Research On Key Technologies Of OFDM In Low-voltage Power Line Communication

With the strong smart grid has entered the overall construction stage, as an important link of strong smart grid, smart power community is under construction in many districts of China.Low voltage power line communication(LPLC) as special communication mode, can be used as the effective communication support technology for the smart power community. Based on the technology of OFDM,low voltage power line communication has wide development prospects in smart grid. Peak-to-Average Power Ratio Reduction and Channel Estimation are the two Key Technologies needed to solve. According to the channel environment and application characteristics of low voltage power line, two Peak-to-Average Power Ratio Reduction methods and one channel estimation method are proposed in this paper.The PAPR reduction algorithms for OFDM are studied in this paper.Then an improved SLM method based on hadamard transform and four-dimensional hyper-chaotic sequences is proposed based on the generalization of existing PAPR reduction algorithms. First, nonlinear four-dimensional hyper-chaotic phase sequence is used to transform the data into two segmented sequences respectively and then Hadamard transform is applied. Finally, the selected data with minimum PAPR will be transmitted after using IFFT transform to every row of the data. Besides, an improved SLM method based on split preference and four-dimensional hyper-chaotic sequences is proposed which combines the method of split preference based on the previous improved SLM method and achieves good performance. Simulation results show that the proposed two schemes can significantly improve the PAPR reduction performance.The classic LS algorithm is used to obtain the rough approximation of channel frequency response, and then split and interpolate it. The accurate channel estimate is obtained by the use of adaptive filtering. Simulations show that this proposed algorithm can effectively and precisely estimate the channel characteristics of low voltage power line, with greatly reduced error rate and thus confers excellent channel estimation properties.