What isZigBee?
ZigBee is an open wireless personal area network (Wireless Personal Area Networks) standard based on the IEEE 802.15.4 protocol. IEEE 802.15.4 defines the physical layer and medium access control layer, while ZigBee defines higher layers such as network layer and application layer. ZigBee/IEEE 802.15.4 is mainly used in fields that require lower data transmission rates. Compared with other wireless communication technologies, ZigBee/IEEE 802.15.4 has the following advantages:

· Low Power
· Inexpensive
· flexible, reliable and self-healing
· Supports a large number of nodes
· Quick and easy configuration
· Use Safe
· Available globally
· Products are compatible with each other
· Producers are independent of each other

ZigBee, the name comes from the communication method used by bee colonies to survive and thrive: bees share information such as the location, distance and direction of newly discovered food sources by dancing ZigZag-shaped dances.

What isIEEE802.15.4standard?
The IEEE802.15.4 standard is a low-rate wireless personal area network (WPAN) developed by the Institute of Electronics and Electrical Engineers (IEEE). The IEEE 802.15.4 standard includes two specifications for the physical layer and the medium access control layer for low-speed wireless personal area networks. It supports simple devices that consume less power and operate in active spaces less than 10 meters in diameter. IEEE 802.15.4 operates in the Industrial Scientific Medical (ISM) band, which defines two physical layers, the 2.4 GHz band and the 868/915 MHz band. The license-exempt 2.4 GHz ISM band is available worldwide, while the 868 MHz and 915 MHz ISM bands are only available in Europe and North America, respectively.
For more information about IEEE802.15.4 visit http://www.ieee802.org/15/pub/ TG4.html.

What is the difference between ZigBeeand other wireless standards?
There are many current wireless standards that meet medium to high rate transmission requirements for voice, local area network or video. But before the advent of ZigBee, no wireless network could meet the transmission requirements of sensors and control devices. Sensors and control devices do not require high bandwidth, but rather low latency and very low power consumption to maintain long battery life and large arrays of devices.

In real life where ZigBee can be applied?
ZigBee can be widely used in building automation, industrial, medical and residential control and monitoring and the following fields:
· Device Management
· Lighting Control
· Automatic meter reading
· Wireless Smoke and Carbon Monoxide Detectors
· Air Conditioning and Ventilation Control
· Home control, such as anti-intrusion sensors, glass break detectors, noise detectors, etc.
· Environmental Control
· Medical Monitoring
· Remote Home Control
· Industrial and Building Automation

For example, the wireless sensors (temperature, humidity, vibration, etc.) installed in the container form a mesh network, and each container in a ship forms a mesh network that reports sensor data to the control center on the ship. Further, the ships can form a larger mesh network controlled by the port control center.

Is ZigBee reliable data transmission?
Reliable data transmission is very important for ZigBee applications. The IEEE 802.15.4 standard provides several mechanisms at multiple levels to ensure the reliability of data transmission. For example: ZigBee transmits data using 27 channels in three different frequency bands.

How long is the transmission distance of ZigBee ?
Under the output power of -3dBm (0.5mW), the distance of single-hop connection can reach more than 10 to 100 meters according to different environments, antennas and operating frequency bands. ZigBee can reach distances far beyond single-hop connections in the case of more complex networks composed of multi-hop connections and routing connections.

What is the size of the ZigBee network?
A ZigBee network includes up to 255 ZigBee network nodes, one of which is the master (Master) device, and the rest are slave (Slave) devices. Through the coordinator, the entire network can support up to more than 65,000 ZigBee network nodes.

What types of devices exist onZigBeenetworks?
The IEEE MAC specification defines three main types of devices in a ZigBee network:
ZigBee Coordinator. Maintaining the operation of the entire network is the most complex device among the three devices, which occupies the largest memory and has the most computing power.
ZigBee router. Communicate as a repeater between remote devices and can be used to extend the range of the network.
ZigBee end device. Exists in the network only as a physical device.

ZigBeeWhat topologies are supported?
The following diagram depicts the ZigBee supported topologies and the roles of the various devices.

ZigBee supports a total of three different network topologies, namely star, tree and mesh. Each structure has its own advantages and can be used in different scenarios. The star structure is the most common and simplest, it consists of several nodes connected to a central node. The mesh structure can provide a higher degree of reliability. It consists of many various nodes to form a complex mesh structure. The nodes can communicate with each other, and the information can reach the designated node through different paths. When a certain path is disturbed, the information can also be transmitted through other available paths. . The tree structure is essentially a combination of star structure and network structure.