Application layer network coding design method for multipath transmission network

Abstract

The invention provides a multipath transmission network-oriented application layer network coding design method, which comprises the following steps of: setting system parameters at a sending end according to transmission quality and requirements, including a maximum interval threshold, a minimum packet loss rate threshold and a change weight factor of an Inter coding packet; the information packets are scheduled and transmitted on a plurality of paths, and each path independently generates an Intra coding packet. And after each path is independently decoded, a receiving end summarizes results to a total decoder, and feeds back a packet loss rate and an Inter coding packet number change suggestion. And the sending end dynamically adjusts the generation and insertion strategy of the Inter coding packet according to the feedback. And the receiving end preferentially decodes the information packet lost earliest and submits the decoded information packet in time. According to the method, Intra coding and Inter coding are combined, so that the transmission quality and efficiency are improved, the time delay and packet loss rate are reduced, and the timeliness and integrity of information are ensured. The method is suitable for a real-time data transmission scene.

Description

Technical Field

[0001] The invention belongs to the field of wireless communication standardization process, and in particular relates to an application layer network coding design method for a multipath transmission network. Background Art

[0002] With the rapid development of communication technology, emerging applications such as Internet of Vehicles communications, remote sensing data collection, and control system communications have put forward higher requirements for the real-time, reliability, and efficiency of data transmission. Multipath transmission is an effective way to increase the transmission rate and reduce the transmission delay. However, traditional multipath transmission schemes (such as MPTCP) use multipath polling scheduling and face serious head-of-line blocking problems in scenarios with unstable channels. Although the Intra coding technology in existing systems enhances the transmission reliability of a single path, it has problems such as low efficiency, lack of inter-path coordination, and insufficient adaptability. This results in the system being unable to fully utilize the potential of multipath transmission and making it difficult to meet the requirements for data freshness and transmission delay.

[0003] Although a comprehensive system update is an option, the cost of equipment upgrades is huge, and many old devices can still partially meet the requirements of the new system. Therefore, a more economical and practical method is to optimize the existing system. The present invention proposes to introduce additional redundant information, namely "Inter coding packets", at the transmitting end of the old system. This method can significantly improve the reliability and efficiency of transmission without significantly changing the existing system structure. Inter coding packets can help the receiving end recover data packets lost during transmission, effectively reduce end-to-end delays, improve the overall reliability of the system, and greatly reduce the cost of system transformation. However, how to effectively design and implement the Inter coding mechanism, and how to coordinate Intra coding and Inter coding in a multipath network, still need in-depth research. Especially in a dynamic and uncertain network environment, it becomes particularly important to design an adaptive coding scheme. In addition, how to maximize the use of delayed feedback information to improve communication performance is also a key issue. Summary of the invention

[0004] The purpose of the present invention is to provide an application layer network coding design for multipath transmission networks, which determines whether it is necessary to add new cross-path coding packets and calculates the number of cross-path coding packets that need to be added by using delayed feedback information based on generations, thereby solving the technical problems of difficulty in parameter change and high packet loss rate in the existing multipath transmission framework.

[0005] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0006] An application layer network coding design for multipath transmission networks specifically includes the following steps:

[0007] Step 1: Before transmission begins, set system parameters based on previous transmission quality and transmission requirements, including: Inter-coding packet coding maximum interval threshold L th , L th ≥2, Inter code packet change weight factor γ, γ>1, by adjusting the maximum interval threshold L of the code packet th and the variable weight factor γ to achieve adaptive adjustment of Inter coding packets to optimize transmission quality and efficiency;

[0008] Step 2: At the beginning of transmission, the sender initializes the number of Inter coded packets to be sent to zero; at the beginning of each generation, all the information packets to be transmitted in this generation are obtained, and scheduled and transmitted on multiple paths; each path has an independent encoder and decoder, and independently generates Intra coded packets. Each Intra coded packet is a linear combination of all information packets and Inter coded packets after the previous Intra coded packet in the path; before receiving feedback from the receiver, the sender will continue to send Inter coded packets after completing the established transmission task to ensure that all information packets of each generation can be successfully decoded;

[0009] Step 3. At the receiving end, each path is equipped with an independent decoder. After each packet is transmitted, each path is first decoded independently, and the successfully decoded data packet is immediately passed to the main decoder at the receiving end. Each information packet that arrives at the main decoder must be uploaded after the previous information packet is uploaded to the application layer. After the data packets of the same generation are uploaded, a backup is retained in the main decoder to help with subsequent encoding. If a packet is eventually lost, the receiving end will send feedback, which includes the packet loss rate e of this generation, the average end-to-end delay D of this generation, and the recommendation on the change in the number of Inter-coded packets. The feedback information is in D F Arrives at the sender after the time slot;

[0010] Step 4: At the current time t≥D F In the case of , when the transmitter did not send Inter coded packets in the previous generation and received feedback information from the previous generation, it is determined whether it is necessary to send Inter coded packets according to the feedback information; if it is not necessary, it jumps to step 2; if it is necessary, it calculates the coding interval L of the Inter coded packet u , and jump to step 5;

[0011] Step 5: The sender receives the u Generate Inter code packets and send them every L u Each packet is inserted into an Inter-coded packet until the end of this generation, and the resulting sequence is scheduled to be transmitted on multiple paths;

[0012] Step 6: At the current time t≥D FIn the case of , the receiving end first decodes independently on each path, and the successfully decoded data packets are immediately aggregated to the general decoder, and the known information packets are submitted to the application layer in real time and in sequence. Each information packet that arrives at the general decoder must be uploaded after the previous information packet is uploaded to the application layer; the data packets of the same generation are kept as a backup in the general decoder after being uploaded to help subsequent encoding; after being aggregated to the general decoder, if all the information packets have not been Inter decoded and there is no packet loss, feedback information is sent to suggest reducing Inter encoding packets; if there is still packet loss, jump to step 7;

[0013] Step 7. If there are still packets that have not been decoded after Intra decoding, the main decoder will give priority to decoding the earliest lost packets when receiving Inter coded packets, and immediately upload the decoded packets to the application layer; if all lost packets are recovered in Inter decoding, feedback is sent, suggesting that the number of Inter coded packets will not be changed; if there are still packets that have not been recovered after Inter decoding within the specified range, all existing and unsubmitted packets are submitted in order, and feedback information is sent, suggesting that Inter coded packets be increased;

[0014] Step 8: When the transmitter sends Inter coded packets in the previous generation and receives feedback on the change of the number of Inter coded packets, the number of Inter coded packets is adjusted according to the feedback instruction; when the number of Inter coded packets is reduced, the new L is calculated. u , if at this time L u ≥L th , this generation does not send Inter code packets and jumps to step 2; then this generation does not send Inter code packets and jumps to step 2; when the number of code packets is increased or the number remains unchanged, calculate the new L u , and jump to step 5;

[0015] Step 9. Repeat steps 5-8 until data transmission is completed.

[0016] Furthermore, in step 1, adaptive adjustment of Inter coded packets is achieved by adjusting system parameters to optimize transmission quality and efficiency. Specifically, the change rate of Inter coded packets increases with the increase of weight factor γ; the use range of Inter coded packets increases with the minimum packet loss rate threshold e th The increase and maximum interval threshold L th The expected end-to-end delay decreases first and then increases when the number of Inter-coded packets increases, while the expected packet loss rate increases with the increase of the number of Inter-coded packets.

[0017] Furthermore, the Inter code packet is responsible for cross-path encoding and decoding, and the Intra code packet on each path is only responsible for encoding and decoding on the path.

[0018] Furthermore, if an inter-coded packet needs to be sent in a generation, the inter-coded packet is a linear combination of all previous source packets of the current generation. Let α i is a coding coefficient randomly selected from a finite field, p i is the source information packet, then the Inter encoding packet is:

[0019]

[0020] Furthermore, the data packet b transmitted on path p i,p It may be a source information packet or an Inter coding packet. Let β i,p is a coding coefficient randomly selected from a finite field, then the kth Intra coding packet on the path is:

[0021]

[0022] Furthermore, if no Inter coded packets were sent in the previous generation, the number of Inter coded packets that need to be sent in the current generation depends on the total packet loss rate e during decoding in the previous generation. The coding interval of the coded packets that need to be sent in the current generation is:

[0023]

[0024] Furthermore, if the previous generation sent an Inter coded packet, and the sender of the current generation receives feedback for adding an Inter coded packet, the coding interval of the Inter coded packet of the current generation is:

[0025]

[0026] Furthermore, if the previous generation sent an Inter coded packet, the sender of the current generation receives feedback to reduce the Inter coded packet, and determines that the current generation still needs to send the Inter coded packet, then the interval of the Inter coded packet of the current generation is:

[0027] L u =γL u .

[0028] The present invention provides an application layer network coding design method for a multipath transmission network, which has the following advantages:

[0029] 1. The present invention can make full use of the delayed feedback information with generations as intervals, estimate the multipath packet loss rate and decoding status, and determine the additional redundancy amount added by the sender accordingly. While ensuring the data freshness of the receiving end, the transmission efficiency and the arrival rate of the data packet are greatly improved. Specifically, when the Inter coded packet is added for the first time, the number of increases depends on the total packet loss rate e of the previous generation decoding, and each subsequent transmission increases or decreases the number of Inter coded packets based on the feedback of the previous generation.

[0030] 2. The present invention can increase the effective redundancy without changing the existing multipath transmission parameters, reduce the changes to the old system, and reduce the replacement cost. Specifically, the present invention does not change the original Intra coding packet transmission system, but chooses to increase the extra Inter coding packet redundancy to reduce the bit error rate and reduce the end-to-end delay.

[0031] 3. The present invention requires less feedback information and fewer network parameters of the model. The transmission parameters of the next generation are obtained only through simple feedback, and it has good robustness in multipath transmission channels with complex conditions. Specifically, the present invention only adjusts the number of Inter coding packets through a single change coefficient γ, which is less than other model parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of an example of detailed transmission process of a transmitting end and a receiving end of an embodiment of an application layer network coding design method for a multipath transmission network of the present invention;

[0033] Figure 2 It is a schematic diagram of an example of the transmission and encoding process of the transmitting end of an embodiment of an application layer network coding design method for a multipath transmission network of the present invention;

[0034] Figure 3 It is a schematic diagram of a transmitter coding and transmission scheme flow chart of an embodiment of an application layer network coding design method for a multipath transmission network of the present invention;

[0035] Figure 4 It is a flowchart of a receiving-end decoding and feedback scheme of an embodiment of an application layer network coding design method for a multipath transmission network of the present invention;

[0036] Figure 5 It is a schematic diagram of end-to-end delay simulation performance of an embodiment of an application layer network coding design method for a multipath transmission network of the present invention. DETAILED DESCRIPTION

[0037] In order to better understand the purpose, structure and function of the present invention, the following further describes in detail an application layer network coding design method for a multipath transmission network of the present invention in conjunction with the accompanying drawings.

[0038] The present invention is applicable to a multipath transmission network with sparse feedback information. At the beginning of each generation, all information packets of the current generation are prepared and scheduled and sent by a sending end. The receiving end first decodes each path independently, then decodes jointly, and instructs the sending end to change redundancy in feedback according to the decoding situation. The sending end determines the change amount of the additional redundancy according to the delayed feedback of each generation. The sending end achieves a trade-off between system reliability and freshness by adjusting the redundancy change speed factor and threshold.

[0039] In one embodiment, reference Figure 2 and Figure 3 As shown in the flowchart, the present invention proposes an application layer network coding design method for multipath transmission networks, including the following main steps:

[0040] Step 1: Before transmission begins, set system parameters based on previous transmission quality and transmission requirements, including: Inter-coding packet coding maximum interval threshold L th , L th ≥2, Inter code packet change weight factor γ, γ>1, by adjusting the maximum interval threshold L of the code packet th , minimum packet loss rate threshold e th The adaptive adjustment of Inter coded packets is realized by changing the weight factor γ to optimize the transmission quality and efficiency. The change rate of Inter coded packets increases with the increase of the weight factor γ; the use range of Inter coded packets increases with the minimum packet loss rate threshold e th The increase and maximum interval threshold L th The expected end-to-end delay decreases first and then increases when the number of Inter-coded packets increases, while the expected packet loss rate increases with the increase of the number of Inter-coded packets.

[0041] Step 2: At the beginning of transmission, the sender initializes the number of Inter coded packets to be sent to zero. At the beginning of each generation, all the information packets that need to be transmitted in this generation are obtained, and scheduled and transmitted on multiple paths. Each path has an independent encoder and decoder, and independently generates Intra coded packets. Each Intra coded packet is a linear combination of all information packets and Inter coded packets after the previous Intra coded packet in the path. Before receiving feedback from the receiver, the sender will continue to send Inter coded packets after completing the established transmission task to ensure that all information packets of each generation can be successfully decoded.

[0042] Step 3. At the receiving end, each path is equipped with an independent decoder. After each packet is transmitted, each path is first decoded independently, and the successfully decoded data packet is immediately passed to the main decoder at the receiving end. Each information packet that arrives at the main decoder must be uploaded after the previous information packet is uploaded to the application layer. After the data packets of the same generation are uploaded, a backup is retained in the main decoder to assist in subsequent encoding. If a packet is eventually lost, the receiving end will send feedback, which includes the packet loss rate e of this generation, the average end-to-end delay D of this generation, and the recommendation on the change in the number of Inter-coded packets. The feedback information is in D F It arrives at the sender after the time slot.

[0043] Step 4: At the current time t≥D F In the case of , when the transmitter did not send Inter coded packets in the previous generation and received feedback information from the previous generation, it is determined whether it is necessary to send Inter coded packets based on the feedback information. If it is not necessary to send, jump to step 2; if it is necessary to send, calculate the coding interval L of the Inter coded packet u , and jump to step 5. Let the data packet transmitted on path p be b i,p , b i,p It may be a source information packet or an Inter coded packet. The kth Intra coded packet on the path is where β i,p are coding coefficients randomly selected from a finite field.

[0044] Specifically, if an inter-coded packet needs to be sent in a generation, the inter-coded packet is a linear combination of all previous packets in the current generation, which is where α i is a coding coefficient randomly selected from a finite field, p i Is the source packet.

[0045] If no Inter coded packets were sent in the previous generation, the number of Inter coded packets that need to be sent in this generation depends on the total packet loss rate of the previous generation and the coding interval of the coded packets that need to be sent in this generation.

[0046] Step 5: The sender receives the u Generate Inter code packets and send them every L u Each packet is inserted into an Inter-coded packet until the end of this generation, and the resulting sequence is scheduled to be transmitted on multiple paths.

[0047] Step 6: At the current time t≥D FIn the case of , the receiving end first decodes independently on each path, and the successfully decoded data packets are immediately aggregated to the master decoder, and the known information packets are submitted to the application layer in real time and in sequence. Each information packet that arrives at the master decoder must be uploaded after the previous information packet is uploaded to the application layer. After uploading, the data packets of the same generation are kept as a backup in the master decoder to help with subsequent encoding. After being aggregated to the master decoder, if all the information packets have not been Inter decoded and there is no packet loss, feedback information is sent to suggest reducing Inter encoding packets; if there is still packet loss, jump to step 7.

[0048] Step 7: If there are still packets that have not been decoded after Intra decoding, the main decoder will give priority to decoding the earliest lost packets when receiving Inter coded packets, and immediately upload the decoded packets to the application layer. If all lost packets are recovered in Inter decoding, feedback is sent, suggesting that the number of Inter coded packets will not be changed; if there are still packets that have not been recovered after Inter decoding within the specified range, all existing and unsubmitted packets are submitted in order, and feedback information is sent, suggesting that Inter coded packets be increased.

[0049] Step 8: When the transmitter sends Inter coded packets in the previous generation and receives feedback on the change of the number of Inter coded packets, the number of Inter coded packets is adjusted according to the feedback indication. If the transmitter receives feedback on the increase of Inter coded packets, the coding interval If the sender receives feedback to reduce the Inter coding packet, the coding interval L u =γL u .

[0050] When reducing the number of Inter coding packets, calculate the new L u , if the new L u ≥L th , this generation does not send Inter coded packets and jumps to step 2; when the number of coded packets increases or remains unchanged, calculate the new L u , and skip to step 5.

[0051] Step 9. Repeat steps 5-8 until data transmission is completed.

[0052] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings.

[0053] Figure 1 It is a schematic diagram of the detailed transmission process of the sending end and the receiving end mentioned in the first embodiment of the present invention.

[0054] in

[0055] There are 4 source packets to be sent in one generation. The initial Inter coding interval L for the first transmission u =4, maximum Inter coding threshold L th =6, change factor γ = 2. It takes 1 time slot for path 1 to transmit a data packet, 2 time slots for path 2 to transmit a data packet, and the feedback delay is 1 time slot. All packets have been pre-scheduled to each path by the sender before each generation is sent. The end-to-end delay is defined as the difference between the time when a packet is received in order and the time when the first packet is sent in the generation where the packet belongs.

[0056] At the beginning of the first time slot, the sender sends packet p1 on path 1 and p2 on path 2. p1 is sent successfully, but p2 fails to be sent.

[0057] At the beginning of the second time slot, the transmitter sends p3 on path 1, and path 2 is not idle and does not send packets. The receiver receives p1, saves a copy of p1 in the decoder, and directly transmits p1 to the upper layer.

[0058] At the beginning of the third time slot, the transmitter sends p4 on path 1 and Inter-coded packet u1 on path 2. Both p4 and u1 fail to be sent. The receiver receives p3. Since p2 before p3 has not been decoded successfully, p3 remains in the decoder and is not transmitted to the upper layer.

[0059] At the beginning of the 4th time slot, the transmitter sends the Intra coded packet c of path 1 on path 1. 1,1 , Path 2 is not idle and no packet is sent. The receiving end does not receive the packet.

[0060] At the beginning of the 5th time slot, the transmitter sends p5 on path 1 and path 2 Intra coded packet c on path 2. 2,1 p5 and c 2,1 All are sent successfully. The receiving end receives c 1,1 , and according to c 1,1 Decode p4 on the same path. Since p2 before p4 has not been decoded successfully, p3 and p4 remain in the decoder and are not transmitted to the upper layer.

[0061] At the beginning of the 6th time slot, the transmitter sends p6 on path 1, and path 2 is not idle and no packets are sent. p6 fails to be sent. The receiver receives p5. Since p2 before p5 has not been decoded successfully, p3, p4, and p5 remain in the decoder and are not transmitted to the upper layer.

[0062] At the beginning of the 7th time slot, the transmitter sends p7 on path 1 and p8 on path 2. Both p7 and p8 are sent successfully. The receiver receives c 2,1 , and according to c2,1 The Inter coded packet u1 lost in path 2 is recovered. In the decoder, u1 is then decoded into p2. p2, p3, p4, and p5 are transmitted to the upper layer together.

[0063] At the beginning of the 8th time slot, the transmitter sends the path-Intra coded packet c on path- 1,2 , path 2 is not idle and no packet is sent. 1,2 The transmission is successful. The receiving end receives p7. Since p6 before p7 has not been decoded successfully, p7 remains in the decoder and is not transmitted to the upper layer.

[0064] At the beginning of the 9th time slot, the transmitter sends Inter coded packet u2 on path 1, and path 2 starts to send repeated Inter coded packets. u2 is sent successfully, but repeated Intra coded packets fail to be sent. The receiver receives p8 and c 1,2 , and according to c 1,2 Decode p6 on path 1. p6, p7, and p8 are sent to the upper layer together. The receiving end determines that a generation has been completely transmitted.

[0065] At the beginning of the 10th time slot, since no feedback was received from the receiving end, the sending end continued to send repeated Inter coded packets, all of which were sent successfully. The receiving end received u2 and determined that the current generation had been transmitted and there were extra Inter coded packets that were not used. The receiving end sent feedback to inform the sending end that the current generation had been transmitted and instructed the sending end to reduce the number of Inter coded packets.

[0066] At the beginning of the 11th time slot, the transmitter receives feedback and recalculates the new L u =γL u (old) = 8, because the new L u ≥L th =6, so the sender does not send Inter coded packets in this generation, and re-adds Intra coded packets to the information packets of this generation and schedules them to different paths for transmission.

[0067] In the 1st to 9th time slots, the detailed transmission process between the transmitter and the receiver is as follows: Figure 1 In the above time slots 1-9, a complete generation transmission is completed, the average end-to-end delay is 6.125, and the transmission reliability is 100%.

[0068] Figure 21 is a schematic diagram of an example of the transmission and encoding process of the transmitting end mentioned in the first embodiment of the present invention. Before a generation is sent, all information packets of the generation are prepared. It is assumed that the number of encoding packets of a generation is 4. Before starting multipath transmission, the transmitting end first adds Inter encoding packets. It is assumed that the sending interval of Inter encoding packets is L. u =4, that is, an Inter coded packet will be added after every 4 information packets. After this step, the number of information packets (including source information packets and Inter coded packets) that need to be transmitted by multipath increases to 5. The sender schedules the coded information packets once according to the principle of minimum transmission delay, that is, it is required to minimize the maximum transmission delay, and independently add Intra coded packets on each path according to their respective erasure probabilities. In this example, there are two paths, the first path Lc1=3, and the second path Lc2=2. Lc1=3 means that for every three information packets allocated on path 1, an Intra coded packet will be added later, and the same applies to path 2. After scheduling, all coded packets will be transmitted in order by the sender.

[0069] Figure 5 The end-to-end delay performance simulation diagram for this example is shown in Figure 1. One generation contains 1000 packets to be sent. As can be seen from the figure, the larger L u The insertion of Inter-coded packets is reduced, resulting in a rapid increase in end-to-end delay. u As it continues to increase, its influence decreases. u If it is too small, too many Inter-coded packets will delay packet transmission and increase end-to-end delay. c It also affects the end-to-end delay. Usually, a larger L c Will reduce latency, especially in L u Large. Although the larger L c Sometimes it is beneficial, but due to the weak error correction capability of intra coded packets, additional delays are caused, so the coding strategy needs to be balanced. Poor channel conditions will increase end-to-end delay.

[0070] The invention discloses an application layer network coding design method for a multipath transmission network, which aims to improve transmission efficiency and reliability while meeting data freshness requirements by combining intra coding and inter coding. This method can not only give full play to the potential of the multipath transmission network, but also maintain compatibility with the existing system, and provide an economical and practical solution for performance optimization of the multipath transmission system.

[0071] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for designing application layer network coding for multipath transmission networks, characterized in that: The specific steps include: Step 1: Before transmission begins, set system parameters based on previous transmission quality and transmission requirements, including: Inter-coding packet coding maximum interval threshold L th , L th ≥2, Inter code packet change weight factor γ, γ>1, by adjusting the maximum interval threshold L of the code packet th and the variable weight factor γ to achieve adaptive adjustment of Inter coding packets to optimize transmission quality and efficiency; Step 2: At the beginning of transmission, the sender initializes the number of Inter coded packets to be sent to zero; at the beginning of each generation, all the information packets to be transmitted in this generation are obtained, and scheduled and transmitted on multiple paths; each path has an independent encoder and decoder, and independently generates Intra coded packets. Each Intra coded packet is a linear combination of all information packets and Inter coded packets after the previous Intra coded packet in the path; before receiving feedback from the receiver, the sender will continue to send Inter coded packets after completing the established transmission task to ensure that all information packets of each generation can be successfully decoded; Step 3. At the receiving end, each path is equipped with a decoder. After each packet is transmitted, each path is first decoded independently, and the successfully decoded data packets are immediately passed to the main decoder at the receiving end. Each information packet that arrives at the main decoder must be uploaded after the previous information packet is uploaded to the application layer. After the data packets of the same generation are uploaded, a backup is retained in the main decoder to help with subsequent encoding. If a packet is eventually lost, the receiving end will send feedback, which includes the packet loss rate e of this generation, the average end-to-end delay D of this generation, and the suggestion of the change in the number of Inter-coded packets. The feedback information is in D F Arrives at the sender after the time slot; Step 4: At the current time t≥D F In the case of , when the transmitter did not send Inter coded packets in the previous generation and received feedback information from the previous generation, it is determined whether it is necessary to send Inter coded packets according to the feedback information; if it is not necessary, it jumps to step 2; if it is necessary, it calculates the coding interval L of the Inter coded packet u , and jump to step 5; Step 5: The sender receives the u Generate Inter code packets and send them every L u Each packet is inserted into an Inter-coded packet until the end of this generation, and the resulting sequence is scheduled to be transmitted on multiple paths; Step 6: At the current time t≥D F In the case of , the receiving end first decodes independently on each path, and the successfully decoded data packets are immediately aggregated to the general decoder, and the known information packets are submitted to the application layer in real time and in sequence. Each information packet that arrives at the general decoder must be uploaded after the previous information packet is uploaded to the application layer; the data packets of the same generation are kept as a backup in the general decoder after being uploaded to help subsequent encoding; after being aggregated to the general decoder, if all the information packets have not been Inter decoded and there is no packet loss, feedback information is sent to suggest reducing Inter encoding packets; if there is still packet loss, jump to step 7; Step 7. If there are still packets that have not been decoded after Intra decoding, the main decoder will give priority to decoding the earliest lost packets when receiving Inter coded packets, and immediately upload the decoded packets to the application layer; if all lost packets are recovered in Inter decoding, feedback is sent, suggesting that the number of Inter coded packets will not be changed; if there are still packets that have not been recovered after Inter decoding within the specified range, all existing and unsubmitted packets are submitted in order, and feedback information is sent, suggesting that Inter coded packets be increased; Step 8: When the transmitter sends Inter coded packets in the previous generation and receives feedback on the change of the number of Inter coded packets, the number of Inter coded packets is adjusted according to the feedback instruction; when the number of Inter coded packets is reduced, the new L is calculated. u , if at this time L u ≥L th , then this generation does not send Inter code packets and jumps to step 2; when the number of code packets increases or remains unchanged, calculate the new L u , and jump to step 5; Step 9. Repeat steps 5-8 until data transmission is completed.

2. The method for designing application layer network coding for multipath transmission networks according to claim 1, characterized in that: In step 1, the adaptive adjustment of Inter coded packets is achieved by adjusting the system parameters to optimize the transmission quality and efficiency. Specifically, the following steps are included: the change rate of Inter coded packets increases with the increase of weight factor γ; the use range of Inter coded packets increases with the minimum packet loss rate threshold e th The increase and maximum interval threshold L th The expected end-to-end delay decreases first and then increases when the number of Inter coding packets increases, while the expected packet loss rate increases with the increase of the number of Inter coding packets.

3. The method for designing application layer network coding for multipath transmission networks according to claim 1, characterized in that: The Inter code packet is responsible for cross-path encoding and decoding, and the Intra code packet on each path is only responsible for encoding and decoding on the path.

4. The method for designing application layer network coding for multipath transmission networks according to claim 1, characterized in that: In step 4, if an inter-coded packet needs to be sent in a generation, the inter-coded packet is a linear combination of all previous packets of the current generation, which is where α i is a coding coefficient randomly selected from a finite field, p i Is the source packet.

5. The method for designing application layer network coding for multipath transmission networks according to claim 1, characterized in that: In step 4, if the previous generation did not send Inter coded packets, the number of Inter coded packets that need to be sent in this generation depends on the total packet loss rate of the previous generation and the coding interval of the Inter coded packets that need to be sent in this generation. Where e is the packet loss rate when the receiving end fails to decode.

6. The method for designing application layer network coding for multipath transmission networks according to claim 1, characterized in that: In step 2, the packet b transmitted on path p i,p is a source information packet or an Inter coded packet, and the kth Intra coded packet on the path is where β i,p are coding coefficients randomly selected from a finite field.

7. The method for designing application layer network coding for multipath transmission networks according to claim 1, characterized in that: In step 8, if the sender receives feedback for adding Inter coding packets, the Inter coding interval is reduced to the original times, that is If the transmitter receives feedback to reduce the Inter coding packet, the Inter coding interval increases to γ ​​times of the original, that is, L u =γL u .

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