Research Of Baseband Signal Processing Method In G3-PLC Transmitter

Power Line Communication (PLC) technology has the advantages of smallinvestment, no rewiring, wide coverage, convenience of application, low cost ofmaintenance etc, which becomes widely used. However, Power line channelstructure is very complicated and has defects of serious multipath fading, large noiseand strong time-varying. Therefore, it’s necessary to develop a transmissiontechnology in order to improve the reliability and effectiveness of the power linecommunication.As a mature standard in narrow band power line communication, G3-PLCstandard has been widely approved by the many international standard system such asIEEE and ITU. It also has been accepted by some international electric metermanufacturers after the independent tests conducted by several world-levelorganization for standardization. Moreover, G3-PLC achieved a high speed datatransmission through the combination of the OFDM technology and coding technique,which ensures a successful access of worldwide power util ities into smart powergrids.This thesis, according to the functional and technology requirements, proposes ageneral plan of OFDM power line communication transmitter system based on G3standard. Chipset MAX2992and MAX2991of MAXIM are decided as the hardwareplatform. By reference to the MAXIM source code, the software platform is designedto be suitable for domestic power grids with the assistance of core technology andcustomized MAC and network-layer protocol. The signal processing procedure ofG3-PLC transmitter physical layer is highlighted in this paper for the further researchof base band signal processing method.Based on the above general plan, the paper makes a detailed analysis on thefeatures of power line channel such as input impedance, no ise and multipath fading,establishes a multipath fading channel transmission model and a noise channeltransmission model and then proposes a model of power line communication systemaccording to its transmission model and noise character. At last, the channel model issimulated in MATLAB environment which leads to the result that this model can fullyreflex the basic characteristics of low-voltage power line channel and is also identicalto its actual operating environment. These findings set the foundation for power line communication research.In view of the problem of single and low rate of convolutional codes and largeloss of data rate in the G3standard，the thesis puts forward an improved algorithmwith less complexity. Puncturing and depuncturing fo llowing convolutional code iscompleted to meet the code rate requirements and the interleaving algorithm isimproved by adopting the time and frequency two dimensional Interleaving.Following simulation experiment shows that the rate of convolutional codes is raisedfrom1/2to2/3，and burst errors are discrete into random ones more effectively.Moreover, data rate is raised without increasing the complexity of decoding，andpower line communication system performance is improved，so as to realize effectiveand reliable communication.