Research Of Data Transmission And Encoding Technology For Seismic Exploration Data Acquisition System

With the rapid development of economy,the global supply of energy resource is very short.The struggle for energy resource is increasingly intensive in the world.To find more useful oil resource,advanced exploration instrument is required.Seismograph also becomes necessary in oil exploration.With the increase of exploration depth,there are higher requirements for the resolution and the capability of carrying channels of seismograph.The increase of the performance depends on,the performance of the acquisition station on one hand,and more important,increasing the data transmission rate of the seismograph on the other hand.The technology of data transmission with high data rate and reliability is very critical in order to achieve seismic data acquisition with large scale and high accuracy.The present article focuses on the research of technology of data transmission of telemetering digital seismograph.Start from the point of view of network communication,analyze the basic structure of digital seismograph network,and establish the model of protocol stack of seismic data transmission system.It focuses on the analysis of the communication style among basic functional units on the line in seismograph network.Considering the specific requirements of data transmission of each device unit,adjust and assign the functions of protocol stack.Analyze the physical layer and data link layer protocol of the line.In physical layer,the protocol LVDS is applied to the line data transmission interface of seismograph.The advantages of small swing amplitude,low power consumption,strong anti-interference capability and low costs of LVDS signal are utilized.In present research,FPGA chipsets are utilized to construct the circuits;the programs are written for encoding and decoding in data transmission;the issue of synchronization is resolved.Since FPGA has the features of high speed and parallel execution,the core chipset is capable of performing receiving data,data acquisition and sending data simultaneously.An acquisition link is built,including acquisition stations and power stations.The performance of data transmission of Big-Line is verified.Apply SOPC to the design of power station,embed Nios? soft core processor,transplant the operation systems of LWIP and MicroC/OS-I,and realize the diver of network chipset and TCP/IP.The external storage acts as program storage and large volume data storage.In current data transmission system,CRC is mainly used as channel coding method.The shortage of CRC is that it can only detect errors and is weak of correcting errors.It can improve this by using forward correction error channel encoding.The convolutional code has an excellent performance of correcting random errors and interleaving can deal with errors in a burst.The present article gives 4 methods of realizing convolutional encoder,set up a simulation communication system,add Gaussian channel,and compare the anti-interference performance of error correction encoding methods.Finally the optimal method is recommended.