An integrated transmission system based on acoustic duct and satellite

Abstract

The application is suitable for the technical field of ocean observation and underwater information transmission, and provides a comprehensive transmission system based on sound and satellite, which comprises a seabed observation node signal collection and processing module, a water sound FSK coding and low frequency transduction emission module, a sea surface buoy water sound receiving and demodulation module, a buoy end data scheduling and satellite packaging module, a satellite link transmission module, and a shore base receiving and analysis module. The application combines water sound communication and satellite communication, realizes the quasi-real-time and reliable return of deep sea observation data, supports remote instruction scheduling, and significantly improves the data timeliness and controllability of the ocean observation system.

Description

Technical Field

[0001] This invention belongs to the field of marine observation and underwater information transmission technology, and particularly relates to an integrated transmission system based on acoustic communication and satellite. Background Technology

[0002] With the rapid development of marine geophysical observation, marine environmental monitoring, and marine disaster early warning technologies, observation equipment such as seabed seismometers (OBS) and deep-sea moorings are widely deployed in deep-sea or offshore waters. These devices typically operate at depths of hundreds to thousands of meters, often unattended, and generate large amounts of data over long periods, placing high demands on the reliability, real-time performance, and engineering feasibility of data transmission.

[0003] Existing technologies for acquiring deep-sea observation data mainly include self-contained storage, single underwater acoustic communication, and single satellite communication. Self-contained storage stores data on a local medium, which is then retrieved after the equipment is recovered. While simple in structure, this method suffers from extremely poor data timeliness; data cannot be retrieved if the equipment malfunctions or is lost. Single underwater acoustic communication transmits data directly to a surface platform or shipborne receiving system via an underwater acoustic channel. However, due to the narrow bandwidth, strong multipath effect, and significant Doppler interference of the underwater acoustic channel, long-distance, high-reliability transmission faces significant challenges, and direct connection with shore-based systems is difficult to achieve. Single satellite communication is suitable for surface or near-surface equipment but cannot directly cover deep-sea environments, requiring relay nodes. Furthermore, satellite communication consumes a lot of power, which would severely limit the system's endurance if used directly for underwater equipment.

[0004] In practical engineering applications, relying solely on a single communication method often fails to simultaneously achieve long-distance transmission, low-power operation, system reliability, and data timeliness. Especially in application scenarios such as deep-sea moorings and OBS (Ocean Base System), achieving stable communication under complex underwater acoustic channel conditions and further efficiently integrating with satellite communication systems to form an end-to-end data loop is a pressing challenge that needs to be addressed in current technologies. Summary of the Invention

[0005] The purpose of this invention is to provide an integrated transmission system based on acoustic communication and satellite, which aims to solve the problems existing in the background art.

[0006] This invention is implemented as follows: a comprehensive transmission system based on acoustic communication and satellite, comprising:

[0007] The signal acquisition and processing module of the seabed observation node is used to digitize and initially simplify the underlying physical signals. The built-in sensor continuously acquires environmental or geophysical signals, converts them into discrete-time signal sequences through analog-to-digital conversion, executes event-triggered decisions, and extracts, compresses and encodes data with significant features to generate structured data frames.

[0008] The underwater acoustic FSK encoding and low-frequency transducer transmission module is used to convert the structured data frame into an acoustic signal suitable for underwater propagation. Based on the signal-to-noise ratio and frequency attenuation function of historical communication feedback, it dynamically selects the frequency that minimizes the cost function from the candidate carrier frequency set for FSK modulation, executes a symbol-level energy adaptive mechanism, assigns weight coefficients to different symbols according to data priority, and drives the low-frequency underwater acoustic transducer to convert the electrical signal into sound waves that radiate upward.

[0009] The underwater acoustic receiving and demodulation module for sea surface buoys is used to receive signals using a multi-element hydrophone array, select weight vectors for weighted synthesis using the least mean square criterion, suppress non-target direction noise, accumulate energy of each carrier frequency in the synthesized signal, and complete symbol decision and data verification based on the maximum energy criterion.

[0010] The buoy-end data scheduling and satellite encapsulation module is used to reassemble and prioritize fragmented unmodulated data from the underwater acoustic link, and reconstruct the data into satellite uplink data frames according to the transmission cycle and protocol format of the satellite link.

[0011] The satellite link transmission module is used to send the encapsulated satellite frames to the on-orbit satellite through the satellite terminal, realize long-distance wireless data relay between the buoy and the shore base, and listen to satellite commands in real time to receive remote scheduling and control commands issued by the shore base.

[0012] The shore-based receiving and parsing module is used to perform multi-layer protocol parsing on satellite downlink data, store it in a database for the monitoring platform to call, and generate working mode switching or parameter configuration instructions based on the analysis results, which are then sent to the buoy via the satellite backhaul link.

[0013] Furthermore, the underwater acoustic FSK coding and low-frequency transducer transmission module adopts an adaptive multi-frequency FSK coding mechanism, which dynamically adjusts the FSK carrier frequency set according to the channel estimation results to reduce the impact of frequency selective fading.

[0014] Furthermore, the underwater acoustic receiving and demodulation module of the sea surface buoy adopts the asymmetric frequency shift FSK demodulation method to make the positive and negative frequency offsets unequal, and introduces a Doppler compensation factor during demodulation to suppress frequency offset misjudgment caused by buoy movement.

[0015] Furthermore, the underwater acoustic receiving and demodulation module of the sea surface buoy obtains array gain through weighted synthesis of a multi-element hydrophone array, thereby improving the received signal-to-noise ratio and compensating for underwater acoustic channel loss.

[0016] Furthermore, the underwater acoustic FSK coding and low-frequency transducer transmission module introduces a symbol-level energy adaptive mechanism, which allocates different transmission energies to different symbols according to data importance or error sensitivity, so that key state information has a higher reception probability under the same channel conditions.

[0017] Furthermore, the shore-based receiving and parsing module generates working mode switching or parameter configuration commands based on the analysis results, sends them to the buoy via the satellite backhaul link, and then sends them to the seabed node via the underwater acoustic communication link, forming a complete two-way communication closed loop.

[0018] The integrated transmission system based on acoustic communication and satellite provided by this invention has the following beneficial effects:

[0019] This invention achieves long-distance, near-real-time transmission of deep-sea observation data by organically combining underwater acoustic communication and satellite communication, solving the problem of balancing data timeliness, transmission distance, power consumption, and reliability inherent in traditional single communication methods. The invention employs an adaptive multi-frequency FSK coding mechanism, which dynamically selects the optimal carrier frequency based on channel conditions, effectively combating frequency-selective fading in the underwater acoustic channel and improving demodulation success rate under low signal-to-noise ratio conditions. Simultaneously, it introduces a symbol-level energy adaptive mechanism, allocating transmission energy according to data priority to optimize power consumption while ensuring reliable transmission of critical information. The buoy-end uses a multi-element hydrophone array weighted synthesis receiver, compensating for underwater acoustic channel losses through array gain, significantly improving communication distance and reliability without increasing underwater transmission power. Furthermore, it combines asymmetric frequency-shift FSK demodulation and Doppler compensation methods to effectively suppress frequency offset misjudgments caused by buoy movement, enhancing communication stability under complex sea conditions. In addition, the system supports remote command scheduling of underwater equipment from shore-based systems, forming a two-way communication closed loop through satellite and underwater acoustic links, improving the controllability and emergency response capabilities of the marine observation system. This invention is particularly suitable for long-term unattended marine observation scenarios such as deep-sea moorings and seabed seismometers, and has good prospects for engineering applications. Attached Figure Description

[0020] Figure 1 A schematic diagram of the structure of an integrated transmission system based on acoustic communication and satellite provided by the present invention;

[0021] Figure 2 This is a schematic diagram of the underwater acoustic adaptive multi-frequency FSK encoding and transmission structure provided by the present invention;

[0022] Figure 3 This is a schematic diagram of the buoy-end hydrophone array receiving and satellite communication processing structure provided by the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 and not intended to limit the invention.

[0024] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0025] like Figure 1 As shown, the integrated transmission system based on acoustic communication and satellite of this invention includes: a signal acquisition and processing module for seabed observation nodes, an underwater acoustic FSK encoding and low-frequency transducer transmission module, an underwater acoustic receiving and demodulation module for surface buoys, a buoy-end data scheduling and satellite encapsulation module, a satellite link transmission module, and a shore-based receiving and parsing module. The seabed observation nodes are deployed on the seabed, the buoys are located on the sea surface, and the shore-based receiving station is located on land.

[0026] During system operation, the sensors built into the signal acquisition and processing module of the seabed observation node continuously acquire environmental or geophysical signals. The acquired analog signals are converted into discrete-time signal sequences through analog-to-digital conversion.

[0027]

[0028] in The sampling period is defined as follows. To reduce the load on the underwater acoustic channel and extend the system's operating time, the seabed node first preprocesses the raw data, including event triggering decisions, feature extraction, and compression coding, to generate structured data frames. These data frames contain at least frame synchronization information, payload, channel coding bits, and a check field, thereby reducing the number of transmitted bits while ensuring data integrity.

[0029] The processed digital data is fed into the underwater acoustic FSK encoding and low-frequency transducer module for modulation. This system uses incoherent multi-frequency shift keying (MFSK) as the underwater acoustic modulation method. Each symbol to be transmitted is represented by a different carrier frequency, and its transmitted signal can be represented as:

[0030]

[0031] in The carrier frequency corresponding to the symbol. Energy is emitted for the symbol. Let be the symbol duration. Considering the significantly different absorption and attenuation characteristics of the underwater acoustic channel at different frequencies, the system does not use a fixed set of carrier frequencies during modulation. Instead, it combines historical communication results and channel statistical characteristics to screen the candidate frequency set, ensuring that the selected frequencies meet the condition of minimizing propagation loss. The propagation loss can be expressed as:

[0032]

[0033] in For the distance of transmission For diffusion factor, This represents the frequency-dependent absorption coefficient. By selecting a subset of frequencies with lower propagation loss within the available frequency band for FSK coding, the reliability of long-distance communication can be effectively improved.

[0034] To further improve the system's robustness in low signal-to-noise ratio environments, this invention introduces a symbol-level energy adaptive mechanism, allocating different transmission energies to different symbols based on data importance or error sensitivity, i.e., allowing... ,in This is the weighting coefficient. This mechanism ensures that critical state information has a higher probability of being received under the same channel conditions, while avoiding unnecessary increases in overall power consumption.

[0035] The modulated underwater acoustic signal is converted into a sound wave by a low-frequency underwater acoustic transducer and radiates upwards into the seawater medium. During propagation, the sound signal is affected by reflections from the water surface, the seabed, and the inhomogeneity of the medium, forming a typical time-varying multipath channel. Its impulse response can be expressed as:

[0036]

[0037] The corresponding received signal is:

[0038]

[0039] in and Let these represent the attenuation coefficient and delay of the i-th path, respectively. Environmental noise is also considered. Because the buoys on the sea surface move slowly under the influence of wind and waves, the system also needs to consider the frequency shift caused by the Doppler effect, with an approximate relationship as follows: During demodulation, this system corrects the carrier frequency through a frequency search and compensation mechanism, thereby reducing the impact of Doppler on incoherent FSK decisions.

[0040] After the underwater acoustic signal reaches the sea surface, it is received by the hydrophone array configured in the sea surface buoy's underwater acoustic receiving and demodulation module. The output signals of multiple hydrophone elements are weighted and synthesized to form the array output. Spatial synthesis is used to improve the received signal-to-noise ratio and suppress interference from non-target directions. Let the array received signal model be:

[0041]

[0042] in It is the array guide vector. This is array noise. The array output is obtained through weighted synthesis:

[0043]

[0044] weight vector Selected according to the least mean square criterion:

[0045]

[0046] This significantly improves the received signal-to-noise ratio.

[0047]

[0048] in This refers to the number of elements in the hydrophone. By compensating for underwater acoustic channel losses through array gain, communication distance and reliability are significantly improved without increasing underwater transmission power.

[0049] Subsequently, the underwater acoustic communication module at the buoy end performs noncoherent demodulation of the received signal and accumulates energy for each candidate carrier frequency:

[0050]

[0051] Symbol determination is performed based on the maximum energy criterion. The demodulated data is then verified and sent to the buoy-end data scheduling and satellite encapsulation module.

[0052] The buoy-end data scheduling and satellite encapsulation module performs time recombination and priority management on fragmented unmodulated data from the underwater acoustic link, and encapsulates it according to the transmission cycle and protocol format of the satellite communication link to form satellite uplink data frames. This data frame is transmitted to the on-orbit satellite via the satellite link transmission module, and then relayed by the satellite to the shore-based receiving station. The satellite channel can be approximated as a linear additive noise channel, and its reception model is as follows: .

[0053] The shore-based receiving system parses, verifies, and stores the data transmitted from the satellite, and then connects the results to the monitoring platform for display and analysis. Simultaneously, the shore-based system can generate control commands based on the received data, transmit them via satellite link to the buoy, and then via underwater acoustic communication link to the seabed node. This enables parameter configuration, operating mode switching, or data requests for seabed equipment, thus forming a complete two-way communication loop.

[0054] In a further embodiment of the present invention, the underwater acoustic FSK coding and low-frequency transducer module adopt an adaptive multi-frequency FSK coding mechanism, dynamically adjusting the FSK carrier frequency set according to the channel estimation results. Let the FSK coding symbol be... ,in Let k be the k-th frequency carrier. The system is based on the underwater channel signal-to-noise ratio (SNR) and frequency attenuation function. By comprehensively considering the absorption loss of the underwater acoustic channel and the received signal-to-noise ratio from the candidate frequency set, the frequency that minimizes the comprehensive cost function is selected as the FSK modulation frequency, thereby achieving adaptive optimization selection of underwater acoustic communication frequency:

[0055] .

[0056] In a further embodiment of the present invention, the underwater acoustic receiving and demodulation module of the sea surface buoy adopts an asymmetric frequency shift FSK demodulation method, resulting in unequal positive and negative frequency offsets, i.e. Demodulation is performed using the maximum likelihood decision method. And introduce a Doppler compensation factor: ,in The estimated Doppler scaling factor is used to reduce frequency offset misjudgment caused by motion and improve communication stability in scenarios where surface buoys move with the waves.

[0057] Through the above-described continuous technical process, this invention establishes a stable and efficient collaborative mechanism between underwater acoustic communication and satellite communication. While ensuring long-distance coverage, it significantly reduces the overall power consumption of the system and improves the reliability of data transmission under complex sea conditions. It is particularly suitable for applications such as deep-sea moorings, seabed earthquake observation, and long-term ocean monitoring.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A comprehensive transmission system based on acoustic communication and satellite, characterized in that, The integrated transmission system based on acoustic communication and satellite includes: The signal acquisition and processing module of the seabed observation node is used to digitize and initially simplify the underlying physical signals. The built-in sensors continuously acquire environmental and geophysical signals, convert them into discrete-time signal sequences through analog-to-digital conversion, execute event-triggered decisions, extract feature data, and compress and encode them to generate structured data frames. The underwater acoustic FSK encoding and low-frequency transducer transmission module is used to convert digital data frames into acoustic signals suitable for underwater propagation. Based on the signal-to-noise ratio and frequency attenuation function of historical communication feedback, it dynamically selects the frequency that minimizes the cost function from the candidate carrier frequency set for FSK modulation, executes a symbol-level energy adaptive mechanism, assigns weight coefficients to different symbols according to data priority, and drives the low-frequency underwater acoustic transducer to convert electrical signals into sound waves that radiate upwards. The underwater acoustic receiving and demodulation module for sea surface buoys is used to receive signals using a multi-element hydrophone array, select weight vectors for weighted synthesis using the least mean square criterion, suppress non-target direction noise, accumulate energy of each carrier frequency in the synthesized signal, and complete symbol decision and data verification based on the maximum energy criterion. The buoy-end data scheduling and satellite encapsulation module is used to reassemble and prioritize fragmented unmodulated data from the underwater acoustic link, and reconstruct the data into satellite uplink data frames according to the transmission cycle and protocol format of the satellite link. The satellite link transmission module is used to send the encapsulated satellite frames to the on-orbit satellite through the satellite terminal, realize long-distance wireless data relay between the buoy and the shore base, and listen to satellite commands in real time to receive remote scheduling and control commands issued by the shore base. The shore-based receiving and parsing module is used to perform multi-layer protocol parsing on satellite downlink data, store it in the database for the monitoring platform to call, and generate working mode switching and parameter configuration instructions based on the analysis results, which are then sent to the buoy via the satellite backhaul link.

2. The integrated transmission system based on acoustic communication and satellite according to claim 1, characterized in that, The underwater acoustic FSK coding and low-frequency transducer module adopts an adaptive multi-frequency FSK coding mechanism, which dynamically adjusts the FSK carrier frequency set according to the channel estimation results. Let the FSK coding symbols be: in: The signal amplitude; This is the k-th frequency carrier; This is the initial phase; The total number of carriers is determined based on the underwater channel signal-to-noise ratio (SNR) and frequency attenuation function. By comprehensively considering the absorption loss of the underwater acoustic channel and the received signal-to-noise ratio from the candidate frequency set, the frequency that minimizes the comprehensive cost function is selected as the FSK modulation frequency, thereby achieving adaptive optimization selection of underwater acoustic communication frequency: The optimal carrier frequency; For frequency The corresponding received signal-to-noise ratio; This is a weighting coefficient used to balance the impact of channel loss and signal-to-noise ratio on frequency selection.

3. The integrated transmission system based on acoustic communication and satellite according to claim 2, characterized in that, The underwater acoustic receiving and demodulation module of the sea surface buoy adopts an asymmetric frequency shift FSK demodulation method, resulting in unequal positive and negative frequency offsets: Demodulation is performed using the maximum likelihood decision: The symbol index obtained for the decision; To receive signals; For the first One candidate carrier frequency; The duration of the symbol; For carrier index. And a Doppler compensation factor is introduced: in: This is the estimated Doppler scaling factor.

4. The integrated transmission system based on acoustic communication and satellite according to claim 1, characterized in that, The underwater acoustic receiving and demodulation module of the sea surface buoy uses a multi-element hydrophone array to receive underwater acoustic signals. The array signal receiving model is as follows: in: It is the array guide vector. For the incident signal; It is array noise, obtained through weighted synthesis: z(t) is the array output signal; It is a weight vector; This is the conjugate transpose of the weight vector; y(t) is the array input signal vector. weight vector Selected according to the least mean square criterion: This improves the received signal-to-noise ratio. The signal-to-noise ratio of the array output; Signal-to-noise ratio for a single hydrophone; This represents the number of elements in the hydrophone array. in The number of basic elements for hydrophones.

5. The integrated transmission system based on acoustic communication and satellite according to claim 1, characterized in that, The underwater acoustic FSK coding and low-frequency transducer module introduces a symbol-level energy adaptive mechanism, which allocates different transmission energies to different symbols according to the importance of the data. That is, the transmission energy is a function of the weighting coefficient and the symbol duration, thereby improving the probability of receiving key state information under the same channel conditions.

6. The integrated transmission system based on acoustic communication and satellite according to claim 1, characterized in that, The underwater acoustic FSK coding and low-frequency transducer module introduces a symbol-level energy adaptive mechanism, which allocates different transmission energies to different symbols based on the bit error sensitivity. That is, the transmission energy is a function of the weighting coefficient and the symbol duration, thereby improving the probability of receiving key state information under the same channel conditions.

7. The integrated transmission system based on acoustic communication and satellite according to claim 1, characterized in that, The shore-based receiving and parsing module generates working mode switching and parameter configuration instructions based on the analysis results, which are sent to the buoy via the satellite backhaul link and then to the seabed node via the underwater acoustic communication link, forming a complete two-way communication closed loop.

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