The Most Comprehensive Introduction to ZigBee

The Most Comprehensive Introduction to ZigBee

In the field of smart hardware and the Internet of Things, the well-known ZigBee is undoubtedly recognized by everyone. Apart from Wi-Fi and Bluetooth, ZigBee is currently one of the most important wireless communication protocols, mainly used in the fields of the Internet of Things and smart hardware. The following text introduces various aspects of ZigBee in a question-and-answer format. Without exaggeration, everything you need to know about ZigBee is here!

Origin and History

What technology does ZigBee originate from? During the use of Bluetooth technology, people found that although Bluetooth has many advantages, it still has many shortcomings. For industrial, home automation control, and industrial telemetry fields, Bluetooth technology is too complex, has high power consumption, short range, and small network scale, etc. However, the demand for wireless data communication in industrial automation is becoming increasingly strong, and for industrial sites, this wireless data transmission must be highly reliable and able to resist various electromagnetic interferences present in industrial environments. Therefore, after long-term efforts, the ZigBee protocol was officially launched in mid-2003. Additionally, ZigBee utilized the Home RF Lite communication protocol, which had been researched prior to it, aimed at home networks. What is ZigBee? Firstly, ZigBee is synonymous with the IEEE802.15.4 protocol. According to the technology defined by this protocol, it is a short-range, low-complexity, low-power, low-data-rate, low-cost bidirectional wireless communication technology, mainly suitable for automatic control and remote control fields, which can be embedded in various devices, while also supporting geographical positioning functions. Since bees communicate with their companions about the location and distance of pollen through flying and buzzing (zig) movements, the inventors of ZigBee artistically used this behavior of bees to describe this wireless information transmission technology.

What are the characteristics of ZigBee technology? The characteristics of ZigBee mainly include the following aspects:

  • (1) Low Power Consumption: In low-power standby mode, two AA batteries can support a node to work for 6-24 months, or even longer. This is ZigBee’s outstanding advantage. In comparison, Bluetooth can work for several weeks, while Wi-Fi can work for several hours;

  • (2) Low Cost: By greatly simplifying the protocol, the cost is very low (less than 1/10 of Bluetooth), reducing the requirements for communication controllers. According to predictive analysis, a full-function master node requires 32KB of code when calculated with an 8051 8-bit microcontroller, while sub-functional nodes require as little as 4KB of code, and ZigBee’s protocol is patent-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 generally lies between 10-100m, and can be increased to 1-3km with increased RF transmission power. This refers to the distance between adjacent nodes. If transmission is relayed through routing and communication between nodes, the transmission distance can be further extended;

  • (5) Short Latency: ZigBee’s response speed is relatively fast, generally taking only 15ms to switch from sleep to active state, and 30ms for a node to connect to the network, further saving energy. In comparison, Bluetooth requires 3-10s, and Wi-Fi requires 3s;

  • (6) High Capacity: ZigBee can adopt star, cluster tree, and mesh network structures, with one master node managing several sub-nodes, and a single master node can manage up to 254 sub-nodes; at the same time, the master node can also be managed by a higher-level network node, allowing for the formation of a large network with 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 access to data, and employing Advanced Encryption Standard (AES128) symmetric encryption to flexibly determine its security attributes;

  • (8) License-Free Frequency Band: Uses direct-sequence spread spectrum in the 2.4GHz (global) band for industrial, scientific, and medical applications.

Why is ZigBee said to meet the growing demand for reliable wireless data transmission in industrial automation? ZigBee technology itself emerged because Bluetooth technology could not meet the demand for low data volume, low cost, low power consumption, and high reliability in wireless data communication in industrial automation. For industrial sites, this wireless data transmission must be highly reliable and able to resist various electromagnetic interferences present in industrial environments. ZigBee technology uses a mesh topology, automatic routing, dynamic networking, and direct-sequence spread spectrum methods to meet the needs of industrial automation control sites.

Communication Technology

What protocol does ZigBee use? IEEE802.15.4 protocol, which is a low transmission 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 the remaining protocols mainly refer to and adopt existing standards, with high-level applications, testing, and market promotion being managed by the ZigBee Alliance. Why is the 2.4G frequency band used for ZigBee wireless communication a free frequency band? In China and most other countries around the world, using radio equipment generally requires paying frequency usage fees, including mobile communications. However, mobile operators have already paid this fee to the state and charge users through number occupancy fees, etc. When using other wireless devices, you must first apply for frequency usage permission from the relevant national department, and fees are charged according to the frequency, power, and quantity of your wireless device. 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 countries according to their actual conditions, considering consistency with other countries, specifically for industrial, medical, and scientific research use (ISM band), which can be used free of charge without application. China’s 2.4G band is such a frequency band. However, to ensure reasonable use, the state has imposed corresponding restrictions on the power of wireless transmission devices in different environments. For example, in urban environments, the transmission power cannot exceed 100mW. Is ZigBee only suitable for short-range communication? ZigBee local 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 distant ZigBee control networks via traditional internet. However, when expanding, attention must be paid to: (1) As transmission power increases, power consumption naturally increases, and if power consumption becomes too high, it will lose ZigBee’s inherent advantage of low energy consumption; (2) Although 2.4GHz is a free frequency band, it cannot exceed the maximum power limitation set by the radio wave law. What are the benefits of ZigBee using direct-sequence spread spectrum communication? 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 ability, communication security, and reliability. The ZigBee system, like the CDMA system, uses direct-sequence spread spectrum technology (DSSS), which is highly resistant to interference and has high confidentiality and reliability. If you have used communication products using these two technologies, you will find that they are exceptional in reliability. Since spread spectrum technology requires a low signal-to-noise ratio during normal communication, it can still operate normally in highly interfered environments. According to calculations and experiments, this is equivalent to an increase in receiving sensitivity of 7dBm. It is also less prone to interfere with others. In other words, it can transmit over longer distances using lower power. Below are some references regarding the advantages of spread spectrum technology:

CDMA is a new type of digital cellular technology launched in 1995 following the introduction of digital communication technology worldwide. It utilizes digital transmission methods and employs spread spectrum communication technology, greatly improving frequency utilization, featuring high capacity, wide coverage, low mobile phone power consumption, and high voice quality, thus advancing mobile communication technology to a new stage. The CDMA (Code Division Multiple Access) cellular system has the following outstanding advantages compared to FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access) systems:

  • (1) Good Anti-Interference Performance: Due to CDMA’s spread spectrum processing, it has good anti-interference performance and can coexist with narrowband signals in the same frequency band without affecting normal operation.

  • (2) Strong Multipath Fading Resistance: Multipath fading is a prominent issue affecting mobile communication quality, typically requiring techniques like spatial diversity and adaptive equalization to overcome, along with a significant fading margin. The CDMA system can utilize multipath signals to provide path diversity, which not only alleviates Rayleigh fading but also mitigates slow fading caused by physical obstructions, thus greatly improving communication quality.

  • (3) Increased System Capacity: For FDMA and TDMA, once the frequency points or time slots in a cell are allocated, the cell cannot receive new calls, leading to hard capacity limitations. However, CDMA is an interference-limited system; under specified interference levels, even when the number of users reaches the limit, it still allows for the addition of individual users, albeit with a decline in voice quality. Service providers can balance capacity and voice quality. CDMA’s precise power control and soft handover technology greatly reduce interference signal strength and required signal-to-noise ratio, and effectively utilize techniques such as voice activation or variable rate voice encoding, diversity reception, and power control. Reports indicate that CDMA’s signal-to-noise ratio is 3.7 times that of DAMPS and TDMA, 11.2 times that of TACS, 13.6 times that of AMPS, and 20 times that of FM/FDMA methods.

  • (4) Good Communication Quality: The CDMA system uses direct-sequence spread spectrum technology, comprehensively applying various diversity techniques, including time, frequency, space, and path diversity to overcome multipath effects, achieving strong anti-interference capability. Additionally, it employs a soft handover technique during inter-zone switching, ensuring communication quality, especially during inter-zone switching without ping-pong effects. This system is characterized by wide bandwidth and low noise, allowing for the use of high redundancy error correction coding and efficient digital modulation technology to ensure high-quality voice and data transmission.

  • (5) High Frequency Utilization: The same frequency in the CDMA system can be reused across all cells, with a frequency reuse rate of 2/3 (FDMA and TDMA’s frequency reuse rate is 1/7), eliminating the need for frequency allocation like FDMA and TDMA, greatly simplifying cell splitting and microcell introduction.

  • (6) Strong Multiple Access Capability: The multiple access capability of the CDMA system determines the extent of multiple access interference among spread spectrum codes, which relates to the spread spectrum coding scheme used, the multiple access interference among users sending signals simultaneously (i.e., the correlation characteristics of spread spectrum codes), and the allowable receiving quality (output signal-to-noise ratio). Therefore, the lower the multiple access interference among users working simultaneously, the lower the allowable receiving quality, and the stronger the multiple access capability of CDMA technology.

  • (7) Highly Reliable Confidentiality: The CDMA mobile communication system is a secure communication system. With the addition of certain encryption algorithms, the confidentiality of communication can be greatly enhanced, which cannot be compared to FDMA and TDMA systems. Analyzing the spread spectrum system, capturing someone else’s communication content is nearly impossible. As long as the lithium battery inside does not run out, it alters its sequence’s instantaneous state at a clock frequency of 512KHz. Even with continuous operation, its spread spectrum address sequence period lasts up to 7 years. It also allows for easy configuration and alteration of the main key, subkey, spread spectrum code table, standard encryption algorithms, etc., making communication confidentiality more reliable.

  • (8) Low Mobile Phone Power Consumption: After power control, CDMA only raises the transmission power level during fading periods, thus reducing the average transmission power. The minimum power for FDMA is 5mW, average transmission power is 794 mW, and peak power is 3W, while CDMA’s minimum power is 2.3mW, average transmission power is 5 mW, and peak power is 100mW. This indicates that CDMA’s average and maximum transmission power are lower than FDMA, thereby increasing system capacity, reducing the number of cells, and lowering equipment costs.

What are the characteristics of ZigBee compared to existing data transmission radios? Its advantages are as follows:

  • (1) High Reliability: Due to the higher integration of ZigBee modules compared to general data transmission radios, there are fewer separate components, thus enhancing reliability;

  • (2) Convenient and Safe to Use: Because of its high integration, ZigBee receiver modules can be made very small compared to general data transmission radios, and have low power consumption, with maximum transmission current much smaller than that of a CDMA phone, making them easy to integrate or directly install in devices, not only convenient to use but also less prone to damage when carried outdoors;

  • (3) Strong Anti-Interference Ability, Good Confidentiality, 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 not only require application but also need to pay considerable frequency usage fees to the national wireless committee each year;

  • (5) Low Price: The price of ZigBee data transmission modules is only a fraction of that of similar function data transmission radios.

Network Technology

What kind of wireless data transmission network does ZigBee have? In simple terms, ZigBee is a highly reliable wireless data transmission network, similar to CDMA and GSM networks, where ZigBee data transmission modules are akin to mobile network base stations. Communication distances range from a standard 75 meters to hundreds of meters or kilometers, and it supports wireless expansion. ZigBee is a wireless data transmission network platform consisting of up to 65,000 wireless data transmission modules, very much like existing mobile communication CDMA or GSM networks. Each ZigBee data transmission module is similar to a base station in a mobile network, and they can communicate with each other across the entire network. The distance between each network node can range from the standard 75 meters to several hundred meters or even kilometers after expansion. Unlike mobile communication CDMA or GSM networks, ZigBee networks are primarily established for industrial site automation control data transmission, thus they must be simple, easy to use, reliable in operation, and low in cost. In contrast, mobile communication networks are primarily established for voice communication, with each base station generally costing over a 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. Furthermore, each ZigBee network node (FFD) can wirelessly connect with multiple isolated sub-nodes (RFD) within its signal coverage range. Each ZigBee network node (FFD and RFD) can support up to 31 sensors and controlled devices, with each sensor and controlled device ultimately offering 8 different interface methods. It can collect and transmit both digital and analog signals.What is the self-organizing network adopted by ZigBee? A simple example can explain this issue. When a group of paratroopers land, each holding a ZigBee network module terminal, once they land, as long as they are within communication range of each other, they can quickly form an interconnected ZigBee network by automatically searching for each other. They cannot determine who is where in advance, and due to personnel movement, their connections will change. Therefore, the modules can refresh the existing network by re-searching communication targets. This is the self-organizing network.

Why does ZigBee use a self-organizing network for communication? Mesh network communication is essentially multi-channel communication. In actual industrial sites, due to various reasons, it is often not guaranteed that every wireless channel can remain unobstructed, just like city streets, which may experience temporary interruptions due to accidents or road repairs. At this time, because we have multiple channels, vehicles (equivalent to our control data) can still reach their destination via other routes. This is very important for industrial site control.

Why does the self-organizing network adopt a dynamic routing method? Dynamic routing means that the data transmission path in the network is not predetermined but is searched for before data transmission, analyzing all currently available paths and their positional relationships before selecting one for data transmission. In our network management software, the path selection uses a “gradient method,” meaning that it first selects the nearest path for transmission, and if that path is not available, it will use another path that is slightly further away, and so on until the data reaches its destination. In actual industrial sites, predetermined transmission paths can change at any time, either due to interruptions for various reasons or because they are too busy to transmit timely. Dynamic routing combined with a mesh topology can effectively address this issue, ensuring reliable data transmission.

What are the characteristics of ZigBee compared to existing communication mobile networks (GPRS, CDMA-1X)?

Its characteristics are:

  • (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 expense;

  • (2) Low Equipment Investment: Using mobile networks requires purchasing mobile terminal devices, each priced around 1,000 yuan, while using ZigBee networks, not only are the ZigBee network node modules (equivalent to base stations) each under 1,000 yuan, but the main network sub-nodes (equivalent to mobile phones) are even cheaper;

  • (3) More Reliable Communication: Existing mobile networks are primarily designed for mobile phone communication. Although CDMA-1X and GPRS can conduct 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 considerable guarantee for control data transmission;

  • (4) High Flexibility and Low Cost: Firstly, by using ZigBee network nodes with different coverage distances and functions, along with low-cost wireless transceiver modules from other 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 high-efficiency industrial automation telemetry and control;

  • (5) Although ZigBee is just a local area network compared to existing mobile communication networks, it can “infinitely” expand its coverage by providing sufficient data outlets and can connect with existing mobile networks, the internet, and other communication networks. Through these networks, many ZigBee local area networks can be interconnected to form a whole, effectively addressing the blind spot coverage issues of mobile networks. We know that existing mobile networks have many blind spots, especially in outdoor areas like railways, highways, oil fields, and mines. The cost of adding a mobile base station or repeater is considerable, making ZigBee networks a cost-effective and often the only feasible solution for blind spot coverage.

How does ZigBee achieve long-distance telemetry and control? ZigBee networks can also connect to the internet, GPRS networks, CDMA1x networks, and other communication systems through interface cards and other methods, enabling remote control. You can also connect two or more local ZigBee networks through other networks.

Market Applications

What application areas does ZigBee technology cover? ZigBee technology’s goal is to target industrial, home automation, telemetry and control, such as lighting automation control, wireless data collection and monitoring of sensors, and applications in oil fields, electricity, mining, and logistics management. What requirements for wireless data transmission in industrial sites does ZigBee fulfill? It requires low power consumption, low data volume (250KPS), low cost, use of the free ISM frequency band (2.4G), high anti-interference performance of direct-sequence spread spectrum communication (DSSS), high confidentiality (64-bit factory number and support for AES-128 encryption), high integration, and high reliability; nodes have automatic dynamic networking capabilities, adopting a topology structure that includes mesh networks and using collision avoidance mechanisms, ensuring reliable information transmission throughout the ZigBee network. In what areas can ZigBee expand its applications? ZigBee applications are very broad, targeting industrial automation, home automation, telemetry and control, automotive automation, agricultural automation, medical care, oil fields, electricity, mining, and logistics management, among others. Practical application examples 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 localized areas, such as vehicles in cities. What conditions should short-range communication meet to consider using ZigBee technology? Generally, short-range communication that meets any of the following conditions can consider using ZigBee:

  • (1) A large number of points require data collection or monitoring;

  • (2) The data volume to be transmitted is not large, while low equipment costs are required;

  • (3) High reliability and security of data transmission are required;

  • (4) The equipment size is very small, making it inconvenient to place larger charging batteries or power modules;

  • (5) It can be powered by batteries;

  • (6) Complex terrain with many monitoring points requires large network coverage;

  • (7) Covering blind spots in existing mobile networks;

  • (8) Has already used existing mobile networks for low data volume transmission in telemetry and control systems.

What is the application status of ZigBee technology in China? Although many people in China have begun to pay attention to this new technology, and many companies 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 hardware and software control technology, which poses certain technical difficulties for companies in the early stages of development. Due to various constraints, the large-scale commercial application of ZigBee technology is still pending. However, it has already demonstrated extraordinary application value, and it is believed that with the development and promotion of related technologies, it will see greater application. 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 companies should seize business opportunities, increase investment, and promote the development of the entire industry.

ZigBee Alliance

What is the mission of the ZigBee Alliance? The ZigBee Alliance is a rapidly growing non-profit industry organization, with members including internationally renowned semiconductor manufacturers, technology providers, integrators, and end-users. The Alliance has established application specifications for networks based on IEEE802.15.4, characterized by high reliability, cost-effectiveness, and low power consumption. What is the goal of the ZigBee Alliance? The main goal of the ZigBee Alliance is to provide consumers with more flexible and easier-to-use electronic products by incorporating wireless networking capabilities. ZigBee technology can be integrated into various electronic products, with applications spanning global consumer, commercial, public utility, and industrial markets. This allows Alliance members to utilize the standardized ZigBee wireless network platform to design simple, reliable, cost-effective, and energy-saving products.

What focus areas does the ZigBee Alliance target? Its focus includes establishing network, security, and application software layers; providing interoperability and compatibility testing specifications for different products; promoting the ZigBee brand worldwide and seeking market attention; and managing technological development. What work has the ZigBee Alliance done on standards? The ZigBee standard formulation includes the physical layer, MAC layer, and data link layer of IEEE802.15.4, with the standard released in May 2003. The development of the ZigBee network layer, encryption layer, and application description layer has also made significant progress, with version 1.0 already released. Other application areas and their related device descriptions will be released successively. Since ZigBee is not just a synonym for 802.15.4, and IEEE only handles low-level MAC layer and physical layer protocols, the ZigBee Alliance has standardized its network layer protocols and APIs. The complete protocol is designed for a basic node that can connect directly to a device with 4K bytes or as a coordinator for a hub or router with 32K bytes. Each coordinator can connect up to 255 nodes, and several coordinators can form a network, with no limit on the number of routed transmissions. The ZigBee Alliance has also developed a security layer to ensure that portable devices do not accidentally leak their identity, and that long-distance transmission using the network is not intercepted by other nodes. The ZigBee Alliance emphasizes device interoperability: many short-range electronic products embedded with ZigBee modules already have ZigBee functionality, and many various products have reserved ZigBee interfaces for future upgrades.

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