Study Of The Channel Coding Technologies In The Low Voltage Power Line Carrier Time Synchronous System

With the rapid development of the Power Line Communication (PLC)technology, the use of the power lines for data transferring is becoming more andmore stable. On October31,2013, the association of IEEE passed the1901.2standard,which provides a complete solution for overcoming the key challenges and obstaclesof the medium or low voltage power lines’ harsh channel environment and thecommunications through the transformers. Thanks to these, the high precision timeand frequency will be transferred through the low voltage power lines, and it will be anew technique of the time synchronization.At present, the domestic researches about this technique is given priority to Dr.FengPing of the National Time Service Center, he used the spread spectrummodulation technology and did the experiments from50meters, the time synchronousdifferential results of this is about5milliseconds. Based on Dr. Feng’s study, the textuses new technologies to redesign the structure of time transferring on low voltagepower lines and expects to improve its transmission accuracy, stability and distance.Besides, it focuses on the channel coding technology which can detect and correct thewrong transmission signals. Finally, implements the Analog Front End(AFE) circuit.The specific works done are as follows:First, the text has studied the characteristics of the low voltage power lines as thetransmission medium, including its topology, channel characteristics and noisecharacteristics. Then gave them models and did simulations through MATLAB.Second, has presented a realizing solution for the low voltage power line carriertime synchronization system and has studied the OFDM modulation technologywhich used in the system, then also designed its basic parameters, involving thefrequency range, the number of sub-carriers, the mapping means, the way to add acyclic prefix and so on.Third, has mainly studied the channel coding techniques of the low voltagepower line carrier time synchronization system, using the MATLAB simulation toolhas compared the system’s transmission bit error rate which uses the BCH code, RScode, convolution code or RS-convolutional concatenated code based on the OFDMmodulation, and then chose the suited one scheme.Fourth, has designed and completed the Analog Front End circuit of the low voltage power line carrier time synchronization system, comprising a transmissioncircuit, a reception circuit and a coupling circuit.Through the MATLAB simulation in these studies, the text ultimatelydetermined the RS-convolutional concatenated code with scrambling and interleavingtechniques as the channel coding scheme of the time synchronization system, whichprovided the theoretical basis for the realization of the software and hardware of thesystem. Meanwhile, the OFDM modulation’s parameters design and the realization ofthe hardware of Analog Front End circuit all laid a solid foundation for the nextstudies.