Guangdong LED
Mainstream Media in the LED Industry: “Guangdong LED” Magazine
Inscription by then Vice Governor of Guangdong Province, Song Hai, supervised by the Provincial Department of Science and Technology, organized by the Provincial Semiconductor Lighting Industry Joint Innovation Center and the Provincial Semiconductor Light Source Industry Association, and hosted by the Shenzhen LED Industry Association (5A level), creating an excellent service platform for LED enterprises with a profound background and rich resources in the LED industry.
Currently, the LED smart lighting industry is flourishing, with various control transmission methods including infrared, WiFi, Bluetooth, and ZigBee. The establishment of standards requires a process, and a consensus has not yet been reached; however, the ZigBee network protocol is the most favored in the industry and is expected to become mainstream in the future.
1. What technology does ZigBee originate from?
A: During the use of Bluetooth technology, people found that despite its many advantages, Bluetooth still had many shortcomings. For industrial and home automation control and industrial telemetry, Bluetooth technology is too complex, consumes too much power, has a short range, and a small network scale… As the demand for wireless data communication in industrial automation becomes increasingly strong, this wireless data transmission must be highly reliable and able to resist various electromagnetic interferences in industrial environments. Therefore, after long-term efforts, the ZigBee protocol was officially launched in mid-2003. Additionally, ZigBee uses the Home RF Lite communication protocol, which was researched prior to it.
2. What is ZigBee?
A: First of all, ZigBee is synonymous with the IEEE802.15.4 protocol. According to the specifications of this protocol, it is a short-range, low-complexity, low-power, low-data-rate, and low-cost bidirectional wireless communication technology, mainly suitable for automatic control and remote control fields, which can be embedded in various devices and also supports geographic positioning functions. The name ZigBee is inspired by the behavior of bees, which communicate the location and distance of pollen through their flight and buzzing dance, thus forming a communication “network” among themselves.
3. What are the characteristics of ZigBee technology?
A: The characteristics of ZigBee mainly include the following eight aspects:
(1) Low power consumption: In low-power standby mode, two AA batteries can support one node for 6-24 months or even longer. This is ZigBee’s outstanding advantage. In comparison, Bluetooth can work for several weeks, and WiFi can work for several hours;
(2) Low cost: The cost is significantly reduced by greatly simplifying the protocol (less than 1/10 of Bluetooth), which also lowers the requirements for communication controllers. According to predictive analysis, a full-function master node requires 32KB of code with an 8051 8-bit microcontroller, while a sub-function node requires as little as 4KB of code, and ZigBee’s protocol patents are free;
(3) Low data rate: ZigBee operates at a communication rate of 250kbps, meeting the application needs for low data rate transmission;
(4) Short range: The transmission range is generally between 10-100m, and can be increased to 1-3km with increased RF transmission power, referring to the distance between adjacent nodes. If communication is relayed through routing and nodes, the transmission distance can be further extended;
(5) Short delay: ZigBee has a fast response speed, generally taking only 15ms to transition from sleep to working state, and 30ms for a node to connect to the network, further saving energy. In comparison, Bluetooth takes 3-10s, and WiFi takes 3s;
(6) High capacity: ZigBee can adopt star, cluster, and mesh network structures, with one master node managing several sub-nodes, and a maximum of one master node can manage 254 sub-nodes; additionally, the master node can also be managed by a higher-level network node, allowing for a large network of up to 65,000 nodes;
(7) High security: ZigBee provides three levels of security modes, including no security settings, using an access control list (ACL) to prevent unauthorized data access, and employing the Advanced Encryption Standard (AES128) for symmetric encryption to flexibly determine its security attributes;
(8) License-free frequency band: It uses direct-sequence spread spectrum in the industrial, scientific, and medical (ISM) 2.4GHz frequency band (global).
4. Why is ZigBee said to meet the growing demand for reliable wireless data transmission in industrial automation?
A: The ZigBee technology itself was developed because Bluetooth technology could not meet the demands for low data volume, low cost, low power consumption, and high reliability in wireless data communication in industrial automation. For industrial environments, this wireless data transmission must be highly reliable and able to resist various electromagnetic interferences. ZigBee technology employs a mesh topology, automatic routing, dynamic networking, and direct-sequence spread spectrum to meet these needs in industrial automation control environments.
5. What protocol does ZigBee use?
A: ZigBee uses the IEEE802.15.4 protocol, which is a low data rate wireless PAN protocol. In terms of standardization, the IEEE802.15.4 working group is mainly responsible for formulating the physical layer and MAC layer protocols, while other protocols mainly refer to and adopt existing standards. The ZigBee Alliance is responsible for high-level applications, testing, and market promotion.
Currently, the wireless personal area networks (WPAN) established by IEEE are roughly four:
1) IEEE 802.15.1 Bluetooth, Bluetooth v1.1;
2) IEEE 802.15.2 Bluetooth, Bluetooth supplementary specification, reducing mutual interference issues when used in conjunction with WiFi;
3) IEEE 802.15.3 WiMEDIA, standard speed, high-speed WPAN; IEEE 802.15.3a UWB, high-speed WPAN;
4) IEEE 802.15.4 ZigBee, low-speed WPAN (also known as WSAN, where S stands for Sensor).
6. Why is the 2.4G frequency band used by ZigBee wireless communication a free frequency band?
A: In China and most other countries around the world, using radio equipment generally requires payment of frequency usage fees, including mobile communications. However, mobile operators have already paid this fee to the state and charge users through number occupancy fees and other means. When using other wireless devices, you must first apply for frequency usage permission from the relevant state department, and fees are charged based on the frequency, power, and quantity of your wireless devices. This can be a significant cost, often amounting to thousands of yuan per year for general equipment.
The free frequency band refers to a band designated by each country based on its actual situation, considering consistency with regulations in other countries, specifically for industrial, medical, and scientific research use (ISM band), which can be used without application. In our country, the 2.4G frequency band is such a band. However, to ensure reasonable use, the state has imposed corresponding restrictions on the power of wireless transceivers in different environments, for example, in urban environments, the transmission power cannot exceed 100mW.
7. Is ZigBee only suitable for short-range communication?
A: ZigBee local area networks can not only expand the network by increasing the transmission power and receiving sensitivity of each node module and increasing the number of nodes, but can also monitor remote ZigBee control networks through traditional internet connections.
However, when expanding, it is important to note:
1) As the transmission power increases, power consumption naturally increases, which may lead to losing ZigBee’s inherent advantage of low energy consumption;
2) Although 2.4GHz is a free frequency band, it cannot exceed the maximum power limits set by radio laws.
8. What are the benefits of ZigBee adopting direct-sequence spread spectrum communication?
A: Different communication methods in the same frequency band can yield significantly different results, such as ASK, FSK, FHSS, DSSS, etc., in terms of anti-interference capability, communication security, and reliability. ZigBee systems, like CDMA systems, use direct-sequence spread spectrum technology (DSSS), which is a highly anti-interference, secure, and reliable communication method. If you have used communication products based on these two technologies, you will find a remarkable difference in reliability.
Due to the low signal-to-noise ratio required for spread spectrum technology during normal communication, it can still operate normally in environments with strong interference. According to calculations and experiments, this is equivalent to an increase in receiving sensitivity of 7dBm, making it less likely to interfere with others. In other words, it can transmit over longer distances using lower power.
9. What are the characteristics of ZigBee compared to existing data transmission radios?
A: Its advantages are as follows:
(1) High reliability: The integration level of ZigBee modules is much higher than that of general data transmission radios, with fewer discrete components, thus ensuring higher reliability;
(2) Convenient and secure to use: Due to high integration, ZigBee receiving modules can be made very small compared to general data transmission radios, and with low power consumption, the maximum transmission current is much lower than that of a CDMA phone, making it easy to integrate or directly place into devices, not only convenient to use but also less prone to damage when carried outdoors;
(3) Strong anti-interference, good confidentiality, and low error rate: ZigBee transceiver modules use 2.4G direct-sequence spread spectrum technology, which has better anti-interference capability and longer transmission distances compared to general FSK, ASK, and frequency-hopping data transmission radios;
(4) Free frequency band: ZigBee uses a free frequency band, while many data transmission radios use frequency bands that require application and annual fees to the national radio administration;
(5) Low price: The price of ZigBee data transmission modules is only a fraction of that of similar-function data transmission radios.
10. What kind of wireless data transmission network does ZigBee have?
A: In simple terms, ZigBee is a highly reliable wireless data transmission network, similar to CDMA and GSM networks, with ZigBee data transmission modules resembling mobile network base stations. The communication distance ranges from a standard 75 meters to several hundred meters or kilometers, and it supports wireless expansion.
ZigBee is a wireless data transmission network platform composed of up to 65,000 wireless data transmission modules, very similar to existing mobile communication CDMA or GSM networks, where each ZigBee data transmission module is akin to a base station in a mobile network, allowing mutual communication within the entire network range; the distance between each network node can range from a standard 75 meters to several hundred meters, or even kilometers when expanded.
Unlike mobile communication CDMA or GSM networks, ZigBee networks are primarily established for data transmission in industrial automation control, thus they must be simple, easy to use, reliable, and low-cost. In contrast, mobile communication networks are mainly established for voice communication, with each base station generally costing over one million yuan, while each ZigBee “base station” costs less than 1,000 yuan. Each ZigBee network node can not only serve as a monitoring object, such as directly collecting and monitoring data from connected sensors, but can also automatically relay data from other network nodes.
In addition, each ZigBee network node (FFD) can wirelessly connect with multiple isolated sub-nodes (RFD) within its signal coverage area. Each ZigBee network node (FFD and RFD) can support up to 31 sensors and controlled devices, with each sensor and controlled device ultimately having eight different interface methods. It can collect and transmit both digital and analog signals.
11. What is the self-organizing network adopted by ZigBee?
A: A simple example can illustrate this issue. When a team of paratroopers lands, each person holds a ZigBee network module terminal. Once they land, as long as they are within the communication range of each other, they can quickly form an interconnected ZigBee network by automatically searching for each other. Due to the movement of personnel, their connections may change, allowing the modules to refresh the original network by re-searching communication partners. This is the self-organizing network.
12. Why does ZigBee use a self-organizing network for communication?
A: Mesh network communication is essentially multi-channel communication. In actual industrial environments, various reasons often prevent every wireless channel from being consistently open, similar to city streets that may be temporarily blocked due to accidents or road repairs. In such cases, having multiple channels allows vehicles (equivalent to our control data) to still reach their destination via alternative routes. This is crucial for industrial control.
13. Why does the self-organizing network adopt a dynamic routing method?
A: Dynamic routing means that the path for data transmission in the network is not predetermined; instead, before transmitting data, all available paths in the network are searched and analyzed based on their positional relationships and distances, and one of these paths is selected for data transmission.
In our network management software, the path selection uses a “gradient method,” which first selects the nearest path for transmission. If it fails, it uses another slightly farther path, and so on, until the data reaches its destination.
In actual industrial environments, predetermined transmission paths can change at any time due to various reasons, or paths may be interrupted or too busy for timely transmission. Dynamic routing combined with mesh topology can effectively solve this problem, ensuring reliable data transmission.
14. What are the characteristics of ZigBee compared to existing mobile communication networks (GPRS, CDMA-1X)?
A: Its characteristics include:
(1) No network usage fees: Using mobile networks requires long-term payment of network usage fees, calculated based on the number of terminal nodes, while ZigBee does not have this fee;
(2) Low equipment investment: Using mobile networks requires purchasing mobile terminal devices, with each terminal priced around 1,000 yuan, while using ZigBee networks not only costs less than 1,000 yuan for each ZigBee network node module (equivalent to a base station), but the price of the main network sub-nodes (equivalent to mobile phones) is even lower;
(3) More reliable communication: Existing mobile networks are primarily designed for mobile phone communication. Although CDMA-1X and GPRS can perform data communication, practice has shown that not only is the communication rate much lower than the designed rate, but the reliability and continuity of data communication are also not guaranteed in many cases. In contrast, ZigBee networks are specifically designed for the transmission of control data, thus ensuring a high level of reliability;
(4) High flexibility and low cost: By using ZigBee network nodes with different coverage distances and functions, as well as low-cost wireless transceiver modules from non-ZigBee systems, a local ZigBee automation control network can be established, which can then be connected to remote computers via the internet or mobile networks, achieving low-cost and efficient industrial automation telemetry and control;
(5) Although ZigBee is only a local area network, it can “infinitely” expand its coverage by providing sufficient data outlets and can connect with existing mobile networks, the internet, and other communication networks, effectively solving the blind spot coverage problem of mobile networks. We know that existing mobile networks have blind spots in many areas, especially in fields like railways, highways, oil fields, and mines. The cost of adding a mobile base station or repeater is considerable, making ZigBee networks an economical and often the only feasible solution for blind spot coverage.
15. How does ZigBee achieve long-distance telemetry and remote control?
A: ZigBee networks can also connect to the internet, GPRS networks, CDMA1x networks, and other communication systems through interface cards and other means, enabling remote control. You can also connect two or more local ZigBee networks together through other networks.
16. What application fields does ZigBee technology cover?
A: The goal of ZigBee technology is to target industrial and home automation, telemetry, and remote control, such as lighting automation control, wireless data collection and monitoring of sensors, power and logistics management, and other application fields.
17. What requirements for wireless data transmission in industrial sites does ZigBee meet?
A: It requires low power consumption, low data volume (250KPS), low cost, use of the free ISM frequency band (2.4G), high anti-interference performance with direct-sequence spread spectrum communication (DSSS), high confidentiality (64-bit factory number and support for AES-128 encryption), high integration, and high reliability; node modules have automatic dynamic networking capabilities, adopting topologies including mesh networks, and using collision avoidance mechanisms to ensure reliable information transmission throughout the ZigBee network.
18. In what areas can ZigBee expand its applications?
A: ZigBee has a very broad application range, targeting industrial automation, home automation, telemetry, automotive automation, agricultural automation, medical care, oil fields, electricity, mining, and logistics management, among other application fields.
Examples of practical applications include lighting control, environmental control, automatic meter reading systems, various curtain controls, smoke sensors, medical monitoring systems, large air conditioning systems, set-top boxes with built-in home control and universal remote controls, heating control, home security, and industrial and building automation. Additionally, it can also locate mobile targets within a localized area, such as vehicles in a city.
19. What conditions should short-range communication meet to consider using ZigBee technology?
A: Generally, short-range communication that meets one of the following conditions can consider applying ZigBee:
(1) Many points require data collection or monitoring;
(2) The amount of data to be transmitted is small, while requiring low equipment costs;
(3) High reliability and security of data transmission are required;
(4) The equipment size must be very small, making it inconvenient to place larger rechargeable batteries or power modules;
(5) Battery power supply is feasible;
(6) Complex terrain with many monitoring points requires extensive network coverage;
(7) Covering blind spots of existing mobile networks;
(8) Existing telemetry and remote control systems using mobile networks for low data volume transmission.
20. What is the application status of ZigBee technology in China?
A: Although many people in China have begun to pay attention to this new technology, and many enterprises have started to engage in the development of ZigBee technology, considering that ZigBee itself is a new system integration technology, the development of application software must combine network transmission, radio frequency technology, and underlying software and hardware control technology, which poses certain technical difficulties for enterprises in the initial development stage.
Due to various constraints, the large-scale commercial application of ZigBee technology is still pending. However, it has already demonstrated extraordinary application value, and with the development and promotion of related technologies, it is believed that it will see greater application in the future.
However, we should also clearly recognize that wireless networks based on ZigBee technology are just beginning to develop, and its technology and applications are far from mature. Domestic enterprises should seize business opportunities, increase investment, and promote the development of the entire industry.
This article is sourced from China LED Network for reference only and does not represent the views or authenticity of Guangdong LED.
