Research On Channel Estimation Based On OFDM Of Low-voltage Power Line

Power Line Communication is a new way to communicate and exchange the data information by means of power line.The reason of using power line to communicate and exchange data is: The cost is low,The power line can reach every region and all the people, Don’t need the extra wiring for data information exchange. However,At the same time of user benefit of its low cost,also get the disadvantages of inaccurate data transmission signal.The reason is:The channel environment which is used for power line communication is very poor.It will be damaged by the power line noise of internal and external and human factors.this factors limit the quality of data transmission and information exchanged.Orthogonal Frequency division Multiplexing technique applications have made the quality of power line communication get greatly improved. Because of OFDM technology has high spectrum efficiency. strong ability to resist the frequency attenuation and the advantages of good anti-noise make it become the main technology of PLC communication. In OFDM system, channel estimation technique is one of the key technology of OFDM system,the accurate to estimate the channel impulse response is direct affects the accuracy of the receiver data information.Therefore,in this paper, based on low voltage powerline channel estimation have done in-depth research. As shown below.Firstly,The traditional MMSE channel estimation algorithm to estimate channel impulse response accurately but it high complexity limits its used in communication field.As presented in this paper, based on the received signal and the pilot signal cross-correlation and pilot signal autocorrelation characteristics,We can remove the channel noise by relevant algorithm. the simulation showed that the precision of channel estimation and MMSE is similar, but the algorithm complexity is low, is of great help to implement power line communication.Secondly,Base on the pilot-averaged channel estimation,the improved channel estimation algorithm is presented in this paper.Due to the energy of channel impulse response is mainly focused on the cyclic prefixof less than,so we can estimate channel impulse response from this knowledge points,we can create a energy factor of impulse response in cycle prefix,then we can improve the accurate of channel estimation by this point. Simulation shows that this algorithm can improve the accuracy of channel estimation,and the performance of communication system is also improved.Finally, this paper offers a DFT channel estimation algorithm which is suitable for the PLC channel. Background noise power spectral density is low on power line channel and the characteristics of pulse noise power spectral density is relatively high, according to the above two kinds of noise respectively set two threshold to filter out noise, reduce the impulse noise effect on the estimate. The simulation results show that the algorithm improves the power line communication channel estimation accuracy and the reliability of the power line communication and transport.