A High-Performance Blind Tracking And Detection Method For OFDM Satellite Signal

OFDM is a high-speed transmission technology based on the orthogonal sub-carriers transmission, which can increase the spectrum efficiency of communication systems. The Fast Fourier Transform(FFT) Algorithm and sophisticated integrated circuits technology promote OFDM from theory to engineering applications. In recent years, OFDM has been widely employed in different kind of communication scenarios.Since OFDM modulation technology has good ability of anti-multipath fading, it is also widely used in the wideband satellite systems for high-speed transmission. In order to get higher spectrum efficiency and data throughput of the system, the new form of OFDM system without the cyclic prefix and the comb-type pilot is proposed. Thus, it requests novel frequency synchronization and signal equalization scheme to new form of OFDM system. There are several issues for the new applications. Firstly, how to accomplish synchronization without data aided, which guarantee the orthogonality of subcarriers and system performance. Secondly, how to compensate residue carrier frequency offset which can cause the rotation of constellation. Thirdly, how to implement blind tracking for signal with non-data aided in the time-varying channel.Based on above urgent demands, in the first place, this thesis proposes a frequency offset estimation method for the OFDM system without CP and comb-type pilot based on the relationship between the deviation amount of samples and the sampling frequency offset in transmitter and receiver. The thesis also analyzes the applicable conditions and estimation error for the proposed method. Secondly, the thesis introduces a method to obtain the optimal samples based on Lagrange’s interpolation for the sampling frequency synchronization. The method to calculate the initial value and the step size of fractionalspace is also provided. Thirdly, the thesis analyzes the influence of residue carrier frequency offset for the superframe-structured OFDM signal, and use blind equalization algorithm such as MCMA, DD to compensate phase offset without data aided. Finally, the thesis introduces several methods to track and equalize amplitude and phase variation in time-varying Rice channel for the new form of OFDM system.This thesis uses the simulation signal with specific format and practical data of iPSTAR system to test the proposed methods. From testing results, it can be found that the proposed blind tracking and detection scheme has good performance for the new form OFDM system, which can achieve synchronization and signal demodulation correctly on the condition of low SNR.