Satellite and shore-based base station cooperative VDES terminal access management method and device

Abstract

This invention provides a VDES terminal access management method and apparatus based on satellite and shore-based base station collaboration. The method includes: calculating the relative radial velocity and delay spread spectrum based on the angle of arrival and signal strength of the uplink signal received by the shore-based base station from the VDES terminal, combined with the global reference frame header timestamp broadcast by the satellite downlink; identifying potential interference sources based on the multipath overlap relationship of the delay spread spectrum; predicting the spatial displacement trajectory within the next superframe period based on the relative radial velocity of the potential interference sources; constructing a spatial conflict map based on the line-of-sight range between the spatial displacement trajectory and the shore-based base station; generating a protective isolation zone based on the boundary of dynamically shielded areas in the spatial conflict map; dividing the sea area covered by the protective isolation zone into time-slot multiplexing domains; and scheduling VDES terminal access based on the number density of potential interference sources within each time-slot multiplexing domain. This invention achieves efficient spectrum multiplexing access for VDES terminals under complex sea conditions.

Description

Technical Field

[0001] This invention relates to the field of computer technology, and in particular to a VDES terminal access management method and apparatus based on satellite and shore-based base station collaboration. Background Technology

[0002] With the digital transformation of the global shipping industry, the Very High Frequency Data Exchange System (VDES) has become a critical infrastructure for maritime communications, supporting Automatic Identification System (AIS), Application Specific Messages (ASM), and Wideband Data Exchange (VDE). In existing VDES standards and deployments, terminal access management primarily relies on the Self-Organizing Time Division Multiple Access (SOTDMA) mechanism. Under this mechanism, ship terminals predict future time slots based on their location and announce their right to occupy specific time slots by broadcasting "reservation information." Other terminals listen to this reservation information to avoid conflicts.

[0003] However, this existing method suffers from two major fatal flaws in the complex electromagnetic environment of the sea surface: First, the problem of hidden nodes and beyond-line-of-sight interference. Due to the curvature of the Earth and the atmospheric ducting effect at sea, two ships that are far apart (e.g., more than 40 nautical miles) may be beyond each other's radio television range (i.e., unable to see each other and listen to each other's reserved information), but their signals can still propagate beyond line-of-sight and reach shore-based base stations or a third ship simultaneously, leading to severe co-channel signal collisions. Existing local neighbor discovery mechanisms cannot detect such remote hidden nodes, resulting in a sharp increase in access conflict rates in high-density sea areas. Second, the fragmentation and low utilization of spatiotemporal resources. The highly dynamic movement of ships leads to frequent changes and releases of time slot reservations, generating a large number of scattered and difficult-to-reuse "fragmented time slots." Existing methods lack a global perspective to integrate these fragments, typically employing conservative static guard intervals or simple random backoff, resulting in a large amount of idle spectrum resources in open sea areas with sparse ships, while congestion occurs in high-density areas such as ports due to insufficient resources, failing to achieve optimal spectrum efficiency. Summary of the Invention

[0004] This invention provides a VDES terminal access management method and apparatus based on satellite and shore-based base station collaboration, aiming to solve the technical problems of high VDES terminal access conflict rate and low spectrum efficiency caused by hidden node beyond-line-of-sight interference and spatiotemporal resource fragmentation in the background art, and to achieve efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0005] In a first aspect, the present invention provides a VDES terminal access management method based on satellite and shore-based base station collaboration, comprising: Based on the angle of arrival and signal strength of the uplink signal received by the VDES terminal from the shore-based base station, combined with the global reference frame header timestamp broadcast by the satellite downlink, the relative radial velocity and delay spread spectrum of each VDES terminal relative to the shore-based base station are calculated, and the subset of terminals with interference are identified based on the multipath overlap relationship of the delay spread spectrum, thus obtaining potential interference sources. Based on the relative radial velocity of the potential interference source, predict its spatial displacement trajectory in the next superframe period, and based on the line-of-sight range of the spatial displacement trajectory and the shore-based base station, construct a spatial conflict map containing dynamic shading areas. Based on the boundaries of the dynamically masked areas in the spatial conflict map, a protective isolation zone is generated, and the sea area covered by the protective isolation zone is divided into a time-slot multiplexing domain. Based on the number density of potential interference sources within each time slot multiplexing domain, access scheduling is performed for VDES terminals within each time slot multiplexing domain.

[0006] Secondly, the present invention also provides a VDES terminal access management device based on satellite and shore-based base station collaboration, for implementing the VDES terminal access management method based on satellite and shore-based base station collaboration as described in the first aspect; the VDES terminal access management device based on satellite and shore-based base station collaboration includes: The interference source localization module is used to calculate the relative radial velocity and delay spread spectrum of each VDES terminal relative to the shore base station based on the angle of arrival and signal strength of the uplink signal received by the shore base station, combined with the global reference frame header timestamp broadcast by the satellite downlink, and to identify the subset of terminals with interference based on the multipath overlap relationship of the delay spread spectrum, thereby obtaining potential interference sources. The conflict map construction module is used to predict the spatial displacement trajectory of the potential interference source in the next superframe period based on the relative radial velocity of the source, and to construct a spatial conflict map containing dynamic occlusion areas based on the line-of-sight range between the spatial displacement trajectory and the shore-based base station. The sea area division module is used to generate a protective isolation zone based on the boundary of the dynamically obscured area in the spatial conflict map, and divide the sea area covered by the protective isolation zone into a time slot multiplexing domain. The terminal access scheduling module is used to schedule the access of VDES terminals in each time slot multiplexing domain based on the number density of potential interference sources in each time slot multiplexing domain.

[0007] Thirdly, the present invention also provides an electronic device, comprising: a memory for storing computer software programs; and a processor for reading and executing the computer software programs, thereby realizing the VDES terminal access management method based on satellite and shore-based base station collaboration as described above.

[0008] Fourthly, the present invention also provides a non-transitory computer-readable storage medium storing a computer software program, which, when executed by a processor, implements the VDES terminal access management method based on satellite and shore-based base station collaboration as described above.

[0009] Fifthly, the present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the VDES terminal access management method based on satellite and shore-based base station collaboration as described above.

[0010] The VDES terminal access management method based on satellite and shore-based base station collaboration provided in this invention calculates the relative radial velocity and delay spread spectrum of each VDES terminal relative to the shore-based base station by combining the angle of arrival and signal strength of the uplink signals received by the shore-based base station with the timestamp of the global reference frame header broadcast by the satellite. The multipath overlap relationship of the delay spread spectrum can accurately reflect the superposition of signals from different terminals and identify potential interference sources that may cause signal collisions. By analyzing the correlation between the relative radial velocity of potential interference sources and the high-dynamic motion characteristics of ships, the spatial displacement trajectory of the potential interference sources in the next superframe period is predicted through velocity. At the same time, by combining the line-of-sight range of the shore-based base station and the objective law of the curvature of the earth's occlusion, the geographical range of the dynamic occlusion area is determined, and a spatial conflict map containing the area is constructed. Therefore, it is possible to accurately locate hidden nodes and potential areas of beyond-line-of-sight interference. Based on spatial conflict maps, the boundaries of dynamically shielded areas are analyzed. Combining this with the maximum beyond-line-of-sight propagation distance determined by the sea surface atmospheric refractive index, a protective isolation zone capable of isolating beyond-line-of-sight interference is generated. Furthermore, by rationally dividing non-overlapping time-slot multiplexing domains, the geographical spacing between adjacent domains is ensured to meet anti-interference requirements, thus resolving signal collision issues at the spatial level. The matching relationship between the number density of potential interference sources and spectrum resource requirements within each time-slot multiplexing domain is analyzed. Differentiated access scheduling strategies are formulated based on density differences to achieve dynamic resource allocation.

[0011] Therefore, the embodiments of the present invention, on the one hand, accurately identify hidden nodes and beyond-line-of-sight interference risks in the dynamically shielded area through a spatial conflict map, and spatially isolate interference by dividing the protective isolation zone and time slot multiplexing domain, thereby avoiding beyond-line-of-sight signal collisions and solving the problems of hidden nodes and beyond-line-of-sight interference. On the other hand, by scheduling access according to the number and density of potential interference sources, the idle resources in sparse sea areas and fragmented time slots in high-density areas are integrated and optimized to solve the problem of spatiotemporal resource fragmentation. Thus, the technical problems of high VDES terminal access conflict rate and low spectrum efficiency caused by beyond-line-of-sight interference from hidden nodes and spatiotemporal resource fragmentation in the background technology are solved, and efficient spectrum multiplexing access of VDES terminals under complex sea conditions is realized. Attached Figure Description

[0012] Figure 1This is a flowchart illustrating the VDES terminal access management method based on satellite and shore-based base station collaboration provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the VDES terminal access management device based on satellite and shore-based base station collaboration provided in an embodiment of the present invention; Figure 3 An embodiment diagram of the electronic device provided in this invention; Figure 4 An embodiment diagram of a computer-readable storage medium provided in accordance with the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0015] In the description of this invention, the term "for example" is used to mean "used as an example, illustration, or description." Any embodiment described as "for example" in this invention is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use the invention. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that the invention can be made without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid obscuring the description of the invention with unnecessary detail. Therefore, the invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed herein.

[0016] Optionally, see Figure 1 , Figure 1This is a flowchart illustrating the VDES terminal access management method based on satellite and shore-based base station collaboration provided by the present invention. In this embodiment, the executing entity of the VDES terminal access management method based on satellite and shore-based base station collaboration is a terminal management device. Therefore, the VDES terminal access management method based on satellite and shore-based base station collaboration includes: Step 10: Based on the angle of arrival and signal strength of the uplink signal of the VDES terminal received by the shore base station, and combined with the global reference frame header timestamp broadcast by the satellite downlink, calculate the relative radial velocity and time delay spread spectrum of each VDES terminal relative to the shore base station, and identify the subset of terminals with interference based on the multipath overlap relationship of the time delay spread spectrum to obtain potential interference sources.

[0017] Optionally, the terminal management device acquires the angle of arrival and signal strength of the uplink signal from the VDES terminal received by the shore-based base station. The angle of arrival refers to the angle between the uplink signal transmitted by the VDES terminal and the preset reference direction of the shore-based base station when the uplink signal reaches the shore-based base station, used to characterize the approximate orientation of the VDES terminal relative to the shore-based base station. The signal strength refers to the power of the uplink signal received by the shore-based base station from the VDES terminal, used to assist in determining the propagation distance and signal propagation quality between the VDES terminal and the shore-based base station. Simultaneously, the terminal management device receives the global reference frame header timestamp broadcast by the satellite downlink. This global reference frame header timestamp is a standard time stamp broadcast globally by the satellite system for time synchronization, ensuring that the time base of the terminal management device, the shore-based base station, and all VDES terminals is consistent, avoiding calculation errors caused by time asynchrony.

[0018] Based on the obtained uplink signal angle of arrival, signal strength, and global reference frame header timestamp, the terminal management device calculates the relative radial velocity and delay spread spectrum of each VDES terminal relative to the shore-based base station. The relative radial velocity refers to the speed of the VDES terminal relative to the shore-based base station along the line connecting the two. When the VDES terminal is close to the shore-based base station, the relative radial velocity is positive; when the VDES terminal is far from the shore-based base station, the relative radial velocity is negative. The delay spread spectrum refers to the distribution spectrum of the complex gain values ​​of the signal corresponding to different propagation delays caused by multipath propagation during the propagation of the uplink signal from the VDES terminal to the shore-based base station. The delay spread spectrum includes the phase angles of the complex gain values ​​of multiple multipath components. Each multipath component corresponds to a signal propagation path, and the phase angle is used to characterize the phase characteristics of the signal along that path.

[0019] In one embodiment, assuming the shore-based base station is deployed at a fixed location along the coast, the terminal management device establishes a wired communication connection with the shore-based base station to obtain uplink signal data from all VDES terminals received by the shore-based base station in real time; at the same time, the terminal management device accesses the satellite downlink to receive the global reference frame header timestamp broadcast by the satellite in real time, ensuring that the time synchronization error does not exceed 1 microsecond.

[0020] Three VDES terminals (designated as Terminal 1, Terminal 2, and Terminal 3) are currently sailing within the sea area covered by a shore-based base station. The shore-based base station receives uplink signals from Terminal 1 with an angle of arrival (Angle of Arrival) of 30 degrees and a signal strength of -60 dBm; from Terminal 2 with an Angle of Arrival (Angle of Arrival) of 150 degrees and a signal strength of -65 dBm; and from Terminal 3 with an Angle of Arrival (Angle of Arrival) of 270 degrees and a signal strength of -58 dBm. The terminal management device invokes preset calculation logic and, in conjunction with the global reference frame header timestamp, calculates the above signal parameters: For the calculation of relative radial velocity, the signal angle of arrival and signal strength of the same VDES terminal were obtained at 5 consecutive time points (each time point was 1 second apart). The changes in signal angle of arrival and signal strength at adjacent time points were calculated. Combined with the signal propagation attenuation law, the motion direction and velocity components of the VDES terminal relative to the shore-based base station were deduced. Finally, the relative radial velocity of terminal 1 was calculated to be 10 knots (1 knot = 1 nautical mile / hour), with the direction towards the shore-based base station; the relative radial velocity of terminal 2 was 8 knots, with the direction away from the shore-based base station; and the relative radial velocity of terminal 3 was 12 knots, with the direction towards the shore-based base station.

[0021] For the calculation of the time delay spread spectrum, the terminal management device performs multipath separation processing on the uplink signal of each VDES terminal, identifies three main multipath components (corresponding to the direct path, sea surface reflection path, and atmospheric reflection path, respectively), measures the propagation delay of each multipath component, and calculates the phase angle of the complex gain value of each multipath component, finally forming the time delay spread spectrum of each VDES terminal: In the time delay spread spectrum of terminal 1, the direct path delay is 10 microseconds and the phase angle is 0 degrees; the sea surface reflection path delay is 12 microseconds and the phase angle is 90 degrees; the atmospheric reflection path delay is 15 microseconds and the phase angle is 180 degrees; the time delay spread spectrum calculation process of terminals 2 and 3 is the same as that of terminal 1, only the delay values ​​and phase angles differ due to different positions and motion states.

[0022] The terminal management device identifies a subset of terminals with interference based on the multipath overlap relationship of the time delay spread spectrum, and obtains potential interference sources. For example, it determines whether there is a case of multipath component propagation delay overlap and phase angle conflict in the time delay spread spectrum of different VDES terminals. If so, these VDES terminals are classified as a subset of terminals with interference, i.e. potential interference sources. Potential interference sources refer to a set of VDES terminals that may cause co-frequency collision interference to the signal transmission of other VDES terminals, as described in steps 101 to 104.

[0023] Step 20: Based on the relative radial velocity of the potential interference source, predict its spatial displacement trajectory in the next superframe period, and based on the spatial displacement trajectory and the line-of-sight range of the shore-based base station, construct a spatial conflict map containing the dynamic shading area.

[0024] Optionally, the terminal management device acquires the relative radial velocity of the potential interference source. This relative radial velocity is defined as the speed at which the potential interference source moves relative to the shore-based base station along the line connecting the two, and includes both magnitude and direction information. Based on this relative radial velocity, the terminal management device predicts the spatial displacement trajectory of the potential interference source in the next superframe period. Here, the superframe period refers to the preset signal transmission period in the VDES system, the specific duration of which is set according to the VDES system standard, typically between 1 and 10 seconds. The spatial displacement trajectory refers to the path trajectory formed by the potential interference source moving from its current position according to its relative radial velocity within the superframe period. This trajectory includes the predicted position of the potential interference source at each time point within the period.

[0025] In one embodiment, it is assumed that the superframe period of the VDES system is set to 5 seconds, and the potential interference sources obtained in step 10 are terminal 1 and terminal 3, wherein the relative radial velocity of terminal 1 is 10 knots (towards the shore-based base station), and the current position is 20 nautical miles away from the shore-based base station; the relative radial velocity of terminal 3 is 12 knots (towards the shore-based base station), and the current position is 25 nautical miles away from the shore-based base station.

[0026] Based on the above parameters, the terminal management device predicts the spatial displacement trajectories of both terminals in the next superframe cycle: First, the relative radial velocity units are converted to nautical miles per second (10 knots = 10 / 3600 nautical miles per second ≈ 0.0028 nautical miles per second, 12 knots = 12 / 3600 nautical miles per second ≈ 0.0033 nautical miles per second); second, based on a superframe cycle of 5 seconds, the displacement distance of each potential interference source is calculated: the displacement distance of terminal 1 is 0.0028 nautical miles per second * 5 seconds ≈ 0.014 nautical miles, and the displacement distance of terminal 3 is 0.0033 nautical miles per second * 5 seconds ≈ 0.014 nautical miles. 165 nautical miles; Finally, combining the current azimuth of the potential interference source (determined by the uplink signal arrival angle in step 10), the movement direction of both is determined to be towards the shore-based base station, and then the spatial displacement trajectory is plotted: Terminal 1 starts from the current position of 20 nautical miles, moves 0.014 nautical miles towards the shore-based base station along the direction of arrival angle 30 degrees, and the final predicted position is 19.986 nautical miles away from the shore-based base station; Terminal 3 starts from the current position of 25 nautical miles, moves 0.0165 nautical miles towards the shore-based base station along the direction of arrival angle 270 degrees, and the final predicted position is 24.9835 nautical miles away from the shore-based base station.

[0027] The terminal management device constructs a spatial conflict map including dynamic shielding areas based on the spatial displacement trajectory of potential interference sources and the line-of-sight range of the shore-based base station. Specifically, steps 201 to 204 are performed as follows: First, the line-of-sight range of the shore-based base station is determined. The line-of-sight range refers to the maximum distance at which the shore-based base station can directly receive VDES terminal signals without obstruction. This distance is determined by factors such as the antenna height of the shore-based base station and the curvature of the Earth. Then, based on the spatial displacement trajectory of the potential interference source, it is determined whether it will enter or remain outside the line-of-sight range within the superframe period. Areas outside the line-of-sight range but whose signals may reach the shore-based base station or other VDES terminals through beyond-line-of-sight propagation are designated as dynamic shielding areas. Finally, the sea area covered by the shore-based base station, the spatial displacement trajectory of the potential interference source, and the dynamic shielding areas are integrated to form a spatial conflict map. This map is used to visually present the distribution of areas where signal conflicts may occur. The dynamic shielding area is a geographical sector where the shore-based base station cannot directly detect signals due to Earth's curvature, but where signal superposition exists. A geographical sector refers to a sea area divided at a certain angle centered on the shore-based base station.

[0028] Step 30: Based on the boundary of the dynamically masked area in the spatial conflict map, a protective isolation zone is generated, and the sea area covered by the protective isolation zone is divided into time slot multiplexing domains, such that the minimum geographical interval between any two adjacent time slot multiplexing domains is greater than the maximum beyond-line-of-sight propagation distance determined by the atmospheric refractive index of the sea surface.

[0029] Optionally, the terminal management device extracts the boundaries of dynamically masked areas from the spatial conflict map. The boundary of a dynamically masked area refers to the geographical dividing line between the dynamically masked area and the unmasked area. This boundary is precisely defined using geographical coordinates (latitude and longitude) to ensure the accuracy of boundary delineation. Based on the boundaries of the dynamically masked areas, the terminal management device generates a protective isolation zone. This protective isolation zone is a buffer zone delineated outside the boundaries of the dynamically masked areas to prevent signal interference between different areas. The width of the protective isolation zone is determined based on the sea surface atmospheric refractive index, which refers to the ability of the atmosphere near the sea surface to refract electromagnetic waves. Its value is determined by environmental factors such as sea surface temperature, humidity, and air pressure. The width of the protective isolation zone must ensure that it can isolate beyond-line-of-sight signal interference between different dynamically masked areas.

[0030] The terminal management device divides the sea area covered by the protective isolation zone into non-overlapping time-slot reuse domains. A time-slot reuse domain refers to an independent sea area that can reuse time-slot resources. The division process must meet the following condition: the minimum geographical interval between any two adjacent time-slot reuse domains is greater than the maximum beyond-line-of-sight propagation distance determined by the sea surface atmospheric refractive index. The maximum beyond-line-of-sight propagation distance refers to the farthest distance that electromagnetic waves can achieve beyond-line-of-sight propagation under the current sea surface atmospheric refractive index conditions. This distance is calculated by combining the sea surface atmospheric refractive index parameter with the electromagnetic wave propagation formula to ensure that VDES terminal signals in adjacent time-slot reuse domains will not interfere with each other through beyond-line-of-sight propagation.

[0031] Continuing with the above embodiment, assume that in the spatial conflict map constructed in step 20, there are two dynamically masked areas (denoted as masked area A and masked area B, respectively). The geographical coordinates of the boundary of masked area A are (30°00′N, 120°00′E) to (30°10′N, 120°10′E), and the geographical coordinates of the boundary of masked area B are (30°20′N, 120°00′E) to (30°30′N, 120°10′E). The terminal management device measures the current atmospheric refractive index of the sea surface and obtains real-time detection data through the atmospheric refractive index detection module carried by the shore-based base station. The maximum beyond-line-of-sight propagation distance corresponding to the current atmospheric refractive index of the sea surface is calculated to be 5 nautical miles. Based on this maximum beyond-line-of-sight propagation distance, the terminal management device generates a protective isolation zone: a 2-nautical-mile-wide protective isolation zone is delineated on the outer side of shielded area A (the side furthest from the shore-based base station), with its boundary coordinates ranging from (29°58′N, 119°58′E) to (30°12′N, 120°12′E); a 2-nautical-mile-wide protective isolation zone is delineated on the outer side of shielded area B, with its boundary coordinates ranging from (30°18′N, 119°58′E) to (30°32′N, 120°12′E), ensuring that the protective isolation zone can effectively buffer beyond-line-of-sight signal interference.

[0032] The terminal management device divides the sea area covered by the protective isolation zone into non-overlapping time-slot multiplexing domains: Area A and its corresponding protective isolation zone are designated as time-slot multiplexing domain 1, with a geographical range from (29°58′N, 119°58′E) to (30°12′N, 120°12′E); Area B and its corresponding protective isolation zone are designated as time-slot multiplexing domain 2, with a geographical range from (30°18′N, 119°58′E) to (30°32′N, 120°12′E). Simultaneously, the minimum geographical interval between the two adjacent time-slot multiplexing domains is detected. Calculations show that the minimum geographical interval between time-slot multiplexing domain 1 and time-slot multiplexing domain 2 is 6 nautical miles, which is greater than the maximum beyond-line-of-sight propagation distance of 5 nautical miles determined by the current atmospheric refractive index at the sea surface. This meets the division requirements and ensures that VDES terminal signals within the two time-slot multiplexing domains will not generate beyond-line-of-sight interference.

[0033] Step 40: Based on the number density of potential interference sources in each time slot multiplexing domain, perform access scheduling for VDES terminals in each time slot multiplexing domain.

[0034] Optionally, the terminal management device calculates the number density of potential interference sources within each time slot multiplexing domain. The number density refers to the number of potential interference sources per unit sea area, measured in vessels per square nautical mile. This number density value is calculated by statistically analyzing the sea area of ​​each time slot multiplexing domain and the number of potential interference sources within that area. Based on the number density of potential interference sources within each time slot multiplexing domain, the terminal management device performs access scheduling for VDES terminals within each time slot multiplexing domain, as described in steps 401 to 404. Here, VDES terminals include both potential and non-potential interference sources. Access scheduling refers to the terminal management device allocating a dedicated time slot for each VDES terminal to ensure conflict-free signal transmission between terminals.

[0035] This invention addresses two main issues. First, by using a spatial conflict map to accurately identify hidden nodes and beyond-line-of-sight (BOS) interference risks within a dynamically shielded area, it spatially isolates interference by dividing the area into protective isolation zones and time slot reuse domains, thus avoiding BOS signal collisions and resolving the problems of hidden nodes and BOS interference. Second, by scheduling access based on the density of potential interference sources, it integrates and optimizes idle resources in sparse sea areas and fragmented time slots in high-density areas, resolving the problem of spatiotemporal resource fragmentation. This solves the technical problems of high access conflict rate and low spectral efficiency of VDES terminals caused by beyond-line-of-sight interference from hidden nodes and spatiotemporal resource fragmentation in the background technology, achieving efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0036] Optionally, the processes of steps 101 to 104 include: Step 101: Based on the phase angle of the complex gain value of each multipath component in the time delay spread spectrum, calculate the difference vector of the phase angle between two adjacent VDES signal periods.

[0037] Optionally, the terminal management device extracts the phase angle of the complex gain value of each multipath component in the delay spread spectrum. Here, a multipath component refers to the signal component that reaches the shore-based base station through different propagation paths (such as direct path, sea surface reflection path, and atmospheric reflection path) during the propagation of the VDES terminal's uplink signal to the shore-based base station. The phase angle of the complex gain value is a parameter characterizing the phase characteristics of this multipath component signal, and its value ranges from 0 degrees to 360 degrees. The VDES signal period refers to the fixed time interval for the VDES terminal to transmit the uplink signal, and its duration is preset according to the VHF data exchange system standard. The terminal management device selects two adjacent VDES signal periods, extracts the phase angle of the same multipath component within each of these two signal periods, subtracts the phase angle of the previous signal period from the phase angle of the subsequent signal period, and obtains the phase angle difference of the multipath component within the two adjacent VDES signal periods. This difference is used as the ordinate of a vector, and the time interval between the two signal periods is used as the abscissa of the vector to construct the phase angle difference vector of the multipath component.

[0038] The difference vector is a vector used to characterize the trend and magnitude of the phase angle change within two adjacent signal periods. Its magnitude reflects the magnitude of the phase angle change, and its direction reflects the direction of the phase angle change.

[0039] The terminal management device performs the above operation on each multipath component in the time delay spread spectrum and calculates the phase angle difference vector corresponding to each multipath component.

[0040] Step 102: Using the multipath component whose magnitude of the differential vector exceeds the Doppler frequency tolerance range as the target component, and based on the carrier frequency offset of the main path component in the target component, retrieve the carrier frequency offset of the signals of other VDES terminals in the same receiving time slot.

[0041] Optionally, the Doppler frequency tolerance range refers to the maximum range of signal frequency offset allowed by the VDES system due to ship motion. This range is preset based on the performance parameters of the shore-based base station receiver and the maximum speed of ship motion on the sea surface, and is usually set to ±50 Hz. It is used to distinguish between phase angle changes caused by normal motion and abnormal phase angle changes caused by interference. The terminal management device calculates the magnitude of each phase angle differential vector. The calculation method for the magnitude is not described in detail here; the magnitude corresponds to the magnitude of the phase angle change.

[0042] The terminal management device compares the magnitude of each differential vector with a preset Doppler frequency tolerance range, filters out multipath components whose magnitudes exceed the tolerance range, and identifies these multipath components as target components. Target components refer to multipath components with abnormal phase angle changes, which may indicate signal interference.

[0043] The terminal management device extracts the main path component from each target component. The main path component refers to the multipath component with the strongest signal strength and shortest propagation delay among the target components, and it is also the component that best characterizes the VDES terminal signal. The carrier frequency offset of the main path component refers to the difference between the uplink signal carrier frequency transmitted by the VDES terminal and the preset receiving carrier frequency of the shore-based base station. Its generation is mainly caused by the movement of the ship and interference from the electromagnetic environment of the sea surface. This parameter can reflect the frequency stability of the signal. The receiving time slot of the main path component refers to the fixed time segment in which the shore-based base station receives the uplink signal of the VDES terminal. Each receiving time slot corresponds to a fixed time interval, used to distinguish the signal transmission time of different VDES terminals.

[0044] The terminal management device retrieves the signals of all other VDES terminals within the receiving time slot, extracts the carrier frequency offset of these VDES terminal signals, and completes the carrier frequency offset retrieval.

[0045] Step 103: The VDES terminal pairs whose carrier frequency offset difference is less than the receiver intermediate frequency filter bandwidth are identified as the first interfering terminal pairs, and the angular distance between the two uplink signals is calculated based on the estimated angle of arrival of the two VDES terminals in the first interfering terminal pair.

[0046] Optionally, the receiver intermediate frequency filter bandwidth refers to the range of signal frequencies that the intermediate frequency filter in the shore-based base station receiver is allowed to pass through. This bandwidth is determined according to the receiver's design parameters and is usually between 100 Hz and 200 Hz. It is used to determine whether the frequency offset of two signals is within the range that can cause interference.

[0047] The terminal management device calculates the difference between the carrier frequency offset of each other VDES terminal it retrieves and the carrier frequency offset of the main path component of the target component, obtaining the absolute value of the difference between the two carrier frequency offsets. Subsequently, the terminal management device compares this absolute value with the preset receiver intermediate frequency filter bandwidth. If the absolute value of the difference is less than the receiver intermediate frequency filter bandwidth, it indicates that the signal frequency offset difference between the two VDES terminals is small, and they are prone to signal superposition interference when transmitting in the same reception time slot. The terminal management device identifies these two VDES terminals as the first interfering terminal pair. The first interfering terminal pair refers to the combination of two VDES terminals that may cause signal interference within the same reception time slot due to their small difference in carrier frequency offset.

[0048] The terminal management device extracts the estimated angles of arrival (Angles of Arrival) of the two VDES terminals in the first interfering terminal pair. These estimated Angles of Arrival are parameters that have been calculated in step 10, representing the azimuth of the two VDES terminals relative to the shore-based base station. Subsequently, the terminal management device calculates the angular distance between the uplink signals of the two VDES terminals. The angular distance is calculated by taking the absolute value of the difference between the two estimated Angles of Arrival. If the absolute value of the difference is greater than 180 degrees, then the absolute value of the difference is subtracted from 360 degrees to obtain the final angular distance. This angular distance is used to represent the azimuth difference between the two VDES terminals relative to the shore-based base station.

[0049] Step 104: Based on the angular distance of each first interference terminal pair and the half-power beamwidth of the antenna array of the shore-based base station, determine the potential interference source.

[0050] Optionally, the half-power beamwidth of the antenna array of the shore-based base station refers to the beam angle range corresponding to the radiated power of the antenna array of the shore-based base station dropping to half of its maximum value, and is used to characterize the directional reception capability of the antenna. The terminal management device determines the potential interference source based on the angular distance of each first interfering terminal pair and the half-power beamwidth of the antenna array of the shore-based base station, as described in steps 1041 to 1044.

[0051] Based on the multipath characteristics of the time delay spread spectrum and the precise analysis of signal parameters, this invention enables the accurate identification of potential interference sources that may cause signal collisions. It can effectively capture the superposition of signals from different VDES terminals, providing support for subsequent solutions to hidden node and beyond-line-of-sight interference problems, thereby improving the spectral efficiency of the VDES system and reducing the access conflict rate.

[0052] Optionally, the process of steps 1041 to 1044 includes: Step 1041: The first interference terminal pair with an angular distance less than half-power beamwidth is selected as the second interference terminal pair. Based on the relative time delay difference between the interference source and the main signal source in the second interference terminal pair, the second interference terminal pair with a relative time delay difference greater than zero and less than the VDES protection interval is determined as the candidate terminal pair.

[0053] Optionally, the terminal management device compares the angular distance of each first interfering terminal pair with the half-power beamwidth of the antenna array of the shore-based base station, and filters out first interfering terminal pairs whose angular distance is less than the half-power beamwidth, identifying such first interfering terminal pairs as second interfering terminal pairs. This is because when the angular distance of the first interfering terminal pair is less than the half-power beamwidth, the signals of the two VDES terminals will fall within the same beamwidth of the shore-based base station antenna array, significantly increasing the probability of signal superposition interference; therefore, these are further filtered as second interfering terminal pairs.

[0054] For each second interfering terminal pair, the terminal management device distinguishes between the primary signal source and the interfering signal source. The primary signal source refers to the VDES terminal with stronger signal strength and shorter propagation delay in the second interfering terminal pair, while the interfering signal source refers to the VDES terminal with weaker signal strength and longer propagation delay in the second interfering terminal pair, which may interfere with the primary signal source. Subsequently, the terminal management device calculates the relative delay difference between the interfering signal source and the primary signal source. The relative delay difference is the difference between the propagation delay of the interfering signal source's signal to the shore-based base station and the propagation delay of the primary signal source's signal to the shore-based base station. The calculation method is to subtract the propagation delay of the primary signal source from the propagation delay of the interfering signal source to obtain the relative delay difference.

[0055] The terminal management device invokes the VDES protection interval, which refers to the preset time interval in the VDES system used to avoid interference between adjacent time slot signals. Its duration is set according to the VDES system standard. Subsequently, the terminal management device compares the relative delay difference of each second interfering terminal pair with the VDES protection interval, filtering out second interfering terminal pairs with a relative delay difference greater than zero and less than the VDES protection interval. These second interfering terminal pairs are identified as candidate terminal pairs. This is because a relative delay difference greater than zero indicates that the interfering signal source lags behind the main signal source, and a difference less than the VDES protection interval indicates that the delay difference between the two signals does not exceed the system's preset anti-interference interval, making them prone to superimposed interference; therefore, they are considered candidate terminal pairs.

[0056] Step 1042: Based on the fluctuation trend of the main peak amplitude of the channel impulse response of each candidate terminal within a consecutive preset number of superframe periods, calculate the cross-correlation coefficient between the first fluctuation sequence of the main peak amplitude of the main signal source and the second fluctuation sequence of the main peak amplitude of the interference signal source.

[0057] Optionally, this preset number is set according to the dynamic characteristics of ship motion on the sea surface and the stability requirements of the VDES system, typically set to 5 to 10. Subsequently, the terminal management device acquires the channel impulse response of each candidate terminal within this preset number of superframe periods. The channel impulse response refers to the response relationship between the output signal and the input signal after the signal passes through the communication channel, which can reflect the influence of the channel on the signal. It includes the key parameter of the main peak amplitude, which refers to the amplitude value corresponding to the peak value with the largest signal strength in the channel impulse response, and is used to characterize the strength stability of the signal.

[0058] The terminal management device extracts the main peak amplitude of the channel impulse response of the main signal source in each candidate terminal pair within a consecutive preset number of superframe periods, and arranges them in the order of the superframe periods to form a first fluctuation sequence of the main peak amplitude of the main signal source; at the same time, it extracts the main peak amplitude of the channel impulse response of the interference signal source in the same candidate terminal pair within the same consecutive preset number of superframe periods, and arranges them in the same order of the superframe periods to form a second fluctuation sequence of the main peak amplitude of the interference signal source.

[0059] The terminal management device calculates the cross-correlation coefficient between the first and second fluctuation sequences. The cross-correlation coefficient is a parameter characterizing the degree of linear correlation between the two sequences, ranging from -1 to 1. A value closer to 1 indicates a higher degree of linear correlation, while a value closer to -1 indicates a higher degree of negative linear correlation. A value of 0 indicates no linear correlation between the two sequences. The calculation method is as follows: First, calculate the average of all values ​​in the first and second fluctuation sequences. Then, multiply the differences between the first and second fluctuation sequence values ​​and their average values ​​for each superframe period, and sum the products for all superframe periods. Simultaneously, calculate the sum of squares of the differences between the first and second fluctuation sequence values ​​and their average values, and take the square root of each sum before multiplying them. Finally, divide the sum of these products by the product of the square roots of the two sums to obtain the cross-correlation coefficient between the first and second fluctuation sequences.

[0060] Step 1043: Candidate terminal pairs with cross-correlation coefficients higher than a preset coherence threshold are identified as target terminals.

[0061] Optionally, the preset coherence threshold refers to the critical value used to determine whether there is a significant correlation between two fluctuation sequences. This threshold is preset according to the anti-interference requirements and channel characteristics of the VDES system, and is usually set to 0.7 to 0.8. It is used to screen out candidate terminal pairs whose signal strength fluctuations are significantly correlated.

[0062] The terminal management device compares the cross-correlation coefficient of each candidate terminal pair with a preset coherence threshold. If the cross-correlation coefficient is higher than the preset coherence threshold, it indicates that the signal intensity fluctuations of the main signal source and the interference signal source in the candidate terminal pair have a significant linear correlation. The signal propagation of the two is affected by the same electromagnetic environment or motion state on the sea surface, and the interference correlation is extremely strong. Such candidate terminal pairs are identified as target terminals.

[0063] Step 1044: Based on the geometric relationship between the geographic coordinate projection of the target terminal and the line-of-sight horizon of the shore-based base station, the target terminal whose geographic coordinate projection is located within the edge sector of the radar blind zone is identified as a potential interference source.

[0064] Optionally, the terminal management device acquires the geographic coordinates of the two VDES terminals in each target terminal. The geographic coordinates refer to the latitude and longitude information of the target terminal, which can be derived from the relative radial velocity and angle of arrival calculated in step 10, combined with the fixed geographic coordinates of the shore-based base station. Subsequently, the terminal management device projects the geographic coordinates of each target terminal onto the geographic coordinate system of the shore-based base station to obtain the geographic coordinate projection of the target terminal. The geographic coordinate projection refers to converting the actual geographic coordinates of the target terminal into planar coordinates with the shore-based base station as the origin, which facilitates the analysis of its geometric relationship with the line-of-sight horizon of the shore-based base station.

[0065] The terminal management device determines the line-of-sight horizon of the shore-based base station. The line-of-sight horizon refers to the boundary line of the maximum range that the shore-based base station can directly receive signals from due to the curvature of the Earth. Its location is determined by the antenna height of the shore-based base station and the radius of curvature of the Earth. Subsequently, the terminal management device analyzes the geometric relationship between the geographic coordinate projection of the target terminal and the line-of-sight horizon of the shore-based base station to determine the edge sector of the radar blind zone. The edge sector of the radar blind zone refers to the fan-shaped area located near the line-of-sight horizon where the shore-based base station has difficulty receiving signals stably, but the signals may reach the target area through beyond-line-of-sight propagation. This area is a high-incidence area for hidden nodes and beyond-line-of-sight interference.

[0066] The terminal management device determines whether the geographic coordinate projection of each target terminal is located within the edge sector of the radar blind zone. If the geographic coordinate projection of the target terminal is located within the sector, it indicates that the target terminal is a hidden node or a terminal that is prone to beyond-line-of-sight interference, and such target terminals are identified as potential interference sources.

[0067] This invention, through comprehensive analysis of signal parameters, geometric relationships, and wave characteristics, achieves accurate identification of potential interference sources, effectively eliminating terminals with no or low interference risk. It ensures that all identified potential interference sources are terminals that may cause signal collisions and beyond-line-of-sight interference, thus enabling targeted solutions to hidden node and beyond-line-of-sight interference problems. This improves the spectral efficiency of the VDES system, reduces the access conflict rate, and achieves efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0068] Optionally, the processes of steps 201 to 204 include: Step 201: Based on the time series nodes of the spatial displacement trajectory and the geometric boundary of the line-of-sight range, perform spatiotemporal coordinate mapping to obtain the terminal's geographical location coordinates corresponding to discrete time points. Based on the terminal's geographical location coordinates corresponding to discrete time points and the radius of curvature of the Earth, perform line-of-sight occlusion geometric determination to obtain the line-of-sight status of the VDES terminal relative to the shore-based base station at each discrete time point.

[0069] Optionally, the terminal management device extracts time-series nodes of the spatial displacement trajectory. A time-series node refers to dividing the entire superframe period into several continuous and equal discrete time points. Each time-series node corresponds to a time value. The number of divisions is set according to the motion speed and position accuracy requirements of the potential interference source, usually 10 to 20, to accurately capture the position changes of the potential interference source within the superframe period.

[0070] The line-of-sight range refers to the maximum distance at which a shore-based base station can directly receive VDES terminal signals under unobstructed conditions. This distance is determined by factors such as the antenna height of the shore-based base station and the curvature of the earth. Its geometric boundary refers to the circular boundary formed with the shore-based base station as the center and the maximum line-of-sight range as the radius. This boundary is precisely defined by geographical coordinates (latitude and longitude).

[0071] The terminal management device performs spatiotemporal coordinate mapping between the time series nodes of the spatial displacement trajectory and the geometric boundaries of the line-of-sight range. Spatiotemporal coordinate mapping refers to converting the relative position of the potential interference source corresponding to each time series node into the corresponding geographic coordinates (latitude and longitude). The conversion process combines the fixed geographic coordinates of the shore-based base station, the relative radial velocity of the potential interference source, and the angle of arrival to ensure that the terminal geographic location coordinates corresponding to each discrete time point are accurate, thus obtaining the terminal geographic location coordinates corresponding to each discrete time point.

[0072] The radius of curvature of the Earth refers to the radius of curvature of the Earth's surface curve. The average radius of curvature of the Earth, 6371 kilometers, is used for geometric determination of line-of-sight obstruction. Subsequently, the terminal management device performs geometric determination of line-of-sight obstruction based on the terminal's geographical location coordinates and the radius of curvature of the Earth at each discrete time point. Optionally, the determination method in this embodiment of the invention is as follows: using the antenna vertex of the shore-based base station and the VDES terminal position corresponding to the discrete time point as two endpoints, a virtual line of sight is drawn. It is determined whether the virtual line of sight is obstructed by the Earth's surface. If the virtual line of sight is not obstructed by the Earth's surface, it means that the VDES terminal is within the line-of-sight range of the shore-based base station, and the line-of-sight state is "line-of-sight"; if the virtual line of sight is obstructed by the Earth's surface, it means that the VDES terminal is outside the line-of-sight range of the shore-based base station, and the line-of-sight state is "obstructed". Finally, the line-of-sight state of the VDES terminal relative to the shore-based base station at each discrete time point is obtained.

[0073] Step 202: Based on the critical time point when the line-of-sight state changes from line-of-sight to occlusion and the direction of the motion vector of the spatial displacement trajectory, the boundary point of the entry blind zone is located to obtain the geographic coordinates of the entrance boundary of the dynamically occluded area.

[0074] Optionally, the terminal management device continuously compares the line-of-sight status at each discrete time point and filters out the critical time point when the line-of-sight status changes from line-of-sight to obstruction. The critical time point refers to the instant when the VDES terminal moves from the line-of-sight range of the shore-based base station to outside the line-of-sight range. The time point is between the last discrete time point when the line-of-sight status is line-of-sight and the first discrete time point when the line-of-sight status is obstruction.

[0075] The direction of the motion vector of the spatial displacement trajectory refers to the direction of motion of the potential interference source at the critical time point. It is determined by the spatial displacement trajectory predicted in step 20, specifically calculated by the difference in the terminal geographical coordinates of two adjacent discrete time points, which can accurately reflect the direction of movement of the potential interference source.

[0076] The terminal management device locates the boundary point of the blind zone based on the critical time point and the direction of the motion vector. Optionally, the positioning method of this embodiment is as follows: taking the geographical coordinates of the terminal corresponding to the critical time point as a reference, along the direction of the motion vector (i.e., the direction in which the VDES terminal moves away from the shore base station), combined with the curvature of the earth and the geometric boundary of the line-of-sight range, the geographical coordinates of the VDES terminal when it is just blocked by the curvature of the earth and the line-of-sight state changes to blockage for the first time are calculated. These coordinates are the geographical coordinates of the entrance boundary of the dynamic blockage area. The geographical coordinates of the entrance boundary refer to the boundary position when the VDES terminal enters the dynamic blockage area, and are used to define the starting range of the dynamic blockage area.

[0077] Step 203: Based on the critical time point when the line of sight changes from obstruction to line of sight and the direction of the motion vector of the spatial displacement trajectory, locate the exit boundary point of the blind zone to obtain the geographic coordinates of the exit boundary of the dynamically obstructed area.

[0078] Optionally, the terminal management device continuously compares the line-of-sight status at each discrete time point and filters out the critical time point when the line-of-sight status changes from obstruction to line-of-sight. The critical time point refers to the instant when the VDES terminal moves from outside the line-of-sight range of the shore-based base station to within the line-of-sight range, which is between the last discrete time point when the line-of-sight status is obstruction and the first discrete time point when the line-of-sight status is line-of-sight.

[0079] The terminal management device locates the boundary point of leaving the blind zone based on the critical time point and the direction of the motion vector. Optionally, the positioning method of this embodiment is as follows: taking the terminal's geographical location coordinates corresponding to the critical time point as a reference, along the direction of the motion vector (i.e., the direction in which the VDES terminal approaches the shore-based base station), combined with the curvature of the earth and the geometric boundary of the line-of-sight range, the geographical location coordinates of the VDES terminal when it just leaves the earth's curvature obstruction and the line-of-sight state changes to line-of-sight for the first time are calculated. These coordinates are the geographical coordinates of the exit boundary of the dynamic obstruction area. The geographical coordinates of the exit boundary refer to the boundary position when the VDES terminal leaves the dynamic obstruction area, and are used to define the termination range of the dynamic obstruction area.

[0080] Step 204: Based on the geographic coordinates of the entrance boundary, the geographic coordinates of the exit boundary, and the continuous path segment of the spatial displacement trajectory between the two, perform blind zone trajectory analysis to obtain a spatial conflict map.

[0081] Optionally, the continuous path segment in the spatial displacement trajectory located between the geographic coordinates of the entrance boundary and the geographic coordinates of the exit boundary refers to the complete path along the spatial displacement trajectory of the VDES terminal from entering the dynamic masking area to leaving the dynamic masking area. The terminal management device performs blind zone trajectory analysis based on the geographic coordinates of the entrance boundary, the geographic coordinates of the exit boundary, and the continuous path segment of the spatial displacement trajectory between the two to obtain a spatial conflict map, as described in steps 2041 to 2044.

[0082] This invention, based on spatiotemporal coordinate mapping, geometric determination, and boundary positioning, accurately defines the complete geographical range of the dynamic shielding area and presents the movement trajectory of potential interference sources within the dynamic shielding area. Simultaneously, by combining the line-of-sight range of shore-based base stations, it constructs a spatial conflict map that accurately reflects hidden nodes and potential beyond-line-of-sight interference areas. This solves the deficiency of being unable to detect remotely hidden nodes, ensuring targeted isolation of beyond-line-of-sight interference at the spatial level. This improves the spectral efficiency of the VDES system, reduces the access conflict rate, and achieves efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0083] Optionally, the process of steps 2041 to 2044 includes: Step 2041: Based on the geographic coordinates of the entrance boundary, the geographic coordinates of the exit boundary, and the continuous path segment of the spatial displacement trajectory between the two, the blind zone trajectory is extracted to obtain the motion path segment of the potential interference source within the dynamic shading area.

[0084] Optionally, the terminal management device performs blind zone trajectory extraction on continuous path segments. The extraction process involves: removing portions of the continuous path segment that exceed the geographical coordinates of the entrance and exit boundaries, retaining only path segments located between the two boundaries, and simultaneously smoothing the path segments to remove abnormal points caused by motion fluctuations, thereby obtaining the motion path segments of the potential interference source within the dynamic shielding area. The motion path segments refer to simplified line segments of the potential interference source's trajectory within the dynamic shielding area, accurately reflecting the motion path and azimuth changes of the potential interference source within that area.

[0085] Step 2042: Calculate the vertical deviation distance between the position coordinates of each sampling point on the motion path segment and the outer edge tangent of the line-of-sight range of the shore-based base station to obtain the occlusion depth value of each sampling point on the motion path segment relative to the line-of-sight boundary.

[0086] Optionally, the terminal management device performs uniform sampling on the motion path segment. The sampling interval is set according to the length of the motion path segment and the positioning accuracy requirements. Typically, one point is sampled every 0.1 nautical miles to obtain each sampling point on the motion path segment, and the location coordinates (latitude and longitude) of each sampling point are recorded at the same time.

[0087] The outer edge tangent of the line-of-sight range of a shore-based base station refers to the straight line tangent to the circular boundary of the line-of-sight range, centered on the shore-based base station. Each tangent corresponds to a specific azimuth angle, used to characterize the outermost boundary of the line-of-sight range. Subsequently, the terminal management device calculates the vertical deviation distance between the position coordinates of each sampling point on the motion path segment and the outer edge tangent. The vertical deviation distance refers to the shortest straight-line distance from the sampling point to the outer edge tangent. The calculation method is as follows: starting from the sampling point, draw a perpendicular line to the outer edge tangent of the line-of-sight range, and measure the length of the perpendicular line, which is the vertical deviation distance.

[0088] The terminal management device determines the vertical deviation distance of each sampling point as the occlusion depth value of that sampling point relative to the line-of-sight boundary. The occlusion depth value refers to the degree to which the sampling point (i.e., the potential interference source) is occluded by the curvature of the earth. The larger the value, the deeper the potential interference source is occluded and the farther it is inside the dynamic occlusion area; the smaller the value, the closer the potential interference source is to the line-of-sight boundary and the shallower the occlusion.

[0089] Step 2043: Based on the shielding depth value and the atmospheric refractive index of the sea surface, the maximum beyond-line-of-sight propagation curvature radius of the electromagnetic wave is determined by the angle projection of the interference sector to obtain the geographical azimuth interval where the signal superposition exists within the dynamic shielding area.

[0090] Optionally, the maximum beyond-line-of-sight propagation radius of electromagnetic waves refers to the radius corresponding to the path curvature of electromagnetic waves when they achieve beyond-line-of-sight propagation under the current sea surface atmospheric refractive index conditions. It is calculated by combining sea surface atmospheric refractive index parameters with the propagation law of electromagnetic waves and is used to determine the coverage range of electromagnetic wave beyond-line-of-sight propagation. Interference sector angle projection is performed based on the shielding depth value of each sampling point and the maximum beyond-line-of-sight propagation radius of electromagnetic waves. The projection process is as follows: using each sampling point as a reference, the coverage angle range of electromagnetic wave beyond-line-of-sight propagation is determined by combining the shielding depth value. The larger the shielding depth value, the smaller the coverage angle range; the smaller the shielding depth value, the larger the coverage angle range. Simultaneously, the coverage angle range is corrected by combining the maximum beyond-line-of-sight propagation radius of electromagnetic waves to ensure that the angle range accurately reflects the area where signal superposition may occur during electromagnetic wave beyond-line-of-sight propagation.

[0091] The terminal management device integrates the coverage angle ranges corresponding to all sampling points, removes overlapping and redundant parts, and obtains the geographical azimuth angle range where signals superimpose within the dynamic masking area. Therefore, the geographical azimuth angle range refers to the azimuth angle range centered on the shore base station that can receive signals propagating beyond line of sight from potential interference sources and where signal superposition may occur. It is used to identify the interference risk area within the dynamic masking area.

[0092] Step 2044: Based on the geographical azimuth interval and the polar coordinate system of the shore-based base station, perform spatial region mapping to obtain a spatial conflict map.

[0093] Optionally, the polar coordinate system is a coordinate system with the shore-based base station as the origin, the north direction of the shore-based base station as the polar axis, the distance from the shore-based base station to the target point as the polar radius, and the angle of the target point relative to the polar axis as the polar angle. It is used to accurately represent the relative positions of various points within the sea area. The terminal management device performs spatial region mapping between the geographic azimuth interval and the polar coordinate system of the shore-based base station. The mapping process is as follows: the geographic azimuth interval is converted into a polar angle range in the polar coordinate system. Combined with the shading depth value and polar radius (i.e., the distance from the sampling point to the shore-based base station) of each sampling point, the polar radius range corresponding to each geographic azimuth interval is determined, thereby defining a specific spatial region in the polar coordinate system.

[0094] The terminal management device integrates information such as the boundaries of the spatial area and the dynamic shielding area (geographic coordinates of the entrance and exit boundaries), the movement path segments of potential interference sources, etc., and marks the line-of-sight range of the shore-based base station to form a spatial distribution map that can intuitively present the interference risk area, the movement trajectory of potential interference sources and the line-of-sight boundary within the dynamic shielding area. This spatial distribution map is the spatial conflict map.

[0095] This invention, through path extraction, distance calculation, angle projection, and coordinate mapping, achieves precise delineation of interference risk areas within a dynamically shielded region. The constructed spatial conflict map can present the movement trajectory of potential interference sources, line-of-sight boundaries, and high-incidence areas of interference, ensuring targeted isolation of beyond-line-of-sight interference at the spatial level. This improves the spectrum efficiency of the VDES system, reduces the access conflict rate, and enables efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0096] Optionally, the processes of steps 401 to 404 include: Step 401: Based on the number density of potential interference sources in each time slot multiplexing domain, determine the time slot contention level of each time slot multiplexing domain, and allocate an exclusive time slot pool for the first time slot multiplexing domain with a time slot contention level greater than or equal to a preset level threshold, and allocate a shared time slot pool that can be called by the first time slot multiplexing domain for the second time slot multiplexing domain with a time slot contention level less than the preset level threshold.

[0097] Optionally, the preset time slot contention level classification standard is set according to the number density range of potential interference sources, and is usually divided into three levels: low contention, medium contention and high contention. Low contention corresponds to the open sea area time slot reuse domain with a small number density, high contention corresponds to the port area time slot reuse domain with a large number density, and medium contention corresponds to the time slot reuse domain between the two.

[0098] The terminal management device compares the number density of potential interference sources in each time slot multiplexing domain with the preset level classification standard to determine the time slot contention level corresponding to each time slot multiplexing domain.

[0099] The level threshold refers to the critical value used to distinguish between high and medium-low competition levels. The terminal management device compares the time slot competition level of each time slot multiplexing domain with the preset level threshold, and filters out time slot multiplexing domains with a time slot competition level greater than or equal to the preset level threshold. These time slot multiplexing domains are identified as the first time slot multiplexing domain. The first time slot multiplexing domain is usually an area with a large number of potential interference sources and a high risk of signal collision (such as near a port). The terminal management device allocates an exclusive time slot pool to each first time slot multiplexing domain. An exclusive time slot pool refers to a set of time slots specifically allocated to the first time slot multiplexing domain and not allowed to be occupied by other time slot multiplexing domains. The number of time slots in this time slot pool is determined based on the number of VDES terminals, the density of potential interference sources, and the total amount of spectrum resources in the first time slot multiplexing domain, ensuring that the access needs of all VDES terminals in the domain can be met, while avoiding time slot conflicts with other domains.

[0100] The terminal management device filters out time slot multiplexing domains with a time slot contention level lower than a preset level threshold. These time slot multiplexing domains are designated as second time slot multiplexing domains. Second time slot multiplexing domains are typically areas with few potential interference sources and low signal conflict risk (such as open sea areas). A shared time slot pool is allocated to all second time slot multiplexing domains. The shared time slot pool refers to a set of time slots that can be used by all second time slot multiplexing domains and can be called by the first time slot multiplexing domain when time slot resources are scarce. The number of time slots in this time slot pool is determined based on the total access demand of all second time slot multiplexing domains and the remaining spectrum resources, thereby realizing flexible reuse of time slot resources.

[0101] Step 402: Construct a time slot bitmap matrix based on the exclusive time slot pool and the shared time slot pool.

[0102] Optionally, the terminal management device constructs a time slot bitmap matrix based on the exclusive time slot pool and the shared time slot pool, as described in steps 4021 to 4025.

[0103] Step 403: Based on the indexes of unoccupied free time slots in the time slot bitmap matrix, generate a time slot offset instruction for each VDES terminal within the time slot multiplexing domain. The time slot offset instruction is used to adjust the local time slot counter of the VDES terminal to avoid the transmission window of potential interference sources.

[0104] Optionally, the terminal management device parses the time slot bitmap matrix, extracts all unoccupied idle time slots, and records the time slot index corresponding to each idle time slot. The time slot index refers to the sequence number used to uniquely identify each time slot, and is numbered sequentially according to the time order of the time slots, so as to facilitate the terminal management device to quickly locate and call up idle time slots.

[0105] For each time slot multiplexing domain, the terminal management device filters out the available idle time slot indexes for that domain and, combined with the transmission windows of potential interference sources within that domain, generates a time slot offset command for each VDES terminal within that domain. The transmission window of a potential interference source refers to a preset signal transmission time interval for that source, determined by the time slot allocation of that source. The time slot offset command is a control command used to adjust the local time slot counter of the VDES terminal, adjusting its signal transmission time to avoid the transmission windows of potential interference sources and prevent signal collisions.

[0106] The method for generating the time slot offset command is as follows: The terminal management device calculates the time offset that the terminal needs to adjust based on the preset transmission time slot of each VDES terminal and the transmission window of the potential interference source in the time slot multiplexing domain where the terminal is located. The value of the time offset is the time difference between the preset transmission time slot and the idle time slot, ensuring that the transmission time of the VDES terminal after adjustment falls within the idle time slot and does not overlap with the transmission window of the potential interference source.

[0107] The terminal management device encapsulates the time offset into a time slot offset instruction. Each VDES terminal corresponds to a unique time slot offset instruction, ensuring the instruction's relevance and accuracy.

[0108] Step 404: The time slot offset command is encapsulated into a VDES management message and broadcast to each VDES terminal in the corresponding time slot multiplexing domain through the downlink control channel of the shore base station. The same time slot offset command is also synchronously sent to VDES terminals located in the dynamic masking area based on the satellite link.

[0109] Optionally, the terminal management device encapsulates the time slot offset instruction for each VDES terminal within each time slot multiplexing domain into a VDES management message. The VDES management message refers to the control message used to implement VDES terminal access management, which includes key information such as terminal identifier, time slot offset, and execution time, to ensure that the VDES terminal can accurately identify and execute the instruction.

[0110] The terminal management device broadcasts the encapsulated VDES management message to each VDES terminal in the corresponding time slot multiplexing domain through the downlink control channel of the shore base station. The downlink control channel is a dedicated channel for the shore base station to send control messages to the VDES terminal. It has the characteristics of stable transmission and low latency, and can ensure that the message is transmitted quickly and accurately to the VDES terminal in the non-dynamic masking area.

[0111] The terminal management device identifies VDES terminals located within dynamic shielding areas. Due to the curvature of the Earth, these terminals may be unable to stably receive messages transmitted via the downlink control channel of the shore-based base station. The terminal management device synchronously sends the same timeslot offset command to these VDES terminals within the dynamic shielding area via a satellite link. The satellite link has wide coverage and is unaffected by the curvature of the Earth, ensuring that VDES terminals within the dynamic shielding area can accurately receive the timeslot offset command, thus achieving synchronized scheduling of all VDES terminals.

[0112] This invention, relying on differentiated time slot allocation, intuitive time slot management, precise command generation, and multi-link delivery, achieves efficient access scheduling for VDES terminals within each time slot reuse domain. It satisfies the high access demands of high-competition areas and avoids signal conflicts, while also enabling time slot resource reuse in low-competition areas. It integrates idle resources in sparse sea areas and fragmented time slots in high-density areas, solving the defects of fragmented spatiotemporal resources and low utilization rate. This improves the spectrum efficiency of the VDES system, reduces the access conflict rate, and achieves efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0113] Optionally, the process of steps 4021 to 4025 includes: Step 4021: Based on the central geographic coordinates of each first time slot multiplexing domain in the exclusive time slot pool and the maximum line-of-sight radius of the shore-based base station, calculate the coverage sector boundary corresponding to the first type of time slot index in each exclusive time slot pool, and project the coverage sector boundary onto a two-dimensional geographic grid to obtain the exclusive space mask layer.

[0114] Optionally, the terminal management device extracts the central geographic coordinates of each first time slot multiplexing domain. The central geographic coordinates refer to the latitude and longitude information of the geometric center of each first time slot multiplexing domain, calculated using the boundary geographic coordinates of the time slot multiplexing domain. Specifically, the calculation method is as follows: take the average latitude and longitude of all boundary geographic coordinates of the time slot multiplexing domain, and use the coordinates corresponding to these two averages as the central geographic coordinates of the first time slot multiplexing domain. The maximum line-of-sight radius refers to the maximum distance at which the shore-based base station can directly receive VDES terminal signals under unobstructed conditions. This distance is determined by factors such as the antenna height of the shore-based base station and the radius of curvature of the Earth, and is the radius of the line-of-sight range of the shore-based base station.

[0115] The terminal management device calculates the coverage sector boundary corresponding to the first type of time slot index in each exclusive time slot pool based on the central geographic coordinates of each first time slot multiplexing domain and the maximum line-of-sight radius of the shore-based base station. The calculation method is as follows: taking the central geographic coordinates of the first time slot multiplexing domain as the vertex and the maximum line-of-sight radius of the shore-based base station as the radius, combined with the geographical range of the first time slot multiplexing domain, the fan-shaped area that the exclusive time slot pool can cover is delineated. The boundary of the fan-shaped area is the coverage sector boundary, which is used to define the signal coverage range corresponding to the exclusive time slot pool.

[0116] A two-dimensional geographic grid refers to dividing the entire sea area covered by a shore-based base station into several equal square grids. Each grid corresponds to a fixed geographic range, and the size of the grid is set according to the positioning accuracy requirements, typically 0.01 square nautical miles per grid. Subsequently, the terminal management device projects the coverage sector boundary of each exclusive time slot pool onto this two-dimensional geographic grid, marking the area within the coverage sector boundary within the grid as the exclusive available area, and the remaining area as the non-exclusive area, forming a layer that can intuitively show the coverage range of each exclusive time slot pool. This layer is the exclusive spatial mask layer.

[0117] Step 4022: Based on the spatial overlap relationship between the predicted trajectory of potential interference sources in each second time slot multiplexing domain in the shared time slot pool and the exclusive space mask layer, the geographical intersection areas that are in the line-of-sight blind zone due to the curvature of the earth but have superimposed signals beyond the line of sight are identified, and a shared conflict hotspot map is obtained.

[0118] Optionally, the terminal management device extracts the predicted trajectory of the potential interference source in each second time slot multiplexing domain. The predicted trajectory is the spatial displacement trajectory of the potential interference source predicted in step 20 in the next superframe period, which can accurately reflect the motion path and position change of the potential interference source in the second time slot multiplexing domain.

[0119] The terminal management device performs spatial overlap analysis on the predicted trajectory of potential interference sources in each second time slot multiplexing domain and the exclusive space mask layer. The spatial overlap analysis refers to determining whether the area traversed by the predicted trajectory of the potential interference source overlaps with the exclusive available area in the exclusive space mask layer. At the same time, it combines the curvature of the earth to determine whether the overlapping area is in the line-of-sight blind zone of the shore-based base station.

[0120] The terminal management device identifies geographically overlapping regions where signals from potential interfering sources overlap with signals from VDES terminals within the exclusive time slot pool, even though these regions are located in line-of-sight blind zones due to Earth's curvature. These geographically overlapping regions refer to marine areas within the second time slot multiplexing domain where the predicted trajectories of potential interfering sources overlap with the exclusive space mask layer and are located in line-of-sight blind zones. Such areas are prone to beyond-line-of-sight signal collisions and are considered high-incidence interference areas. The terminal management device integrates all identified geographically overlapping regions, marking the location coordinates, overlap range, and potential interference intensity of each region to form a map that visually represents the distribution of high-incidence interference areas within the shared time slot pool. This map is the shared conflict hotspot map.

[0121] Step 4023: Based on the signal propagation delay difference in geographically overlapping areas in the shared conflict hotspot map, the second type of time slot index in the shared time slot pool is hierarchically clustered according to the delay gradient, so that the time windows of the signals corresponding to the time slot indexes in the same level arrive at the shore base station do not overlap, thus obtaining a hierarchical shared time slot cluster.

[0122] Optionally, the terminal management device extracts the signal propagation delay difference for each geographically overlapping region in the shared conflict hotspot map. The signal propagation delay difference refers to the difference between the propagation delay of the signal from the potential interference source in the geographically overlapping region to the shore-based base station and the propagation delay of the signal from the VDES terminal corresponding to the shared time slot pool in the region to the shore-based base station. The calculation method is as follows: subtract the propagation delay of the VDES terminal signal in the shared time slot pool from the propagation delay of the potential interference source signal to obtain the signal propagation delay difference.

[0123] The terminal management device performs hierarchical clustering of the second type of time slot indexes in the shared time slot pool according to the gradient of the signal propagation delay difference. The hierarchical clustering process is as follows: the delay gradient interval is set according to the protection interval of the VDES system, usually 1 microsecond to 2 microseconds, and the signal propagation delay difference is divided into several delay levels according to the gradient interval; then, the signal propagation delay difference corresponding to each second type of time slot index is assigned to the corresponding delay level, ensuring that the signal propagation delay difference corresponding to all second type of time slot indices in the same delay level is within the same gradient interval; finally, the time windows of the signals corresponding to the time slot indices in the same level arrive at the shore base station do not overlap. The set of second type of time slot indices corresponding to each delay level is a hierarchical shared time slot cluster, and all hierarchical shared time slot clusters together constitute the hierarchical shared time slot structure.

[0124] Step 4024: Based on the first type of time slot index in the exclusive space mask layer and the second type of time slot index in the hierarchical shared time slot cluster, establish an interference chain mapping relationship with geographical intersection areas as nodes, associate the second type of time slot index with over-line-of-sight superposition to the first type of time slot index affected by it, and obtain a directed topological connection table.

[0125] Optionally, the terminal management device establishes an interference chain mapping relationship using each geographical intersection area in the shared conflict hotspot map as a node. This interference chain mapping relationship reflects the interference correlation between different time slot indices. Specifically, the process involves determining whether a second-type time slot index in each hierarchical shared time slot cluster will cause signal superposition interference to a first-type time slot index in the exclusive space mask layer through beyond-line-of-sight propagation. If interference exists, a correlation is established between the second-type time slot index and the affected first-type time slot index. The terminal management device integrates all correlations with beyond-line-of-sight superposition interference to form a directed topology connection table. This table records the affected first-type time slot index corresponding to each second-type time slot index, as well as the direction of interference (from the second-type time slot index to the affected first-type time slot index), clearly presenting the interference correlation between time slot indices.

[0126] Step 4025: Based on the hierarchical structure of the node connection order and temporal orthogonality attribute in the directed topology connection table, the exclusive time slot index and the hierarchical shared time slot cluster are mapped to the row vector and column vector of the matrix to generate a time slot bitmap matrix in which the row vector represents the spatial exclusive level and the column vector represents the temporal shared level.

[0127] Optionally, the terminal management device extracts the node connection order from the directed topology connection table. The node connection order refers to the interference association order between nodes in the geographically overlapping area. At the same time, it extracts the hierarchical structure of the temporal orthogonality attribute of the hierarchical shared time slot cluster. The temporal orthogonality attribute refers to the attribute that the time slots of different hierarchical shared time slot clusters do not overlap in the time dimension. The hierarchical structure is the delay hierarchy structure formed in step 4023.

[0128] The terminal management device maps the first type of time slot index in the exclusive time slot pool to the row vectors of the matrix. The row vectors represent the spatial exclusive level, and each row vector corresponds to a first type of time slot index, representing the spatial coverage attribute of the exclusive time slot. The device maps the second type of time slot index in the hierarchical shared time slot cluster to the column vectors of the matrix. The column vectors represent the temporal sharing level, and each column vector corresponds to a hierarchical shared time slot cluster, representing the temporal hierarchical attribute of the shared time slot. Based on the mapping relationship between the row vectors and column vectors, and combined with the interference association relationship in the directed topology connection table, the device marks the interference association status, time slot occupancy status (occupied, idle) and usage permission between each first type of time slot index and the second type of time slot index in the matrix with preset identifiers. Finally, a time slot bitmap matrix is ​​generated in which the row vectors represent the spatial exclusive level and the column vectors represent the temporal sharing level.

[0129] This invention, based on spatial coverage analysis, interference area location, time slot hierarchical clustering, interference correlation mapping, and matrix mapping, constructs a time slot bitmap matrix that clearly presents the spatial attributes, temporal attributes, and interference correlation status of time slot resources. This solves the shortcomings of inaccurate time slot resource management and difficulty in avoiding beyond-line-of-sight time slot interference, ensuring that access scheduling can specifically avoid interference, improving time slot resource utilization and the stability of VDES terminal access, thereby improving the spectrum efficiency of the VDES system, reducing the access conflict rate, and realizing efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0130] Furthermore, the VDES terminal access management device based on satellite and shore-based base station collaboration provided by the present invention will be described below, which can be referred to in correspondence with the VDES terminal access management method based on satellite and shore-based base station collaboration described above.

[0131] Optionally, refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of the VDES terminal access management device based on satellite and shore-based base station collaboration provided by the present invention. The VDES terminal access management device based on satellite and shore-based base station collaboration includes: The interference source localization module 210 is used to calculate the relative radial velocity and time delay spread spectrum of each VDES terminal relative to the shore base station based on the angle of arrival and signal strength of the uplink signal received by the shore base station, combined with the global reference frame header timestamp broadcast by the satellite downlink, and to identify the subset of terminals with interference based on the multipath overlap relationship of the time delay spread spectrum, so as to obtain the potential interference source. The conflict map construction module 220 is used to predict the spatial displacement trajectory of a potential interference source in the next superframe period based on its relative radial velocity, and to construct a spatial conflict map containing dynamic occlusion areas based on the line-of-sight range between the spatial displacement trajectory and the shore-based base station. The sea area division module 230 is used to generate a protective isolation zone based on the boundary of the dynamically masked area in the spatial conflict map, and divide the sea area covered by the protective isolation zone into a time slot multiplexing domain. The terminal access scheduling module 240 is used to schedule the access of VDES terminals in each time slot multiplexing domain based on the number density of potential interference sources in each time slot multiplexing domain.

[0132] This invention addresses two main issues. First, by using a spatial conflict map to accurately identify hidden nodes and beyond-line-of-sight (BOS) interference risks within a dynamically shielded area, it spatially isolates interference by dividing the area into protective isolation zones and time slot reuse domains, thus avoiding BOS signal collisions and resolving the problems of hidden nodes and BOS interference. Second, by scheduling access based on the density of potential interference sources, it integrates and optimizes idle resources in sparse sea areas and fragmented time slots in high-density areas, resolving the problem of spatiotemporal resource fragmentation. This solves the technical problems of high access conflict rate and low spectral efficiency of VDES terminals caused by beyond-line-of-sight interference from hidden nodes and spatiotemporal resource fragmentation in the background technology, achieving efficient spectrum reuse access for VDES terminals under complex sea conditions.

[0133] Please see Figure 3 , Figure 3 An embodiment diagram of an electronic device provided in accordance with the present invention. For example... Figure 3 As shown, an embodiment of the present invention provides an electronic device 300, including a memory 310, a processor 320, and a computer program 311 stored in the memory 310 and executable on the processor 320. When the processor 320 executes the computer program 311, it implements the processes of steps 10 to 40.

[0134] Please see Figure 4 , Figure 4 An embodiment diagram of a computer-readable storage medium provided in accordance with an embodiment of the present invention is shown. Figure 4 As shown, this embodiment provides a computer-readable storage medium 400 on which a computer program 311 is stored. When the computer program 311 is executed by a processor, it implements the processes of steps 10 to 40.

[0135] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the VDES terminal access management method based on satellite and shore-based base station collaboration provided by the above methods, which includes steps 10 to 40.

[0136] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0137] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A VDES terminal access management method based on satellite and shore-based base station collaboration, characterized in that, include: Based on the angle of arrival and signal strength of the uplink signal received by the VDES terminal from the shore-based base station, combined with the global reference frame header timestamp broadcast by the satellite downlink, the relative radial velocity and delay spread spectrum of each VDES terminal relative to the shore-based base station are calculated, and the subset of terminals with interference are identified based on the multipath overlap relationship of the delay spread spectrum, thus obtaining potential interference sources. Based on the relative radial velocity of the potential interference source, predict its spatial displacement trajectory in the next superframe period, and based on the line-of-sight range of the spatial displacement trajectory and the shore-based base station, construct a spatial conflict map containing dynamic shading areas. Based on the boundaries of the dynamically masked areas in the spatial conflict map, a protective isolation zone is generated, and the sea area covered by the protective isolation zone is divided into a time-slot multiplexing domain. Based on the number density of potential interference sources within each time slot multiplexing domain, access scheduling is performed for VDES terminals within each time slot multiplexing domain.

2. The VDES terminal access management method based on satellite and shore-based base station collaboration according to claim 1, characterized in that, The access scheduling of VDES terminals in each time slot multiplexing domain based on the number density of potential interference sources in each time slot multiplexing domain includes: Based on the number density of potential interference sources in each time slot multiplexing domain, the time slot contention level of each time slot multiplexing domain is determined, and an exclusive time slot pool is allocated to the first time slot multiplexing domain with a time slot contention level greater than or equal to a preset level threshold. For the second time slot multiplexing domain with a time slot contention level less than a preset level threshold, a shared time slot pool that can be called by the first time slot multiplexing domain is allocated. Based on the exclusive time slot pool and the shared time slot pool, a time slot bitmap matrix is ​​constructed; Based on the index of the unoccupied free time slots in the time slot bitmap matrix, a time slot offset instruction is generated for each VDES terminal in the time slot multiplexing domain; the time slot offset instruction is used to adjust the local time slot counter of the VDES terminal to avoid the transmission window of potential interference sources. The time slot offset command is encapsulated into a VDES management message and broadcast to each VDES terminal in the corresponding time slot multiplexing domain through the downlink control channel of the shore base station. The same time slot offset command is also synchronously sent to VDES terminals located in the dynamic masking area based on the satellite link.

3. The VDES terminal access management method based on satellite and shore-based base station collaboration according to claim 2, characterized in that, The construction of a time slot bitmap matrix based on the exclusive time slot pool and the shared time slot pool includes: Based on the central geographic coordinates of each first time slot multiplexing domain in the exclusive time slot pool and the maximum line-of-sight radius of the shore-based base station, the coverage sector boundary corresponding to the first type of time slot index in each exclusive time slot pool is calculated, and the coverage sector boundary is projected onto a two-dimensional geographic grid to obtain an exclusive space mask layer. Based on the spatial overlap relationship between the potential interference source prediction trajectory of each second time slot multiplexing domain in the shared time slot pool and the exclusive space mask layer, the geographical intersection area that is in the line-of-sight blind zone due to the curvature of the earth but has superposition of beyond-line-of-sight signals is identified, and a shared conflict hotspot map is obtained. Based on the signal propagation delay difference in geographically overlapping areas in the shared conflict hotspot map, the second type of time slot index in the shared time slot pool is hierarchically clustered according to the delay gradient, so that the time windows of the signals corresponding to the time slot index in the same level arrive at the shore base station do not overlap, thus obtaining a hierarchical shared time slot cluster. Based on the first type of time slot index in the exclusive space mask layer and the second type of time slot index in the hierarchical shared time slot cluster, an interference chain mapping relationship with geographical intersection areas as nodes is established. The second type of time slot index with over-line-of-sight superposition is associated with the first type of time slot index affected by it, and a directed topological connection table is obtained. Based on the hierarchical structure of the node connection order and temporal orthogonality attribute in the directed topological connection table, the exclusive time slot index and the hierarchical shared time slot cluster are mapped to the row vectors and column vectors of the matrix to generate a time slot bitmap matrix where the row vectors represent the spatial exclusive level and the column vectors represent the temporal shared level.

4. The VDES terminal access management method based on satellite and shore-based base station collaboration according to claim 1, characterized in that, The construction of a spatial conflict map containing dynamically obscured areas based on the spatial displacement trajectory and the line-of-sight range of the shore-based base station includes: Based on the time series nodes of the spatial displacement trajectory and the geometric boundary of the line-of-sight range, spatiotemporal coordinate mapping is performed to obtain the terminal geographical location coordinates corresponding to discrete time points. Based on the terminal geographical location coordinates corresponding to discrete time points and the radius of curvature of the earth, line-of-sight occlusion geometry is determined to obtain the line-of-sight status of the VDES terminal relative to the shore-based base station at each discrete time point. Based on the critical time point when the line of sight changes from open to closed and the direction of the motion vector of the spatial displacement trajectory, the boundary point of the entry blind zone is located to obtain the geographic coordinates of the entrance boundary of the dynamic occlusion area. Based on the critical time point when the line of sight changes from obstruction to line of sight and the direction of the motion vector of the spatial displacement trajectory, the exit boundary point of the blind zone is located to obtain the geographical coordinates of the exit boundary of the dynamic obstruction area. The spatial conflict map is obtained by performing blind zone trajectory analysis based on the geographic coordinates of the entrance boundary, the geographic coordinates of the exit boundary, and the continuous path segment of the spatial displacement trajectory between them.

5. The VDES terminal access management method based on satellite and shore-based base station collaboration according to claim 4, characterized in that, The spatial conflict map is obtained by performing blind zone trajectory analysis based on the geographic coordinates of the entrance boundary, the geographic coordinates of the exit boundary, and the continuous path segment of the spatial displacement trajectory between the two, including: Based on the geographic coordinates of the entrance boundary, the geographic coordinates of the exit boundary, and the continuous path segment of the spatial displacement trajectory between the two, the blind zone trajectory is extracted to obtain the motion path segment of the potential interference source in the dynamic shielding area. The vertical deviation distance between the position coordinates of each sampling point on the motion path segment and the outer edge tangent of the line-of-sight range of the shore-based base station is calculated to obtain the occlusion depth value of each sampling point on the motion path segment relative to the line-of-sight boundary. Based on the maximum beyond-line-of-sight propagation curvature radius of electromagnetic waves determined by the shielding depth and the atmospheric refractive index of the sea surface, the angle projection of the interference sector is used to obtain the geographical azimuth interval where signals superimpose within the dynamic shielding area. The spatial conflict map is obtained by mapping the geographical azimuth interval to the polar coordinate system of the shore-based base station.

6. The VDES terminal access management method based on satellite and shore-based base station collaboration according to claim 1, characterized in that, The identification of a subset of interfering terminals based on the multipath overlap relationship of the time delay spread spectrum, to obtain potential interference sources, includes: Based on the phase angle of the complex gain value of each multipath component in the time delay spread spectrum, calculate the difference vector of the phase angle within two adjacent VDES signal periods; The multipath component whose magnitude exceeds the Doppler frequency tolerance range is taken as the target component. Based on the carrier frequency offset of the main path component in the target component, the carrier frequency offset of the signal of other VDES terminals in the same receiving time slot is retrieved. VDES terminal pairs whose carrier frequency offset difference is less than the receiver intermediate frequency filter bandwidth are identified as the first interfering terminal pair, and the angular distance between the two uplink signals is calculated based on the estimated angle of arrival of the two VDES terminals in the first interfering terminal pair. The potential interference sources are determined based on the angular distance of each first interference terminal pair and the half-power beamwidth of the antenna array of the shore-based base station.

7. The VDES terminal access management method based on satellite and shore-based base station collaboration according to claim 6, characterized in that, The determination of the potential interference source based on the angular distance of each first pair of interfering terminals and the half-power beamwidth of the antenna array of the shore-based base station includes: The first interference terminal pair with an angular distance less than the half-power beamwidth is designated as the second interference terminal pair. Based on the relative time delay difference between the interference source and the main signal source in the second interference terminal pair, the second interference terminal pair with a relative time delay difference greater than zero and less than the VDES protection interval is determined as the candidate terminal pair. Based on the fluctuation trend of the main peak amplitude of the channel impulse response of each candidate terminal within a consecutive preset number of superframe periods, the cross-correlation coefficient between the first fluctuation sequence of the main peak amplitude of the main signal source and the second fluctuation sequence of the main peak amplitude of the interference signal source is calculated. Candidate terminal pairs with a cross-correlation coefficient higher than a preset coherence threshold are identified as target terminals; Based on the geometric relationship between the geographic coordinate projection of the target terminal and the line-of-sight horizon of the shore-based base station, the target terminal whose geographic coordinate projection is located within the edge sector of the radar blind zone is identified as the potential interference source.

8. A VDES terminal access management device based on satellite and shore-based base station collaboration, characterized in that, The apparatus is used to implement the VDES terminal access management method based on satellite and shore-based base station collaboration as described in any one of claims 1 to 7; the apparatus includes: The interference source localization module is used to calculate the relative radial velocity and delay spread spectrum of each VDES terminal relative to the shore base station based on the angle of arrival and signal strength of the uplink signal received by the shore base station, combined with the global reference frame header timestamp broadcast by the satellite downlink, and to identify the subset of terminals with interference based on the multipath overlap relationship of the delay spread spectrum, thereby obtaining potential interference sources. The conflict map construction module is used to predict the spatial displacement trajectory of the potential interference source in the next superframe period based on the relative radial velocity of the source, and to construct a spatial conflict map containing dynamic occlusion areas based on the line-of-sight range between the spatial displacement trajectory and the shore-based base station. The sea area division module is used to generate a protective isolation zone based on the boundary of the dynamically obscured area in the spatial conflict map, and divide the sea area covered by the protective isolation zone into a time slot multiplexing domain. The terminal access scheduling module is used to schedule the access of VDES terminals in each time slot multiplexing domain based on the number density of potential interference sources in each time slot multiplexing domain.

9. An electronic device, comprising: Memory, used to store computer software programs; A processor for reading and executing the computer software program, characterized in that, when the processor executes the computer software program, it implements the VDES terminal access management method based on satellite and shore-based base station collaboration as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium, wherein a computer software program is stored therein, characterized in that, When the computer software program is executed by the processor, it implements the VDES terminal access management method based on satellite and shore-based base station collaboration as described in any one of claims 1 to 7.

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