Flow optimization method and system for ship-shore off-line data transmission under limited network

Abstract

The invention relates to a flow optimization method and system for ship-shore off-line data transmission under a limited network, and the system comprises the steps: firstly collecting multi-source data, including safety alarm data, collision avoidance trajectory data and sensor data, of a ship end in real time, carrying out the differential preprocessing to generate a lightweight data set, and then carrying out the real-time compression processing; then, constructing a priority hierarchical model comprising a multi-stage queue scheduling mechanism, implementing transmission scheduling according to the security level, performing traffic quota monitoring and fusing protection, monitoring the network state in real time, and pausing data transmission of all queues when the network state is abnormal; the method comprises the following steps of: acquiring an abnormal state of each queue, recording a transmission breakpoint state of each queue at an abnormal moment and a serial number of a data packet which is not transmitted completely, continuously transmitting data according to a priority sequence based on the recorded transmission breakpoint state of each queue and the serial number of the offline data packet which is not transmitted completely after a network state is recovered, and verifying data integrity by adopting a Hash verification method. And flow optimization of ship-shore off-line data transmission is completed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ship communication, in particular to a flow optimization method and system for ship-shore offline data transmission under a restricted network. BACKGROUND

[0002] When a ship sails in the marine environment, it is affected by climate conditions, environmental factors and base station coverage range, and mainly relies on satellite communication to realize long-distance communication. However, due to the limited bandwidth and inherent high delay characteristics of satellite communication network, the data transmission speed is low and the response time is long. In this case, not only the data transmission efficiency is affected, but also potential safety hazards are caused to key operations that need real-time update information (such as electronic chart, radar equipment data viewing, telegram sending, etc.).

[0003] Satellite communication services are usually charged according to data flow, which means that excessive network communication will directly lead to an increase in communication costs, becoming an important economic burden for shipping companies. In addition, if the satellite communication network used by the ship has limited bandwidth, excessive data transmission may cause network congestion problems, not only affecting the user experience of other users, but also affecting the normal use of other devices on the ship, such as viewing of electronic charts, radar equipment, etc., telegram sending, etc., which brings safety hazards to the ship sailing. Therefore, during the sailing process of the ship, how to effectively manage the flow usage, reduce the communication cost, and at the same time ensure the reliability and stability of the key communication, has important significance in the sailing of the ship.

[0004] The existing technology usually relies on directly transmitting data that has not been processed or has only been simply compressed through satellite link. This method does not fully consider the effective use of bandwidth and cost control. Specifically: high-frequency sensor data collected by the ship end (such as LiDAR point cloud, GPS positioning information, etc.) is generated at the original frame rate, and there is a lot of repeated or unnecessary information in continuous trajectory sampling, environmental monitoring values, etc., which occupies valuable limited bandwidth resources when directly transmitted; general compression methods are used for ship data (such as collision avoidance trajectory vector, device status log, etc.), and the volume after compression is still large, so it is impossible to maximize the reduction of data volume; each type of data such as ship safety alarm and routine operation log is transmitted in a unified order, which may cause delay in transmission of key information; the amount of data transmitted during the data transmission process directly changes with the amount of data generated, which may cause excessive data transmission in a single day, resulting in high fees due to excessive use of satellite communication, and also increasing the risk of network congestion, affecting the normal use experience of other users.

[0005] The existence of these problems makes it difficult for the ship to effectively manage the flow usage during navigation, reduces the communication cost, and ensures the reliability and stability of the key communication. Therefore, in the limited network environment, how to optimize the offline data transmission method between the ship and the shore, improve the data transmission efficiency, reduce the cost and ensure the reliability of the key communication is a problem to be solved at present. SUMMARY

[0006] To solve the problems of lack of effective local data processing, transmission in a unified order causing delay in transmission of key information, easy network congestion and insufficient data compression in the process of offline message transmission in the current ship-shore communication, the application provides a flow optimization method for offline data transmission between ship and shore in a limited network, which can greatly reduce the amount of data to be transmitted to the shore, reduce bandwidth consumption, optimize bandwidth utilization, and realize minimum bandwidth transmission of ship-end data (sensor data, alarm information, event log, etc.) to the shore in unstable or weak network environment. The application also relates to a flow optimization system for offline data transmission between ship and shore in a limited network.

[0007] The technical scheme of the application is as follows:

[0008] A flow optimization method for offline data transmission between ship and shore in a limited network, characterized in that it comprises the following steps:

[0009] Data acquisition and lightweight processing step: real-time acquisition of multi-source data including safety alarm data, collision avoidance trajectory data and sensor data at the ship end; differential preprocessing of the acquired multi-source data at the ship end, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into a single batch vector package, and standardized encoding processing of safety alarm data, to generate a lightweight data set adapted for offline data transmission between ship and shore after the above differential preprocessing;

[0010] Data compression processing step: real-time compression of the lightweight data set after differential preprocessing using ZLIB compression engine;

[0011] Data transmission scheduling step: constructing a priority layered model including a multi-level queue scheduling mechanism based on safety level, and implementing transmission scheduling according to safety level; the multi-level queue includes a first-level queue, a second-level queue and a third-level queue, the safety alarm data in the compressed lightweight data set is stored in the first-level queue and set as the highest priority for real-time preemptive transmission; the collision avoidance trajectory data in the compressed lightweight data set is stored in the second-level queue and set as the medium priority for time-sensitive aggregated transmission; the sensor data in the compressed lightweight data set is stored in the third-level queue and set as the lowest priority for transmission at the minimum rate when there is bandwidth redundancy;

[0012] The traffic quota monitoring and fusing step: the cumulative data transmission traffic of all queues from the ship end to the shore end is counted in real time, and the cumulative data transmission traffic is compared with the preset daily traffic threshold, if the cumulative data transmission traffic of the day reaches the daily traffic threshold, the fusing protection is activated and the data transmission of all queues in the day is stopped;

[0013] The network monitoring and breakpoint recording step: the network state is monitored in real time, when the network state is abnormal, the data transmission of all queues from the ship end to the shore end is suspended, the transmission breakpoint state of each queue at the time of abnormality is recorded, a unique sequence number is allocated to each data packet to be transmitted in each queue, the data packet to be transmitted is taken as an offline data packet, and the sequence number of the offline data packet is recorded in the database;

[0014] The breakpoint resume and integrity check step: when the network state is recovered, based on the recorded transmission breakpoint state of each queue and the sequence number of the offline data packet to be transmitted, the offline data packet to be transmitted is resumed in the order of the priority of each queue, and the integrity of the resumed offline data packet is checked by using the hash check method, the offline data packet that fails the check is retransmitted in the corresponding priority queue, and all data packets are checked successfully to complete the flow optimization of the offline data transmission from the ship to the shore under the restricted network.

[0015] Preferably, in the breakpoint resume and integrity check step, a ladder backoff retransmission mechanism based on server connection state detection is also established, which includes a high-frequency exploration stage, a medium-frequency retry stage, a low-frequency detection stage, and a state reset mechanism; the high-frequency exploration stage attempts data transmission with a first preset period when the offline data packet transmission fails; the medium-frequency retry stage retransmits with a second preset period when the high-frequency exploration fails, the second preset period is greater than the first preset period; the low-frequency detection stage performs data transmission with a third preset period when the medium-frequency retry fails, the third preset period is greater than the second preset period; the state reset mechanism immediately resets to the transmission frequency of the first preset period when the offline data packet transmission succeeds in any stage.

[0016] Preferably, in the traffic quota monitoring and fusing step, if the cumulative data transmission traffic of the day is less than the preset traffic quota threshold, and the traffic quota threshold is less than the daily transmission traffic threshold, the elastic transmission mode is automatically started, which includes expanding the time range of transmission data, dynamically adjusting the data transmission interval, and dynamically adjusting the transmission rate according to the proportion of the remaining traffic and the remaining time.

[0017] Preferably, in the network monitoring and breakpoint recording step, after recording the sequence number of the offline data packet in the database, the sailing state of the ship is determined according to the real-time AIS data obtained in advance, and the offline data packet transmission is terminated immediately when the sailing state is determined to be sailing; when the sailing state 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 yes, a probe data packet is sent to the speed measurement server based on the TCP / IP protocol, the downlink transmission rate and the uplink transmission delay are measured, and the downlink transmission rate and the uplink transmission delay are compared with the corresponding preset threshold values respectively, and the offline data packet transmission is activated when the downlink transmission rate is greater than the preset transmission rate threshold value and the uplink transmission delay is less than the preset delay time threshold value; when the downlink transmission rate is less than or equal to the preset transmission rate threshold value or the uplink transmission delay is greater than or equal to the preset delay time threshold value, the transmission is suspended.

[0018] Preferably, in the data transmission scheduling step, the safety alarm data in the compressed and lightweight data set stored in the primary queue is executed when the time limit priority mechanism is executed during transmission, the time limit priority mechanism includes assigning a unique identifier to each alarm event; the transmission queue is sorted from near to far according to the alarm event occurrence time; and all data associated with the same alarm event are packaged as a single data set and atomic transmission is performed.

[0019] Preferably, in the data transmission scheduling step, the real-time preemption transmission refers to immediate execution when the network is connected, and the transmission of other queues is interrupted; the time limit aggregation transmission refers to aggregating multiple groups of collision avoidance trajectory data within the collision avoidance period into a single batch of vector data set for transmission.

[0020] A flow optimization system for ship-shore offline data transmission under a restricted network, characterized by comprising a data acquisition and lightweight processing module, a data compression processing module, a data transmission scheduling module, a flow quota monitoring and fuse module, a network monitoring and breakpoint recording module, and a breakpoint resumption and integrity verification module connected in sequence,

[0021] The data acquisition and lightweight processing module acquires real-time multi-source data including safety alarm data, collision avoidance trajectory data and sensor data at the ship end; differentiates and pre-processes the acquired multi-source data at the ship end, including dynamic frame extraction processing of sensor data, aggregation processing of collision avoidance trajectory data into a single batch of vector package, and standardized encoding processing of safety alarm data, and generates a lightweight data set suitable for ship-shore offline data transmission after the above-mentioned differentiated preprocessing;

[0022] The data compression processing module uses ZLIB compression engine to compress the lightweight data set after differentiated preprocessing in real time;

[0023] The data transmission scheduling module constructs a priority layering model including a multi-level queue scheduling mechanism based on security levels, 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 security alarm data in the compressed and processed lightweight data set is stored in the first-level queue and is set as the highest priority for real-time pre-emptive transmission; the collision avoidance trajectory data in the compressed and processed lightweight data set is stored in the second-level queue and is set as the medium priority for time-sensitive aggregated transmission; the sensor data in the compressed and processed lightweight data set is stored in the third-level queue and is set as the lowest priority for transmission at the minimum rate when bandwidth is redundant.

[0024] The traffic quota monitoring and fusing module real-time counts the daily cumulative data transmission traffic of all queues from the ship end to the shore end, and compares the cumulative data transmission traffic with a preset daily traffic threshold, if the daily cumulative data transmission traffic reaches the daily traffic threshold, activates the fusing protection and suspends the data transmission of all queues from the ship end to the shore end on the same day.

[0025] The network monitoring and breakpoint recording module real-time monitors the network state, suspends the data transmission of all queues from the ship end to the shore end when an abnormal network state is monitored, records the transmission breakpoint state of each queue at the time of the abnormality, and assigns a unique sequence number to each data packet to be transmitted in each queue, takes the data packets to be transmitted as offline data packets, and records the sequence number of the offline data packets in the database.

[0026] The breakpoint resuming transmission and integrity checking module resumes the transmission of the offline data packets according to the priority order of each queue based on the recorded transmission breakpoint state of each queue and the sequence number of the offline data packets to be transmitted when the network state is recovered, and uses the hash checking method to check the integrity of the offline data packets to be transmitted, the offline data packets that fail the checking are retransmitted in the corresponding priority queue, and the offline data transmission from the ship to the shore under the restricted network is completed after all data packets are successfully checked.

[0027] Preferably, the breakpoint resuming transmission and integrity checking module further establishes a ladder-type backoff retransmission mechanism based on server connection state detection, the ladder-type backoff retransmission mechanism includes a high-frequency exploration stage, a medium-frequency retry stage, a low-frequency detection stage, and a state reset mechanism; the high-frequency exploration stage uses a first preset period to attempt data transmission when the offline data packet transmission fails; the medium-frequency retry stage uses a second preset period to retransmit when the high-frequency exploration fails, the second preset period is greater than the first preset period; the low-frequency detection stage uses a third preset period to perform data transmission when the medium-frequency retry fails, the third preset period is greater than the second preset period; the state reset mechanism immediately resets to the transmission frequency of the first preset period when the offline data packet transmission succeeds in any stage.

[0028] Preferably, in the flow quota monitoring and fusing module, if the daily cumulative data transmission flow is less than the preset flow quota threshold, and the flow quota threshold is less than the daily transmission flow threshold, the elastic transmission mode is automatically started, the elastic transmission mode includes expanding the time range of transmission data, dynamically adjusting the data sending interval, and dynamically adjusting the transmission rate according to the proportion of the remaining flow and the remaining time.

[0029] And / or, in the data transmission scheduling module, the security alarm data in the compressed and lightweight data set stored in the first queue executes the time-sensitive priority mechanism when transmitting, the time-sensitive priority mechanism includes assigning a unique identifier to each alarm event, sorting the transmission queue from near to far according to the alarm event occurrence time, and packaging all data associated with the same alarm event as a single data set and performing atomic transmission.

[0030] Preferably, in the network monitoring and breakpoint recording module, after recording the serial number of the offline data packet in the database, the sailing state of the ship is judged according to the real-time AIS data obtained in advance, and when the sailing state is judged as sailing, the transmission of the offline data packet is terminated immediately; when the sailing state is judged as berthing, it is further judged whether the current network interface type is a mobile network, if not, the transmission queue is automatically frozen, if yes, a probe data packet is sent to the speed measurement server based on the TCP / IP protocol, the downlink transmission rate and the uplink transmission delay are measured, and the downlink transmission rate and the uplink transmission delay are compared with the corresponding preset threshold respectively, 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 transmission of the offline data packet 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 the present application are as follows:

[0032] The application provides a flow optimization method for ship-shore offline data transmission under a restricted network. In an unstable or weak network environment, reliable data transmission with the lowest bandwidth occupation between the ship and the shore can be realized without affecting the operation of the ship business system. First, multi-source data including safety alarm data, collision avoidance trajectory data, and sensor data are collected in real time at the ship end, and the collected multi-source data are differentially preprocessed to generate a lightweight data set suitable for offline data transmission between the ship and the shore. Then, the differentially preprocessed lightweight data set is compressed in real time using the ZLIB compression engine. By differentially preprocessing, the core data features are retained, and the amount of redundant original data is reduced, generating lightweight data suitable for offline transmission. This improves data compatibility and data interaction capability between systems, effectively reduces data volume through the ZLIB compression algorithm, reduces network bandwidth occupation and bandwidth consumption, effectively improves transmission efficiency, and reduces storage space requirements through compression processing, making it suitable for resource-constrained shipboard environments. By processing data at the ship end, the amount of data transmitted to the shore end is greatly reduced. Then, a priority layering model based on a multi-level queue scheduling mechanism is constructed, and preemptive transmission, time-sensitive aggregated transmission, and minimum rate transmission are used according to priority. High-priority data (such as safety alarm data) can preempt low-priority transmission channels in real time to ensure that critical information is delivered in the first place. Medium-priority data (such as collision avoidance trajectory data) uses aggregated transmission to improve transmission throughput while ensuring timeliness. Low-priority data (such as sensor data) is transmitted during bandwidth redundancy periods to avoid wasting valuable communication resources. The priority transmission scheduling mechanism significantly improves overall network resource utilization and ensures differentiated quality of service. That is, by using a three-level priority queue combined with a differential transmission strategy (real-time preemption for safety alarms, time-sensitive aggregation for trajectory data, and bandwidth adaptation for sensor data), high-priority data is transmitted first, and low-priority data is prevented from occupying resources. At the same time, aggregated transmission reduces fragmented packet sending, reduces protocol overhead, and improves bandwidth utilization. The cumulative daily data transmission flow of all queues from the ship end to the shore end is calculated in real time, and the cumulative data transmission flow is compared with the preset daily flow threshold. If the daily cumulative data transmission flow reaches the daily flow threshold, the fuse protection is activated and the daily data transmission of all queues is stopped, effectively preventing excessive daily transmission data and avoiding affecting the normal operation of the network, saving costs.Then real-time monitoring of network state, when the network state is abnormal, suspend the ship end to the shore all the queue data transmission, and record the abnormal time of each queue transmission breakpoint state and the sequence number of the data packet of the incomplete transmission, finally, based on the recorded each queue transmission breakpoint state and the sequence number of the offline data packet of the incomplete transmission, the data is transmitted in priority order, and the hash check method is used to verify the data integrity, the offline data packet that fails in the verification is retransmitted to the corresponding queue, and the flow optimization of the ship-shore offline data transmission under the restricted network is completed after all the data packets are successfully verified, the breakpoint resume mechanism effectively reduces the repeated transmission, greatly saves the bandwidth resources, the hash check ensures that the data is not tampered or damaged during transmission, and the data security is guaranteed, and at the same time, the transmission is restored in priority order, ensuring that the high-priority data is restored first, improving the emergency response capability, improving the data transmission success rate through the complete error retransmission mechanism, and enhancing the system robustness and stability.

[0033] The application realizes the following effects through data acquisition grading + lightweight data set + real-time compression + priority scheduling + network monitoring + breakpoint resume and integrity check: 1) Optimize bandwidth utilization: by performing local data processing and analysis at the ship end, using efficient data compression algorithms (such as ZLIB), and intelligent data buffering and priority sorting mechanism, the amount of data that needs to be transmitted to the shore is greatly reduced, not only reducing the cost of satellite communication, but also improving the bandwidth utilization, ensuring that critical information can be timely and accurately conveyed. 2) Improve data transmission efficiency and reliability: use feature extraction and downsampling technology to preprocess sensor data, reduce redundant data; use compression technology to further reduce data volume, adapt to the transmission capacity of the ship-shore restricted network, reduce the single packet transmission time, and reduce the risk of transmission interruption; and design a multi-level queue scheduling mechanism based on security level, to ensure the real-time of emergency data and the effectiveness of other data, thereby enhancing the overall efficiency and reliability of data transmission. 3) Ensure the safety of ship navigation: the application emphasizes the immediate transmission of critical data (such as ship safety alarm), even in poor network conditions, to ensure the priority of these information, which is crucial for maintaining the safe navigation of ships. 4) Economy and flexibility: by delaying the transmission of non-urgent data or only storing it locally for post-analysis, and dynamically adjusting the transmission strategy according to the network conditions, the communication cost is effectively controlled, and a more flexible data management method is provided for shipping companies. In summary, the application provides a comprehensive and effective solution, which not only solves the current practical problems in ship communication, but also lays a solid foundation for future technological development.

[0034] Further, a step-by-step backoff retransmission mechanism based on server connection state detection is also established, which gradually extends the retransmission interval period when data transmission fails, and immediately restores the initial transmission frequency when data transmission is successful; and when the daily cumulative data transmission flow is less than the preset flow quota threshold, the elastic transmission mode is automatically started. Through the implementation of flow quota monitoring and step-by-step backoff retransmission mechanism, reliable data transmission with minimum bandwidth occupation can still be realized in unstable or weak network environment, avoiding data loss or repeated sending problems caused by network fluctuations.

[0035] Further, the security alarm data stored in the first queue is executed when the time limit priority mechanism is transmitted, the time limit priority mechanism includes assigning a unique identifier to each alarm event; the transmission queue is sorted from near to far according to the alarm event occurrence time; and all data associated with the same alarm event are packaged as a single data set and atomic transmission is performed. Effectively avoid incomplete alarm information received by the shore end due to multiple transmissions (such as only pre-warning trigger records are missing subsequent handling logs), ensuring the integrity of the event context, that is, ensuring that the latest security event is prioritized (such as the latest collision warning is more important than the oil consumption data last week); in addition, packaging associated data effectively reduces the number of communication handshakes (single transmission saves more than 30% overhead than multiple transmissions).

[0036] The present application also relates to a flow optimization system for ship-shore offline data transmission under a restricted network, which corresponds to the above-mentioned flow optimization method for ship-shore offline data transmission under a restricted network, and can be understood as a system for implementing the above-mentioned flow optimization method for ship-shore offline data transmission under a restricted network, comprising a data acquisition and lightweight processing module, a data compression processing module, a data transmission scheduling module, a flow quota monitoring and fuse module, a network monitoring and breakpoint recording module, and a breakpoint resuming and integrity checking module connected in turn, each module works cooperatively, through local data processing and analysis at the ship end, efficient data compression algorithm, and intelligent data buffering and priority sorting mechanism, the amount of data that needs to be transmitted to the shore end is greatly reduced, not only reducing the cost of satellite communication, but also improving the bandwidth utilization, ensuring that critical information can be transmitted in time and accurately. Through differential preprocessing of different types of multi-source data, lightweight data sets suitable for ship-shore offline data transmission are generated, reducing redundant data; compression technology is used to further reduce data volume; and a multi-level queue scheduling mechanism based on security level is designed to ensure the real-time of emergency data and the effectiveness of other data, thereby enhancing the overall efficiency and reliability of data transmission. The present application emphasizes the immediate transmission of critical data (such as ship safety alarms), which can ensure the priority transmission of these information even in poor network conditions, which is crucial for maintaining the safe navigation of ships. The present application not only solves the practical problems in current ship communication, but also lays a solid foundation for future technological development. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a flow chart of the flow optimization method of the offline data transmission between the ship and the shore under the restricted network of the application.

[0038] Figure 2 is a preferred flow chart of the flow optimization method of the offline data transmission between the ship and the shore under the restricted network of the application.

[0039] Figure 3 is a flow chart of the stepped backoff retransmission mechanism of the application. DETAILED DESCRIPTION

[0040] The application will be described below in conjunction with the accompanying drawings.

[0041] The application relates to a flow optimization method of offline data transmission between a ship and a shore under a restricted network, aiming at the processing of offline messages (referring to messages that fail to be transmitted and will be stored in a database persistently to trigger an automatic retransmission mechanism when the network recovers) in ship-shore communication, realizing the minimum bandwidth transmission of ship-end data (sensor data, alarm information, event log, etc.) to the shore end under the premise of guaranteeing real-time performance and reliability, and realizing reliable data transmission between the ship and the shore with the minimum bandwidth occupation under the premise of not affecting the operation of the ship business system (i.e. reducing the bandwidth occupation ratio of non-urgent data under the premise of guaranteeing the reliability of key data) in an unstable or weak network environment. The flow chart of the method is shown in Figure 1 and sequentially includes the following steps:

[0042] I. Data acquisition and lightweight processing step: real-time acquisition of multi-source data including safety alarm data, collision avoidance trajectory data and sensor data at the ship end; differential preprocessing of the acquired multi-source data at the ship end, including dynamic frame extraction processing of the sensor data, aggregation processing of the collision avoidance trajectory data into a single batch vector package, and standardized encoding processing of the safety alarm data, to generate a lightweight data set adapted to offline data transmission between the ship and the shore through the above differential preprocessing.

[0043] Specifically, first, real-time acquisition of multi-source data including safety alarm data, collision avoidance trajectory data and sensor data at the ship end; then, lightweight processing of the ship-end data as the core criterion, performing optimization processing before transmission, i.e. differential preprocessing of the acquired multi-source data at the ship end; for example, Figure 2As shown, the collected multi-source data is reorganized, and the safety alarm data is directly standardized and encoded, i.e., the safety alarm data is directly encoded into structured alarm messages; and for the offline supplement scenario, the multi-target collision avoidance trajectory data within the collision avoidance period is aggregated into a single batch vector package for transmission, reducing the fragmentation transmission frequency. At the same time, under the premise of ensuring the lossless of key features, dynamic frame extraction processing, downsampling, feature extraction and other lightweight processing are implemented on high frame rate sensor data (such as video stream, LiDAR point cloud data / GPS data), to generate lightweight data sets suitable for ship-shore transmission, so as to greatly reduce the amount of redundant data to be transmitted to the shore. That is, standardized encoding, dynamic frame extraction and aggregation are "differentiated" operations for different data types, ensuring that the three types of core data can meet the interface requirements and bandwidth characteristics of ship-shore offline transmission. Among them, 1) safety alarm data: structured alarm information based on real-time monitoring of crew behavior according to driving safety specifications, including post specification alarms (irregular lookout, insufficient number of watchmen, non-standard captain watch), safety equipment alarms (not wearing work clothes, not wearing safety helmet, etc.). 2) Collision avoidance trajectory data: analysis results of dynamic trajectory of ships with collision risk, including: predicted trajectories of ships with collision risk with the ship (including TCPA / DCPA), motion vectors (heading, speed, distance) of surrounding ships for collision avoidance, risk level labeling and recommended avoidance scheme. 3) Sensor data: raw data stream collected by the ship-end serial server, including position navigation (such as AIS, GPS, inertial navigation, etc.), environmental perception (such as anemorumbometer, laser radar, depth finder, etc.), and ship state (such as rudder angle, engine speed, etc.).

[0044] II. Data compression processing step: using ZLIB compression engine to compress the lightweight data sets after differentiated preprocessing in real time.

[0045] Specifically, in the ship-shore communication scenario supported by satellite link, bandwidth resources are highly scarce and a traffic billing mode is adopted. For original text data (containing high redundancy data structure) in lightweight data set of sensor data and encoded structured alarm message data, all data to be transmitted (safety alarm data, collision avoidance trajectory data and sensor data) are compressed by ZLIB compression engine using efficient compression algorithm (such as Huffman coding or special format) to further reduce bandwidth consumption and achieve a compression rate of 70% to 90%. The technical advantages are as follows: 1) transmission efficiency is improved: the data volume is compressed to 10% to 30% of the original size (such as 10MB to 2MB), and the transmission delay is reduced by more than 60%. 2) Anti-packet loss capability is enhanced: compressed data packets are smaller, reducing the probability of retransmission caused by packet loss. 3) storage cost is optimized: compressed data storage space is reduced, directly reducing the load of cloud server storage cluster. The application uses Zlib compression method. Zlib compression engine is a very popular compression library that supports multiple compression algorithms and is very effective in data compression and decompression.

[0046] III. Data transmission scheduling step: In view of the intermittent opening characteristics of the satellite communication window, the application designs a multi-level queue scheduling mechanism based on safety level. First, a priority layered model including a multi-level queue scheduling mechanism based on safety level is constructed, and transmission scheduling is implemented according to safety level. The multi-level queue includes a first-level queue (P0), a second-level queue (P1) and a third-level queue (P2). The safety alarm data in the lightweight data set after compression is stored in the first-level queue and set as the highest priority for real-time preemptive transmission when the communication window is opened (i.e. immediately executed when the network is connected, and the transmission of other queues is interrupted). The collision avoidance trajectory data in the lightweight data set after compression is stored in the second-level queue and set as the medium priority for time-sensitive aggregated transmission, i.e. data packaging processing is performed on the collision avoidance trajectory data, and for offline retransmission scenario, multiple groups 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 data set for transmission to reduce the frequency of fragmented transmission. The third-level sensor data in the lightweight data set after compression is stored in the third-level queue and set as the lowest priority for transmission at the minimum rate when the bandwidth is redundant (i.e. sent at the minimum rate when the bandwidth is idle), and the regular large capacity data (such as original sensor log) is delayed for transmission or only stored locally for subsequent analysis, thereby optimizing the bandwidth utilization. In addition, the ship speed and collision avoidance risk index are collected in real time, and the transmission priority is dynamically adjusted according to the data type and the real-time collected speed and risk index. When the following conditions are met, the data priority is improved: 1) the ship speed exceeds the preset safety threshold; 2) the collision avoidance risk index reaches the 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. Breakpoint resume and integrity check step: when the network state is monitored to recover, based on the recorded transmission breakpoint state of each queue and the sequence number of the offline data packet not completed, the offline data packet not completed is resumed in the order of the priority of each queue, and the hash check method is used to check the integrity of the offline data packet resumed, the offline data packet failed in the check is re-entered into the corresponding priority queue for transmission, and all data packets are checked successfully to complete the flow optimization of the ship-shore offline data transmission under the restricted network.

[0053] Preferably, the application also designs an optimization strategy including an adaptive network retransmission strategy, a transmission optimization strategy based on time priority and flow melting, a ship end data time window storage strategy, and a ship offline data transmission constraint strategy. Among them,

[0054] 1. Adaptive network retransmission strategy. It is suitable for the breakpoint resume and integrity check step, and establishes a ladder backoff retransmission mechanism based on server connection state detection, as shown in Figure 3 , the specific implementation steps are as follows:

[0055] 1) High frequency exploration stage

[0056] When the offline data packet (offline message) transmission fails, the first preset period is used to attempt data sending, i.e. the initial 5 seconds / attempt is used to attempt batch sending of data (5 sample data per single sending); if the data packet is not received by the server confirmation (ACK), the state degradation process is started.

[0057] 2) Medium frequency retry stage

[0058] When the high frequency exploration fails, the second preset period is used for retransmission, and the retransmission interval is extended to 30 seconds period (30 seconds / attempt), and the batch sending scale of 5 data per single is maintained; if there is still no effective ACK response, the next level state migration is triggered.

[0059] 3) Low frequency detection stage

[0060] When the medium frequency retry fails, the third preset period is used to perform data sending, i.e. the period is further expanded to 60 seconds / attempt to perform data sending (5 samples per single sending); if the continuous sending fails, it is determined that the network is unavailable, and the transmission task is actively suspended.

[0061] 4) State reset mechanism

[0062] When the offline data packet in any stage is sent successfully, the system immediately resets to the transmission frequency of the first preset period, i.e. immediately resets to the high frequency exploration state (5 seconds period), and clears the cache queue of the confirmed data.

[0063] 2. Transmission optimization strategy based on time priority and traffic fuse. A time-oriented hierarchical transmission mechanism is established, combined with daily traffic fuse protection rules, to achieve efficient data return and fine resource management. The specific implementation steps are as follows:

[0064] 1) Time priority transmission mechanism

[0065] Suitable for data transmission scheduling steps, the security alarm data in the compressed and lightweight data set stored in the first queue is executed with a time priority mechanism during transmission. The time priority mechanism includes assigning a unique identifier to each alarm event and scheduling data transmission in reverse chronological order (with the most recent date first) as the smallest transmission unit. That is, each independent alarm event is assigned a unique ID (such as "2023-08-20_ collision warning_001"), and when there are multiple alarm events to be transmitted, the transmission queue is sorted by the time of the alarm event from recent to distant, i.e. the event with the latest timestamp is transmitted first, for example, collision warning today is transmitted first, and then device fault alarm yesterday is transmitted. Then, the complete data set associated with the same alarm event ID is executed with atomic transmission (single session completes the full data return of the event), ensuring event context integrity, i.e. all data related to the same alarm event ID (such as warning trigger record, subsequent trajectory data, disposal log) must be: a) packaged as a single data set; b) transmitted in one go (no partial transmission allowed), avoiding incomplete alarm information received by the shore end due to partial transmission (such as only the warning trigger record is missing the subsequent disposal log), ensuring that the latest safety event is prioritized for disposal (such as the most recent collision warning is more important than the oil consumption data last week), and effectively reducing the number of communication handshakes by packaging associated data (single transmission saves more than 30% overhead compared to multiple transmissions).

[0066] 2) Daily traffic quota fuse mechanism

[0067] Suitable for traffic quota monitoring and fuse steps, real-time statistics of consumed traffic during transmission, i.e. real-time monitoring of the cumulative data transmission traffic of all queues per day, and comparing the cumulative data transmission traffic with the preset daily transmission traffic threshold (setting 30MB / day as the system traffic threshold (hardware configurable parameter)), when the cumulative value reaches the threshold, the fuse protection is activated immediately, and the subsequent data transmission of the day is terminated, i.e. if the cumulative data transmission traffic of 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 satellite cost overruns.

[0068] 3) Dynamic bandwidth regulation strategy

[0069] Suitable for flow quota monitoring and fusing steps, if the daily cumulative data transmission flow is less than the preset flow quota threshold, that is, the daily cumulative data transmission flow < 25MB, the system automatically starts the elastic transmission mode; The elastic transmission mode includes extending the transmission data time range, dynamically adjusting the data sending interval, and dynamically adjusting the transmission rate according to the proportion of the remaining flow and the remaining time. Among them,

[0070] Extended transmission data time range: additional sending of offline data in adjacent time windows (T-1 to T-3 days);

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

[0072] Dynamically adjust the transmission rate according to the proportion of the remaining flow and the remaining time (rate adaptive control): the transmission rate is dynamically adjusted according to the following formula:

[0073] Rate = (remaining quota / remaining time) x safety factor (0.6)

[0074] 3, Ship end data time window storage strategy, which can be understood as a pre-optimized processing link of the data transmission scheduling step, used to complete the time-effective hierarchical filtering of data before transmission scheduling. Establish a configurable data time management mechanism, based on the preset storage duration threshold, the offline data is processed hierarchically, the specific implementation steps are as follows:

[0075] 1) Time-effective transmission window constraint

[0076] The system sets the dynamic storage time window threshold (default to retain the last 30 days of data, and supports modification to 15 / 60 days through the configuration file), only the historical data generated within the time window is executed. Ship-shore transmission task, in order to avoid transmission of obsolete data occupying valuable bandwidth, and ensure that the data obtained by the shore center has time value.

[0077] 2) Overdue data localization processing

[0078] Automatic archiving strategy for data beyond the time window: transmission behavior termination: no longer included in the communication scheduling queue, exempt from satellite link sending (that is, no longer consume satellite flow quota), for example, GPS data 31 days ago Stop sending to the shore end;

[0079] Local persistent storage: complete retention to the ship end database, supporting post-tracing query (supporting local review and accident tracing);

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

[0081] 4. Ship offline data transmission constraint strategy. Based on the ship's operating state, network environment and transmission security, a multi-dimensional transmission control mechanism is established, and the specific rules are as follows:

[0082] 1) Ship navigation state constraint, corresponding to the timing decision of the transmission scheduling mechanism of the data transmission scheduling step

[0083] Parse AIS (Automatic Identification System) real-time data stream, activate offline data transmission only when the navigation state is "berthing" (IMO state code = 5), and terminate transmission immediately when the ship's navigation state changes to "navigation".

[0084] 2) Network access type screening, corresponding to the network decision of the transmission scheduling mechanism of the data transmission scheduling step

[0085] Detect the current active network interface type (4G / VSAT / WiFi) through the operating system layer API, start transmission only when connected to 4G mobile network (interface identifier CELLULAR_NETWORK), and automatically freeze the transmission queue when switching to high-cost links such as maritime satellite VSAT (avoid high-cost satellite communication).

[0086] 3) Network quality dynamic evaluation, corresponding to the link decision of the transmission scheduling mechanism of the data transmission scheduling step

[0087] Send 128KB probe packets to the speed measurement server based on TCP / IP protocol, develop (activate) transmission channel when the downlink rate is greater than 1.5Mbps and the uplink delay is less than 800ms, and suspend data transmission within 200ms when the network quality drops below the threshold (i.e. downlink rate less than or equal to 1.5Mbps or uplink delay greater than or equal to 800ms).

[0088] 4) Transmission rate hard flow limiting, corresponding to the flow decision of the transmission scheduling mechanism of the data transmission scheduling step

[0089] Use Token Bucket Algorithm to limit the sending speed to no more than 10kbps, and use Linux TC (Traffic Control) to simulate kernel-level flow control.

[0090] 5) Data packet level transmission control, corresponding to the execution detail decision of the transmission scheduling mechanism of the data transmission scheduling step

[0091] Encapsulate a single data into a TCP packet of less than or equal to 512B (avoid MTU fragmentation), the maximum number of retries for a single packet is 3, and continuous failure is marked as "offline unreachable", and the failed data packet is injected into the offline storage pool (isolated from the subsequent transmission queue).

[0092] 6) Breakpoint resume guarantee mechanism

[0093] Suitable for network monitoring and breakpoint recording steps, a unique sequence number is assigned to each data packet in each queue, and the sequence number of the offline data packet that has not been completed is recorded in the database in a breakpoint resume manner, so as to prevent missing data packets or repeated sending of data packets that have been sent when the software is started next time.

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

[0095] Suitable for breakpoint resume and integrity check steps, a hash check method is used to check the integrity of the data packet for resuming transmission, and 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 file MD5 hash values of the sender and the receiver, it can be verified whether the file remains unchanged during transmission, and it is ensured that the file is not damaged during transmission.

[0096] The application also relates to a flow optimization system for ship-shore offline data transmission under a restricted network, which corresponds to the flow optimization method for ship-shore offline data transmission under a restricted network described above, and can be understood as a system for implementing the method. The system comprises a data acquisition and lightweight processing module, a data compression processing module, a data transmission scheduling module, a flow quota monitoring and fusing module, a network monitoring and breakpoint recording module, and a breakpoint resume and integrity check module connected in sequence. Specifically,

[0097] The data acquisition and lightweight processing module acquires multi-source data including safety alarm data, collision avoidance trajectory data and sensor data at the ship end in real time; the acquired multi-source data is differentiated and pretreated at the ship end, including dynamic frame extraction processing of the sensor data, aggregation processing of the collision avoidance trajectory data into a single batch vector packet, and standardized encoding processing of the safety alarm data, to generate a lightweight data set adapted for ship-shore offline data transmission after the above-mentioned differentiated pretreatment;

[0098] The data compression processing module uses a ZLIB compression engine to compress the differentiated pretreated lightweight data set in real time;

[0099] The data transmission scheduling module constructs a priority layering model including a multi-level queue scheduling mechanism based on security levels, 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 security alarm data in the compressed and processed lightweight data set is stored in the first-level queue and is set as the highest priority for real-time pre-emptive transmission; the collision avoidance trajectory data in the compressed and processed lightweight data set is stored in the second-level queue and is set as the medium priority for time-sensitive aggregated transmission; the sensor data in the compressed and processed lightweight data set is stored in the third-level queue and is set as the lowest priority for transmission at the minimum rate when there is bandwidth redundancy.

[0100] The traffic quota monitoring and fusing module real-time counts the daily cumulative data transmission traffic of all queues from the ship end to the shore end, and compares the cumulative data transmission traffic with a preset daily traffic threshold, if the daily cumulative data transmission traffic reaches the daily traffic threshold, activates the fusing protection and suspends the data transmission of all queues from the ship end to the shore end on the same day.

[0101] The network monitoring and breakpoint recording module real-time monitors the network state, suspends the data transmission of all queues from the ship end to the shore end when an abnormal network state is monitored, records the transmission breakpoint state of each queue at the time of the abnormality, and assigns a unique sequence number to each data packet to be transmitted in each queue, takes the data packets to be transmitted as offline data packets, and records the sequence number of the offline data packets in the database.

[0102] The breakpoint resuming and integrity checking module resumes the transmission of the offline data packets according to the priority order of each queue based on the recorded transmission breakpoint state of each queue and the sequence number of the offline data packets to be transmitted when the network state is recovered, and uses the hash checking method to check the integrity of the offline data packets to be transmitted, the offline data packets that fail the checking are retransmitted in the corresponding priority queue, and the offline data transmission from the ship to the shore under the restricted network is completed after all data packets are successfully checked.

[0103] Preferably, in the breakpoint resuming and integrity checking module, a stepwise backoff retransmission mechanism based on server connection state detection is also established, which includes a high-frequency trial stage, a medium-frequency retry stage, a low-frequency detection stage, and a state reset mechanism; the high-frequency trial stage uses a first preset period to attempt data transmission when the offline data packet transmission fails; the medium-frequency retry stage uses a second preset period to retransmit when the high-frequency trial fails, the second preset period is greater than the first preset period; the low-frequency detection stage uses a third preset period to perform data transmission when the medium-frequency retry fails, the third preset period is greater than the second preset period; the state reset mechanism immediately resets to the transmission frequency of the first preset period when the offline data packet transmission succeeds in any stage.

[0104] Preferably, in the flow quota monitoring and fusing module, if the daily cumulative data transmission flow is less than the preset flow quota threshold, which is less than the daily transmission flow threshold, the elastic transmission mode is automatically started, which includes expanding the time range of transmission data, dynamically adjusting the data sending interval, and dynamically adjusting the transmission rate according to the proportion of the remaining flow and the remaining time.

[0105] And / or, in the data transmission scheduling module, the security alarm data in the compressed and lightweight data set stored in the first queue is executed with the time-sensitive priority mechanism during transmission, which includes assigning a unique identifier to each alarm event, sorting the transmission queue from near to far according to the alarm event occurrence time, and packaging all data associated with the same alarm event as a single data set and performing atomic transmission.

[0106] Preferably, in the network monitoring and breakpoint recording module, after recording the serial number of the offline data packet in the database, the sailing state of the ship is determined according to the real-time AIS data obtained in advance, and the transmission of the offline data packet is terminated immediately when the sailing state is determined to be sailing. When the sailing state 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 yes, a probe data packet is sent to the speed measurement server based on the TCP / IP protocol, the downlink transmission rate and the uplink transmission delay are measured, and the downlink transmission rate and the uplink transmission delay are compared with the corresponding preset threshold values, respectively. When the downlink transmission rate is greater than the preset transmission rate threshold value, and the uplink transmission delay is less than the preset delay time threshold value, the transmission of the offline data packet is activated. When the downlink transmission rate is less than or equal to the preset transmission rate threshold value or the uplink transmission delay is greater than or equal to the preset delay time threshold value, the transmission is suspended.

[0107] The application provides an objective and scientific flow optimization method and system for ship-shore offline data transmission under a restricted network, which performs local data processing and analysis at the ship end, adopts an efficient data compression algorithm, and uses an intelligent data buffering and priority sorting mechanism, thereby greatly reducing the amount of data that needs to be transmitted to the shore end, reducing the cost of satellite communication, improving the bandwidth utilization rate, and ensuring that critical information can be transmitted in a timely and accurate manner. Different types of multi-source data are differentiated and preprocessed to generate a lightweight data set suitable for ship-shore offline data transmission, thereby reducing redundant data; compression techniques are used to further reduce the data volume; and a multi-level queue scheduling mechanism based on security levels is designed to ensure the real-time nature of emergency data and the effectiveness of other data, thereby enhancing the overall efficiency and reliability of data transmission. The application places particular emphasis on the immediate transmission of critical data (such as ship safety alerts), and even in poor network conditions, it can ensure the priority transmission of this information, which is crucial for maintaining the safe navigation of ships. The application 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 above specific embodiments can enable those skilled in the art to more fully understand the present application, but do not limit the present application in any way. Therefore, although the present application has been described in detail with reference to the drawings and examples, those skilled in the art should understand that modifications or equivalent replacements can still be made to the present application, and in general, all technical solutions and improvements that do not deviate from the spirit and scope of the present application should be covered within the protection scope of the present application.

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 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. 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 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. 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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