Design Of Node Seismograph Data Transmission System Based On WLAN

The micro-seismic monitoring technology is an important technique in the field of low-permeability oil and gas exploration in recent years.Through monitoring the process of oil and gas production and such petroleum engineering as hydraulic pressure and air injection,the micro-seismic monitoring provides guidance for oil fracturing and subsequent development of oil fields.Therefore,it is of great significance to recover the data of micro-seismic monitoring in real time.The node seismograph could meet the seismic prospecting in complicated landforms,so it could be applied widely in the field of micro-seismic monitoring.But,the lack of real-time monitoring of field data limits its further application in the micro-seismic monitoring.In the view of the lack of communication ability of node seismograph developed by Jilin University,the thesis presents a data real-time recovery system based on 5GHz WLAN by combining the communication distance,speed and other aspects of the existing mature wireless communication technology with the demand of micro-seismic monitoring.Through the analysis of the different network topology in the existing wireless local area network,the combination of extended service set topology and relay network topology is used to realize the real-time transmission of long-distance and multi-node data.The realization of data transmission system based on 5GHz WLAN includes two parts: hardware circuit design and software development.In the design of the hardware circuit,the paper mainly completes the design of seismic data storage unit based on STM32F207,Ethernet transmission unit and wireless transmission unit based on AR7161.On the basis of hardware system above,the development of data transmission program based on embedded Free RTOS and the data transmission software based on Visual Studio 2010 + Qt development environment is completed,including the interaction module between the host computer and the seismograph and improvement on multi-node transmission mechanism.The design of functional modules of the host computer software includes connection monitoring,parameter setting,status information query,and file transmission based on FTP.In the micro-seismic monitoring,channel congestion and multi-rate transmission limit the throughput of the entire transmission system.Combining the mechanism of multi-node contention shared channel based on CSMA/CA with polling mechanism based on PCF,the data transmission system achieve multi-node data transmission,considering the influence of multi-rate transmission.Finally,the performance of the data transmission system is test,including hardware system test,software functional test,speed and distance test,optimal throughput test,multi-rate transmission test and the overall system test.The test results show that data transmission system designed in this paper can realize the command interaction and data recovery of ninety node seismographs in the range of 1km and the throughput of the whole system could reach 7.29MB/s,which achieves the desired objective and could satisfies the real-time monitoring of the micro-seismic activity.