| At present coal mine accidents, in which the mine safety issues into the public spotlight. Due to underground mining, coal seam gas released due to lack of timely and other flammable gases discharged, and the coal seam deep from the surface normal in the event of accidents such as gas explosion, very could easily lead to mine casualties. Be able to track the location in the shortest time to save the mine staff personnel vital for life. At present, the main GPS satellite positioning to track positioning, mobile communications to track location, zigbee track positioning technology.ZigBee technology uses IEEE 802.15.4 protocol standards. Because of this public free of charge based on the 2.4 GHz frequency band for signal transmission without network usage fees. ZigBee chip prices have dropped below 3 U.S. dollars, therefore, compared the price of mobile terminal equipment. Build networks with zigBee have greater cost advantages.In this paper, advantages and disadvantages of more traditional positioning systems that zigbee-based wireless location system for its advanced technology, easy to implement, cost-low cost, easy-to-universal characteristics, will become the future trend of development. ZigBee technology has an agreement simple, low cost, power consumption, easy networking, etc., most suitable for downhole positioning system.By in-depth study of the ZigBee technology, the basic principle of in-depth analysis of the physical layer, media access control layer, network layer, application layer protocol layers. Underground staff on the positioning system simulation, the various parts of the functions in the system and the main hardware selection was determined to study a variety of wireless network positioning algorithm, a practical location methods.Because of the location positioning system zigbee nodes are generally rely on their own portable battery-powered, take up as much as possible a long life, so how to reduce the energy consumption of the communication process seems very important. Reduce energy consumption and extend battery survival time related to different levels of ZigBee protocol and algorithm complexity, this article analysis of the physical layer, media access control layer, network layer of the questions and APIT algorithm has been improved to reduce the algorithm complexity and coupling and positioning accuracy within an acceptable range. In this paper, various existing energy-saving technologies applied in this system the possibility of in-depth study found that:the physical layer network nodes based on location to determine RSSI/LQI values adjust the size of transmission power. In the MAC layer to support node to switch between different states to improve energy efficiency. Zigbee-based tracking and positioning system for underground workers in the network layer energy-saving mechanism must take into account both communication energy consumption, but also must take into account the coupling degree of the system to prevent certain parts of the absence of Er Shi positioning node failure. In an underground mine if there is an incident, it may result in a large number of nodes in communication interrupt, so the coupling is more demanding requirements.Finally, sum up the text, and proposed future direction of work... |
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