A logic control method for integrating underwater acoustic modem communication and positioning

Abstract

This invention discloses a logic control method for integrated underwater acoustic modem communication and positioning. The main control module of the transmitting underwater acoustic modem reads data from the positioning module, packages it, and sequentially passes it along with data packets through the communication module, power amplifier, and transducer, converting it into an underwater acoustic signal before outputting it. The receiving underwater acoustic modem receives the underwater acoustic signal through a hydrophone array, passes it through an analog-to-digital converter, and inputs it to the communication module. The waveform undergoes preliminary demodulation and verification before being sent to the main control module. The main control module sends positioning-related data to the positioning module and communication-related data to the communication module, obtaining communication data output. The positioning module obtains the relative position data between the transmitting and receiving underwater acoustic modes and outputs it as positioning data. This invention achieves positioning functionality during underwater acoustic communication and avoids conflicts between communication and positioning functions, realizing integrated underwater acoustic modem communication and positioning.

Description

Technical Field

[0001] This invention relates to the fields of underwater communication and underwater acoustic positioning, and in particular to a logic control method for integrated underwater acoustic modem communication and positioning. Background Technology

[0002] With the introduction of the national maritime power strategy and the concept of the marine Internet of Things (IoT), people have gradually increased their efforts in developing underwater electronic equipment. Various underwater IoT devices, unmanned underwater vehicles, and underwater sensors have been developed, promoting the observation and use of the marine environment. The emergence of these technologies and devices has enabled people to explore the ocean more deeply, helping marine observation and information transmission to develop in a direction of large-scale, automated, and efficient operation.

[0003] The widespread use of various underwater devices has further increased the frequency and requirements for the use of underwater acoustic modems. For underwater equipment, because common short-wave electromagnetic signals attenuate too quickly in water, long-wave underwater sound waves are mostly chosen for data and information transmission. The increased use of underwater acoustic modems has promoted the development of underwater acoustic communication systems, which have become a hot research topic. Underwater acoustic modems are the primary application form of most underwater acoustic communication systems, generally used in marine monitoring, remote control and telemetry of various underwater platform equipment, etc.

[0004] In underwater equipment, common underwater acoustic positioning or underwater acoustic communication functions are independent processes. This is because underwater sound waves have a slower propagation speed compared to electromagnetic waves. Long-distance underwater acoustic communication and positioning require a long time. If the positioning and measurement of underwater equipment are to be performed at fixed intervals, it can easily lead to conflicts and interference between the positioning and communication functions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a logic control method that integrates underwater acoustic modem communication and positioning.

[0006] The specific technical solution is as follows:

[0007] A logic control method integrating underwater acoustic modem communication and positioning is implemented through a transmitting underwater acoustic modem and a receiving underwater acoustic modem. The transmitting underwater acoustic modem includes: a main control module, a positioning module, a communication module, a power amplifier, an analog-to-digital converter, and a transducer; the receiving underwater acoustic modem includes: a main control module, a positioning module, a communication module, a power amplifier, an analog-to-digital converter, and a hydrophone array.

[0008] The main control module of the transmitting underwater acoustic modem reads the attitude data and timestamp data from the positioning module, packages them into frame header data, and inputs them together with the data packet data into the communication module for modulation; the modulated data is then converted into underwater acoustic signals by the power amplifier and transducer and sent to the receiving underwater acoustic modem.

[0009] The receiving underwater acoustic modem receives underwater acoustic signals through a hydrophone array. After processing by an analog-to-digital converter, the signals are input to the communication module. The arrival of the waveform is detected, and the waveform is initially demodulated and verified. After successful verification, the communication module sends the demodulated data to the main control module. The main control module sends positioning-related data to the positioning module and communication-related data to the communication module in bit order. The communication module demodulates the communication data to obtain the communication data output. The positioning module combines the attitude data and timestamp data of the receiving underwater acoustic modem to obtain the relative position data between the transmitting and receiving underwater acoustic modems and outputs it as positioning data. The relative position data includes distance data and azimuth data. The positioning module obtains the distance data between the transmitting and receiving underwater acoustic modems based on the timestamp difference and underwater acoustic velocity. The receiving underwater acoustic modem estimates the direction using a frequency domain beamforming method to obtain the azimuth data of the transmitting underwater acoustic modem.

[0010] Furthermore, the attitude data is acquired by a motion sensor, and the timestamp data is acquired by an atomic clock.

[0011] Furthermore, the frequency domain beamforming method is specifically as follows:

[0012] The underwater acoustic signal processed by the analog-to-digital converter is bandpass filtered; then Fourier transform is performed to convert it to the frequency domain, and frequency domain search is performed to obtain the frequency peak of the bandwidth signal; using narrowband beamforming, azimuth angle search is performed at the corresponding frequency to obtain the azimuth angle corresponding to the energy peak.

[0013] Multiplying the searched multi-frequency domain signals by the array manifold yields a two-dimensional spatial spectrum; the expression for the array manifold is as follows:

[0014]

[0015] In the formula, r is the array radius, f is the signal frequency in the search range, θ is the elevation angle, Φ is the azimuth angle in the search range, n=0…N-1, N is the number of array elements, c is the speed of sound, and j is the imaginary number.

[0016] The obtained two-dimensional spatial spectrum is summed in the frequency dimension to obtain a one-dimensional azimuth spatial spectrum. In the one-dimensional azimuth spatial spectrum, the index of the maximum value corresponding to the spectral peak is found, which is the target azimuth, thus obtaining the azimuth data.

[0017] Furthermore, the receiving underwater acoustic modem copies the communication data and positioning data into two copies, outputs one copy, and packages the other copy into an ACK frame and sends it to the sending underwater acoustic modem. If the sending underwater acoustic modem detects that the transmission was unsuccessful, it starts retransmission.

[0018] Furthermore, the header of the data frame of the underwater acoustic signal transmitted from the transmitting underwater acoustic modem to the receiving underwater acoustic modem contains bit data and a checksum packaged into bytes; the communication-related data in the bit data includes: frame type, signal-to-noise ratio data, transmitting node address, receiving node address, frame number, modulation method, number of data packets, and data type; the positioning-related data in the bit data includes: timestamp data, vector velocity data, depth data, and angle data.

[0019] Furthermore, the header of the ACK frame transmitted from the receiving underwater acoustic modem to the transmitting underwater acoustic modem contains bit data and a checksum packaged into bytes; the communication-related data in the bit data includes: frame type, signal-to-noise ratio data, sending node address, receiving node address, and data packet correctness information; the positioning-related data in the bit data includes: longitude data, latitude data, and depth data.

[0020] Furthermore, during transmission, the underwater acoustic modem first sends a frame header using incoherent modulation, and then sends subsequent data packets using coherent modulation.

[0021] The beneficial effects of this invention are:

[0022] This invention achieves the goal of realizing positioning function in underwater acoustic communication by adding positioning data to the necessary communication frame header, and realizing DOA estimation at the receiving end of the underwater acoustic modem through frequency domain beamforming. This avoids the conflict between positioning function and communication function and realizes the integration of underwater acoustic modem communication and positioning. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the underwater acoustic modem used in this invention.

[0024] Figure 2 This is a flowchart of the underwater acoustic modem transmission function of the transmitting end of the present invention.

[0025] Figure 3 This is a flowchart of the underwater acoustic modem receiving function of the receiving end of the present invention.

[0026] Figure 4 This is a flowchart of the method for obtaining the relative position data of the transmitting and receiving underwater acoustic modems according to the present invention. Detailed Implementation

[0027] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The objectives and effects of the present invention will become clearer as a result. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] like Figure 1 As shown, this invention is applicable to a communication system consisting of at least two underwater acoustic modems. The underwater acoustic modem includes: a main control module, a positioning module, a communication module, a power amplifier, an analog-to-digital converter, a motion sensor, an atomic clock, a transducer, and a hydrophone array. The positioning module and the communication module constitute the computing module. In this communication system, at least one underwater acoustic modem is equipped with a hydrophone array as a receiver to determine the direction of the underwater acoustic signal; the other underwater acoustic modem can act as a transmitter.

[0029] After normal power-on, the main control module controls the power supply of each hardware component, performs various function configurations and power-on self-tests. After the computing module powers on, it sends a power-on signal to the control module. After receiving the power-on signal, the control module confirms that the power-on configuration of each part is normal, and then enters the normal working mode.

[0030] During transmission, the underwater acoustic modem will first send a frame header using incoherent modulation, and then send subsequent data packets using coherent modulation.

[0031] like Figure 2 As shown, when data needs to be transmitted, the host computer sends a command to the main control module of the transmitting underwater acoustic modem. The main control module queries and reads the current vector velocity, depth, angle, timestamp, and other data from the positioning module, and packages them into frame header data. The vector velocity, depth, and angle data of the positioning module are read from the attitude data of the motion sensor, and the timestamp data is read from the atomic clock's own timestamp data. The frame header data and the data packet data are modulated together by the communication module, with the frame header data undergoing incoherent modulation and the data packet data undergoing coherent modulation. The modulated frame header data and data packet data are then converted into underwater acoustic signals by a power amplifier and a transducer, and transmitted to the receiving underwater acoustic modem.

[0032] The header of the data frame transmitting the underwater acoustic signal from the transmitting underwater acoustic modem to the receiving underwater acoustic modem contains bit data and a checksum packaged into bytes. The communication-related data in the bit data includes: frame type, signal-to-noise ratio data, transmitting node address, receiving node address, frame number, modulation scheme, number of data packets, and data type. The positioning-related data in the bit data includes: timestamp data, vector velocity data, depth data, and angle data.

[0033] like Figure 3 As shown, when receiving underwater acoustic data, the receiving underwater acoustic modem listens to the underwater acoustic signal in real time through a hydrophone array. After the underwater acoustic signal passes through an analog-to-digital converter, it is input into the communication module in the computing module. The communication module is used to detect the arrival of the waveform and perform preliminary demodulation and verification of the waveform. When the verification is successful, the communication module sends the non-coherently demodulated frame header data to the main control module. After receiving the frame header data, the main control module sends the positioning-related data in the frame header to the positioning module according to the bit order, and at the same time sends the communication-related data to the communication module. The communication module performs normal communication data demodulation. The positioning module obtains the attitude data from the motion sensor and its own timestamp data from the atomic clock. Combined with the transmitter's attitude, velocity, and time data in the frame header positioning data, and based on the beamforming positioning principle, it calculates the relative position data between the transmitting underwater acoustic modem and the receiving underwater acoustic modem (hereinafter referred to as the two devices).

[0034] like Figure 4 As shown, the relative position data includes distance data and azimuth data. The positioning module calculates the distance difference between the transmitting and receiving underwater acoustic modems (i.e., the distance difference between the two devices) based on the difference in timestamps and the underwater acoustic velocity, thus obtaining the distance data. The receiving underwater acoustic modem estimates its direction using frequency domain beamforming to obtain the azimuth data of the transmitting underwater acoustic modem. The frequency domain beamforming method is as follows:

[0035] The multi-channel underwater acoustic signals processed by the analog-to-digital converter are bandpass filtered; then Fourier transform is performed to convert them to the frequency domain, and frequency domain search is performed to obtain the frequency peak of the bandwidth signal; using narrowband beamforming, azimuth angle search is performed at the corresponding frequency to obtain the azimuth angle corresponding to the energy peak, wherein the search azimuth angle is in 0.1° intervals from 0 to 360°.

[0036] Multiplying the searched multi-frequency domain signals by the array manifold yields the two-dimensional spatial spectrum. The expression for the array manifold is as follows:

[0037]

[0038] In the formula, r is the array radius, f is the signal frequency within the search range, θ is the elevation angle, Φ is the azimuth angle within the search range, n = 0…N-1, N is the number of array elements, and c is the speed of sound. j is an imaginary number.

[0039] The obtained two-dimensional spatial spectrum is summed in the frequency dimension to obtain a one-dimensional azimuth spatial spectrum. In the one-dimensional azimuth spatial spectrum, the index of the maximum value corresponding to the spectral peak is found, which is the target azimuth, thus obtaining the azimuth data.

[0040] Meanwhile, the underwater acoustic modem uses the timestamp data of the transmission time and the timestamp data of the reception time to obtain the time difference of underwater acoustic propagation between the two devices. Using the current underwater acoustic velocity, the distance between the two devices can be obtained.

[0041] By combining distance data with azimuth data, the specific coordinates of the transmitting underwater acoustic modem are calculated, and the corresponding geographical coordinates are obtained after coordinate transformation.

[0042] The receiving underwater acoustic modem copies the communication and positioning data into two copies. One copy is sent by the positioning module to the host computer, containing positioning data including relative position data, and the other copy is sent by the communication module to the host computer after demodulation. The receiving underwater acoustic modem packages the data into an ACK frame and sends it to the transmitting underwater acoustic modem in a non-coherent modulation manner. After receiving the returned ACK frame, the transmitting underwater acoustic modem parses the data to obtain the relative position of the two devices and the data packet transmission result. If any data packets are not successfully transmitted, retransmission is performed.

[0043] The header of the ACK frame transmitted from the receiving underwater acoustic modem to the transmitting underwater acoustic modem contains bit data and a checksum packaged into bytes. The communication-related data in the bit data includes: frame type, signal-to-noise ratio data, transmitting node address, receiving node address, and data packet correctness information. The location-related data in the bit data includes: longitude data, latitude data, and depth data.

[0044] It will be understood by those skilled in the art that the above descriptions are merely preferred examples of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or make equivalent substitutions for some of the technical features. All modifications and equivalent substitutions made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A logic control method integrating underwater acoustic modem communication and positioning, characterized in that, This is achieved through a transmitting underwater acoustic modem and a receiving underwater acoustic modem. The transmitting underwater acoustic modem includes: a main control module, a positioning module, a communication module, a power amplifier, an analog-to-digital converter, and a transducer. The receiving underwater acoustic modem includes: a main control module, a positioning module, a communication module, a power amplifier, an analog-to-digital converter, and a hydrophone array. The main control module of the transmitting underwater acoustic modem reads the attitude data and timestamp data from the positioning module, packages them into frame header data, and inputs them together with the data packet data into the communication module for modulation; the modulated data is then converted into underwater acoustic signals by the power amplifier and transducer and sent to the receiving underwater acoustic modem. The receiving underwater acoustic modem receives underwater acoustic signals through a hydrophone array. After processing by an analog-to-digital converter, the signals are input to the communication module. The module detects the arrival of the waveform and performs preliminary demodulation and verification. After successful verification, the communication module sends the demodulated data to the main control module. The main control module sends positioning-related data to the positioning module and communication-related data to the communication module in bit order. The communication module demodulates the communication data to obtain the communication data output. The positioning module combines the attitude data and timestamp data of the receiving underwater acoustic modem to obtain the relative position data between the transmitting and receiving underwater acoustic modems and outputs it as positioning data. The relative position data includes distance data and azimuth data. The positioning module obtains the distance data between the transmitting and receiving underwater acoustic modems based on the timestamp difference and underwater acoustic velocity. The receiving underwater acoustic modem estimates the direction using a frequency domain beamforming method to obtain the azimuth data of the transmitting underwater acoustic modem. The frequency domain beamforming method is as follows: The underwater acoustic signal processed by the analog-to-digital converter is bandpass filtered; then Fourier transform is performed to convert it to the frequency domain, and frequency domain search is performed to obtain the frequency peak of the bandwidth signal; using narrowband beamforming, azimuth angle search is performed at the corresponding frequency to obtain the azimuth angle corresponding to the energy peak. Multiplying the searched multi-frequency domain signals by the array manifold yields a two-dimensional spatial spectrum; the expression for the array manifold is as follows: ； In the formula, r is the array radius, f is the signal frequency in the search range, θ is the elevation angle, Φ is the azimuth angle in the search range, n=0,1,2,…,N-1, N is the number of array elements, c is the speed of sound, and j is the imaginary number. The obtained two-dimensional spatial spectrum is summed in the frequency dimension to obtain a one-dimensional azimuth spatial spectrum. In the one-dimensional azimuth spatial spectrum, the index of the maximum value corresponding to the spectral peak is found, which is the target azimuth, thus obtaining the azimuth data.

2. The logic control method for integrated underwater acoustic modem communication and positioning according to claim 1, characterized in that, The attitude data is acquired by a motion sensor, and the timestamp data is acquired by an atomic clock.

3. The logic control method for integrated underwater acoustic modem communication and positioning according to claim 1, characterized in that, The receiving underwater acoustic modem copies the communication data and positioning data into two copies. One copy is output, and the other copy is packaged into an ACK frame and sent to the sending underwater acoustic modem. If the sending underwater acoustic modem detects that the transmission was unsuccessful, it starts retransmission.

4. The logic control method for integrated underwater acoustic modem communication and positioning according to claim 1, characterized in that, The header of the data frame of the underwater acoustic signal transmitted from the transmitting underwater acoustic modem to the receiving underwater acoustic modem contains bit data and a checksum packaged into bytes. The communication-related data in the bit data includes: frame type, signal-to-noise ratio data, transmitting node address, receiving node address, frame number, modulation method, number of data packets, and data type. The positioning-related data in the bit data includes: timestamp data, vector velocity data, depth data, and angle data.

5. The logic control method for integrated underwater acoustic modem communication and positioning according to claim 3, characterized in that, The header of the ACK frame transmitted from the receiving underwater acoustic modem to the transmitting underwater acoustic modem contains bit data and a checksum packaged into bytes. The communication-related data in the bit data includes: frame type, signal-to-noise ratio data, sending node address, receiving node address, and data packet correctness information; the positioning-related data in the bit data includes: longitude data, latitude data, and depth data.

6. The logic control method for integrated underwater acoustic modem communication and positioning according to claim 1, characterized in that, During transmission, the underwater acoustic modem first sends a frame header using incoherent modulation, and then sends subsequent data packets using coherent modulation.

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