Research On OFDM Technology Applied To The Wire Line High-speed Telemetry

Using OFDM technology to further improve the transmission rate of well logging telemetry system is the consensus of the industry.At present,the rise of network-well-logging concept is to promote the development of OFDM technology applied to well logging cable telemetry system.This article aims to obtain the technical architecture based on OFDM technology applied to wire line telemetry system Also,we analysis the key factors of the architecture in detail.Wire line is the key factor which severely limits the transmission rate performance in telemetry system.This article started the research on logging telemetry system from the analog signal path,also analyzed the transmission characteristics of the well logging cable under the T5 model and the amplitude-frequency characteristics of the transformer connected at both ends of the cable.We make those into a sub-module of the numerical simulation platform by digitizing the analog signal transmission channel.Based on the platform,we proposed technical architecture based on OFDM technology in wire line telemetry and the crucial task module.Logging cable OFDM modulation system is a double module,it could divided into the frequency domain modulation and time domain modulation In the frequency domain modulation module,This paper studied the data stream of pseudo-random,error correction coding and packet interleaving task.And we studied how to use the IFFT algorithm to make the frequency domain data stream into the time domain data stream.In the time domain modem module,synchronization is the most important task.This paper analyzed the interaction symbol synchronization with the sampling clock synchronization relations.This paper presented a method applied to well logging cable telemetry system of symbol synchronization error & sampling frequency offset joint estimation of synchronization scheme and did the numerical simulation in mat lab.For the well logging cable channel on the OFDM time-domain waveform severely tailing phenomenon,the article used the MMSE thought to design the Wiener filter to shorten the cable channel tail successfully.Finally,in order to make OFDM wire line telemetry system achieve the pre-transfer rates designed,this paper studied the water-filling algorithm,the results of numerical simulations show that the bit allocation reached the system design requirements.In the end,by a numerical calculation of the OFDM wire line telemetry system simulation study,this article got some thoughts and information for developers' reference on the process of device selection and functional modules.