Research On Key Technologies Of Broadband Power Line Communication System Based On OFDM

With the modernization of our country’s power grid,Power line communication technology has become the key research content due to its wide coverge and low cost,and the current large-capacity,low-delay services put forward higher requirements on the speed and reliability of power line communication technology.Aiming to achieve the goal of high-speed,low-error communication,this paper researches on the broadband power line communication system based on OFDM（Orthogonal Frequency Division Multiplexing）,and uses FPGA（Field Programmable Gate Array）and DSP（Digital Signal Processing）development platforms to design and implement the hardware and software co-design of the receiving subsystem.Based on the analysis of the basic characteristics of the low-voltage broadband power line channel,this paper uses the model Middleton Class A noise to model random impulse noise,compares the transfer function modeling methods with the bottom-up method and the frequency domain analysis method,and decides to adopt the top-down method proposed by M.Zimmermann and Klaus Dostert.Then this paper combines the noise model and the transfer function model to establish the low-voltage broadband power line communication channel,which provides support for subsequent simulations.This paper explains the basic principles and key technologies of OFDM system,analyzes the advantages of applying OFDM technology in power line communication,then proposes the overall scheme of broadband power line communication system.The physical layer framework,main parameters and frame structure are designed,and the main functional modules of the receiving subsystem are introduced briefly.Aiming at the problem of receiving constellation diagram rotation and inter symbol interference caused by the offset of the starting position,this paper combines the delayed autocorrelation and the local sequence cross-correlation algorithm,and proposes the twice correlation algorithm based on local sequence,which can eliminate the peak plateau and"small spikes"phenomenon of the measurement function,and make the symbol synchronization result more accurate.In view of the mismatch of the sampling clock between the transmitter and receiver,this paper proposes the sampling clock synchronization algorithm based on phase superposition.Compared with traditional methods,the accuracy has a gain of more than 3d B.Aiming at the problem of high communication bit error rate caused by the multipath and noise characteristics of the power line channel,this paper proposes the mirror extended DFT channel estimation algorithm based on noise clustering.Compared with the traditional LS algorithm,the performance at the bit error rate10^-3 has improvement of about2.8d B.In terms of the optimization of OFDM peak-to-average power,this paper proposes the method to combine Hadamard transform and IPTS（Iterative Partial Transmission Sequence）,which can reduce the peak-to-average power ratio of the system effectively.Based on the FPGA and DSP development platform,this paper carries out the hardware and software co-design on the receiver of the proposed broadband power line communication system,completes the receiving system,and tests each module through functional simulation and board debugging.The results indicate that the receiver can restore the transmitted information accurately,verify the feasibility of the overall scheme and key algorithm of the broadband power line communication system proposed in this paper,and provide an important reference for the design of subsequent industrialized chips.