Mmsi number detection method and system based on frequency of ais message broadcasting

Abstract

The present application relates to ship traffic control system, especially to a kind of MMSI re-number detection method and system based on AIS message broadcasting frequency, the method comprises: continuously receiving AIS dynamic message on time series and parsing to obtain MMSI and message ID;A certain number of dynamic messages are stored for each MMSI;The validity of dynamic message is judged;The time difference of adjacent dynamic message is calculated for valid message, and abnormal value is filtered out;The average value of the time difference retained is calculated, and the arithmetic mean of mean deviation is obtained, if the absolute value of the result is not greater than 26.67ms, it is determined that this MMSI is normal, otherwise it is determined that this MMSI is abnormal and further re-number verification is carried out;The system includes memory and processor, and the processor is used to call and run the instruction from the memory, and the re-number detection method is executed.

Description

TECHNICAL FIELD

[0001] The present application relates to a ship traffic control system, in particular to a MMSI number detection method and system based on AIS message broadcast frequency. BACKGROUND

[0002] AIS (Automatic Identification System) is a system for automatic exchange of information between ships and between ships and shore, and is an important means to improve navigation safety, enhance maritime traffic management and promote shipping efficiency. Maritime Mobile Service Identity (MMSI) is an important part of the AIS system. MMSI is the unique identifier of each ship, through which the ship can transmit real-time position, time information, heading, speed and other important data, thereby improving navigation safety and reducing collision risk. In the event of an emergency, MMSI can speed up emergency response, helping maritime agencies to quickly locate affected ships, and port management agencies and shipping companies to track and dispatch ships, optimizing operational efficiency. In addition, MMSI is also the focus of the International Maritime Organization (IMO) and national regulations.

[0003] In the AIS system, ships are divided into A-class ships and B-class ships. A-class ships broadcast 1, 2, 3 and 5 number messages at a certain frequency, 1, 2 and 3 number messages are dynamic messages, the broadcast interval is shown in Table 1, and 5 number message is a static message, the broadcast interval is 6 minutes. B-class ships broadcast 18 and 24 number messages, 18 number dynamic message broadcast interval is shown in Table 2, and 24 number static message broadcast interval is 6 minutes.

[0004] Table 1 A-class ship message reporting interval

[0005]

[0006] Table 2 B-class ship message reporting interval

[0007]

[0008] The AIS message contains ship MMSI, user ID, time (time mark), position (longitude, latitude) and navigation speed (SOG) and other information. The AIS shore-based system continuously receives all AIS messages, and through the MMSI number and message ID in the message, it can obtain the message transmitted by each ship.

[0009] But in the process of maritime law enforcement, it is often found that the same MMSI appears on two or more ships (the probability of the same MMSI appearing on three or more ships is extremely low), that is, MMSI number duplication phenomenon occurs, which not only increases the risk of ship collision, affects the safety of ship navigation, but also increases the difficulty of maritime emergency rescue and shipping management, therefore, effective detection and timely processing of MMSI number duplication problem need to be solved. SUMMARY

[0010] The technical problem to be solved by the present application is to detect MMSI number duplication based on the frequency of AIS message broadcasting when the same MMSI appears on two ships.

[0011] To solve the above problems, the technical solution adopted by the present application is:

[0012] In the first aspect, the present application provides a MMSI number duplication detection method based on the frequency of AIS message broadcasting, which comprises the following steps:

[0013] S1, continuously receiving AIS dynamic messages in time sequence, and parsing the received dynamic messages to obtain MMSI and message ID;

[0014] S2, storing the received dynamic messages respectively marked by MMSI, and storing N dynamic messages for each MMSI, wherein N is a positive integer;

[0015] S3, reading the dynamic messages stored in S2 marked by MMSI, and judging the validity of the dynamic messages; if the message is invalid, empty the message corresponding to the MMSI and re-store for re-judgment; if the message is valid, continue to the next step of detection;

[0016] S4, calculating the time difference of adjacent dynamic messages , filtering out abnormal , and retaining normal time difference ;

[0017] S5, calculating the average value of the time difference retained in S4 , the arithmetic mean of mean deviation , and the arithmetic mean of mean deviation , if is not greater than 26.67ms, it is determined that the MMSI is normal, otherwise it is determined that the MMSI is abnormal and further number duplication verification is performed.

[0018] Further, in S5, the further number duplication verification method is as follows:

[0019] Retrieve the static message of 10h corresponding to the MMSI and verify it, if the number of static messages is greater than 110, determine that the MMSI is heavy number, otherwise, re-store the message corresponding to the MMSI and re-determine.

[0020] Further, in the S3, the method for judging the validity of the dynamic message is as follows:

[0021] Extract the received signal level carried in each dynamic message VSI statement and calculate the average value thereof If Less than -107dBm, the message is invalid, and it is emptied and re-stored;

[0022] If Not less than -107dBm, determine whether the N dynamic messages contain the No. 3 message, if not, or all are No. 3 messages, the message is valid.

[0023] Further, in the S2, each MMSI stores N dynamic messages, and the N is a positive integer of 100-200.

[0024] Further, in the S4, the abnormal The method is as follows:

[0025] Calculate the interval difference of adjacent messages The average value of If Greater than 1.6 Delete the .

[0026] Further, the MMSI determined as heavy number is reported to the VDL system.

[0027] Further, the MMSI determined as normal is cyclically detected.

[0028] In the second aspect, the application provides an MMSI heavy number detection device based on the broadcasting frequency of AIS message, and the device comprises:

[0029] A dynamic message receiving and analyzing unit is used for continuously receiving AIS dynamic messages in time sequence and analyzing and obtaining MMSI and message ID;

[0030] A dynamic message storage unit is used for storing the received dynamic messages respectively marked by MMSI, and each MMSI stores N dynamic messages, wherein N is a positive integer;

[0031] A message validity judging unit is used for judging the validity of the N dynamic messages corresponding to each MMSI;

[0032] The time difference calculation unit is used to calculate the time difference between adjacent dynamic messages corresponding to each MMSI. Filter out abnormal ones Preserve the normal time difference ;

[0033] The duplicate number detection unit is used to detect the time difference. Calculate the average value and the arithmetic mean of the mean deviation And make a judgment, if If the time is no more than 26.67ms, the MMSI is considered normal; otherwise, the MMSI is considered abnormal and further verification of duplicate numbers is performed.

[0034] Thirdly, the present invention provides an MMSI duplicate number detection system based on AIS message broadcast frequency, the system comprising:

[0035] One or more memories for storing instructions; and

[0036] One or more processors are configured to retrieve and execute the instructions from the memory to perform the method described in the first aspect of the present invention.

[0037] Fourthly, the present invention provides a computer-readable storage medium comprising:

[0038] The method described in the first aspect of the present invention is executed when the program is run by a processor.

[0039] The beneficial effects of adopting the above technical solution are as follows:

[0040] The MMSI duplicate number detection method based on AIS message broadcast frequency provided by this invention can effectively distinguish between normal MMSI and MMSI duplicate numbers of two ships. In particular, the dual mechanism of dynamic message initial judgment and static message verification can ensure the accuracy and reliability of detection.

[0041] By continuously detecting ship messages using the detection method provided by this invention, duplicate MMSI numbers of ships can be identified in real time. MMSI numbers that are determined to be duplicated are reported to the VDL system and then handled by relevant departments, ensuring timely processing of illegal activities.

[0042] By using this invention to detect duplicate MMSI numbers, the risk of MMSI theft can be reduced, the risk of ship collisions caused by duplicate MMSI numbers can be lowered, ship navigation safety can be ensured, and duplicate MMSI numbers can be avoided from affecting maritime emergency search and rescue and shipping management. Attached Figure Description

[0043] Figure 1 This is a flowchart of the detection method of the present invention.

[0044] Figure 2 is a dynamic message validity judgment flow chart.

[0045] Figure 3 is an abnormal MMSI static message verification flow chart.

[0046] Figure 4 is a dynamic message simulation verification result chart in a normal state of MMSI.

[0047] Figure 5 is a dynamic message simulation verification result chart in a two-ship MMSI duplicate number state.

[0048] Figure 6 is a ship static message statistical chart in a normal MMSI state.

[0049] Figure 7 is a ship static message statistical chart in a two-ship MMSI duplicate number state. DETAILED DESCRIPTION

[0050] In order to make the object, technical scheme and advantages of the present application more clear, the present application will be described clearly and completely below in combination with specific embodiments.

[0051] The core technology of the AIS system is the SOTDMA (self-organizing time division multiple access) communication mode. The system divides the time accurately into extremely small units, i.e. time slots. There are 2250 time slots in 1 min, and each time slot is 26.67 ms long. The AIS messages are transmitted in the time slots reserved in advance. The AIS shore-based system receives all the AIS messages continuously, and through the MMSI number in the messages, the transmitted messages of each ship can be obtained. The data tag (Tag Block) carried by the messages contains the receiving time of the messages. Since the AIS signal works in the very high frequency, the receiving time of the messages is synchronized with the transmission time of the messages. Therefore, through the received messages, the transmission time and the transmission interval of the AIS messages of each ship can be obtained.

[0052] When the MMSI of the ship does not have the duplicate number problem and the message loss is not considered, the mean deviation of the transmission interval of the ship messages is around 0 (since the selection of the transmission time slot of the AIS message adopts the reservation mode of SOTDMA, there is a random jitter between the actual transmission time slot and the nominal time slot, and the random jitter conforms to the Gaussian distribution), and the mean value is a fixed value. The value strictly conforms to the transmission interval in Table 1 and Table 2. However, when the same MMSI is repeatedly used in two or more ships, due to the intersection of the ship messages, the mean deviation of the transmission interval is not 0. Therefore, by using this characteristic, the detection of the MMSI duplicate number can be realized. The MMSI duplicate number detection algorithm based on the message transmission interval mainly includes two parts, i.e. the duplicate number detection depending on the dynamic message and the duplicate number verification using the static message.

[0053] refer to Figure 1 As shown, this invention provides a method for detecting duplicate MMSI numbers based on AIS message broadcast frequency. This method addresses the situation where the same MMSI appears on two ships. The method includes the following steps:

[0054] S1. Continuously receive AIS dynamic messages in the time series, parse the received dynamic messages to obtain MMSI and message ID, where message ID is used to indicate the type of message;

[0055] S2. Store the received dynamic messages using MMSI as the identifier. Each MMSI stores N dynamic messages, where N is a positive integer; the value of N is a positive integer ranging from 100 to 200.

[0056] S3. Read the dynamic message stored in S2 using the MMSI as a marker and determine the validity of the dynamic message; if the message is invalid, clear the message corresponding to the MMSI, restore it, and re-determine it; if the message is valid, continue to the next step of detection.

[0057] S4. Calculate the time difference between adjacent dynamic messages. Filter out abnormal ones Preserve the normal time difference ;

[0058] S5. The time difference retained in S4 Calculate the average value and the arithmetic mean of the mean deviation ,if If the time is no more than 26.67ms, the MMSI is considered normal; otherwise, the MMSI is considered abnormal and further verification of duplicate numbers is performed.

[0059] in, ;

[0060] ;

[0061] n is the retention time difference The number of.

[0062] In the AIS system, in order to avoid the problem of message loss due to the instability of the AIS signal received by the base station caused by the geographical environment, equipment electromagnetic interference, signal propagation characteristics and other factors during the ship sailing, and further to cause the inaccuracy of the calculation of the message broadcast interval, therefore, in the process of calculating the message broadcast interval, firstly, the power level of the received message is evaluated, and the average value of the message receiving power level is selected to be not less than -107dBm (-107dBm is the international standard requirement for the sensitivity of the AIS received signal power level); meanwhile, in the actual sailing of the ship, the message broadcast interval is closely related to the ship speed and the ship heading (as shown in Table 1 and Table 2), in order to improve the accuracy of the subsequent calculation of the message broadcast interval, after the message validity is judged, it can be ensured that the selected message sample meets the requirements in terms of signal strength and broadcast rate stability.

[0063] In addition, according to the IEC standard, when the message broadcast interval changes, the ship AIS equipment should first transmit message No. 3 for 1 min, and the change of the message broadcast interval is realized by the increase or decrease of message No. 3. Therefore, by judging whether message No. 3 exists in the received N (100-200) messages, it can be determined whether the broadcast interval is switched during the message storage; in addition, when the ship is in the anchoring state, the message broadcast rate is lower than 1 times / min, and it always broadcasts message No. 3.

[0064] In the S2, N dynamic messages are stored for each MMSI, and since the message broadcast frequency is different, when the message storage count of each MMSI corresponding to the message reaches the set N, or the message storage time reaches 5h, the message reception is stopped, and the MMSI message storage is completed. Wherein, N is 100-200, if the N value is too low, even if the normal ship, one or two message random delay, channel interference or SOTDMA time slot jitter, may cause the average deviation to fluctuate greatly, and it is easy to cause misjudgment (judging the normal ship as a heavy number). At the same time, if the N value is too large, it will increase the storage and processing burden of the method, and at the same time, the change of the sailing speed and the sailing direction in a longer time window is introduced, which may make the judgment of the stability of the message broadcast interval become complex.

[0065] Reference Figure 2 As shown in the MMSI heavy number detection method of the present application, the method for judging the validity of the dynamic message in the S3 is as follows:

[0066] Extract the received signal level carried in the VSI statement of each dynamic message and calculate the average value If is less than -107dBm, the message is invalid, and it is emptied and stored again, that is, the MMSI is re-detected;

[0067] If If the value is not less than -107dBm, then determine whether the N dynamic messages contain message number 3. If message number 3 is not contained, or if all messages are message number 3, then the message is valid, and then proceed to the next step (step S4) for detection.

[0068] In step S4, abnormal values ​​are filtered out. The method is as follows:

[0069] Calculate the interval difference between adjacent messages average ,if Greater than 1.6 , then delete this Specifically, after reading the filtered valid messages from the memory, the time interval between adjacent messages is calculated. ,in, and for all Take the average to get All times are in milliseconds.

[0070] Since the success rate of AIS message broadcasting is actually less than 100%, the message broadcasting interval difference calculated based on the received messages is used as a reference. There may be an anomaly, meaning the message reception failed. Too large. Under normal circumstances, this is an outlier. Normal value The packet loss rate must be at least twice or more than 20%, and the message reception success rate must be no less than 80% (ITU-RM.1371-5 Recommendation (02 / 2014) - Technical characteristics of Automatic Identification Systems for Use in the VHF Maritime Mobile Band). This means the packet loss rate must not exceed 20%. Furthermore, in practice, packet loss is sporadic, with only rare instances of consecutive loss. Therefore, based on the extreme value, taking 100 received messages as an example, when the packet loss rate is 20% and both messages are consecutively lost (two messages each), the following applies:

[0071] ;

[0072] Therefore, in filtering outliers The following judgment is performed: if Then remove this. Otherwise, no action will be taken.

[0073] After outliers After filtering, theoretically, the remaining All values ​​are within the normal range, which is called... Calculate at this time mean and average deviation .

[0074] Reference Figure 3 As shown in the S5, the further verification method of the renumber is as follows:

[0075] The static message of 10h corresponding to the MMSI is called and verified. If the number of static messages is greater than 110, it is determined that the MMSI is renumbered, otherwise the message corresponding to the MMSI is re-stored and re-determined.

[0076] 10h is selected as the observation time window of the static message verification, which is based on the consideration of the extremely low frequency of static message broadcast and the statistical reliability. Whether it is a class A ship or a class B ship, the broadcast interval of the static message (message 5 or message 24) is 6 minutes. In 10h, the number of static messages received in theory is 100, and 100 messages can reliably calculate the average interval (6 minutes) and the total number. If the observation time is too short, any occasional message loss or delay will have a huge impact on the average value. In actual message reception, it is possible that the existence of bit error rate will cause the failure of message reception, so that the number of received messages is lower than the theoretical value, but it is not possible to make the received message higher than the theoretical value of 100. At the same time, considering the fault tolerance of 10%, the threshold value of the number of static messages is set to 110. If the number of static messages is abnormal, it means that the MMSI is indeed renumbered; otherwise, the MMSI renumbering fails, and the data is emptied to re-determine the MMSI.

[0077] Although the normal MMSI, the static message received within 10 hours usually does not exceed 110, and when the MMSIs of two ships are renumbered, the static message received within 10 hours is extremely likely to be much greater than 110. When the last period in the 10 hours of receiving static messages, the MMSI just appears the renumbering phenomenon, there may be static messages less than 110 but actually renumbered and not identified. But in order to save law enforcement resources and avoid rashly reporting the VDL system for law enforcement action, the threshold value of the static message is set to 110. The renumbered MMSI that is missed can be identified in the subsequent renumbering detection.

[0078] Further, the heavy number detection method of the present application reports the MMSI determined as heavy number to the VDL system, and the relevant departments handle it according to the clue. And the MMSI determined as normal is detected in a cycle. That is, the present method receives the messages corresponding to M MMSIs at the same time, and the verification of m (m is less than M) MMSIs can be carried out at the same time in each round of judgment. Assuming that all of the m MMSIs are normal, the remaining MMSIs are continuously detected until all of the MMSIs are detected, and then all of the MMSIs are detected again. If it is determined in the detection that a certain MMSI is heavy, it is immediately reported to the VDL system. If it is determined that the message of a certain MMSI is invalid, or the MMSI is not finally determined as heavy after static message verification, it is immediately re-detected in the next batch of MMSIs to be verified. The MMSIs not determined as heavy are detected in a cycle (or repeatedly), which can continuously monitor whether all MMSIs exist (appear) heavy.

[0079] To verify the effectiveness and accuracy of the "MMSI heavy number detection algorithm based on message broadcasting interval" proposed in this paper, a simulation environment is built using MATLAB R2022b platform. The simulation aims to simulate the real message data stream received by the AIS shore-based system, and evaluate the detection performance of the algorithm under different scenarios.

[0080] For dynamic message verification, if there is no heavy number situation for the MMSI of the ship, the message interval jitter caused by the random time slot reservation of SOTDMA conforms to the Gaussian distribution, and the mean deviation is very small, which is theoretically much smaller than a time slot. When two or more ships alternately broadcast messages, the interval between adjacent messages in the received message stream is mainly determined by the difference in broadcasting time of the two ships, rather than the SOTDMA jitter of a single ship, so that the mean deviation of the message interval increases sharply and exceeds a time slot. Simulation: one ship broadcasts messages at a stable 10s nominal interval when the MMSI is normal, and two ships broadcast messages using the same MMSI when the MMSI is heavy. The simulation results are shown in Figure 4 and Figure 5 .

[0081] It can be seen from Figure 4 that when the MMSI is normal, the deviation of adjacent message interval is around 0, the mean value of the deviation is close to 0, and the absolute value of the arithmetic mean is 5.81ms (less than 26.67ms); as Figure 5 shown, when the MMSI of two ships is heavy, the deviation of adjacent message interval deviates far from 0, and the absolute value of the arithmetic mean is much larger than 26.67ms).

[0082] For the MMSI marked as "suspected duplicate number" in dynamic message detection, the algorithm starts the static message verification process, simulates 10 hours of static message data, and the simulation results are shown in Figure 6 and Figure 7 .

[0083] Referring to Figure 6 , in the normal case, the static message statistics received within 10 hours, the message number (98) and the average interval (6.1 minutes) are within the normal threshold range (the number is less than 110, and the average interval is 5-7 minutes). Referring to Figure 7 , in the case of MMSI duplicate number of two ships, the static message statistics within 10 hours, the message number (195) is far more than the upper limit (110, and the average interval is 3.07 minutes), so that the existence of MMSI duplicate number can be verified.

[0084] The simulation results show that the method described in the application can effectively distinguish between normal and two-ship duplicate MMSI, and especially through the double mechanism of dynamic message preliminary judgment and static message verification, the accuracy and reliability of detection are greatly improved.

[0085] In the second aspect, the application provides an MMSI duplicate number detection device based on AIS message broadcast frequency, which comprises:

[0086] a dynamic message receiving and analyzing unit, configured to continuously receive AIS dynamic messages in time sequence and analyze and obtain MMSI and message ID;

[0087] a dynamic message storage unit, configured to store the received dynamic messages respectively marked by MMSI, and each MMSI stores N dynamic messages, wherein N is a positive integer of 100-200;

[0088] a message validity judgment unit, configured to judge the validity of N dynamic messages corresponding to each MMSI, if the message is invalid, the message corresponding to the MMSI is emptied and re-stored for re-judgment, if the message is valid, the next detection is continued, and the specific method of message validity judgment is described in step S3 of the MMSI duplicate number detection method;

[0089] a time difference calculation unit, configured to calculate the time difference of adjacent dynamic messages corresponding to each MMSI , filter out abnormal , and retain normal time difference , and the judgment and filtering method of abnormal is described in step S4 of the MMSI duplicate number detection method;

[0090] a duplicate number detection unit, configured to detect the retained normal time difference Calculate the average value and the arithmetic mean of the mean deviation Find the absolute value of the expression and make a judgment if... If the delay is no greater than 26.67ms, the MMSI is considered normal; otherwise, the MMSI is considered abnormal and further duplicate number verification is performed. The specific method for further duplicate number verification is as described in step S5 of the MMSI duplicate number detection method of this invention.

[0091] In one example, the unit in the above device may be one or more integrated circuits configured to implement the above methods, such as one or more application-specific integrated circuits (ASICs), or one or more digital signal processors (DSPs), or one or more field-programmable gate arrays (FPGAs), or a combination of at least two of these integrated circuit forms.

[0092] For example, when the units in the device can be implemented through a processing element scheduler, the processing element can be a general-purpose processor, such as a central processing unit (CPU) or other processor capable of calling programs. Alternatively, these units can be integrated together to form a system-on-a-chip (SOC).

[0093] Thirdly, the present invention provides an MMSI duplicate number detection system based on AIS message broadcast frequency, the system comprising:

[0094] One or more memories for storing instructions; and

[0095] One or more processors are configured to call and run the instructions from the memory to execute the MMSI duplicate number detection method based on AIS message broadcast frequency as described in the first aspect of the present invention.

[0096] The processor can be a CPU, a microprocessor, an ASIC, or one or more integrated circuits for controlling the execution of the program of the method for transmitting the feedback information. The memory is used to store necessary program instructions and data. The processor and the memory can be decoupled and arranged on different devices, and connected through wired or wireless means to support the chip system to realize various functions in the above embodiments. Alternatively, the processor and the memory can be coupled on the same device. Optionally, the memory is a storage unit in the chip, such as a register, a cache, etc. The memory can also be a storage unit outside the chip in the terminal, such as a ROM or other type of static storage device that can store static information and instructions, a RAM, etc.

[0097] In a fourth aspect, the present application provides a computer readable storage medium comprising:

[0098] The program, when executed by a processor, performs the MMSI renumbering detection method based on the AIS message broadcast frequency according to the first aspect of the present application.

[0099] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for detecting duplicate MMSI numbers based on AIS message broadcast frequency, characterized in that, Includes the following steps: S1. Continuously receive AIS dynamic messages in the time series, and parse the received dynamic messages to obtain MMSI and message ID; S2. Store the received dynamic messages using MMSI as the identifier. Each MMSI stores N dynamic messages, where N is a positive integer. S3. Read the dynamic message stored in S2 using the MMSI as a marker and determine the validity of the dynamic message; if the message is invalid, clear the message corresponding to the MMSI, restore it, and re-determine it; if the message is valid, continue to the next step of detection. S4. Calculate the time difference between adjacent dynamic messages. Filter out abnormal ones Preserve the normal time difference ; S5. The time difference retained in S4 Calculate the average value and the arithmetic mean of the mean deviation ,if If the delay is no greater than 26.67ms, the MMSI is considered normal; otherwise, the MMSI is considered abnormal and further duplicate number verification is performed. The method for duplicate number verification is as follows: Retrieve the static message corresponding to the abnormal MMSI for verification. If the static message count is abnormal, then the MMSI is determined to be a duplicate number; otherwise, clear the data and re-evaluate the MMSI.

2. The MMSI duplicate number detection method based on AIS message broadcast frequency according to claim 1, characterized in that, In step S5, the method for further verifying duplicate numbers is as follows: Retrieve the 10h static message corresponding to the MMSI and verify it. If the number of static messages is greater than 110, the MMSI is determined to be a duplicate number. Otherwise, the message corresponding to the MMSI is re-stored and re-evaluated.

3. The MMSI duplicate number detection method based on AIS message broadcast frequency according to claim 1, characterized in that, In step S3, the method for determining the validity of dynamic messages is as follows: Extract the received signal level carried in each dynamic message VSI statement and calculate its average value. ,if If the value is less than -107dBm, the message is invalid; clear it and store it again. if If the value is not less than -107dBm, then it is determined whether the N dynamic messages contain message number 3. If message number 3 is not contained, or if all messages are message number 3, then the message is valid.

4. The MMSI duplicate number detection method based on AIS message broadcast frequency according to claim 1, characterized in that, In S2, each MMSI stores N dynamic messages, where N is a positive integer between 100 and 200.

5. The MMSI duplicate number detection method based on AIS message broadcast frequency according to claim 1, characterized in that, In step S4, abnormal values ​​are filtered out. The method is as follows: Calculate the interval difference between adjacent messages average ,if Greater than 1.6 , then delete this .

6. The MMSI duplicate number detection method based on AIS message broadcast frequency according to claim 2, characterized in that, MMSIs identified as duplicates are reported to the VDL system.

7. The MMSI duplicate number detection method based on AIS message broadcast frequency according to claim 1, characterized in that, For MMSIs that are judged to be normal, perform cyclic testing.

8. A device for detecting duplicate MMSI numbers based on AIS message broadcast frequency, characterized in that, include: The dynamic message receiving and parsing unit is used to continuously receive AIS dynamic messages in a time series and parse them to obtain the MMSI and message ID; The dynamic message storage unit stores the received dynamic messages using MMSI as a label. Each MMSI stores N dynamic messages, where N is a positive integer. The message validity judgment unit is used to judge the validity of the N dynamic messages corresponding to each MMSI; The time difference calculation unit is used to calculate the time difference between adjacent dynamic messages corresponding to each MMSI. Filter out abnormal ones Preserve the normal time difference ; The duplicate number detection unit is used to detect the time difference. Calculate the average value and the arithmetic mean of the mean deviation And make a judgment, if If the delay is no greater than 26.67ms, the MMSI is considered normal; otherwise, it is considered abnormal and further duplicate number verification is performed. The duplicate number verification method is as follows: retrieve the static message corresponding to the abnormal MMSI for verification. If the static message count is abnormal, the MMSI is considered a duplicate number; otherwise, clear the data and re-verify the MMSI.

9. A duplicate number detection system for MMSI based on AIS message broadcast frequency, characterized in that, The system includes: One or more memories for storing instructions; and One or more processors are configured to retrieve and execute the instructions from the memory to perform the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes: The program, when run by the processor, executes the method as described in any one of claims 1 to 7.

Images