A ultra-long cable communication system and method in a well based on polarization coding

Abstract

This invention discloses a communication system and method for ultra-long cables in wells based on polar coding, relating to the field of wired communication. The system includes a well-based remote transmission device, a ground communication device, and a host computer. The method first modulates the raw data in the well using OFDM based on polar coding; then, it performs digital-to-analog conversion on the modulated OFDM signal; next, it transmits the analog signal to the ground communication device to acquire the OFDM sampled signal; finally, it demodulates the OFDM sampled signal and displays and stores it according to a preset data frame format, completing the acquisition and storage of the well-based data. The polar coding used in this invention is suitable for high-speed data transmission in wells, especially when high data transmission rates are required. Its encoding and decoding mechanisms can reduce the bit error rate. In well-based cable communication environments with significant noise and interference, polar coding can allocate information bits to reliable channels through its polarization characteristics, thereby improving anti-interference capabilities.

Description

Technical Field

[0001] This invention relates to the field of wired communication, specifically to a communication system and method for ultra-long cables in wells based on polarization coding. Background Technology

[0002] Polar coding, with its high efficiency and reliability, can be applied to wired cable communication, especially under complex channel conditions and interference. Through channel modeling and optimization, polar coding can be effectively integrated into wired communication systems, improving their performance and reliability. In long-distance manhole cable communication, extremely narrow channels, signal attenuation, and noise interference significantly impact communication quality. Implementing polar coding in manhole cable communication, leveraging its near-Shannon limit, can improve channel fault tolerance, thereby enhancing signal transmission reliability.

[0003] With the ever-increasing demand for formation information, well logging systems have undergone a series of iterative upgrades, leading to a more diversified range of detection methods. Along with these improvements, many advanced well logging devices have adopted high-sampling-rate acquisition chips, resulting in a need for higher transmission throughput. Long-distance detection is a crucial indicator for well logging projects in my country. However, considering that my country's well logging radar systems need to operate in high-temperature, high-pressure environments at depths of 1000–6000 m, with wells filled with drilling mud, the extremely long communication distances and the changes in distributed parameters and resistance caused by the stretching of logging cables severely impact signal reliability. As the required logging depth continues to increase and the sampling rate of logging equipment gradually rises, greater throughput in well logging communication is required. This necessitates addressing issues arising from ultra-deep well exploration, with cable-related problems requiring priority consideration. Firstly, the long length of logging cables, coupled with the variable and noisy environment within the well, presents a significant challenge in practical engineering experiments, demanding long-distance communication and interference resistance capabilities from the system.

[0004] In my country, many well logging projects utilize mainstream seven-core armored cables. Each core consists of seven twisted copper wires, covered with an insulation layer, and then further covered with two layers of steel armor of different thicknesses wound in opposite directions. The total cable length exceeds seven kilometers. Well-drilled cables can be approximated as narrow-band, low-frequency communication channels; high-frequency signals can hardly pass through ultra-long well-drilled cables, resulting in communication speeds limited by signal bandwidth. Because the equipment operates deep underground, the system cannot troubleshoot problems in real time during logging operations, frequently leading to data reception failures and the inability to issue commands from the surface.

[0005] The basic idea of ​​polar coding is to combine multiple identical channels into a new set of channels through channel polarization, where 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, thus achieving reliable transmission close to the channel capacity. In well logging cable communication, polar codes are combined with OFDM (Orthogonal Frequency Division Multiplexing) to achieve efficient coding and modulation, allowing high-priority information bits to 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] Polar coding, based on the principle of channel polarization, classifies channels into reliable and unreliable categories, thus achieving a highly efficient coding scheme that approaches channel capacity. It has broad application prospects in modern communication systems, especially in 5G communication where it has been practically applied and validated. Therefore, polar coding is also one of the most promising methods in well logging communication engineering. In long-distance wired communication, signal attenuation and noise interference can significantly affect communication quality. Polar coding, through its near-Shannon limit characteristic, can improve the channel's fault tolerance, thereby enhancing the reliability of signal transmission. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a communication system and method for ultra-long cables in wells based on polarization coding, which solves the problems of low communication speed and low data reliability in current well logging projects.

[0008] The technical solution adopted in this invention is as follows:

[0009] In a first aspect, the present invention provides a method for communication via ultra-long cables in wells based on polarization coding, comprising the following steps:

[0010] Step 1: OFDM modulation of raw data from the well based on polar coding: Using the recursive construction of polar codes, the raw data from the well is encoded into a bit sequence based on the generator matrix G.

[0011] The generating matrix G is:

[0012]

[0013] in, It represents the power of Kronecker.

[0014] The generated bit sequence expression is:

[0015]

[0016] Where, xA For the bit sequence generated for encoding, u A Let A be the original information sequence and A be the set of integer indicators.

[0017] For bit sequence x A Perform QAM (Quadrature Amplitude Modulation) mapping on the groups to generate complex numbers s:

[0018]

[0019] in, and Based on the bit sequence x A The real part mapping value and imaginary part mapping value obtained from the sequence values ​​of the two parts in each group are used to generate multiple complex numbers s to form a complex number sequence S.

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

[0021]

[0022] Among them, s k Let represent the k-th complex number in the complex sequence S, where 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: Convert the obtained OFDM signal X(n) from digital to analog to obtain an analog signal; transmit the analog signal to the ground communication equipment through the communication cable in the well to obtain the OFDM sampling signal.

[0024] Step 3: Demodulate the OFDM sampled signal and decode the obtained data. The data is displayed and stored according to the preset data frame format, thus completing the acquisition and storage of well data.

[0025] Further, in step 1, a pilot signal is inserted into the complex sequence S, and then the complex sequence S with the pilot signal 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 sub-channel fading and synchronization error.

[0026] Furthermore, the pilot signal has a comb-like distribution pattern.

[0027] Furthermore, step 3, the demodulation step of the OFDM sampled signal, includes:

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

[0029] S33. For 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:

[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 criteria for judgment are:

[0033]

[0034] in, This represents the estimation of source bits from level 1 to i-1; based on the decision criterion, the bit sequence y... i Make a judgment and obtain the decoded data.

[0035] Furthermore, in step 3, the decoded data... The data frame is parsed according to the preset data frame format, and the well parameters are extracted and displayed on the host computer. At the same time, the well parameters are stored on the host computer to generate a data file for later reading.

[0036] Secondly, the present invention provides a communication system for ultra-long cables in wells based on polarization coding, including a remote transmission device in the well, a ground communication device and a host computer, wherein the remote transmission device in the well and the ground communication device are interconnected through a communication cable in the well, and the ground communication device and the host computer are interconnected through an Ethernet interface.

[0037] The in-well remote transmission device is used to control the working mode of the in-well equipment according to the received control commands, 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 in-well communication cable.

[0038] The ground communication equipment is used to collect OFDM signals sent by the in-well remote transmission equipment and send the collected OFDM sampling signals to the host computer; it is also used to transmit the instructions sent by the host computer to the in-well remote transmission equipment.

[0039] The host computer device is used to demodulate the OFDM sampled signal using OFDM, and to display and store the demodulated data; it is also used to send control commands to the remote transmission device in the well.

[0040] Furthermore, the in-well telemetry device utilizes an in-well telemetry FPGA chip to receive and parse control commands, encode and modulate acquired data, and control the operating mode of the in-well device. Specifically, the in-well telemetry FPGA chip includes a command receiving module, a modulation module, and a device control module.

[0041] The instruction receiving module is used to receive and parse control instructions from the host computer device, and send the parsed 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 commands, and to complete the acquisition of raw data in the well.

[0043] The modulation module performs OFDM modulation on the raw data in the well based on polarization coding, and the modulated OFDM signal is transmitted 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 uses an AC-DC-AC method to power the remote transmission equipment in the well. Since the ultra-long cable has a capacitive effect, using AC-DC-AC 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 underground remote transmission device. The communication module is connected to the host computer device through an Ethernet interface, acquires the OFDM signal uploaded by the underground remote transmission device through an ADC data acquisition module, and transmits control commands to the underground remote transmission device through a UART serial port protocol.

[0047] The beneficial effects of this invention are as follows:

[0048] 1. The application of polar codes in wired communication is mainly reflected in their efficient encoding and decoding capabilities. For wired communication systems such as cable communication in wells, polar codes can provide a stable encoding scheme, giving data high robustness and anti-interference ability during transmission.

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

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

[0051] 4. Polar codes can achieve efficient encoding under extremely limited bandwidth conditions in cable channels in wells, enabling high data transmission speeds even under extremely narrow bandwidth conditions. This avoids the situation where traditional encoding 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 polar codes enable them to maintain a high data transmission rate even in environments with high frequency attenuation and noise interference in well cables. Attached Figure Description

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

[0054] Figure 2 Overall collaborative principle diagram of the system of this invention;

[0055] Figure 3 The FPGA internal logic block diagram of the well-ground remote transmission device of this 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 this invention;

[0058] Figure 6 A schematic diagram of the distributed training sequence used in this invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of protection of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The present invention will be further described below with reference to the accompanying drawings.

[0060] This embodiment provides a method and system for communication over ultra-long cables in wells based on polarization coding, used for deep well exploration operations, as detailed below:

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

[0062] The underground remote transmission device, such as Figure 3 The diagram illustrates how a remote transmission FPGA chip in a well is used to receive and parse control commands, encode and modulate acquired data, and control the operating mode of the equipment within the well. Specifically, the remote transmission FPGA chip includes a command receiving module, a modulation module, and a device control module.

[0063] The instruction receiving module is used to receive and parse control instructions from the host computer device, and send the parsed 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 commands, and to complete the acquisition of raw data in the well.

[0065] The modulation module is used to perform OFDM modulation on the raw data from the wellbore based on polarization coding, and to transmit the modulated OFDM signal to the surface communication equipment via the wellbore communication cable. The modulation module includes a wellbore 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 uses an AC-DC-AC method to power the remote transmission equipment and communication module in the well. Since the ultra-long cable has a capacitive effect, using AC-DC-AC 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 underground remote transmission device. The communication module is connected to the host computer device through an Ethernet interface, acquires the OFDM signal uploaded by the underground remote transmission device through an ADC data acquisition module, and transmits control commands to the underground remote transmission device through a UART serial port protocol.

[0069] The host computer device includes an FFT module, a time-domain equalization processing module, a frequency-domain equalization processing module, a polar code decoding module, a well data parsing module, and an instruction generation module. The host computer device is used to perform OFDM demodulation on the OFDM sampled signal, and to display and store the demodulated data. It is also used to send control instructions to the well remote transmission device.

[0070] Based on the above system, the flowchart 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: OFDM modulation of raw well data based on polar coding: The polar coding module uses the recursive construction of polar codes to encode the raw well data received by the well data receiving module into a bit sequence based on the generator matrix G.

[0072] The generating matrix G is:

[0073]

[0074] in, It represents the power of Kronecker.

[0075] The generated bit sequence expression is:

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

[0077] Where, x A For the bit sequence generated for encoding, u A Let A be the original information sequence and A be the set of integer indicators.

[0078] Step 2: The QAM mapping module maps the bit sequence x A Perform QAM (Quadrature Amplitude Modulation) mapping on the groups to generate complex numbers s:

[0079]

[0080] in, and Based on the bit sequence x A The real part mapping value and imaginary part mapping value obtained from the sequence values ​​of the two parts in each group are used to generate multiple complex numbers s to form a complex number sequence S.

[0081] Step 3: Insert pilot signals into the complex sequence S using the pilot insertion module, and then transmit the complex sequence S containing the pilot signals as input data to the IFFT module; the distribution pattern of the pilot signals is as follows: Figure 6 The diagram shows a comb-like distribution. Each row represents the signal carried by a subcarrier at a specific frequency, and each column represents the signals carried by all subcarriers at the same time. Black represents pilot signals, and white represents data signals.

[0082] Step 4: The IFFT module performs IFFT (Inverse Fast Fourier Transform) processing on the complex sequence S with pilot signals to obtain the OFDM signal X(n):

[0083]

[0084] Among them, s k Let represent the k-th complex number in the complex sequence S, where 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 converts the OFDM signal X(n) into an analog signal; the analog signal is transmitted to the ground communication equipment via the communication cable in the well, and the ADC data acquisition module acquires the OFDM sampling signal.

[0086] Step 5: Demodulate the OFDM sampled signal: The OFDM sampled signal undergoes Fast Fourier Transform (FFT) processing through an FFT module to obtain the received complex sequence. The received complex sequence then passes through a time-domain equalization module and a frequency-domain equalization module, incorporating pilot signals to perform time-domain and frequency-domain equalization to reduce noise and restore signal phase and amplitude. Finally, the equalized complex sequence is demapped using a QAM demapping module to obtain the bit sequence y. i .

[0087] The bit sequence y is decoded using the polar code decoding module. 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 criteria for judgment are:

[0091]

[0092] in, This represents the estimation of source bits from level 1 to i-1; based on the decision criterion, the bit sequence y... i Make a judgment and obtain the decoded data.

[0093] Step 6: The well data parsing module will decode the data. The data frame is parsed according to the preset data frame format, and the well parameters are extracted and displayed on the host computer. At the same time, the well parameters are stored on the host computer to generate a data file for later reading.

[0094] The polar coding employed in this invention is suitable for high-speed data transmission systems in wells, especially when high data transmission rates are required. Its encoding and decoding mechanisms can reduce the bit error rate. In well-drilled cable communication environments with significant noise and interference, polar coding can allocate information bits to reliable channels through its polarization characteristics, thereby improving anti-interference capabilities.

[0095] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for communication via ultra-long cables in wells based on polar coding, comprising the following steps: Step 1: OFDM modulation of raw well data based on polar coding: Using the recursive construction of polar codes, the raw well data is encoded into a bit sequence based on the generator matrix G; The generating matrix G is: in, Indicates Kronecker exponentiation; The generated bit sequence expression is: x A =u A G (2) Where, x A For the bit sequence generated for encoding, u A Let A be the original information sequence, and A be the set of integer indicators. For bit sequence x A Perform QAM mapping by group to generate complex number s: in, and Based on the bit sequence x A The real part mapping value and imaginary part mapping value obtained from the sequence values ​​of the two parts in each group are used to generate multiple complex numbers s to form a complex number sequence S; Then, the complex sequence S is used as input data and processed by IFFT to obtain the OFDM signal X(n): Among them, s k Let represent the k-th complex number in the complex sequence S, where 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: Convert the obtained OFDM signal X(n) from digital to analog to obtain an analog signal; transmit the analog signal to the ground communication equipment via the communication cable in the well to collect the OFDM sampling signal; Step 3: Demodulate the OFDM sampled signal and decode the obtained data. The data is displayed and stored according to the preset data frame format, thus completing the acquisition and storage of well data.

2. The method for communication of ultra-long cables in wells based on polarization coding as described in 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 signal is used as input data for IFFT processing.

3. The method for communication of ultra-long cables in wells based on polarization coding as described in claim 2, characterized in that, In step 1, the pilot signal is distributed in a comb-like pattern.

4. The method for communication of ultra-long cables in wells based on polarization coding as described in claim 3, characterized in that, Step 3, the demodulation steps for the OFDM sampled signal, include: S32. Process the OFDM sampled signal using FFT to obtain the received complex sequence; perform time-domain equalization and frequency-domain equalization on the received complex sequence in conjunction with the pilot signal; perform QAM demapping on the equalized complex sequence to obtain the bit sequence y. i ; S33. For 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: Among them, W(y) i |0) and W(y) i |1) represents the channel transition probabilities when the input is 0 and 1, respectively; Set decoding data The criteria for judgment are: in, This represents the estimation of source bits from level 1 to i-1; based on the decision criterion, the bit sequence y... i Make a judgment and obtain the decoded data.

5. The method for communication of ultra-long cables in wells based on polarization coding as described in claim 4, characterized in that, In step 3, the demodulated data is... The data frame is parsed according to the preset data frame format, and the well parameters are extracted and displayed on the host computer. At the same time, the well parameters are stored on the host computer to generate a data file for later reading.

6. A method for communication over ultra-long cables in wells based on polarization coding as described in any one of claims 1-5, characterized in that, The system for implementing the polar coding-based long cable communication method in a well includes a remote transmission device in the well, a ground communication device, and a host computer. The remote transmission device in the well and the ground communication device are interconnected via a communication cable in the well, and the ground communication device and the host computer are interconnected via an Ethernet interface. The in-well remote transmission device is used to control the working mode of the in-well device according to the received control command, 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 device through the in-well communication cable. The ground communication equipment is used to collect OFDM signals sent by the in-well remote transmission equipment and send the collected OFDM sampling signals to the host computer; it is also used to transmit the instructions sent by the host computer to the in-well remote transmission equipment. The host computer device is used to demodulate the OFDM sampled signal using OFDM, and to display and store the demodulated data; it is also used to send control commands to the remote transmission device in the well.

7. The method for communication of ultra-long cables in wells based on polarization coding as described in claim 6, characterized in that, The in-well telemetry device uses an in-well telemetry FPGA chip to receive and parse control commands, encode and modulate acquired data, and control the working mode of the in-well device. Specifically, the in-well telemetry FPGA chip includes a command receiving module, a modulation module, and a device control module. The instruction receiving module is used to receive and parse control instructions from the host computer device, and send the parsed 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 commands, and to complete the acquisition of raw data in the well; The modulation module performs OFDM modulation on the raw data in the well based on polarization coding, and the modulated OFDM signal is transmitted to the ground communication equipment through the communication cable in the well.

8. The method for communication of ultra-long cables in wells based on polarization coding as described in claim 7, characterized in that, The ground communication equipment includes a power supply module and a communication module; The power supply module uses an AC-DC-AC method to power the remote transmission equipment in the well. The communication module is used to realize data transmission between the host computer device and the underground remote transmission device. The communication module is connected to the host computer device through an Ethernet interface, acquires the OFDM signal uploaded by the underground remote transmission device through an ADC data acquisition module, and transmits control commands to the underground remote transmission device through a UART serial port protocol.

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