In-well ultra-long cable communication system and method based on polarization coding

Abstract

The invention discloses an in-well ultra-long cable communication system and method based on polarization coding, and relates to the field of wired communication. The system comprises in-well telemetry equipment, ground communication equipment and an upper computer, the method comprises the following steps: firstly, performing OFDM modulation on original data in a well based on polarization coding; then carrying out digital-to-analog conversion on the modulated OFDM signal; the analog signal is transmitted to ground communication equipment, and an OFDM sampling signal is acquired; and finally, demodulating the OFDM sampling signal, and displaying and storing the OFDM sampling signal according to a preset data frame format to complete acquisition and storage of data in the well. Polarization coding adopted by the method is suitable for high-speed data transmission in a well, and especially under the condition that the requirement for the data transmission rate is high, coding and decoding mechanisms of the polarization coding can be utilized, and the bit error rate is reduced; in a well cable communication environment with large noise and interference, polarization coding can distribute information bits to reliable channels through polarization characteristics of the polarization coding, so that the anti-interference capability is improved.

Description

Technical Field

[0001] The present invention relates to the field of wired communications, and in particular to an ultra-long cable communication system and method in a well based on polarization coding. Background Art

[0002] Polarization coding is efficient and reliable and can be applied to wired cable communications, especially when channel conditions are complex and interference exists. Through channel modeling and optimization design, polarization coding can be effectively integrated into the wired communication system to improve the performance and reliability of the communication system. In long-distance borehole cable communications, extremely narrow channels, signal attenuation, and noise interference can significantly affect the communication quality. Implementing polarization coding in borehole cable communications can improve the channel's fault tolerance through its characteristics close to the Shannon limit, thereby enhancing the reliability of signal transmission.

[0003] With the growing demand for formation information, the borehole detection system has undergone a series of iterative upgrades, and the detection methods have become more diversified. Along with these improvements, many advanced borehole equipment has adopted high-sampling rate acquisition chips, which has created a demand for higher transmission throughput. Long-distance detection is an important indicator of my country's logging projects. Considering that my country's borehole radar system needs to work in a high-temperature and high-pressure environment at a depth of 1000 to 6000m, and the borehole is full of mud, the ultra-long communication distance and the changes in distribution parameters and resistance caused by the stretching of the logging cable will seriously affect the signal reliability. As the requirements for logging depth continue to increase and the sampling rate of logging equipment gradually increases, this requires that the borehole communication has a greater throughput, and it is necessary to solve the problems caused by ultra-deep well exploration, among which the problems from the cable need to be given priority. First of all, due to the long length of the logging cable itself, the well environment is time-varying and noisy, which is a situation that needs to be solved in actual engineering experiments, which requires the system to have long-distance communication and anti-interference functions.

[0004] Many well logging projects in my country use the mainstream seven-core armored cable. Each cable core is made of 7 copper wires twisted together, covered with an insulating layer on the outside, and the outermost layer is covered with two layers of steel armor with different thicknesses wound in both directions. The total length of the cable is more than 7 kilometers. The cable in the well can be approximated as a narrowband low-communication channel. High-frequency signals can hardly pass through the ultra-long cable in the well, which results in the communication rate in the well being limited by the signal bandwidth. Since the equipment works deep underground, the system cannot detect problems in real time during logging work, and the equipment often fails to receive data and cannot issue instructions from the well.

[0005] The basic idea of ​​polarization coding is to combine multiple identical channels into a new set of channels through the channel polarization process, in which some channels become completely reliable and others become completely unreliable. Through this polarization effect, information bits can be transmitted to reliable channels, while frozen bits (known fixed bits) are placed on unreliable channels, thereby achieving reliable transmission close to the channel capacity. In logging cable communications, polarization codes are combined with OFDM (orthogonal frequency division multiplexing) to achieve efficient coding and modulation, so that high-priority information bits can be mapped to subcarriers with high signal-to-noise ratios, ensuring reliable transmission of information bits under complex channel conditions and improving the overall performance and reliability of the system.

[0006] Polarization coding divides channels into reliable and unreliable categories based on the principle of channel polarization, thereby achieving an efficient coding scheme close to the channel capacity. It has broad application prospects in modern communication systems, especially in 5G communications, where it has been put into practical use and verified. Therefore, polarization coding is also one of the most promising methods in well logging communication engineering. In long-distance wired communications, signal attenuation and noise interference may significantly affect the communication quality. Polarization coding can improve the fault tolerance of the channel through its characteristics close to the Shannon limit, thereby enhancing the reliability of signal transmission. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides an ultra-long cable communication system and method in a well based on polarization coding, which solves the problems of low communication rate and low data reliability in current well logging projects.

[0008] The technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides an ultra-long cable communication method in a well based on polarization coding, comprising the following steps:

[0010] Step 1: Perform OFDM modulation on the original data in the well based on polarization coding: Utilize the recursive construction of polarization code to encode the original data in the well into a bit sequence based on the generator matrix G.

[0011] The generator matrix G is:

[0012]

[0013] in, represents the Kronecker power.

[0014] The generated bit sequence expression is:

[0015]

[0016] Among them, xA is the bit sequence generated by the encoding, u A is the original information sequence, and A is a set of integer indicators.

[0017] For bit sequence x A Perform QAM (quadrature amplitude modulation) mapping by group to generate complex number s:

[0018]

[0019] in, and According to the bit sequence x A The real part mapping value and the imaginary part mapping value obtained by the sequence values ​​of the front and back parts in each group, and the multiple complex numbers s generated constitute a complex number sequence S.

[0020] Then the complex sequence S is used as input data for IFFT (Inverse Fast Fourier Transform) processing to obtain the OFDM signal X(n):

[0021]

[0022] Among them, s k represents the kth complex number in the complex sequence S, k is the sequence number of the complex sequence, N is the total number of subcarriers, n is the subcarrier number, and j represents the imaginary unit.

[0023] Step 2: Perform digital-to-analog conversion on the obtained OFDM signal X(n) to obtain an analog signal; transmit the analog signal to the ground communication equipment through the communication cable in the well, and collect the OFDM sampling signal.

[0024] Step 3: Demodulate the OFDM sampling signal and decode the demodulated data The data is displayed and stored according to the preset data frame format to complete the collection and storage of well data.

[0025] Furthermore, in step 1, a pilot signal is inserted into the complex sequence S, and then the complex sequence S with the pilot sequence is used as input data for IFFT processing; the purpose of inserting the pilot signal is to use the pilot signal for subsequent equalization processing to resist interference caused by subchannel fading and synchronization errors.

[0026] Furthermore, the distribution pattern of the pilot signal is a comb-shaped distribution.

[0027] Further, in step 3, the step of demodulating the OFDM sampling signal includes:

[0028] S32. The OFDM sampling signal is processed by FFT (Fast Fourier Transform) to obtain a received complex sequence; the received complex sequence is subjected to time domain equalization and frequency domain equalization in combination with the pilot signal to reduce noise, restore the signal phase and amplitude, and facilitate QAM demapping; the equalized complex sequence is subjected to QAM demapping to obtain a bit sequence y i .

[0029] S33. Bit sequence y i Polar code decoding: According to the serial cancellation decoding algorithm, the bit sequence y i The likelihood ratio is expressed as:

[0030]

[0031] Among them, W(y i ∣0) and W(y i |1) represents the channel transition probability when the input is 0 and 1 respectively.

[0032] Set decoding data The judgment criteria are:

[0033]

[0034] in, Represents the estimation of the source bits of level 1 to i-1; based on the decision criterion, the bit sequence y i Make a decision and get the decoded data

[0035] Furthermore, in step 3, the decoded data The well parameter information is extracted and displayed on the host computer after parsing according to the preset data frame format; at the same time, the well parameter information is stored in the host computer and a data file is generated for subsequent reading.

[0036] In a second aspect, the present invention provides an ultra-long cable communication system in a well based on polarization coding, comprising an in-well telemetry device, a ground communication device and a host computer, wherein the in-well telemetry device and the ground communication device are interconnected via an in-well communication cable, and the ground communication device and the host computer are interconnected via an Ethernet interface.

[0037] The well telemetry equipment is used to control the working mode of the well equipment according to the received control instructions, complete the acquisition of raw data in the well, perform OFDM modulation on the raw data in the well based on polarization coding, and finally send the modulated OFDM signal to the ground communication equipment through the well communication cable.

[0038] The ground communication equipment is used to collect the OFDM signal sent by the telemetry equipment in the well, and send the collected OFDM sampling signal to the host computer; it is also used to transmit the command sent by the host computer to the telemetry equipment in the well.

[0039] The host computer device is used to perform OFDM demodulation on the OFDM sampling signal, and to display and store the demodulated data; and is also used to send control instructions to the remote transmission device in the well.

[0040] Furthermore, the well telemetry equipment realizes control command reception and analysis, data collection encoding and modulation, and control of well equipment working mode through the well telemetry FPGA chip. Specifically, the well telemetry FPGA chip includes a command reception module, a modulation module, and an equipment control module;

[0041] The instruction receiving module is used to receive and analyze the control instructions from the host computer device, and send the analyzed control instructions to the device control module;

[0042] The equipment control module is used to control the working mode of the equipment in the well according to the received control instructions, and complete the collection of raw data in the well.

[0043] The modulation module performs OFDM modulation on the original data in the well based on polarization coding, obtains the modulated OFDM signal and transmits it to the ground communication equipment through the communication cable in the well.

[0044] Furthermore, the ground communication equipment includes a power supply module and a communication module.

[0045] The power supply module adopts AC-DC-AC mode to power the remote transmission equipment in the well; since the extra-long cable has a capacitive effect, using AC-DC-AC for power supply can achieve electrical isolation, block the capacitive effect, and the output voltage is adjustable.

[0046] The communication module is used to realize data transmission between the host computer device and the well telemetry device; the communication module uses an Ethernet interface to connect to the host computer device, uses an ADC data acquisition module to collect OFDM signals uploaded by the well telemetry device, and uses a UART serial port protocol to transmit control instructions to the well telemetry device.

[0047] The beneficial effects of the present invention are:

[0048] 1. The application of polarization code in wired communication is mainly reflected in its efficient encoding and decoding capabilities. For wired communication systems such as well cable communication, polarization code can provide a stable encoding scheme, making the data more robust and anti-interference during transmission.

[0049] 2. Polarization codes have stronger adaptive capabilities. By adjusting the frozen bits, polarization codes can adapt to the time-varying channel characteristics of the cable in the well caused by temperature and stretching, ensuring transmission stability.

[0050] 3. Polar codes can still maintain good error correction performance under low signal-to-noise ratio conditions, so they can transmit signals at lower power levels, increase data transmission speeds, and avoid the situation where traditional coding methods have poor performance under low signal-to-noise ratio conditions and require a higher signal-to-noise ratio to maintain communication quality.

[0051] 4. Polarization codes can achieve efficient coding under extremely limited bandwidth conditions in underground cable channels, enabling higher data transmission speeds even under extremely narrow bandwidth conditions, avoiding the situation where traditional coding methods need to sacrifice some speed to ensure reliability under bandwidth-limited conditions.

[0052] 5. The strong error correction capability and anti-interference performance of the polarization code enable it to maintain a high data transmission rate in an environment with high high-frequency attenuation and noise interference of the well cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The operating principle diagram of the ultra-long cable communication system in a well based on polarization coding of the present invention;

[0054] Figure 2 The overall coordination principle diagram of the system of the present invention;

[0055] Figure 3 The FPGA internal logic block diagram of the well telemetry equipment part of the present invention;

[0056] Figure 4 Internal block diagram of the ground communication device of the present invention;

[0057] Figure 5 The logic block diagram of the host computer device of the present invention;

[0058] Figure 6 Schematic diagram of the training sequence distribution used in the present invention. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of protection of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The present invention is further described below in conjunction with the drawings.

[0060] This embodiment provides a method and system for ultra-long cable communication in a well based on polarization coding, which is used for deep well detection operations, as follows:

[0061] like Figure 2 As shown, the system includes an in-well telemetry device, a ground communication device and a host computer, wherein the in-well telemetry device and the ground communication device are interconnected via an in-well communication cable, and the ground communication device and the host computer are interconnected via an Ethernet interface.

[0062] The well telemetry equipment, such as Figure 3 As shown, the well telemetry FPGA chip is used to realize the control command reception and analysis, the collection data encoding and modulation, and the control of the well equipment working mode. Specifically, the well telemetry FPGA chip includes a command receiving module, a modulation module, and an equipment control module.

[0063] The instruction receiving module is used to receive and analyze the control instructions from the host computer device, and send the analyzed control instructions to the device control module.

[0064] The equipment control module is used to control the working mode of the equipment in the well according to the received control instructions, and complete the collection of raw data in the well.

[0065] The modulation module is used to perform OFDM modulation on the original data in the well based on polarization coding, obtain the modulated OFDM signal and transmit it to the ground communication equipment through the communication cable in the well; the modulation module includes a well data receiving module, a polarization coding module, a QAM mapping module, a pilot insertion module, an IFFT module, and a DAC control module.

[0066] The ground communication equipment, such as Figure 4 As shown, it includes a power supply module and a communication module.

[0067] The power supply module adopts AC-DC-AC mode to power the remote transmission equipment and communication module in the well; since the extra-long cable has a capacitive effect, using AC-DC-AC for power supply can achieve electrical isolation, block the capacitive effect, and the output voltage is adjustable.

[0068] The communication module is used to realize data transmission between the host computer device and the well telemetry device; the communication module uses an Ethernet interface to connect to the host computer device, uses an ADC data acquisition module to collect OFDM signals uploaded by the well telemetry device, and uses a UART serial port protocol to transmit control instructions to the well telemetry device.

[0069] The host computer device includes an FFT module, a time domain equalization processing module, a frequency domain equalization processing module, a polarization code decoding module, an in-well data analysis module, and an instruction generation module; the host computer device is used to perform OFDM demodulation on the OFDM sampling signal, and display and store the demodulated data; and is also used to send control instructions to the in-well telemetry equipment.

[0070] Based on the above system, the process of the ultra-long cable communication method in the well based on polarization coding in this embodiment is as follows: Figure 1 As shown, the specific steps include:

[0071] Step 1: Perform OFDM modulation on the original data in the well based on polarization coding: The polarization coding module uses the recursive construction of polarization code to encode the original data in the well received by the well data receiving module into a bit sequence based on the generator matrix G.

[0072] The generator matrix G is:

[0073]

[0074] in, represents the Kronecker power.

[0075] The generated bit sequence expression is:

[0076] x A =u A G (2)

[0077] Among them, x A is the bit sequence generated by the encoding, u A is the original information sequence, and A is a set of integer indicators.

[0078] Step 2: QAM mapping module for bit sequence x A Perform QAM (quadrature amplitude modulation) mapping by group to generate complex number s:

[0079]

[0080] in, and According to the bit sequence x A The real part mapping value and the imaginary part mapping value obtained by the sequence values ​​of the front and back parts in each group, and the multiple complex numbers s generated constitute a complex number sequence S.

[0081] Step 3: Use the pilot insertion module to insert a pilot signal into the complex sequence S, and then transmit the complex sequence S with the pilot signal as input data to the IFFT module; the distribution mode of the pilot signal is as follows: Figure 6 The comb-shaped distribution shown in FIG. Each row means the signal carried by a subcarrier of a specific frequency, and each column means the signal carried by all subcarriers at the same time. The black one is the pilot signal, and the white one is the data signal.

[0082] Step 4: The IFFT module performs IFFT (inverse fast Fourier transform) processing on the complex sequence S with the pilot signal to obtain the OFDM signal X(n):

[0083]

[0084] Among them, s k represents the kth complex number in the complex sequence S, k is the sequence number of the complex sequence, N is the total number of subcarriers, n is the subcarrier number, and j represents the imaginary unit.

[0085] Step 4: The DAC control module performs digital-to-analog conversion on the OFDM signal X(n) to obtain an analog signal; the analog signal is transmitted to the ground communication equipment through the communication cable in the well, and the ADC data acquisition module acquires the OFDM sampling signal.

[0086] Step 5: Demodulate the OFDM sampling signal: The OFDM sampling signal is processed by fast Fourier transform through the FFT module to obtain the received complex sequence; the received complex sequence is then processed by the time domain equalization module and the frequency domain equalization module in sequence, and the received complex sequence is processed by time domain equalization and frequency domain equalization in combination with the pilot signal to reduce noise and restore the signal phase and amplitude; the QAM demapping module is used to perform QAM demapping on the equalized complex sequence to obtain the bit sequence y i .

[0087] The polar code decoding module decodes the bit sequence y i Polar code decoding: According to the serial cancellation decoding algorithm, the bit sequence y i The likelihood ratio is expressed as:

[0088]

[0089] Among them, W(y i∣0) and W(y i |1) represents the channel transition probability when the input is 0 and 1 respectively.

[0090] Set decoding data The judgment criteria are:

[0091]

[0092] in, Represents the estimation of the source bits of level 1 to i-1; based on the decision criterion, the bit sequence y i Make a decision and get the decoded data

[0093] Step 6: The well data analysis module decodes the data The well parameter information is extracted and displayed on the host computer after parsing according to the preset data frame format; at the same time, the well parameter information is stored in the host computer and a data file is generated for subsequent reading.

[0094] The polarization coding used in the present invention is suitable for the high-speed data transmission system in the well, especially when the data transmission rate is high, and its encoding and decoding mechanism can be used to reduce the bit error rate. In the well cable communication environment with large noise and interference, polarization coding can allocate information bits to reliable channels through its polarization characteristics, thereby improving the anti-interference ability.

[0095] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for ultra-long cable communication in a well based on polarization coding, comprising the following steps: Step 1: Perform OFDM modulation on the original data in the well based on polarization coding: Using the recursive construction of polarization code, the original data in the well is encoded into a bit sequence based on the generator matrix G; The generator matrix G is: in, represents the Kronecker power; The generated bit sequence expression is: x A =u A G (2) Among them, x A is the bit sequence generated by the encoding, u A is the original information sequence, A is the set of integer indicators; For bit sequence x A Perform QAM mapping by group to generate complex number s: in, and According to the bit sequence x A The real part mapping value and the imaginary part mapping value obtained by the sequence values ​​of the front and back parts of each group, and the multiple complex numbers s generated form a complex number sequence S; Then the complex sequence S is used as input data for IFFT processing to obtain the OFDM signal X(n): Among them, s k represents the kth complex number in the complex sequence S, k is the sequence number of the complex sequence, N is the total number of subcarriers, n is the subcarrier number, and j represents the imaginary unit; Step 2: Perform digital-to-analog conversion on the obtained OFDM signal X(n) to obtain an analog signal; transmit the analog signal to the ground communication equipment through the communication cable in the well, and collect the OFDM sampling signal; Step 3: Demodulate the OFDM sampling signal and decode the demodulated data The data is displayed and stored according to the preset data frame format to complete the collection and storage of well data.

2. The method for ultra-long cable communication in a well based on polarization coding according to claim 1, characterized in that: In step 1, a pilot signal is inserted into the complex sequence S, and then the complex sequence S with the pilot sequence is used as input data for IFFT processing.

3. The method for ultra-long cable communication in a well based on polarization coding as claimed in claim 2, characterized in that: In step 1, the distribution mode of the pilot signal is a comb-shaped distribution.

4. The method for ultra-long cable communication in a well based on polarization coding as claimed in claim 3, characterized in that: In step 3, the step of demodulating the OFDM sampled signal includes: S32. The OFDM sampling signal is processed by FFT to obtain a received complex sequence; the received complex sequence is subjected to time domain equalization and frequency domain equalization in combination with the pilot signal; the equalized complex sequence is subjected to QAM demapping to obtain a bit sequence y i ; S33. Bit sequence y i Polar code decoding: According to the serial cancellation decoding algorithm, the bit sequence y i The likelihood ratio is expressed as: Among them, W(y i ∣0) and W(y i |1) represents the channel transition probability when the input is 0 and 1 respectively; Set decoding data The judgment criteria are: in, Represents the estimation of the source bits of level 1 to i-1; based on the decision criterion, the bit sequence y i Make a decision and get the decoded data 5. The method for ultra-long cable communication in a well based on polarization coding as claimed in claim 4, characterized in that: In step 3, the decoded data obtained by demodulation is The well parameter information is extracted and displayed on the host computer after parsing according to the preset data frame format; at the same time, the well parameter information is stored in the host computer and a data file is generated for subsequent reading.

6. The method for ultra-long cable communication in a well based on polarization coding according to any one of claims 1 to 5, characterized in that: A system for implementing the ultra-long cable communication method in a well based on polarization coding comprises a well telemetry device, a ground communication device and a host computer, wherein the well telemetry device and the ground communication device are interconnected via a well communication cable, and the ground communication device and the host computer are interconnected via an Ethernet interface; The well telemetry device is used to control the working mode of the well equipment according to the received control instructions, complete the acquisition of raw data in the well, perform OFDM modulation on the raw data in the well based on polarization coding, and finally send the modulated OFDM signal to the ground communication equipment through the well communication cable; The ground communication device is used to collect the OFDM signal sent by the telemetry device in the well, and send the collected OFDM sampling signal to the host computer; it is also used to transmit the command sent by the host computer to the telemetry device in the well; The host computer device is used to perform OFDM demodulation on the OFDM sampling signal, and to display and store the demodulated data; and is also used to send control instructions to the remote transmission device in the well.

7. The method for ultra-long cable communication in a well based on polarization coding according to claim 6, characterized in that: The well telemetry equipment realizes control command reception and analysis, data collection encoding and modulation, and control of well equipment working mode through the well telemetry FPGA chip; specifically, the well telemetry FPGA chip includes a command reception module, a modulation module, and an equipment control module; The instruction receiving module is used to receive and analyze the control instructions from the host computer device, and send the analyzed control instructions to the device control module; The equipment control module is used to control the working mode of the equipment in the well according to the received control instructions to complete the collection of raw data in the well; The modulation module performs OFDM modulation on the original data in the well based on polarization coding, obtains the modulated OFDM signal and transmits it to the ground communication equipment through the communication cable in the well.

8. The method for ultra-long cable communication in a well based on polarization coding as claimed in claim 7, characterized in that: The ground communication equipment comprises a power supply module and a communication module; The power supply module uses AC-DC-AC mode to supply power to the remote transmission equipment in the well; The communication module is used to realize data transmission between the host computer device and the well telemetry device; the communication module uses an Ethernet interface to connect to the host computer device, uses an ADC data acquisition module to collect OFDM signals uploaded by the well telemetry device, and uses a UART serial port protocol to transmit control instructions to the well telemetry device.

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