Shijiazhuang Yibang Technology Co., Ltd.:
Zigbee technology introduction:
(1) zigbee Introduction: ZigBee is a short-range, low complexity, low power, low data rate, low-cost two-way wireless communication technology, a complete protocol stack is only 32KB, can be embedded in a variety of devices, while supporting geography GPS. These characteristics determine that ZigBee technology is very suitable for application in wireless sensor networks. Compared with various existing wireless communication technologies, ZigBee technology is relatively low in power consumption and cost, and has great advantages. The mine personnel positioning and gas wireless monitoring system designed and researched in this paper is a wireless sensor network based on ZigBee technology for real-time positioning of downhole personnel and monitoring of gas concentration in mine air to achieve system reliability, ease of installation, and low cost , energy saving and practical feasibility, which will provide certain guarantees for the smooth progress of coal mine production work, and play a role in mine disaster prevention, disaster reduction, and improvement of production efficiency.
(2) zigbee technical features:
ç›´ Physical layer RF communication link direct sequence spread spectrum adopts high processing gain; clear channel detection; detection of interference energy; frequency-hopping technology; frequency agility;
åè®® The protocol is based on CRC error detection/correction; a collision avoidance strategy CSMA/CA is adopted; a dedicated guaranteed time slot is reserved for the fixed bandwidth communication service; the transmitted data packets are to be confirmed by the receiving party. Retransmit if there is a problem; keep packet data freshness;
Zi The communication reliability mechanism zigbee uses the collision avoidance mechanism of CSMA-CA, and at the same time reserves dedicated time slots for communication services that require fixed bandwidth, avoiding competition and collisions when sending data; clear channel detection; MAC layer adopts complete For the confirmed data transmission mechanism, each sent data packet must wait for the recipient's confirmation message.
â—‡ Self-organizing and self-healing ability of network: zigbee's self-organizing function: Without human intervention, network nodes can perceive the presence of other nodes, and determine the connection relationship, forming a structured network; zigbee self-healing function: add or delete a node The node location changes, node failure, etc., the network can repair itself, and the network topology is adjusted accordingly, without manual intervention to ensure that the entire system can still work properly.
(3) zigbee's technical advantages:
æ•°æ® Low data transmission rate: 10KB/sec~250KB/sec, focusing on low-transmission applications 功耗 Low power consumption: In the low-power standby mode, two regular AA batteries can be used for 6~24 months;
æˆæœ¬ Low cost: ZigBee data transmission rate is low, the protocol is simple, so the cost is greatly reduced;
â—‡ Large network capacity: The network can accommodate 65,000 devices;
æ—¶ Short delay: 30 ms for typical search equipment, 15 ms for sleep activation, and 15 ms for active equipment.
â—‡ Network self-organizing, self-healing ability and reliable communication;
æ•°æ® Data Security: ZigBee provides data integrity checking and authentication capabilities. It uses AES-128 encryption algorithm (US new encryption algorithm, which is currently one of the best text encryption algorithms). Each application can flexibly determine its security properties. Flexible frequency band: Use frequency bands of 2.4GHz, 868MHz (Europe) and 915MHz (United States), all of which are license-free (free)
(4) Zigbee network equipment:
â—‡ Network Coordinator: Contains all network messages and is the most complex of the three device types, with the largest storage capacity and the highest computing power. Send network beacons, establish a network, manage network nodes, store network node information, find routing messages between a pair of nodes, and continuously receive information.
â—‡ Full-featured device (FFD): Can act as a network coordinator, form a network, connect other FFDs or Reduced Function Devices (RFDs), and FFDs have the function of a controller to provide bidirectional transmission of information. All of the 802.15.4 features and all the features specified by the standard are attached with more memory and computing power to make it function as a network router when idle. Can also be used as a terminal device ç²¾ Reduced Function Device (RFD): The RFD can only send information to or receive information from the FFD. Including limited functionality to control cost and complexity is commonly used as a terminal device in the network. The relatively simple implementation of ZigBee naturally saves money. RFD reduces the cost of ZigBee components by eliminating memory and other circuitry, while a simple 8-bit processor and a small protocol stack also help reduce costs.
An Introduction:
(1) General introduction: This system is composed of multiple self-powered ZigBee nodes. Each ZigBee node can collect and calculate the surrounding environment data, perform simple calculations, communicate with other nodes and the outside world, and thus make numerous sensors available. The zigbee handheld terminal can work together to communicate with high quality and form a fault-tolerant acquisition system. this system