Research Of Techniques For Noise Mitigation In OFDM-Based Power Line Communications

Power line communication technology(PLC)plays a very important role in the development of smart grid,Because the power line system has a wide range of basic measures,it can transmit data to every corner of the world based on the existing power line power network,which greatly saves the cost.Therefore,more and more researchers are focusing on the research of power line communication technology based on orthogonal frequency division multiplexing(OFDM)technology.However,the communication environment of the power line is complex,and always exists a lot of noise interference,which hinders the development and application of power line communication technology.Especially the impulse noise is the biggest bottleneck in the reliability improvement of power line communication system based on OFDM.Based on the above problems,this paper will rely on the research status of the noise suppression techonlogy in power line system,through in-depth analysis of noise types,noise models and the advantages and disadvantages of noise suppression at home and abroad,we study the noise suppression algorithm in power line communication system based on OFDM technology,and improve the reliability of power line communication technology.The research content and results of this paper are as follows:(1)A nonlinear noise suppression algorithm based on Blanking and Clipping is proposed.It has two thresholds,T and T/a,T is Blanking threshold,T/a is Clipping threshold,a is scaling factor.Most of the previous researches mainly focus on finding the optimal threshold T to improve the ability of noise suppression,but the optimization of scale factor a is ignored.Based on this,this paper proposes a method for estimating the optimal scaling factor to improve the performance of joint Clipping and Blanking method.Most of them get the value of scale factor through many simulations,which indirectly increases the complexity of algorithm implementation.The simulation results show that,the optimal scale factor makes the average bit error rate of the system reduced by 0.02,and the average output SNR is improved by 0.3dB.(2)A noise suppression algorithm which converts frequency domain noise interference to time domain is proposed.Firstly,the frequency point location of noise is detected in the frequency domain,then the frequency domain noise is suppressed in the time domain,the LMS algorithm is applied to the G3-PLC protocol for noise suppression.The simulation results show that compared with the method which directly removes the frequency domain noise in frequency domain,the proposed method in this paper has better BER and achieved the purpose of noise suppression,also greatly improve the stability of power line communication system.