Research On Nosie Characteristics And Noise Mitigation Technology In Low Voltage Power Line Communication Channel

Communication network is an important infrastructure to ensure the safe and stable operation of power system. Due to the wide coverage of the power line and economical advantage, power line communication system (PLC) has gained attention. However, the power line communication channel has a large amount of noise, which seriously affects the reliability of power line communication. Because its randomness, the high noise intensity and non-Gauss distribution, the asynchronous impulse noise is the most serious damage to the power line communication system. Therefore, in order to improve the reliability of power line communication system, this paper study the power line communication channel noise characteristics and the technology of noise mitigation.Firstly, the noise characteristics and noise models of power line communication system are studied based on the measured power line communication channel noise in this paper. Power line communication channel is a typical noisy channel, which contains a large amount of noise, and the emergence of impulse noise causes the communication system long burst error. That shows that the power line communication has the limited memory property. Therefore, in this paper, for the memory characteristics of power line communication channel, the memory characteristics of the power line communication channel is studied. In the study of memory characteristics, the most important parameter is the memory order. Hence, in this paper, we use the power line channel multipath model and information theory to prove the first order Markov characteristics of power line communication channel. And according to the measured OFDM signal, we establish the first order and second order AR model. Based on the comparison of the model parameters, it is proved that the power line communication channel has a general first-order Markov properties.Then, the Time Frequency Peak filter (TFPF) is proposed, and the performance of the Time-Frequency Peak Filtering Algorithm in power line communication system is studied. First, the TFPF is introduced. Then, the performance of the Time-Frequency Peak Filtering Algorithm in power line communication system is studied under the different noise environment. The simulation experiment although shows that the time frequency peak filtering algorithm has good effect on the background noise in power line communication, but it can not play a good effect on the impulse noise environment.According to these cases, the Normalization Time Frequency Peak Filter (NTFPF) is proposed. Before filtering, the signal is normalized, which has the effect of suppressing the impulse noise. In the NTFPF, the normalization parameter is vary important. Considering parameter selection plays a vital role, the effect of normalization on signal is studied, and a normalized parameter selection based on signal amplitude is proposed. In view of the practical application, the Pre-estimation Normalization Time Frequency Peak Filter (PE-NTFPF) is proposed, which is based on the pre estimation of the Time-Frequency Peak Filtering. The simulation results show that the method can have some effects in low impulse noise intensity..However, in the power line communication system, the Environment is complicated and changeable. The PE-NTFPF is not stable in this environment. Therefore, in this paper, the Adaptive Normalization Time Frequency Peak Filter (ATFPF) is proposed. The signal to noise ratio (SNR) can be changed after signal normalization by using different parameters. Hence, The parameters can be selected based on the SNR. The simulation experiments show that the adaptive normalized parameter selection method can improve the adaptability of the time frequency peak filtering algorithm, and can better adapt to the changing environment of power line communication system. Moreover, the algorithm has better effect of eliminating noise, improving system reliability and reducing error rate.