A method and system for optimizing traffic of ship-shore offline data transmission under a restricted network

Abstract

The present application relates to a kind of flow optimization method and system for ship-shore offline data transmission under restricted network, the system first real-time acquisition ship end including the multi-source data of safety alarm data, collision avoidance trajectory data and sensor data, and carry out differentiated preprocessing to generate lightweight data set, then real-time compression processing is carried out;Then construct the priority layered model including multi-stage queue scheduling mechanism, transmission scheduling is implemented according to safety level, and flow quota monitoring and fuse protection are carried out, and network state is monitored in real time, when network state is abnormal, suspend the data transmission of all queues, and record the transmission breakpoint state of each queue and the data packet sequence number of uncompleted transmission when abnormal occurs, finally, after network state recovers, based on the transmission breakpoint state of each queue and the offline data packet sequence number of uncompleted transmission recorded, data is continued according to priority order, and the data integrity is verified using hash check method, complete the flow optimization of ship-shore offline data transmission.

Description

Technical Field

[0001] This invention relates to the field of ship communication technology, specifically to a method and system for optimizing the flow of ship-to-shore offline data transmission under limited network conditions. Background Technology

[0002] When ships navigate in the marine environment, they are affected by weather conditions, environmental factors, and the coverage of base stations, and rely primarily on satellite communication for long-distance communication. However, due to the limited bandwidth and inherent high latency of satellite communication networks, data transmission speeds are low and response times are long. This not only affects data transmission efficiency but also poses potential safety hazards to critical operations requiring real-time information updates (such as viewing electronic charts, radar equipment data, and sending telegrams).

[0003] Satellite communication services are typically billed based on data traffic, meaning that excessive network communication can directly increase communication costs, becoming a significant economic burden for shipping companies. Furthermore, if the satellite communication network used by a ship has limited bandwidth, excessive data transmission can cause network congestion, affecting not only the user experience of other users but also the normal operation of other onboard equipment, such as viewing electronic charts and radar equipment, and sending telegrams, posing safety hazards to navigation. Therefore, effectively managing data traffic, reducing communication costs, and ensuring the reliability and stability of critical communications are of paramount importance during ship navigation.

[0004] Existing technologies typically rely on transmitting unprocessed or simply compressed data directly via satellite links. This approach fails to adequately consider bandwidth utilization and cost control. Specifically: high-frequency sensor data collected on board (such as LiDAR point clouds and GPS positioning information) is generated at the raw frame rate. Continuous trajectory sampling and environmental monitoring values ​​contain a large amount of repetitive or unnecessary information, consuming valuable and limited bandwidth resources when transmitted directly; general compression methods are used for ship data (such as collision avoidance trajectory vectors and equipment status logs), resulting in a still large compressed file size, thus failing to minimize data volume; transmitting various types of data, such as ship safety alarms and routine operation logs, in a uniform order can easily cause delays in the transmission of critical information; the transmission volume changes directly with the amount of data generated during data transmission, potentially leading to excessive daily data transmission, resulting in high costs due to overuse of satellite communication, increasing the risk of network congestion, and affecting the normal user experience of other users.

[0005] These issues make it difficult for ships to effectively manage traffic usage, reduce communication costs, and ensure the reliability and stability of critical communications during navigation. Therefore, optimizing ship-to-shore offline data transmission methods to improve data transmission efficiency, reduce costs, and ensure the reliability of critical communications in constrained network environments is a pressing problem that needs to be solved. Summary of the Invention

[0006] To address the problems existing in current ship-to-shore offline message transmission, such as the lack of effective local data processing, delays in critical information transmission due to uniform transmission order, network congestion, and insufficient data compression, this invention provides a traffic optimization method for ship-to-shore offline data transmission under constrained network conditions. This method significantly reduces the amount of data to be transmitted to the shore, reduces bandwidth consumption, optimizes bandwidth utilization, and achieves minimum bandwidth transmission of ship-side data (sensor data, alarm information, event logs, etc.) to the shore even in unstable or weak network environments. This invention also relates to a traffic optimization system for ship-to-shore offline data transmission under constrained network conditions.

[0007] The technical solution of the present invention is as follows:

[0008] A method for optimizing the traffic of ship-to-shore offline data transmission under a restricted network, characterized by comprising the following steps:

[0009] Data acquisition and lightweight processing steps: Real-time acquisition of multi-source data from the ship, including safety alarm data, collision avoidance trajectory data, and sensor data; Differentiated preprocessing of the acquired multi-source data at the ship, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into single-batch vector packets, and standardized encoding processing of safety alarm data; After the above differentiated preprocessing, a lightweight dataset adapted for ship-shore offline data transmission is generated.

[0010] Data compression processing steps: The ZLIB compression engine is used to compress the lightweight dataset after differential preprocessing in real time;

[0011] Data transmission scheduling steps: Construct a priority-layered model based on security levels, including a multi-level queue scheduling mechanism, and implement transmission scheduling according to security levels; the multi-level queues include a first-level queue, a second-level queue, and a third-level queue. The first-level queue stores security alarm data from the compressed lightweight dataset and sets it to the highest priority for real-time preemptive transmission; the second-level queue stores collision avoidance trajectory data from the compressed lightweight dataset and sets it to a medium priority for timely aggregation transmission; the third-level queue stores sensor data from the compressed lightweight dataset and sets it to the lowest priority for transmission at the minimum rate when there is bandwidth redundancy.

[0012] Traffic quota monitoring and circuit breaker steps: Real-time statistics of the daily cumulative data transmission traffic of all queues from ship to shore, and compare the cumulative data transmission traffic with the preset daily traffic threshold. If the daily cumulative data transmission traffic reaches the daily traffic threshold, activate circuit breaker protection and stop all queues from transmitting data for the day.

[0013] Network monitoring and breakpoint recording steps: Monitor the network status in real time. When an abnormal network status is detected, suspend data transmission of all queues from the ship to the shore and record the breakpoint status of each queue at the time of the abnormality. Then, assign a unique sequence number to each data packet to be transmitted in each queue, treat the data packets that have not been transmitted as offline data packets, and record the offline data packet sequence number in the database.

[0014] Resumption of transmission and integrity verification steps: When network status recovery is detected, based on the recorded transmission interruption status of each queue and the sequence number of offline data packets that have not been transmitted, the offline data packets that have not been transmitted are resumed in order of priority of each queue. The integrity of the resumed offline data packets is verified by a hash verification method. Offline data packets that fail the verification are re-entered into the corresponding priority queue for transmission. After all data packets are verified successfully, the traffic optimization of ship-shore offline data transmission under the restricted network is completed.

[0015] Preferably, in the breakpoint resumption and integrity verification steps, a tiered backoff retransmission mechanism based on server connection status detection is also established. This tiered backoff retransmission mechanism includes a high-frequency probing phase, a mid-frequency retry phase, a low-frequency probing phase, and a status reset mechanism. In the high-frequency probing phase, when offline data packet transmission fails, a first preset period is used to attempt data transmission. In the mid-frequency retry phase, when the high-frequency probing fails, a second preset period is used for retransmission, where the second preset period is longer than the first preset period. In the low-frequency probing phase, when the mid-frequency retry fails, a third preset period is used to execute data transmission, where the third preset period is longer than the second preset period. The status reset mechanism immediately resets the transmission frequency to the first preset period when offline data packet transmission is successful in any phase.

[0016] Preferably, in the traffic quota monitoring and circuit breaker steps, if the cumulative data transmission traffic for the day is less than the preset traffic quota threshold, and the traffic quota threshold is less than the daily transmission traffic threshold, then the elastic transmission mode is automatically activated. The elastic transmission mode includes extending the time range of data transmission, dynamically adjusting the data transmission interval, and dynamically adjusting the transmission rate according to the ratio of remaining traffic to remaining time.

[0017] Preferably, in the network monitoring and breakpoint recording step, after recording the sequence number of the offline data packets that have not been transmitted in the database, the ship's navigation status is determined based on the pre-acquired real-time AIS data. When the navigation status is determined to be navigation, the offline data packet transmission is immediately terminated. When the navigation status is determined to be berthing, it is then determined whether the current network interface type is a mobile network. If not, the transmission queue is automatically frozen. If so, a probe data packet is sent to the speed test server based on the TCP / IP protocol to measure the downlink transmission rate and uplink transmission delay. The downlink transmission rate and uplink transmission delay are compared with corresponding preset thresholds. When the downlink transmission rate is greater than the preset transmission rate threshold and the uplink transmission delay is less than the preset delay time threshold, the offline data packet transmission is activated. When the downlink transmission rate is less than or equal to the preset transmission rate threshold or the uplink transmission delay is greater than or equal to the preset delay time threshold, the transmission is suspended.

[0018] Preferably, in the data transmission scheduling step, the security alarm data in the compressed lightweight dataset stored in the primary queue is transmitted using a time-priority mechanism. The time-priority mechanism includes assigning a unique identifier to each alarm event; sorting the transmission queues from nearest to farthest in terms of the occurrence time of the alarm events; and packaging all data associated with the same alarm event into a single dataset and performing atomic transmission.

[0019] Preferably, in the data transmission scheduling step, the real-time preemptive transmission refers to being executed immediately when the network is connected, and interrupting the transmission of other queues; the time-sensitive aggregation transmission refers to aggregating multiple sets of collision avoidance trajectory data within the collision avoidance cycle into a single batch vector dataset for transmission.

[0020] A traffic optimization system for ship-to-shore offline data transmission under restricted network conditions is characterized by comprising, in sequence, a data acquisition and lightweight processing module, a data compression processing module, a data transmission scheduling module, a traffic quota monitoring and circuit breaker module, a network monitoring and breakpoint recording module, and a breakpoint resumption and integrity verification module.

[0021] The data acquisition and lightweight processing module collects multi-source data from the ship in real time, including safety alarm data, collision avoidance trajectory data, and sensor data. On the ship, it performs differentiated preprocessing on the collected multi-source data, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into single-batch vector packets, and standardized encoding processing of safety alarm data. After the above differentiated preprocessing, a lightweight dataset adapted for ship-shore offline data transmission is generated.

[0022] The data compression processing module uses the ZLIB compression engine to compress the lightweight dataset after differential preprocessing in real time.

[0023] The data transmission scheduling module constructs a priority-layered model based on security levels, including a multi-level queue scheduling mechanism, and implements transmission scheduling according to security levels. The multi-level queues include a first-level queue, a second-level queue, and a third-level queue. The first-level queue stores security alarm data from the compressed lightweight dataset and sets it to the highest priority for real-time preemptive transmission. The second-level queue stores collision avoidance trajectory data from the compressed lightweight dataset and sets it to a medium priority for timely aggregation transmission. The third-level queue stores sensor data from the compressed lightweight dataset and sets it to the lowest priority for transmission at the minimum rate when there is bandwidth redundancy.

[0024] The traffic quota monitoring and circuit breaker module calculates the cumulative data transmission traffic of all queues from the ship to the shore in real time and compares the cumulative data transmission traffic with the preset daily traffic threshold. If the cumulative data transmission traffic of the day reaches the daily traffic threshold, the circuit breaker protection is activated and the data transmission of all queues for the day is stopped.

[0025] The network monitoring and breakpoint recording module monitors the network status in real time. When an abnormal network status is detected, it suspends data transmission of all queues from the ship to the shore and records the breakpoint status of each queue at the time of the abnormality. Then, it assigns a unique sequence number to each data packet to be transmitted in each queue, treats the data packets that have not been transmitted as offline data packets, and records the offline data packet sequence number in the database.

[0026] The interrupted transmission resume and integrity verification module, upon detecting network status recovery, resumes the transmission of offline data packets that have not been completed, based on the recorded transmission interruption status of each queue and the sequence number of the offline data packets that have not been completed, according to the priority order of each queue. It also uses a hash verification method to perform integrity verification on the resumed offline data packets. Offline data packets that fail the verification are re-entered into the corresponding priority queue for transmission. After all data packets are successfully verified, the traffic optimization of ship-shore offline data transmission under the restricted network is completed.

[0027] Preferably, the breakpoint resumption and integrity verification module further establishes a tiered backoff retransmission mechanism based on server connection status detection. This tiered backoff retransmission mechanism includes a high-frequency probing phase, a mid-frequency retry phase, a low-frequency probing phase, and a status reset mechanism. During the high-frequency probing phase, data transmission is attempted for a first preset period when offline data packet transmission fails. During the mid-frequency retry phase, retransmission is performed for a second preset period when the high-frequency probing fails, and the second preset period is longer than the first preset period. During the low-frequency probing phase, data transmission is performed for a third preset period when the mid-frequency retry fails, and the third preset period is longer than the second preset period. The status reset mechanism immediately resets the transmission frequency to the first preset period when offline data packet transmission is successful in any phase.

[0028] Preferably, in the traffic quota monitoring and circuit breaker module, if the cumulative data transmission traffic on a given day is less than a preset traffic quota threshold, and the traffic quota threshold is less than the daily transmission traffic threshold, then the elastic transmission mode is automatically activated. The elastic transmission mode includes extending the time range of data transmission, dynamically adjusting the data transmission interval, and dynamically adjusting the transmission rate according to the ratio of remaining traffic to remaining time.

[0029] And / or, in the data transmission scheduling module, the security alarm data in the compressed lightweight dataset stored in the primary queue is transmitted using a time-priority mechanism. The time-priority mechanism includes assigning a unique identifier to each alarm event; sorting the transmission queues from nearest to farthest in terms of the occurrence time of the alarm events; and packaging all data associated with the same alarm event into a single dataset and performing atomic transmission.

[0030] Preferably, in the network monitoring and breakpoint recording module, after recording the sequence number of offline data packets that have not been transmitted in the database, the navigation status of the ship is determined based on the pre-acquired real-time AIS data. When the navigation status is determined to be navigation, the offline data packet transmission is immediately terminated. When the navigation status is determined to be berthing, it is further determined whether the current network interface type is a mobile network. If not, the transmission queue is automatically frozen. If so, a probe data packet is sent to the speed test server based on the TCP / IP protocol to measure the downlink transmission rate and uplink transmission delay. The downlink transmission rate and uplink transmission delay are compared with corresponding preset thresholds. When the downlink transmission rate is greater than the preset transmission rate threshold and the uplink transmission delay is less than the preset delay time threshold, the offline data packet transmission is activated. When the downlink transmission rate is less than or equal to the preset transmission rate threshold or the uplink transmission delay is greater than or equal to the preset delay time threshold, the transmission is suspended.

[0031] The technical effects of this invention are as follows:

[0032] This invention provides a traffic optimization method for ship-to-shore offline data transmission under constrained network conditions. Even in unstable or weak network environments, it enables reliable data transmission between ship and shore with minimal bandwidth consumption without affecting the operation of ship business systems. First, multi-source data, including safety alarm data, collision avoidance trajectory data, and sensor data, is collected in real-time from the ship. The collected multi-source data undergoes differentiated preprocessing to generate a lightweight dataset suitable for ship-to-shore offline data transmission. Then, the ZLIB compression engine is used to compress the differentiated preprocessed lightweight dataset in real-time. This differentiated preprocessing reduces redundancy while preserving core data characteristics, generating lightweight data suitable for offline transmission. This improves data compatibility and inter-system data interaction capabilities. The ZLIB compression algorithm effectively reduces data volume, lowers network bandwidth usage, and reduces bandwidth consumption, significantly improving transmission efficiency. Furthermore, the compression process reduces storage space requirements, making it suitable for resource-constrained shipboard environments. By performing a series of data processing steps on the ship, the amount of data that needs to be transmitted to the shore is significantly reduced. Then, a priority-based hierarchical model with a multi-level queue scheduling mechanism based on security levels is constructed. Preemptive transmission, time-sensitive aggregation transmission, and minimum rate transmission are adopted according to priority. High-priority data (such as security alarm data) can preempt low-priority transmission channels in real time, ensuring that critical information is delivered as soon as possible. Medium-priority data (such as collision avoidance trajectory data) uses aggregation transmission to improve transmission throughput while ensuring timeliness. Low-priority data (such as sensor data) is transmitted using bandwidth redundancy periods to avoid wasting high-value communication resources. The priority transmission scheduling mechanism significantly improves the overall network resource utilization and achieves differentiated quality of service assurance. In other words, by combining a three-level priority queue with differentiated transmission strategies (real-time preemption of security alarms, time-sensitive aggregation of trajectory data, and adaptive bandwidth for sensor data), high-priority data is ensured to be transmitted first, preventing low-priority data from crowding out resources. At the same time, aggregation transmission reduces fragmented packet sending, lowers protocol overhead, and improves bandwidth utilization. It also counts the cumulative data transmission traffic of all queues from the ship to the shore in real time, and compares the cumulative data transmission traffic with the preset daily traffic threshold. If the cumulative data transmission traffic of a day reaches the daily traffic threshold, the circuit breaker protection is activated and the data transmission of all queues for that day is stopped. This effectively avoids the situation of excessive data transmission in a single day, avoids affecting the normal operation of the network, and saves costs.Then, the network status is monitored in real time. When the network status is abnormal, data transmission from the ship to the shore is suspended, and the transmission interruption status of each queue and the sequence number of the uncompleted data packets are recorded at the time of the anomaly. Finally, after the network status is restored, based on the recorded transmission interruption status of each queue and the sequence number of the uncompleted offline data packets, data is resumed in priority order, and a hash verification method is used to verify data integrity. Offline data packets that fail verification are re-entered into the corresponding queue for transmission. After all data packets are successfully verified, the traffic optimization of ship-shore offline data transmission under the restricted network is completed. The interruption resumption mechanism effectively reduces duplicate transmissions and greatly saves bandwidth resources. Hash verification ensures that the data is not tampered with or damaged during transmission, ensuring data security. At the same time, resuming transmission in priority order ensures that high-priority data is restored first, improving emergency response capabilities. The complete error retransmission mechanism improves the data transmission success rate and enhances the robustness and stability of the system.

[0033] This invention achieves the following effects through key technologies such as hierarchical data acquisition, lightweight datasets, real-time compression, priority scheduling, network monitoring, and breakpoint resumption and integrity verification: 1) Optimized bandwidth utilization: By performing local data processing and analysis on the ship, employing efficient data compression algorithms (such as ZLIB), and intelligent data buffering and priority sorting mechanisms, the amount of data that needs to be transmitted to the shore is significantly reduced. This not only lowers the cost of satellite communication but also improves bandwidth utilization, ensuring that critical information can be transmitted in a timely and accurate manner. 2) Improved data transmission efficiency and reliability: Feature extraction and downsampling techniques are used to preprocess sensor data, reducing redundant data; compression technology is used to further reduce data volume, adapting to the transmission capabilities of ship-shore restricted networks, reducing single packet transmission time, and lowering the risk of transmission interruption; and a multi-level queue scheduling mechanism based on security levels is designed to ensure the real-time nature of emergency data and the validity of other data, thereby enhancing the overall efficiency and reliability of data transmission. 3) Ensuring ship navigation safety: This invention particularly emphasizes the immediate transmission of critical data (such as ship safety alarms), ensuring the priority transmission of this information even under poor network conditions, which is crucial for maintaining the safe navigation of ships. 4) Economy and Flexibility: By delaying the transmission of non-urgent data or storing it locally for post-event analysis, and dynamically adjusting transmission strategies based on network conditions, communication costs are effectively controlled, and shipping companies are provided with a more flexible data management approach. In summary, this invention provides a comprehensive and effective solution that not only addresses current practical problems in ship communication but also lays a solid foundation for future technological development.

[0034] Furthermore, a tiered backoff and retransmission mechanism based on server connection status detection is established. This mechanism gradually extends the retransmission interval when data transmission fails, and immediately restores the initial transmission frequency when data is successfully transmitted. Additionally, when the cumulative data transmission traffic for the day is less than a preset traffic quota threshold, an elastic transmission mode is automatically activated. By implementing traffic quota monitoring and the tiered backoff and retransmission mechanism, reliable data transmission with minimal bandwidth usage can still be achieved even in unstable or weak network environments, avoiding data loss or duplicate transmissions caused by network fluctuations.

[0035] Furthermore, the safety alarm data stored in the primary queue undergoes a time-priority mechanism during transmission. This mechanism includes assigning a unique identifier to each alarm event; sorting the transmission queues by the time the alarm events occurred, from most recent to oldest; and packaging all data associated with the same alarm event into a single dataset and performing atomic transmission. This effectively avoids incomplete alarm information received by the shore end due to fragmented transmissions (e.g., only the warning trigger record is available, but subsequent handling logs are missing), ensuring the integrity of the event context, that is, ensuring that the most recent safety events are handled first (e.g., the most recent collision warning is more important than last week's fuel consumption data). In addition, packaging associated data effectively reduces the number of communication handshakes (a single transmission saves more than 30% of the overhead compared to multiple transmissions).

[0036] This invention also relates to a traffic optimization system for ship-to-shore offline data transmission under restricted networks. This system corresponds to the aforementioned traffic optimization method for ship-to-shore offline data transmission under restricted networks. It can be understood as a system that implements the aforementioned traffic optimization method for ship-to-shore offline data transmission under restricted networks. The system includes, in sequence, a data acquisition and lightweight processing module, a data compression processing module, a data transmission scheduling module, a traffic quota monitoring and circuit breaker module, a network monitoring and breakpoint recording module, and a breakpoint resumption and integrity verification module. These modules work collaboratively, performing local data processing and analysis on the ship, employing efficient data compression algorithms, and intelligent data buffering and priority sorting mechanisms. This significantly reduces the amount of data that needs to be transmitted to the shore, not only lowering satellite communication costs but also improving bandwidth utilization and ensuring that critical information can be transmitted in a timely and accurate manner. By differentially preprocessing different types of multi-source data, a lightweight dataset adapted for ship-to-shore offline data transmission is generated, reducing redundant data. Compression technology is used to further reduce data volume. A multi-level queue scheduling mechanism based on security levels is designed to ensure the real-time nature of emergency data and the validity of other data, thereby enhancing the overall efficiency and reliability of data transmission. This invention places particular emphasis on the real-time transmission of critical data (such as ship safety alarms), ensuring the priority delivery of this information even under poor network conditions. This is crucial for maintaining the safe navigation of ships. This invention not only solves practical problems in current ship communication but also lays a solid foundation for future technological development. Attached Figure Description

[0037] Figure 1 This is a flowchart of the traffic optimization method for ship-to-shore offline data transmission under a restricted network according to the present invention.

[0038] Figure 2 This is a preferred flowchart of the traffic optimization method for ship-to-shore offline data transmission under a restricted network according to the present invention.

[0039] Figure 3 This is a flowchart of the stepped backoff and retransmission mechanism of the present invention. Detailed Implementation

[0040] The present invention will now be described with reference to the accompanying drawings.

[0041] This invention relates to a traffic optimization method for ship-to-shore offline data transmission under constrained network conditions. It addresses the handling of offline messages (messages that have failed to transmit, which are persistently stored in a database and trigger an automatic retransmission mechanism when the network recovers) in ship-to-shore communication. While ensuring real-time performance and reliability, it achieves minimum bandwidth transmission of ship-side data (sensor data, alarm information, event logs, etc.) to the shore. In unstable or weak network environments, it can achieve reliable data transmission between ship and shore with minimal bandwidth consumption without affecting the operation of the ship's business systems (i.e., reducing the bandwidth consumption of non-urgent data while ensuring the reliability of critical data). The flowchart of this method is as follows... Figure 1 As shown, the steps are as follows:

[0042] I. Data Acquisition and Lightweight Processing Steps: Real-time acquisition of multi-source data from the ship, including safety alarm data, collision avoidance trajectory data, and sensor data; differentiated preprocessing of the acquired multi-source data at the ship, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into single-batch vector packets, and standardized encoding processing of the safety alarm data; after the above differentiated preprocessing, a lightweight dataset adapted for ship-shore offline data transmission is generated.

[0043] Specifically, firstly, multi-source data, including safety alarm data, collision avoidance trajectory data, and sensor data, is collected in real time from the ship's end; then, with lightweight ship-end data as the core principle, optimization processing is performed before transmission, that is, differentiated preprocessing of the collected multi-source data at the ship's end; such as... Figure 2As shown, the collected multi-source data is reorganized, and the safety alarm data is directly standardized and encoded into structured alarm messages. For offline retransmission scenarios, the multi-target collision avoidance trajectory data within the collision avoidance cycle is aggregated into single-batch vector packets for transmission, reducing the frequency of fragmented transmission. Simultaneously, while ensuring the integrity of key features, high-frame-rate sensor data (such as video streams, LiDAR point cloud data / GPS data) undergoes dynamic frame extraction, downsampling, and feature extraction to generate lightweight datasets suitable for ship-to-shore transmission, significantly reducing the amount of redundant data that needs to be transmitted to the shore. In other words, standardized encoding, dynamic frame extraction, and aggregation are "differentiated" operations for different data types, ensuring that all three types of core data meet the interface requirements and bandwidth characteristics of ship-to-shore offline transmission. Specifically, 1) safety alarm data consists of structured alarm information based on real-time monitoring of crew behavior according to navigation safety regulations, including alarms related to job regulations (irregular lookout, insufficient on-duty personnel, captain's non-standard watchkeeping) and alarms related to safety equipment (not wearing work clothes, not wearing a safety helmet, etc.). 2) Collision avoidance trajectory data includes: analysis results of the dynamic trajectory of vessels at risk of collision, including: predicted trajectories of vessels at risk of collision with the vessel (including TCPA / DCPA), collision avoidance motion vectors of surrounding vessels (heading, speed, distance), risk level markings, and recommended avoidance schemes. 3) Sensor data includes: raw data streams from navigation equipment collected via a shipboard serial port server, including position and navigation data (such as AIS, GPS, inertial navigation, etc.), environmental perception data (such as wind speed and direction sensors, lidar, depth sounders, etc.), and vessel status data (such as rudder angle, main engine speed, etc.).

[0044] II. Data Compression Processing Steps: The ZLIB compression engine is used to compress the lightweight dataset after differential preprocessing in real time.

[0045] Specifically, in ship-to-shore communication scenarios supported by satellite links, bandwidth resources are highly scarce and a traffic-based billing model is adopted. For the raw text data (including highly redundant data structures) and structured alarm message data encoded in the sensor data within lightweight datasets, the ZLIB compression engine employs efficient compression algorithms (such as those based on Huffman coding or dedicated formats) to compress all data to be transmitted (safety alarm data, collision avoidance trajectory data, and sensor data), further reducing bandwidth consumption and achieving a compression rate of 70%–90%. Its technical advantages are: 1) Improved transmission efficiency: Data volume is compressed to 10%–30% of its original size (e.g., 10MB → 2MB), and transmission latency is reduced by more than 60%. 2) Enhanced packet loss resistance: Compressed data packets are smaller, reducing the probability of retransmission due to packet loss. 3) Optimized storage costs: Reduced data storage space after compression directly reduces the load on cloud server storage clusters. This invention uses the Zlib compression method. The Zlib compression engine is a very popular compression library that supports multiple compression algorithms and is highly effective in data compression and decompression.

[0046] III. Data Transmission Scheduling Steps: Addressing the intermittent opening of satellite communication windows, this invention designs a multi-level queue scheduling mechanism based on security levels. First, a priority-layered model based on security levels, including a multi-level queue scheduling mechanism, is constructed, and transmission scheduling is implemented according to security levels. The multi-level queues include a first-level queue (P0), a second-level queue (P1), and a third-level queue (P2). The first-level queue stores security alarm data from the compressed lightweight dataset and sets it to the highest priority for real-time preemptive transmission when the communication window is open (i.e., it executes immediately upon network connectivity, interrupting transmission in other queues). The second-level queue stores collision avoidance trajectory data from the compressed lightweight dataset and sets it to a medium priority for timely aggregation and transmission. This involves performing data encapsulation processing on the collision avoidance trajectory data. For offline retransmission scenarios, multiple sets of collision avoidance trajectory data within the collision avoidance period (i.e., within a continuous time window) are aggregated (packed and merged) into a single batch of vector datasets for transmission, reducing the frequency of fragmented transmissions. The compressed, lightweight dataset contains Level 3 sensor data stored in a three-level queue and set to the lowest priority for transmission at the minimum rate during periods of bandwidth redundancy (i.e., transmission at the minimum rate when bandwidth is idle). This optimizes bandwidth utilization by delaying the transmission of regular, large-volume data (such as raw sensor logs) until bandwidth redundancy occurs or storing it locally for post-analysis. Furthermore, ship speed and collision avoidance risk index are collected in real time. Transmission priority is dynamically adjusted based on data type and the real-time collected speed and risk index. Data priority is increased when the following conditions are met: 1) Ship speed exceeds a preset safety threshold; 2) Collision avoidance risk index reaches an emergency level.

[0047] Furthermore, differential compression processing is performed on the collision avoidance trajectory data, meaning only trajectory changes are transmitted (when longitude, latitude, TCPA, and DPCA change). The specific implementation strategy of the priority hierarchical model is shown in Table 1.

[0048] Table 1

[0049]

[0050] IV. Traffic Quota Monitoring and Circuit Breaker Procedure: Implement traffic quota monitoring, and calculate the cumulative data transmission traffic of all queues from the ship to the shore in real time. Compare the cumulative data transmission traffic with the preset daily traffic threshold. If the cumulative data transmission traffic reaches the daily traffic threshold, activate circuit breaker protection and stop all queues from transmitting data for the day to avoid network congestion that could affect the normal operation of the network.

[0051] V. Network Monitoring and Breakpoint Recording Steps: First, determine if the server connection is successful. If the server connection is successful, send messages according to the priority order of each queue and determine if the message was sent successfully. If the message was sent successfully, store the log record; if the message failed to be sent, save the untransmitted data packets to the database. Then, monitor the network status in real time. When an abnormal network status is detected, suspend data transmission of all queues from the ship to the shore and record the transmission breakpoint status of each queue at the time of the abnormality. Then, assign a unique sequence number to each data packet in each queue, treat the untransmitted data packets as offline data packets, and record the offline data packet sequence number in the database. Preferably, after recording the sequence number of the untransmitted offline data packets in the database, determine the ship's navigation status based on the pre-acquired real-time AIS data. When the navigation status is determined to be navigation, immediately terminate the offline data packet transmission; for example... Figure 2 As shown, berthing, network speed, traffic, and recent date data can be determined sequentially. When the navigation status is determined to be berthing, it is then determined whether the current network interface type is a mobile network. If not, the transmission queue is automatically frozen. If so, a probe data packet is sent to the speed test server based on the TCP / IP protocol to measure the downlink transmission rate and uplink transmission delay. The downlink transmission rate and uplink transmission delay are compared with the corresponding preset thresholds. When the downlink transmission rate is greater than the preset transmission rate threshold and the uplink transmission delay is less than the preset delay time threshold, offline data packet transmission is activated. When the downlink transmission rate is less than or equal to the preset transmission rate threshold or the uplink transmission delay is greater than or equal to the preset delay time threshold, transmission is suspended. That is, a 128KB probe packet is sent to the speed test server based on the TCP / IP protocol. When the downlink rate is greater than 1.5Mbps and the uplink delay is less than 800ms, the transmission channel is developed (activated). When the network quality drops below the threshold (i.e., the downlink rate is less than or equal to 1.5Mbps or the uplink delay is greater than or equal to 800ms), data transmission is suspended within 200ms.

[0052] VI. Resumption of Transmission and Integrity Verification Steps: When network status is detected to be restored, based on the recorded transmission interruption status of each queue and the sequence number of offline data packets that have not been transmitted, the offline data packets that have not been transmitted are resumed in order of priority of each queue. The integrity of the offline data packets that have resumed transmission is verified by a hash verification method. Offline data packets that fail the verification are re-entered into the corresponding priority queue for transmission. After all data packets have been verified successfully, the traffic optimization of ship-shore offline data transmission under the restricted network is completed.

[0053] Preferably, the present invention also designs optimization strategies including an adaptive network retransmission strategy, a transmission optimization strategy based on timeliness priority and traffic circuit breaking, a ship-side data timeliness window storage strategy, and a ship offline data transmission constraint strategy. Among these,

[0054] 1. Adaptive network retransmission strategy. Applicable to breakpoint resumption and integrity verification steps, it establishes a tiered backoff retransmission mechanism based on server connection status detection, such as... Figure 3 As shown, the specific implementation steps are as follows:

[0055] 1) High-frequency probing phase

[0056] When offline data packet (offline message) transmission fails, the system attempts to send data in the first preset period, that is, it attempts to send data in batches at a period of 5 seconds / time (the size of a single send is 5 sample data); if the data packet does not receive an acknowledgment (ACK) from the server, the status degradation process is initiated.

[0057] 2) Intermediate frequency retry phase

[0058] When the high-frequency probe fails, a second preset period is used for retransmission, with the retransmission interval extended to a 30-second period (30 seconds / transmission), maintaining a batch transmission scale of 5 data items per transmission; if there is still no valid ACK response, the next level state transition is triggered.

[0059] 3) Low-frequency detection phase

[0060] When the intermediate frequency retry fails, the third preset period is used to perform data transmission, that is, the period is further extended to 60 seconds / time to perform data transmission (5 samples are sent at a time); when the transmission fails continuously, the network is determined to be unavailable and the transmission task is actively suspended.

[0061] 4) State reset mechanism

[0062] When an offline data packet is successfully sent at any stage, the system immediately resets to the transmission frequency of the first preset period, that is, immediately resets to the high-frequency probing state (5-second cycle), and clears the cache queue of confirmed data.

[0063] 2. Transmission optimization strategy based on timeliness priority and traffic circuit breaking. Establish a timeliness-oriented hierarchical transmission mechanism, combined with daily traffic circuit breaking protection rules, to achieve efficient backhaul of critical data and refined resource management. Specific implementation steps are as follows:

[0064] 1) Time-priority transmission mechanism

[0065] For data transmission scheduling steps, the security alarm data in the compressed lightweight dataset stored in the primary queue is transmitted using a time-priority mechanism. This mechanism involves assigning a unique identifier to each alarm event and scheduling data transmission in reverse chronological order (most recent date first), with each alarm event as the smallest transmission unit. Specifically, each independent alarm event is assigned a unique ID (e.g., "2023-08-20_Collision Warning_001"). When multiple alarms are pending transmission, the transmission queue is sorted from most recent to oldest based on the alarm event occurrence time, prioritizing the transmission of the event with the latest timestamp. For example, today's collision warning is transmitted first, followed by yesterday's device fault alarm. Then, atomic transmission is performed on the complete dataset associated with the same alarm event ID (the entire data of the event is returned in a single session) to ensure the integrity of the event context. That is, all data related to the same alarm event ID (such as warning trigger records, subsequent trajectory data, and handling logs) must: a) be packaged into a single dataset; b) be transmitted completely in one go (sending in multiple sessions is not allowed) to avoid the shore receiving incomplete alarm information due to multiple transmissions (such as only having warning trigger records but missing subsequent handling logs), and to ensure that the latest safety events are handled first (such as the most recent collision warning being more important than last week's fuel consumption data). By packaging associated data, the number of communication handshakes is effectively reduced (a single transmission saves more than 30% of the overhead compared to multiple transmissions).

[0066] 2) Daily traffic quota circuit breaker mechanism

[0067] This system is applicable to traffic quota monitoring and circuit breaker procedures. During transmission, it counts the consumed traffic in real time, that is, it monitors the cumulative data transmission traffic of all queues every day and compares the cumulative data transmission traffic with the preset daily transmission traffic threshold (set to 30MB / day as the system traffic threshold (hardware configurable parameter)). When the cumulative value reaches the threshold, the circuit breaker protection is activated immediately, terminating the subsequent data transmission for the day. In other words, if the cumulative data transmission traffic for the day is greater than or equal to the daily transmission traffic threshold, the data transmission of all queues for the day is suspended to avoid the risk of exceeding satellite tariffs.

[0068] 3) Dynamic bandwidth control strategy

[0069] This applies to traffic quota monitoring and circuit breaker procedures. If the cumulative data transmission traffic for the day is less than the preset traffic quota threshold (i.e., the cumulative data transmission traffic for the day is <25MB), the system automatically activates the elastic transmission mode. The elastic transmission mode includes extending the time range for data transmission, dynamically adjusting the data transmission interval, and dynamically adjusting the transmission rate according to the ratio of remaining traffic to remaining time.

[0070] Extend the time range of transmitted data: send additional offline data within the adjacent time window (T-1 to T-3 days);

[0071] Dynamically adjust the data transmission interval (reduce transmission density): Gradually increase the transmission interval to 2-5 times the base value (default base interval = 5s);

[0072] The transmission rate is dynamically adjusted according to the ratio of remaining bandwidth to remaining time (rate adaptive control): The transmission rate is dynamically adjusted using the following formula:

[0073] Rate = (Remaining Quota / Remaining Time) × Safety Factor (0.6)

[0074] 3. The shipboard data timeliness window storage strategy can be understood as a pre-processing optimization step in the data transmission scheduling process, used to complete the timeliness-based stratification and screening of data before transmission scheduling. A configurable data timeliness management mechanism is established, which performs stratified processing of offline data based on preset storage duration thresholds. The specific implementation steps are as follows:

[0075] 1) Time-sensitive transmission window constraints

[0076] The system sets a dynamic storage time window threshold (by default, it retains data from the most recent 30 days, and supports modification to 15 / 60 days, etc., via configuration file). Ship-to-shore transmission tasks are only performed on historical data generated within the time window to avoid consuming valuable bandwidth by transmitting outdated data and to ensure that the data obtained by the shore-based center has time-sensitive value.

[0077] 2) Localized processing of overdue data

[0078] Data exceeding the time window will be automatically archived: transmission will be terminated: it will no longer be included in the communication scheduling queue and will be exempted from satellite link transmission (i.e., it will no longer consume satellite traffic quota). For example, GPS data older than 31 days will stop being transmitted to the shore.

[0079] Local persistent storage: Fully retained in the ship's database, supporting post-event traceability and query (supporting local retrieval and accident tracing);

[0080] Resource isolation mechanism: Archived data is stored independently in a cold backup partition (such as a dedicated hard drive), physically isolated from transferable data (different disk partitions) to prevent accidental deletion or malicious tampering.

[0081] 4. Offline Data Transmission Constraint Strategy for Ships. A multi-dimensional transmission control mechanism is established based on ship operating status, network environment, and transmission security. Specific rules are as follows:

[0082] 1) Ship navigation status constraints correspond to the timing decision of the data transmission scheduling mechanism in the data transmission scheduling steps.

[0083] The system parses the AIS (Automatic Identification System) real-time data stream and activates offline data transmission only when the navigation status is "berthed" (IMO status code = 5). Transmission is immediately terminated when the ship's navigation status changes to "navigating".

[0084] 2) Network access type selection, corresponding to the network decision-making of the transmission scheduling mechanism in the data transmission scheduling steps.

[0085] The system detects the currently active network interface type (4G / VSAT / WiFi) through the operating system layer API, and starts transmission only when connected to a 4G mobile network (interface identifier CELLULAR_NETWORK). When switching to high-cost links such as maritime satellite VSAT, the transmission queue is automatically frozen (to avoid high-cost satellite communication).

[0086] 3) Dynamic network quality assessment, corresponding to the link decision-making mechanism of the data transmission scheduling step.

[0087] The system sends a 128KB probe packet to the speed test server based on the TCP / IP protocol. When the downlink speed is greater than 1.5Mbps and the uplink latency is less than 800ms, the transmission channel is developed (activated). When the network quality drops below the threshold (i.e., the downlink speed is less than or equal to 1.5Mbps or the uplink latency is greater than or equal to 800ms), data transmission is suspended within 200ms.

[0088] 4) Hard rate limiting of transmission rate corresponds to the traffic decision of the transmission scheduling mechanism in the data transmission scheduling steps.

[0089] The token bucket algorithm is used to limit the sending speed to no more than 10kbps, and kernel-level traffic control is simulated through Linux TC (Traffic Control).

[0090] 5) Packet-level transmission control, corresponding to the execution details of the transmission scheduling mechanism in the data transmission scheduling steps.

[0091] Each data entry is encapsulated into a TCP packet of 512 bytes or less (to avoid MTU fragmentation). The maximum number of retries per packet is 3. If a packet fails consecutively, it is marked as "offline unreachable" and the failed data packet is injected into the offline storage pool (to isolate the subsequent transmission queue).

[0092] 6) Resume interruption guarantee mechanism

[0093] This is applicable to network monitoring and breakpoint recording. It assigns a unique sequence number to each data packet in each queue and uses a breakpoint resume method to record the sequence number of offline data packets that have not been transmitted incompletely in the database, preventing data packets from being missed or duplicated when the software starts again.

[0094] 7) End-to-end data integrity verification

[0095] This method is suitable for resuming interrupted downloads and verifying file integrity. It uses a hash checksum method to verify the integrity of data packets in the resumed transmission. The MD5 hash value can be used to confirm whether the received file content is consistent with the original file, because even a small change in the file will result in a completely different MD5 hash value. By comparing the MD5 hash values ​​of the sender and receiver, it can be verified whether the file has remained unchanged during transmission, ensuring that the file has not been corrupted during transmission.

[0096] This invention also relates to a traffic optimization system for ship-to-shore offline data transmission under restricted networks. This system corresponds to the aforementioned traffic optimization method for ship-to-shore offline data transmission under restricted networks and can be understood as a system implementing the aforementioned method. The system includes, in sequence, a data acquisition and lightweight processing module, a data compression processing module, a data transmission scheduling module, a traffic quota monitoring and circuit breaker module, a network monitoring and breakpoint recording module, and a breakpoint resumption and integrity verification module. Specifically,

[0097] The data acquisition and lightweight processing module collects multi-source data from the ship in real time, including safety alarm data, collision avoidance trajectory data, and sensor data. On the ship, it performs differentiated preprocessing on the collected multi-source data, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into single-batch vector packets, and standardized encoding processing of safety alarm data. After the above differentiated preprocessing, a lightweight dataset adapted for ship-shore offline data transmission is generated.

[0098] The data compression processing module uses the ZLIB compression engine to compress the lightweight dataset after differential preprocessing in real time.

[0099] The data transmission scheduling module constructs a priority-layered model based on security levels, including a multi-level queue scheduling mechanism, and implements transmission scheduling according to security levels. The multi-level queues include a first-level queue, a second-level queue, and a third-level queue. The first-level queue stores security alarm data from the compressed lightweight dataset and sets it to the highest priority for real-time preemptive transmission. The second-level queue stores collision avoidance trajectory data from the compressed lightweight dataset and sets it to a medium priority for timely aggregation transmission. The third-level queue stores sensor data from the compressed lightweight dataset and sets it to the lowest priority for transmission at the minimum rate when there is bandwidth redundancy.

[0100] The traffic quota monitoring and circuit breaker module calculates the cumulative data transmission traffic of all queues from the ship to the shore in real time and compares the cumulative data transmission traffic with the preset daily traffic threshold. If the cumulative data transmission traffic of the day reaches the daily traffic threshold, the circuit breaker protection is activated and the data transmission of all queues for the day is stopped.

[0101] The network monitoring and breakpoint recording module monitors the network status in real time. When an abnormal network status is detected, it suspends data transmission of all queues from the ship to the shore and records the breakpoint status of each queue at the time of the abnormality. Then, it assigns a unique sequence number to each data packet to be transmitted in each queue, treats the data packets that have not been transmitted as offline data packets, and records the offline data packet sequence number in the database.

[0102] The interrupted transmission resume and integrity verification module, upon detecting network status recovery, resumes the transmission of offline data packets that have not been completed, based on the recorded transmission interruption status of each queue and the sequence number of the offline data packets that have not been completed, according to the priority order of each queue. It also uses a hash verification method to perform integrity verification on the resumed offline data packets. Offline data packets that fail the verification are re-entered into the corresponding priority queue for transmission. After all data packets are successfully verified, the traffic optimization of ship-shore offline data transmission under the restricted network is completed.

[0103] Preferably, the breakpoint resumption and integrity verification module also establishes a tiered backoff retransmission mechanism based on server connection status detection. This tiered backoff retransmission mechanism includes a high-frequency probing phase, a mid-frequency retry phase, a low-frequency probing phase, and a status reset mechanism. During the high-frequency probing phase, data transmission is attempted for a first preset period when offline data packet transmission fails. During the mid-frequency retry phase, retransmission is performed for a second preset period when the high-frequency probing fails, and the second preset period is longer than the first preset period. During the low-frequency probing phase, data transmission is performed for a third preset period when the mid-frequency retry fails, and the third preset period is longer than the second preset period. The status reset mechanism immediately resets the transmission frequency to the first preset period when offline data packet transmission is successful in any phase.

[0104] Preferably, in the traffic quota monitoring and circuit breaker module, if the cumulative data transmission traffic on a given day is less than a preset traffic quota threshold, and the traffic quota threshold is less than the daily transmission traffic threshold, then the elastic transmission mode is automatically activated. The elastic transmission mode includes extending the time range of data transmission, dynamically adjusting the data transmission interval, and dynamically adjusting the transmission rate according to the ratio of remaining traffic to remaining time.

[0105] And / or, in the data transmission scheduling module, the security alarm data in the compressed lightweight dataset stored in the primary queue is transmitted using a time-priority mechanism. The time-priority mechanism includes assigning a unique identifier to each alarm event; sorting the transmission queues from nearest to farthest in terms of the occurrence time of the alarm events; and packaging all data associated with the same alarm event into a single dataset and performing atomic transmission.

[0106] Preferably, in the network monitoring and breakpoint recording module, after recording the sequence number of offline data packets that have not been transmitted in the database, the navigation status of the ship is determined based on the pre-acquired real-time AIS data. When the navigation status is determined to be navigation, the offline data packet transmission is immediately terminated. When the navigation status is determined to be berthing, it is further determined whether the current network interface type is a mobile network. If not, the transmission queue is automatically frozen. If so, a probe data packet is sent to the speed test server based on the TCP / IP protocol to measure the downlink transmission rate and uplink transmission delay. The downlink transmission rate and uplink transmission delay are compared with corresponding preset thresholds. When the downlink transmission rate is greater than the preset transmission rate threshold and the uplink transmission delay is less than the preset delay time threshold, the offline data packet transmission is activated. When the downlink transmission rate is less than or equal to the preset transmission rate threshold or the uplink transmission delay is greater than or equal to the preset delay time threshold, the transmission is suspended.

[0107] This invention provides an objective and scientific method and system for optimizing the flow of ship-to-shore offline data transmission under limited network conditions. By performing local data processing and analysis on the ship, employing efficient data compression algorithms, and intelligent data buffering and priority sorting mechanisms, the amount of data that needs to be transmitted to the shore is significantly reduced. This not only lowers the cost of satellite communication but also improves bandwidth utilization, ensuring that critical information can be transmitted in a timely and accurate manner. Differential preprocessing of different types of multi-source data generates lightweight datasets adapted for ship-to-shore offline data transmission, reducing redundant data. Compression technology further reduces data volume. A multi-level queue scheduling mechanism based on security levels is designed to ensure the real-time nature of emergency data and the validity of other data, thereby enhancing the overall efficiency and reliability of data transmission. This invention particularly emphasizes the immediate transmission of critical data (such as ship safety alarms), ensuring the priority transmission of this information even under poor network conditions, which is crucial for maintaining the safe navigation of ships. This invention not only solves the practical problems in current ship communication but also lays a solid foundation for future technological development.

[0108] It should be noted that the specific embodiments described above enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail with reference to the accompanying drawings and embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. In short, all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention patent.

Claims

1. A method for optimizing the flow of offline data transmission between ship and shore under a constrained network, characterized in that, Includes the following steps: Data acquisition and lightweight processing steps: Real-time acquisition of multi-source data from the ship, including safety alarm data, collision avoidance trajectory data, and sensor data; Differentiated preprocessing of the acquired multi-source data at the ship, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into single-batch vector packets, and standardized encoding processing of safety alarm data; After the above differentiated preprocessing, a lightweight dataset adapted for ship-shore offline data transmission is generated. Data compression processing steps: The ZLIB compression engine is used to compress the lightweight dataset after differential preprocessing in real time; Data transmission scheduling steps: Construct a priority hierarchical model based on security levels, including a multi-level queue scheduling mechanism, and implement transmission scheduling according to security levels; the multi-level queues include a first-level queue, a second-level queue, and a third-level queue. The first-level queue stores the security alarm data in the compressed lightweight dataset and sets it to the highest priority for real-time preemptive transmission; the second-level queue stores the collision avoidance trajectory data in the compressed lightweight dataset and sets it to a medium priority for time-sensitive aggregated transmission; Sensor data from the compressed lightweight dataset is stored in the three-level queue and set to the lowest priority for transmission at the minimum rate in the event of bandwidth redundancy. Traffic quota monitoring and circuit breaker steps: Real-time statistics of the cumulative data transmission traffic of all queues from ship to shore, and compare the cumulative data transmission traffic with the preset daily transmission traffic threshold. If the cumulative data transmission traffic of the day is greater than or equal to the daily transmission traffic threshold, activate circuit breaker protection and stop the data transmission of all queues for the day. Network monitoring and breakpoint recording steps: Monitor the network status in real time. When an abnormal network status is detected, suspend data transmission of all queues from the ship to the shore and record the breakpoint status of each queue at the time of the abnormality. Then, assign a unique sequence number to each data packet to be transmitted in each queue, treat the data packets that have not been transmitted as offline data packets, and record the offline data packet sequence number in the database. Resumption of transmission and integrity verification steps: When network status recovery is detected, based on the recorded transmission interruption status of each queue and the sequence number of offline data packets that have not been transmitted, the offline data packets that have not been transmitted are resumed in order of priority of each queue. The integrity of the resumed offline data packets is verified by a hash verification method. Offline data packets that fail the verification are re-entered into the corresponding priority queue for transmission. After all data packets are verified successfully, the traffic optimization of ship-shore offline data transmission under the restricted network is completed.

2. The traffic optimization method for ship-to-shore offline data transmission under a restricted network according to claim 1, characterized in that, In the breakpoint resumption and integrity verification steps, a tiered backoff retransmission mechanism based on server connection status detection is also established. The tiered backoff retransmission mechanism includes a high-frequency probing phase, a medium-frequency retry phase, a low-frequency probing phase, and a status reset mechanism. In the high-frequency probing phase, data transmission is attempted to be sent using a first preset period when offline data packet transmission fails. In the medium-frequency retry phase, data is retransmitted using a second preset period when the high-frequency probing fails, and the second preset period is longer than the first preset period. During the low-frequency detection phase, if the mid-frequency retry fails, data transmission is performed using a third preset period, which is greater than the second preset period. The state reset mechanism immediately resets the transmission frequency to the first preset period when the offline data packet is successfully transmitted in any phase.

3. The traffic optimization method for ship-to-shore offline data transmission under a restricted network according to claim 1, characterized in that, In the traffic quota monitoring and circuit breaker steps, if the cumulative data transmission traffic on a given day is less than the preset traffic quota threshold, and the traffic quota threshold is less than the daily transmission traffic threshold, then the elastic transmission mode is automatically activated. The elastic transmission mode includes extending the time range of data transmission, dynamically adjusting the data transmission interval, and dynamically adjusting the transmission rate according to the ratio of remaining traffic to remaining time.

4. The traffic optimization method for ship-to-shore offline data transmission under a restricted network according to claim 1, characterized in that, In the network monitoring and breakpoint recording steps, after recording the sequence number of offline data packets that have not been transmitted in the database, the ship's navigation status is determined based on the pre-acquired real-time AIS data. If the navigation status is determined to be navigation, the offline data packet transmission is immediately terminated. If the navigation status is determined to be berthing, it is then determined whether the current network interface type is a mobile network. If not, the transmission queue is automatically frozen. If so, a probe data packet is sent to the speed test server based on the TCP / IP protocol to measure the downlink transmission rate and uplink transmission delay. The downlink transmission rate and uplink transmission delay are compared with corresponding preset thresholds. When the downlink transmission rate is greater than the preset transmission rate threshold and the uplink transmission delay is less than the preset delay time threshold, the offline data packet transmission is activated. When the downlink transmission rate is less than or equal to the preset transmission rate threshold or the uplink transmission delay is greater than or equal to the preset delay time threshold, the transmission is suspended.

5. The method for optimizing the flow of ship-to-shore offline data transmission under a restricted network according to any one of claims 1 to 4, characterized in that, In the data transmission scheduling step, the security alarm data in the compressed lightweight dataset stored in the primary queue is transmitted using a time-priority mechanism. This time-priority mechanism includes assigning a unique identifier to each alarm event; sorting the transmission queues from most recent to oldest alarm events based on their occurrence time; and packaging all data associated with the same alarm event into a single dataset and performing atomic transmission.

6. The traffic optimization method for ship-to-shore offline data transmission under a restricted network according to claim 5, characterized in that, In the data transmission scheduling steps, the real-time preemptive transmission refers to being executed immediately when the network is connected, interrupting the transmission of other queues; the time-sensitive aggregation transmission refers to aggregating multiple sets of collision avoidance trajectory data within the collision avoidance cycle into a single batch vector dataset for transmission.

7. A traffic optimization system for ship-to-shore offline data transmission under a restricted network, characterized in that, It includes, in sequence, a data acquisition and lightweight processing module, a data compression processing module, a data transmission scheduling module, a traffic quota monitoring and circuit breaker module, a network monitoring and breakpoint recording module, and a breakpoint resume and integrity verification module. The data acquisition and lightweight processing module collects multi-source data from the ship in real time, including safety alarm data, collision avoidance trajectory data, and sensor data. On the ship, it performs differentiated preprocessing on the collected multi-source data, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into single-batch vector packets, and standardized encoding processing of safety alarm data. After the above differentiated preprocessing, a lightweight dataset adapted for ship-shore offline data transmission is generated. The data compression processing module uses the ZLIB compression engine to compress the lightweight dataset after differential preprocessing in real time. The data transmission scheduling module constructs a priority hierarchical model based on security levels, including a multi-level queue scheduling mechanism, and implements transmission scheduling according to security levels. The multi-level queue includes a first-level queue, a second-level queue, and a third-level queue. The first-level queue stores security alarm data from the compressed lightweight dataset and sets it to the highest priority for real-time preemptive transmission. The second-level queue stores collision avoidance trajectory data from the compressed lightweight dataset and sets it to a medium priority for timely aggregated transmission. Sensor data from the compressed lightweight dataset is stored in the three-level queue and set to the lowest priority for transmission at the minimum rate in the event of bandwidth redundancy. The traffic quota monitoring and circuit breaker module calculates the cumulative data transmission traffic of all queues from the ship to the shore in real time and compares the cumulative data transmission traffic with the preset daily transmission traffic threshold. If the cumulative data transmission traffic on a given day is greater than or equal to the daily transmission traffic threshold, the circuit breaker protection is activated and the data transmission of all queues on that day is suspended. The network monitoring and breakpoint recording module monitors the network status in real time. When an abnormal network status is detected, it suspends data transmission of all queues from the ship to the shore and records the breakpoint status of each queue at the time of the abnormality. Then, it assigns a unique sequence number to each data packet to be transmitted in each queue, treats the data packets that have not been transmitted as offline data packets, and records the offline data packet sequence number in the database. The interrupted transmission resume and integrity verification module, upon detecting network status recovery, resumes the transmission of offline data packets that have not been completed, based on the recorded transmission interruption status of each queue and the sequence number of the offline data packets that have not been completed, according to the priority order of each queue. It also uses a hash verification method to perform integrity verification on the resumed offline data packets. Offline data packets that fail the verification are re-entered into the corresponding priority queue for transmission. After all data packets are successfully verified, the traffic optimization of ship-shore offline data transmission under the restricted network is completed.

8. The traffic optimization system for ship-to-shore offline data transmission under a restricted network according to claim 7, characterized in that, The breakpoint resume and integrity verification module also establishes a tiered backoff retransmission mechanism based on server connection status detection. The tiered backoff retransmission mechanism includes a high-frequency probing phase, a medium-frequency retry phase, a low-frequency probing phase, and a status reset mechanism. In the high-frequency probing phase, data transmission is attempted to be sent using a first preset period when offline data packet transmission fails. In the medium-frequency retry phase, data is retransmitted using a second preset period when the high-frequency probing fails, and the second preset period is longer than the first preset period. During the low-frequency detection phase, if the mid-frequency retry fails, data transmission is performed using a third preset period, which is greater than the second preset period. The state reset mechanism immediately resets the transmission frequency to the first preset period when the offline data packet is successfully transmitted in any phase.

9. The traffic optimization system for ship-to-shore offline data transmission under a restricted network according to claim 7 or 8, characterized in that, In the traffic quota monitoring and circuit breaker module, if the cumulative data transmission traffic on a given day is less than the preset traffic quota threshold, and the traffic quota threshold is less than the daily transmission traffic threshold, then the elastic transmission mode is automatically activated. The elastic transmission mode includes extending the time range of data transmission, dynamically adjusting the data transmission interval, and dynamically adjusting the transmission rate according to the ratio of remaining traffic to remaining time. And / or, in the data transmission scheduling module, the security alarm data in the compressed lightweight dataset stored in the primary queue is transmitted using a time-priority mechanism. The time-priority mechanism includes assigning a unique identifier to each alarm event; sorting the transmission queues from nearest to farthest in terms of the occurrence time of the alarm events; and packaging all data associated with the same alarm event into a single dataset and performing atomic transmission.

10. The traffic optimization system for ship-to-shore offline data transmission under a restricted network according to claim 7, characterized in that, In the network monitoring and breakpoint recording module, after recording the sequence number of offline data packets that have not been transmitted in the database, the navigation status of the ship is determined based on the pre-acquired real-time AIS data. When the navigation status is determined to be navigation, the offline data packet transmission is immediately terminated. When the navigation status is determined to be berthing, it is further determined whether the current network interface type is a mobile network. If not, the transmission queue is automatically frozen. If so, a probe data packet is sent to the speed test server based on the TCP / IP protocol to measure the downlink transmission rate and uplink transmission delay. The downlink transmission rate and uplink transmission delay are compared with corresponding preset thresholds. When the downlink transmission rate is greater than the preset transmission rate threshold and the uplink transmission delay is less than the preset delay time threshold, the offline data packet transmission is activated. When the downlink transmission rate is less than or equal to the preset transmission rate threshold or the uplink transmission delay is greater than or equal to the preset delay time threshold, the transmission is suspended.

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