Research On Noise Suppression Technology Of Medium-Voltage Power Line Communication System Based On Multi-Carrier Modulation

The quality of medium voltage power line communication(MV-PLC)is seriously restricted by the complex noise interference.In this channel environment,there is a lack of anti-interference ability and anti-noise measures for the traditional OFDM system.That makes it imposible to exploit OFDMs theoretical advantage.Aiming at the deficiencies,this paper focuses on the anti-noise interference technology of MV-PLC based on adaptive OFDM system.Firstly,based on the measurement data of MV power line channel noise,the characteristics of various noises are analyzed.On the other hand,the AR model of channel background noise is constructed.Meanwhile,the detailed processes of parameter estimation for the AR model is discussed.Through the statistical analysis of channel impulse noise data,a MARKOV chain model for random impulse noise is established.The above work provides a noise model reference for subsequent anti-noise interference research.Secondly,aiming at the weakness of the traditional OFDM system,an improved water-filling resource allocation algorithm combining SNR threshold is proposed.The algorithm uses SNR threshold which from statistical data to achieve early allocation of resources,and realizes the redistribution of resources baesd on water-filling principle.The practicality of original IWFP algorithm is inproved under the condition of minimizing the complexity.Based on this algorithm,an adaptive OFDM system for MV-PLC is established.Simulation results show that the adaptive resource allocation algorithm proposed in this paper has effectively realized resource allocation,reduced the bit error rate,and strengthened the anti-interference ability of OFDM system.Finally,based on the adaptive OFDM system,a low complexity subspace iterative algorithm is introduced to suppress background noise.And an improved clipping method is used to suppress impulse noise.For the former,the feature space of the noisy OFDM signal is decomposed based on the subspace theory,and under the constraint of minimum signal distortion,the best estimate of the ideal signal is obtained by applying the Lagrangian optimal extremum method.Moreover,the repeated one-dimensional subspace iteration is used to reduce the computational complexity.For the latter,the SLM algorithm is used to reduce the peak-to-average power ratio of OFDM signal before traditional clipping method.The accuracy of pulse noise identification is improved by this way.The results show that the anti-noise scheme presented in this paper can further improve the bit-error rate of the system,improve the SNR,and optimize the application of adaptive OFDM system in MV-PLC.