ZigBee technology is a short-range wireless communication technology with a unified standard. Its name comes from the observation of people dancing the "Z" in the honey bee collecting process. The bees are small in size, require less energy, and can transmit collected pollen. Therefore, ZigBee is used to represent wireless communication technologies with low cost, small size, low energy consumption, and low transmission rate. This paper introduces the structure of ZigBee network, analyzes the ZigBee RF performance, and discusses the ZigBee RF test method.
1 Introduction
ZigBee is one of the new technologies that will have a huge impact on the 21st century. Compared with traditional networks, wireless sensor networks are data-centric self-organizing wireless networks with fast temporary networking and network topology dynamics. It is highly resistant to damage and does not require the construction of network infrastructure. Based on these characteristics, ZigBee is widely used in military, environmental monitoring, smart home , building condition monitoring, complex mechanical monitoring, urban transportation, space exploration, and security testing in airports and large industrial parks. Environmental monitoring is an aspect of wireless sensor network applications. Sensor networks have obvious advantages in the field of environmental monitoring, and can provide a new means for environmental monitoring with more accurate, larger data volume and less impact on the environment.
ZigBee technology is widely used in environmental monitoring, smart home, building automation, industrial control and other fields due to its low cost, low power consumption, large network capacity, short transmission delay and high reliability.
2 ZigBee technology features and network structure
(1) Technical characteristics of ZigBee
â— Low power consumption: Because ZigBee's transmission rate is low, the transmission power is only 1mW, and the sleep mode is adopted, the power consumption is low, so the ZigBee device is very power-saving. It is estimated that ZigBee devices can last up to 2 years using only two 5th batteries, which is beyond the reach of other wireless devices.
â— Low cost: The initial cost of the ZigBee module is around $6, which is estimated to drop to $1.5 to $2.5 soon, and the ZigBee protocol is royalty-free. Low cost is also a key factor for ZigBee.
â— Short delay: The communication delay and the delay from the sleep state are very short. The typical search device delay is 30ms, the sleep activation delay is 15ms, and the active device channel access delay is 15ms. Therefore, ZigBee technology is suitable for applications with time-critical wireless control (such as industrial control applications).
â— Large network capacity: A star-shaped ZigBee network can accommodate up to 254 slave devices and one master device, and the network is flexible.
â— Reliable: A collision avoidance strategy (CSMA-CA) is adopted, and dedicated time slots are reserved for communication services requiring fixed bandwidth, avoiding competition and collision of transmitted data. The MAC layer uses a fully acknowledged data transmission mode, and each transmitted packet must wait for the acknowledgement from the receiver. If there is a problem during the transfer, you can resend it.
â— Security: ZigBee provides a packet integrity check function based on Cyclic Redundancy Check (CRC), which supports authentication and authentication. It uses AES-128 encryption algorithm, and each application can flexibly determine its security attributes.
(2) Equipment and network topology in the ZigBee network
It is divided into a full-featured device (FFD) and a reduced-function device (RFD) according to the function of the device.
â— Full-featured devices have more memory and computing power, with all 802.15.4 features and all features. There is a controller function that provides bidirectional transmission of information.
â— Streamlined function devices only have limited functions to control cost and complexity. They are only used as terminal devices, using small memory and small protocol stacks for easy implementation.
Divided into Zig-Bee coordinator, ZigBee router and ZigBee terminal device according to their role in the network.
â— The ZigBee Coordinator is at the top of the network. It is always working and has a stable and reliable power supply. It contains all the network information and is the most complicated of the three types of devices. It has large storage capacity and strong computing power. Can send network beacons, establish a network, manage network nodes, store network node information, and so on. They can only be undertaken by the FFD.
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