The Design Of Power Line Communication System Based On OFDM And Its FPGA Implementation

The low-voltage power line communication is the generic name for a networktechnology that transmits data information over low-voltage power line. Thelow-voltage power line networks cover a wide range of areas. There is no need for thelaying of new communications networks. The low-voltage power line communicationgreatly reduce the communication cost and has the advantage of convenient connection.However, Low-voltage power supply networks are not designed for communicationpurposes. Thus, the PLC transmission channel is not very suitable for data transmission.OFDM (Orthogonal Frequency Division Multiplexing) technique can effectivelyovercome multipath interference and frequency-selective fading on the power linechannel, and has high spectral efficiency. Therefore, OFDM technique adapts to theapplication in low-voltage power line carrier communication very well. Currently,Application of OFDM technique in low-voltage power line communication has receivedconsiderable attention.Firstly, the background of power line communication and the current research onpower line communication in domestic and abroad are introduced in this paper. Then, itintroduces the transmission characteristics of the low-voltage power line channel.Analyze three transmission characteristics named input impedance characteristics,attenuation characteristics, noise characteristics. According to the power line channelcharacteristics, the paper proves that zero section of alternating current is the bestcommunication time slot for power line communication. Then, the basic principles andimplementation process of OFDM technology is introduced. This paper clarifies theadvantage of OFDM technology for the power line carrier communication system.Meanwhile, G3-PLC physical layer specification based on the OFDM power linecarrier communication standard is analyzed, including the basic parameters, the framestructure, preamble and so on. The primary modules of G3-PLC physical layerspecification is emulated by software.Secondly, Based on G3-PLC specification, according to the specificity and statusof domestic low-voltage distribution network, a low-voltage power line carriercommunication system was designed based on OFDM. The work mainly includeseveral aspects as follows: system block diagram, zero communication, the framestructure, preamble and selection of windowing function. Thirdly, the whole physic layer of low-voltage power line carrier communicationsystem is design by FPGA device and single chip microcomputer. The system mainlyconsists of the Micro Control Unit (MCU), baseband modem and analog front-end. Theprinciple and process of the key functional modules implemented in hardware areelaborated. A new algorithm based on training sequence is presented according to theframe structure of new system. The algorithm is not only effective in achieving thesymbol synchronization, but also has low computation, hardware resource consumptionand fast synchronization.Finally, the thesis built the hardware debugging platform, and debug the hardwaresystem. The results show that the system can operation stably in domestic low-voltagedistribution network and basically fulfils the design demands.