CN103297372B - A kind of downhole data high speed radio transmission system and reduction Peak-to-Average Power Ratio method thereof - Google Patents
A kind of downhole data high speed radio transmission system and reduction Peak-to-Average Power Ratio method thereof Download PDFInfo
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Abstract
The invention discloses a kind of downhole data high speed radio transmission system and reduce Peak-to-Average Power Ratio method. This invention first proposed downhole data high-speed transfer ofdm system, and the transfer rate of existing downhole transmitted mode is brought up to a megabit level, it is achieved that downhole data real time high-speed transmits, and provides new thinking for China's downhole data transmission technology. Simultaneously because this system has higher PAPR value, when signal higher for PAPR is through these non-linear components, signal can produce non-linear distortion, can have a strong impact on systematic function; Therefore, it is proposed to a kind of SLM method of improvement, eliminate the independent transmission of side information, save downhole transmitted channel width. The present invention realizes easily, can be used in all kinds of employing OFDM communication system being modulated.
Description
Technical field
The invention belongs to Oil/gas Well downhole data high-speed transfer field, relate to based on OFDM (OrthogonalFrequencyDivisionMultiplexing, OFDM) the downhole data high speed radio transmission system of modulation technique, and signal high peak-to-average power ratio Peak-to-AveragePowerRatio, PAPR in this system) problem. More particularly it relates to an downhole data high speed radio transmission system and reduction Peak-to-Average Power Ratio method thereof.
Background technology
Down-hole information effectively extract with signal transmission rate problem govern always Oil/gas Well exploitation new technique development. Particularly measurement while drilling, well logging during and geosteering have become indispensable technology in horizontal well, extended reach well and directional well construction, but at present, China is also in the stage of Introduced From Abroad drilling measuring technology. Wherein, downhole data transmission technology is to restrict the Main Bottleneck of its development. Conventional downhole data transmission mode is mud-pulse transmission means, this mode has positive pulse, negative pulse, continuous wave pulse three kinds, and positive and negative pulse transmission means is all because transmission data speed is slow, corrosion failure is relatively strong, power consumption is replaced by continuous wave transmission means greatly and gradually. But, continuous wave slurry pulse generator only has Schumlburger company to have the instrument that this Technical comparing is ripe at present, and efficiency of transmission also only increases to 5��10bit/s simultaneously, and noise jamming impact is relatively larger.
Along with country's attention to petroleum-based energy, the application in well logging during of electronic technology and communication technology is increasingly extensive. The defect low for prior art transfer rate and down-hole gather data sharp increase needs high-speed transfer to arrive the current situation of well head, China's development downhole data transmission technology to have new thinking, realize great-leap-forward development, could be consistent with the developing steps of World Oil Industry advanced technology, reach to improve the purpose of domestic well logging during high-speed transfer. So that its high data rate, high spectrum utilization, good Effect of Carrier Frequency Offset, power system capacity be big etc., feature is adopted OFDM technology by forth generation mobile communication system. At present, OFDM is applied to the domestic existing research of wire transmission and the application of downhole cable, such as middle oil well logging company limited EILog High-performance Well Logging System, adopt COFDM (COFDM) technology, OFDM technology is applied to well logging field, and transmission speed reaches 430kbit/s. CNPC's Great Wall probing LEAP800 logging system is being analyzed on the basis of seven core logging cable transmission characteristics, practical situation in conjunction with well logging, it is developed based on million grades of high speed logging remote transmission systems of orthogonal frequency division multiplexi, system has two-way communications capabilities, the message transmission rate of up 1000kbit/s, descending 50kbit/s can be provided, and there is the features such as the time of foundation short, stable and reliable in work, the different logging cables of self adaptation. Owing to cable transmission mode exists the deficiency such as connection reliability difference, structure complexity, the focus of research has been become in recent years based on the downhole transmitted system of OFDM modulation system, article " Wang Qiang; Li Cheng; Ding Tianhuai. the OFDM modulation method of the drill string sound transmission realizes [J]. electromechanical engineering; 2012,29 (4): 373-376 " propose the pipe nipple drilling rod sound transmission scheme based on OFDM modulation system and can realize the transfer rate of 160bit/s, the research that the program is follow-up provides direction.
Current down-hole OFDM transmission system exists, but, downhole wireless OFDM transmission system does not still have. And wireless relatively wired, it is possible to the deficiency such as overcome that the connection based on OFDM cable communication system is unreliable and structure is complicated. So, study and to propose a kind of down-hole OFDM high speed transmission system technology significant.
Simultaneously, form owing to ofdm signal shows as multiple orthogonal sub-carriers Signal averaging in time domain, its signal has high PAPR, and the power amplifier in downhole transmitted system is much nonlinear, its dynamic range is also very limited, when data signal higher for PAPR is through these non-linear components, signal can produce non-linear distortion, and harmonic wave produced by non-linear distortion can have a strong impact on systematic function. But the power device of large dynamic range, it is meant that the equipment cost of transmitter is higher. It is thus desirable to find the method reducing signal PAPR. Have already been proposed a lot of method reducing peak-to-average power ratio, including amplitude limit class technology, coding class technology and probability class technology. Owing to amplitude limit class technology adopts non-linear process, signal distortion can be brought; Coding class technology encoding and decoding complexity is very big. Wherein, Choose for user method (SelectiveMapping, SLM) method can reduce PAPR without distortions, but owing to the method need to produce multiple transmission sequence representing identical information, from multiple different random phasic serial signal vector dot products, carry out repeatedly IFFT computing again, it is necessary to multiple IFFT modules, this considerably increases the complexity of the amount of calculation of system and hardware;It addition, receiving terminal recovers former data message needs multiple random vectors of the fully known transmitting terminal of receiving terminal, namely multiple random vectors also to be sent as side information, and these side informations are exactly the redundancy of SLM method, and it sacrifices part and sends bandwidth.
Summary of the invention
It is an object of the invention to overcome the problems referred to above of high speed data transfer system and reduction Peak-to-Average Power Ratio method thereof under existing well, it is provided that a kind of downhole data high speed radio transmission system and reduction Peak-to-Average Power Ratio method thereof. The data of downhole sensor collection are carried out OFDM modulation by this system, and adopt the SLM method of improvement to reduce the high PAPR of system signal, and the wireless bridge that modulation signal is built along drill string in the form of an electromagnetic wave is transferred to aboveground and recovers; Data transmission bauds is increased to the speed of megabit level by this invention, exceeds well over the speed of data transmission technology under existing well, can better realize the real time high-speed transmission of downhole data the problem solving system signal height PAPR better.
For achieving the above object, the technical solution used in the present invention is as follows:
A kind of downhole data high speed radio transmission system and reduction Peak-to-Average Power Ratio method thereof, it is characterised in that: it is made up of down-hole acquisition module, ofdm signal transport module and aboveground receiver module; Described down-hole acquisition module includes sensor assembly and analog-digital converter module, the position being arranged on drill bit below square drill collar; Described ofdm signal transport module includes down-hole OFDM manipulator, ofdm signal transmission pipe nipple is constituted; Described aboveground receiver module includes: ofdm demodulator, digital to analog converter module and signal recover module; Described ofdm signal transmission pipe nipple includes ofdm demodulator, wireless repeater and OFDM manipulator; Described OFDM manipulator includes coding mapping module, serial/parallel module, weak energy supposition training sequence module, IFFT module, parallel/serial module, protection interval module, D/A converter module, rf modulations module; Described ofdm demodulator structure includes: radio demodulating, analog-to-digital conversion module, synchronization channel estimation module, training sequence module, deprotection interval module, serial/parallel module, FFT module, parallel/serial module, decoding De-mapping module;
Described signals collecting, transmitting, transmission and reception process are as follows: first sensor assembly is by waveshape signals such as the downhole temperature collected, pressure, becomes bit stream by analog-digital converter module; Its signal is transferred to the OFDM manipulator being arranged on nearly drill bit place along drill string, and bit stream is modulated into ofdm signal; Ofdm signal after process is transferred to the ofdm signal transmission pipe nipple at 50 meters of with electromagnetic wave along drill string, and in drill string, every 50 meter amperes fill an ofdm signal transmission pipe nipple; Signal is transferred to along drill string in the ofdm demodulator of aboveground receiver module always and is demodulated, and by the digital-to-analogue conversion again of the signal of demodulation, recovers and be transferred to terminal to process.
In described ofdm signal transmission pipe nipple: ofdm signal first passes through ofdm demodulator and is demodulated to digital signal; Amplify signal again through wireless repeater, compensate the decay of signal along drill string transmitting procedure; Become ofdm signal finally by OFDM modulators modulate, and transmit pipe nipple transmission to the next one.
Described reduction Peak-to-Average Power Ratio method is applied on each OFDM manipulator, specifically comprises the following steps that
First the digital signal received is carried out serioparallel exchange and obtains parallel signal sequences X by step 1:OFDM manipulatorn=[X1,X2,��XN], n represents the number of signal sequence, n=1,2 ..., N;
Step 2: each signal sequence X in parallel signal sequencesn, it is multiplied with Hadamard matrix H and obtains signal X 'n;
Step 3: again by the front U row vector H of Hadamard matrixuAs phase sequence, according to Superposition FormulaSuperposition logging signal X ' after treatmentnObtain signal, wherein u represents the number of phase sequence, u=1,2 ..., U, �� is power allocation factor, 0 < �� < 0.1;
Step 4: signalAgain with phase sequence HuCorrespondence is multiplied and obtains the more options signal sequence of an original logging signal
Step 5: from the more options signal sequence of gainedMiddle selection has the signal sequence of minimum PAPR valueSend;
Step 6: first the ofdm demodulator at aboveground receiver module recovers phase sequence H by channel estimation methodsu, then adopt inverse process demodulation to recover original down-hole digital signal.
The beneficial effects of the present invention is: the problem that the invention solves the low transmission rate existed in current downhole data high speed transmission system, message transmission rate can be brought up to a megabit level, and the intersymbol interference that down-hole multipath channel brings can be overcome, provide new approaches for China's downhole data high-speed transfer. The SLM method of improving simultaneously utilizing Hadamard and weak energy supposition training sequence method reduces the defect of the high PAPR that system is brought; Further, since be weak energy supposition, receiver is without separating overlying training sequence, it is also possible to undertaken synchronizing by training sequence module, channel estimating, thus improving systematic function.
Accompanying drawing explanation
Fig. 1 is a kind of downhole data high speed radio transmission ofdm system block diagram, mainly includes down-hole acquisition module, ofdm signal transport module and aboveground receiver module and constitutes; Described down-hole acquisition module includes sensor assembly and analog-digital converter module; Described ofdm signal transport module includes down-hole OFDM manipulator, ofdm signal transmission pipe nipple is constituted; Described aboveground receiver module includes: ofdm demodulator, digital to analog converter module and signal recover module; Transmission channel is drill string and the ofdm signal being connected to drill string different parts transmission pipe nipple;
Fig. 2 is the structured flowchart of an ofdm signal transmission pipe nipple, includes successively: ofdm demodulator, wireless repeater, OFDM manipulator;
Fig. 3 is an OFDM modulator principle block diagram, including coding mapping module, serial/parallel module, weak energy supposition training sequence module, IFFT module, parallel/serial module, protection interval module, D/A converter module, rf modulations module;
Fig. 4 is an ofdm demodulator theory diagram, including radio demodulating, analog-to-digital conversion module, synchronization channel estimation module, training sequence module, deprotection interval module, serial/parallel module, FFT module, parallel/serial module, decoding De-mapping module;
Fig. 5 is the main process schematic that realizes improving SLM method, is overlying training sequence algorithm block diagram in broken box;
Fig. 6 is the PAPR simulation curve figure of overlying training sequence method in improved method, " original " represents the PAPR of primary signal, " SLM traditional method " represents the PAPR adopting SLM traditional method signal, " overlying training sequence method " represents the PAPR of the SLM method signal adopting overlying training sequence method, abscissa represents the threshold value of PAPR, vertical coordinate represents that PAPR exceedes the probability of a certain threshold value, i.e. complementary accumulated probability distribution function (CCDF);
Fig. 7 is the PAPR simulation curve figure improving SLM embodiment of the method, " original " represents the PAPR of primary signal, " SLM traditional method " represents the PAPR adopting SLM traditional method signal, " improve SLM method " and represent the PAPR improving SLM method signal adopting the present invention to propose, phase sequence number u=128, abscissa represents the threshold value of PAPR, and vertical coordinate represents that PAPR exceedes the probability of a certain threshold value, i.e. complementary accumulated probability distribution function (CCDF);
Fig. 8 improves SLM method PAPR simulation curve figure of embodiment when the phase sequence of varying number, " original " represents the PAPR of primary signal, " improve SLM method " and represent the PAPR improving SLM method signal adopting the present invention to propose, u represents the number of phase sequence, taking 2,4,8,16 respectively, namely original method is u=1; Abscissa represents the threshold value of PAPR, and vertical coordinate represents that PAPR exceedes the probability of a certain threshold value, i.e. complementary accumulated probability distribution function (CCDF).
Detailed description of the invention
Below in conjunction with accompanying drawing, main principle, the detailed description of the invention etc. of realizing of technical scheme is described in detail.
Downhole data high-speed transfer ofdm system operation principle of the present invention is as follows: the sensor of down-hole, by waveshape signals such as the downhole temperature collected, pressure, becomes bit stream by analog-digital converter; Signal is transferred to the OFDM manipulator being arranged on nearly drill bit place along drill string, and bit stream is modulated into ofdm signal, reduces this signal peak-to-average ratio simultaneously; Ofdm signal after process is transferred to the ofdm signal transmission pipe nipple at 50 meters of with electromagnetic wave along drill string, and in drill string, every 50 meter amperes fill an ofdm signal transmission pipe nipple; Signal is transferred to ground ofdm demodulator along drill string always and is demodulated, and recovers the signal of demodulation and be transferred to terminal to process.
Refer to Fig. 1, this figure is a kind of downhole data high speed radio transmission ofdm system theory diagram, after the downhole data that the various sensor in down-hole obtains is modulated into ofdm signal, it is transferred to uphole equipment in the form of an electromagnetic wave along drill string, and teletransmission is to control centre, wherein in order to compensate the decay of signal in transmitting procedure, in drill string, every 50 meter amperes fill an ofdm signal transmission pipe nipple. Refer to Fig. 2, this figure is the structured flowchart of an ofdm signal transmission pipe nipple, includes successively: ofdm demodulator, wireless repeater, OFDM manipulator; Ofdm signal first passes through ofdm demodulator and is demodulated to digital signal; Amplify signal again through wireless repeater, compensate the decay of signal along drill string transmitting procedure; Become ofdm signal finally by OFDM modulators modulate, and transmit pipe nipple transmission to the next one; Filling an ofdm signal transmission pipe nipple every 50 meter amperes in drill string, it is attached to the different parts of drill string and goes into the well in company with drill string, carries out real-time data transmission.
The downhole data information of sensor acquisition is become bit stream by analog-digital converter conversion (ADC), for OFDM manipulator, refer to Fig. 3, its operation principle is: bit stream first pass around chnnel coding with reduce due to channel effect produce in error probability; Secondly, bit stream is mapped on symbol, and the mode of employing is BPSK or QPSK. Symbol stream forms parallel form data stream by serioparallel exchange, forms serial data stream format then through parallel-serial conversion after IFFT, produces protection interval between OFDM symbol, and this protection interval is to be obtained by the cyclic extensions of OFDM symbol. Analogue signal is converted digital signals into, then through rf modulations then through digital-to-analogue conversion (DAC). Using antenna modulation signal to transmit along drill string, refer to Fig. 4, ofdm demodulator does the process that OFDM manipulator is contrary, modulates signals into into digital signal.
Refer to Fig. 5, the figure shows the improvement SLM procedure reducing system signal height PAPR, specifically comprise the following steps that
Step 1: each sensor in down-hole by cable by the down-hole digital data transmission that collects to the signal input part of OFDM manipulator, first the digital signal received is carried out serioparallel exchange and obtains parallel signal sequences X by manipulatorn=[X1,X2,��XN], n represents the number of signal sequence, n=1,2 ..., N;
Step 2: each signal sequence X in parallel signaln, it is multiplied with Hadamard matrix H and obtains signal X 'n;
Step 3: again by the front U row vector H of Hadamard matrixu, u represents the number of phase sequence, u=1,2 ..., U is as phase sequence, according to Superposition FormulaSuperposition logging signal X ' after treatmentnObtain signal;
Step 4: signalAgain with phase sequence HuCorrespondence is multiplied and obtains the more options signal sequence of an original logging signal
Step 5: from the more options signal sequence of gainedMiddle selection has the signal sequence of minimum PAPR valueSend; First phase sequence H is recovered by channel estimation methods at aboveground receiving terminalu, then adopt inverse process demodulation to recover original down-hole digital signal.
Described Hadamard matrix H is the orthogonal square formation being made up of+1 and-1 element. Build this Matrix Formula as follows:
Wherein, the dotted box portion of Fig. 3 embodies the concrete schematic diagram adopting overlying training sequence method, carries out phase sequence and signal sequence Superposition Formula according to power allocation factor ��:
Wherein 0�ܦ¡�1.
Refer to Fig. 5 the main of SLM method utilizing Hadamard matrix proposed according to the present invention and realize principle flow chart. The downhole data high-speed transfer ofdm system platform put up on its basis does the performance of one group of embodiment emulation method to verify the present invention and propose. Embodiment algorithm simulating parameter is:
�� channel is Gaussian channel
The each ofdm signal of �� comprises 128 subcarriers
�� ofdm signal number 1000
�� adopts BSPK modulator approach
Fig. 6 is the PAPR simulation curve of weak energy supposition training sequence method, by the contrast of this curve, can draw when weak energy supposition training sequence power allocation factor �� is in 0��0.1, the SLM method and the tradition SLM method that adopt overlying training sequence are close, influential system does not reduce PAPR performance, receiving terminal is by utilizing channel estimation method just can recover side information, thus saving bandwidth and reducing hardware complexity.
Refer to Fig. 7, it can be seen that as complementary cumulative distribution function CCDF=10-3Time, the SLM method of improvement reduces the PAPR of 1dB than traditional SLM method.
Refer to Fig. 8, it can be seen that along with the ability of the increase improved method reduction PAPR of phase sequence number is consequently increased, the row vector of Hardmard can not only reduce PAPR as phase sequence simultaneously, it is also possible to keeps relatively low complexity.
By PAPR simulation curve Fig. 7, Fig. 8 of embodiment it can be seen that the SLM method of the improvement of present invention proposition more can reduce PAPR than traditional SLM method, and along with the ability of the increase improved method reduction PAPR of phase sequence number is consequently increased.
Claims (2)
1. the method that speed wireless data transfer reduces peak-to-average force ratio, specifically comprises the following steps that
First the down-hole digital signal received is carried out serioparallel exchange and obtains parallel signal sequences by step 1:OFDM manipulator: Xn=[X1,X2,��XN], n represents the number of signal sequence, n=1,2 ..., N;
Step 2: each signal sequence X in parallel signal sequencesn, it is multiplied with Hadamard matrix H and obtains signal X 'n;
Step 3: again by the front U row vector H of Hadamard matrixuAs phase sequence, according to Superposition FormulaIt is superimposed upon signal X 'nObtain signalWherein u represents the number of phase sequence, u=1,2 ..., U, �� is power allocation factor, 0 < �� < 0.1;
Step 4: signalAgain with phase sequence HuCorrespondence is multiplied and obtains the more options signal sequence of a down-hole digital signalU=1,2 ..., U, n=1,2 ..., N;
Step 5: from the more options signal sequence of gainedMiddle selection has the signal sequence of minimum PAPR valueSend;
Step 6: first the ofdm demodulator at aboveground receiver module recovers phase sequence H by channel estimation methodsu, then adopt inverse process demodulation to recover original down-hole digital signal.
2. the method that a kind of speed wireless data transfer according to claim 1 reduces peak-to-average force ratio, it is applied to a kind of downhole data high speed radio transmission system, it is characterised in that: described downhole data high speed radio transmission system is made up of down-hole acquisition module, ofdm signal transport module and aboveground receiver module; Described down-hole acquisition module includes sensor assembly and analog-digital converter module, the position being arranged on drill bit below square drill collar; Described ofdm signal transport module includes down-hole OFDM manipulator, ofdm signal transmission pipe nipple; Described aboveground receiver module includes: ofdm demodulator, digital to analog converter module and signal recover module; Described ofdm signal transmission pipe nipple includes ofdm demodulator, wireless repeater and OFDM manipulator; Described down-hole OFDM manipulator all includes coding mapping module, serial/parallel module, weak energy supposition training sequence module, IFFT module, parallel/serial module, protection interval module, D/A converter module, rf modulations module with the OFDM manipulator in ofdm signal transmission pipe nipple; Described aboveground ofdm demodulator all includes with the ofdm demodulator in ofdm signal transmission pipe nipple: radio demodulating module, analog-to-digital conversion module, synchronization channel estimation module, training sequence module, deprotection interval module, serial/parallel module, FFT module, parallel/serial module, decoding De-mapping module;
Wherein signals collecting, transmitting, transmission and reception process are as follows: the waveshape signal that first sensor assembly will collect, and become bit stream by analog-digital converter module; Its signal is transferred to the down-hole OFDM manipulator being arranged on nearly drill bit place along drill string, and bit stream is modulated into ofdm signal; Ofdm signal after process is transferred to the ofdm signal transmission pipe nipple at 50 meters of with electromagnetic wave along drill string, and in drill string, every 50 meter amperes fill an ofdm signal transmission pipe nipple; Signal is transferred to along drill string in the ofdm demodulator of aboveground receiver module always and is demodulated, and by the digital-to-analogue conversion again of the signal of demodulation, recovers and be transferred to terminal to process.
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| CN104453868B (en) * | 2013-09-23 | 2023-06-13 | 中国石油集团长城钻探工程有限公司 | Device and method for synthesizing emission signals of induction logging instrument and induction logging method |
| CN108071385B (en) * | 2016-11-17 | 2021-03-16 | 中国石油化工股份有限公司 | Method and circuit for measuring electromagnetic wave resistivity amplitude ratio and phase difference while drilling |
| CN108063657B (en) * | 2017-12-13 | 2021-01-26 | 电子科技大学 | Logging-while-drilling data NC-OFDM sound wave transmission method based on compressed sensing |
| CN110971559B (en) * | 2019-12-18 | 2022-02-01 | 南京信息工程大学 | Modulation and demodulation method for reducing peak-to-average power ratio of OFDM-PON signal |
| CN113775320A (en) * | 2021-11-11 | 2021-12-10 | 滨州学院 | Underground water injection device and underground water injection method |
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