CN115413050A - Time slot distribution method and system for very high frequency data exchange system - Google Patents

Abstract

The invention discloses a time slot distribution method and a time slot distribution system for a very high frequency data exchange system, wherein the method is suitable for a VDES satellite system and sets a priority level for a ship station terminal; and when the time slot is jammed, the shore station informs the low-priority ship station terminal to quit the occupied time slot and transfer to the high-priority ship station terminal for use according to the priority level of the ship station terminal. The scheme provided by the invention can cause the originally distributed low-priority terminal to abandon the sending message and transfer the message to the high-priority terminal for emergency sending. By the scheme, communication safety and guarantee of sailing of the high-priority ship at sea can be better guaranteed, the occurrence rate of channel blockage of the high-priority terminal is reduced, and the distribution efficiency of channel use is improved.

Description

A VHF data exchange system time slot allocation method and system

technical field

The invention relates to the technical field of satellite communication, in particular to a time slot allocation method system of a VHF data exchange system.

Background technique

The VHF Data Exchange System (VDES) is an enhanced and upgraded version of the Automatic Identification System (AIS), which integrates the existing AIS functions and adds Application-specific messages , ASM) and broadband VHF Data Exchange (VDE) functions, which can effectively relieve the pressure of existing AIS data communication, and satisfy all data transfers between ship-to-ship, ship-to-shore, ship-to-satellite, and shore-to-satellite The need for switching services belongs to the third generation of maritime communication systems.

With the continuous improvement of the demand for data communication on the water, AIS has gradually assumed the task of ship-to-shore data communication. The increase of AIS communication demand in the VHF frequency band has resulted in very crowded frequency bands available to AIS, and many busy ports have reached an occupancy rate of more than 50% of the frequency bands. The 2015 World Radiocommunication Conference (WRC-15) of the International Telecommunication Union decided to introduce the VHF Data Exchange System (VDES) in the field of maritime mobile services. VDES integrates the three functions of AIS, Application Special Message (ASM) and Broadband VHF Data Exchange (VDE). It can comprehensively strengthen the data transmission capability of ship communication by introducing ASM and VDE on the basis of protecting the existing AIS function. .

my country is a big ocean country, and 90% of my country's import and export goods are transported by sea, so the safety and communication of sea traffic are very important. In the process of maritime communication, it is not enough to be satisfied with short-distance communication within a certain range, and the need to establish a communication network of maritime base stations is becoming more and more clear.

In the environment of VDES, because there are few channels in the maritime communication network, there are only 2250 time slots in one minute, so in the communication process, the allocation of time slot channels must adopt the pre-allocation system. That is, under the VDES pre-allocation system, the shore station base station allocates the time slot plan for the next minute through the bulletin board, and broadcasts it to all ships within the range through the bulletin board.

In the prior art, the AIS has 2250 time slots per minute, and each broadcast message occupies 1 time slot. AIS equipment monitors 2250 time slots for 1 minute after it is turned on, looks for a blank time slot and sends after 1 minute, and then occupies this time slot and continues to send. AIS occupies the channel seriously, and it is easy to conflict with other AIS messages.

Like AIS, ASM has 2250 time slots, and after one minute of monitoring, one of the unoccupied time slots is randomly selected and sent. ASM messages are mostly used for functional messages, so the priority of ASM transmission is lower than that of AIS. When a device needs to send both AIS and ASM, it will send AIS messages first.

VDES has 30 units per minute, each unit is 2 seconds, and there are 75 time slots (Slot). Each time division multiple access (TDMA) bulletin board includes 90 time slots, and the 90 time slots are distributed in 6 different channels, and each channel uses 15 time slots. Every 6 time slots form a hex slot (Hex Slot), a hex slot means that each channel is used once, and a total of 375 hex slots are included in one minute. A billboard occupies 15 six-slots, or 90 slots. In one minute, there are a total of 25 bulletin boards. The total number of time slots per minute of VDES is the same as that of AIS, both are 2250 time slots, but VDES channels will use different channels to work separately, which greatly avoids channel congestion and occupation problems. Refer to FIG. 1 for details, which is a TDMA time slot allocation diagram.

At present, the AIS channel is very seriously occupied. Although the AIS equipment will monitor for one minute, once the AIS equipment is working, it will no longer monitor. Therefore, two ships meeting on the sea may block each other due to the use of the same channel, resulting in AIS messages. Unable to interact normally. Currently, pre-allocated channels cannot be modified or used.

The time slot channel allocation of maritime communication adopts the pre-allocation system, and the bulletin board is set up one minute in advance to arrange the time slot allocation for the next minute. Therefore, when a burst occurs, the time slot will be occupied. This will cause higher priority ships to be limited by lower priority ships, affecting normal work.

When there is a higher-priority business, if the low-priority business has already occupied the time slot, the high-priority business cannot use the time slot and will be forced to postpone it until the next minute or even later. This solution affects the work of high-priority services and high-priority terminals.

Contents of the invention

The invention provides a method and system for allocating time slots in a VHF data exchange system, which can ensure that high-authority users successfully use emergency time slot resources in an emergency state.

According to one aspect of the present invention, a VHF data exchange system time slot allocation method is provided, comprising the following steps:

Set the priority level of the ship station terminal;

When the time slot is congested, the shore station will notify the low priority ship station terminal to exit the occupied time slot and transfer it to the high priority ship station terminal according to the priority level of the ship station terminal.

Said setting the priority level of the ship station terminal includes:

Set the priority level of the ship station terminal according to the importance of the ship station terminal; or set the priority level of the ship station terminal according to the importance of the data sent by the ship station terminal;

The priority level of the ship station terminal can be adjusted according to the importance of the ship station terminal itself or the importance of the data to be sent.

Said notifying the low-priority ship station terminal to exit the occupied time slot and transfer it to the high-priority ship station terminal for use, including:

When the high-priority ship station terminal needs to use the time slot urgently when the time slot is congested, the shore station determines that the current low-priority ship station gives up the occupied time slot, and gives up the time slot to the high-priority ship station.

Said notifying the low-priority ship station terminal to transfer the occupied time slot to the high-priority ship station terminal for use, including:

The shore station receives the data request sent by the terminal of the high-priority ship station, and analyzes the congestion degree of the time slot;

When it is determined that the current time slot is congested, send an exit time slot message to the selected low priority ship station terminal; and after receiving the confirmation character ACK sent by the low priority ship station terminal, send the message to the high priority ship station terminal The station terminal sends the use time slot message;

After receiving the used timeslot message, the high-priority ship station terminal uses the timeslot to send data.

The shore station determines the number of low-priority ship-station terminals that need to exit the occupied time slot according to the number of high-priority ship-station terminals.

According to the priority levels of all current ship station terminals, the shore station preferentially selects the lowest priority ship station terminal to exit the occupied time slot; or randomly selects a low priority ship station terminal to exit the occupied time slot.

When no congestion occurs in the current time slot, the shore station notifies the high-priority ship station terminal to randomly select a time slot to send data.

According to another aspect of the present invention, a VHF data exchange system time slot allocation system is provided, comprising:

The priority setting unit is used to set the priority level of the ship station terminal;

The message sending and receiving unit is used for when the time slot is congested, the shore station notifies the low priority ship station terminal to exit the occupied time slot and transfer it to the high priority ship station terminal for use according to the priority level of the ship station terminal.

The system also includes:

The bulletin board unit is used to generate bulletin boards and send them to all ship station terminals;

The congestion determining unit is configured to determine the current time slot congestion degree.

The message sending and receiving unit is specifically used for:

Send an exit time slot message to the selected low-priority ship station terminal;

After receiving the acknowledgment character ACK sent by the low-priority ship station terminal, the used time slot message is sent to the high-priority ship station terminal.

By adopting the technical solution of the present invention, a VHF data exchange system time slot allocation scheme is proposed, which is applicable to the VDES satellite system, and the priority level is set for the ship station terminal; The priority level of the station terminal, notify the low priority ship station terminal to exit the occupied time slot and transfer it to the high priority ship station terminal for use.

In the solution proposed by the present invention, by adding specific messages to the RA and AS channels, the originally assigned low-priority terminals can give up sending messages and transfer them to high-priority terminal equipment for emergency transmission. Through this solution, the communication safety and guarantee of high-priority ships navigating at sea can be better guaranteed, the occurrence rate of channel congestion of high-priority terminals can be reduced, and the allocation efficiency of channel usage can be improved.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the schematic diagram of existing TDMA time slot allocation;

Fig. 2 is the principle flowchart of the time slot allocation method of the VHF data exchange system in the embodiment of the present invention;

Fig. 3 is a schematic structural diagram of the time slot allocation system of the VHF data exchange system in the embodiment of the present invention.

Detailed ways

The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

In fact, as shown in FIG. 1 , each TDMA bulletin board contains 90 time slots, and the 90 time slots are distributed in 6 different channels, and each channel uses 15 time slots. Every 6 time slots form a hex slot (Hex Slot), a hex slot means that each channel is used once, and a total of 375 hex slots are included in one minute. A billboard occupies 15 six-slots, or 90 slots. In one minute, there are a total of 25 bulletin boards. The total number of time slots per minute of VDES is the same as that of AIS, both are 2250 time slots, but VDES channels will use different channels to work separately, which greatly avoids channel congestion and occupation problems.

In various embodiments of the present invention, a method for dynamically allocating VDES time slot resources based on a priority strategy is proposed. On top of the VDES-based system, this method adds a method that allows high-priority terminals to urgently use resources that have been allocated to low-priority terminals. The scheme of time slot resources for priority terminals and the suspension of non-emergency resources for low priority terminals. Through this solution, it can be guaranteed that high-privileged users can successfully use emergency time slot resources in an emergency state.

Fig. 2 is a flow chart of time slot allocation in the VHF data switching system in Embodiment 1 of the present invention. As shown in Figure 2, the time slot allocation process of the VHF data exchange system includes the following steps:

Step 101, setting priority levels for ship station terminals.

In one embodiment of the present invention, the priority level of the ship station terminal is set according to the importance of the ship station terminal; or the priority level of the ship station terminal is set according to the importance of the data sent by the ship station terminal;

The priority level of the ship station terminal can be adjusted according to the importance of the ship station terminal itself or the importance of the data to be sent.

In one embodiment of the present invention, on the basis of the conventional VDES transmission mechanism, a new type of message is added to the RA and AS channels of the bulletin board. The message can stop the message of the low-priority terminal, and transfer the time slot occupied by the low-priority terminal to the high-priority terminal. In order to achieve the release of time slots, to ensure the normal transmission and time slot occupancy of emergency functions.

After the shore station generates the bulletin board, high-priority terminals will also receive the bulletin board.

Step 102, when the time slot is congested, the shore station notifies the low priority ship station terminal to exit the occupied time slot and transfer it to the high priority ship station terminal according to the priority level of the ship station terminal.

In one embodiment of the present invention, when the high-priority ship station terminal needs to use the time slot urgently when the time slot is congested, the shore station determines that the current low-priority ship station gives up the occupied time slot, and gives up the time slot to all Said high priority ship station use.

In one embodiment of the present invention, the shore station receives a data request sent by a high-priority ship station terminal, and analyzes the congestion degree of the time slot;

When it is determined that the current time slot is congested, send an exit time slot message to the selected low-priority ship station terminal; and after receiving the acknowledgment character (Acknowledge character, ACK) sent by the low-priority ship station terminal, The high priority ship station terminal sends the used time slot message;

After receiving the used timeslot message, the high-priority ship station terminal uses the timeslot to send data.

In an embodiment of the present invention, the shore station determines the number of low-priority ship-station terminals that need to exit the occupied time slot according to the number of high-priority ship-station terminals.

According to the priority level of all current ship station terminals, the shore station will give priority to selecting the lowest priority ship station terminal to exit the occupied time slot; or randomly select the low priority ship station terminal to exit the occupied time slot.

When no congestion occurs in the current time slot, the shore station notifies the high-priority ship station terminal to randomly select a time slot to send data.

Specifically, the embodiment of the present invention proposes a method for dynamically allocating VDES time slot resources based on a priority policy. On the basis of the conventional VDES transmission mechanism, a new type of message is added to the RA and AS channels of the bulletin board . The message can stop the message of the low-priority terminal, and transfer the time slot occupied by the low-priority terminal to the high-priority terminal. In order to achieve the release of time slots, to ensure the normal transmission and time slot occupancy of emergency functions.

After the shore station generates the bulletin board, high-priority terminals will also receive the bulletin board.

When a high-priority terminal needs to use time slot resources urgently, it will send an instruction to the shore station. After analyzing the congestion degree of the time slot, the shore station will decide whether to give up sending and vacate the time slot according to the congestion situation of the time slot.

If the time slot is unobstructed, the shore station will send an instruction to the terminal to directly arrange the time slot and send it.

If the time slot occupancy rate is high and the time slot congestion is serious, the current time slot is relatively congested, and the shore station needs to designate the low priority terminal to give up the transmission of the time slot and transfer the time slot to the high priority terminal for use.

The shore station needs to send two different messages. One is sent to terminals with low priority but originally occupied time slots, and the other is sent to terminals with high priority but not originally allocated time slots. The message format of this command is:

! VEVSW,x,xxxxxxxxx,xxxx,x*xx

! VEVSW is a fixed header

The x after the first comma represents an instruction, 0 means stop sending and give up the time slot, 1 means start sending and use the time slot.

After the second comma is the MMSI of the ship, usually 9 digits.

The third comma is followed by a time slot.

The fourth comma is followed by zero padding, usually one of 0, 2, and 4.

The asterisk is followed by a check code, which is calculated by the CRC algorithm.

Sample message: ! VEVSW,0,111222333,1024,0*4A

It means that the ship whose MMSI is 111222333 will give up the time slot No. 1024 of the current minute. After giving up the time slot, the ship needs to return an ACK to the shore station to tell the shore station that it has received it and agree to give up the time slot.

The message format of the ACK is:

! VEVSA,xxxxxxxxx,xxxx,x*xx

in,! VEVSA is a fixed header

After the first comma is the MMSI of the ship, usually 9 digits

The second comma is followed by a time slot.

After the third comma is zero padding, usually one of 0, 2, 4.

The asterisk is followed by a check code, which is calculated by the CRC algorithm.

Sample message: ! VEVSA,111222333,1024,2*3F

On behalf of the ship whose MMSI is 111222333, after receiving the command to relinquish the time slot, the same relinquishment time slot is the 1024th time slot, and stop sending at the 1024th time slot of the next minute.

After receiving the ACK returned by the low-priority ship, the shore station will send a message to the high-priority ship that needs to occupy the time slot. The message is also ! VEVSW message, the difference is that the value after the first comma is 1, which means that the high priority ship can use the time slot.

When there are α high-priority terminals that need to send urgently, and the number of remaining channels is β, then α-β low-priority terminals need to give up time slots. The shore station will randomly find α-β low-priority terminals, and send messages that need to give up time slots to the corresponding terminals.

If there are still γ high-priority terminals that have not been assigned time slots, the shore station will continue to request γ low-priority terminals to give up time slots, and so on, until all high-priority terminals are allocated available time slots.

In order to realize the above process, the technical solution of the present invention also provides a VHF data exchange system time slot allocation system, as shown in Figure 3, the VHF data exchange system time slot allocation system includes:

The priority setting unit 21 is used to set the priority level of the ship station terminal;

The message sending and receiving unit 22 is used for notifying the low priority ship station terminal to exit the occupied time slot and transfer it to the high priority ship station terminal according to the priority level of the ship station terminal when the time slot is congested.

The system also includes:

The bulletin board unit 23 is used to generate a bulletin board and send it to all ship station terminals;

The congestion determination unit 24 is configured to determine the current time slot congestion degree.

The message sending and receiving unit 22 is specifically used for:

Send an exit time slot message to the selected low-priority ship station terminal;

After receiving the acknowledgment character ACK sent by the low-priority ship station terminal, the used time slot message is sent to the high-priority ship station terminal.

In summary, the technical solution of the present invention proposes a VHF data exchange system time slot allocation scheme, which is applicable to the VDES satellite system, and sets the priority level of the ship station terminal; when the time slot is congested, the shore station According to the priority level of the ship station terminal, notify the ship station terminal with low priority to exit the occupied time slot and transfer it to the ship station terminal with high priority for use.

In the solution proposed by the present invention, by adding specific messages to the RA and AS channels, the originally assigned low-priority terminals can give up sending messages and transfer them to high-priority terminal equipment for emergency transmission. Through this solution, the communication safety and guarantee of high-priority ships navigating at sea can be better guaranteed, the occurrence rate of channel congestion of high-priority terminals can be reduced, and the allocation efficiency of channel usage can be improved.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, systems, or computer program products. Accordingly, the present invention can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (10)

1. A VHF data exchange system time slot allocation method is characterized in that, comprising the following steps: Set the priority level of the ship station terminal; When the time slot is congested, the shore station will notify the low priority ship station terminal to exit the occupied time slot and transfer it to the high priority ship station terminal according to the priority level of the ship station terminal. 2. a kind of VHF data exchange system time slot allocation method according to claim 1, is characterized in that, described ship station terminal setting priority level comprises: Set the priority level of the ship station terminal according to the importance of the ship station terminal; or set the priority level of the ship station terminal according to the importance of the data sent by the ship station terminal; The priority level of the ship station terminal can be adjusted according to the importance of the ship station terminal itself or the importance of the data to be sent. 3. A method for allocating time slots of a VHF data exchange system according to claim 1, characterized in that, said low-priority ship station terminal is notified to withdraw from the occupied time slot and transfer it to a high-priority ship station terminal for use ,include: When the high-priority ship station terminal needs to use the time slot urgently when the time slot is congested, the shore station determines that the current low-priority ship station gives up the occupied time slot, and gives up the time slot to the high-priority ship station. 4. A method for allocating time slots of a VHF data exchange system according to claim 1, wherein the notifying the low-priority ship station terminal transfers the occupied time slot to the high-priority ship station terminal for use, include: The shore station receives the data request sent by the terminal of the high-priority ship station, and analyzes the congestion degree of the time slot; When it is determined that the current time slot is congested, send an exit time slot message to the selected low priority ship station terminal; and after receiving the confirmation character ACK sent by the low priority ship station terminal, send the message to the high priority ship station terminal The station terminal sends the use time slot message; After receiving the used timeslot message, the high-priority ship station terminal uses the timeslot to send data. 5. a kind of VHF data exchange system time slot allocation method according to claim 1, is characterized in that, described method also comprises: The shore station determines the number of low-priority ship-station terminals that need to exit the occupied time slot according to the number of high-priority ship-station terminals. 6. a kind of VHF data exchange system time slot allocation method according to claim 1, is characterized in that, described method also comprises: According to the priority levels of all current ship station terminals, the shore station preferentially selects the lowest priority ship station terminal to exit the occupied time slot; or randomly selects a low priority ship station terminal to exit the occupied time slot. 7. a kind of VHF data exchange system time slot allocation method according to claim 1, is characterized in that, described method also comprises: When no congestion occurs in the current time slot, the shore station notifies the high-priority ship station terminal to randomly select a time slot to send data. 8. A VHF data exchange system time slot allocation system, characterized in that it comprises: The priority setting unit is used to set the priority level of the ship station terminal; The message sending and receiving unit is used for when the time slot is congested, the shore station notifies the low priority ship station terminal to exit the occupied time slot and transfer it to the high priority ship station terminal for use according to the priority level of the ship station terminal. 9. a kind of VHF data exchange system time slot allocation system according to claim 8, is characterized in that, described system also comprises: The bulletin board unit is used to generate bulletin boards and send them to all ship station terminals; The congestion determining unit is configured to determine the current time slot congestion degree. 10. A kind of VHF data exchange system time slot assignment system according to claim 8, is characterized in that, described message sending and receiving unit is specifically used for: Send an exit time slot message to the selected low-priority ship station terminal; After receiving the acknowledgment character ACK sent by the low-priority ship station terminal, the used time slot message is sent to the high-priority ship station terminal.

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