Application of Home Internet of Things Technology in Smart Home System

    0 Introduction

　　The smart home system is an open, intelligent, and humanized integrated home system that uses a number of high-tech technologies. It organically combines broadband Internet, home appliances, home automation, and home security and anti-theft. The home smart controller is the hub of the home network, through which the information appliances in the home network can be centrally monitored and remotely controlled.

　　At present, the main way for home systems to access the Internet is wired access. The most popular wired broadband access technologies are ADSL (asymmetric digital subscriber line) and HFC (hybrid coaxial fiber network). However, the existing wireless communication network also has the ability to provide a certain transmission rate for data communication services. For example, the ZigBee network can theoretically provide a transmission rate of up to 250 Kb/s, which fully meets the requirements of information appliance control information transmission. Therefore, home network wireless communication has broad development prospects [1.2].

　　The smart home system consists of three networks: home Internet of Things, home wireless LAN and external network. The home Internet of Things is established through a reliable and fully covered wireless network (ZigBee, small wireless, power line carrier, etc.); the Internet of Things network consists of network nodes and management centers. The communication module of the home wireless LAN is a home high-speed LAN established through WiFi, and the network adopts TCP/IP standard protocol. The external network can be a community LAN, cable TV network, telephone network and Internet, etc., most of which use relatively mature technologies.

　　This article uses ZigBee technology to design a home Internet of Things, which controls various home appliances and lighting systems through smart sockets, and integrates network metering of smart electricity services, orderly electricity management and intelligent control into a new generation of smart home systems.

　　1 ZigBee Technical Features

　　ZigBee technology is an emerging wireless technology in recent years. Compared with long-distance communication technologies such as Ethernet, GPRS and CDMA, it has the characteristics of short distance, low complexity, low power consumption, low rate, short delay, large capacity and high communication reliability [3]. Compared with short-distance wireless communication technologies such as Bluetooth and WiFi, although the transmission rate is low, it has the biggest advantages of low power consumption and long battery life. The physical and MAC layer protocol used by ZigBee is IEEE 802.15.4, which operates in three industrial, scientific and medical (ISM) frequency bands of 868 MHz, 915 MHz and 2.4 GHz. Among them, the 2.4 GHz frequency band is free to use worldwide. In summary, the characteristics of ZigBee technology are very suitable for application in smart home systems. Therefore, ZigBee technology is used in the home Internet of Things in the smart community pilot of Shaoxing Power Bureau.

    2 System Design

　　The structure of the smart home system in this paper is shown in Figure 1.

　　The whole system consists of a smart home gateway and a ZigBee wireless network, which mainly realizes the control of home appliances, lighting systems, and security systems.

　　3. Smart Socket

　　Smart sockets are mainly used to control televisions, refrigerators and other similar electrical appliances. They not only have the on-off function of ordinary sockets, but also have metering and communication functions, support remote management, and users can choose according to actual application needs. Smart sockets are mainly composed of communication modules, metering modules, power modules, output control circuits, protection circuits, key circuits and display modules. The mainboard circuit chip is shown in Figure 2.

　　4 Data Transfer Protocol

　　4.1 Data Link Layer

　　This protocol is a half-duplex communication method with a master-slave structure. The handheld unit or other data terminal is the master station, and the smart socket is the slave station. Each smart socket has its own address code.

　　The establishment and release of the communication link are controlled by the information frame sent by the master station.

　　Each frame consists of seven fields: frame start character, slave station address field, control code, data field length, data field, frame information longitudinal check code and frame end character. Each part consists of several bytes.

　　4.2 Byte Format

　　Each byte contains 8 bits of binary code, and a start bit (0) is added during transmission. An even parity bit and a stop bit (1) are added, for a total of 11 bits. The transmission sequence is shown in Figure 3. D0 is the least significant bit of the byte, and D7 is the most significant bit of the byte. The low bit is transmitted first, followed by the high bit.

　　4.3 Data Identification

　　4.3.1 Data identification structure

　　The data identification code uses 4 bytes to distinguish different data items. The 4 bytes are represented by DI3, DI2, DI1 and DI0 respectively. Each byte is encoded in hexadecimal. The data types are divided into 7 categories: electric energy, maximum demand and occurrence time, variables, event records, parameter variables, frozen quantity, and load records.

　　4.3.2 Frame format

　　Frame is the basic unit for transmitting information. The frame format is shown in Figure 4.

　　4.3.3 Data transmission form

　　The data identification code identifies a single data item or a collection of data items. When requesting access to a data collection consisting of several data items, a data block identification code can be used. The actual application is subject to the definition of the data identification code table.

　　5 Conclusion

　　This paper designs home Internet of Things technology based on ZigBee technology, and designs a smart home system with simple structure, low cost, high performance and low power consumption. The system has been applied in the smart community pilot project of Shaoxing Power Bureau. The designed smart home system has power characteristics and can complete network metering of power business, household energy information management and mode control to achieve the purpose of saving energy and reducing energy consumption. On the other hand, smart home has home intelligent design such as visual intercom, local and remote control of home appliances, security alarm, etc., so that users can enjoy the comfort and convenience of home intelligence while also achieving energy saving and environmental protection. Reduce household energy consumption, thereby achieving the goal of intelligent life, and providing a good solution for realizing a better smart home system.