CN101202564B - Channel initialization method - Google Patents
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- CN101202564B CN101202564B CN2007101783032A CN200710178303A CN101202564B CN 101202564 B CN101202564 B CN 101202564B CN 2007101783032 A CN2007101783032 A CN 2007101783032A CN 200710178303 A CN200710178303 A CN 200710178303A CN 101202564 B CN101202564 B CN 101202564B
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Abstract
A channel initialization method includes the following steps: A1) a ground end modem and an underground end modem respectively send a first training sequence to each other; B1) the modem received the first training sequence finishes the training of channel activation, multi-carrier clock synchronization, multi-carrier symbol synchronization, multi-carrier frame synchronization, AGC parameter arrangement, transmission power adjustment, time-domain equalizer and frequency-domain equalizer; C1) the ground end modem and the underground end modem respectively send a second training sequence to each other; D1) the modem received the second training sequence carries out subchannel SNR estimation to the training sequence and carries out bit and energy distribution to each subchannel according to the estimated SNR value; E1) the ground end modem and the underground end modem respectively send a subchannel bit distribution information and a subchannel energy distribution information to each other.
Description
Technical field
The present invention relates to a kind of channel initialization method, relate in particular to a kind of channel initialization method that is used for logging cable.
Background technology
Logging system generally includes ground installation (ground surface end equipment) and downhole instrument (downhole end equipment) two parts, and ground installation links to each other by logging cable with downhole instrument.Downhole instrument need be transferred to ground installation by logging cable with the data that collect; And ground installation also needs transfer of data such as control commands to downhole instrument.
Logging operation starts from 20th century the '20s～the '30s, and logging system has experienced the development from analog to digital.Developed into for the 5th imaging logging stage in generation at present.Along with the development of logger, to the also raising gradually of demand of message transmission rate.
In order to satisfy the demand that message transmission rate is improved constantly, a large amount of researchers studies the well logging transmission technology.The sixties were adopted analogue modulation system transportation simulator amounts such as frequency modulation, amplitude modulation in the past basically, data quantity transmitted seldom, transmission rate is also very low.The eighties, the well logging transmission technology begins to adopt in a large number digital modulation mode, but message transmission rate still can't satisfy the demands.
For example, it is 3502 PCM (PulseCode Modulation, pulse code modulation) modulator that Atlas company is developed into code name mid-term in the eighties, and transmission rate only is 7.5 kbps.Afterwards, the modulation-demodulation technique of the said firm begins to adopt the Manchester's code mode, and transmission rate is brought up to 93.35kbps (model is WTC3510).
Schlumberger company adopts phase shift keying (Phase Shift Keying is called for short PSK) modulation system transmission data always.The eighties was developed the Digital Transmission pipe nipple of CCS and two kinds of models of CTS before mid-term, and wherein the transmission rate of CCS is 80kbps, and the transmission rate of CTS is 100kbps.CCS and CTS all adopt BPSK (Binary Phase Shift Keying, binary phase shift keying) modulation technique.The early 1990s is developed the Imaging Logging System that model is MAX-500, and on behalf of its spread of the rumours system data uplink speed, " 500 " in " MAX-500 " can reach 500kb/s.The spread of the rumours system of Schlumberger company is called DTS numeral the spread of the rumours system, adopt QAM (Quadrature AmplitudeModulation, quadrature amplitude modulation) technology can reach the message transmission rate of 500kbps, can satisfy the needs that the transmission of instrument amount of information is surveyed in imaging basically.In the Imaging Logging System EXCELL-2000 that Halliburton Company releases, its spread of the rumours system (model is DITS) adopts the binary code transmission of modulation, and uploading rate is 217.6kbps.The model that Bake-Atlas company releases is in the Imaging Logging System of ECLIPS-2000, and its spread of the rumours system (model is WTC) adopts the Manchester code transmission, and uploading rate is 230kbps.
But, along with the real-time requirement of modern logging system is more and more higher, need data quantity transmitted more and more between ground installation and the downhole instrument, the transmission rate of present logging system can't meet the demands.
Summary of the invention
Technical problem to be solved by this invention is, overcomes the deficiencies in the prior art, proposes a kind of channel initialization method that is used for the two-forty of logging cable.
In order to address the above problem, the invention provides a kind of channel initialization method, be applied to comprise in the well logging communication system of the ground surface end that links to each other by logging cable and downhole end, it is characterized in that this method comprises following steps:
A1) ground surface end modulator-demodulator and downhole end modulator-demodulator send first training sequence to the other side respectively;
B1) modulator-demodulator that receives first training sequence finish channel activation, multicarrier clock synchronization, multicarrier symbol synchronously, the training of multicarrier frame synchronization, the setting of AGC parameter, transmitted power adjustment, time-domain equalizer and frequency-domain equalizer;
C1) ground surface end modulator-demodulator and downhole end modulator-demodulator send second training sequence to the other side respectively;
D1) this training sequence of modulator-demodulator that receives second training sequence carries out subchannel SNR estimation, according to the SNR value that estimation obtains each subchannel is carried out bit and energy distribution;
E1) ground surface end modulator-demodulator and downhole end modulator-demodulator send subchannel bit distribution information and sub-channel energy assignment information to the other side respectively.
In addition, at described step B1) and C1) between also comprise following steps: ground surface end modulator-demodulator and downhole end modulator-demodulator send an ACK sequence to the other side respectively;
At described step D1) and E1) between also comprise following steps: ground surface end modulator-demodulator and downhole end modulator-demodulator send the 2nd ACK sequence to the other side respectively.
In addition, the signal of described first training sequence and the second training sequence correspondence carries out the BPSK modulation by PRBS and forms, and the mapping ruler of BPSK constellation is 1 →-1, and 0 →+1; The generator polynomial of PRBS is: x
8+ x
6+ x
5+ x
4+ 1; Described second training sequence has different phase places with first training sequence.
In addition, the signal of a described ACK sequence and the 2nd ACK sequence correspondence carries out the BPSK modulation by PRBS and forms, and the mapping ruler of BPSK constellation is 1 →-1, and 0 →+1; The generator polynomial of PRBS is: x
8+ x
6+ x
5+ x
4+ 1; A described ACK sequence, the 2nd ACK sequence have different phase places with described first training sequence and second training sequence.
In sum, adopt the data sending, receiving method and the device that the present invention is based on OFDM, and corresponding channel initialization method, on existing logging cable, significantly improved message transmission rate, satisfied the transmission requirement of the big data quantity of downhole instrument.
Description of drawings
Fig. 1 is the logging system structural representation that adopts channel initialization of the present invention and data transmission method;
Fig. 2 is the schematic diagram that carries out channel distribution according to the pairing OFDM basic parameter of logging cable;
Fig. 3 is the channel initialization method flow chart that the embodiment of the invention is used for logging cable;
Fig. 4 is the system configuration schematic diagram of the modulator in the embodiment of the invention data sending device;
Fig. 5 is the flow chart of the modulator approach in the embodiment of the invention data transmission method;
Fig. 6 is to use the formed superframe structure schematic diagram of embodiment of the invention data transmission method for uplink;
Fig. 7 is the system configuration schematic diagram of the demodulator in the embodiment of the invention data sending device;
Fig. 8 is the flow chart of embodiment of the invention transfer of data demodulation method.
Embodiment
Basic ideas of the present invention are that in order to improve message transmission rate, with multi-transceiver technology, especially OFDM (Orthogonal Frequency Division Multiplexing, OFDM) technology is applied to the transfer of data of logging cable.
Multi-transceiver technology is exactly to realize parallel data transmission and multichannel data transmission by the frequency division multiplexing technology such as (FDM) that frequency spectrum overlaps, to improve the transmission rate of data.Wherein, adopt discrete Fourier transform (DFT) (DFT) to realize the FDM scheme usually.
In various FDM technology, be one of the most promising modulation-demodulation technique of communication technical field based on the OFDM technology of multi-carrier scheme.The information code current that OFDM is very high with speed is divided into many low speed code streams, carries out parallel transmission on the subchannel of one group of quadrature.Adopt the OFDM technology can expand the width of subchannel transmission symbol, thus the design of equalizer in the simplified receiver greatly.The OFDM technology adopts guardtime (to be called for short TGI) at interval and removes intersymbol interference (being called for short ISI) effectively simultaneously, has overcome the channel delay expansion less than TGI.On the other hand, utilize the orthogonality between subcarrier, the OFDM technology has improved the availability of frequency spectrum effectively.Compare with traditional single-carrier technology, OFDM has the higher availability of frequency spectrum, its availability of frequency spectrum is along with the number of subchannels purpose increases and convergence Nyquist (Nyquist) limit, and can carry out adaptive bit and energy (power) distribution according to the transmission conditions of each subchannel, to make full use of channel capacity, improve transmission rate.
Describe the present invention below in conjunction with drawings and Examples.
Fig. 1 is the logging system structural representation that adopts channel initialization of the present invention and data transmission method.As shown in Figure 1, this system comprises: ground surface end, downhole end is with the logging cable that is connected ground surface end and downhole end.
Ground surface end comprises: ground based terminal, ground based terminal interface, COFDM (Coded OrthogonalFrequency Division Multiplexing, coded orthogonal frequency division multiplexing) modulator B, COFDM demodulator B, land cable interface.
Downhole end comprises: downhole instrument, downhole instrument interface, COFDM modulator A, COFDM demodulator A, downhole cable interface.
Ground based terminal links to each other with COFDM demodulator B with COFDM modulator B by the ground based terminal interface, transmits and receive data.
COFDM modulator B receives data to be sent from the ground based terminal interface, and the modulation back is sent to downhole end by the land cable interface bearing on logging cable.
COFDM demodulator B is carried on the data that send on the logging cable by land cable interface received well lower end, sends to ground based terminal through after the demodulation by the ground based terminal interface.
COFDM modulator B and COFDM demodulator B can directly carry out data interaction.COFDM modulator B and COFDM demodulator B merging can be called COFDM modulator-demodulator B.
Downhole instrument links to each other with COFDM demodulator A with COFDM modulator A by the downhole instrument interface, transmits and receive data.
COFDM modulator A receives data to be sent from the downhole instrument interface, and the modulation back is sent to ground surface end by the downhole cable interface bearing on logging cable.
COFDM demodulator A receives ground surface end by the downhole cable interface and is carried on the data that send on the logging cable, sends to downhole instrument through after the demodulation by the downhole instrument interface.
Equally, COFDM modulator A and COFDM demodulator A can directly carry out data interaction.Also COFDM modulator A and COFDM demodulator A merging can be called COFDM modulator-demodulator A.
Logging cable adopts the armouring logging cable usually.The embodiment of the invention is determined according to the transmission characteristic of armouring logging cable channel based on the employed part of O FDM system parameters of the data transmission method of OFDM.
With 7000 meters armouring logging cables is example, can determine following OFDM basic parameter according to the transmission characteristic of cable channel:
The available subchannels sum that up channel (Up Link, the down-hole is to ground) comprises: 195;
The available subchannels sum that down channel (Down Link, ground is to the down-hole) comprises: 7.
On the armouring logging cable, carry out channel distribution according to above-mentioned OFDM basic parameter.Fig. 2 is the schematic diagram that carries out channel distribution according to the pairing OFDM basic parameter of logging cable.As shown in Figure 2,
Subcarrier 0～subcarrier 5: as keeping subcarrier (not using).The reason of not using subcarrier 0～subcarrier 5 is to avoid the Alternating Current Power Supply of low frequency end to disturb;
Subcarrier 6～subcarrier 12: as down channel (ground surface end equipment is to downhole end equipment);
The pilot signal of transmitting on the above-mentioned pilot subchannel is a sine wave, is used for carrying out between transmitting terminal and the receiving terminal clock synchronization.
Data transmission method of the present invention is divided into: channel initialization stage and data transfer phase.
Need finish in the channel initialization stage: operations such as communication link foundation, transmission power control, reception AGC parameter, clock synchronization, sign synchronization, frame synchronization, time-domain equalizer training, frequency-domain equalizer training, subchannel performance estimation, subchannel Bit Allocation in Discrete and energy distribution.
Fig. 3 is the channel initialization method flow chart that the embodiment of the invention is used for logging cable.As shown in Figure 3, this method comprises following steps:
101:COFDM modulator A sends training sequence 0 to COFDM modulator-demodulator B;
The signal of training sequence 0 correspondence carries out the BPSK modulation by PRBS (pseudo-random binary sequence) and forms, and the mapping ruler of BPSK constellation is 1 →-1, and 0 →+1.The generator polynomial of PRBS is: x
8+ x
6+ x
5+ x
4+ 1.
Training sequence 0 can use all subchannels of up channel to send, and also can use one or more subchannels to send.Use a plurality of subchannels to send the accuracy that training sequence 0 can increase clock synchronization, equalizer training.
After 102:COFDM modulator-demodulator B receives training sequence 0, finish channel activation, multicarrier clock synchronization, multicarrier symbol synchronously, the training of multicarrier frame synchronization, the setting of AGC parameter, transmitted power adjustment, time-domain equalizer and frequency-domain equalizer.
Be provided with by the AGC parameter, COFDM demodulator B is controlled at the optimum reception level with AGC; Synchronous by multicarrier symbol, COFDM demodulator B adjusts to the optimum position with the FFT window, makes received signal not have to disturb between subchannel; By the training of time-domain equalizer and frequency-domain equalizer, COFDM demodulator B obtains the equalizing coefficient of time domain and frequency-domain equalizer, for follow-up training sequence and transfer of data ready.
By the calculating channel decay, COFDM modulator B carries out the power adjustment, makes transmitted power reach optimum state.
103:COFDM modulator B sends training sequence 0 to COFDM modulator-demodulator A;
Identical in the generation method of training sequence 0 and the step 101.
Equally, training sequence 0 can use all subchannels of down channel to send, and also can use one or more subchannels of down channel to send.
After 104:COFDM modulator-demodulator A receives training sequence 0, finish channel activation, multicarrier clock synchronization, multicarrier symbol synchronously, the training of multicarrier frame synchronization, the setting of AGC parameter, channel response estimation, transmitted power adjustment, time-domain equalizer and frequency-domain equalizer.
Be provided with by the AGC parameter, COFDM demodulator A is controlled at the optimum reception level with AGC; Synchronous by multicarrier symbol, COFDM demodulator A adjusts to the optimum position with the FFT window, makes received signal not have to disturb between subchannel; By the training of time-domain equalizer and frequency-domain equalizer, COFDM demodulator A obtains the equalizing coefficient of time domain and frequency-domain equalizer, for follow-up training sequence and transfer of data ready.
Estimate by channel response, the calculating channel decay, COFDM modulator A carries out the power adjustment, makes transmitted power reach optimum state.
105:COFDM modulator-demodulator A sends ACK (ACKnowledgement confirms to reply) sequence 0 to COFDM modulator-demodulator B;
By sending ACK sequence 0, COFDM modulator-demodulator B knows that COFDM modulator-demodulator A has finished the reception and the corresponding setting of training sequence 0, can enter next stage.
The generating principle of ACK sequence 0 is identical with training sequence 0, just postpones a bit than training sequence 0, so that its phase place is different with training sequence 0.
106:COFDM modulator-demodulator B sends ACK sequence 0 to COFDM modulator-demodulator A;
By sending ACK sequence 0, COFDM modulator-demodulator A knows that COFDM modulator-demodulator B has finished the reception and the corresponding setting of training sequence 0, can enter next stage.
Identical in the generation method of ACK sequence 0 and the step 105.
107:COFDM modulator A sends training sequence 1 to COFDM modulator-demodulator B;
Training sequence 1 sends at all subchannels of up channel.
The generating principle of training sequence 1 is identical with training sequence 0, just postpones 2 bits than training sequence 0, so that its phase place is different with ACK sequence 0 with training sequence 0.
After 108:COFDM modulator-demodulator B receives training sequence 1, carry out subchannel SNR (Signal to Noise Ratio, signal to noise ratio) according to this training sequence and estimate, each subchannel is carried out bit and energy distribution according to the SNR value that estimation obtains.
To determine each subchannel with what constellation is modulated according to above-mentioned subchannel bit and energy distribution result at follow-up data transfer phase, and each subchannel sends with great power.
In the present embodiment, the scope of each subchannel Bit Allocation in Discrete: 0～10bits.
109:COFDM modulator B sends training sequence 1 to COFDM modulator-demodulator A;
Training sequence 1 sends at all subchannels of down channel.The generation method of training sequence 1 is identical with step 107.
After 110:COFDM modulator-demodulator A receives training sequence 1, carry out subchannel SNR according to this training sequence and estimate, each subchannel is carried out bit and energy distribution according to the SNR value that estimation obtains.
Equally, will determine each subchannel with what constellation is modulated according to above-mentioned subchannel bit and energy distribution result at follow-up data transfer phase, and each subchannel sends with great power.
111:COFDM modulator-demodulator A sends ACK sequence 1 to COFDM modulator-demodulator B;
By sending ACK sequence 1, COFDM modulator-demodulator B knows that COFDM modulator-demodulator A has finished the reception and the corresponding setting of training sequence 1, can enter next stage.
ACK sequence 1 in this step is identical with ACK sequence 0.
112:COFDM modulator-demodulator B sends ACK sequence 1 to COFDM modulator-demodulator A;
By sending ACK sequence 1, COFDM modulator-demodulator A knows that COFDM modulator-demodulator B has finished the reception and the corresponding setting of training sequence 1, can enter next stage.
ACK sequence 1 in this step is identical with ACK sequence 0.
113:COFDM modulator-demodulator A is to COFDM modulator-demodulator B transmitting system information;
Said system information comprises: subchannel bit distribution information and sub-channel energy assignment information.
System information adopts the QPSK modulation system, uses one or more subchannels of up channel to send.
In the present embodiment, system information uses 4 subchannels of the low-limit frequency (channel condition is good) of up channel to send, to improve reliability.
114:COFDM modulator-demodulator B is to COFDM modulator-demodulator A transmitting system information;
Equally, said system information comprises: subchannel bit distribution information and sub-channel energy assignment information.
System information adopts the QPSK modulation system, uses one or more subchannels of down channel to send.
In the present embodiment, system information uses 4 subchannels of the low-limit frequency (channel condition is good) of down channel to send, to improve reliability.
115:COFDM modulator-demodulator A sends ACK sequence 2 to COFDM modulator-demodulator B;
By sending ACK sequence 2, COFDM modulator-demodulator B knows that COFDM modulator-demodulator A has finished the reception and the corresponding setting of system information, can enter data transfer phase.
ACK sequence 2 is identical with ACK sequence 0.
116:COFDM modulator-demodulator B sends ACK sequence 2 to COFDM modulator-demodulator A;
By sending ACK sequence 2, COFDM modulator-demodulator A knows that COFDM modulator-demodulator B has finished the reception and the corresponding setting of system information, can enter data transfer phase.
ACK sequence 2 is identical with ACK sequence 0.
As from the foregoing, the setting that is sent completely each messaging parameter by 2 training sequences of the present invention; That is to say that two stages of branch that are provided with of parameter carry out, the parameter setting of second stage can be provided with the result with reference to the parameter of phase I.Adopt this mode, can be provided with messaging parameter more exactly.
In the transmit stage of data, data to be sent are sent out the demodulator that sends to receiving terminal after the modulators modulate of end; Receiving terminal identification also receives modulation signal after send terminal to after the demodulator demodulation.Below in conjunction with drawings and Examples modulation of the present invention, demodulation method and device thereof are described respectively.
Hereinafter, modulator is meant COFDM modulator A and COFDM modulator B; Demodulator is meant COFDM demodulator A and COFDM demodulator B.
Below in conjunction with accompanying drawing modulator of the present invention is carried out concise and to the point introduction.
Fig. 4 is the system configuration schematic diagram of the modulator in the embodiment of the invention data sending device.As shown in Figure 4, this modulator comprises: the randomization unit, and the RS coding unit, interleave unit, the QAM map unit, frequency domain becomes frame unit, the IFFT unit, unit, DAC are inserted in protection at interval.Wherein:
The randomization unit is used for the input data are carried out exporting after the randomization;
The RS coding unit is used for the data of randomization unit output are carried out the back output of FEC (forward error correction coding) coding;
Interleave unit is used for the data of RS coding unit output are carried out exporting after the interleaving treatment;
The QAM map unit is used for the subchannel bit of the data based bit of interleave unit output and energy distribution table and energy distribution information are carried out QAM mapping back output;
Frequency domain becomes frame unit to be used to use the data of QAM map unit output to generate and output frequency domain data frame;
The IFFT unit is used for becoming the frequency domain data frame of frame unit output to carry out the IFFT conversion frequency domain, exports out time domain OFDM signal;
Protection is inserted the unit at interval and is used for the time domain OFDM signal of IFFT unit output being added Cyclic Prefix as the time domain protection at interval, the output baseband transmit signals;
DAC is used for that the baseband transmit signals of exporting the unit is inserted in protection at interval and carries out digital-to-analogue conversion, the output base-band analog signal.
Below in conjunction with accompanying drawing the modulator approach that modulator of the present invention adopted is described in detail.
Fig. 5 is the flow chart of the modulator approach in the embodiment of the invention data transmission method.As shown in Figure 5, this modulator approach comprises following steps:
201: data to be sent enter the physical layer data bag that is divided into 112 byte longs behind the modulator, and the physical layer data bag is admitted to after the randomization unit carries out randomization, output randomization data bag;
The randomization unit produces the PRBS sequence by PRBS generator, and the physical layer data bag of this PRBS sequence and input carries out mould 2 and adds and finish randomization.
The generator polynomial of above-mentioned PRBS sequence is: x
15+ x
14+ 1.
202: the randomization data bag be admitted to RS (Reed-Solomon, Reed. the Saloman) coding unit carries out FEC (forward error correction coding) coding, exports the RS coded data packet of 128 byte longs;
The RS coding unit uses following parameter: error correcting capability t=8; Data total length=128; Data original length=112.
The territory generator polynomial of RS sign indicating number is: p (x)=x
8+ x
4+ x
3+ x
2+ 1;
The sign indicating number generator polynomial of RS sign indicating number is:
g(x)＝(x+λ
0)(x+λ
1)(x+λ
2)...(x+λ
15)＝g
16x
16+...+g
1x+g
0。
The 203:RS coded data packet is admitted to interleave unit and carries out interleaving treatment, output interleaving data bag;
Interleave unit adopts convolutional interleave, and its parameter is: weaving width I=8, interleave depth M=16.
The RS coded data packet can strengthen the performance of its RS sign indicating number error correction through interleaving treatment.
204: the interleaving data bag is admitted to the QAM map unit and shines upon processing;
Subchannel bit and energy distribution information (being stored in bit and the energy distribution table) that map unit obtained according to the channel initialization stage, data in the interleaving data bag are distributed to each subchannel by corresponding bit number, and be mapped as corresponding qam constellation point, the frequency domain data after output QAM modulates.
The data of 205:QAM map unit output are admitted to frequency domain and become frame unit to generate the frequency domain data frame.
206: the frequency domain data frame is admitted to IFFT (Inverse Fast Fourier Transform, invert fast fourier transformation) unit and carries out the IFFT conversion, promptly carries out OFDM modulation and produces time domain OFDM signal (comprising several OFDM symbols).
The ofdm signal that generates after the 207:IFFT conversion be admitted to protection insert at interval the unit add Cyclic Prefix as the time domain protection at interval (TGI) just form the time domain baseband transmit signals; The time domain baseband transmit signals is sent into the logging cable Channel Transmission through DAC (Digital Analog Convert, digital-to-analogue conversion) behind the generation base-band analog signal.
Fig. 6 is to use the formed superframe structure schematic diagram of embodiment of the invention data transmission method for uplink; As shown in Figure 6, a superframe is made up of 128 OFDM symbols and 2 synchronization frames.
1 OFDM symbol is made of 1 CP and 1 IFFT piece; The length of CP is 1/4 of IFFT block length.
2 synchronization frame: SYNC and
, lay respectively at the 1st OFDM symbol (Data 0) before, between the 64th OFDM symbol (Data 63) and the 65th the OFDM symbol (Data 64).Wherein, SYNC is identical with training sequence 0, and length is 256;
Anti-phase for SYNC.
Below in conjunction with accompanying drawing demodulator of the present invention is carried out concise and to the point introduction.
Fig. 7 is the system configuration schematic diagram of the demodulator in the embodiment of the invention data sending device.As shown in Figure 7, this demodulator comprises: ADC, time domain equalization unit, the channel information getter, the AGC unit, synchronous correction unit, FFT (Fast Fourier Transform, fast fourier transform) unit, frequency-domain balancing unit, QAM separates map unit, the deinterleaving unit, the RS decoding unit is separated the randomization unit.Wherein,
ADC is used for the base-band analog signal of input is carried out analog-to-digital conversion, the output digital signal;
The time domain equalization unit is used for extracting the time-domain equalizer coefficient that the channel initialization stage obtains from the channel information getter, and use this coefficient that the digital signal of ADC output is carried out time domain equalization with the brachymemma channel impulse response, the time delay expansion that channel impulse response is caused drops within the TGI scope;
The AGC unit is used for carrying out the setting and the adjustment of AGC parameter according to the digital signal of ADC output;
The synchronous correction unit is used for extracting the synchronizing information that the channel initialization stage obtains from the channel information getter, and uses this information that the data of time domain equalization unit output are entered and export after TGI is removed in the synchronous correction unit;
The FFT unit is used for the data of synchronous correction unit output are carried out exporting after the FFT conversion;
Frequency-domain balancing unit is used for extracting the frequency domain equalizer coefficients that the channel initialization stage obtains from the channel information getter, and uses this coefficient that the data of FFT unit output are carried out frequency domain equalization and handle;
QAM separates map unit and is used for extracting the bit distribution information that initial phase obtains from the channel information getter, and uses this information that the data of frequency-domain balancing unit output are carried out QAM and separate mapping;
Deinterleaving unit and RS decoding unit are used for that the data that QAM separates map unit output are carried out deinterleaving and back output is handled in RS decoding;
Separate and export user data after the randomization unit is used for the data of deinterleaving unit and RS decoding unit output are separated randomization.
Below in conjunction with accompanying drawing the demodulation method that demodulator of the present invention adopted is described in detail.
Fig. 8 is the flow chart of embodiment of the invention transfer of data demodulation method.As shown in Figure 8, this demodulation method comprises following steps:
301: base-band analog signal is sent into the time domain equalization unit and is carried out time domain equalization with the brachymemma channel impulse response after ADC (Analog Digital Convert, analog-to-digital conversion) sampling, and the time delay expansion that channel impulse response is caused drops within the TGI scope.
The time domain equalization unit carries out time domain equalization from the time-domain equalizer coefficient that the channel information getter extracts the acquisition of channel initialization stage.
In addition, the data after the ADC sampling are also sent into setting and the adjustment that the AGC unit carries out the AGC parameter.
302: after the data of time domain equalization unit output enter synchronous correction unit removal TGI, export;
The synchronous correction unit carries out synchronous correction from the synchronizing information that the channel information getter extracts the acquisition of channel initialization stage.
303: the data of synchronous correction unit output are admitted to FFT (Fast Fourier Transform, fast fourier transform) unit and carry out the FFT conversion.
The data of exporting after the 304:FFT conversion enter frequency-domain balancing unit and carry out the frequency domain equalization processing;
Frequency-domain balancing unit is carried out frequency domain equalization from the frequency domain equalizer coefficients that the channel information getter extracts the acquisition of channel initialization stage.
305: the data of frequency-domain balancing unit output enter QAM and separate map unit and carry out QAM and separate mapping;
QAM separates map unit and extracts bit distribution information that initial phase obtains from the channel information getter and carry out QAM and separate mapping.
The data that 306:QAM separates map unit output enter the deinterleaving unit and the RS decoding unit carries out deinterleaving and back output is handled in RS decoding;
The deinterleaving unit adopts convolution de-interleaving, and its parameter is: weaving width I=8, interleave depth M=16.
The RS decoding unit uses following parameter: error correcting capability t=8; Data total length=128; Data original length=112.
The territory generator polynomial of RS sign indicating number is: p (x)=x
8+ x
4+ x
3+ x
2+ 1;
The sign indicating number generator polynomial of RS sign indicating number is:
g(x)＝(x+λ
0)(x+λ
1)(x+λ
2)...(x+λ
15)＝g
16x
16+...+g
1x+g
0。
307: handle the data of exporting the back through deinterleaving unit and RS decoding unit and enter and separate the randomization unit and separate randomization to obtain original user data;
Separate the randomization unit and produce the PRBS sequence by PRBS generator, the physical layer data bag of this PRBS sequence and input carries out mould 2 and adds to finish and separate randomization.
The generator polynomial of above-mentioned PRBS sequence is: x
15+ x
14+ 1.
In sum, the present invention is according to the superiority of OFDM technology in transfer of data, and in conjunction with the characteristics of logging system own, proposed this logging cable high-speed data transmission method based on the OFDM technology.Use method and apparatus of the present invention, on 7000 meters armouring logging cables, can realize uploading rate 800kbps, the high speed data transfer of following biography speed 30kbps.
Claims (4)
1. channel initialization method is applied to comprise in the well logging communication system of the ground surface end that links to each other by logging cable and downhole end, it is characterized in that this method comprises following steps:
A1) ground surface end modulator-demodulator and downhole end modulator-demodulator send first training sequence to the other side respectively;
B1) modulator-demodulator that receives first training sequence finish channel activation, multicarrier clock synchronization, multicarrier symbol synchronously, the training of multicarrier frame synchronization, the setting of AGC parameter, transmitted power adjustment, time-domain equalizer and frequency-domain equalizer;
C1) ground surface end modulator-demodulator and downhole end modulator-demodulator send second training sequence to the other side respectively;
D1) modulator-demodulator that receives second training sequence carries out subchannel SNR estimation according to this second training sequence, according to the SNR value that estimation obtains each subchannel is carried out bit and energy distribution;
E1) ground surface end modulator-demodulator and downhole end modulator-demodulator send subchannel bit distribution information and sub-channel energy assignment information to the other side respectively.
2. channel initialization method as claimed in claim 1 is characterized in that,
At described step B1) and C1) between also comprise following steps: ground surface end modulator-demodulator and downhole end modulator-demodulator send an ACK sequence to the other side respectively;
At described step D1) and E1) between also comprise following steps: ground surface end modulator-demodulator and downhole end modulator-demodulator send the 2nd ACK sequence to the other side respectively.
3. channel initialization method as claimed in claim 2 is characterized in that, the signal of described first training sequence and the second training sequence correspondence carries out the BPSK modulation by pseudo-random binary sequence PRBS and forms, and the mapping ruler of BPSK constellation is 1 →-1,0 →+1; The generator polynomial of PRBS is: x
8+ x
6+ x
5+ x
4+ 1; Described second training sequence has different phase places with first training sequence.
4. channel initialization method as claimed in claim 3 is characterized in that, the signal of a described ACK sequence and the 2nd ACK sequence correspondence carries out the BPSK modulation by PRBS and forms, and the mapping ruler of BPSK constellation is 1 →-1,0 →+1; The generator polynomial of PRBS is: x
8+ x
6+ x
5+ x
4+ 1; A described ACK sequence, the 2nd ACK sequence have different phase places with described first training sequence and second training sequence.
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| US8837561B2 (en) * | 2012-11-21 | 2014-09-16 | Texas Instruments Incorporated | Initialization sequence for bi-directional communications in a carrier-based system |
| CN107710669B (en) * | 2015-09-21 | 2020-06-02 | 华为技术有限公司 | Data transmission method, transceiving equipment and system |
| CN107610435B (en) * | 2017-08-18 | 2019-06-18 | 中国科学院地质与地球物理研究所 | The high speed logging remote transmission means of communication suitable for multiple types cable |
| CN112187695B (en) * | 2020-09-30 | 2021-12-14 | 中国科学技术大学 | FPGA channel pre-emphasis and equalization method and system based on OFDM high-speed logging telemetry system |
| CN112761625B (en) * | 2020-12-18 | 2021-09-28 | 中国科学院地质与地球物理研究所 | Synchronization method of measurement while drilling system |
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