Research On OFDM Modulation And Channel Estimation Under The Satellite Channel

The concept of OFDM (Orthogonal Frequency Division Multiplexing) technology had been suggested in the 1950s. After decades of development and in-depth research, OFDM has become a technology that can be against the ISI effectively and ensure information transmit effectively. OFDM has some advantages like high spectrum efficiency, anti-multipath capability, high-speed information transmission, simple channel equalization and simple implementation, so it has been used in the fields of integrated wireless access widely. And with the development of DSP chip, high-speed modulation techniques like MQAM, trellis coding, soft decision and channel adaptive technology, OFDM has also been deeply used in the field of mobile communication.This paper has described the OFDM system under the parameters belonging to the S-band satellite channel and has made the independent study of some important issues. The first two chapters have introduced some basic information of OFDM, including its history, principles and application environment. The last three chapters are the main research results of this paper. The multi-path channel has been designed and modeled according to the parameters. Then OFDM symbol has been designed and OFDM system has been built. When it came to the OFDM symbol designing, pilot insertion format has been made specific discussion. The application of MQAM in the OFDM system has also been analyzed. The impact of frequency offset and phase noise also has been discussed. And the influence of phase noise includes constellation rotation and radiation. Channel estimation is also a key issue which has been studied carefully, including its acting on multipath, frequency offset, phase noise and white noise. All those studies has been simulated and verified based on MATLAB and finally a comprehensive study on those issues has been made. And the OFDM system has achieved the best optimization by using suitable data modulation scheme, choosing an optimal pilot insertion format and using the best channel estimation method.