Research On Application Of Wavelet Lifting Algorithm In G3-PLC

G3-PLC(G3-Power Line Communication)is an international standard for power line communication.Its physical layer signal transmission model is based on Orthogonal Frequency Division Multiplexing(OFDM)based on Fast Fourier Transform(FFT).Due to the strict requirements of OFDM for orthogonality and synchronization,it is difficult to guarantee the reliability in complex channel environment,and has the problems of high peak-to-average ratio and low efficiency.Therefore,this paper proposes OFDM based on Lifting Wavelet Transform(LWT)and applies it to G3-PLC physical layer signal transmission model.Through lifting wavelet transform,the inter carrier interference of G3-PLC communication system in complex channel environment is reduced,the reliability is improved,the peak-to-average ratio of the system is reduced,and the transmission and implementation efficiency are optimized by reasonably reducing cyclic prefix and integer wavelet transform.Firstly,the thesis analyzes the signal transmission model of G3-PLC and the core technology principle of OFDM.In view of the performance defects of FFT-OFDM applied to G3-PLC,based on the analysis and research of the basic idea of wavelet lifting algorithm and the selection of wavelet basis function,LWT was used to replace FFT,and the LWT-OFDM system was established.The good scale and shift orthogonal characteristics of the lifting wavelet transform were used to improve the communication reliability of the system and reduce the peak to average ratio.Then,the signal transmission model and frame structure of G3-PLC were designed with LWT-OFDM as the core,and the performance analysis and simulation platform was built.Bit error rate and peak-to-average ratio performance of the communication system are simulated and analyzed in Gaussian,multipath and measured power line channels from the aspects of lifting wavelet basis and lifting wavelet decomposition layer number.By comparing and analyzing the performance of haar,db8,sym8 and bior6.8 four different wavelet bases,sym8 wavelet base suitable for the system is selected.And using integer wavelet transform to improve transmission efficiency.Finally,the effective combination of selecting Mapping(SLM)and limiting filtering is used to reduce the system peak to average ratio.The performance of G3-PLC.system model is simulated and analyzed in the actual power line channel environment.The results show that:compared with the G3-PLC system based on FFT-OFDM,when the BER is 10-3,the performance is improved by about 5dB,the communication efficiency is improved from 40%to 58%,and the peak-to-average ratio is reduced from 11dB to 6.5dB,and the communication performance is significantly improved;the LWT-OFDM system after integer processing is improved.The LWT-OFDM-based G3-PLC system after integer processing has a bit error rate of 10-3.Although the performance is reduced by 0.5dB,but the efficiency is further improved.