communication link parameter requirements,then the algorithms performance is simulated to verify theoretical performance.In the time-frequency synchronization algorithm,the time synchronization algorithm consists of the auto-correlation and cross-correlation algorithms,a frequency synchronization algorithm combines with differential correlation and FFT frequency synchronization.DFT interpolation algorithm is used in channel equalization algorithm.Under AWGN condition,the timing error of the time-frequency synchronization algorithm is lower than 8 sampling points and frequency offset deviation is lower than 1% of the subcarriers;the performance loss of the channel equalization algorithm is about 1.3 dB.Finally,using the software defined radio platform to design and verify the synchronization equalization algorithms.The paper implements the algorithms by using FPGA chip,which completes with the module division,scheduling,sub-modules design,timing and resources optimization.Tests show that the timing synchronization error is less than 8 sampling points,the frequency synchronization error is less than 2% of the subcarrier bandwidth,and performance loss of channel equalization is about 2.3dB,which can meet the project requirements.The paper designs and implements the synchronization and equalization techniques in low-orbit satellite-to-earth ground mobile communication system.The research results are verified through engineering implementation,which can provide reference for the design of broadband low-orbit satellite communication systems.