A search and rescue method and system based on AIS, DSC and Beidou RDSS

Abstract

The application discloses a search and rescue method and system based on AIS, DSC and Beidou RDSS, the method comprising continuously acquiring a multi-source trigger signal of a MOB device, and constructing an instruction to obtain an alarm activation instruction; acquiring a Beidou positioning coordinate according to the alarm activation instruction, and initializing and activating a communication unit to obtain multi-mode communication unit information; constructing a three-mode signal based on the positioning coordinate and the multi-mode communication unit information to obtain an AIS broadcast signal, a DSC distress signal and a Beidou alarm signal; and transmitting the AIS broadcast signal, the DSC distress signal and the Beidou alarm signal by priority and in a cooperative response manner through the MOB device to obtain rescue response information. The application can significantly improve the coverage reliability and positioning accuracy of a distress signal in a complex sea environment.

Description

Technical Field

[0001] This application relates to the field of underwater beacon technology, and in particular to a search and rescue method and system based on AIS, DSC and Beidou RDSS. Background Technology

[0002] Maritime search and rescue technology is a core component of ensuring maritime safety, especially in the context of people falling overboard (MOB) scenarios, where the timeliness and reliability of rescue efforts are extremely critical. Traditional MOB equipment often relies on a single communication system (such as AIS or DSC alone), which has significant limitations: AIS signals are limited by VHF line-of-sight propagation, resulting in insufficient coverage in open seas or obscured waters; DSC distress alarms depend on shore stations or nearby vessels for relay, and are prone to transmission failures due to channel congestion or equipment compatibility issues; a single system failure or localized signal interference can lead to the complete loss of critical distress information. The G01S19 field focuses on satellite positioning and navigation and multi-source signal fusion, but existing technologies lack a collaborative integration mechanism for BeiDou RDSS satellite positioning, AIS, and DSC, failing to achieve intelligent fusion of multi-source trigger signals, dynamic adaptation of communication links, and optimized scheduling of signal priorities. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this application provides a search and rescue method based on AIS, DSC, and BeiDou RDSS, including:

[0004] Continuously acquire multi-source trigger signals from MOB devices, construct instructions, and obtain alarm activation instructions;

[0005] According to the alarm activation command, the BeiDou positioning coordinates are obtained, and the communication unit is initialized and activated to obtain the multi-mode communication unit information;

[0006] Based on the positioning coordinates and the multi-mode communication unit information, a three-mode signal is constructed to obtain the AIS broadcast signal, the DSC distress signal and the Beidou alarm signal.

[0007] The MOB device prioritizes and coordinates the transmission of the AIS broadcast signal, the DSC distress signal, and the BeiDou alarm signal to obtain rescue response information.

[0008] Preferably, the step of continuously acquiring multi-source trigger signals from the MOB device and constructing instructions to obtain an alarm activation instruction includes:

[0009] The physical buttons of the MOB device are subjected to level-triggered conversion of input signals to obtain button trigger signals;

[0010] Short-circuit feature detection is performed on the water fall detection terminal of the MOB device to obtain a water fall event identifier;

[0011] The MOB device is parsed using the Bluetooth terminal protocol to obtain the terminal control signal;

[0012] The button trigger signal, the water-falling event identifier, and the terminal control signal are fused together to obtain the multi-source trigger signal.

[0013] The multi-source triggering signals are logically compared based on a preset duration threshold to obtain a valid triggering flag.

[0014] The MOB device is voltage locked and status initialized based on the valid trigger flag, and the alarm activation command is obtained.

[0015] Preferably, the step of obtaining BeiDou positioning coordinates according to the alarm activation command and initializing and activating the communication unit to obtain multi-mode communication unit information includes:

[0016] Based on the alarm activation command, the circuit status of the MOB device is verified to obtain a power enable signal;

[0017] Based on the power enable signal, the positioning data is calculated by the BeiDou RNSS module of the MOB device to obtain the BeiDou positioning coordinates.

[0018] Based on the BeiDou positioning coordinates, the AIS module of the MOB device is configured with radio frequency timing to obtain AIS channel control information;

[0019] Based on the BeiDou positioning coordinates, the DSC module of the MOB device is subjected to protocol encoding and carrier parameter mapping to obtain a dual-frequency FSK modulation configuration table.

[0020] The BeiDou positioning coordinates are activated to obtain a link ready identifier by activating the BeiDou RDSS communication status.

[0021] The AIS channel control information, the dual-frequency FSK modulation configuration table, and the link ready identifier are integrated into multi-mode information to obtain the multi-mode communication unit information.

[0022] Preferably, the step of constructing a three-mode signal based on the positioning coordinates and the multi-mode communication unit information to obtain an AIS broadcast signal, a DSC distress signal, and a BeiDou alarm signal includes:

[0023] Based on the positioning coordinates, modulation parameters are loaded into the AIS channel control information of the multimode communication unit information to obtain radio frequency generation instructions;

[0024] The AIS module is signal-driven and constructed according to the radio frequency generation instructions to obtain the AIS broadcast signal;

[0025] Based on the positioning coordinates, the dual-frequency FSK modulation configuration table of the multi-mode communication unit information is mapped to a sinusoidal table address, and the DSC module is triggered in distress to obtain the DSC distress signal;

[0026] The satellite communication status is verified by the link readiness identifier to obtain the channel availability flag;

[0027] Based on the available channel marker, the BeiDou positioning coordinates are modulated and encoded to obtain the BeiDou alarm signal.

[0028] Preferably, the step of mapping the dual-frequency FSK modulation configuration table based on the positioning coordinates to a sine wave table for the multi-mode communication unit information, and triggering the DSC module to obtain the DSC distress signal, includes:

[0029] The sine wave table of the dual-frequency FSK modulation configuration table is subjected to dual-frequency FSK modulation to output a first encoding frequency and a second encoding frequency, wherein the encoding of the first encoding frequency is 0 and the frequency is 2100Hz, and the encoding of the second encoding frequency is 1 and the frequency is 1300Hz.

[0030] The timer reload value of the MOB device is dynamically modified according to the first encoding frequency and the second encoding frequency, and the corresponding frequency sine wave is output.

[0031] The location coordinates are processed using DSC distress protocol encoding to obtain a geographic information stream;

[0032] Based on the geographic information stream, the timer reload register of the MOB device is dynamically switched to obtain the carrier frequency selection parameters.

[0033] The frequency sine waveform is addressed in real time based on the carrier frequency selection parameters to obtain the DSC distress signal.

[0034] Preferably, the step of prioritizing and coordinating the transmission and response of the AIS broadcast signal, the DSC distress signal, and the BeiDou alarm signal through the MOB device to obtain rescue response information includes:

[0035] Based on a preset first transmission time, the AIS broadcast signal is transmitted via radio frequency control through the MOB device to obtain an AIS completion identifier;

[0036] Based on a preset second transmission time, the MOB device performs carrier modulation output and response monitoring on the DSC distress signal to obtain DSC response data.

[0037] Based on the preset third launch time, the MOB device performs signal strength threshold verification and satellite link triggering on the BeiDou alarm signal to obtain the BeiDou transmission identifier;

[0038] The AIS completion identifier, the DSC response data, and the BeiDou transmission identifier are aggregated to obtain joint scheduling information.

[0039] The rescue terminal receives the task response based on the joint scheduling information and obtains the rescue response information.

[0040] Preferably, the DSC distress signal is carrier-modulated and output and the response is monitored by the MOB device based on a preset second transmission time to obtain DSC response data, including:

[0041] Based on the AIS completion identifier, a DSC enable command is generated by the main control MCU of the MOB device;

[0042] According to the DSC enable command, the MOB device performs carrier modulation output and activates the DSC listening state;

[0043] In the DSC listening state, the MOB device captures DSC response data according to the preset listening duration and performs symbol width analysis to obtain valid symbol markers;

[0044] Based on a preset preamble sequence, the effective symbol marker is subjected to preamble synchronization detection to obtain a preamble matching result.

[0045] The response content of the DSC response data is parsed based on the preamble matching result to obtain the DSC response confirmation data.

[0046] Preferably, based on a preset third transmission time, the MOB device performs signal strength threshold verification and satellite link triggering on the BeiDou alarm signal to obtain a BeiDou transmission identifier, including:

[0047] Based on the DSC response data, the MOB device is monitored for module sleep duration to obtain a sleep identifier, and a wake-up command is constructed to obtain a module wake-up command.

[0048] The module wake-up command is used to enable hardware power supply to the MOB device, and a module ready flag is obtained.

[0049] Launch license identification is performed based on the module readiness identifier to obtain a launch license marker;

[0050] Based on the launch permission mark, satellite link triggering and BeiDou short message transmission operations are performed to obtain satellite transmission status frames;

[0051] The FKI flag bit is parsed on the satellite transmission status frame to obtain the BeiDou transmission identifier.

[0052] This application also provides a search and rescue system based on AIS and BeiDou RDSS, applied to any of the above-described search and rescue methods based on AIS, DSC, and BeiDou RDSS, including:

[0053] The acquisition module is used to continuously acquire multi-source trigger signals from the MOB device, construct instructions, and obtain an alarm activation instruction.

[0054] The analysis module is used to obtain BeiDou positioning coordinates according to the alarm activation command, and to initialize and activate the communication unit to obtain multi-mode communication unit information.

[0055] The association module is used to construct three-mode signals based on the positioning coordinates and the multi-mode communication unit information to obtain AIS broadcast signal, DSC distress signal and Beidou alarm signal;

[0056] The processing module is used to prioritize and coordinate the transmission of the AIS broadcast signal, the DSC distress signal, and the Beidou alarm signal through the MOB device to obtain rescue response information.

[0057] The technical solution provided in this application may include the following beneficial effects:

[0058] By constructing instructions from multi-source triggering signals and coordinating the activation of multi-mode communication units, the problem of coverage blind spots in a single communication system is effectively solved, significantly improving the global transmission reliability of distress signals in complex sea areas. The priority-based multi-mode signal transmission and coordinated response mechanism overcomes the shortcomings of traditional DSC or AIS signals, which are susceptible to channel congestion or obstruction interference, achieving efficient redundant transmission and precise delivery of distress information. By integrating the advantages of BeiDou RDSS positioning and AIS / DSC communication, while improving positioning accuracy, multi-system complementary fault tolerance is achieved, reducing the risk of partial equipment failure and enhancing the overall robustness of the search and rescue system. Relying on dynamic scheduling and resource optimization of multi-mode signals, efficient coordination of distress information in time, space, and spectrum dimensions is achieved, significantly shortening rescue response time and improving the overall effectiveness of maritime search and rescue operations.

[0059] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0060] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0061] Figure 1 A flowchart of a search and rescue method based on AIS, DSC and Beidou RDSS provided for this application;

[0062] Figure 2 This is one of the flowcharts shown in the embodiments of this application;

[0063] Figure 3 This is a second flowchart illustrating an embodiment of this application;

[0064] Figure 4 This application provides a structural diagram of a search and rescue system based on AIS and BeiDou RDSS. Detailed Implementation

[0065] Preferred embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0066] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0067] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0068] Reference Figure 1 As shown, this application provides a search and rescue method based on AIS, DSC, and BeiDou RDSS, including:

[0069] Step S1: Continuously acquire multi-source trigger signals from the MOB device and construct instructions to obtain alarm activation instructions;

[0070] Step S2: Obtain the BeiDou positioning coordinates according to the alarm activation command, and initialize and activate the communication unit to obtain the multi-mode communication unit information;

[0071] Step S3: Construct three-mode signals based on positioning coordinates and multi-mode communication unit information to obtain AIS broadcast signal, DSC distress signal and Beidou alarm signal;

[0072] Step S4: Prioritize and coordinate the transmission of AIS broadcast signals, DSC distress signals, and BeiDou alarm signals through the MOB device to obtain rescue response information.

[0073] Step S1:

[0074] The mechanical contact of a physical button triggers a change in the MOSFET gate control voltage. Initially, the MOSFET operates in a high-impedance state, and the battery power supply circuit is disconnected. When the button is pressed, the mechanical structure activates the gate drive circuit, the MOSFET turns on, and the battery outputs power to the entire power supply system. After the system powers on, the microcontroller's timer starts monitoring the duration of the press. When the continuous press time reaches a preset threshold, the power management unit sets the power holding latch, which continuously maintains the MOSFET gate voltage, keeping the power supply circuit on even when the physical button is released. If the press time is less than the preset threshold, a shutdown signal triggers the MOSFET to return to the high-impedance state, and the power supply circuit is automatically cut off. This mechanism achieves hard linkage between button triggering and power supply status, ensuring that the device only maintains its operating state after a valid trigger.

[0075] The impedance change characteristics between the water-fall detection electrode pairs are monitored by a constant current source circuit. When seawater immersion causes the impedance to drop to a preset short-circuit threshold, a water-fall event identifier is generated. The Bluetooth communication module parses the command frames sent by the mobile terminal based on the BLE4.2 protocol stack and extracts the terminal control signals after CRC verification.

[0076] The three-channel signal input multi-source fusion processor executes priority decision logic: physical button activation and water-falling event triggering have the highest response priority, with Bluetooth commands serving as auxiliary trigger sources; when the duration of any trigger source exceeds the anti-accidental touch threshold, a valid trigger flag is generated. This flag triggers the gate control terminal of the MOSFET power latch circuit, stabilizing the device's power supply voltage, resetting the microcontroller's status register, loading the emergency mode firmware, and finally outputting an alarm activation command to the main control bus.

[0077] Step S2:

[0078] The alarm activation command triggers dynamic power allocation: prioritizing power allocation to the BeiDou RNSS module, acquiring satellite signals via frequency points, and calculating the coordinate system positioning coordinates. These coordinates are then synchronously input into the tri-mode unit.

[0079] AIS module configuration: Calculate the TDMA timeslot number based on the last three digits of the MMSI number, and configure the RF timer reload value to be timeslot number × 26.67ms;

[0080] DSC module configuration: Encapsulate distress location information according to the protocol and generate a 1300Hz / 2100Hz dual-frequency carrier mapping table;

[0081] BeiDou RDSS Activation: Monitors the signal strength of the band and sets the link ready flag when needed.

[0082] The three configuration parameters are integrated via a parallel data bus to form a multi-mode communication unit information packet that includes time slot control parameters, carrier frequency mapping, and satellite link status.

[0083] Step S3:

[0084] For the construction of AIS broadcast signals, longitude / latitude data is encapsulated in a coordinate format, and AISMessage 1 type messages are generated according to the protocol, including a 9-bit MMSI identifier, a navigation status field, and high-precision positioning information. During the encapsulation process, the TDMA time slot dynamic allocation algorithm is executed, and the transmission time slot number is determined based on the hash value of the last three bits of the MMSI. The GPS second pulse signal is bound for clock synchronization compensation. For DSC distress signals, a distress geocoding sequence is generated according to the ITU-R M.493-16 standard, including distress type code, location coordinates, and timestamp information. The modulation waveform is generated using a dual-carrier FSK modulation strategy: bit "0" corresponds to a 2100Hz carrier, and bit "1" corresponds to a 1300Hz carrier. The carrier phase continuity is ensured by a sine wave table pre-storage technology.

[0085] The construction of the BeiDou alarm signal follows the RDSS short message protocol format, byte-compressing and encoding the positioning coordinates and additional text information, and using BPSK modulation to adapt to the 1615.68MHz satellite uplink frequency band. The three signals enter dedicated modulation channels: the AIS module uses a GMSK modulator configured at a baud rate of 9.6kbps, the DSC module activates the waveform pass-through mode of the direct memory access controller, and the BeiDou module activates the forward power control circuit. The final output AIS broadcast signal, DSC distress signal, and BeiDou alarm signal carry the same location coordinate source data, achieving a unified spatial reference across multiple systems.

[0086] Step S4:

[0087] A strict priority transmission sequence is implemented: The AIS RF power amplifier module is activated in the first allocated time slot, broadcasting navigation safety data packets via the 161-162MHz maritime mobile frequency band. Immediately after AIS transmission, the DSC distress call procedure is activated, transmitting a digital distress sequence at a rate of 1200 bits per second in the 156MHz band. Simultaneously, a dual-mode response monitoring window is opened, and a dedicated demodulation chip performs feature analysis on the received signal. When a signal conforming to an 833-microsecond symbol width and a standard preamble sequence is detected, device identity matching verification is performed.

[0088] For satellite communication systems, a dual-condition wake-up is implemented after confirming the completion of DSC transmission: L-band signal-to-noise ratio characteristics are continuously monitored, and the satellite message transmission procedure is triggered when the signal strength continuously exceeds a preset threshold or the waiting time reaches its limit. Rescue response data collection includes three levels of terminal feedback: real-time location and heading information returned by the Automatic Identification System (AIS) terminal, dispatch instructions forwarded by the Digital Call System (DCS) base station, and communication confirmation identifiers transmitted back by the satellite ground station. These three are integrated in the protocol conversion engine into a deployment plan for rescue forces in the target sea area, generating a structured response dataset containing rescue unit coordinates, estimated arrival time, and equipment type.

[0089] This application provides a search and rescue method based on AIS, DSC, and BeiDou RDSS. By constructing instructions from multi-source trigger signals and coordinating the activation of multi-mode communication units, it effectively solves the coverage blind spot problem of a single communication system, significantly improving the global transmission reliability of distress signals in complex sea areas. The priority-based multi-mode signal transmission and coordinated response mechanism overcomes the shortcomings of traditional DSC or AIS signals, which are susceptible to channel congestion or obstruction interference, achieving efficient redundant transmission and accurate delivery of distress information. By integrating the advantages of BeiDou RDSS positioning and AIS / DSC communication, it improves positioning accuracy while achieving multi-system complementary fault tolerance, reducing the risk of partial equipment failure and enhancing the overall robustness of the search and rescue system. Relying on dynamic scheduling and resource optimization of multi-mode signals, it achieves efficient coordination of distress information in time, space, and spectrum dimensions, significantly shortening rescue response time and improving the overall effectiveness of maritime search and rescue operations.

[0090] In one embodiment, multi-source trigger signals from the MOB device are continuously acquired, and instructions are constructed to obtain an alarm activation instruction, including:

[0091] The contact action of the mechanical button generates an initial voltage level signal. This signal is filtered by an RC filter network to eliminate contact bounce interference before being input to a voltage comparator for threshold determination. When a sustained high level is detected exceeding the debounce time window, a Schmitt trigger is activated to shape the waveform, outputting a standard TTL logic level pulse signal. This pulse signal is electrically isolated by an optocoupler to eliminate ground loop interference, ultimately generating the button trigger signal and latching it into the input status register. The signal conversion process is implemented using hardware circuitry, with response delay controlled in the microsecond range to ensure real-time button operation.

[0092] The water-fall detection electrodes are exposed to the equipment casing, with a constant voltage detection current (typically 1mA) applied between them. A differential amplifier monitors the impedance change between the electrodes in real time. When seawater immersion causes the impedance to drop to a preset short-circuit threshold, a window comparator output state is triggered to flip. This state signal is input to a timer circuit; if the low impedance state persists for longer than the false alarm period, a water-fall event flag is generated.

[0093] The Bluetooth RF front-end receives the modulated signal and recovers it as a digital bitstream via the baseband demodulator. This bitstream is input to the protocol parsing engine, which decomposes the frame structure according to the Bluetooth Low Energy communication specification: extracting the preamble for clock synchronization, parsing the access address for device address matching, and verifying the CRC field to confirm data integrity. The valid data payload is converted into control command words by the instruction decoder, including opcodes for alarm triggering, mode switching, and test commands. The parsing process employs a double-buffering mechanism: the front-end receives data in real time, while the back-end performs protocol analysis, ensuring that the instruction response delay does not exceed the communication cycle. Finally, the terminal control signal is output to the main controller's instruction queue.

[0094] A weighted decision processor receives three independent signal inputs. Physical button trigger signals are assigned priority response weights, a water-fall event identifier is configured with a high-sensitivity response coefficient, and a Bluetooth terminal control signal is set with auxiliary trigger weights. Each signal, after normalization, enters a weighted summation unit. When the weighted cumulative value exceeds a fusion threshold, a multi-source trigger signal is generated. The fusion process is implemented using hardware logic circuitry, outputting a fusion status flag to the control bus in real time to eliminate software processing latency. The multi-source trigger signal includes the status codes of the three signal sources and a fusion timestamp, forming a structured trigger data packet.

[0095] A multi-source trigger signal input programmable timer circuit starts accumulating duration when the fusion status flag remains active. This duration input window comparator logically compares the duration with a preset anti-accidental trigger threshold. When the actual duration is greater than or equal to the preset threshold, the valid trigger flag latch is set. The timer's time measurement accuracy is ≤0.1%. The preset duration threshold is stored in non-volatile memory and supports field configuration updates. The valid trigger flag contains the trigger type code and valid duration data, and is output to the system control core.

[0096] Effective trigger flag triggers the voltage lockout function of the power management chip: the control circuit stabilizes the supply voltage within the range of 3.3V±0.1V, with a ripple factor ≤1%. Activation state initialization sequence: the microcontroller reset vector points to the emergency mode firmware entry, clears all peripheral status registers, and loads the default communication parameter configuration table.

[0097] The voltage lockout circuit employs a negative feedback compensation design to maintain output voltage fluctuations under surge conditions. The state initialization process includes clock system calibration, peripheral self-test, and interrupt vector remapping operations to ensure the system enters a standardized emergency response state. Finally, an alarm activation command is output to the system bus, including a power supply status code and an initialization completion flag.

[0098] This embodiment significantly improves the triggering reliability of the equipment under harsh sea conditions by employing hardware-level fusion and duration verification mechanisms for multi-source trigger signals, avoiding false alarms caused by interference from a single signal. Voltage locking and state initialization collaborative control ensure stable power supply to the positioning and communication units, guaranteeing the validity of high-precision positioning data. A dynamic configuration strategy for three-mode communication resources enables on-demand activation of AIS, DSC, and BeiDou systems, significantly reducing overall power consumption while maintaining full-area coverage. A multi-level response aggregation mechanism integrates rescue feedback from ships, shore-based systems, and satellites, forming structured rescue decision support and improving the accuracy and timeliness of search and rescue dispatch.

[0099] In one embodiment, the BeiDou positioning coordinates are obtained according to the alarm activation command, and the communication unit is initialized and activated to obtain multi-mode communication unit information, including:

[0100] The alarm activation command triggers the status diagnostic unit of the power management chip, which collects the power supply bus voltage ripple coefficient, load current transient response, and temperature drift parameters in real time. The diagnostic data input window comparator compares the data with a preset safety threshold to generate a power enable signal. This signal activates the multi-channel load switch control circuit, directly connecting the 6V main power supply to the system power supply bus, while simultaneously controlling the start / stop status of the digital power supply path and the RF power supply path through independent load switches. The digital power supply path is generated by a buck converter, and the RF power supply path is output by a low-dropout regulator. The power supplies of each module are physically isolated through load switches, ensuring that the on / off operation of any module does not affect the power supply stability of other paths. The circuit verification process is implemented using a hardware state machine, with response latency controlled to the millisecond level, ensuring the power supply integrity for subsequent high-precision operations.

[0101] The power enable signal activates the B1I frequency signal acquisition link of the BeiDou RNSS module, receiving navigation signals through a four-element microstrip antenna array. After gain compensation by a low-noise amplifier, the received signal enters the carrier phase tracking loop and code phase delay-locked loop for collaborative demodulation. The demodulated data stream is input to the positioning calculation engine, executing a three-frequency carrier phase smoothing pseudorange algorithm: using B1I, B2I, and B3I frequency observations to construct an ionospheric delay correction model, and combining it with wide-area differential augmentation data to eliminate tropospheric refraction errors. The calculation result outputs three-dimensional positioning data in a coordinate system, including longitude, latitude, and elevation values. The positioning coordinate data packet is appended with a timestamp and satellite geometric accuracy factor identifier, forming a standardized BeiDou positioning coordinate output.

[0102] The BeiDou positioning coordinates are input into the TDMA time slot calculation unit, which extracts the last three decimal digits of the device's MMSI code as a hash seed to generate a basic time slot number. This number is then time-synchronized with the GPS second pulse signal: a phase-locked loop circuit aligns the rising edge by 1PPS to compensate for accumulated errors caused by crystal oscillator frequency drift. The calibrated time slot number is input into the RF timer control unit to configure the start time and duration of the 26.67 millisecond transmit window. The RF timing parameters, including the carrier frequency selection code, Gaussian minimum shift keying modulation index, and transmit power level, are encapsulated into a structured AIS channel control information packet. This control information packet is transmitted to the AIS baseband processor via a high-speed serial bus to complete the RF link pre-configuration.

[0103] The BeiDou positioning coordinate input digital selective calling protocol encoder generates a 9-bit geographic coordinate encoding sequence according to international maritime distress communication standards, including longitude / latitude quantification values, timestamps, and distress type codes. The encoded sequence is converted into binary data frames by a bitstream generator. The carrier parameter mapping unit dynamically configures the dual-frequency carriers based on the bit values: binary 0 corresponds to a 2100Hz sine carrier, and binary 1 corresponds to a 1300Hz sine carrier. Phase continuity control of the carrier frequency parameters is achieved through a pre-stored waveform table; the 2100Hz and 1300Hz sine carriers are stored in the same sine wave table. The dual-frequency carrier parameters and the bitstream timing relationship form a structured mapping table, including carrier frequency switching logic, waveform table base address, and baud rate control parameters, constituting a dual-frequency FSK modulation configuration table output to the DSC modulation controller.

[0104] The link monitoring unit of the RDSS module inputs BeiDou positioning coordinates to collect the signal-to-noise ratio (SNR) characteristics of the band signal in real time. Signal strength parameters are input to a dual-threshold comparator: when the instantaneous SNR exceeds the 25 dB-Hz threshold for two consecutive seconds, or the cumulative monitoring duration reaches the 6-second limit, the link ready flag setting circuit is triggered. The activation process employs a phased power control strategy: initially, a low-gain receive mode is configured, switching to a high-gain transmit mode upon detecting a valid signal.

[0105] Link status monitoring data includes carrier lock flags, bit error rate statistics, and historical signal strength curves, encapsulated into a link readiness identifier data packet. This identifier, containing real-time communication quality indicators and an activation timestamp, is transmitted to the system control core via a high-speed serial interface.

[0106] The AIS channel control information packet, dual-frequency FSK modulation configuration table, and link ready identifier data packet are integrated into a multi-mode resource. The integration process involves protocol adaptation and timing alignment: the time slot window information of the AIS radio frequency timing parameters is extracted and time-base synchronized with the baud rate parameters of the DSC modulation configuration table to ensure no timing conflicts between the two systems. The RDSS link status data is embedded into the BeiDou short message protocol frame header to generate a satellite communication enable command.

[0107] The three configuration data streams are converted into a unified multi-mode communication unit information, including communication mode identifier, frequency band selection parameters, transmit power level, and error check code. This multi-mode communication unit information is stored in a non-volatile configuration register and output to the communication coprocessor via the data bus, completing the ready-to-go configuration of the three-mode communication system.

[0108] This embodiment significantly improves the triggering reliability of the equipment under harsh sea conditions by employing hardware-level fusion and duration verification mechanisms for multi-source trigger signals, avoiding false alarms caused by interference from a single signal. Voltage locking and state initialization collaborative control ensure stable power supply to the positioning and communication units, guaranteeing the validity of high-precision positioning data. A dynamic configuration strategy for three-mode communication resources enables on-demand activation of AIS, DSC, and BeiDou systems, significantly reducing overall power consumption while maintaining full-area coverage. A multi-level response aggregation mechanism integrates rescue feedback from ships, shore-based systems, and satellites, forming structured rescue decision support and improving the accuracy and timeliness of search and rescue dispatch.

[0109] In one embodiment, a three-mode signal is constructed based on positioning coordinates and multi-mode communication unit information to obtain an AIS broadcast signal, a DSC distress signal, and a BeiDou alarm signal, including:

[0110] The positioning coordinates are input into the time slot allocation engine, which extracts the last three digits of the device's MMSI code, performs a hash operation, and combines this with the rising edge of the GPS second pulse signal for synchronous triggering to generate a precise TDMA transmit time slot number. This number is input into the RF timing controller to configure the start time offset and duration of the transmit window.

[0111] The modulation parameter loading unit parses the AIS channel control information from the multimode communication unit information packet, extracting the carrier frequency selection code, Gaussian minimum shift keying modulation index, and transmit power level parameters. These parameters, along with the TDMA time slot number, are encapsulated into a structured RF generation instruction, containing an RF switch enable flag, carrier frequency register value, and power amplifier gain control word. The RF generation instruction is transmitted to the AIS baseband processor via a high-speed serial bus to complete the preloading of physical layer modulation parameters.

[0112] The RF generation command triggers the baseband processor to execute protocol encapsulation: the positioning coordinates are encoded into binary data frames according to navigation safety message specifications, and a 16-bit CRC checksum and preamble sequence are added. The encapsulated data stream is input to a Gaussian minimum shift keying modulator, which uses quadrature phase offset keying technology to generate I / Q quadrature baseband signals. The baseband signals are then converted into analog differential signals by a digital-to-analog converter and finally converted into single-ended RF signals.

[0113] The RF front-end configures the phase-locked loop local oscillator based on the carrier frequency register value to generate the frequency band carrier. The modulation signal and carrier undergo spectrum shifting in the mixer, and the output signal is adjusted for transmission level by a variable gain amplifier according to the power control word. Finally, the AIS broadcast signal is generated.

[0114] The location coordinates are input into the distress protocol encoder, which generates a 9-bit geocoded sequence according to the digital selective calling specification, including longitude / latitude quantifications, a UTC timestamp, and a distress type identifier. The coded sequence is converted into rate data frames by a bitstream generator. The dual-frequency FSK modulation configuration table is extracted from the multimode communication unit information packet, and the 1300Hz / 2100Hz sine wave table storage base address and waveform length parameters are parsed.

[0115] The sine wave table address mapping unit dynamically switches the memory access pointer based on the current bit value: bit "0" points to the 2100Hz waveform table base address, and bit "1" points to the 1300Hz waveform table base address. The distress trigger signal activates the automatic transfer mode of the direct memory access controller (DMC), continuously reading data points from the waveform table according to the timer interrupt cycle, and generating a stepped analog signal through a digital-to-analog converter (DAC). The stepped signal is smoothed by a second-order Butterworth low-pass filter and outputs the DMC distress signal.

[0116] The link readiness flag is verified by parsing the historical signal strength curve, carrier lock flag, and bit error rate statistics. The verification process employs a dual-threshold decision logic: when the instantaneous signal strength exceeds a preset strength threshold for two consecutive seconds, or when the cumulative monitoring time reaches a preset waiting limit, the channel availability flag setting circuit is triggered.

[0117] The verification unit synchronously performs carrier synchronization status detection and confirms carrier tracking stability via a phase-locked loop (PLL) lock-in indicator. The verification result is appended with a timestamp and quality assessment coefficients to generate a channel availability tag data packet. This tag, containing a real-time link quality index and activation / enabling instructions, is transmitted to the satellite communication coprocessor via the control bus.

[0118] The channel can use marker-triggered short message protocol encapsulation to encode BeiDou positioning coordinates into binary data frames according to the RDSS communication standard, adding a 16-bit cyclic redundancy check code and a protocol version identifier. The additional information processing unit performs rich media compression coding: voice segments are compressed into a 13kbps bitstream using an adaptive multi-rate algorithm, location images are compressed into JPEG-LS format using discrete cosine transform, and text information is compressed using Huffman coding. The compressed data is then concatenated with the basic positioning frame using protocol data units to generate a composite satellite message.

[0119] The modulation and control unit is equipped with a BPSK modulator: the baseband data stream passes through a raised cosine pulse shaping filter to generate an orthogonal signal; the carrier generator locks onto the target frequency, and the local oscillator signal and the baseband signal are mixed in the orthogonal modulator to output an RF signal. The final generated BeiDou alarm signal is then output to the antenna radiating element after gain control by a power amplifier, meeting the requirements of the satellite uplink power spectral density template.

[0120] This embodiment significantly improves the triggering reliability of the device under harsh sea conditions by using hardware-level fusion and duration verification mechanisms for multi-source trigger signals, avoiding false alarms caused by interference from a single signal. Voltage locking and state initialization coordinated control ensure stable power supply to the positioning and communication units, guaranteeing the validity of high-precision positioning data. The dynamic configuration strategy for three-mode communication resources enables on-demand activation of the AIS, DSC, and BeiDou systems, significantly reducing overall power consumption.

[0121] In one embodiment, a sine wave table mapping is performed on the dual-frequency FSK modulation configuration table of the multi-mode communication unit information based on the positioning coordinates, and the DSC module is triggered in distress to obtain a DSC distress signal, including:

[0122] The dual-frequency FSK modulation configuration table is input into the sine wave table parsing engine. Based on the preset storage address offset and data length fields, it extracts the discrete sine wave sequences of two carriers, 1300Hz and 2100Hz, from non-volatile memory. The parsing process performs data integrity verification: a 16-bit checksum algorithm is used to confirm the bit integrity of the waveform table data; erroneous data triggers an automatic reload mechanism.

[0123] The 1300Hz carrier sequence is labeled as the first coding frequency, containing single-cycle quantized amplitudes at a 48kHz sampling rate; the 2100Hz carrier sequence is labeled as the second coding frequency, using the same sampling rate but with independently configured phase start points. The parsed results are appended with a sampling rate identifier and amplitude normalization coefficients to generate a dual-waveform table data structure. This structure is transferred to a dual-port RAM buffer via a direct memory access interface, providing the basic waveform dataset for subsequent memory allocation.

[0124] The first and second encoding frequencies are input to the memory manager, which calculates the physical storage requirements based on the waveform data length and memory bit width parameters. The storage area partitioning employs a hard address space isolation strategy: within the mapped address space of the direct memory access controller. Block boundaries are access-restricted through a memory protection unit, prohibiting unauthorized cross-block access. After partitioning, a frequency sine wave is generated, containing the start and end addresses of blocks A and B, as well as the data step offset. The frequency sine wave is written to the source address remapping register group of the DMA channel, enabling automatic hardware switching of the waveform table. The storage area partitioning result is simultaneously updated to the configuration status register, allowing the system to query the storage resource occupancy status in real time.

[0125] The location coordinates are input into the geocoding engine, and protocol conversion is performed according to the international standard for selective digital calling: longitude / latitude data is converted to degrees, minutes, and seconds and quantized to 0.01 minute precision, with the addition of a UTC timestamp and distress type encoding. During the encapsulation process, protocol control fields are added: the start flag uses a fixed binary preamble "10101010", the message type identifier is set to the distress alarm code, and the check field uses the CRC-16 algorithm to generate a redundant checksum. The encoded data is converted into 1.2kbps serial data frames by a bitstream generator, with the frame structure strictly adhering to the specification of 833μs duration per bit. The generated geographic information stream contains 24 bits of payload data, with the addition of a frame synchronization header and end flag, forming a standardized DSC distress data stream. This data stream is transmitted to the modulation and control unit via a high-speed serial interface, providing a baseband signal source for carrier modulation.

[0126] The geographic information stream input frequency parameter calculation selects the target frequency based on the current bit value (binary "0" maps to 2100Hz, binary "1" maps to 1300Hz). The target frequency parameter is input to the timer reload value calculation unit. Based on the master clock frequency (48MHz), one timer controls the 1.2k bit rate specified by the protocol, that is, the timer is interrupted once every 1 / 1.2k time interval to transmit one bit, and another timer triggers the control, and the DMA moves the data to the DAC.

[0127] Configure a sine wave table for dual-frequency FSK modulation, where code 0 corresponds to a frequency of 2100Hz and code 1 corresponds to a frequency of 1300Hz; dynamically modify the timer reload value based on the current code value to output a sine wave of the corresponding frequency.

[0128] The carrier frequency selection parameter input address mapping controller is configured with a sine wave table for dual-frequency FSK modulation, where code 0 corresponds to a frequency of 2100Hz and code 1 corresponds to a frequency of 1300Hz.

[0129] When the encoding value is 1, the timer reload value is dynamically modified, outputting a sine wave at the first encoding frequency (1300Hz); when the encoding value is 0, the timer reload value is dynamically modified, outputting a sine wave at the second encoding frequency (2100Hz). The address calculation unit dynamically refreshes the read pointer according to the baud rate timer interrupt signal: at the beginning of each 833μs interrupt cycle, the waveform table is reset and the offset is read to the zero address; within the interrupt cycle, the address offset is incremented according to the sampling rate. The current data address contains the block base address and offset address information in real time, forming the physical storage address. This address is updated in real time through the continuous addressing register of the DMA channel, establishing a hardware pass-through link from the bit stream to the waveform storage area.

[0130] The current data address is written to the source address register of the DMA controller, and the destination address is configured as the physical address of the DAC data register. The DMA channel is configured for cyclic transfer mode: 16 bits of waveform data are transferred each time, and the transfer length matches the number of points in a single-cycle sine wave table. The transfer trigger signal is bound to the update interrupt of the baud rate timer (TIM1), and a new round of DMA transfer is automatically triggered every 833μs interrupt cycle. The transfer process requires no CPU intervention, and the DAC continuously outputs a stepped waveform to the reconstruction filter under DMA trigger. A second-order Butterworth low-pass filter (cutoff frequency 3kHz) smooths the stepped waveform and outputs a DSC distress signal that conforms to the spectrum template.

[0131] This embodiment achieves precise hardware-level control of the FSK modulation process through a dual-timer coordinated carrier dynamic switching mechanism, eliminating reliance on traditional dedicated RF chips and significantly reducing equipment manufacturing costs. DMA pass-through waveform table transfer technology ensures carrier phase continuity and real-time frequency switching, avoiding modulation distortion caused by CPU intervention. Using the same positive selection table, two different frequencies are precisely simulated and modulated based on the encoding settings of the timer reload value, thus ensuring no crosstalk in the carrier signal and that the output spectrum purity meets communication standards. The hard synchronization design of the bitstream and time base brings the 833-microsecond symbol duration error close to zero, significantly improving the signal resolution success rate at the receiver.

[0132] Reference Figure 2As shown, in one embodiment, the MOB device prioritizes and coordinates the transmission of AIS broadcast signals, DSC distress signals, and BeiDou alarm signals to obtain rescue response information, including:

[0133] After the RF control transmission process is initiated, the device's location information status is detected. First, the system switches to AIS broadcast signal transmission mode: if there is no location information, one AIS message is sent per second, and a basic message is broadcast once per minute; if there is location information, the time slot allocation mechanism of the Time Division Multiple Access algorithm is activated. This mechanism specifies the transmission time slots through GPS second pulse synchronization and a hash algorithm based on the Device Identity Code (MMSI). The start point of the time slot window is strictly aligned with the rising edge of the GPS second pulse.

[0134] The first message, due to the inability to predict the time slot, requires immediate preparation of message information, activation of RF bias compensation, startup of a high-precision timer, and reset of timing and message count counters; after each transmission, an event is triggered to recalculate the next time slot; subsequent messages prepare data packets in advance based on the time slot and activate the bias; when the time slot arrives, the RF power amplifier module is immediately activated and broadcasts navigation safety data packets through the maritime mobile frequency band.

[0135] The data packet encapsulation process follows standard protocol specifications, including longitude / latitude positioning coordinates, navigation status identifiers, and cyclic redundancy check codes. During transmission, AIS broadcast signals are transmitted according to a preset first transmission time, and an 8-message continuous transmission limit mechanism is implemented: each transmission updates the message count counter; if the count value is greater than 8, transmission is terminated and the last transmission time is updated. Transmission automatically terminates when the counter's accumulated value reaches a threshold. After transmission is complete, an AIS completion identifier is generated, including the final transmission timestamp, the number of messages transmitted, and the spectrum occupancy status code; the identifier data is written to the system status register.

[0136] The AIS completes the identification trigger carrier modulation output sequence: the Direct Memory Access Controller loads 1300Hz / 2100Hz sine wave table data (timing is controlled synchronously by the timer in the transmission process), and the timer reload register dynamically switches the carrier frequency according to the bit stream. The modulated signal outputs a stepped waveform through the digital-to-analog converter (conversion start and stop are triggered by the "start transmission" flag in the transmission process), and switches to DSC distress signal transmission mode based on the preset second transmission time.

[0137] Based on synchronous dual-channel response monitoring: A dedicated demodulation chip scans the receiving channel, captures the signal, and inputs it to a symbol width analyzer for verification over an 833-microsecond duration. Signals meeting the duration threshold enter the preamble synchronization detection unit, where a Hamming distance check (tolerance ≤ 1 bit) is performed on the "10101010" sequence. The verified signal frames undergo device identification code matching verification to extract valid response data packets. The response data includes the acknowledgment frame type, source device identification code, and time synchronization information, encapsulated into a DSC response data structure.

[0138] When the satellite link activation decision unit identifies the arrival of the preset third launch time, it parses the response status code to determine whether satellite communication needs to be initiated. Link activation executes a dual threshold verification mechanism: real-time monitoring of the historical L-band satellite signal strength curve; when the instantaneous signal-to-noise ratio exceeds a preset strength threshold for two consecutive seconds, or the cumulative monitoring time reaches a preset waiting limit, the satellite launch enable flag is set. The enable flag triggers the BeiDou short message protocol encapsulation engine, performing byte compression and forward error correction encoding on the positioning coordinates and additional text information.

[0139] The encoded data generates an RF signal via a binary phase-shift keying modulator, with the carrier frequency precisely locked at 1615.68MHz. The transmission process employs phased power control: initially, a low-gain receive mode is configured to detect signal quality; once link stability is confirmed, the mode switches to high-gain transmit mode. Upon successful transmission, a BeiDou transmission identifier is generated, containing a communication confirmation flag, transmit power level, and bit error rate statistics. The identifier data is appended with a timestamp accurate to the millisecond level.

[0140] AIS completes the identification resolution of the ship's receiving terminal's real-time position and heading data, extracting information including latitude and longitude coordinates, speed vector, and shipboard rescue resource type. DSC response data decodes the dispatch instructions forwarded by the shore-based base station, resolving the coast guard deployment coordinates, rescue unit type, and estimated response time. BeiDou transmits identification to extract communication confirmation frames returned by the satellite ground station, verifies the FKI flag bit as a 0xAA success code, and records the satellite positioning accuracy factor. A three-way data input spatiotemporal alignment engine: uses UTC timestamps for millisecond-level event synchronization and unifies the spatial reference through WGS-84 coordinate system transformation. The aggregation process executes multi-level decision logic:

[0141] Priority ranking: The real-time location of the vessel is given the highest response weight, followed by the coast guard dispatch instructions, and satellite confirmation information is used as auxiliary verification; Resource matching: The vessel's ETA (Estimated Time of Arrival) is dynamically calculated based on the coordinates of the point of impact, and the configuration status of the onboard lifeboats is associated; Conflict resolution: When multiple rescue units cover the same area, the responsibility area is automatically assigned according to the timeliness of the response.

[0142] Generate a joint dispatch information package, which includes a gridded deployment map of the target sea area, dynamic path planning for rescue units, and a resource allocation list. The data format conforms to the emergency response protocol.

[0143] The joint dispatch information input task distribution engine transmits in parallel through multi-mode communication links: AIS broadcast link: sends binary command frames (message type 27) to the target vessel, containing rescue coordinates and a list of cooperating vessels' MMSIs; DSC command link: sends distress transfer instructions to the coast guard base station, triggering a ship / helicopter deployment sequence; Beidou satellite link: sends a structured deployment plan to the rescue center, along with voice navigation instructions and real-time images of the crash site.

[0144] The rescue terminal's execution status is transmitted back to the feedback collector in real time: the ship's AIS terminal continuously reports its location and trajectory, the coast guard unit sends action status codes through the GMDSS system, and the rescue center updates the mission progress timeline. The feedback data is weighted and fused based on confidence level: ship trajectory: assigned a high confidence coefficient, real-time correction of the ETA model; coast guard status code: assigned a medium confidence coefficient, triggering resource reallocation; center timeline: assigned a low confidence coefficient, used for accountability tracing.

[0145] Dynamically fused and generated rescue response information includes real-time location heatmaps of rescue units, phased task completion assessments, and final rescue success indicators.

[0146] This embodiment significantly improves the triggering reliability of the device under harsh sea conditions by using hardware-level fusion and duration verification mechanisms for multi-source trigger signals, avoiding false alarms caused by interference from a single signal. Voltage locking and state initialization coordinated control ensure stable power supply to the positioning and communication units, guaranteeing the validity of high-precision positioning data. The dynamic configuration strategy of the three-mode communication resources enables on-demand activation of the AIS, DSC, and BeiDou systems, significantly reducing overall power consumption while maintaining full sea area coverage.

[0147] Reference Figure 3 As shown, in one embodiment, based on a preset second transmission time, the MOB device performs carrier modulation output and response monitoring on the DSC distress signal to obtain DSC response data, including:

[0148] When the main control MCU's status parsing unit recognizes that the preset second transmission time has been reached, it extracts the transmission termination timestamp and spectrum release flag. The status data input enables the decision logic: when the AIS transmission counter value is ≥8 and the RF channel idle flag is set, the DSC enable instruction generation circuit is triggered. The enable instruction includes a carrier modulation start command, a listening status activation code, and priority parameters, and is written to the DSC control register group via a 32-bit data bus. The instruction transmission process uses a hardware handshake protocol to ensure that DSC system initialization is completed within 2 milliseconds after AIS transmission ends. The enable instruction also resets the DSC module's status register, clears historical buffer data, and provides a clean initial environment for modulation output and response listening.

[0149] The direct memory access controller loads the base address of the 1300Hz / 2100Hz sine wave table, timer TIM1 configures the baud rate period, and the TIM2 reload register dynamically switches the carrier frequency parameters according to the geographic information stream bit value. The modulated signal is converted into a stepped waveform by a digital-to-analog converter, and then smoothed by a fourth-order Chebyshev filter to output an RF signal conforming to the spectrum template. Simultaneous activation of dual-channel monitoring mode: the RF switch switches to receive mode, the low-noise amplifier gain is increased to 30dB, and the dedicated demodulation chip initializes the preamble matching template. The monitoring status flag is written to the system control register, the monitoring window timer is started, and the channel response signal is monitored in real time.

[0150] The preset listening duration is configured in a window timer, and the timer overflow signal triggers a listening termination interrupt. During listening, the timer capture unit records the timestamps of the input signal transitions in real time, and the time difference between adjacent transitions is used to calculate the symbol width. The calculation result is compared with the 833-microsecond standard symbol period: when the actual symbol width consistently falls within the preset tolerance range, a valid symbol marker is generated. A timestamp and confidence coefficient are appended to the marker data to form a structured valid symbol marker sequence. The sequence data is stored in a circular buffer for subsequent use by the protocol parsing engine.

[0151] The preset preamble sequence "10101010" is stored in the reference register of the synchronization detection unit, and the valid symbol marker sequence is input to the shift register for serial-to-parallel conversion. The detection process performs clock recovery and phase alignment: a phase-locked loop circuit tracks the symbol transition edges to compensate for phase shifts caused by transmission delays. The aligned data stream and the reference preamble are compared bit-by-bit with a Hamming distance calculation. A preamble matching success flag is generated when the difference in the number of bits is ≤1. A synchronization quality coefficient (calculated based on the number of consecutive matching bits) is added to the matching result to form the preamble matching result.

[0152] The preamble matching result triggers protocol parsing. The DSC response data is input to the frame structure decomposer: the address field is extracted to verify the device identification code matching, and the data payload fields are separated for verification. Data packets that pass verification undergo distress response type identification: the confirmation frame identifier matches a preset distress confirmation code, and the location coordinates and timestamp are verified for reasonableness. The parsing result is encapsulated as DSC response confirmation data, including the source device identification code, response type code, and location verification flag. Finally, the DSC response confirmation data is written to the system response queue, appending the parsing timestamp and error statistics.

[0153] This embodiment achieves seamless switching between DSC modulation transmission and response monitoring through master control at the instruction level, significantly improving the response timeliness of the distress call system. Signal feature extraction technology based on symbol width analysis effectively filters sea clutter interference, ensuring accurate identification of symbol duration. A preamble Hamming distance fault-tolerant verification strategy enhances protocol synchronization robustness under harsh sea conditions, increasing communication success rate threefold in sudden interference scenarios. The spatiotemporal rationality verification architecture of the response parsing engine eliminates false alarm signals at their source.

[0154] In one embodiment, based on a preset third transmission time, the MOB device performs signal strength threshold verification and satellite link triggering on the BeiDou alarm signal to obtain a BeiDou transmission identifier, including:

[0155] When the sleep duration monitoring unit detects that the preset third transmission time has been reached, it parses the response timestamp and calculates the idle duration of the module by comparing it with the current UTC time. The idle duration input window comparator performs a logical judgment with the preset sleep threshold: when the continuous inactivity duration is ≥6 seconds, a sleep flag status code is generated. This flag triggers the wake-up decision engine to perform a two-condition verification: if the sleep flag is valid and a DSC response completion command is received, or if the sleep duration reaches the limit threshold, the wake-up request flag is set. The wake-up command construction process integrates a negative feedback compensation design, using a temperature sensor to correct timing errors caused by crystal oscillator drift in real time, ensuring wake-up timing accuracy ≤0.1%. The finally generated module wake-up command includes a hardware reset command, clock calibration parameters, and power level configuration words, which are transmitted to the power management unit via a high-speed serial bus.

[0156] The RDSS module wake-up command trigger includes a multi-level power enable sequence of level 1, level 2, and level 3 enable. Real-time power supply status monitoring: A digital voltage monitor collects voltage samples from each node, and an RF power detector measures the local oscillator signal strength. When all power supply parameters remain stable within the safety threshold for 200ms, the module readiness flag is set. This flag includes the power quality coefficient, local oscillator lock flag, and startup timestamp, and is written to the system status register group. After the readiness flag is generated, a self-test program is automatically triggered to verify the integrity of the baseband processor instruction set.

[0157] The module readiness flag is input to the channel quality assessment engine, which analyzes in real time the historical signal strength curves, carrier lock status, and bit error rate statistics. The assessment process performs a two-dimensional threshold decision:

[0158] Signal strength dimension: Calculate the moving average of the instantaneous signal-to-noise ratio of the L-band signal, and generate a strength compliance flag when 5 consecutive sampling points exceed the preset strength threshold;

[0159] Time dimension: The duration of monitoring signal capture is such that a timeout permission flag is generated when the preset waiting limit (6 seconds) is reached.

[0160] Activation of any flag triggers the launch clearance flag to be set. The flag data includes an environmental adaptability factor: the intensity threshold tolerance range is dynamically adjusted based on temperature and humidity sensor data (with a 3dB relaxation in surge environments) to enhance adaptability to complex sea conditions. The final launch clearance flag includes the real-time link quality index, frequency offset compensation value, and recommended transmit power value, and is transmitted to the satellite communication coprocessor.

[0161] The launch clearance marker triggers the carrier synchronization control sequence: the phase-locked loop circuit configures the local oscillator based on the frequency point, and compensates for frequency deviation caused by temperature drift through the automatic frequency control loop. After carrier lock, the BeiDou short message protocol encapsulation is performed: the positioning coordinates are converted to geodetic coordinate system binary encoding, distress type identifier and check code are added, and the compressed text information uses Huffman coding to reduce bandwidth usage. The encapsulated data stream is input to the BPSK modulator: the baseband signal is passed through a raised cosine pulse shaping filter to generate I / Q quadrature components, and the quadrature modulator shifts the baseband signal to the L-band carrier. The launch process implements phased power control: in the initial stage, a 10dBm low-gain mode is configured to detect link quality, and after confirming carrier synchronization, it switches to a high-gain launch mode. The RF signal is filtered by a surface acoustic wave filter to suppress out-of-band spurious signals, and the output is a modulated signal that conforms to the power spectral density template. After launch, a satellite transmission status frame is generated, including the launch timestamp, actual launch power value, and carrier synchronization quality coefficient.

[0162] The satellite transmission status frame input protocol parsing engine extracts the frame synchronization header from the downlink response signal using a matched filter. Upon successful synchronization, the FKI (Communication Acknowledgment Flag) field is located, and binary decoding is performed: if the FKI value equals the preset success code (0xAA), the communication success flag is set; otherwise, an error type code (0x55 timeout / 0xCC check failure) is detected. The parsing process includes a quality assessment: a carrier-to-noise ratio analyzer calculates the downlink signal-to-noise ratio, and an error rate statistician records the number of consecutive error frames. The parsing result is encapsulated as a BeiDou transmission identifier, containing the communication status code (success / failure / retry), downlink signal quality index (0-100), and satellite time stamp. The identifier data is written to non-volatile memory with added cyclic redundancy check protection for use by the rescue response aggregation system.

[0163] This embodiment achieves precise hardware-level control of the FSK modulation process through a dual-timer coordinated carrier dynamic switching mechanism. This ensures crosstalk-free carrier signals and output spectral purity that meets stringent maritime communication standards. The hard synchronization design of the bitstream and time base brings the symbol duration error close to zero, significantly improving the signal resolution success rate at the receiver. The end-to-end hardware acceleration architecture reduces overall power consumption to one-third of traditional solutions, extending continuous operation time in emergency situations.

[0164] Reference Figure 4As shown, the present invention also provides a search and rescue system based on AIS and BeiDou RDSS, applicable to any of the above-mentioned search and rescue methods based on AIS, DSC, and BeiDou RDSS, comprising:

[0165] The acquisition module is used to continuously acquire multi-source trigger signals from the MOB device, construct instructions, and obtain alarm activation instructions.

[0166] The analysis module is used to obtain BeiDou positioning coordinates according to the alarm activation command, and to initialize and activate the communication unit to obtain multi-mode communication unit information.

[0167] The association module is used to construct three-mode signals based on positioning coordinates and multi-mode communication unit information to obtain AIS broadcast signals, DSC distress signals and Beidou alarm signals.

[0168] The processing module is used to prioritize and coordinate the transmission of AIS broadcast signals, DSC distress signals, and Beidou alarm signals through the MOB device to obtain rescue response information.

[0169] This application provides a search and rescue system based on AIS and BeiDou RDSS. By constructing instructions from multi-source trigger signals and coordinating the activation of multi-mode communication units, it effectively solves the coverage blind spot problem of a single communication system, significantly improving the global transmission reliability of distress signals in complex sea areas. The priority-based multi-mode signal transmission and coordinated response mechanism overcomes the shortcomings of traditional DSC or AIS signals, which are susceptible to channel congestion or obstruction interference, achieving efficient redundant transmission and accurate delivery of distress information. By integrating the advantages of BeiDou RDSS positioning and AIS / DSC communication, it improves positioning accuracy while achieving multi-system complementary fault tolerance, reducing the risk of partial equipment failure and enhancing the overall robustness of the search and rescue system. Relying on dynamic scheduling and resource optimization of multi-mode signals, it achieves efficient coordination of distress information in time, space, and spectrum dimensions, significantly shortening rescue response time and improving the overall effectiveness of maritime search and rescue operations.

[0170] Regarding the system in the above embodiments, the specific manner in which each module performs its operations has been described in detail in the embodiments of the apparatus in the above embodiments, and the specific manner in which each module performs its operations has been described in detail in the embodiments of the method, and will not be elaborated further here.

[0171] The solution of this application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of each embodiment have different emphases; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. Those skilled in the art should also understand that the actions and modules involved in the specification are not necessarily essential to this application. Furthermore, it is understood that the steps in the method of this application embodiment can be adjusted, combined, and deleted according to actual needs, and the modules in the device of this application embodiment can be combined, divided, and deleted according to actual needs.

[0172] Furthermore, the method according to this application can also be implemented as a computer program or computer program product, which includes computer program code instructions for performing some or all of the steps in the method described above.

[0173] Alternatively, this application may be implemented as a non-transitory machine-readable storage medium (or computer-readable storage medium, or machine-readable storage medium) storing executable code (or computer program, or computer instruction code) thereon, which, when executed by a processor of an electronic device (or electronic device, server, etc.), causes the processor to perform part or all of the steps of the methods described above according to this application.

[0174] Those skilled in the art will also understand that the various exemplary logic blocks, modules, circuits, and algorithm steps described in connection with the present application can be implemented as electronic hardware, computer software, or a combination of both.

[0175] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems and methods according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0176] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A search and rescue method based on AIS, DSC, and BeiDou RDSS, characterized in that, include: Continuously acquire multi-source trigger signals from MOB devices, construct instructions, and obtain alarm activation instructions; According to the alarm activation command, the BeiDou positioning coordinates are obtained, and the communication unit is initialized and activated to obtain the multi-mode communication unit information; Based on the positioning coordinates and the multi-mode communication unit information, a three-mode signal is constructed to obtain the AIS broadcast signal, the DSC distress signal and the Beidou alarm signal; The MOB device prioritizes and coordinates the transmission and response of the AIS broadcast signal, the DSC distress signal, and the Beidou alarm signal to obtain rescue response information. The process of obtaining BeiDou positioning coordinates according to the alarm activation command and initializing and activating the communication unit to obtain multi-mode communication unit information includes: Based on the alarm activation command, the circuit status of the MOB device is verified to obtain a power enable signal; Based on the power enable signal, the positioning data is calculated by the BeiDou RNSS module of the MOB device to obtain the BeiDou positioning coordinates. Based on the BeiDou positioning coordinates, the AIS module of the MOB device is configured with radio frequency timing to obtain AIS channel control information; Based on the BeiDou positioning coordinates, the DSC module of the MOB device is subjected to protocol encoding and carrier parameter mapping to obtain a dual-frequency FSK modulation configuration table. The BeiDou positioning coordinates are activated to obtain a link ready identifier by activating the BeiDou RDSS communication status. The AIS channel control information, the dual-frequency FSK modulation configuration table, and the link ready identifier are integrated into multi-mode information to obtain the multi-mode communication unit information. The construction of three-mode signals based on the positioning coordinates and the multi-mode communication unit information yields AIS broadcast signals, DSC distress signals, and BeiDou alarm signals, including: Based on the positioning coordinates, modulation parameters are loaded into the AIS channel control information of the multimode communication unit information to obtain radio frequency generation instructions; The AIS module is signal-driven and constructed according to the radio frequency generation instructions to obtain the AIS broadcast signal; Based on the positioning coordinates, the dual-frequency FSK modulation configuration table of the multi-mode communication unit information is mapped to a sinusoidal table address, and the DSC module is triggered in distress to obtain the DSC distress signal; The satellite communication status is verified by the link readiness identifier to obtain the channel availability flag; Based on the channel availability marker, the BeiDou positioning coordinates are modulated and encoded to obtain the BeiDou alarm signal; The process of mapping the dual-frequency FSK modulation configuration table based on the positioning coordinates to the address of the multi-mode communication unit information using a sine wave table, and triggering the DSC module to obtain the DSC distress signal, includes: The sine wave table of the dual-frequency FSK modulation configuration table is subjected to dual-frequency FSK modulation to output a first encoding frequency and a second encoding frequency, wherein the encoding of the first encoding frequency is 0 and the frequency is 2100Hz, and the encoding of the second encoding frequency is 1 and the frequency is 1300Hz. The timer reload value of the MOB device is dynamically modified according to the first encoding frequency and the second encoding frequency, and the corresponding frequency sine wave is output. The location coordinates are processed using DSC distress protocol encoding to obtain a geographic information stream; Based on the geographic information stream, the timer reload register of the MOB device is dynamically switched to obtain the carrier frequency selection parameters. The frequency sine waveform is addressed in real time based on the carrier frequency selection parameters to obtain the DSC distress signal.

2. The search and rescue method based on AIS, DSC, and BeiDou RDSS according to claim 1, characterized in that, The continuous acquisition of multi-source trigger signals from the MOB device and the construction of instructions to obtain an alarm activation instruction include: The physical buttons of the MOB device are subjected to level-triggered conversion of input signals to obtain button trigger signals; Short-circuit feature detection is performed on the water fall detection terminal of the MOB device to obtain a water fall event identifier; The MOB device is parsed using the Bluetooth terminal protocol to obtain the terminal control signal; The button trigger signal, the water-falling event identifier, and the terminal control signal are fused together to obtain the multi-source trigger signal. The multi-source triggering signals are logically compared based on a preset duration threshold to obtain a valid triggering flag. The MOB device is voltage locked and status initialized based on the valid trigger flag, and the alarm activation command is obtained.

3. The search and rescue method based on AIS, DSC, and BeiDou RDSS according to claim 1, characterized in that, The process of prioritizing and coordinating the transmission and response of the AIS broadcast signal, the DSC distress signal, and the BeiDou alarm signal through the MOB device to obtain rescue response information includes: Based on a preset first transmission time, the AIS broadcast signal is transmitted via radio frequency control through the MOB device to obtain an AIS completion identifier; Based on a preset second transmission time, the MOB device performs carrier modulation output and response monitoring on the DSC distress signal to obtain DSC response data. Based on the preset third launch time, the MOB device performs signal strength threshold verification and satellite link triggering on the BeiDou alarm signal to obtain the BeiDou transmission identifier; The AIS completion identifier, the DSC response data, and the BeiDou transmission identifier are aggregated to obtain joint scheduling information. The rescue terminal receives the task response based on the joint scheduling information and obtains the rescue response information.

4. The search and rescue method based on AIS, DSC, and BeiDou RDSS according to claim 3, characterized in that, The MOB device performs carrier modulation output and response monitoring on the DSC distress signal based on a preset second transmission time to obtain DSC response data, including: Based on the AIS completion identifier, a DSC enable command is generated by the main control MCU of the MOB device; According to the DSC enable command, the MOB device performs carrier modulation output and activates the DSC listening state; In the DSC listening state, the MOB device captures DSC response data according to the preset listening duration and performs symbol width analysis to obtain valid symbol markers; Based on a preset preamble sequence, the effective symbol marker is subjected to preamble synchronization detection to obtain a preamble matching result. The response content of the DSC response data is parsed based on the preamble matching result to obtain the DSC response confirmation data.

5. The search and rescue method based on AIS, DSC, and BeiDou RDSS according to claim 3, characterized in that, Based on a preset third launch time, the MOB device performs signal strength threshold verification and satellite link triggering on the BeiDou alarm signal to obtain a BeiDou transmission identifier, including: Based on the DSC response data, the MOB device is monitored for module sleep duration to obtain a sleep identifier, and a wake-up command is constructed to obtain a module wake-up command. The module wake-up command is used to enable hardware power supply to the MOB device, and a module ready flag is obtained. Launch license identification is performed based on the module readiness identifier to obtain a launch license marker; Based on the launch permission mark, satellite link triggering and BeiDou short message transmission operations are performed to obtain satellite transmission status frames; The FKI flag bit is parsed on the satellite transmission status frame to obtain the BeiDou transmission identifier.

6. A search and rescue system based on AIS and BeiDou RDSS, characterized in that, The search and rescue method based on AIS, DSC, and BeiDou RDSS applied to any one of claims 1-5 includes: The acquisition module is used to continuously acquire multi-source trigger signals from the MOB device, construct instructions, and obtain an alarm activation instruction. The analysis module is used to obtain BeiDou positioning coordinates according to the alarm activation command, and to initialize and activate the communication unit to obtain multi-mode communication unit information. The association module is used to construct three-mode signals based on the positioning coordinates and the multi-mode communication unit information to obtain AIS broadcast signal, DSC distress signal and Beidou alarm signal; The processing module is used to prioritize and coordinate the transmission of the AIS broadcast signal, the DSC distress signal, and the Beidou alarm signal through the MOB device to obtain rescue response information.

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