An Implementation Method of the MAC Layer of the VDLM2 Airborne Radio

Abstract

The present invention discloses a method for implementing the MAC layer of a VDLM2 airborne radio. In the case where the hardware is not implemented, a simulation system can be simulated. After the hardware is implemented, only the debugging of the interface needs to be completed to implement the MAC layer function of a set of VDLM2 radios. The flexibility and scalability of the implementation of the VDLM2 radio are improved. It has flexibility and scalability, and can use software to simulate and perform function and performance tests on the VDLM2 airborne radio without hardware conditions. In addition, the P-CSMA algorithm is optimized to make the parameter probability p adapt to the signal environment, reduce the probability of signal collision and transmission delay of each aircraft, and improve the throughput of system data transmission.

Description

Technical Field

[0001] The present invention relates to the field of aviation very high frequency (VHF) data transmission, and particularly to a method for implementing the MAC layer of a VDLM2 airborne radio station. Background Art

[0002] Civil aviation data links are mainly divided into three types of communication methods: high frequency (HF), very high frequency (VHF), and satellite communication. Among them, the VHF data link is the most commonly used civil aviation data link communication method globally. In the VHF data link, the current ACARC mode is the most widely used. However, with the continuous and rapid growth of the global civil aviation passenger volume every year, the current civil data link communication system based on ACARC can no longer fully meet the needs of the growth of air traffic flow and the expansion of the speed and range of new aircraft. To meet the development needs of air traffic management, the International Civil Aviation Organization has proposed a new navigation system for establishing an aviation telecommunications network, and the VDL Mode 2 data link has been recognized as the mainstream ground-air data link for the transition to the ATN. However, at present, this method remains at the network simulation stage, mostly theoretical research, which only has certain guiding significance for the early stage of product and system development. It is significantly difficult in the later stage of product implementation and engineering conversion. If directly implemented in hardware, the R & D cycle is long, and the flexibility and scalability are poor during the engineering implementation process. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for implementing the MAC layer of a VDLM2 airborne radio station. Without hardware implementation, a simulation system of the MAC layer is simulated. When the hardware is implemented, only the debugging of the interface needs to be completed to implement the MAC layer function of a VDLM2 radio station. It improves the flexibility and scalability of the implementation of the VDLM2 radio station and is of great significance for the further development and implementation of the VDLM2 radio station.

[0004] The present invention is achieved by the following technical solutions:

[0005] A method for implementing the MAC layer of a VDLM2 airborne radio station, including setting an ARM module, a receiver, and a transmitter in the MAC layer; the receiver is used to receive the data transmitted from the ground station in the uplink, and it includes an uplink data receiving module, a first uplink data processing module, a second uplink data processing module, a third uplink data processing module, and an uplink data sending module; the transmitter is used to receive the data transmitted to the ground station in the downlink, and it includes a downlink data receiving module, a first downlink data processing module, a second downlink data processing module, a third downlink data processing module, and a downlink data sending module.

[0006] As an alternative, the MAC layer is set in the airborne radio, and the airborne radio is connected to the airborne communication management unit, which transmits the airborne communication primitive data through the ARINC429 bus connection; among them, the airborne radio is also provided with a physical layer, and the physical layer realizes signal processing of the VDML2 radio through the FPGA module, and the ARM module is used for data transmission of the VDML2 radio in the MAC.

[0007] As an alternative, the uplink data receiving module is used to receive the physical layer data after being processed by the FPGA module and save it in the buffer; the uplink data sending module is used to send the ARINC 429 data after being processed by the uplink data to the airborne communication management unit.

[0008] As an alternative, the uplink data processing is sequentially processed by the first uplink data processing module, the second uplink data processing module, and the third uplink data processing module, and it includes the following steps:

[0009] The first uplink data processing module parses the data in the receive buffer according to the privately defined serial port format, assembles it into the original AVLC frame; then performs bit stuffing removal on the original AVLC frame; then decomposes it according to the frame flag FLAG into single AVLC frames; finally performs FCS frame checksum and address filtering on the single AVLC frames, and saves the frames that pass the checksum and address filtering in the AVLC frame buffer;

[0010] The second uplink data processing module performs protocol analysis on the data in the AVLC frame buffer, and adds a primitive header according to the ARINC 750 protocol standard to generate different types of primitive data;

[0011] The third uplink data processing module is used to perform 429 data format encoding operations on different types of primitive data, encode the primitive data of different lengths and different types into a unified 32-bit ARINC 429 data format, and then transmit it to the uplink data sending module.

[0012] As an alternative, the downlink data receiving module is used to receive the ARINC 429 data sent from the airborne communication management unit; the downlink data sending module is used to send the AVLC frame data to the FPGA, and then the FPGA converts the data signal into a radio frequency signal and sends it through the antenna.

[0013] As an alternative, the downlink data processing is sequentially processed by the first downlink data processing module, the second downlink data processing module, and the third downlink data processing module, and it includes the following steps:

[0014] The first downlink data processing module performs decoding operations on the ARIN 429 data, and decodes the ARINC429 data into primitive data;

[0015] The second downlink data processing module decodes the primitive data according to the ARINC 750 protocol, and determines whether it is a control primitive. If it is a control primitive, the control state is changed; if it is a data primitive, it is converted into a single AVLC frame, and the FCS check value, bit stuffing, and frame flag are added; and it is saved in the transmit buffer.

[0016] The third downlink data processing module is used for maintaining the MAC layer state machine and implementing the P-persistent carrier sense detection algorithm.

[0017] As an optional method, the MAC layer is also used to control the access to the very high frequency channel; it also includes:

[0018] Timer T1, timer T2, counter M1;

[0019] The signal transmission interval of timer T1 is TM1. When the channel is idle, it detects whether there is buffered data in the buffer. If so, timer T1 is started; when the channel is busy, timer T1 is turned off.

[0020] After timer T2 receives a transmission request, its maximum waiting time is TM2; when the MAC layer receives a transmission request, timer T2 is started, and timer T2 is turned off after a transmission is completed.

[0021] Counter M1 has a maximum access count M1. Counter M1 accumulates the count after each access attempt fails. When the count accumulates to the maximum access count M1, it detects the channel idle situation, and immediately performs transmission when the channel is detected to be idle.

[0022] As an optional method, the signal transmission interval of timer T1 is TM1. When the channel is idle, it detects whether there is buffered data in the buffer. If so, timer T1 is started; when the channel is busy, timer T1 is turned off.

[0023] After timer T2 receives a transmission request, its maximum waiting time is TM2; when the MAC layer receives a transmission request, timer T2 is started, and timer T2 is turned off after a transmission is completed.

[0024] Counter M1 has a maximum access count M1. Counter M1 accumulates the count after each access attempt fails. When the count accumulates to the maximum access count M1, it detects the channel idle situation, and immediately performs transmission when the channel is detected to be idle.

[0025] As an alternative, after the time of timer T2 expires, the external on-board communication management unit is notified of the current channel congestion, and a new operating frequency is searched for; moreover, the recorded count of counter M1 is cleared after system initialization, when the T2 timer expires, or when an access attempt is successful.

[0026] As an alternative, the maximum number of accesses M1 = [log(1 - v) / log(1 - p)];

[0027] where v is the cumulative probability; and p is the probability of successful data transmission in any single signal transmission attempt.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] A method for implementing the MAC layer of a VDLM2 on-board radio provided by the present invention is flexible and scalable, and can be used to simulate and perform function and performance tests on the VDLM2 on-board radio in a software manner without the need for hardware conditions. By controlling the access and use of the very high frequency (VHF) channel, the parameter probability p is adapted to the signal environment, reducing the probability of signal collisions and transmission delays between aircraft, and improving the throughput of system data transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and should not be considered as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0031] Figure 1 is a schematic diagram of an on-board radio simulation system provided by an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of a method for receiving / transmitting the MAC layer of a VDLM2 on-board radio provided by an embodiment of the present invention;

[0033] Figure 3 is a schematic diagram of a method for controlling the very high frequency (VHF) channel of an on-board radio based on P-persistent CSMA provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an all-hardware embodiment, an all-software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0035] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0036] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0037] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0038] Those of ordinary skill in the art can understand that all or part of the steps in implementing the above-mentioned facts and methods can be completed by instructing relevant hardware through a program. The program involved or the said program can be stored in a computer-readable storage medium. When the program is executed, it includes the following steps: At this time, the corresponding method steps are introduced. The storage medium can be ROM / RAM, magnetic disk, optical disk, etc.

[0039] Embodiment

[0040] The VDL Mode 2 data link is the mainstream ground-air data link for the transition to ATN. VDLM2 uses a half-duplex working mode. Due to the complexity of the protocol stack, the current research on VDLM2 mainly adopts network simulation methods. In view of this, this embodiment provides a VDLM2 airborne VDR radio MAC layer simulation system and method, which can effectively shorten the product development cycle of the VLDM2 radio, and at the same time optimize the P-CSMA algorithm, reduce the probability of signal collision and transmission delay of each aircraft, and improve the system throughput.

[0041] In VHF communication, the MAC layer has 4 states: idle state, busy state, ready-to-send state, and waiting state. When the MAC layer is in the idle state, if it detects that the channel is occupied, it enters the busy state. If there is data to be transmitted and the channel is idle, it enters the ready-to-send state. When the MAC layer is in the busy state, if it detects that the channel is idle, it enters the idle state. If there is data to be transmitted, it enters the waiting state. When the MAC layer is in the waiting state, if it detects that the channel becomes idle, it enters the ready-to-send state. When the MAC layer is in the ready-to-send state, if the data transmission is completed and the channel is idle, it enters the idle state. If there is data to be transmitted and the channel is occupied, it enters the waiting state. The MAC layer of this embodiment adopts the P-persistent CSMA algorithm to control the access and use of the VHF channel, aiming to enable all aircraft in the VDLM2 system to share the VHF channel resources of the ground station, reduce the probability of signal collision and transmission delay of each aircraft, and improve the throughput of system data transmission. This embodiment is implemented as follows:

[0042] Please refer to Figures 1 - 3, this embodiment provides a method for implementing the MAC layer of a VDLM2 airborne radio, including setting an ARM module, a receiver, and a transmitter in the MAC layer; the receiver is used to receive the data transmitted from the ground station in the uplink, and it includes an uplink data receiving module, a first uplink data processing module (uplink data processing module 1), (uplink data processing module 2), a third uplink data processing module (uplink data processing module 3), and an uplink data sending module; the transmitter is used to receive the data transmitted to the ground station in the downlink, and it includes a downlink data receiving module, a first downlink data processing module (downlink data processing module 1), a second downlink data processing module (downlink data processing module 2), a third downlink data processing module (downlink data processing module 3), and a downlink data sending module. Among them, the MAC layer is set in the airborne radio (CDR), and the airborne radio is connected to an airborne communication management unit (CMU), and they perform the transmission of airborne communication primitive data through the ARINC429 bus connection; among them, the airborne radio is also provided with a physical layer, and the physical layer realizes the signal processing of the VDML2 radio through the FPGA module, and the ARM module is used to perform data transmission on the VDML2 radio in the MAC.

[0043] In the uplink process, the uplink data receiving module is used to receive the physical layer data processed by the FPGA module and save it in the buffer; the uplink data sending module is used to send the ARINC 429 data after uplink data processing to the airborne communication management unit. The uplink data processing is sequentially processed by the first uplink data processing module, the second uplink data processing module, and the third uplink data processing module, and it includes the following steps:

[0044] The first uplink data processing module parses the data in the receive buffer according to the privately defined serial port format, assembles it into the original AVLC frame; then performs bit stuffing removal on the original AVLC frame; then decomposes it according to the frame flag FLAG into single AVLC frames; finally performs FCS frame checksum and address filtering on the single AVLC frames, and saves the frames that pass the checksum and address filtering in the AVLC frame buffer;

[0045] The second uplink data processing module performs protocol analysis on the data in the AVLC frame buffer, and adds a primitive header according to the ARINC 750 protocol standard to generate different types of primitive data;

[0046] The third uplink data processing module is used to perform 429 data format encoding operations on different types of primitive data, encode the primitive data of different lengths and different types into a unified 32-bit ARINC 429 data format, and then transmit it to the uplink data sending module.

[0047] During the downlink process, the downlink data receiving module is used to receive ARINC429 data sent by the airborne communication management unit; the downlink data sending module is used to send AVLC frame data to the FPGA, and then the FPGA converts the data signal into a radio frequency signal and sends it through the antenna. The downlink data processing is sequentially processed by the first downlink data processing module, the second downlink data processing module, and the third downlink data processing module, and it includes the following steps:

[0048] The first downlink data processing module decodes the ARIN 429 data and decodes the ARINC 429 data into primitive data; the decoding process is as follows: judge the SAL bit of the received 32-bit ARINC 429 data, the SAL position is bit1 to bit8, when the SAL value is 172 and 270, it means that the received is the CMU periodic primitive, and it is directly handed over to the periodic primitive processing function for processing; when the SAL value is 250, 251, 252, 253, it means that the received is the CMU data type primitive, and it is classified and processed according to the ARINC429 data type. Finally, the complete CMU primitive is obtained.

[0049] The second downlink data processing module decodes the primitive data according to the ARINC 750 protocol and judges whether it is a control primitive. If it is a control primitive, the control state is changed; if it is a data primitive, it is converted into a single AVLC frame, and the FCS check value, bit filling and frame flag are added; and it is saved in the send buffer; the third downlink data processing module is used to maintain the MAC layer state machine and implement the P-persistent carrier sense detection algorithm.

[0050] In addition, this embodiment also optimizes the P-CSMA algorithm. The access to the very high frequency channel is controlled through the MAC layer. In the MAC layer, the signal transmission interval of the timer T1 is TM1. When the channel is idle, it detects whether there is buffered data in the buffer. If so, the timer T1 is started; when the channel is busy, the timer T1 is turned off.

[0051] After the timer T2 receives the request to be transmitted, its maximum waiting time is TM2; when the MAC layer receives a transmission request, the timer T2 is started, and the timer T2 is turned off after a transmission is completed; and when the time of the timer T2 expires, it notifies the airborne communication management unit that the current channel is congested and re-searches for the operating frequency.

[0052] The counter M1 has a maximum access count M1. The counter M1 increments its count after each failed access attempt. When the count accumulates to the maximum access count M1, it checks the channel idle condition and immediately transmits when the channel is detected to be idle. Also, the recorded count of counter M1 is cleared after system initialization, when the T2 timer expires, or when an access attempt is successful. M1 can be obtained by M1 = [log(1 - v) / log(1 - p)], and the default value of the cumulative probability v is 0.999. The probability P (0 ≤ P ≤ 1): refers to the probability of successful data transmission in any single signal transmission attempt.

[0053] When there is data to be sent in the transmit queue, the MAC layer requests the channel. If the physical channel is idle, the MAC layer calculates the transmit probability parameter p0. If the calculated result p0 is less than the persistence parameter p, the MAC sublayer notifies the transmit queue to send immediately; otherwise, the MAC layer starts timer T1 and delays for TM1 time (TM1 is a MAC layer parameter), recalculates the transmit probability p0, and this process repeats until the value of p0 is less than the persistence parameter p or the number of repetitions exceeds the maximum number of access attempts M1; when the number of transmissions exceeds M1, the MAC sublayer no longer calculates the value of p0 but immediately notifies the transmit queue to send immediately; additionally, if the physical channel becomes busy during the startup of timer T1, timer T1 is turned off, and when the physical channel returns to idle, timer T1 is restarted; to avoid the physical channel being busy for a long time and preventing the transmit queue from sending data, the MAC layer uses timer T2 (default value is TM2). When the timer exceeds TM2 time, the MAC layer considers the physical channel to be congested and unavailable and notifies CMU of this situation.

[0054] Please refer to again Figure 3 , which shows as an example that the MAC layer attempts 5 times continuously with the initialization parameter probability p and fails each time. Then the channel starts to be busy, at which time timer T1 is turned off. After some time, the channel becomes idle, at which time timer T1 is turned on, and the 6th attempt is successful and the data is successfully transmitted. It can be seen that when the channel is very idle, because the value of the attempt parameter probability p is set too small, the channel resources are wasted. Similarly, when the channel is very busy, the value of the parameter probability p is set too large, resulting in an increase in signal transmission collisions and wasting channel resources. Therefore, the parameter probability p should adapt to the channel usage situation, and the channel usage situation can be reflected by the number of packet retransmissions of CMU. Thus, the present invention optimizes the parameter probability P, decreasing the parameter probability p when the number of packet retransmissions of CMU increases; increasing the parameter probability p when the number of packet retransmissions of CMU decreases. Through the adaptive method of the parameter probability p, the transmission delay and throughput of the system are improved.

[0055] The optimization of the P-CSMA algorithm in this embodiment enables the parameter probability p to be adaptive to the signal environment, reduces the probability of signal collision and transmission delay of each aircraft, and improves the throughput of system data transmission.

[0056] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for implementing the MAC layer of a VDLM2 airborne radio, characterized in that Including: An ARM module, a receiver, and a transmitter are set in the MAC layer; The receiver is used to receive the data transmitted from the ground station in the uplink. It includes an uplink data receiving module, a first uplink data processing module, a second uplink data processing module, a third uplink data processing module, and an uplink data sending module; The transmitter is used to receive the data transmitted to the ground station in the downlink. It includes a downlink data receiving module, a first downlink data processing module, a second downlink data processing module, a third downlink data processing module, and a downlink data sending module; The MAC layer is set in the airborne radio station. The airborne radio station is connected to an airborne communication management unit, and the transmission of airborne communication primitive data is carried out through the ARINC429 bus connection; wherein, a physical layer is also set in the airborne radio station. The physical layer realizes the signal processing of the VDML2 radio station through the FPGA module, and the ARM module is used for data transmission of the VDML2 radio station in the MAC; The uplink data receiving module is used to receive the physical layer data after being processed by the FPGA module and store it in the buffer; the uplink data sending module is used to send the ARINC 429 data after being processed by the uplink data to the airborne communication management unit; The uplink data processing is sequentially processed by the first uplink data processing module, the second uplink data processing module, and the third uplink data processing module, and it includes the following steps: The first uplink data processing module parses the data in the receiving buffer according to the privately defined serial port format, assembles it into the original AVLC frame; then performs bit stuffing removal on the original AVLC frame; then decomposes it according to the frame flag FLAG into single AVLC frames; finally, performs FCS frame checksum and address filtering on the single AVLC frames, and stores the frames that pass the checksum and address filtering in the AVLC frame buffer; The second uplink data processing module performs protocol analysis on the data in the AVLC frame buffer, and adds a primitive header according to the ARINC 750 protocol standard to generate different types of primitive data; The third uplink data processing module is used to perform 429 data format encoding operations on different types of primitive data, encode the primitive data with different lengths and different types into a unified 32-bit ARINC 429 data format, and then transmit it to the uplink data sending module.

2. The MAC layer implementation method of a VDLM2 airborne radio according to claim 1, characterized in that, The downlink data receiving module is used to receive the ARINC 429 data sent from the airborne communication management unit; the downlink data sending module is used to send the AVLC frame data to the FPGA, and then the FPGA converts the data signal into a radio frequency signal and sends it through the antenna.

3. A method for implementing the MAC layer of a VDLM2 airborne radio according to claim 2, characterized in that, The downlink data processing is sequentially processed by the first downlink data processing module, the second downlink data processing module, and the third downlink data processing module, and it includes the following steps: The first downlink data processing module performs a decoding operation on the ARIN 429 data, and decodes the ARINC429 data into primitive data; The second downlink data processing module decodes the primitive data according to the ARINC 750 protocol, and determines whether it is a control primitive. If it is a control primitive, the control state is changed; if it is a data primitive, it is converted into a single AVLC frame, and the FCS check value, bit stuffing, and frame flag are added; and it is stored in the transmit buffer. The third downlink data processing module is used to implement the maintenance of the MAC layer state machine and the P-persistent carrier sense detection algorithm.

4. A method for implementing the MAC layer of a VDLM2 airborne radio according to claim 1, characterized in that The MAC layer is also used to control the access to the VHF channel. It also includes: Timer T1, Timer T2, Counter M1; The signal transmission interval of the timer T1 is TM1. When the channel is idle, it detects whether there is buffered data in the buffer. If so, it starts the timer T1; when the channel is busy, it turns off the timer T1. After the timer T2 receives a transmission request, its maximum waiting time is TM2; when the MAC layer receives a transmission request, it starts the timer T2, and turns off the timer T2 after a transmission is completed. The counter M1 has a maximum access count M1. The counter M1 accumulates the number of times after each access attempt fails. When the number of times accumulates to the maximum access count M1, it detects the channel idle condition, and immediately performs a transmission when the channel is detected to be idle.

5. A method for implementing the MAC layer of a VDLM2 airborne radio according to claim 4, characterized in that, The signal transmission interval of the timer T1 is TM1. When the channel is idle, it detects whether there is buffered data in the buffer. If so, it starts the timer T1; when the channel is busy, it turns off the timer T1. After the timer T2 receives a transmission request, its maximum waiting time is TM2; when the MAC layer receives a transmission request, it starts the timer T2, and turns off the timer T2 after a transmission is completed. The counter M1 has a maximum access count M1. The counter M1 accumulates the number of times after each access attempt fails. When the number of times accumulates to the maximum access count M1, it detects the channel idle condition, and immediately performs a transmission when the channel is detected to be idle.

6. The method for implementing the MAC layer of a VDLM2 airborne radio according to claim 4, wherein After the time of the timer T2 expires, it notifies the external on-board communication management unit that the current channel is congested and re-searches for a working frequency; and, the recorded count of the counter M1 is cleared after system initialization, when the T2 timer reaches, or after a successful access attempt.

7. A method for implementing the MAC layer of a VDLM2 airborne radio according to claim 6, characterized in that, The maximum access count M1 = [log(1 - v) / log(1 - p)]; Where, v is the cumulative probability, and the default value of the cumulative probability v is 0.999; p is the probability of successful data transmission in any single signal transmission attempt.

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