Research On Noise Mitigation Method Of Low-voltage Power Line Communication Based On OFDM

Power line communication(PLC)is a data transmission technology based on distribution network that has wide distribution and no need for rewiring,it has great advantages and prospects in field of smart grid and smart home.However,power lines are mainly used for power transmission,and there are varying line impedance,frequency selective fading,and various noises on it.Among them,impulsive noise(IN)affect the performance of power line communication seriously,and brings severe challenge to accurate transmission of information.Therefore,how to realize effective transmission and processing of communication signal in the environment of bad noise interference has been paid more and more attention by universities and scientific research institutes at home and abroad all the time.In this paper,the power line noise is measured in various environments,and the effect of various IN mitigation algorithms is analyzed in depth based on orthogonal frequency division multiplexing(OFDM)power line communication,the main research results are listed as follows:(1)For the stationary IN in low peak period of power consumption,an IN mitigation algorithm based on moment estimation and iterative feedback compensation is proposed.First,moment estimation method is used to estimate the IN characteristics,according to which different noise mitigation methods are used to deal with IN.In addition,a lookup table is constructed to control the iteration times of iterative feedback compensation.Next,an adaptive blanking threshold of IN is determined according to the working curve of the receiver base on the obtained characteristic parameters.Finally,according to the established noise model,the performance of the proposed noise mitigation algorithm and the traditional noise mitigation algorithm are compared,and the performance of the communication system is effectively improved.(2)For the sudden change IN in peak period of power consumption,an IN mitigation algorithm based on companding peak and hard decision feedback is proposed.The algorithm uses compression and expansion method to process the transmitted signal at the sending end,resulting in converting the transmitted signal from Rayleigh distribution to uniform distribution.In addition,it digitally encodes the peak value of the companding signal,and use a separate control channel transmit the coded signal.At the receiving end,the received IN frequency is estimated according to the received peak value of companding signal,and a relationship between the IN frequency and the IN characteristic is established.Further more,with the estimated IN frequency,the received signal is processed by peak blanking or hard decision feedback compensation adaptively.Finally,the performance of the proposed algorithm and the existing algorithm is analyzed according to the established noise model.(3)For the burst IN generated by switching of large electrical appliances,an IN mitigation algorithm based on interleaver and compressed sensing(CS)is proposed.First,interleaver is used to permute burst IN.Then moment estimation method is used to estimate the characteristic parameters of IN,basis pursuit de-noising(BPDN)method is used to obtain the coarse amplitude information of IN.In addition,the estimated IN parameters are used to determine the position support set of IN,and minimum mean square error(MMSE(Minimum Mean-Square Error)method is used to obtain the accurate amplitude of IN.Further more,in order to save the resources of the communication system,the number of zero subcarriers is determined adaptively with the IN characteristics.Finally,the proposed noise mitigation algorithm is compared with other CS algorithms and blanking/clipping algorithms,and the subcarrier utilization of the proposed algorithm is analyzed.(4)In view of the high complexity of various IN mitigation algorithms,an IN mitigation algorithm based on optimal threshold and power estimation is proposed,it can realize simple and fast IN mitigation effect.First,the noise power of the received signal is estimated by using the zero subcarriers of the communication process,then a look-up table is established between the noise power and the preset optimal blanking threshold,therefore,IN mitigation algorithm can be realized quickly.In order to further improve the performance of IN mitigation,the peak-to-average power ratio(PAPR)of the transmitted signal is processed to improve the efficiency of the optimal blanking threshold and to compensate for the error of the IN power estimation.Compared with the traditional algorithm,the proposed algorithm has the advantages of low complexity,easy implementation and high time efficiency.(5)In view of the spatial correlation between IN in multi-input and multi-output(MIMO)power line channel,a structured compressed sensing IN mitigation algorithm based on MIMO is proposed.The algorithm acquires data from zero subcarriers in multiple transmission channels on power lines,then obtains multiple measurement vectors in frequency domain.Next,an adaptive blanking threshold is determinded based on the IN parameters derived from moment estimation,and the IN presupport set is obtained according to the adaptive limiting threshold.Further more,the IN is reconstructed by compressed sensing and mean square error estimation method.Theoretical and experimental results show that compared with the traditional compressed sensing reconstruction algorithm,the proposed algorithm has lower bit error rate(BER)and lower complexity.The advantages are more obvious in case of large IN sparsity and large amount of transmission data.