Research And Implementation Of Data Transmission System Based On Power Line Carrier Communication

Power line carrier communications (PLC) is a new technique which utilizes the power line as medium to transfer signals. It takes full advantage of power network resources to realize multimedia communication (data, speech and video), and does not affect transmission of electric energy. PLC has the advantage of without rewiring, Hi-speed data communication network building and small investment. It can transfer signals faster than the existing wireless techniques. Since the wide distribution of power line network, the data communication network and broadband access of PLC have more superiority than other techniques.However, power line was designed for electric energy transmission, PLC has bad communication environment in the power line channels. So, we analysis the characters of power line channels which include input impedance, channel fading, noise and time varying. The input impedance increase with communication frequency increasing generally, and will fluctuate wildly at some frequency. The channel fading is proportional to communication distance and frequency. There are many noise sources, such as colored noise, narrow-band noise, periodic noise, stochastic noise, et al. Because of the different equipment of the power line using in different time, the noise and other parameters are time varying. To overcome these adverse factors, we adopt various modulation techniques (FSK, Spread spectrum communication and OFDM). The main contents of paper are as follows:(1) Design and realize a low tension narrow-band data communication system based on PLC chip-ST7538, which includes automatic meter reading system and monitoring system of public lighting equipment.(2) Design the tree structure of three phase power line data communication network. Overcome the PLC transmission distance problem by relaying approach. Considering the power line channel characteristics, we adopt answer mode and overtime retransmission to achieve communicating.(3) Design and realize a PLC module based on ST7538with serial communication interface. Develop a communication protocol with the properties of relaying transmission, expandability and generality.(4) A detailed introduction of hardware design, data processing (acquisition, storage, inquiry and reading), and the software realization of communication protocol is given in section4.1.In section4.2, an analysis of the hardware design and working principle of control terminal is given, and the programming method in introduced.(5) Develop a model machine of PLC automatic reading meter system which pass the experiment testing.