A method and system for LTP transmission based on RaptorQ encoding

Abstract

The application discloses a LTP transmission method and system based on RaptorQ coding. A sending end divides to-be-transmitted data as LTP red data into RaptorQ coding blocks and source symbols, carries the source symbols by an LTP red data segment, and encapsulates repair symbols into a RaptorQ repair segment associated with an LTP session. A receiving end updates an LTP red region recombination buffer and a RaptorQ decoding buffer according to the LTP red data segment and the RaptorQ repair segment, generates an enhanced status report RS carrying LTP-RQ status extension information, and feeds back coding block recovery status and coding block recovery compensation. The sending end performs compensation transmission according to the status extension information. The application can reduce the multi-round retransmission probability in a deep space long time delay link.

Description

Technical Field

[0001] This invention belongs to the field of reliable transmission technology for deep space communication and delay-tolerant networks, specifically relating to an LTP transmission method and system based on RaptorQ coding. Background Technology

[0002] In deep space communication environments, one-way propagation delays between Earth and distant celestial bodies such as Mars can reach several minutes to over twenty minutes, with round-trip times (RTTs) on the order of tens of minutes. Furthermore, deep space links face the combined effects of path loss, link interruptions, bandwidth limitations, and high error rates. Traditional end-to-end transmission protocols that rely on fast feedback and retransmission (such as TCP / IP) are ill-suited to such long-latency, intermittent connections, and high-error-rate communication environments.

[0003] To address these challenges, Delay / Disruption Tolerant Networking (DTN) has been introduced into deep space communication systems. It achieves ordered data transmission even when the end-to-end path is not continuously connected through a "store-and-carry-forward" mechanism. Within the DTN protocol suite, the Licklider Transmission Protocol (LTP) is commonly used as a point-to-point reliable aggregation layer protocol on deep space links. LTP divides the data to be transmitted into a red zone (reliable transmission) and a green zone (unreliable transmission). For red zone data, LTP employs a three-way handshake reliable transmission loop consisting of checkpoints (CP), report segments (RS), and report acknowledgments (RA). The basic process is as follows: the sender transmits LTP red data segments (some of which carry CP); upon receiving the CP, the receiver generates an RS based on the received red zone data range and sends it back; the sender retransmits the corresponding LTP red data segments based on the received range and missing data declared in the RS; and the receiver then confirms the report segment via RA. This cycle continues until the receiver has completely received all red zone data.

[0004] However, in deep space links with extremely high round-trip latency, the above mechanism has the following inherent defects: First, any retransmission operation triggered by RS may introduce at least one additional completion delay on the order of RTT; Second, the retransmitted LTP red data segment itself may still be lost again, thereby triggering multiple rounds of RS reports and multiple rounds of retransmissions, which multiplies the LTP session completion time and seriously reduces transmission efficiency.

[0005] Existing technologies have attempted to use Forward Error Correction (FEC) coding to improve the robustness of LTP transmission in deep space links. While these schemes can improve packet loss resistance or reduce buffer usage to some extent, they generally suffer from the following shortcomings: First, the coding process lacks a unified and coordinated design with the LTP internal processes such as red data segments, checkpoints, status reports, and retransmissions. The generation and recovery of coded symbols are often independent of LTP session state management. Second, the receiver cannot provide the sender with fine-grained decoding status information (such as the recovery progress of each coded block and the remaining number of symbols) for coding recovery through the standard LTP status reporting mechanism, making it difficult for the sender to accurately determine the actual needs of current coding recovery. Third, when the repair symbols are insufficient to complete decoding, the system still has to revert to traditional LTP retransmission or upper-layer protocol retransmission, failing to fully utilize coding gain to fundamentally reduce multi-round feedback interactions. Therefore, existing solutions still face significant bottlenecks in reducing transmission overhead and shortening session completion time in long-latency links.

[0006] RaptorQ coding, as a new generation of fountain codes, has near-ideal coding efficiency (reaching or approaching capacity limits) and extremely strong packet loss recovery capabilities. After acquiring any number of coded symbols (a combination of source symbols and repair symbols) slightly more than the original data, the receiver can recover all source symbols with a very high probability, making it particularly suitable for deep space communication scenarios with high packet loss rates, long latency, and high feedback costs.

[0007] Therefore, there is an urgent need in this field for an LTP transmission mechanism based on RaptorQ coding. This mechanism can deeply coordinate the generation, decoding, and recovery processes of RaptorQ coding with the red zone data segment carrying, checkpoint triggering, status report feedback, and compensation transmission processes within the LTP protocol. This would enable the receiver to carry the recovery status and recovery compensation amount of each RaptorQ coding block in the enhanced status report, and enable the transmitter to quantitatively and incrementally generate and send repair symbols based on the recovery compensation amount of the coding block. This would achieve reliable recovery of red zone data with minimal feedback rounds, significantly reducing the probability of multiple retransmissions in deep space links and the LTP session completion time. Summary of the Invention

[0008] Purpose of the Invention: This invention aims to address the technical shortcomings of existing LTP protocols in deep space communication, such as high overhead from multiple retransmissions and long session completion times under long latency and high packet loss environments. It proposes an LTP transmission method and system based on RaptorQ coding. Its core innovation lies in the unified and coordinated design of the symbol generation and decoding recovery process of RaptorQ coding with the LTP protocol's LTP red data segment carrying, checkpoint triggering, status report feedback, and compensation transmission process. The receiver can use enhanced status reports (RS) to provide feedback to the transmitter on the recovery status of each RaptorQ coded block and the compensation amount representing the number of supplementary symbols required to complete decoding. The transmitter generates and sends a corresponding number of repair symbols based on the incremental compensation amount of the coded block recovery, while simultaneously carrying checkpoints to drive the next round of status feedback. This achieves closed-loop compensation transmission with "precise on-demand retransmission," effectively reducing multiple rounds of interaction in long-latency links, significantly shortening LTP session completion time, and improving reliable transmission efficiency in deep space environments with high bit error rates and intermittent links.

[0009] The above objectives are achieved through the following technical solutions:

[0010] An LTP transmission method based on RaptorQ coding, characterized by the following steps:

[0011] S1. The sending end uses the data to be transmitted as the red zone data of the LTP session, divides the red zone data into at least one RaptorQ coding block, and performs RaptorQ coding on each RaptorQ coding block to generate source symbols and repair symbols; wherein, the source symbols are carried by the LTP red data segment, and the repair symbols are encapsulated as RaptorQ repair segments associated with the LTP session.

[0012] S2, the transmitting end transmits the LTP red data segment and the RaptorQ repair segment; the receiving end receives and buffers the LTP red data segment and the RaptorQ repair segment;

[0013] S3. The receiving end generates an Enhanced Status Report (RS) when any of the following triggering conditions are met: a first triggering condition, receiving an LTP red data segment carrying a checkpoint CP; a second triggering condition, the red area data has been fully recovered by RaptorQ decoding before the checkpoint CP has been received; the Enhanced Status Report (RS) carries LTP-RQ status extension information, which includes at least one status item, each status item indicating the recovery status of the corresponding RaptorQ coding block and the coding block recovery compensation amount; wherein, the coding block recovery compensation amount is used to characterize the number of supplementary coding symbols required to complete the recovery of the corresponding RaptorQ coding block, and when the RaptorQ coding block has been fully recovered, the value of the coding block recovery compensation amount is zero;

[0014] S4. The transmitting end receives and parses the Enhanced Status Report RS. If there is a RaptorQ coding block with a coding block recovery compensation amount greater than zero, then compensation transmission is performed. The compensation transmission includes: generating an incremental number of new repair symbols from the corresponding RaptorQ coding block with a number not less than the coding block recovery compensation amount according to the coding block recovery compensation amount, encapsulating and sending them, and sending at least one LTP red data segment carrying an LTP checkpoint CP.

[0015] S5. Iterate through steps S3 to S4 until one of the following termination conditions is met: the LTP session is completed; or the session is terminated voluntarily.

[0016] Furthermore, when the coded block recovery compensation amount of each status item in the Enhanced Status Report (RS) received by the transmitting end is zero, the transmitting end terminates the compensation transmission for the current LTP session and determines that the red zone data has been reliably recovered.

[0017] Furthermore, the code block recovery compensation amount is determined based on the difference between the target number of valid coded symbols required to complete the decoding of the corresponding RaptorQ code block and the number of valid coded symbols already received; when the target number of valid coded symbols is greater than the number of valid coded symbols already received, the code block recovery compensation amount is equal to the difference between the two; otherwise, the code block recovery compensation amount is zero.

[0018] Furthermore, when the red zone data is divided into multiple RaptorQ coding blocks, the enhanced status report RS includes multiple status items, each of which corresponds one-to-one with each of the RaptorQ coding blocks and independently indicates the recovery status and coding block recovery compensation amount of the corresponding RaptorQ coding block.

[0019] Furthermore, the correspondence between each state item and the corresponding RaptorQ coding block is determined in any of the following ways: Method 1, determined by the explicit coding block location information carried in the state item; Method 2, determined by the predefined implicit coding block mapping rules.

[0020] The present invention also provides an LTP transmission system based on RaptorQ coding, including a transmitting module and a receiving module, wherein the transmitting module and the receiving module are used to perform the above-described method;

[0021] The transmitting module includes:

[0022] The RaptorQ coding unit is used to perform RaptorQ block coding on the red zone data of the LTP session to generate source symbols and repair symbols;

[0023] A segment encapsulation unit is used to carry the source symbol in an LTP red data segment and encapsulate the repair symbol into a RaptorQ repair segment associated with the LTP session;

[0024] The enhanced report parsing unit is used to receive and parse the enhanced status report RS from the receiving module and extract the code block recovery compensation amount of each RaptorQ code block;

[0025] The compensation transmission control unit is used to control the transmission of at least one LTP red data segment carrying a checkpoint CP when the compensation amount of the coded block recovery is greater than zero, and to control the RaptorQ coding unit to generate a new repair symbol from the corresponding RaptorQ coding block increment, which is then encapsulated by the segment encapsulation unit into a RaptorQ repair segment for transmission.

[0026] The receiving module includes:

[0027] The segment receiving unit is used to receive the LTP red data segment and the RaptorQ repair segment;

[0028] The buffer management unit is used to maintain the LTP red zone reassembly buffer and the RaptorQ decoding buffer;

[0029] The recovery compensation calculation unit is used to determine the code block recovery compensation amount for each code block according to the received source symbols and repair symbols, based on the RaptorQ code blocks.

[0030] An enhanced report generation unit is used to generate an enhanced status report RS carrying the recovery compensation amount of the coded block, and send the enhanced status report RS to the sending module.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention integrates the symbol generation and decoding recovery process of RaptorQ encoding with the LTP red data segment carrying, checkpoint triggering, status report feedback, and compensation transmission process of the LTP protocol. This enables the receiver to directly recover the entire data content of the corresponding coded block using the received source symbols and repair symbols when some LTP red data segments are missing. This avoids triggering retransmission segment by segment for missing LTP red data segments, effectively reducing multiple rounds of interaction in long-latency links and significantly shortening the LTP session completion time.

[0033] 2. This invention enhances the status report (RS) by carrying LTP-RQ status extension information, enabling the receiver to feed back the recovery status and the code block recovery compensation amount according to the RaptorQ code block. The code block recovery compensation amount is used to characterize the number of supplementary coded symbols required to complete the recovery of the corresponding code block. This overcomes the limitation of the standard LTP status report, which only reflects the information range of the received bytes, and enables the transmitter to obtain quantitative status information for the coding recovery process. This improves the ability to judge the actual recovery needs of the receiver and provides a basis for decision-making for accurate compensation transmission.

[0034] 3. This invention enables the transmitter to generate new repair symbols from the corresponding RaptorQ coding block increment and send them based on the coding block recovery compensation amount, achieving on-demand compensation transmission based on the coding block recovery compensation amount. Compared to fixed redundant transmission or falling back to the traditional LTP retransmission loop when the number of repair symbols is insufficient, this invention accurately supplements the required number of symbols on demand when the number of symbols required for decoding is insufficient, reducing unnecessary data retransmissions and link resource occupation, and improving reliable transmission efficiency in bandwidth-constrained, high-error-rate deep space links. Attached Figure Description

[0035] Figure 1 A schematic diagram of the architecture of an LTP transmission system based on RaptorQ coding is provided for an embodiment of the present invention;

[0036] Figure 2 A flowchart illustrating the RaptorQ-based LTP transmission method applied to the transmitting end according to an embodiment of the present invention;

[0037] Figure 3 A flowchart illustrating the RaptorQ-based LTP transmission method applied to the receiving end according to an embodiment of the present invention;

[0038] Figure 4 This is a schematic diagram of the data and signaling interaction timing between the sending end and the receiving end provided in an embodiment of the present invention. Detailed Implementation

[0039] The technical solutions of this invention have been clearly and completely described with reference to the accompanying drawings of the embodiments. It should be noted that the embodiments described represent only a part of this invention, and not all of it. Other embodiments obtained by those skilled in the art based on these embodiments are all within the scope of protection of this invention.

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown in the diagram, this embodiment of the invention provides an architecture diagram of an LTP transmission system based on RaptorQ coding. The system includes a transmitter and a receiver, which interact with each other via an LTP session for data and signaling. The transmitter is responsible for performing RaptorQ coding on the red zone data to be reliably transmitted, carrying the encoded source symbols in the LTP red data segment and the repair symbols in the RaptorQ repair segment, and then transmitting them. After receiving the above segments, the receiver calculates the coding block recovery compensation amount according to the coding block and feeds it back to the transmitter through an enhancement status report. The transmitter performs compensation transmission of incremental repair symbols based on the recovery compensation amount information.

[0042] The transmitting end includes a RaptorQ encoding unit, a segment encapsulation unit, an enhancement report parsing unit, and a compensation transmission control unit.

[0043] The RaptorQ coding unit performs block coding on red zone data in an LTP session. In an LTP session, the sender acquires the red zone data to be reliably transmitted and divides it into at least one RaptorQ coding block according to a preset block size. For each coding block, source symbols are generated according to the RaptorQ coding specification. During the initial transmission phase, the RaptorQ coding unit can pre-generate a certain number of repair symbols for each coding block; the pre-generated number can be configured based on the estimated link packet loss rate. During the compensation transmission phase, the compensation transmission control unit instructs the RaptorQ coding unit to incrementally generate a specified number of new repair symbols from the target coding block. The newly generated repair symbols do not duplicate the repair symbols already transmitted for that coding block.

[0044] The segment encapsulation unit is used to encapsulate source symbols and repair symbols into LTP segments respectively. Source symbols are encapsulated as LTP red data segments. These LTP red data segments can be associated with their respective RaptorQ coded blocks and coded symbol positions through extended fields or by means of session identifiers, byte offsets, etc., so that the receiver can correctly classify them. Repair symbols are encapsulated as RaptorQ repair segments. In one implementation, the RaptorQ repair segment is an unreliable transmission segment; its payload carries the repair symbols, and it can carry the identifier of its coded block and the identifier of the corresponding coded symbol through extended fields. LTP does not perform reliable transmission acknowledgment and retransmission mechanisms for RaptorQ repair segments.

[0045] The Enhanced Status Report (RS) parsing unit receives and parses the Enhanced Status Report (RS) from the receiving end. The RS utilizes the standard LTP header extension mechanism to carry LTP-RQ status extension information. Specifically, an extension type identifier can be written into the extension area of ​​the standard RS header, and the extension content is the LTP-RQ status extension field. The Enhanced Status Report (RS) parsing unit extracts this extension field from the received RS, obtains the corresponding coded block identifier, recovery status indication, and coded block recovery compensation value for each status item, and provides this information to the compensation transmission control unit.

[0046] The compensation transmission control unit is used to make decisions and execute compensation transmissions based on the status information provided by the enhancement report parsing unit. If the compensation amount of the coded block recovery for all coded blocks is zero, it is determined that the red zone data has been reliably recovered, and the compensation transmission for the current LTP session is terminated. The LTP session is then completed or closed according to the standard procedure. If the compensation amount of any coded block is greater than zero, the compensation transmission process begins: for each coded block with a compensation amount greater than zero, the RaptorQ coding unit is notified to incrementally generate a new repair symbol of no less than the compensation amount, which is then encapsulated by the segment encapsulation unit into a RaptorQ repair segment for transmission; simultaneously, at least one LTP red data segment carrying CP is scheduled to be transmitted. Its core function is to trigger the receiver to generate the next round of enhancement status reports upon receipt, maintaining the operation of the LTP state machine.

[0047] The receiving end includes a segment receiving unit, a buffer management unit, a recovery compensation calculation unit, and an enhancement report generation unit.

[0048] The segment receiving unit is used to receive LTP red data segments and RaptorQ repair segments from the transmitting end. Based on the segment type identifier or extension identifier in the segment header, the segment receiving unit sends the LTP red data segments into the LTP red area reassembly buffer and sends the encoded symbols in the LTP red data segments and RaptorQ repair segments into the RaptorQ decoding buffer of the corresponding encoded blocks.

[0049] The buffer management unit maintains two types of buffers. The LTP red zone reassembly buffer organizes received LTP red data segments according to the standard LTP method, using red zone offsets, and is used to verify whether the red zone data has been received completely. The RaptorQ decoding buffer maintains the set of received coded symbols for each coded block, indexed by the coded block. The two types of buffers are logically independent: the LTP red zone reassembly buffer serves standard LTP receive range determination and status report generation, while the RaptorQ decoding buffer serves RaptorQ decoding recovery and coded block recovery compensation calculation.

[0050] The recovery compensation calculation unit is used to determine the recovery compensation amount for each coding block. This unit iterates through each RaptorQ coding block, and for each coding block, calculates the coding block recovery compensation amount based on its target number of valid coding symbols and the number of received valid coding symbols. The specific calculation method is detailed below.

[0051] The Enhancement Report Generation Unit generates an Enhancement Status Report (RS) carrying the recovery compensation amount of the coded blocks and sends it to the sender. When the triggering condition is met, the Enhancement Report Generation Unit obtains the recovery status and recovery compensation amount of each coded block from the Recovery Compensation Calculation Unit, generates a status item, and encapsulates the status item into an LTP-RQ status extension field, writing it into the extension area of ​​the standard RS segment header. Each status item contains at least the coded block recovery compensation amount information of the corresponding coded block. The correspondence between status items and coded blocks can be determined through explicit coded block location information or implicit coded block mapping rules.

[0052] In the above structure, this invention maintains consistency with standard LTP in the following aspects: The header format and field definitions of the LTP red data segment are consistent with standard LTP. The source symbols generated by RaptorQ encoding are carried in the LTP red data segment, and the semantics and operation methods of fields such as CP flag, session identifier, and red zone offset in the header remain unchanged. The carrying method of CP and its role in the LTP state machine are consistent with standard LTP, and the basic interaction path of the receiver generating a status report after receiving CP is retained. The enhanced status report (RS) carries LTP-RQ status extension information through the extension area of ​​the standard LTP segment header. For LTP implementations that do not support this extension, this extension type can be regarded as an unknown extension and ignored, without affecting the parsing and processing of standard RS. As an unreliable transmission segment, the RaptorQ repair segment can be discarded as an unknown segment if the standard LTP implementation does not define this segment type, without affecting the normal interaction between the LTP red data segment and the standard status report. Therefore, the method of this invention can provide enhanced reliable transmission capabilities while maintaining consistency with standard LTP.

[0053] The code block recovery compensation amount is the core parameter driving the compensation transmission in the method of this invention, which represents the number of supplementary coded symbols required to complete the decoding recovery of a RaptorQ coded block.

[0054] For a RaptorQ coded block, the following four core quantities are defined: Number of source symbols. The total number of source symbols contained in this coded block. The target number of valid coded symbols. The minimum number of encoded symbols required to complete the decoding and recovery of this encoded block. In a preferred embodiment, Values In practical engineering implementation, it can be used as Add a small integer redundancy (For example Take 1 or 2), that is, take This redundancy is used to conservatively ensure a high decoding success rate. The introduction of this redundancy does not change the overall architecture and process of the method of this invention. Number of valid encoded symbols received. The receiver calculates the total number of coded symbols (including source symbols and repair symbols) with distinct ESIs accumulated in the coded block. In a preferred embodiment, according to the RaptorQ coding specification, the probability of linear correlation between coded symbols corresponding to different ESIs is extremely low, and the receiver can determine this by performing deduplication and counting of the ESIs of the received coded symbols. Explicit matrix rank deficiency detection is usually unnecessary before decoding. Code block recovery compensation amount. Defined as .when Less than When the difference between the two values ​​is equal, the amount of compensation for the recovered coded block is equal to the difference, representing the minimum number of coded symbols needed to complete the decoding recovery; when... When D is reached or exceeded, the compensation amount for the coded block recovery is zero, indicating that the receiver has accumulated a sufficient number of coded symbols for decoding.

[0055] For cases where the data is divided into multiple coding blocks, the coding block recovery compensation amount for each coding block is calculated independently. Assume the red area data is divided into... The th RaptorQ encoded block, the th One coded block The number of source symbols is The number of effective coding symbols for the target is The number of valid encoded symbols received is The code block recovery compensation amount for that code block. When a certain coded block When the value is zero, it indicates that the encoded block has met the decoding conditions and can be decoded and recovered independently without waiting for all other encoded blocks to complete.

[0056] For example, a source symbol number The number of target effective coded symbols in a RaptorQ coded block. Take 17. During the initial transmission phase, the receiver receives 10 source symbols and 3 repair symbols of this coded block. All of these symbols have different ESIs. Code block recovery compensation amount This indicates that the receiving end still needs to supplement at least 4 encoded symbols to complete the decoding and recovery. If the receiving end subsequently receives 4 repair symbols incrementally generated by the sending end, then... Updated to 17. The coded block is marked as recovered.

[0057] In this embodiment, the receiving end performs decoding recovery when the code block recovery compensation amount of the corresponding code block is zero. At this time, a number of code symbols not less than the target valid code symbols have been received, and the decoder can complete the source symbol recovery with a high probability. Attempting decoding when the value is greater than zero may fail due to insufficient encoded symbols, introducing unnecessary computational overhead. Therefore, with... As a decoding condition, it not only ensures the predictability of decoding behavior, but also is logically consistent with the information on the recovery compensation of the encoded block fed back in the enhanced state report.

[0058] Figure 2 This is a flowchart illustrating the RaptorQ-based LTP transmission method applied to the transmitting end according to an embodiment of the present invention. Figure 3 This is a schematic diagram of a process applied to the receiving end according to an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the data and signaling interaction timing between the transmitting end and the receiving end, provided in an embodiment of the present invention. The following is in conjunction with... Figures 2 to 4 The end-to-end workflow is described in terms of the timeline of a complete LTP session.

[0059] During the initial transmission phase, the sender establishes an LTP session, acquires the red zone data to be reliably transmitted, and divides the red zone data into blocks according to a preset coding block size. Each block is a RaptorQ encoded block. RaptorQ encoding is performed on each block to generate... The system generates one source symbol and can pre-generate a certain number of repair symbols for each coded block. The source symbol is encapsulated into an LTP red data segment by the segment encapsulation unit, and a correspondence is established between the source symbol and the LTP red data segment through the aforementioned carry-over or association methods. The repair symbol is encapsulated into a RaptorQ repair segment by the segment encapsulation unit. The transmitter sets the CP flag in the header of one or more LTP red data segments.

[0060] During the initial transmission phase, the receiver continuously receives LTP red data segments and RaptorQ repair segments. For LTP red data segments, the segment receiving unit extracts the segment header information and includes it in the LTP red area reassembly buffer, and includes the source symbol data carried by it in the RaptorQ decoding buffer of the corresponding coded block according to the coded block identifier and ESI. For RaptorQ repair segments, the segment receiving unit extracts the coded block identifier and ESI, and includes the repair symbol data in the RaptorQ decoding buffer of the corresponding coded block. Received coded symbols with different ESIs are accumulated and counted, and duplicate symbols are discarded.

[0061] The receiver triggers the generation of an Enhanced Status Report (RS) in two scenarios. First, the receiver receives an LTP red data segment with a CP flag set in the segment header; this is the basic path for triggering a status report in standard LTP. Second, before the receiver receives any CP red data segments, the recovery compensation calculation unit detects that the code block recovery compensation of all RaptorQ coded blocks is zero, and the red zone data is fully recovered by RaptorQ decoding. In this case, the receiver actively constructs an Enhanced Status Report (RS) and sends it to the transmitter, notifying the transmitter in advance that reliable transmission has been completed. This second scenario is an enhancement introduced in this invention, complementary to the standard LTP path of "sending RS after receiving CP," enabling early completion of the transmission loop without relying on the arrival of CP, further shortening session completion time.

[0062] Upon triggering, the enhancement report generation unit obtains the code block recovery compensation amount for each code block from the recovery compensation amount calculation unit. And the recovery status, generating each status item. Each status item contains the code block recovery compensation amount information for the corresponding code block. For a fully recovered code block ( The compensation value is zero; for coded blocks that have not yet been fully recovered ( The compensation amount is Each status item is encapsulated as an LTP-RQ status extension field, written into the extension area of ​​the standard RS segment header, and sent to the sender via the LTP session.

[0063] The sender's enhancement report parsing unit receives and parses the enhancement status report (RS), extracts each status item from the LTP-RQ status extension field, and obtains the code block recovery compensation amount for each code block. The compensation transmission control unit makes decisions based on this: if all coded blocks... If all values ​​are zero, it is determined that the red zone data has been reliably recovered, and the compensation transmission for the current LTP session is terminated. The LTP session is then completed or closed according to the standard procedure. If at least one coded block exists... If the value is greater than zero, then the compensation transmission process begins.

[0064] In the compensation transmission process, the compensation transmission control unit performs each... For coded blocks with a value greater than zero, the RaptorQ coding unit is notified to generate new repair symbols incrementally from that coded block. The newly generated repair symbols do not duplicate those already transmitted for that coded block. The number of newly generated repair symbols is determined based on the coded block recovery compensation amount: in one implementation, considering that repair symbols transmitted in compensation in deep space links may still be lost, the transmitter may transmit a number greater than zero based on link state information. The compensation transmission control unit encapsulates newly generated repair symbols into RaptorQ repair segments to improve the success rate of single-round compensation and reduce the overhead of multi-round feedback and compensation. Simultaneously, the compensation transmission control unit schedules the transmission of an LTP red data segment carrying the CP flag. This CP red data segment can carry source symbol data that has not yet been successfully delivered; its core function is to signal the receiver to generate the next round of enhancement state report, maintaining the normal operation of the LTP state machine. The RaptorQ repair segment and the CP red data segment are transmitted together during compensation transmission.

[0065] After receiving the RaptorQ repair segment and CP red data segment from the compensation transmission, the segment receiving unit incorporates the newly received repair symbols into the RaptorQ decoding buffer of the corresponding coded block. The recovery compensation calculation unit updates the RaptorQ decoding buffer of each coded block. Recalculate If a CP red data segment is received at this time, or if all coded blocks are detected again... If all values ​​are zero, the Enhanced Report Generation Unit generates a new round of Enhanced Status Report (RS) and sends it to the sending end.

[0066] The aforementioned enhancement report generation and compensation transmission are repeated cyclically until the enhancement status report received by the sender shows that the code block recovery compensation amount for all code blocks is zero. At this point, the sender terminates the compensation transmission, and the LTP session is completed. If the LTP session reaches a preset timeout condition or reaches a maximum number of transmissions, or other termination conditions, the session can also be terminated according to the standard LTP procedure.

[0067] To illustrate the above process more intuitively, a specific session example containing two RaptorQ coded blocks is given below. Assume the red zone data is divided into two RaptorQ coded blocks (denoted as block 0 and block 1), and the number of source symbols in each coded block is... Number of effective coding symbols for the target All values ​​are set to 17. The sender generates 16 source symbols and 5 repair symbols (ESIs from 16 to 20) for block 0, and 16 source symbols and 5 repair symbols (ESIs from 16 to 20) for block 1. The source symbols are encapsulated into 32 LTP red data segments, and the repair symbols are encapsulated into 10 RaptorQ repair segments. The CP is set in the last LTP red data segment. The sender completes the initial transmission.

[0068] Suppose that in a deep space link, due to bit errors and packet loss, the receiver actually receives the following data: 10 source symbols and 4 repair symbols (all with different ESIs) from block 0, and 12 source symbols and 3 repair symbols (all with different ESIs) from block 1. At this time, what is the number of valid coded symbols received in block 0? Code block recovery compensation amount Block 1 Code block recovery compensation amount .

[0069] Upon receiving an LTP red data segment carrying CP, the receiver triggers the generation of an Enhanced Status Report. The Enhanced Status Report contains two status items: Status Item 0 indicates that block 0 has not been recovered, with a coded block recovery compensation of 3; Status Item 1 indicates that block 1 has not been recovered, with a coded block recovery compensation of 2.

[0070] After parsing the enhanced status report, the sender performs compensation transmission. Considering that the repair symbols from the compensation transmission may still be lost in the deep space link, the sender, in conjunction with the link status information, sends more repair symbols than the amount of compensation for the recovery of each coded block: 5 new repair symbols are generated for the incremental block 0, 4 new repair symbols are generated for the incremental block 1, and an LTP red data segment carrying CP is sent at the same time.

[0071] Suppose that during the compensation transmission, due to packet loss in the link, the receiver actually receives 4 out of the 5 repair symbols for block 0 and 2 out of the 4 repair symbols for block 1. After the update, block 0... , Block 1 , Both coded blocks have zero recovery compensation, indicating that decoding is possible. The receiver calls the RaptorQ decoder to complete source symbol recovery. After receiving the CP red data segment in the compensation transmission, the receiver triggers the generation of a new round of enhancement status report. In this report, the recovery status of both status items is "recovered," and the coded block recovery compensation is zero.

[0072] After parsing the new round of enhancement status reports, the sending end confirms that the code block recovery compensation amount for all code blocks is zero, the red zone data has been reliably recovered, and terminates the compensation transmission for the current LTP session. The LTP session is complete.

[0073] In this example, the sender transmits more repair symbols than the amount of code block recovery compensation during the compensation transmission. Some of these repair symbols are lost during transmission, but the number of arriving repair symbols still meets the decoding requirements of each code block, and full recovery is completed in just one round of compensation transmission. This demonstrates the sender's strategy of sending redundant repair symbols in conjunction with link state information: using appropriate transmission redundancy to cope with packet loss in the compensation transmission itself, and improving the success rate of single-round compensation without excessively increasing transmission overhead. Throughout the process, the enhanced state report is carried out through the LTP standard segment header extension mechanism, and the transmission and reception of CP follow the standard LTP procedure. The enhancement mechanism of this invention achieves coordination with RaptorQ coding recovery within the standard LTP framework.

[0074] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the patent. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An LTP transmission method based on RaptorQ coding, characterized in that, Includes the following steps: S1. The sending end uses the data to be transmitted as the red zone data of the LTP session, divides the red zone data into at least one RaptorQ coding block, and performs RaptorQ coding on each RaptorQ coding block to generate source symbols and repair symbols; wherein, the source symbols are carried by the LTP red data segment, and the repair symbols are encapsulated as RaptorQ repair segments associated with the LTP session. S2, the transmitting end transmits the LTP red data segment and the RaptorQ repair segment; the receiving end receives and buffers the LTP red data segment and the RaptorQ repair segment; S3. The receiving end generates an Enhanced Status Report (RS) when any of the following triggering conditions are met: a first triggering condition, receiving an LTP red data segment carrying a checkpoint CP; a second triggering condition, the red area data has been fully recovered by RaptorQ decoding before the checkpoint CP has been received; the Enhanced Status Report (RS) carries LTP-RQ status extension information, which includes at least one status item, each status item indicating the recovery status of the corresponding RaptorQ coding block and the coding block recovery compensation amount; wherein, the coding block recovery compensation amount is used to characterize the number of supplementary coding symbols required to complete the recovery of the corresponding RaptorQ coding block, and when the RaptorQ coding block has been fully recovered, the value of the coding block recovery compensation amount is zero; S4. The transmitting end receives and parses the Enhanced Status Report RS. If there is a RaptorQ coding block with a coding block recovery compensation amount greater than zero, then compensation transmission is performed. The compensation transmission includes: generating an incremental number of new repair symbols from the corresponding RaptorQ coding block with a number not less than the coding block recovery compensation amount according to the coding block recovery compensation amount, encapsulating and sending them, and sending at least one LTP red data segment carrying an LTP checkpoint CP. S5. Iterate through steps S3 to S4 until any of the following termination conditions are met: the LTP session is completed; or the session is actively terminated. The block recovery compensation amount is determined based on the difference between the target number of valid coded symbols required to complete the decoding of the corresponding RaptorQ block and the number of valid coded symbols already received; when the target number of valid coded symbols is greater than the number of valid coded symbols already received, the block recovery compensation amount is equal to the difference between the two; otherwise, the block recovery compensation amount is zero.

2. The method according to claim 1, characterized in that, When the compensation amount of the coded block recovery for each status item in the Enhanced Status Report (RS) received by the transmitting end is zero, the transmitting end terminates the compensation transmission for the current LTP session and determines that the red zone data has been reliably recovered.

3. The method according to claim 1, characterized in that, When the red zone data is divided into multiple RaptorQ coding blocks, the Enhanced Status Report (RS) includes multiple status items, each of which corresponds one-to-one with each of the RaptorQ coding blocks and independently indicates the recovery status and coding block recovery compensation amount of the corresponding RaptorQ coding block.

4. The method according to claim 3, characterized in that, The correspondence between each state item and the corresponding RaptorQ coding block is determined in one of the following ways: Method 1, determined by the explicit coding block location information carried in the state item; Method 2, determined by the predefined implicit coding block mapping rules.

5. An LTP transmission system based on RaptorQ coding, characterized in that, It includes a sending module and a receiving module, wherein the sending module and the receiving module are used to perform the method according to any one of claims 1 to 4; The transmitting module includes: The RaptorQ coding unit is used to perform RaptorQ block coding on the red zone data of the LTP session to generate source symbols and repair symbols; A segment encapsulation unit is used to carry the source symbol in an LTP red data segment and encapsulate the repair symbol into a RaptorQ repair segment associated with the LTP session; The enhanced report parsing unit is used to receive and parse the enhanced status report RS from the receiving module and extract the code block recovery compensation amount of each RaptorQ code block; The compensation transmission control unit is used to control the transmission of at least one LTP red data segment carrying a checkpoint CP when the compensation amount of the coded block recovery is greater than zero, and to control the RaptorQ coding unit to generate a new repair symbol from the corresponding RaptorQ coding block increment, which is then encapsulated by the segment encapsulation unit into a RaptorQ repair segment for transmission. The receiving module includes: The segment receiving unit is used to receive the LTP red data segment and the RaptorQ repair segment; The buffer management unit is used to maintain the LTP red zone reassembly buffer and the RaptorQ decoding buffer; The recovery compensation calculation unit is used to determine the code block recovery compensation amount for each code block according to the received source symbols and repair symbols, based on the RaptorQ code blocks. An enhanced report generation unit is used to generate an enhanced status report RS carrying the recovery compensation amount of the coded block, and send the enhanced status report RS to the sending module.

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