Channel Estimation And Equalication Technology Research Of Broad Band Satellite Communication System Based On OFDM

Satellite communication has an irreplaceable role in many aspects,such as emergency communications,maritime communications,forest monitoring and so on.As an important complement to terrestrial communications network,Satellite communication developes overall towards high-capacity,high-power,high-speed,broadband and low-cost direction in recent years.Ka-band has become the main direction of development of broadband satellite communicationswith its wide bandwidth,high-capacity advantages.As a key technology of the fourth-generation mobile communications,Orthogonal Frequency Division MultiplexingTechnology(OFDM)has received a large number of commercial applications in the field of terrestrial mobile communications with its advantages of large capacity,high data transfer rate and resistance to multipath fading.While the current traditionaltransmission means of TDMA,FDMA and CDMA can provide a temporary solution for users to communicateln certain situations,it can't meet the needs of high-speed data transmission in the next generation of broadband satellite mobile communication system.In this view of point,it is a good solution to adopt OFDM technology in satellite communication,Its advantages can solve the problem of signal transmission of broadband-satellite links and gets better integration with terrestrial networks in the futureSignal transmission will be affected by atmospheric effects,multipath fading,shadowing,and other environmental impactsthrough the satellite channel.Channel estimation plays an important rolein recovering the information transmitted by transmitter through satellite channel.Channel estimation is to estimate the frequency or time domain channel impulse response,so as to minimize the impact of multipath channel,shadows,and the noise on the signal and recover the received data better[7]-[8].This paper focuses on channel estimation based on pilot.Since OFDM is a multi-carrier transmission system,the channel has an impact on signal in both time and frequency directions,therefore the channel estimation needs to be carried on in two dimensions of time and frequency.This thesis proposes a method of OFDM satellite channel estimation based on the concatenation of Wiener filter and Kalman filter,consideringthe characteristics of Ka-band satellite channel.The main idea is to estimate the pilot channel informationin time direction by Wiener filter at first,then make a second estimation by kalman filter to make the estimation preciser,finally gets all the channel information by linear interpolating in frequency direction.The simulation results indicate that,compared with the traditional LS estimation method and Wiener filter estimation method,the new method can get more accurate estimation and lower BER.