Research On Signal Synchronization And Channel Estimation Of Power Line Communication System Based On OFDM

With the rise of smart grid,power line communication(PLC)become a hot research once aagain.It's considered to be one of the important and essential ways to achieve smart grid.Although the PLC has been developed for decades,but so far it can not be widely used.One of the important reasons is that the environment of power line is complex,and its load is variable.Moreover,the noise interference is serious.These lead to the reliability of PLC is not high.With its many good communication performances,OFDM has been adopted by the vast PLC terminals.Signal synchronization and channel estimation are two important parts of OFDM system.Therefore,in order to improve the reliability of PLC,this paper mainly discusses the signal synchronization and channel estimation of OFDM,which is used in the low voltage PLC(LV-PLC).Firstly,we introduce the present development and research status of PLC at home and abroad.The advantages and shortages of various signal synchronization algorithms and channel estimation algorithms are analyzed emphatically.Secondly,the basic principle of OFDM system is presented.We also analyze the characteristics of low voltage power line channel,and we establish the frequency response model and noise model of LV-PLC.On this basis,the model of OFDM PLC system is established,which lays the foundation for the follow-up research.Thirdly,by analyzing the synchronization algorithms of OFDM,we propose a new local correlation synchronization algorithm(PR algorithm),which is based on synchronous training sequence and the characteristics of PLC.The PR algorithm includes two parts,timing synchronization and frequency offset estimation.Through the simulation and analysis,the PR algorithm and Park's algorithm are compared from three aspects: the significance of the peak of timing function,the calculation of timing synchronization and the accuracy of the timing synchronization.In addition,from the perspective of estimating the mean square error of the frequency offset,the improved algorithm is compared to the Schmidl algorithm.Then,based on the analysis of LS algorithm and MMSE algorithm,a new method is proposed,which is about how to use the relationship of the power of channel impulse reponse and SNR to set a threshold for the channel impulse respone to deny noise.It can improve the synchronization performance of the LS algorithm when SNR is low.Based on the charateristics of slow timing-varying of PLC channeland and the fact that the channel estimation in OFDM directly determines the error rate of communication system,we design a method to optimize the channel estimation algorithm.Through the simulation and analysis,we verify the superiority of the improved algorithm from the mean square error and the communication error rate of channel estimation.Finaly,we construct an experimental platform of PLC,and design an OFDM system of PLC.Then,we program DSP procedures to achieve point to piont communication on the 220 V power line.We design two experimental scenarios which are good channel situation and bad channel situation.Our algorithms are applied to the experiment to verify their feasibilities.