A search coordination communication system and method for multiple people in distress in a water area

Abstract

The application discloses a search cooperative communication system and method for multi-person water area distress, comprising a plurality of search and rescue operation platforms, receiving devices and a search and rescue command platform; the plurality of search and rescue operation platforms are used for sending ranging and direction finding interrogation signals and acquiring signals sent by the receiving devices, and the ranging and direction finding results of the receiving devices are obtained by a direction finding method and sent to the command device; the receiving device is used for receiving the ranging and interrogation signals and filling in local time stamps and identity information in the response information, and sending the ranging response signals at a predetermined frequency point; the search and rescue command platform is used for forming a search and rescue operation scheme according to the received ranging and direction finding results, and broadcasting and sending to each search and rescue operation platform at sea; and the application adopts time division or frequency division to optimize, organize and dispatch the sequence of search positioning waveforms sent by the search and rescue operation platforms, reduces the mutual collision probability of the search positioning signals and improves the search positioning communication efficiency.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a collaborative communication system and method for searching multiple people in distress in water. Background Technology

[0002] Currently, in maritime emergencies in my country, systems capable of efficiently searching for and locating large numbers of people in distress are needed to address situations such as ship capsizing, sinking, and mass casualties. This is crucial for supporting subsequent rescue efforts. Search and location capabilities primarily include direction finding and ranging capabilities for distressed targets, specifically:

[0003] 1) Direction finding technology

[0004] Direction finding technology refers to determining the spatial orientation of a distressed target relative to the search and rescue team. For far-field signals, there will be a time delay when the signal from the same target arrives at different array elements, and this time delay corresponds to the phase difference between the different array elements.

[0005] like Figure 1 As shown, assuming in If there is a distant target in the direction of the antenna, and the distance between the antennas is d, then the path difference of the received signals is:

[0006]

[0007] The resulting phase difference is:

[0008]

[0009] In the above formula, The wavelength is [wavelength]. If the phase difference between array elements can be measured using a phase meter, these phase differences can be used to determine the target's orientation. In simple terms, this is the most basic principle of target orientation estimation. Commonly used methods for target orientation include: Watson-Watt orientation finding, MUSIC algorithm orientation finding, etc.

[0010] 2) Distance measurement technology

[0011] Ranging refers to determining the relative distance between a distressed target and the search and rescue team. Ranging techniques can be categorized by the path of radio wave transmission into two-way ranging and one-way ranging. Two-way ranging means the radio wave travels back and forth along the measured distance once, i.e., the radio wave travels twice the measured distance. One-way ranging means the radio wave travels only once along the measured distance, i.e., it travels a single path. Based on the electrical signal system, it can be classified into pulse ranging, frequency ranging, phase ranging, and code-correlated ranging. The technical principles are as follows:

[0012] a) Pulse ranging: Using pulse signals or their codes to measure the propagation delay of electromagnetic waves from one point to another, thereby calculating the distance between the two points.

[0013] b) Frequency-based ranging: Utilizing a specific functional relationship between the frequency of a time-varying frequency source and time. The change in frequency of the source during the propagation of radio waves from one point to another. To measure the distance between two points.

[0014] c) Phase-based ranging: This method uses the phase delay of an electrical signal during its propagation from one point to another to measure the distance between two points.

[0015] d) Code correlation ranging: The distance between two points is measured by measuring the code sequence delay correlation from one point to another using pseudocode sequences with excellent correlation properties.

[0016] As can be seen from the above analysis, when multiple maritime rescue platforms conduct coordinated search and rescue for the same distressed target, the maritime search and rescue operation platform (ship / aircraft) needs to conduct ranging and direction finding communication with the distressed target on the same frequency band. The ranging and direction finding signals sent by multiple search and rescue operation platforms are at risk of colliding with each other, which can easily lead to mutual interference, resulting in invalid direction finding and reducing search efficiency. Summary of the Invention

[0017] The technical problem solved by this invention is to provide a collaborative communication system for searching and locating multiple people in distress at sea, which can solve the problem of signal collisions that easily occur when multiple platforms carry out maritime search and positioning missions.

[0018] The technical solution adopted by the present invention to solve its technical problem is: a search and rescue collaborative communication system for multiple people in distress in water, including multiple search and rescue operation platforms, receiving devices and search and rescue command platforms;

[0019] Multiple search and rescue operation platforms are used to send ranging and direction finding inquiry signals and obtain signals sent by receiving devices, and obtain the direction finding and ranging results of each receiving device through direction finding methods and send them to the command device;

[0020] The receiving device is used to receive ranging and interrogation signals and fill in local timestamps and identity information in the response information, and send ranging response signals at a predetermined frequency.

[0021] The search and rescue command platform is used to integrate and converge the received direction finding and ranging results to form the relative positional relationship between the distressed target and the search and rescue operation platform at the search and rescue site, and to form a rescue command operation plan, which is then broadcast to each search and rescue operation platform at sea.

[0022] Furthermore, the search and rescue command platform is used to send broadcast time slots and allocate time slots to the search and rescue operation platform;

[0023] The search and rescue operation platform is used to send access request information in the access time slots allocated by the search and rescue command platform.

[0024] This invention also discloses a collaborative communication method for searching multiple people in distress in water, the steps of which are as follows:

[0025] S100: The search and rescue operation platform uses frequency division multiplexing or time division multiplexing to send ranging and direction finding interrogation signals;

[0026] S200: The distressed target fills in the local timestamp and response information in the response information and sends a ranging response signal at a predetermined frequency.

[0027] S300: The distressed target transmits direction-finding beacon signals on other frequencies;

[0028] S400: Each search and rescue operation platform receives ranging response signals and direction finding beacon signals, and calculates its relative distance and relative direction with the distressed target;

[0029] S500: Each search and rescue operation platform sends direction-finding distance and results to the search and rescue command platform via its own frequency;

[0030] S600: The search and rescue command platform receives direction finding distance and results, and after merging and aggregating them, forms the relative positional relationship between the distressed target and the search and rescue operation platform at the search and rescue site;

[0031] S700: The search and rescue command platform formulates a search and rescue command plan and broadcasts it to each search and rescue operation platform.

[0032] S800: Each search and rescue operation platform receives the search and rescue command plan and carries out rescue operations.

[0033] Furthermore, in step S100, the search and rescue operation platform uses frequency division multiplexing to send ranging and direction finding interrogation signals, specifically:

[0034] S101: Assign ID numbers to each search and rescue operation platform;

[0035] S102: Each search and rescue operation platform sends ranging inquiry signals, direction finding inquiry signals, and its own platform ID signal to the distressed target according to differentiated communication frequencies;

[0036] S103: The distressed target uses a wide-spectrum receiving method to receive ranging and interrogation signals.

[0037] Furthermore, in step S100, the search and rescue operation platform uses time-division multiplexing to send ranging and direction-finding interrogation signals, specifically as follows:

[0038] S101: Assign ID numbers to each search and rescue operation platform;

[0039] S102: The search and rescue command platform sends a broadcast time slot, and the search and rescue operation platform approaching the accident site receives the information sent by the broadcast time slot and sends an access request information in the access time slot;

[0040] S103: After receiving the access request information, the search and rescue command platform allocates a time slot to the search and rescue operation platform and sends it in the broadcast time slot;

[0041] S104: Each search and rescue operation platform sends ranging inquiry signals, direction finding inquiry signals, and its own platform ID signal according to the pre-allocated time slots.

[0042] S105: The distressed target uses a wide-spectrum receiving method to receive ranging and interrogation signals.

[0043] Furthermore, it also includes the following steps: S900: The search and rescue command platform schedules time slot resources according to the signal strength received by each search and rescue operation platform, and allocates more time slot resources to the platform with better search and detection signal reception effect through time slot control commands according to the detection cycle P.

[0044] Furthermore, in step S900, specifically:

[0045] Let N be the total number of search and rescue operation platforms participating in the search and rescue. The time slots allocated to the search and rescue operation platform M1 Let (x=1,2,…N) be the number of service time slots allocated to search and rescue operation platform Mx. Within a preset time period, the average signal quality received by each search and rescue operation platform is RSSI. n (n=M1,M2,…M) n ), The average signal quality received by search and rescue platform M1. Given the average signal quality received by search and rescue platform Mx, the total number of time slots to be allocated is T. total ;

[0046] S901: Each search and rescue platform sends an inquiry signal to the distressed target, respectively. , … ;

[0047] S902: Each search and rescue platform receives the response signal sent by the distressed target and obtains the signal quality RSSI by measuring the received signal. n The measurement results were then sent to the search and rescue command platform.

[0048] S903: Based on the signal quality RSSIn (n=M1,M2,…M) received by each search and rescue operation platform from all search and rescue operation platforms, RSSIn is calculated. n To allocate initial time slots to each search and rescue platform, first allocate time slots to the search and rescue platform with the best signal quality among those currently awaiting allocation. Assuming search and rescue platform M1 has the best average signal quality, then the number of time slots allocated is... ;in, This is an adjustment factor, and its value range is [ , ];

[0049] S904: Based on signal average quality RSSI n From highest to lowest quality, select the platform M with the best received signal quality from the platforms that have never been allocated time slot resources. x If the remaining time slots are allocated, then the number of time slots allocated is... for:

[0050] ;

[0051] in, This is an adjustment factor, and its value range is [0, 1].

[0052] S905: And so on, allocating corresponding time slot resources to all platforms until all platforms or time slot resources have been allocated.

[0053] Furthermore, in step S400, each search and rescue platform receives ranging response signals and direction-finding beacon signals, and calculates its relative distance and relative direction with the distressed target, specifically as follows:

[0054] Each search and rescue platform receives the ranging response signal and direction finding beacon signal sent by the distressed target, extracts the timestamp marked in the ranging response signal, and calculates the relative distance between the search and rescue platform and the distressed target; based on the direction of arrival of the direction finding beacon signal, the amplitude comparison direction finding method or the MUSIC direction finding method is used to determine the heading of the distressed target relative to its respective search and rescue platform.

[0055] The beneficial effects of this invention are: This invention optimizes and schedules the order in which search and rescue operation platforms send search and positioning waveforms using time-division or frequency-division methods, thereby reducing the probability of collisions between search and positioning signals and improving search and positioning communication efficiency. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the collaborative search waveform allocated according to time slots in an embodiment of this application.

[0057] Figure 2 This is a flowchart illustrating the scheduling method for collaborative search and positioning signals using frequency division multiplexing in this embodiment of the application.

[0058] Figure 3 This is a flowchart illustrating the scheduling method for collaborative search and positioning signals using time-division multiplexing in this embodiment of the application.

[0059] Figure 4This is a flowchart illustrating the time slot resource reuse method under the time-division multiplexing scheduling method for collaborative search and positioning signals in the embodiments of this application. Detailed Implementation

[0060] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0061] The embodiments of this application disclose a search and rescue collaborative communication system for multiple people in distress in water, including multiple search and rescue operation platforms, receiving devices and search and rescue command platforms;

[0062] Multiple search and rescue operation platforms are used to send ranging and direction finding inquiry signals and obtain signals sent by receiving devices, and obtain the direction finding and ranging results of each receiving device through direction finding methods and send them to the command device;

[0063] The receiving device is used to receive ranging and interrogation signals and fill in local timestamps and identity information in the response information, and send ranging response signals at a predetermined frequency.

[0064] The search and rescue command platform is used to integrate and converge the received direction finding and ranging results to form the relative positional relationship between the distressed target and the search and rescue operation platform at the search and rescue site, and to form a rescue command operation plan, which is then broadcast to each search and rescue operation platform at sea.

[0065] Specifically, the search and rescue command platform can also be used to send broadcast time slots and allocate time slots to search and rescue operation platforms;

[0066] The search and rescue operation platform can also be used to send access request information in the access time slots allocated by the search and rescue command platform.

[0067] Specifically, in the aforementioned system, either frequency division multiplexing (FDM) or time division multiplexing (TDM) methods can be used to transmit ranging and direction finding interrogation signals. When using FDM, each search and rescue platform is first assigned a unique ID number to ensure signal identification. Subsequently, each search and rescue platform sends ranging, direction finding, and its own ID signal to the distressed target according to a pre-allocated differentiated communication frequency. The distressed target uses a wide-spectrum reception method to ensure accurate reception of signals from different search and rescue platforms.

[0068] When using time-division multiplexing, the search and rescue command platform first broadcasts time slot information. Search and rescue operation platforms approaching the accident site receive this information and then send access request information in their designated access time slots. Upon receiving these requests, the search and rescue command platform allocates time slots to the corresponding search and rescue operation platforms and broadcasts the allocation results. Subsequently, each search and rescue operation platform sequentially sends ranging interrogation signals, direction-finding interrogation signals, and its own platform ID signal according to the pre-allocated time slots. Similarly, the distressed target also receives these signals using a wide-spectrum reception method.

[0069] Next, upon receiving the ranging and inquiry signals, the receiving device quickly fills in a precise local timestamp and unique identification information in the response information to ensure data accuracy and traceability. Subsequently, the receiving device promptly transmits ranging response signals on a predetermined frequency, enabling the search and rescue platform to accurately obtain the relative distance information to the distressed target. Using these signals, the search and rescue platform can calculate the relative distance and direction to the distressed target. After receiving the direction-finding and ranging results from each search and rescue platform, the search and rescue command platform performs fusion and convergence processing to establish the relative positional relationship between the distressed target and the search and rescue platforms at the search and rescue site, and formulates a scientifically sound search and rescue command plan to ensure the efficient and orderly conduct of the rescue operation.

[0070] The design of the aforementioned system effectively avoids signal collisions and interference during collaborative search and rescue operations involving multiple search and rescue platforms, improving the accuracy and efficiency of ranging and direction finding. Through frequency division multiplexing or time division multiplexing, it ensures that signals transmitted by each search and rescue platform are transmitted clearly and orderly, without interference from other platforms. This allows for the determination of the relative positions of the search and rescue platforms, enabling the development of scientifically sound search and rescue command and control plans, effectively guiding each platform in its rescue operations, and significantly improving rescue efficiency and success rates.

[0071] This invention also discloses a collaborative communication method for searching multiple people in distress in water, which has the following two specific embodiments:

[0072] Example 1: As Figure 1 and 2 As shown, the search and rescue operation platform uses frequency division multiplexing:

[0073] S101: Assign ID numbers to each search and rescue operation platform;

[0074] S102: Each search and rescue operation platform sends ranging inquiry signals, direction finding inquiry signals, and its own platform ID signal to the distressed target according to differentiated communication frequencies;

[0075] S103: The distressed target uses a wide-spectrum receiving method to receive ranging and interrogation signals.

[0076] S200: The distressed target fills in the local timestamp and response information in the response information and sends a ranging response signal at a predetermined frequency.

[0077] S300: The distressed target transmits direction-finding beacon signals on other frequencies;

[0078] S400: Each search and rescue operation platform receives ranging response signals and direction finding beacon signals, and calculates its relative distance and relative direction with the distressed target;

[0079] S500: Each search and rescue operation platform sends direction-finding distance and results to the search and rescue command platform via its own frequency;

[0080] S600: The search and rescue command platform receives direction finding distance and results, and after merging and aggregating them, forms the relative positional relationship between the distressed target and the search and rescue operation platform at the search and rescue site;

[0081] S700: The search and rescue command platform formulates a search and rescue command plan and broadcasts it to each search and rescue operation platform.

[0082] S800: Each search and rescue operation platform receives the search and rescue command plan and carries out rescue operations.

[0083] Example 2: Figure 3 As shown, the search and rescue operation platform adopts a time-division multiplexing method:

[0084] S101: Assign ID numbers to each search and rescue operation platform;

[0085] S102: The search and rescue command platform sends a broadcast time slot, and the search and rescue operation platform approaching the accident site receives the information sent by the broadcast time slot and sends an access request information in the access time slot;

[0086] S103: After receiving the access request information, the search and rescue command platform allocates a time slot to the search and rescue operation platform and sends it in the broadcast time slot;

[0087] S104: Each search and rescue operation platform sends ranging inquiry signals, direction finding inquiry signals, and its own platform ID signal according to the pre-allocated time slots.

[0088] S105: The distressed target uses a wide-spectrum receiving method to receive ranging and interrogation signals.

[0089] S200: The distressed target fills in the local timestamp and response information in the response information and sends a ranging response signal at a predetermined frequency.

[0090] S300: The distressed target transmits direction-finding beacon signals on other frequencies;

[0091] S400: Each search and rescue operation platform receives ranging response signals and direction finding beacon signals, and calculates its relative distance and relative direction with the distressed target;

[0092] S500: Each search and rescue operation platform sends direction-finding distance and results to the search and rescue command platform via its own frequency;

[0093] S600: The search and rescue command platform receives direction finding distance and results, and after merging and aggregating them, forms the relative positional relationship between the distressed target and the search and rescue operation platform at the search and rescue site;

[0094] S700: The search and rescue command platform formulates a search and rescue command plan and broadcasts it to each search and rescue operation platform.

[0095] S800: Each search and rescue operation platform receives the search and rescue command plan and carries out rescue operations.

[0096] Both of the aforementioned search and rescue methods fully consider the complexity and variability of multi-person water-based distress scenarios. Through collaborative communication technology, they achieve effective information exchange between the search and rescue operation platform and the distressed target, as well as between the search and rescue command platform and each search and rescue operation platform. Frequency division multiplexing (FDM) avoids signal interference by allocating different communication frequencies to each search and rescue operation platform, ensuring accurate transmission of ranging and direction-finding information. Time division multiplexing, through the allocation and management of time slots, enables each search and rescue operation platform to send and receive signals within a specified time, further improving communication efficiency and reliability. Meanwhile, the search and rescue command platform plays a crucial role throughout the entire search and rescue process. It not only receives and processes the ranging and direction-finding results from each search and rescue operation platform but also formulates scientifically sound search and rescue command plans based on this information, ensuring the efficient and orderly conduct of the rescue operation.

[0097] In this embodiment, as Figure 4 As shown, it also includes the following steps: S900: The search and rescue command platform schedules time slot resources according to the signal strength received by each search and rescue operation platform, and allocates more time slot resources to the platform with good search and detection signal reception effect through time slot control commands according to the detection cycle P.

[0098] Specifically, step S900 is as follows:

[0099] Let N be the total number of search and rescue operation platforms participating in the search and rescue. The time slots allocated to the search and rescue operation platform M1 Let (x=1,2,…N) be the number of service time slots allocated to search and rescue operation platform Mx. Within a preset time period, the average signal quality received by each search and rescue operation platform is RSSI. n (n=M1,M2,…M) n ), The average signal quality received by search and rescue platform M1. Given the average signal quality received by search and rescue platform Mx, the total number of time slots to be allocated is T. total ;

[0100] S901: Each search and rescue platform sends an inquiry signal to the distressed target, respectively. , … ;

[0101] S902: Each search and rescue platform receives the response signal sent by the distressed target and obtains the signal quality RSSI by measuring the received signal. n The measurement results were then sent to the search and rescue command platform.

[0102] S903: Based on the signal quality RSSIn (n=M1,M2,…M) received by each search and rescue operation platform from all search and rescue operation platforms, RSSIn is calculated. n To allocate initial time slots to each search and rescue platform, first allocate time slots to the search and rescue platform with the best signal quality among those currently awaiting allocation. Assuming search and rescue platform M1 has the best average signal quality, then the number of time slots allocated is... ;in, This is an adjustment factor, and its value range is [0, 1].

[0103] S904: Based on signal average quality RSSI n From highest to lowest quality, select the platform M with the best received signal quality from the platforms that have not been allocated time slot resources. x If the remaining time slots are allocated, then the number of time slots allocated is... for:

[0104] ;

[0105] in, This is an adjustment factor, and its value range is [0, 1].

[0106] S905: In this manner, allocate corresponding time slot resources to all platforms until all platforms or time slot resources have been allocated.

[0107] Specifically, the above method dynamically and rationally allocates time slot resources based on the signal strength received by the search and rescue platforms. In actual search and rescue scenarios, the quality of signals received from distressed targets varies among search and rescue platforms in different locations and with different equipment states. Through this method, platforms with better signal reception can obtain more time slot resources, enabling them to send and receive critical information more frequently, such as more precise ranging and direction-finding interrogation signals, which helps to more accurately determine the location of distressed targets. For platforms with relatively poor signal reception, although fewer time slot resources are allocated, they are still guaranteed to participate in communication for a certain period and will not be completely excluded from search and rescue information exchange. This allocation method makes full use of limited time slot resources, improving the efficiency and reliability of the entire search and rescue collaborative communication system.

[0108] In this embodiment, in step S400, each search and rescue platform receives ranging response signals and direction-finding beacon signals, and calculates its relative distance and relative direction with the distressed target, specifically as follows:

[0109] Each search and rescue platform receives the ranging response signal and direction finding beacon signal sent by the distressed target, extracts the timestamp marked in the ranging response signal, and calculates the relative distance between the search and rescue platform and the distressed target; based on the direction of arrival of the direction finding beacon signal, the amplitude comparison direction finding method or the MUSIC direction finding method is used to determine the heading of the distressed target relative to its respective search and rescue platform.

[0110] Specifically, when calculating relative distance, each search and rescue platform utilizes the timestamp information in the ranging response signal, combined with the signal propagation speed (usually the speed of light), to accurately determine the distance to the distressed target by calculating the round-trip time difference. This process requires extremely high time precision to ensure the accuracy of the distance calculation. For determining relative direction, amplitude comparison direction finding estimates the direction of signal arrival by comparing the differences in signal amplitude received by different antennas, suitable for scenarios with significant signal strength variations. MUSIC direction finding is a high-resolution direction finding technique that utilizes the spatial spectrum estimation characteristics of array antennas to more accurately distinguish the directions of multiple signal sources, particularly suitable for direction finding needs in complex electromagnetic environments. Through the flexible application of these two methods, each search and rescue platform can accurately obtain the position information of the distressed target relative to itself, providing crucial data support for subsequent rescue operations.

[0111] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A collaborative communication method for searching multiple people in distress in water, characterized in that, The steps are as follows: S100: The search and rescue operation platform uses frequency division multiplexing or time division multiplexing to send ranging and direction finding interrogation signals; S200: The distressed target fills in the local timestamp and response information in the response information and sends a ranging response signal at a predetermined frequency. S300: The distressed target transmits direction-finding beacon signals on other frequencies; S400: Each search and rescue operation platform receives ranging response signals and direction finding beacon signals, and calculates its relative distance and relative direction with the distressed target; S5 00: Each search and rescue operation platform sends its direction-finding distance and results to the search and rescue command platform via its own frequency; S600: The search and rescue command platform receives direction finding distance and results, and after merging and aggregating them, forms the relative positional relationship between the distressed target and the search and rescue operation platform at the search and rescue site; S700: The search and rescue command platform formulates a search and rescue command plan and broadcasts it to each search and rescue operation platform. S800: Each search and rescue operation platform receives the search and rescue command plan and carries out rescue operations. The following steps are also included: S900: The search and rescue command platform allocates time slot resources based on the signal strength received by each search and rescue operation platform, and according to the detection cycle P, allocates more time slot resources to platforms with better search and detection signal reception through time slot control commands. In step S900, specifically: Let N be the total number of search and rescue operation platforms participating in the search and rescue. The time slots allocated to the search and rescue operation platform M1 Let (x=1,2,…N) be the number of service time slots allocated to search and rescue operation platform Mx. Within a preset time period, the average signal quality received by each search and rescue operation platform is RSSI. n (n=M1,M2,…M) n ), The average signal quality received by search and rescue platform M1. Given the average signal quality received by search and rescue platform Mx, the total number of time slots to be allocated is T. total ; S901: Each search and rescue platform sends an inquiry signal to the distressed target, respectively. , … ; S902: Each search and rescue platform receives the response signal sent by the distressed target and obtains the signal quality RSSI by measuring the received signal. n The measurement results were then sent to the search and rescue command platform. S903: Based on the signal quality RSSIn (n=M1,M2,…M) received by each search and rescue operation platform from all search and rescue operation platforms, RSSIn is calculated. n To allocate initial time slots to each search and rescue platform, first allocate time slots to the search and rescue platform with the best signal quality among those currently awaiting allocation. Assuming search and rescue platform M1 has the best average signal quality, then the number of time slots allocated is... ;in, This is an adjustment factor, and its value range is [0, 1]. S904: Based on signal average quality RSSI n From highest to lowest quality, select the platform M with the best received signal quality from the platforms that have not been allocated time slot resources. x If the remaining time slots are allocated, then the number of time slots allocated is... for: ； in, This is an adjustment factor, and its value range is [0, 1]. S905: In this manner, allocate corresponding time slot resources to all platforms until all platforms or time slot resources have been allocated.

2. The search and collaborative communication method for multiple people in distress in water as described in claim 1, characterized in that, In step S100, the search and rescue operation platform uses frequency division multiplexing to send ranging and direction finding interrogation signals, specifically: S101: Assign ID numbers to each search and rescue operation platform; S102: Each search and rescue operation platform sends ranging inquiry signals, direction finding inquiry signals, and its own platform ID signal to the distressed target according to differentiated communication frequencies; S103: The distressed target uses a wide-spectrum receiving method to receive ranging and interrogation signals.

3. The search and collaborative communication method for multiple people in distress in water as described in claim 1, characterized in that, In step S100, the search and rescue operation platform uses time-division multiplexing to send ranging and direction-finding interrogation signals, specifically as follows: S101: Assign ID numbers to each search and rescue operation platform; S102: The search and rescue command platform sends a broadcast time slot, and the search and rescue operation platform approaching the accident site receives the information sent by the broadcast time slot and sends an access request information in the access time slot; S103: After receiving the access request information, the search and rescue command platform allocates a time slot to the search and rescue operation platform and sends it in the broadcast time slot; S104: Each search and rescue operation platform sends ranging inquiry signals, direction finding inquiry signals, and its own platform ID signal according to the pre-allocated time slots; S105: The distressed target uses a wide-spectrum receiving method to receive ranging and interrogation signals.

4. The search and collaborative communication method for multiple people in distress in water as described in claim 1, characterized in that, In step S400, each search and rescue platform receives ranging response signals and direction-finding beacon signals, and calculates its relative distance and relative direction with the distressed target, specifically as follows: Each search and rescue platform receives the ranging response signal and direction finding beacon signal sent by the distressed target, extracts the timestamp marked in the ranging response signal, and calculates the relative distance between the search and rescue platform and the distressed target; based on the direction of arrival of the direction finding beacon signal, the amplitude comparison direction finding method or the MUSIC direction finding method is used to determine the heading of the distressed target relative to its respective search and rescue platform.

5. A search and coordination communication system for multiple people in distress in water, used to implement the search and coordination communication method for multiple people in distress in water as described in any one of claims 1 to 4, characterized in that: Includes multiple search and rescue operation platforms, receiving devices, and a search and rescue command platform; Multiple search and rescue operation platforms are used to send ranging and direction finding inquiry signals and obtain signals sent by receiving devices, and obtain the direction finding and ranging results of each receiving device through direction finding methods and send them to the command device; The receiving device is used to receive ranging and interrogation signals and fill in local timestamps and identity information in the response information, and send ranging response signals at a predetermined frequency. The search and rescue command platform is used to integrate and converge the received direction and distance measurement results to form the relative positional relationships between the distressed targets and search and rescue operation platforms at the search and rescue site, and to formulate a rescue command operation plan, which is then broadcast to all search and rescue operation platforms at sea. The search and rescue command platform is used to send broadcast time slots and allocate time slots to search and rescue operation platforms; The search and rescue operation platform is used to send access request information in the access time slots allocated by the search and rescue command platform.

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