1, Zigbee comes from Bluetooth
During the use of Bluetooth technology, Bluetooth technology has been found to have many drawbacks despite its many advantages. For the field of home automation control and industrial remote control, Bluetooth technology is too complicated, power consumption is large, the distance is short, the network size is too small, and the demand for wireless data communication is becoming more and more intense in industrial automation. It must be highly reliable and resistant to electromagnetic interference from industrial sites. Therefore, after long-term efforts, the Zigbee agreement was officially released in 2004 after it was passed in mid-2003.
2, Zigbee is a high-reliability wireless data transmission network of your own
Zigbee is a wireless data transmission network platform consisting of up to 65,000 wireless data transmission modules. It is very similar to the existing mobile communication CDMA network or GSM network. Each Zigbee network data transmission module is similar to a mobile network base station. Throughout the network, they can communicate with each other; the distance between each network node can be from the standard 75 meters, to the extended hundreds of meters, or even several kilometers; in addition, the entire Zigbee network can not only "infinitely" expand It can also be connected to other existing networks. For example, you can monitor a Zigbee control network in a certain place in Yunnan via the Internet.
The difference is that the Zigbee network is mainly established for industrial field automation control data transmission. Therefore, it must be simple, easy to use, reliable, and low in price. The mobile communication network is mainly established for voice communication; the value of each mobile base station is generally more than one million yuan, and each Zigbee "base station" is less than several hundred yuan; each Zigbee network node can not only be Monitoring data acquisition and monitoring directly on objects, such as sensor connections, it can also automatically transfer data from other network nodes; in addition, each Zigbee network node (FFD) can also cover its own signal coverage. Internal, and multiple isolated child nodes (RFDs) that do not undertake network information relay tasks.
Each Zigbee network node (FFD and RFD) can support up to 31 sensors and controlled devices, and each sensor and controlled device can have 8 different interface modes. Digital and analog quantities can be acquired and transmitted.
3. Application fields of Zigbee technology
The goal of Zigbee technology is to target industrial, home automation, telemetry and remote control, such as lighting automation control, wireless data acquisition and monitoring of sensors, oilfield, power, mining and logistics management applications. Industrial site requirements for wireless data transmission and Zigbee technology features: low power consumption, low data volume (250KPS), low cost, free ISM band (2.4G), high anti-interference performance, direct sequence spread spectrum communication (DSSS), high confidentiality (64-bit factory number and support for AES-128 encryption), high integration and high reliability; automatic dynamic networking between node modules, including mesh network The topology uses a collision avoidance mechanism, and information is transmitted through the automatic routing in the entire Zigbee network, thereby ensuring the reliability of information transmission.
4. Zigbee's development prospects
Zigbee technology and RFID technology were listed in 2004 as two of the world's fastest growing and most promising top 10 technologies. For reports on this, you only need to type "Zigbee" in Baidu, or in the GOOGLE search bar, and you will see a lot of relevant reports. In short, in the coming years, Zigbee technology will be a period of rapid development.
5. Why should Zigbee technology use mesh communication?
Mesh network communication is actually multi-channel communication. In actual industrial sites, for various reasons, it is often impossible to ensure that every wireless channel can always be unblocked, just like a city street, it may be caused by a car accident, road maintenance, etc. The traffic on one road was temporarily interrupted. At this time, because we have multiple channels, the vehicle (equivalent to our control data) can still reach the destination through other roads. This is very important for industrial site control.
6. What is automatic networking?
A simple example can illustrate this problem well. If a team of paratroopers descends from the sky, each of them holds a Zigbee network module terminal, and when they land on the ground, as long as they are within the communication range of the network module, they pass each other. Automatic search, and soon to form an interconnected Zigbee network. They don't know who is next to whom they are in advance. At the same time, the contact between them will change due to the movement of people. Therefore, the module can also refresh the original network by re-finding the communication objects, determining the contact with each other.
7. Why should the network adopt dynamic routing?
First, we must understand, what is dynamic routing? Dynamic routing refers to the path of data transmission in the network. It is not preset. Before transmitting data, it searches for all the paths available at the time of the network, determines their distance, and then selects one of them. data transmission. In our network management software, the path is selected using the "gradient method", that is, the channel closest to the path is selected for transmission. If it is not transmitted, another channel is transmitted a little further, and so on. Until the packet is delivered to the destination. In actual industrial sites, the pre-determined transmission path may change at any time, or the path may be interrupted for various reasons, or it may be too busy to transmit in time. Dynamic routing combined with the mesh topology can solve this problem well, thus ensuring reliable data transmission.
8. What are the benefits of Zigbee's communication method using direct sequence spread spectrum?
In the same frequency band, different communication methods have great differences, such as ASK, FSK, FHSS, DSSS, etc., from anti-interference ability, communication security confidentiality, and reliability are different. Like the CDMA system, the Zigbee system uses Direct Sequence Spread Spectrum (DSSS), which is a communication method with strong anti-interference ability, confidentiality and high reliability. If you have used communication products for these two technologies, you will find that the reliability of the two is significantly different.
Since the spread spectrum technology can achieve a low signal-to-noise ratio during normal communication, that is, it can still work normally in a highly interference environment. According to calculations and experiments, this is equivalent to an increase in reception sensitivity of 7dBm. It is not easy to interfere with others. In other words, it can transmit longer distances with lower power. Many other advantages of the direct sequence spread spectrum technique employed by Zigbee are not discussed here.
9, Zigbee uses the 2.4G free band
In China and most other countries in the world, the general use of radio equipment is subject to frequency usage fees, including mobile communication, but the mobile operator has already paid the fee to the state and has provided the user with the number occupancy fee. This fee was charged. When using other wireless devices, you must first apply for a frequency license from the relevant national authorities, and then charge the amount and amount of power according to the frequency, amount and amount of wireless devices used by your wireless device. This is not a small fee. Generally, equipment costs a few thousand dollars a year. The free frequency band refers to a frequency band that each country divides according to its actual situation and considers the consistency with other countries in the world as much as possible. It is used exclusively for industrial, medical and scientific research (ISM band). A frequency band that can be used free of charge if required. Our country's 2.4G band is such a frequency band. However, in order to ensure that everyone can use it reasonably, the state has limited the use of wireless transceiver equipment in this frequency band in different environments. For example, in an urban environment, the transmission power cannot exceed 100mW.
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