Research And Application Of Wireless Sensor Network In Xinjiang Coal Field

Wireless Sensor Network has extensive application prospect in national security and national economy. But Environment Monitoring of a large area is an important domain in Wireless Sensor Network application. Adopting Wireless Sensor Network technology in the fire monitoring system of Xinjiang coal field, it is taking the initial step from laboratory research to the practical application of large-scale gradually. In the process, remote data transmission from monitoring site to the control center and effective communication between sensor nodes are important links in practical application.The Mobile network transmission scheme are determined after analyzing data transmission mode. This dissertation analyzed the system structure of Wireless Sensor Network which takes AVR ATmega128L,CC2400,temperature and humidity sensor ( SHT10 ) and GPRS module as the components. Through programming the microprocessor, activating mode of GPRS by mobile phone short message to realize remote data transmission by double modes (mode of GPRS and mode of GSM) of wireless sensor and to accomplish complementary mutual function of two modes, reliability and stability of remote data transmission are enhanced. The system was tested in real conditions for fire monitoring in Xinjiang coal fields. The results indicated that this system can realize accurate and real time remote data transmission by Wireless Sensor Networks. Antennas which influenced network performance are improved to ensure the effective communication in Wireless Sensor Network. Wireless Sensor Network node usually used monopole antenna and patch antennas, which can achieve the gain of 1-2dB and nominal communication distance is 100-200 meters. Xinjiang coal fields have requirements for the space sampling frequency of 30 meters, also requested the node buried and antenna concealed. If the node is buried, communication distance dramatically reduced to 5 meters as absorption of electromagnetic wave by earth surface; On the other hand, GPRS module usually used monopole antenna and microstrip antenna, which can achieve the gain of 2-3dB.But the base station antenna can achieve the gain of 10 dB. A variation in the gain cause the arrangement of nodes is limited. Antennas of general node and GPRS module are improved in this paper. Stub loaded helix (SLH) antennas suitable for 2.4 GHz and GSM1800 MHz is developed. The antenna of general node operates at 2.45 GHz with a return loss of -32.86 dB and a bandwidth of 160 MHz, which can achieve the maximum gain of 11.174 dB; The antenna of GPRS module operates at 1.72 GHz with a return loss of -39.9 dB and a bandwidth of 240 MHz, which can achieve the maximum gain of 11.853 dB. The gain of GPRS antenna is close to the gain of the base station antenna, so communication distance of them can equal each other. Further, the SLH antenna enhanced the Remote extension capability. The measurement results show that without increasing the transmission power the communication distance from general node to convergent node can increase by 10 times and the communication distance from convergent node to the base station can increase by 5 times.SLH antenna enhanced the coverage ability and reliability, then lay a good basis for the monitoring of a large area in Wireless Sensor Network application.