Research And Implementation Of The Key Technology Of Smart Home System Based On PLC

As the rapid development of electronic information technology, automatic control technology and sensor network, people’s living standards continue to improve and Internet has influenced all aspects of life much than more. At present, people pursuit intellectualized, humanized and comfortable life but the traditional appliances have been unable to meet these demands. As a result, how to use the Internet to monitor and control household alliances conveniently and form a complete system of smart home become a research focus in recent years.There are many kinds of mediums to construct the network of smart home and we can divide them into two categories:the wireless and the wired. The wireless mode mainly include bluetooth, infrared, ZigBee and so on. As wireless devices popularize in the life, people pay more attention to the potential impact of radio radiation on the body. As a result, the wired which is represented by power lines, telephone lines, coaxial cable and so on will have more development space, especially the power line communication. It has lots of advantages such as no rewiring, low cost and it is suitable for the intellectualized reconstruction for old house. In view of the advantages and disadvantages of the existing network mode of smart home, this paper proposes a scheme which is designed on WiFi and low voltage power line communication. It solved the problems which is not easy to connect to the Internet and to realize the centralized control on the handset in the previous power carrier communication system.As the power line is designed to transmit power rather than signal. When using it as a signal transmission channel, it has some characteristics such as varied impedance, strong noise interference, serious signal attenuation and multipath interference. This paper analyzes the related characteristics of low voltage power line and establishes a practical channel model. The model covers many characteristics of the channel and it is conducive to deepen the understanding of power line channel and study the demodulation, technology and select the simulation design parameter in the following chapters. Then comparing the technologies such as the traditional modulation technology, spread spectrum communication and OFDM which can be used in the power carrier system. After the simulated design and comparing the parameters, we can conclude that OFDM technology is the ideal choice to realize high speed digital transmission in low voltage power distribution network.In view of the inter-symbol interference and multipath effect in the power line channel, this paper focuses on the effects of cyclic prefix and different signal-to-noise ratio to the system combing OFDM modulation and demodulation principle on the basis of the original modulation mechanism of the power carrier chip HT8560C. Research has shown that joining the cyclic prefix will lose a certain amount of power and influence the information transmission rate but it can eliminate inter-symbol interference and significantly improve the ability to resist the multipath interference. Moreover, with the increase of input SNR, the bit error rate of the system reduced and the performance improved.Finally, I use the resources of the internship company to design the AP and switch module in the aspect of hardware and write the PC and ANDROID terminal software in the aspect of software on the basis of the power carrier chip HT8560C. Then we formed a complete set of smart home system which is based on WiFi and low voltage power line communication and tested the communication distance, anti-interference and the overall communication effect of the system. Results show that the system has realized the remote monitoring and control of household equipment, and the reliable and real-time performance and communication distance can meet the requirements of smart home.