Hfc-catv Network Uplink Channel Noise Characteristics Analysis And Study On Anti - Interference Technique

The noise characteristics and the anti-interference techniques of the HFC-CATV upstream channel are studied in this thesis. Firstly, the noise "funnel effect" phenomenon is analyzed and the sources, the cause and the characteristics of the noise interference in the HFC network are discussed. Secondly, based on the related mathematical formulas and physical laws, the noise models of the upstream channel are set up. Then, the effects that the noises in the upstream channel have on the QPSK and 16QAM modulation techniques are studied. The simulation results show that the more frequently the impulse emerges or the greater the energy of each impulse, the more obviously the bit error rate degrades . The characteristic function of the narrow-band continuous wave interference is the same as that of gaussian white noise, so the shapes of their bit error graph are the same. With the increase of the Eb/N0, the bit error rate declines quickly, but with the increase of the number of the narrow-band continuous wave, the performance on the bit error rate degrades greatly. The study results have shown that the anti-interference performance of the QPSK system is better than that of the 16QAM system. Finally, The S-CDMA and the adaptive nonlinear filter techniques are used to restrain the impulse interference and the narrow-band continuous wave interference.