A Smart Home System Based On A Hybrid Network Of Wireless Sensor Networks And Power Carrier Communications

As the progress of technology of Internet of Things. Zigbee network are widely used as terminal of wireless sensor network to monitor parameters of surrounding for its features of low-cost, low-power-consumption, low-bit-rate and no-wiring.As a significant development direction of Internet of Things, Smart home undergo the process of using from coaxial wire to RS485 wire then to Zigbee as transmission medium. Majority of smart home are utilizing Zigbee as backbone network now. Compare with wire backbone network, Zigbee has the advantages of no wiring, easily to organize network and so on. But the inherent shortcomings of low diffraction, low capacity of through-wall and so on limit the application of Zigbee. In addition, because of the usage of 2.4G unlicensed frequency band, it makes Zigbee signal which has attenuated severely during the process of propagating indoors suffering same frequency interference more easily from signal of 2.4G. They are include WiFi, Bluetooth, microwave radiate and so on. Because of the feature of high-transmit-power of WiFi, as backbone network, Zigbee suffer same frequency interference from WiFi largely. This project firstly introduce the characters of 802.11 and 802.15.4 protocol at 2.4G frequency band which are utilized by WiFi and Zigbee respectively. Analyzing interference between them in theory first, and then designing a experiment to measure the interference between them by channel number, frequency offset, distance between WiFi and Zigbee network and other parameters.Although there are many way to mitigate the interference between them, such as utilizing frequency agility mechanism, reducing duty ratio of WLAN network and so on. But once in a context of apartment, Zigbee will not only suffer interference from indoors', but also from neighbours' WiFi network. Base on it, A hybrid network smart home base on Zigbee and power line communication(PLC) is proposed.PLC utilize power line to communication directly. Smart home is under the background of apartment and power line are all over the wall. So, smart home use PLC as backbone network which makes wiring is unnecessary. The devices and module for PLC can get power from power line by AC/DC module directly. Power line are communication backbone network and power supply network simultaneously. Smart home must involves the control for household appliance. Using PLC as backbone network can directly use PLC communication module to control relays to achieve the goal of commanding household appliance. Compare with pure Zigbee network this system is simpler and more practical. As an extension of PLC network, Zigbee has the features of low power consumption and organizing network easily, is applicable to be a sensor terminal to monitor environment variables.This project used PL3120 as power line communication chip, S3C2440 as main control chip, CC2530 as Zigbee communication chip. This paper is concentrate on introducing Zigbee and PLC technology and realizing a hybrid network smart home base on Zigbee and PLC. Experiment results show that, compare with pure Zigbee network, hybrid network have more advantages and market prospect.