附（外文文献原文）：
Research of Wireless Sensor Networks based on ZigBee for Miner Position
Xiuping Zhang, Guangjie Han, Changping Zhu, Yan Dou, Jianfeng Tao College of Computer & Information Engineering, Hohai Univ. Changzhou, China
E-mail:zhangxiup@hhuc.edu.cn Zhucp315@126.com Abstract—With the rapid development of computer communication and web technology, especially the widely application of wireless sensor and embedded technology, Wireless Sensor Networks (WSNs) have been paid great attention in industry field and our daily life. WSNs based on ARM7TDMI-S CPU and ZigBee device has merit of rapid and simple in networking, node movable in application, abundant information in acquisition, real time collaboration in communication, low power consumption in continuous operation, so it is very suitable for targeting miner’s position underground. In this paper, networking scheme of the WSN is presented, and distributed information processing, communication technology and real time collaboration are focused on. Miner’sinformation in mobile is obtained accurately by sensor. After that position information is transmitted reliably to monitoring center. Test result in continuous operation shows there is no information loss or undetected. Therefore this scheme is stable and effective,which will play a positive role for security in coal mine by right of characteristics of Zigbee WSNs in my opinion. Keywords- ZigBee; ARM7TDMI-S; CC2420; WSNs; Miner positionning
I. INTRODUCTION
Wireless Sensor Networks (WSNs) is a large scale, wireless, self-organization network. It is integration of computer communication, web technology, embedded MCU and wireless sensor technology which has the ability to sense and communicate [1]. Nodes are of low cost, small size. Most of which can spread in the work region, collect data, process data and communicate. Wireless sensor nodes usually work at Radio Frequency (RF) band. Nodes constitute a tiered architecture networks on site
data monitoring. It is usually applied in industry, agriculture, telemedicine and environmental monitoring. We all know that coal production is in the threat of complex working conditions, such as poisonous gas, pervious, collapse, apical plate, etc [2]. Once accident occurs, it would endanger the lives of miners. Therefore it is urgent for the ground staff to make clear the miners’ exact location so as to take measures I time. The founding of a Wireless Sensor Network for miner position monitoring has great application value in mine. II. SCHEME SELECTION
Main technical specification requirements of miner position monitoring system are summarized as follows:(1) Position precision is 10 meters. Coal mine roadway is narrow, crooked and complicated, so safety monitoring system needs to capture more o
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monitoring points, (2) Low data rate. The amount of data to be transmitted is small, however high reliability of data transmission is required, (3) Low power consumption. Relatively large power supply is not allowed underground in fact, (4) Low cost of the monitoring system device is required [3].Comparison of several wireless transport modes is shown in Table 1.ZigBee technology is low protocol complexity, low power consumption, low data rate, low cost, wireless communication technology, which adopts IEEE 802.15.4 protocol. It can be embedded in devices, and has the function of geography position. It works at the data rate of 250 kbps. The range of each node is normally between 10~100m. The range can be up to 1~3km by increasing the RF emission power. It can respond rapidly. It takes only 15ms from sleep state to work state and 30ms to access network. It defined three network topologies including star topology, cluster topology and mesh topology. Nodes are as many as 65000, which can organize high capacity data transmission network platform. Three-tier security mode is used to determine its security attribute flexibly. Free patent agreement, license free band. ZigBee works at the 2.4GHz ISM band, using Direct Sequence Spread Spectrum ( SSS) modulation [4]
TABLE I. COMPARISION OF WIRELESS
TRANSPORT MODES cost Battery lifetime Effective range(m) Baud rate protocol 20/40/ 250Kbps IEEE 802.15.4 1M~3M bps IEEE 802.15.1 40M~ 60Mbps IEEE 802.14.3 5.5/11 Mbps IEEE 802.11 b Assigned band 868M/915M /2.4GHz 2.4 GHz
Considered the above factors, WSNs with ZigBee technology can suit the long-term coal miner position monitoring at low cost, low data rate, low power consumption, high reliability, so this scheme is adopted in coalminer position system. During the process of design, the network structure is determined first, then device is selected and related circuit is designed for networking, including wireless receiver module applying Mega128 and CC2420, substation module applying LPC2114, etc. Communication protocols and related software have been designed and debugged finally.
III. WIRELESS SENSOR NETWORKS DESIGN
System function: (1) Achieving underground miner positioning, having their location improve efficiency of rescue at the time of accident, (2) Managing the time and frequency that miner come into or go out of coalmine, getting miner’s dynamic
3.1G~ 10.6GHz 2.4 GHz 10~75 10 30 100 ZigBee Lowest years Blue Tooth UWB Lower days Highest hours Wi-Fi Higher days
position information, so as to improve management performance, (3) Tracing back historical data, statistics and analysis for decision-making.
A. WSNs structure and hardware device design
Mixed topology is implemented in our design. At present relatively large power supply is not allowed in ine. Star topology network is relatively easy to control and synchronize with low power consume, therefore it is applied in the first layer. Bus topology is applied in the second layer, because data waveform transmitted has less distortion in this way. The ZigBee wireless sensor network designed for coal miner positioning has four sections:
1) Monitoring and managing software platform (master node): taking charge of collecting personnel position information from network, tracing back data, statistics and analysis, and displaying results in theform of graphic. 2) Monitoring substations: which are full function device nodes, responsible for receiving information of mobile nodes from wireless receiver and outputting data to the master node for processing.
3) Wireless receivers (wireless sensor nodes): which are responsible for detecting information from miners’ within the working area and sending it to substation in accordance with communication protocols.
4) Wireless code emitter: which are reduced function device nodes, which can be easily fixed in miner’s lamp box, helmet, belt, or pocket. Code emitter sends out radio frequency signals which carry miners’identity information. When miner in mobile is in theworking area of wireless receiver, his information will be received by receiver and be transferred up to substation [5].
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