1. 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 industrial, home automation control and industrial telemetry and remote control applications, Bluetooth technology is too complex, power consumption, distance, network size is too small, and industrial automation, the demand for wireless data communications 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-based communication protocol that was studied before it.
2. What is ZigBee?
First of all, ZigBee's MAC layer and PHY layer are IEEE 802.15.4 protocols. 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 a 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?
3, ZigBee features are mainly 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 10m 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 power. 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: Uses the Industrial Scientific Medical (ISM) band, 915 MHz (United States), 868 MHz (Europe), 2.4 GHz (Global).
Since the physical layers of these three bands are not the same, their respective channel bandwidths are also different, namely 0.6 MHz, 2 MHz and 5 MHz. There are 1, 10 and 16 channels respectively. The three bands have different spread spectrum and modulation methods. Spread spectrum uses direct sequence spread spectrum (DSSS), but the bit-to-chip transitions vary widely. The modulation method uses phase modulation technology, but the 868MHz and 915MHz bands use BPSK, while the 2.4GHz band uses OQPSK.
With a transmit power of 0 dBm, Bluetooth typically has a range of 10 meters. While ZigBee can usually reach a working distance of 30-50 meters indoors, it can even reach 400 meters in outdoor open space (TICC2530 without power amplification).
Therefore, ZigBee can be classified as a low-rate short-range wireless communication technology.
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