Non-cooperative Digital Communication Systems, Group Delay And Phase Noise

With deep researches on wireless communications, non-cooperative communication draws more and more attention. Non-cooperative communication receivers access the system without being authorized while they can not disturb the normal operation of other receivers. Because non-cooperative communication receivers are unauthorized, they do not know the system parameters, such as modulation mode, symbol rate, carrier frequency. Therefore, non-cooperative communication receivers have to estimate these parameters by the received signals, and then they adjust these parameters according to multiple signal features for demodulation.In this paper, it studies the demodulation degradation for different modulation type signals of group delay and phase noise. A modified blind equalizer algorithm is proposed. Simulation results show that the new algorithm could compensate the group delay in transmission channel and reduce the bit error rate. And it also studies the algorithms of carrier recovery in non-cooperative communication system. Then, based on the cooperative working architecture of frequency sweeping and carrier recovering, a new fast carrier frequency estimation algorithm is proposed.From the second chapter to the fourth one of this dissertation, some researches on group delay and phase noise in cooperative communication system are done. In addition, a new carrier frequency estimation algorithm in real-time demodulation system is proposed.Chapter 1 gives a brief introduction of non-cooperative communications and the classical parameter estimation algorithms. Then, the background and the main work of this dissertation are introduced.Chapter 2 studies the carrier frequency estimation algorithm in non-cooperative communication system. Several carrier frequency estimation algorithms for real-time demodulation system are analyzed firstly, and then a new chirp Z transform(CZT) parabolic interpolation algorithm is proposed. Simulation results show that the new algorithm can improve the estimation accuracy of the carrier frequency without increasing much computational complexity.Chapter 3 investigates the influence of group delay on different modulated signals. Based on least mean square(LMS) rule, a new blind adaptive equalization algorithm is proposed. The new algorithm can compensate the distortion of the signal caused by group delay adaptively. The simulation results show that the performance of receivers is apparently improved.In chapter 4, the demodulation loss of MPSK signals caused by phase noise is researched, and the results are helpful for us to design the phase noise specifications for each part of a receiver.The dissertation is summarized in the Chapter 5. Finally, the future research work is also pointed out.