A downlink selection method and system in a VDES multi-satellite coverage scenario

Abstract

The application provides a downlink selection method and system in a VDES multi-satellite coverage scenario, and belongs to the technical field of satellite communication. The method comprises the following steps: presetting ship platform context information and satellite ephemeris information in a VDES satellite core network; receiving a VDE point-to-point message carrying a target ship MMSI; querying a local cache to obtain a real-time position of the target ship platform and calculating a candidate satellite list currently covered; sending a paging request to each satellite payload in parallel for a multi-satellite coverage scenario; collecting multiple parameters such as signal strength and signal-to-noise ratio returned by each satellite payload; performing a normalized satellite selection algorithm based on multiple factors such as signal strength, signal-to-noise ratio, position in a sector coverage area, satellite height, coverage stability and the number of queued messages, calculating a comprehensive weighted score and selecting an optimal link; and sending a VDE point-to-point message through the optimal satellite payload. The application realizes dynamic and intelligent selection of an optimal downlink in a multi-satellite coverage scenario, effectively improves communication success rate and reliability, and reduces transmission delay.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology, and more particularly to a downlink selection method and system in a VDES multi-satellite coverage scenario. Background Technology

[0002] VDES is a new generation of ship communication system that integrates functions such as AIS (Automatic Identification System), ASM (Dedicated Message System), and VDE (Very High Frequency Data Exchange). It can effectively alleviate the data congestion problem of the existing AIS system and support high-speed data exchange between ship-to-shore, ship-to-ship, and ship-to-satellite.

[0003] In the open ocean, where there is no shore-based base station coverage, VDES shipborne terminals must communicate with shore-based application service platforms or other vessels via VDES satellite payloads. With the development of low-Earth orbit satellite constellations, it has become common for multiple satellite payloads to simultaneously provide signal coverage for the same sea area (i.e., the same shipborne terminal).

[0004] Existing downlink selection methods are relatively simple, typically employing one of the following approaches: Fixed satellite selection: This method pre-selects a specific satellite as a relay node, which lacks flexibility and can lead to communication failure or retransmission when the satellite's signal quality is poor.

[0005] Random satellite selection: The core network randomly selects a satellite that covers the target terminal to send messages, which cannot guarantee communication quality and reliability.

[0006] Based solely on coverage: The core network only determines "whether there is satellite coverage". As long as there is coverage from one satellite, it will transmit through that satellite, without comparing the signal quality differences under multiple satellite coverage.

[0007] The main problem with the above method is that in multi-satellite coverage scenarios, it fails to fully utilize the signal quality differences among multiple satellites to select the optimal downlink, resulting in large message transmission latency, low success rate, insufficient utilization of spectrum resources, and poor user experience. Summary of the Invention

[0008] To address the technical problem in existing technologies where the core network cannot dynamically and intelligently select the optimal downlink satellite link when sending VDE point-to-point messages to VDES shipborne terminals under multi-satellite coverage, resulting in poor communication quality and low success rate, this invention provides a downlink selection method and system for VDES multi-satellite coverage scenarios. This invention primarily utilizes pre-set shipboard context information and satellite ephemeris information in the core network. Upon receiving a downlink message, it queries a list of candidate satellites covering the target ship. For multi-satellite coverage scenarios, it initiates paging requests in parallel, collecting multi-dimensional parameters such as signal strength and signal-to-noise ratio returned by each satellite payload. Based on multiple factors such as signal strength, signal-to-noise ratio, location within the sector coverage area, satellite altitude, coverage stability, and queued message count, it executes a normalized satellite selection algorithm to calculate a comprehensive weighted score to select the optimal downlink. Finally, it sends VDE point-to-point messages to the target shipborne terminal through the selected optimal satellite payload. This achieves the technical effects of dynamically and intelligently selecting the optimal downlink satellite link in multi-satellite coverage scenarios, improving communication success rate and reliability, reducing transmission latency, and optimizing spectrum resource utilization.

[0009] The technical means employed in this invention are as follows: A downlink selection method for VDES multi-satellite coverage scenarios includes: The S1 and VDES satellite core network continuously collect static and dynamic information about ships from the VDES satellite payload, generate and cache shipboard context information, including the mapping relationship between the shipboard identifier MMSI and the latest position; at the same time, it obtains and pre-stores satellite ephemeris information from the satellite network operator. S2, VDES satellite core network receives VDE point-to-point messages that need to be sent to the target VDES shipborne terminal, and the messages carry the target ship identifier MMSI; S3. The VDES satellite core network queries the locally cached ship station context information based on the target ship identifier MMSI to obtain the real-time geographical location of the target ship station; based on the real-time geographical location and pre-stored ephemeris information, it calculates all VDES satellite payloads covering the target ship's location at the current time to obtain a candidate satellite list. S4. Determine the number of satellites in the candidate satellite list: If there is only one satellite, a paging message is sent directly to the target ship station through that satellite. After receiving the paging response, a point-to-point VDE message is sent through the same satellite. If there are multiple satellites, a paging request message carrying the target ship's MMSI is sent to the payload of each VDES satellite in the list in parallel. S5. Each VDES satellite payload that receives a paging request initiates a paging process on its own downlink; after receiving the paging message, the target VDES shipborne terminal sends a paging response message to the corresponding satellite payload; each satellite payload forwards the received paging response message and the signal strength and signal-to-noise ratio information measured when receiving the response message to the VDES satellite core network. The S6 and VDES satellite core networks collect all returned paging response messages and related information, read the signal strength and signal-to-noise ratio parameters of each satellite payload when receiving paging response messages, and simultaneously read the current message queue length of each satellite payload; based on the messages to be sent, they calculate the transmission time required. Query the ephemeris to obtain the real-time signal coverage area, satellite altitude, and other parameters of each VDES satellite payload. The signal coverage area after seconds; based on the above multi-dimensional parameters, the satellite selection algorithm is executed to calculate the comprehensive weighted score of each candidate satellite, and the VDES satellite payload with the highest score is selected as the optimal downlink; The S7 and VDES satellite core network send VDE point-to-point messages to the target VDES shipborne terminal through the selected optimal satellite payload.

[0010] Further, step S1 includes: S11, VDES shipborne terminal sends AIS static message, where the message ID of AIS static message is 5, 19 or 24; S12. When a ship is within the coverage area of ​​the VDES satellite network, each VDES satellite payload covering the area where the ship is located receives the AIS static message and reports it to the VDES satellite core network through the interface. S13, the VDES satellite core network parses and deduplicates AIS static messages received from multiple VDES satellite payloads to obtain ship static information including ship identifier MMSI and ship name; if the information of the shipborne terminal has not been saved locally, the shipborne terminal context information is newly generated and cached in the system. S14, the VDES shipborne terminal sends AIS dynamic messages, where the message ID of the AIS dynamic message is 1, 2, 3, 18 or 19. S15. When a ship is within the coverage area of ​​the VDES satellite network, each VDES satellite payload covering the area where the ship is located receives the AIS dynamic message and reports it to the VDES satellite core network through the interface. S16, the VDES satellite core network parses and deduplicates AIS dynamic messages received from multiple VDES satellite payloads, obtains ship dynamic information including ship position, heading and speed, updates shipborne terminal context information and caches it in the system; S17 and VDES satellite core networks obtain satellite ephemeris information from satellite network operators. The process for obtaining satellite ephemeris information is customized by each satellite network operator.

[0011] Further, step S2 includes: S21. Operators logged into the VDES business service platform send VDE point-to-point messages to the target vessel through the VDES business service platform, or external applications connected to the VDES business service platform send VDE point-to-point messages to the target vessel through the VDES business service platform. S22, VDE point-to-point messages carry the target vessel's MMSI and are forwarded by the VDES service platform to the VDES satellite core network; S23, the VDES satellite core network sends an acknowledgment message to the VDES service platform to confirm receipt of the point-to-point broadcast request.

[0012] Further, step S3 includes: S31, VDES satellite core network analyzes the destination MMSI carried in the received messages; The S32 and VDES satellite core networks query locally cached shipyard context information to obtain the current position of the target vessel. Based on the target ship's location and pre-stored ephemeris information, the S33 and VDES satellite core network calculate all VDES satellite payloads covering the target ship's location at the current moment. S34. Compile a candidate satellite list by combining all VDES satellite payloads that cover the target ship's location.

[0013] Further, step S4 includes: S41, VDES satellite core network determines the number of satellites in the candidate satellite list; S42. If there is only one satellite in the candidate satellite list, the VDES satellite core network will directly send a paging message to the target ship station through that satellite. S43. In the case of single-satellite coverage, upon receiving a paging response, immediately send a point-to-point VDE message through the same satellite; S44. If there are multiple satellites in the candidate satellite list, the VDES satellite core network will send a paging request to each VDES satellite payload in the candidate satellite list in sequence. The paging request message carries the destination ship MMSI.

[0014] Further, step S5 includes: S51. Each VDES satellite payload that receives a paging request shall initiate a ship paging procedure in accordance with the ITU-R M.2092 protocol definition. S52. After receiving the paging message from the satellite payload, the target VDES shipborne terminal sends a paging response message to the corresponding satellite payload. S53. After receiving the paging response, each VDES satellite payload generates association information associated with the paging response message based on the channel, time slot, signal strength, and signal-to-noise ratio information of the received response message. S54. Each VDES satellite payload sends the paging response message and associated information to the VDES satellite core network through a single message or two messages. The associated information includes the channel, time slot, signal strength, and signal-to-noise ratio parameters when receiving the paging response message.

[0015] Further, step S6 includes: The S61 and VDES satellite core networks receive messages returned by each satellite payload and extract signal strength and signal-to-noise ratio information from the messages. The S62 and VDES satellite core networks read the signal strength of each satellite payload when receiving paging response messages. And perform normalization:

[0016] in, ; ; The signal-to-noise ratio of each satellite payload receiving paging response messages is read by the S63 and VDES satellite core network. And perform normalization:

[0017] in, ; ; The S64 and VDES satellite core networks read the current message queue length for each satellite payload. And perform normalization:

[0018] in, ; ; The S65 and VDES satellite core network queries the current ephemeris to obtain the real-time signal coverage area and satellite altitude of the VDES satellite payload. And perform normalization:

[0019] in, ; ; The S66 and VDES satellite core networks calculate the time required to send a message based on the message to be sent. VDES satellite core network query to obtain current ephemeris The VDES satellite payload signal coverage area was obtained seconds later. Will the ship be covered in seconds? And perform normalization:

[0020] The S67 and VDES satellite core networks calculate the distance of the target ship from the great circle radius. Distance from the radius of the small circle The radial positions of the sector are obtained and then normalized.

[0021] The S68 and VDES satellite core networks calculate the distance of the target ship from the left sector. Distance from the right fan edge The horizontal position of the sector is obtained and then normalized.

[0022] The S69 and VDES satellite core networks combine the radial and lateral positions of the sector into a position score, using the following formula:

[0023] S610 and VDES satellite core networks are based on normalized signal strength. Signal-to-noise ratio Location rating Satellite altitude Coverage stability Queued message length Calculate the overall weighted score for each candidate satellite:

[0024] in, Indicates signal strength weights. Indicates the signal-to-noise ratio weight. Indicates the position weight within the sector. Indicates satellite altitude weight. Indicates the coverage stability weight. Indicates the weight of the queued message length; S611, Select Comprehensive Weighted Score The largest VDES satellite payload is used as the optimal satellite link for transmitting downlink messages; S612, If the comprehensive weighted score is used If the maximum value is less than the preset threshold, the current round of transmission is abandoned, and the satellite is reselected after the next paging.

[0025] Further, step S7 includes: S71, the VDES satellite core network sends a VDE service message transmission request to the selected optimal satellite payload, wherein the request message carries attributes related to the transmission of the service message; S72. The optimal satellite payload determines whether to use short messages or fragment messages based on the aforementioned attributes, wherein the message ID of short messages is 14 and the message ID of fragment messages is 30 to 32. S73. The optimal satellite payload selects the corresponding message ID based on the VDE service message sending request and sends the VDE service message. S74. After the optimal satellite payload confirms the successful transmission of the VDE service message, a broadcast success message is sent to the VDES satellite core network. After receiving the broadcast success message, the S75 and VDES satellite core network send a VDE service message broadcast success message to the VDES service platform to notify the VDES service platform that the VDE service message broadcast was successful.

[0026] This invention also provides a downlink selection system for VDES multi-satellite coverage scenarios, comprising: The VDES service platform is used to initiate or receive service data for the VDES shipborne terminal. The VDES satellite core network, connected to the VDES service platform, is used to store shipboard context information and ephemeris information, and to perform link selection decisions. The VDES satellite payload is connected to the VDES satellite core network and is used to forward messages between the core network and the shipborne terminal, and to report the signal strength and signal-to-noise ratio information of the transmitted and received messages. The VDES shipborne terminal is used to receive and send AIS, ASM, and VDE messages. The VDES satellite core network is configured to execute the downlink selection method in the VDES multi-satellite coverage scenario, specifically including: The platform context information generation and ephemeris information pre-setting module is used to continuously collect static and dynamic information of the ship, generate and cache platform context information including the mapping relationship between the platform identifier MMSI and the latest position, and obtain pre-stored satellite ephemeris information from the satellite network operator. The downlink message receiving module is used to receive VDE point-to-point messages carrying the target vessel identifier MMSI from the VDES service platform or another shipborne terminal. The candidate satellite list query module is used to query the local cached ship station context information based on the target ship identifier MMSI to obtain the real-time geographical location of the target ship station, and calculate all VDES satellite payloads covering the target ship's location at the current time based on the real-time geographical location and pre-stored ephemeris information to obtain the candidate satellite list. The multi-satellite coverage judgment and paging control module is used to judge the number of satellites in the candidate satellite list. When there is single-satellite coverage, it directly sends a paging message through the satellite. When there is multi-satellite coverage, it sends a paging request message carrying the target ship station MMSI to each VDES satellite payload in the list in parallel. The signal quality collection module is used to collect paging response messages returned by each satellite payload and signal strength and signal-to-noise ratio information measured based on the received response messages; The optimal link selection module is used to read the signal strength, signal-to-noise ratio parameters, and message queue length of each satellite payload, and calculate the transmission time required based on the messages to be transmitted. Query the ephemeris to obtain the real-time signal coverage area, satellite altitude, and other parameters of each VDES satellite payload. The signal coverage area after seconds is calculated using a satellite selection algorithm based on multi-parameter parameters to obtain a comprehensive weighted score, and the VDES satellite payload with the highest score is selected as the optimal downlink. The downlink message sending module is used to send VDE point-to-point messages to the target VDES shipborne terminal via the selected optimal satellite payload.

[0027] Compared with the prior art, the present invention has the following advantages: 1. The present invention provides a downlink selection method in a VDES multi-satellite coverage scenario. By initiating paging in parallel with multiple coverage satellites and collecting multi-dimensional parameters such as signal strength and signal-to-noise ratio of each satellite link, the method realizes dynamic and intelligent selection of the optimal downlink in a multi-satellite coverage scenario, thereby significantly improving the communication success rate and reliability, and reducing the packet loss rate and retransmission rate caused by selecting inferior links.

[0028] 2. The present invention provides a downlink selection method in a VDES multi-satellite coverage scenario. By using a comprehensive weighted scoring algorithm based on multiple factors such as signal strength, signal-to-noise ratio, location within the sector coverage area, satellite altitude, coverage stability, and number of queued messages, the method achieves quantitative evaluation and selection of candidate satellite links. This ensures that downlink messages are always transmitted through the link with the best performance, effectively avoiding communication quality fluctuations caused by random or fixed satellite selection.

[0029] 3. The present invention provides a downlink selection method in a VDES multi-satellite coverage scenario. By calculating the transmission time x based on the length of the message to be sent and predicting whether the satellite will still cover the target ship after x seconds, the method achieves a forward-looking assessment of the continuous stability of the link, thereby ensuring the complete transmission of VDE point-to-point messages and avoiding message transmission interruption caused by the satellite moving out of the coverage area.

[0030] 4. The downlink selection method in a VDES multi-satellite coverage scenario provided by this invention introduces the length of the satellite message queue to be sent as one of the satellite selection parameters, thereby taking into account the satellite payload load status, and thus prioritizing the selection of satellites with shorter queues, avoiding increased transmission delays caused by satellite overload, and optimizing the overall spectrum resource utilization efficiency of the system.

[0031] 5. The downlink selection method for VDES multi-satellite coverage scenarios provided by this invention achieves decoupling of paging coverage discovery and optimal link selection by adopting a two-stage process of parallel paging followed by optimal transmission. This ensures that all possible covered satellites can be found, and also ensures that the performance of the final transmission link is optimal, thus forming a complete fallback mechanism.

[0032] In summary, by applying the technical solution of this invention, the problems of inflexible fixed satellite selection, unreliable communication quality due to random satellite selection, and failure to fully utilize the differences in signal quality among multiple satellites based solely on coverage are addressed. This invention achieves dynamic and intelligent selection of the optimal downlink in multi-satellite coverage scenarios through multi-parameter parallel paging and a comprehensive weighted satellite selection algorithm. Therefore, the technical solution of this invention solves the technical problems of poor communication quality, low success rate, large transmission delay, and insufficient utilization of spectrum resources in multi-satellite coverage scenarios, which are caused by the inability to dynamically and intelligently select the optimal downlink satellite link.

[0033] Based on the above reasons, this invention can be widely applied in fields such as VDES satellite communication, marine communication, low-orbit satellite constellation communication, and maritime Internet of Things communication. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is the core flowchart of the downlink selection method of the present invention.

[0036] Figure 2 This is a schematic diagram of the process for generating shipboard context information according to the present invention.

[0037] Figure 3 This is a system architecture diagram of downlink selection based on signal quality in a VDES multi-satellite coverage scenario according to the present invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. 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 should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product or device.

[0040] like Figure 1 As shown, this invention provides a downlink selection method in a VDES multi-satellite coverage scenario, comprising: The S1 and VDES satellite core network continuously collect static and dynamic information about ships from the VDES satellite payload, generate and cache shipboard context information, including the mapping relationship between the shipboard identifier MMSI and the latest position; at the same time, it obtains and pre-stores satellite ephemeris information from the satellite network operator. S2, VDES satellite core network receives VDE point-to-point messages that need to be sent to the target VDES shipborne terminal, and the messages carry the target ship identifier MMSI; S3. The VDES satellite core network queries the locally cached ship station context information based on the target ship identifier MMSI to obtain the real-time geographical location of the target ship station; based on the real-time geographical location and pre-stored ephemeris information, it calculates all VDES satellite payloads covering the target ship's location at the current time to obtain a candidate satellite list. S4. Determine the number of satellites in the candidate satellite list: If there is only one satellite, a paging message is sent directly to the target ship station through that satellite. After receiving the paging response, a point-to-point VDE message is sent through the same satellite. If there are multiple satellites, a paging request message carrying the target ship's MMSI is sent to the payload of each VDES satellite in the list in parallel. S5. Each VDES satellite payload that receives a paging request initiates a paging process on its own downlink; after receiving the paging message, the target VDES shipborne terminal sends a paging response message to the corresponding satellite payload; each satellite payload forwards the received paging response message and the signal strength and signal-to-noise ratio information measured when receiving the response message to the VDES satellite core network. The S6 and VDES satellite core networks collect all returned paging response messages and related information, read the signal strength and signal-to-noise ratio parameters of each satellite payload when receiving paging response messages, and simultaneously read the current message queue length of each satellite payload; based on the messages to be sent, they calculate the transmission time required. Query the ephemeris to obtain the real-time signal coverage area, satellite altitude, and other parameters of each VDES satellite payload. The signal coverage area after seconds; based on the above multi-dimensional parameters, the satellite selection algorithm is executed to calculate the comprehensive weighted score of each candidate satellite, and the VDES satellite payload with the highest score is selected as the optimal downlink; The S7 and VDES satellite core network send VDE point-to-point messages to the target VDES shipborne terminal through the selected optimal satellite payload.

[0041] In specific implementation, as a preferred embodiment of the present invention, such as Figure 2 As shown, step S1 includes: S11, VDES shipborne terminal sends AIS static message, where the message ID of AIS static message is 5, 19 or 24; S12. When a ship is within the coverage area of ​​the VDES satellite network, each VDES satellite payload covering the area where the ship is located receives the AIS static message and reports it to the VDES satellite core network through the interface. S13, the VDES satellite core network parses and deduplicates AIS static messages received from multiple VDES satellite payloads to obtain ship static information including ship identifier MMSI and ship name; if the information of the shipborne terminal has not been saved locally, the shipborne terminal context information is newly generated and cached in the system. S14, the VDES shipborne terminal sends AIS dynamic messages, where the message ID of the AIS dynamic message is 1, 2, 3, 18 or 19. S15. When a ship is within the coverage area of ​​the VDES satellite network, each VDES satellite payload covering the area where the ship is located receives the AIS dynamic message and reports it to the VDES satellite core network through the interface. S16, the VDES satellite core network parses and deduplicates AIS dynamic messages received from multiple VDES satellite payloads, obtains ship dynamic information including ship position, heading and speed, updates shipborne terminal context information and caches it in the system; S17. The VDES satellite core network obtains satellite ephemeris information from the satellite network operator. The process for obtaining satellite ephemeris information is customized by each satellite network operator and there is no unified process. The specific interaction process is based on the operator's definition and will not be described in detail in this patent. In a specific implementation, as a preferred embodiment of the present invention, step S2 includes: S21. Operators logged into the VDES business service platform send VDE point-to-point messages to the target vessel through the VDES business service platform, or external applications connected to the VDES business service platform send VDE point-to-point messages to the target vessel through the VDES business service platform. S22, VDE point-to-point messages carry the target vessel's MMSI and are forwarded by the VDES service platform to the VDES satellite core network; S23, the VDES satellite core network sends an acknowledgment message to the VDES service platform to confirm receipt of the point-to-point broadcast request.

[0042] In a specific implementation, as a preferred embodiment of the present invention, step S3 includes: S31, VDES satellite core network analyzes the destination MMSI carried in the received messages; The S32 and VDES satellite core networks query locally cached shipyard context information to obtain the current position of the target vessel. Based on the target ship's location and pre-stored ephemeris information, the S33 and VDES satellite core network calculate all VDES satellite payloads covering the target ship's location at the current moment. S34. Compile a candidate satellite list by combining all VDES satellite payloads that cover the target ship's location.

[0043] In a specific implementation, as a preferred embodiment of the present invention, step S4 includes: S41, VDES satellite core network determines the number of satellites in the candidate satellite list; S42. If there is only one satellite in the candidate satellite list, the VDES satellite core network will directly send a paging message to the target ship station through that satellite. S43. In the case of single-satellite coverage, upon receiving a paging response, immediately send a point-to-point VDE message through the same satellite; S44. If there are multiple satellites in the candidate satellite list, the VDES satellite core network will send a paging request to each VDES satellite payload in the candidate satellite list in sequence. The paging request message carries the destination ship MMSI.

[0044] In a specific implementation, as a preferred embodiment of the present invention, step S5 includes: S51. Each VDES satellite payload that receives a paging request shall initiate a ship paging procedure in accordance with the ITU-R M.2092 protocol definition. S52. After receiving the paging message from the satellite payload, the target VDES shipborne terminal sends a paging response message to the corresponding satellite payload. S53. After receiving the paging response, each VDES satellite payload generates association information associated with the paging response message based on the channel, time slot, signal strength, and signal-to-noise ratio information of the received response message. S54. Each VDES satellite payload sends the paging response message and associated information to the VDES satellite core network through a single message or two messages. The associated information includes the channel, time slot, signal strength, and signal-to-noise ratio parameters when receiving the paging response message.

[0045] In a specific implementation, as a preferred embodiment of the present invention, step S6 includes: The S61 and VDES satellite core networks receive messages returned by each satellite payload and extract signal strength and signal-to-noise ratio information from the messages. The S62 and VDES satellite core networks read the signal strength of each satellite payload when receiving paging response messages. And perform normalization:

[0046] in, ; ; The signal-to-noise ratio of each satellite payload receiving paging response messages is read by the S63 and VDES satellite core network. And perform normalization:

[0047] in, ; ; The S64 and VDES satellite core networks read the current message queue length for each satellite payload. And perform normalization:

[0048] in, ; ; The S65 and VDES satellite core network queries the current ephemeris to obtain the real-time signal coverage area and satellite altitude of the VDES satellite payload. And perform normalization:

[0049] in, ; ; The S66 and VDES satellite core networks calculate the time required to send a message based on the message to be sent. VDES satellite core network query to obtain current ephemeris The VDES satellite payload signal coverage area was obtained seconds later. Will the ship be covered in seconds? And perform normalization:

[0050] The S67 and VDES satellite core networks calculate the distance of the target ship from the great circle radius. Distance from the radius of the small circle The radial positions of the sector are obtained and then normalized.

[0051] The S68 and VDES satellite core networks calculate the distance of the target ship from the left sector. Distance from the right fan edge The horizontal position of the sector is obtained and then normalized.

[0052] The S69 and VDES satellite core networks combine the radial and lateral positions of the sector into a position score, using the following formula:

[0053] S610 and VDES satellite core networks are based on normalized signal strength. Signal-to-noise ratio Location rating Satellite altitude Coverage stability Queued message length Calculate the overall weighted score for each candidate satellite:

[0054] in, Indicates signal strength weights. Indicates the signal-to-noise ratio weight. Indicates the position weight within the sector. Indicates satellite altitude weight. Indicates the coverage stability weight. This represents the weight of the queued message length; examples of weights are shown in the table below:

[0055] Note: The above weight allocation is for example only. The weights of each parameter can be adjusted according to the actual situation during implementation.

[0056] S611, Select Comprehensive Weighted Score The largest VDES satellite payload is used as the optimal satellite link for transmitting downlink messages; S612, If the comprehensive weighted score is used If the maximum value is less than the preset threshold, the current round of transmission is abandoned, and the satellite is reselected after the next paging.

[0057] In this embodiment, the VDES satellite core network executes a satellite selection algorithm, and the parameters involved in the satellite selection are shown in the table below:

[0058] Note: The signal coverage area of ​​the VDES satellite payload on the ground is approximately a sector, where the left and right sides of the sector are defined as two sides, and the top and bottom sides of the sector are two concentric circles, where the circle corresponding to the upper longer side is defined as the large circle, and the circle corresponding to the lower shorter side is defined as the small circle.

[0059] Note: The satellite selection process of this invention is applicable to any network connecting VDES satellite payloads, including but not limited to the VDES satellite core network.

[0060] In a specific implementation, as a preferred embodiment of the present invention, step S7 includes: S71, the VDES satellite core network sends a VDE service message transmission request to the selected optimal satellite payload, wherein the request message carries attributes related to the transmission of the service message; S72. The optimal satellite payload determines whether to use short messages or fragment messages based on the aforementioned attributes, wherein the message ID of short messages is 14 and the message ID of fragment messages is 30 to 32. S73. The optimal satellite payload selects the corresponding message ID based on the VDE service message sending request and sends the VDE service message. S74. After the optimal satellite payload confirms the successful transmission of the VDE service message, a broadcast success message is sent to the VDES satellite core network. After receiving the broadcast success message, the S75 and VDES satellite core network send a VDE service message broadcast success message to the VDES service platform to notify the VDES service platform that the VDE service message broadcast was successful.

[0061] The downlink selection method based on signal quality in the multi-satellite coverage scenario involved in this invention is mainly used by the VDES service platform (or other application systems) to send point-to-point messages to target ships that are not in the service area of ​​shore-based base stations, and for ship-to-ship point-to-point communication where the target ship is not in the service area of ​​shore-based base stations. The downlink selection process is exactly the same in both scenarios.

[0062] This invention also provides a downlink selection system for VDES multi-satellite coverage scenarios, such as... Figure 3 As shown, it includes: The VDES service platform is used to initiate or receive service data for the VDES shipborne terminal. The VDES satellite core network, connected to the VDES service platform, is used to store shipboard context information and ephemeris information, and to perform link selection decisions. The VDES satellite payload is connected to the VDES satellite core network and is used to forward messages between the core network and the shipborne terminal, and to report the signal strength and signal-to-noise ratio information of the transmitted and received messages. The VDES shipborne terminal is used to receive and send AIS, ASM, and VDE messages. The VDES satellite core network is configured to execute the aforementioned downlink selection method, specifically including: The platform context information generation and ephemeris information pre-setting module is used to continuously collect static and dynamic information of the ship, generate and cache platform context information including the mapping relationship between the platform identifier MMSI and the latest position, and obtain pre-stored satellite ephemeris information from the satellite network operator. The downlink message receiving module is used to receive VDE point-to-point messages carrying the target vessel identifier MMSI from the VDES service platform or another shipborne terminal. The candidate satellite list query module is used to query the local cached ship station context information based on the target ship identifier MMSI to obtain the real-time geographical location of the target ship station, and calculate all VDES satellite payloads covering the target ship's location at the current time based on the real-time geographical location and pre-stored ephemeris information to obtain the candidate satellite list. The multi-satellite coverage judgment and paging control module is used to judge the number of satellites in the candidate satellite list. When there is single-satellite coverage, it directly sends a paging message through the satellite. When there is multi-satellite coverage, it sends a paging request message carrying the target ship station MMSI to each VDES satellite payload in the list in parallel. The signal quality collection module is used to collect paging response messages returned by each satellite payload and signal strength and signal-to-noise ratio information measured based on the received response messages; The optimal link selection module is used to read the signal strength, signal-to-noise ratio parameters, and message queue length of each satellite payload, and calculate the transmission time required based on the messages to be transmitted. Query the ephemeris to obtain the real-time signal coverage area, satellite altitude, and other parameters of each VDES satellite payload. The signal coverage area after seconds is calculated using a satellite selection algorithm based on multi-parameter parameters to obtain a comprehensive weighted score, and the VDES satellite payload with the highest score is selected as the optimal downlink. The downlink message sending module is used to send VDE point-to-point messages to the target VDES shipborne terminal via the selected optimal satellite payload.

[0063] The embodiments of the present invention are described simply because they correspond to those in the embodiments above. For any similarities, please refer to the descriptions in the embodiments above, which will not be elaborated here.

[0064] 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A downlink selection method in a VDES multi-satellite coverage scenario, characterized in that, include: The S1 and VDES satellite core network continuously collect static and dynamic information about ships from the VDES satellite payload, generate and cache shipboard context information, including the mapping relationship between the shipboard identifier MMSI and the latest position; at the same time, it obtains and pre-stores satellite ephemeris information from the satellite network operator. S2, VDES satellite core network receives VDE point-to-point messages that need to be sent to the target VDES shipborne terminal, and the messages carry the target ship identifier MMSI; S3, the VDES satellite core network queries the locally cached ship station context information based on the target ship identifier MMSI to obtain the real-time geographical location of the target ship station; Based on real-time geographic location and pre-stored ephemeris information, calculate all VDES satellite payloads covering the target ship's location at the current moment to obtain a candidate satellite list; S4. Determine the number of satellites in the candidate satellite list: If there is only one satellite, a paging message is sent directly to the target ship station through that satellite. After receiving the paging response, a point-to-point VDE message is sent through the same satellite. If there are multiple satellites, a paging request message carrying the target ship's MMSI is sent to the payload of each VDES satellite in the list in parallel. S5. Each VDES satellite payload that receives a paging request initiates a paging process on its own downlink. After receiving the paging message, the target VDES shipborne terminal sends a paging response message to the corresponding satellite payload. Each satellite payload will forward the received paging response messages, as well as the signal strength and signal-to-noise ratio information measured when receiving the response messages, to the VDES satellite core network; The S6 and VDES satellite core networks collect all returned paging response messages and related information, read the signal strength and signal-to-noise ratio parameters of each satellite payload when receiving paging response messages, and read the current message queue length of each satellite payload. Calculate the required transmission time based on the message to be sent. Query the ephemeris to obtain the real-time signal coverage area, satellite altitude, and other parameters of each VDES satellite payload. The signal coverage area after seconds; based on the above multi-dimensional parameters, the satellite selection algorithm is executed to calculate the comprehensive weighted score of each candidate satellite, and the VDES satellite payload with the highest score is selected as the optimal downlink; The S7 and VDES satellite core network send VDE point-to-point messages to the target VDES shipborne terminal through the selected optimal satellite payload.

2. The downlink selection method in a VDES multi-satellite coverage scenario according to claim 1, characterized in that, Step S1 includes: S11, VDES shipborne terminal sends AIS static message, where the message ID of AIS static message is 5, 19 or 24; S12. When a ship is within the coverage area of ​​the VDES satellite network, each VDES satellite payload covering the area where the ship is located receives the AIS static message and reports it to the VDES satellite core network through the interface. S13, the VDES satellite core network parses and deduplicates AIS static messages received from multiple VDES satellite payloads to obtain ship static information including ship identifier MMSI and ship name; if the information of the shipborne terminal has not been saved locally, the shipborne terminal context information is newly generated and cached in the system. S14, the VDES shipborne terminal sends AIS dynamic messages, where the message ID of the AIS dynamic message is 1, 2, 3, 18 or 19. S15. When a ship is within the coverage area of ​​the VDES satellite network, each VDES satellite payload covering the area where the ship is located receives the AIS dynamic message and reports it to the VDES satellite core network through the interface. S16, the VDES satellite core network parses and deduplicates AIS dynamic messages received from multiple VDES satellite payloads, obtains ship dynamic information including ship position, heading and speed, updates shipborne terminal context information and caches it in the system; S17 and VDES satellite core networks obtain satellite ephemeris information from satellite network operators. The process for obtaining satellite ephemeris information is customized by each satellite network operator.

3. The downlink selection method in a VDES multi-satellite coverage scenario according to claim 1, characterized in that, Step S2 includes: S21. Operators logged into the VDES business service platform send VDE point-to-point messages to the target vessel through the VDES business service platform, or external applications connected to the VDES business service platform send VDE point-to-point messages to the target vessel through the VDES business service platform. S22, VDE point-to-point messages carry the target vessel's MMSI and are forwarded by the VDES service platform to the VDES satellite core network; S23, the VDES satellite core network sends an acknowledgment message to the VDES service platform to confirm receipt of the point-to-point broadcast request.

4. The downlink selection method in a VDES multi-satellite coverage scenario according to claim 1, characterized in that, Step S3 includes: S31, VDES satellite core network analyzes the destination MMSI carried in the received messages; The S32 and VDES satellite core networks query locally cached shipyard context information to obtain the current position of the target vessel. Based on the target ship's location and pre-stored ephemeris information, the S33 and VDES satellite core network calculate all VDES satellite payloads covering the target ship's location at the current moment. S34. Compile a candidate satellite list by combining all VDES satellite payloads that cover the target ship's location.

5. The downlink selection method in a VDES multi-satellite coverage scenario according to claim 1, characterized in that, Step S4 includes: S41, VDES satellite core network determines the number of satellites in the candidate satellite list; S42. If there is only one satellite in the candidate satellite list, the VDES satellite core network will directly send a paging message to the target ship station through that satellite. S43. In the case of single-satellite coverage, upon receiving a paging response, immediately send a point-to-point VDE message through the same satellite; S44. If there are multiple satellites in the candidate satellite list, the VDES satellite core network will send a paging request to each VDES satellite payload in the candidate satellite list in sequence. The paging request message carries the destination ship MMSI.

6. The downlink selection method in a VDES multi-satellite coverage scenario according to claim 1, characterized in that, Step S5 includes: S51. Each VDES satellite payload that receives a paging request shall initiate a ship paging procedure in accordance with the ITU-R M.2092 protocol definition. S52. After receiving the paging message from the satellite payload, the target VDES shipborne terminal sends a paging response message to the corresponding satellite payload. S53. After receiving the paging response, each VDES satellite payload generates association information associated with the paging response message based on the channel, time slot, signal strength, and signal-to-noise ratio information of the received response message. S54. Each VDES satellite payload sends the paging response message and associated information to the VDES satellite core network through a single message or two messages. The associated information includes the channel, time slot, signal strength, and signal-to-noise ratio parameters when receiving the paging response message.

7. The downlink selection method in a VDES multi-satellite coverage scenario according to claim 1, characterized in that, Step S6 includes: The S61 and VDES satellite core networks receive messages returned by each satellite payload and extract signal strength and signal-to-noise ratio information from the messages. The S62 and VDES satellite core networks read the signal strength of each satellite payload when receiving paging response messages. And perform normalization: in, ; ; The signal-to-noise ratio of each satellite payload receiving paging response messages is read by the S63 and VDES satellite core network. And perform normalization: in, ; ; The S64 and VDES satellite core networks read the current message queue length for each satellite payload. And perform normalization: in, ; ; The S65 and VDES satellite core network queries the current ephemeris to obtain the real-time signal coverage area and satellite altitude of the VDES satellite payload. And perform normalization: in, ; ; The S66 and VDES satellite core networks calculate the time required to send a message based on the message to be sent. VDES satellite core network query to obtain current ephemeris The VDES satellite payload signal coverage area was obtained seconds later. Will the ship be covered in seconds? And perform normalization: The S67 and VDES satellite core networks calculate the distance of the target ship from the great circle radius. Distance from the radius of the small circle The radial positions of the sector are obtained and then normalized. The S68 and VDES satellite core networks calculate the distance of the target ship from the left sector. Distance from the right fan edge The horizontal position of the sector is obtained and then normalized. The S69 and VDES satellite core networks combine the radial and lateral positions of the sector into a position score, using the following formula: S610 and VDES satellite core networks are based on normalized signal strength. Signal-to-noise ratio Location rating Satellite altitude Coverage stability Queued message length Calculate the overall weighted score for each candidate satellite: in, Indicates signal strength weights. Indicates the signal-to-noise ratio weight. Indicates the position weight within the sector. Indicates satellite altitude weight. Indicates the coverage stability weight. Indicates the weight of the queued message length; S611, Select Comprehensive Weighted Score The largest VDES satellite payload is used as the optimal satellite link for transmitting downlink messages; S612, If the comprehensive weighted score If the maximum value is less than the preset threshold, the current round of transmission is abandoned, and the satellite is reselected after the next paging.

8. The downlink selection method in a VDES multi-satellite coverage scenario according to claim 1, characterized in that, Step S7 includes: S71, the VDES satellite core network sends a VDE service message transmission request to the selected optimal satellite payload, wherein the request message carries attributes related to the transmission of the service message; S72. The optimal satellite payload determines whether to use short messages or fragment messages based on the aforementioned attributes, wherein the message ID of short messages is 14 and the message ID of fragment messages is 30 to 32. S73. The optimal satellite payload selects the corresponding message ID based on the VDE service message sending request and sends the VDE service message. S74. After the optimal satellite payload confirms the successful transmission of the VDE service message, a broadcast success message is sent to the VDES satellite core network. After receiving the broadcast success message, the S75 and VDES satellite core network send a VDE service message broadcast success message to the VDES service platform to notify the VDES service platform that the VDE service message broadcast was successful.

9. A downlink selection system for VDES multi-satellite coverage scenarios, characterized in that, include: VD The ES business service platform is used to initiate or receive business data for the VDES shipborne terminal. The VDES satellite core network, connected to the VDES service platform, is used to store shipboard context information and ephemeris information, and to perform link selection decisions. The VDES satellite payload is connected to the VDES satellite core network and is used to forward messages between the core network and the shipborne terminal, and to report the signal strength and signal-to-noise ratio information of the transmitted and received messages. The VDES shipborne terminal is used to receive and send AIS, ASM, and VDE messages. The VDES satellite core network is configured to perform the method described in any one of claims 1 to 9, specifically including: The platform context information generation and ephemeris information pre-setting module is used to continuously collect static and dynamic information of the ship, generate and cache platform context information including the mapping relationship between the platform identifier MMSI and the latest position, and obtain pre-stored satellite ephemeris information from the satellite network operator. The downlink message receiving module is used to receive VDE point-to-point messages carrying the target vessel identifier MMSI from the VDES service platform or another shipborne terminal. The candidate satellite list query module is used to query the local cached ship station context information based on the target ship identifier MMSI to obtain the real-time geographical location of the target ship station, and calculate all VDES satellite payloads covering the target ship's location at the current time based on the real-time geographical location and pre-stored ephemeris information to obtain the candidate satellite list. The multi-satellite coverage judgment and paging control module is used to judge the number of satellites in the candidate satellite list. When there is single-satellite coverage, it directly sends a paging message through the satellite. When there is multi-satellite coverage, it sends a paging request message carrying the target ship station MMSI to each VDES satellite payload in the list in parallel. The signal quality collection module is used to collect paging response messages returned by each satellite payload and signal strength and signal-to-noise ratio information measured based on the received response messages; The optimal link selection module is used to read the signal strength, signal-to-noise ratio parameters, and message queue length of each satellite payload, and calculate the transmission time required based on the messages to be transmitted. Query the ephemeris to obtain the real-time signal coverage area, satellite altitude, and other parameters of each VDES satellite payload. The signal coverage area after seconds is calculated using a satellite selection algorithm based on multi-parameter parameters, and the VDES satellite payload with the highest score is selected as the optimal downlink. The downlink message sending module is used to send VDE point-to-point messages to the target VDES shipborne terminal via the selected optimal satellite payload.

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