In the field of intelligent hardware and the Internet of Things, the famous ZigBee can be described as nobody knows. In addition to wifi and Bluetooth, ZigBee is currently one of the most important wireless communication protocols and is mainly applied to the Internet of Things and intelligent hardware. Regarding ZigBee, we will introduce you to all aspects in detail in Q&A form. We don't boast that all you need to know about ZigBee is here!
Origin History What is the origin of ZigBee?
During the use of Bluetooth technology, people found that although there are many advantages of Bluetooth technology, there are still many defects. For industry, home automation control and industrial telemetering and remote control, Bluetooth technology is too complex, power consumption, distance, network size is too small, etc... Industrial automation, the demand for wireless data communication is increasingly strong And, for industrial sites, this wireless data transmission must be highly reliable and resistant to various electromagnetic disturbances at the industrial site. Therefore, after a long period of hard work, the ZigBee protocol was officially launched in mid-2003. In addition, ZigBee uses HomeRFLite, a home network-oriented communication protocol that was previously studied.
What is ZigBee?
ZigBee is synonymous with the IEEE 802.15.4 protocol. The technology provided by this agreement is a two-way wireless communication technology that is close range, low complexity, low power consumption, low data rate and low cost. It is mainly suitable for the field of automatic control and remote control, and can be embedded in various devices. Supports geolocation. Since bees are the "dance" of flying and "zig"ly dithering wings to communicate with their peers the position and distance information of the pollen, that is, the bees rely on this way to form the communication in the group. "Network", so ZigBee's inventors vividly use the 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 the low power standby mode, two AA batteries can support 1 node for 6-24 months, or even longer. This is the outstanding advantage of ZigBee. In contrast, Bluetooth can work for several weeks, WiFi can work for several hours;
(2) Low cost: By greatly simplifying the protocol, the cost is very low (less than 1/10 of Bluetooth), and the requirements for the communication controller are reduced. According to the predictive analysis, the 8051's 8-bit microcontroller is used to measure the full-featured master. The node needs 32KB code, the sub-function node is as little as 4KB code, and the ZigBee protocol patent is free;
(3) Low rate: ZigBee operates at a communication rate of 250kbps to meet the application requirements for low-rate data transmission;
(4) Close range: The transmission range is generally between 10 and 100m. After increasing the RF transmit power, it can be increased to 1-3km. This refers to the distance between adjacent nodes. If the relay through the routing and communication between nodes, the transmission distance can be farther;
(5) Short delay: The response speed of ZigBee is faster, generally only 15ms from the transition from sleep to working state, and the node only needs 30ms to enter the network, which further saves energy. In comparison, Bluetooth needs 3-10s, WiFi needs 3s;
(6) High-capacity: ZigBee can use star-shaped, patchy, and meshed network structures. One master node manages several child nodes, and at most one master node can manage 254 child nodes; at the same time, the master node can also be managed by the upper-layer network node. , Can form a large network of up to 65,000 nodes;
(7) High security: ZigBee provides three levels of security modes, including no security settings, use of access control lists (ACLs) to prevent illegal data acquisition, and the use of advanced encryption standard (AES128) symmetric passwords to flexibly determine its security attributes ;
(8) Unlicensed band: Adopts direct sequence spread spectrum in the 2.4 GHz (global) band of industrial scientific medical care.
Why does ZigBee respond to the growing demand for reliable wireless data transmission from industrial automation?
The ZigBee technology itself is because the blue tooth technology cannot meet the demand for low data volume, low cost, low power consumption and high reliability wireless data communication in industrial automation. Because, for industrial sites, this wireless data transmission must be highly reliable and resistant to various electromagnetic disturbances at the industrial site. ZigBee technology uses mesh topology, automatic routing, dynamic networking, and direct-sequence spread spectrum. It is to meet this need of industrial automation control site.
Communication Technology
What kind of protocol does ZigBee use?
The IEEE 802.15.4 protocol, which is a protocol for an unlimited PAN with a low transmission rate. In terms of standardization, the IEEE802.15.4 working group is mainly responsible for formulating the physical layer and MAC layer protocols. The remaining protocols mainly refer to and adopt existing standards. The work of high-level applications, testing, and marketing will be handled by the ZigBee Alliance.
Why is ZigBee wireless communication using 2,4G band free band?
In China and most other countries in the world, the general use of radio equipment is to pay frequency usage fees, including mobile phone communications, but mobile operators have already paid this fee to the country and passed the number occupancy fee to users. Charged this fee. When using other wireless devices, you first need to apply for a frequency license to the relevant national authorities, and then charge fees based on the frequency, power, and quantity of your wireless device. This is a small sum of money, and the average device is usually paid a few thousand dollars a year. The free-frequency bands refer to the frequency bands allocated by each country according to their actual conditions and considering the consistency with other countries' regulations as far as possible, and they are specifically allocated to use in industrial, medical, and scientific research (ISM band). Frequency bands that can be applied for free of charge. Our country’s 2.4G band is such a band. However, in order to ensure that everyone can use it reasonably, the country has made corresponding restrictions on the power usage of radio transceivers in this band in different environments. For example, in an urban environment, the transmit power cannot exceed 100mW.
Is ZigBee suitable only for near field communication?
ZigBee LAN can not only expand the network by increasing the transmit power and receiving sensitivity of each node module, but also increase the number of nodes, and it can also monitor the distant ZigBee control network through the traditional Internet. However, attention must be paid to the expansion: (1) As the transmission power increases, the power consumption naturally increases, and only the power consumption is also large, and the ZigBee itself loses the advantage of low power consumption; (2) Although 2.4Ghz is a free band, it cannot exceed the limit of maximum power in the radio wave method.
What are the advantages of ZigBee direct-sequence spread-spectrum communication?
In the same frequency band, different communication methods may have very different results. For example, the anti-jamming capability of ASK, FSK, FHSS, DSSS, etc., communication security, and reliability are all different. Like the CDMA system, the ZigBee system uses the Direct Sequence Spread Spectrum (DSSS) technology, which is a communication method with strong anti-interference ability and high confidentiality and reliability. If you use these two technologies of communication products, you will find that the two are exceptional in reliability.
Since the signal-to-noise ratio required by the spread spectrum technology in normal communication can be very low, that is, it can still work normally in a very strong interference environment. According to calculations and experiments, this corresponds to a 7 dBm increase in receiver sensitivity. It is also not easy to interfere with others. In other words, it can transmit farther distances with lower power. Here are some references to the superiority of spread spectrum technology for reference:
CDMA is a new type of digital cellular technology introduced in 1995 following the introduction of digital communication technology in the world. It uses digital transmission methods and adopts spread spectrum communication technology, which greatly improves the frequency utilization rate and has a large capacity and coverage. The outstanding advantages of wide, low power consumption and high voice quality will push mobile communication technology to a new stage of development. Compared with FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access) systems, CDMA (Code Division Multiple Access) cellular systems have the following outstanding advantages:
(1) Good anti-interference performance Since CDMA is spread spectrum processing, it has good anti-interference performance and can coexist with the narrowband of the same frequency band without affecting its normal operation.
(2) Strong anti-multipath fading capability Multi-path fading is a prominent problem affecting the quality of mobile communications. Usually, space diversity, adaptive equalization and other techniques must be adopted to overcome them, and there is also a large fading margin. CDMA systems can use multipath signals to provide path diversity. This not only mitigates Rayleigh fading but also mitigates slow fading caused by physical obstructions, thereby greatly improving the quality of communications.
(3) Increase in system capacity For FDMA and TDMA, if the frequency or time slot of the cell is allocated, the cell cannot receive a new call, and the capacity has a hard limit. However, CDMA is an interference-limited system. Even if the number of users reaches a limited number at the specified interference level, individual users are allowed to be added. The disadvantage is that the voice quality is degraded. Service providers can balance capacity and voice quality. The CDMA precise power control and soft handoff techniques greatly reduce the strength of the jammer and the required signal-to-noise ratio requirements, and effectively employ such features as voice activation or variable rate voice coding, diversity reception, and power control. According to reports, the CDMA SNR 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.
(4) Good communication quality The CDMA system uses direct sequence spread spectrum technology to comprehensively apply multiple diversity techniques such as time diversity, frequency diversity, space diversity, and path diversity to overcome multipath effects and obtain strong anti-jamming capability. In the handover, the soft handover technology for establishing the post-interruption is firstly used to ensure the communication quality of the CDMA, especially when there is no ping-pong effect during the handover. The system is a wideband, low-noise ratio. The waveforms allow high-redundancy error correction coding and high-efficiency digital modulation techniques to ensure high-quality voice and data transmission.
(5) High frequency utilization The same frequency of a CDMA system can be reused in all cells with a frequency reuse ratio of 2/3 (frequency reuse ratio of FDMA and TDMA is 1/7). FDMA and TDMA are not required. Frequency configuration is done in that way, which greatly simplifies cell splitting and microcell introduction.
(6) Multiple access capability The CDMA system multi-access capability determines the size of the multiple access interference between spreading codes, which is related to the spreading code scheme used, and the multiple access interference between users transmitting signals simultaneously (ie, spread spectrum coding The correlation characteristic) is related to the allowable reception quality (output SNR), so the lower the multiple access interference between the working users, the lower the allowable reception quality, the stronger the multiple access capability of the CDMA technology.
(7) Highly reliable security The CDMA mobile communication system is a secure communication system. If a certain encryption algorithm technology is added, the communication security performance can be greatly improved. This is unmatched by FDMA and TDMA systems. It is almost impossible to analyze the spread spectrum system adopted by it. It is impossible to intercept other people's communication content. For example, as long as the lithium battery inside the battery is not discharged, it changes the instantaneous state of the sequence at a clock frequency of 512KHz, even if it is continuously working. Its spread-spectrum address sequence has a period of up to 7 years. It can also conveniently set and change the master key, secondary key, spread spectrum code table, and standard encryption algorithms in the CDMA system, making the confidentiality of communications more reliable.
(8) Mobile phone power consumption After CDMA adopts power control, the transmit power level is increased only during fading, so that the average transmit power is reduced, the minimum power of FDMA is 5mW, the average transmit power is 794mW, and the peak power is 3W. The CDMA minimum power is 2.3mW, the average transmit power is 5mW, and the peak power is 100mW. It can be seen that the average transmit power and the maximum transmit power of CDMA are lower than those of FDMA, thereby increasing the system capacity, reducing the number of cells and reducing the equipment cost.
What are the characteristics of ZigBee and existing digital radio stations?
Its advantages are as follows:
(1) High reliability: Because the ZigBee module is far more integrated than a general data transmission radio, the number of discrete components is small, so the reliability is higher.
(2) Convenient and safe to use: Because of its high level of integration, the ZigBee receiving module can be made smaller in size than conventional data transmission radios, and its power consumption is low. The maximum emission current is much smaller than a CDMA mobile phone. Easy to integrate or directly placed in the device, not only easy to use, but also not easily damaged when carried outdoors.
(3) Strong anti-jamming capability, good confidentiality, and low bit error rate: The ZigBee transceiver module uses 2.4G direct sequence spread spectrum technology, which is better than general FSK, ASK and frequency hopping digital radio stations. Anti-interference ability, and more distant transmission distance;
(4) Free frequency band: ZigBee uses the free frequency band, and the frequency bands used by many digital radio stations not only need to apply, but also need to pay the National Radio Committee a considerable frequency usage fee every year;
(5) Low price: The price of the ZigBee data transmission module is only a fraction of that of a digital radio station with similar functions.
Network Technology
What kind of wireless data transmission network does ZigBee have?
Simply put, ZigBee is a highly reliable wireless data transmission network. Similar to CDMA and GSM networks, the ZigBee data transmission module is similar to a mobile network base station. The communication distance is from standard 75 meters to several hundred meters, a few kilometers, and supports wireless expansion.
ZigBee is a wireless data transmission network platform composed of up to 65,000 wireless data transmission modules. It is similar to the existing mobile communication CDMA network or GSM network. Each ZigBee network data transmission module is similar to a base station of a mobile network. Within the entire network, they can communicate with each other; the distance between each network node can range from standard 75 meters to several hundred meters or even several kilometers after expansion.
Different from the CDMA network or the GSM network of mobile communication, the ZigBee network is mainly established for industrial field automation control of 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 base station is generally more than one million yuan, and each ZigBee "base station" is less than 1,000 yuan. Each ZigBee network node not only can be used as a monitoring object itself, for example, the sensors connected to it directly perform data collection and monitoring, and can also automatically transfer data data transmitted from other network nodes. In addition, each ZigBee network node (FFD) can also wirelessly connect to isolated child nodes (RFDs) that do not undertake network information relay tasks within the coverage of their own signals.
Each ZigBee network node (FFD and RFD) can support up to 31 sensors and controlled devices. Each sensor and controlled device can finally have 8 different interface modes. Digital and analog quantities can be collected and transmitted.
What is the self-organizing network used by ZigBee?
A simple example can illustrate this problem. When a team of parachutists airborne, each person holds a ZigBee network module terminal and lands on the ground. As long as they are within the communication range of the network module, they automatically find each other. A connected ZigBee network will soon be formed. They can't determine who is in the rain beforehand, and because of the movement of people, the contact between them will change. Therefore, the module can also refresh the original network by re-finding the communication objects and confirming the liaison between them. This is self-organizing.
Why does ZigBee technology use the ad hoc network to communicate?
Mesh communication is actually multi-channel communication. In actual industrial scenes, due to various reasons, it is not always possible to ensure that every wireless channel can always be unimpeded. Like a city street, it may be due to a car accident, road maintenance, etc. There is a temporary interruption of traffic on a road. At this time, because we have multiple passages, vehicles (equivalent to our control data) can still reach other destinations through other roads. This is very important for industrial field control.
Why do self-organizing networks use dynamic routing?
The so-called dynamic routing means that the data transmission path in the network is not set in advance, but before the data is transmitted, all paths available at the time of the network are searched, their position relationships and distances are analyzed, and then one path is selected. 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 first, and if it fails, it is transmitted using another, slightly farther path, and so on. Until the data arrives at the destination. In an actual industrial site, a predetermined transmission path may change at any time, or the path may be interrupted due to various reasons, or may be too busy for timely transmission. Dynamic routing combined with the topology of the mesh network can solve this problem well and ensure the reliable transmission of data.
What are the characteristics of ZigBee and existing communication mobile networks (GPRS, CDMA-1X)?
Its characteristics are:
(1) No network usage fees: The use of mobile networks requires long-term payment of network usage fees, which is calculated on the basis of the number of node terminals, and ZigBee does not have this fee;
(2) Low equipment investment: The use of mobile networks requires the purchase of mobile terminal equipment. The price of each terminal is up to RMB 1,000. However, using ZigBee networks, the cost of not only ZigBee network node modules (equivalent to base stations) is less than RMB 1,000 per RMB And, the price of the main network sub-nodes (equivalent to mobile phones) is much lower;
(3) The communication is more reliable: Since the existing mobile network is mainly designed for mobile communication, although CDMA-1X and GPRS can perform data communication, it has been found in practice that not only the communication rate is much lower than the design rate, but also the reliability of data communication. Letters and continuity are not guaranteed in many cases. The ZigBee network is specifically designed to control the transmission of data, so control data transmission has a considerable guarantee;
(4) High flexibility and low cost: First, a ZigBee local automation network is established by using ZigBee network nodes with different coverage distances and functions, and other low-cost wireless transceiver modules that are not ZigBee systems. The Internet or mobile network is connected to a remote computer so as to realize low cost and high efficiency remote control of industrial automation telemetry;
(5) Compared to the existing mobile communication network, although ZigBee is only a local area network, it can expand its coverage "infinitely" by providing sufficient data exports, and it can communicate with existing mobile networks, the Internet and Other communication networks are connected. And through these networks, many ZigBee LANs are connected to one another. Effectively solve the problem of blind coverage of mobile networks: We know that existing mobile networks have blind areas in many places, especially railways, highways, oil fields, and mines. The cost of adding a mobile base station or repeater is considerable. At this time, using ZigBee network for blind coverage is not only cost-effective, but it is often the only feasible method.
How does ZigBee achieve remote telemetry remote control?
The ZigBee network can also be connected to the Internet, GPRS network, CDMA1x network, and other communication system lines through various methods such as interface cards to achieve remote control. You can also connect two or more local ZigBee networks through other networks.
Market Application
What are the application areas of ZigBee technology?
The ZigBee technology aims to address, industrial, home automation, telemetry and remote control, such as automated lighting control, wireless data acquisition and monitoring of sensors, oil fields, power, mining and logistics management applications.
What industry requirements for wireless data transmission have ZigBee achieved?
Requires low power consumption, low data volume (250KPS), low cost, use of free ISM band (2.4G), high anti-jamming performance of direct sequence spread spectrum communication (DSSS), high security (64-bit factory number and Supports AES-128 encryption, high integration and high reliability; automatic dynamic networking between node modules, topological structure including mesh network, collision avoidance mechanism, and information throughout ZigBee In the network, transmission is performed through automatic routing, which ensures the reliability of information transmission.
Where can ZigBee expand applications?
ZigBee application: Its range is very wide, and it can be used in industrial automation, home automation, remote telemetry, automotive automation, agricultural automation and medical care, oil fields, electricity, mining and logistics management applications. Examples of practical applications include: lighting control, environmental control, automatic meter reading systems, various types of curtain control, smoke sensors, medical monitoring systems, large-scale air conditioning systems, built-in home-control set-top boxes and universal remote controls, heating control, home security, industrial and Building automation. In addition, it can also locate moving objects in a local area, such as vehicles in a city.
Where can the ZigBee technology be considered for short-range communications?
In general, ZigBee can be considered for short-range communications that meet one of the following conditions:
(1) There are many outlets that require data collection or monitoring;
(2) The amount of data required to be transmitted is not large, but requires low equipment cost;
(3) It requires high data transmission reliability and high security;
(4) The required equipment is very small, so it is not convenient to place a large rechargeable battery or power supply module;
(5) Battery-powered;
(6) The terrain is complex, there are many monitoring points and large network coverage is required;
(7) Coverage of those existing blind spots of mobile networks;
(8) Remote telemetry systems that use existing mobile networks for low data transmission.
What is the application of ZigBee technology in China?
Although many people in China have begun to pay attention to the new ZigBee technology, and many companies have begun to get involved in the development of ZigBee technology, however, considering that ZigBee itself is a new system integration technology, the development of application software must use network transmission. The combination of radio frequency technology and the underlying hardware and software control technology has certain technical difficulties for the initial development of the enterprise. Due to various constraints, large-scale commercial applications of ZigBee technology will take time. However, it has already demonstrated extraordinary application value. It is believed that with the development and advancement of related technologies, greater applications will surely be obtained. However, we should also clearly understand that wireless networks based on ZigBee technology have only just begun to develop. Their technologies and applications are still far from mature. Domestic enterprises should seize business opportunities, increase investment, and promote the entire industry. development of.
ZigBee Alliance
What is the mission of the ZigBee Alliance?
The ZigBee Alliance is a rapidly growing non-profit industry organization that includes internationally renowned semiconductor manufacturers, technology providers, technology integrators, and end users. The Alliance has developed a network application specification based on IEEE802.15.4 with 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 adding wireless network capabilities. ZigBee technology can be integrated into all kinds of electronic products, and its application range spans markets in the civil, commercial, public utility, and industrial markets worldwide. This allows affiliates to use ZigBee, a standardized wireless network platform, to design simple, reliable, inexpensive and power-saving products.
What is the focus of the ZigBee Alliance?
Its focus is to develop the network, security and application software layer; provide coordination and interoperability testing specifications for different products; promote the ZigBee brand around the world and strive for market attention; management technology development.
What is the work done by the ZigBee Alliance on standards?
The ZigBee standard was established: IEEE 802.15.4 physical layer, MAC layer, and data link layer. The standard was released in May 2003. The ZigBee network layer, encryption layer and application description layer have also made significant progress. Version V1.0 has been released. Other application areas and related device descriptions will also be released. Since ZigBee is not only synonymous with 802.15.4, but the IEEE only deals with low-level MAC layer and physical layer protocols, the ZigBee Alliance standardized its network layer protocols and APIs. Full protocol is used for 4K bytes of a basic node that can be directly connected to one device at a time or 32K bytes that is a coordinator of a hub or router. Each coordinator can connect up to 255 nodes, and several coordinators can form a network with no restrictions on the number of route transmissions. The ZigBee Alliance has also developed a security layer to ensure that such portable devices do not accidentally leak their logos, and that such long-distance transmission using the network is not available to other nodes.
The ZigBee Alliance emphasizes the interoperability of devices: Many ZigBee modules embedded in close-range electronic products already have ZigBee functionality, and many other products have ZigBee interfaces reserved for future upgrades. The development of various gateway products has also been further developed. Gateway products support the interconnection of existing facilities such as the ZigBee system and home control networks, intelligent building networks and commercial networks.
Origin History What is the origin of ZigBee?
During the use of Bluetooth technology, people found that although there are many advantages of Bluetooth technology, there are still many defects. For industry, home automation control and industrial telemetering and remote control, Bluetooth technology is too complex, power consumption, distance, network size is too small, etc... Industrial automation, the demand for wireless data communication is increasingly strong And, for industrial sites, this wireless data transmission must be highly reliable and resistant to various electromagnetic disturbances at the industrial site. Therefore, after a long period of hard work, the ZigBee protocol was officially launched in mid-2003. In addition, ZigBee uses HomeRFLite, a home network-oriented communication protocol that was previously studied.
What is ZigBee?
ZigBee is synonymous with the IEEE 802.15.4 protocol. The technology provided by this agreement is a two-way wireless communication technology that is close range, low complexity, low power consumption, low data rate and low cost. It is mainly suitable for the field of automatic control and remote control, and can be embedded in various devices. Supports geolocation. Since bees are the "dance" of flying and "zig"ly dithering wings to communicate with their peers the position and distance information of the pollen, that is, the bees rely on this way to form the communication in the group. "Network", so ZigBee's inventors vividly use the 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 the low power standby mode, two AA batteries can support 1 node for 6-24 months, or even longer. This is the outstanding advantage of ZigBee. In contrast, Bluetooth can work for several weeks, WiFi can work for several hours;
(2) Low cost: By greatly simplifying the protocol, the cost is very low (less than 1/10 of Bluetooth), and the requirements for the communication controller are reduced. According to the predictive analysis, the 8051's 8-bit microcontroller is used to measure the full-featured master. The node needs 32KB code, the sub-function node is as little as 4KB code, and the ZigBee protocol patent is free;
(3) Low rate: ZigBee operates at a communication rate of 250kbps to meet the application requirements for low-rate data transmission;
(4) Close range: The transmission range is generally between 10 and 100m. After increasing the RF transmit power, it can be increased to 1-3km. This refers to the distance between adjacent nodes. If the relay through the routing and communication between nodes, the transmission distance can be farther;
(5) Short delay: The response speed of ZigBee is faster, generally only 15ms from the transition from sleep to working state, and the node only needs 30ms to enter the network, which further saves energy. In comparison, Bluetooth needs 3-10s, WiFi needs 3s;
(6) High-capacity: ZigBee can use star-shaped, patchy, and meshed network structures. One master node manages several child nodes, and at most one master node can manage 254 child nodes; at the same time, the master node can also be managed by the upper-layer network node. , Can form a large network of up to 65,000 nodes;
(7) High security: ZigBee provides three levels of security modes, including no security settings, use of access control lists (ACLs) to prevent illegal data acquisition, and the use of advanced encryption standard (AES128) symmetric passwords to flexibly determine its security attributes ;
(8) Unlicensed band: Adopts direct sequence spread spectrum in the 2.4 GHz (global) band of industrial scientific medical care.
Why does ZigBee respond to the growing demand for reliable wireless data transmission from industrial automation?
The ZigBee technology itself is because the blue tooth technology cannot meet the demand for low data volume, low cost, low power consumption and high reliability wireless data communication in industrial automation. Because, for industrial sites, this wireless data transmission must be highly reliable and resistant to various electromagnetic disturbances at the industrial site. ZigBee technology uses mesh topology, automatic routing, dynamic networking, and direct-sequence spread spectrum. It is to meet this need of industrial automation control site.
Communication Technology
What kind of protocol does ZigBee use?
The IEEE 802.15.4 protocol, which is a protocol for an unlimited PAN with a low transmission rate. In terms of standardization, the IEEE802.15.4 working group is mainly responsible for formulating the physical layer and MAC layer protocols. The remaining protocols mainly refer to and adopt existing standards. The work of high-level applications, testing, and marketing will be handled by the ZigBee Alliance.
Why is ZigBee wireless communication using 2,4G band free band?
In China and most other countries in the world, the general use of radio equipment is to pay frequency usage fees, including mobile phone communications, but mobile operators have already paid this fee to the country and passed the number occupancy fee to users. Charged this fee. When using other wireless devices, you first need to apply for a frequency license to the relevant national authorities, and then charge fees based on the frequency, power, and quantity of your wireless device. This is a small sum of money, and the average device is usually paid a few thousand dollars a year. The free-frequency bands refer to the frequency bands allocated by each country according to their actual conditions and considering the consistency with other countries' regulations as far as possible, and they are specifically allocated to use in industrial, medical, and scientific research (ISM band). Frequency bands that can be applied for free of charge. Our country’s 2.4G band is such a band. However, in order to ensure that everyone can use it reasonably, the country has made corresponding restrictions on the power usage of radio transceivers in this band in different environments. For example, in an urban environment, the transmit power cannot exceed 100mW.
Is ZigBee suitable only for near field communication?
ZigBee LAN can not only expand the network by increasing the transmit power and receiving sensitivity of each node module, but also increase the number of nodes, and it can also monitor the distant ZigBee control network through the traditional Internet. However, attention must be paid to the expansion: (1) As the transmission power increases, the power consumption naturally increases, and only the power consumption is also large, and the ZigBee itself loses the advantage of low power consumption; (2) Although 2.4Ghz is a free band, it cannot exceed the limit of maximum power in the radio wave method.
What are the advantages of ZigBee direct-sequence spread-spectrum communication?
In the same frequency band, different communication methods may have very different results. For example, the anti-jamming capability of ASK, FSK, FHSS, DSSS, etc., communication security, and reliability are all different. Like the CDMA system, the ZigBee system uses the Direct Sequence Spread Spectrum (DSSS) technology, which is a communication method with strong anti-interference ability and high confidentiality and reliability. If you use these two technologies of communication products, you will find that the two are exceptional in reliability.
Since the signal-to-noise ratio required by the spread spectrum technology in normal communication can be very low, that is, it can still work normally in a very strong interference environment. According to calculations and experiments, this corresponds to a 7 dBm increase in receiver sensitivity. It is also not easy to interfere with others. In other words, it can transmit farther distances with lower power. Here are some references to the superiority of spread spectrum technology for reference:
CDMA is a new type of digital cellular technology introduced in 1995 following the introduction of digital communication technology in the world. It uses digital transmission methods and adopts spread spectrum communication technology, which greatly improves the frequency utilization rate and has a large capacity and coverage. The outstanding advantages of wide, low power consumption and high voice quality will push mobile communication technology to a new stage of development. Compared with FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access) systems, CDMA (Code Division Multiple Access) cellular systems have the following outstanding advantages:
(1) Good anti-interference performance Since CDMA is spread spectrum processing, it has good anti-interference performance and can coexist with the narrowband of the same frequency band without affecting its normal operation.
(2) Strong anti-multipath fading capability Multi-path fading is a prominent problem affecting the quality of mobile communications. Usually, space diversity, adaptive equalization and other techniques must be adopted to overcome them, and there is also a large fading margin. CDMA systems can use multipath signals to provide path diversity. This not only mitigates Rayleigh fading but also mitigates slow fading caused by physical obstructions, thereby greatly improving the quality of communications.
(3) Increase in system capacity For FDMA and TDMA, if the frequency or time slot of the cell is allocated, the cell cannot receive a new call, and the capacity has a hard limit. However, CDMA is an interference-limited system. Even if the number of users reaches a limited number at the specified interference level, individual users are allowed to be added. The disadvantage is that the voice quality is degraded. Service providers can balance capacity and voice quality. The CDMA precise power control and soft handoff techniques greatly reduce the strength of the jammer and the required signal-to-noise ratio requirements, and effectively employ such features as voice activation or variable rate voice coding, diversity reception, and power control. According to reports, the CDMA SNR 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.
(4) Good communication quality The CDMA system uses direct sequence spread spectrum technology to comprehensively apply multiple diversity techniques such as time diversity, frequency diversity, space diversity, and path diversity to overcome multipath effects and obtain strong anti-jamming capability. In the handover, the soft handover technology for establishing the post-interruption is firstly used to ensure the communication quality of the CDMA, especially when there is no ping-pong effect during the handover. The system is a wideband, low-noise ratio. The waveforms allow high-redundancy error correction coding and high-efficiency digital modulation techniques to ensure high-quality voice and data transmission.
(5) High frequency utilization The same frequency of a CDMA system can be reused in all cells with a frequency reuse ratio of 2/3 (frequency reuse ratio of FDMA and TDMA is 1/7). FDMA and TDMA are not required. Frequency configuration is done in that way, which greatly simplifies cell splitting and microcell introduction.
(6) Multiple access capability The CDMA system multi-access capability determines the size of the multiple access interference between spreading codes, which is related to the spreading code scheme used, and the multiple access interference between users transmitting signals simultaneously (ie, spread spectrum coding The correlation characteristic) is related to the allowable reception quality (output SNR), so the lower the multiple access interference between the working users, the lower the allowable reception quality, the stronger the multiple access capability of the CDMA technology.
(7) Highly reliable security The CDMA mobile communication system is a secure communication system. If a certain encryption algorithm technology is added, the communication security performance can be greatly improved. This is unmatched by FDMA and TDMA systems. It is almost impossible to analyze the spread spectrum system adopted by it. It is impossible to intercept other people's communication content. For example, as long as the lithium battery inside the battery is not discharged, it changes the instantaneous state of the sequence at a clock frequency of 512KHz, even if it is continuously working. Its spread-spectrum address sequence has a period of up to 7 years. It can also conveniently set and change the master key, secondary key, spread spectrum code table, and standard encryption algorithms in the CDMA system, making the confidentiality of communications more reliable.
(8) Mobile phone power consumption After CDMA adopts power control, the transmit power level is increased only during fading, so that the average transmit power is reduced, the minimum power of FDMA is 5mW, the average transmit power is 794mW, and the peak power is 3W. The CDMA minimum power is 2.3mW, the average transmit power is 5mW, and the peak power is 100mW. It can be seen that the average transmit power and the maximum transmit power of CDMA are lower than those of FDMA, thereby increasing the system capacity, reducing the number of cells and reducing the equipment cost.
What are the characteristics of ZigBee and existing digital radio stations?
Its advantages are as follows:
(1) High reliability: Because the ZigBee module is far more integrated than a general data transmission radio, the number of discrete components is small, so the reliability is higher.
(2) Convenient and safe to use: Because of its high level of integration, the ZigBee receiving module can be made smaller in size than conventional data transmission radios, and its power consumption is low. The maximum emission current is much smaller than a CDMA mobile phone. Easy to integrate or directly placed in the device, not only easy to use, but also not easily damaged when carried outdoors.
(3) Strong anti-jamming capability, good confidentiality, and low bit error rate: The ZigBee transceiver module uses 2.4G direct sequence spread spectrum technology, which is better than general FSK, ASK and frequency hopping digital radio stations. Anti-interference ability, and more distant transmission distance;
(4) Free frequency band: ZigBee uses the free frequency band, and the frequency bands used by many digital radio stations not only need to apply, but also need to pay the National Radio Committee a considerable frequency usage fee every year;
(5) Low price: The price of the ZigBee data transmission module is only a fraction of that of a digital radio station with similar functions.
Network Technology
What kind of wireless data transmission network does ZigBee have?
Simply put, ZigBee is a highly reliable wireless data transmission network. Similar to CDMA and GSM networks, the ZigBee data transmission module is similar to a mobile network base station. The communication distance is from standard 75 meters to several hundred meters, a few kilometers, and supports wireless expansion.
ZigBee is a wireless data transmission network platform composed of up to 65,000 wireless data transmission modules. It is similar to the existing mobile communication CDMA network or GSM network. Each ZigBee network data transmission module is similar to a base station of a mobile network. Within the entire network, they can communicate with each other; the distance between each network node can range from standard 75 meters to several hundred meters or even several kilometers after expansion.
Different from the CDMA network or the GSM network of mobile communication, the ZigBee network is mainly established for industrial field automation control of 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 base station is generally more than one million yuan, and each ZigBee "base station" is less than 1,000 yuan. Each ZigBee network node not only can be used as a monitoring object itself, for example, the sensors connected to it directly perform data collection and monitoring, and can also automatically transfer data data transmitted from other network nodes. In addition, each ZigBee network node (FFD) can also wirelessly connect to isolated child nodes (RFDs) that do not undertake network information relay tasks within the coverage of their own signals.
Each ZigBee network node (FFD and RFD) can support up to 31 sensors and controlled devices. Each sensor and controlled device can finally have 8 different interface modes. Digital and analog quantities can be collected and transmitted.
What is the self-organizing network used by ZigBee?
A simple example can illustrate this problem. When a team of parachutists airborne, each person holds a ZigBee network module terminal and lands on the ground. As long as they are within the communication range of the network module, they automatically find each other. A connected ZigBee network will soon be formed. They can't determine who is in the rain beforehand, and because of the movement of people, the contact between them will change. Therefore, the module can also refresh the original network by re-finding the communication objects and confirming the liaison between them. This is self-organizing.
Why does ZigBee technology use the ad hoc network to communicate?
Mesh communication is actually multi-channel communication. In actual industrial scenes, due to various reasons, it is not always possible to ensure that every wireless channel can always be unimpeded. Like a city street, it may be due to a car accident, road maintenance, etc. There is a temporary interruption of traffic on a road. At this time, because we have multiple passages, vehicles (equivalent to our control data) can still reach other destinations through other roads. This is very important for industrial field control.
Why do self-organizing networks use dynamic routing?
The so-called dynamic routing means that the data transmission path in the network is not set in advance, but before the data is transmitted, all paths available at the time of the network are searched, their position relationships and distances are analyzed, and then one path is selected. 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 first, and if it fails, it is transmitted using another, slightly farther path, and so on. Until the data arrives at the destination. In an actual industrial site, a predetermined transmission path may change at any time, or the path may be interrupted due to various reasons, or may be too busy for timely transmission. Dynamic routing combined with the topology of the mesh network can solve this problem well and ensure the reliable transmission of data.
What are the characteristics of ZigBee and existing communication mobile networks (GPRS, CDMA-1X)?
Its characteristics are:
(1) No network usage fees: The use of mobile networks requires long-term payment of network usage fees, which is calculated on the basis of the number of node terminals, and ZigBee does not have this fee;
(2) Low equipment investment: The use of mobile networks requires the purchase of mobile terminal equipment. The price of each terminal is up to RMB 1,000. However, using ZigBee networks, the cost of not only ZigBee network node modules (equivalent to base stations) is less than RMB 1,000 per RMB And, the price of the main network sub-nodes (equivalent to mobile phones) is much lower;
(3) The communication is more reliable: Since the existing mobile network is mainly designed for mobile communication, although CDMA-1X and GPRS can perform data communication, it has been found in practice that not only the communication rate is much lower than the design rate, but also the reliability of data communication. Letters and continuity are not guaranteed in many cases. The ZigBee network is specifically designed to control the transmission of data, so control data transmission has a considerable guarantee;
(4) High flexibility and low cost: First, a ZigBee local automation network is established by using ZigBee network nodes with different coverage distances and functions, and other low-cost wireless transceiver modules that are not ZigBee systems. The Internet or mobile network is connected to a remote computer so as to realize low cost and high efficiency remote control of industrial automation telemetry;
(5) Compared to the existing mobile communication network, although ZigBee is only a local area network, it can expand its coverage "infinitely" by providing sufficient data exports, and it can communicate with existing mobile networks, the Internet and Other communication networks are connected. And through these networks, many ZigBee LANs are connected to one another. Effectively solve the problem of blind coverage of mobile networks: We know that existing mobile networks have blind areas in many places, especially railways, highways, oil fields, and mines. The cost of adding a mobile base station or repeater is considerable. At this time, using ZigBee network for blind coverage is not only cost-effective, but it is often the only feasible method.
How does ZigBee achieve remote telemetry remote control?
The ZigBee network can also be connected to the Internet, GPRS network, CDMA1x network, and other communication system lines through various methods such as interface cards to achieve remote control. You can also connect two or more local ZigBee networks through other networks.
Market Application
What are the application areas of ZigBee technology?
The ZigBee technology aims to address, industrial, home automation, telemetry and remote control, such as automated lighting control, wireless data acquisition and monitoring of sensors, oil fields, power, mining and logistics management applications.
What industry requirements for wireless data transmission have ZigBee achieved?
Requires low power consumption, low data volume (250KPS), low cost, use of free ISM band (2.4G), high anti-jamming performance of direct sequence spread spectrum communication (DSSS), high security (64-bit factory number and Supports AES-128 encryption, high integration and high reliability; automatic dynamic networking between node modules, topological structure including mesh network, collision avoidance mechanism, and information throughout ZigBee In the network, transmission is performed through automatic routing, which ensures the reliability of information transmission.
Where can ZigBee expand applications?
ZigBee application: Its range is very wide, and it can be used in industrial automation, home automation, remote telemetry, automotive automation, agricultural automation and medical care, oil fields, electricity, mining and logistics management applications. Examples of practical applications include: lighting control, environmental control, automatic meter reading systems, various types of curtain control, smoke sensors, medical monitoring systems, large-scale air conditioning systems, built-in home-control set-top boxes and universal remote controls, heating control, home security, industrial and Building automation. In addition, it can also locate moving objects in a local area, such as vehicles in a city.
Where can the ZigBee technology be considered for short-range communications?
In general, ZigBee can be considered for short-range communications that meet one of the following conditions:
(1) There are many outlets that require data collection or monitoring;
(2) The amount of data required to be transmitted is not large, but requires low equipment cost;
(3) It requires high data transmission reliability and high security;
(4) The required equipment is very small, so it is not convenient to place a large rechargeable battery or power supply module;
(5) Battery-powered;
(6) The terrain is complex, there are many monitoring points and large network coverage is required;
(7) Coverage of those existing blind spots of mobile networks;
(8) Remote telemetry systems that use existing mobile networks for low data transmission.
What is the application of ZigBee technology in China?
Although many people in China have begun to pay attention to the new ZigBee technology, and many companies have begun to get involved in the development of ZigBee technology, however, considering that ZigBee itself is a new system integration technology, the development of application software must use network transmission. The combination of radio frequency technology and the underlying hardware and software control technology has certain technical difficulties for the initial development of the enterprise. Due to various constraints, large-scale commercial applications of ZigBee technology will take time. However, it has already demonstrated extraordinary application value. It is believed that with the development and advancement of related technologies, greater applications will surely be obtained. However, we should also clearly understand that wireless networks based on ZigBee technology have only just begun to develop. Their technologies and applications are still far from mature. Domestic enterprises should seize business opportunities, increase investment, and promote the entire industry. development of.
ZigBee Alliance
What is the mission of the ZigBee Alliance?
The ZigBee Alliance is a rapidly growing non-profit industry organization that includes internationally renowned semiconductor manufacturers, technology providers, technology integrators, and end users. The Alliance has developed a network application specification based on IEEE802.15.4 with 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 adding wireless network capabilities. ZigBee technology can be integrated into all kinds of electronic products, and its application range spans markets in the civil, commercial, public utility, and industrial markets worldwide. This allows affiliates to use ZigBee, a standardized wireless network platform, to design simple, reliable, inexpensive and power-saving products.
What is the focus of the ZigBee Alliance?
Its focus is to develop the network, security and application software layer; provide coordination and interoperability testing specifications for different products; promote the ZigBee brand around the world and strive for market attention; management technology development.
What is the work done by the ZigBee Alliance on standards?
The ZigBee standard was established: IEEE 802.15.4 physical layer, MAC layer, and data link layer. The standard was released in May 2003. The ZigBee network layer, encryption layer and application description layer have also made significant progress. Version V1.0 has been released. Other application areas and related device descriptions will also be released. Since ZigBee is not only synonymous with 802.15.4, but the IEEE only deals with low-level MAC layer and physical layer protocols, the ZigBee Alliance standardized its network layer protocols and APIs. Full protocol is used for 4K bytes of a basic node that can be directly connected to one device at a time or 32K bytes that is a coordinator of a hub or router. Each coordinator can connect up to 255 nodes, and several coordinators can form a network with no restrictions on the number of route transmissions. The ZigBee Alliance has also developed a security layer to ensure that such portable devices do not accidentally leak their logos, and that such long-distance transmission using the network is not available to other nodes.
The ZigBee Alliance emphasizes the interoperability of devices: Many ZigBee modules embedded in close-range electronic products already have ZigBee functionality, and many other products have ZigBee interfaces reserved for future upgrades. The development of various gateway products has also been further developed. Gateway products support the interconnection of existing facilities such as the ZigBee system and home control networks, intelligent building networks and commercial networks.
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