Low-overhead and low-feedback hop-by-hop coding transmission method suitable for underwater acoustic network

Abstract

The invention provides a low-overhead and low-feedback hop-by-hop coding transmission method suitable for an underwater acoustic network. Aiming at the characteristics of limited energy, high bit error rate and relatively high feedback cost of an underwater acoustic network, on the premise of keeping a hop-by-hop fountain coding transmission framework unchanged, an actually available continuous communication time period in one hop is described by utilizing underwater acoustic neighbor time, and original data is divided into a plurality of transmission stages; by jointly adopting stage division, single statistical feedback and redundancy configuration adjustment in a single hop, on the premise of meeting the reliable transmission requirement of a to-be-transmitted original data packet set of the hop, the total number of coding packets and feedback packets is controlled with fewer feedback rounds, and the overall transmission overhead of the multi-hop underwater acoustic network is reduced.

Description

Technical Field

[0001] This invention relates to the field of underwater acoustic communication network data transmission technology, and more specifically, to a low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks. Background Technology

[0002] Underwater acoustic communication network data transmission technology is used to achieve reliable data transmission between underwater nodes under acoustic channel conditions, supporting multi-hop communication services such as underwater monitoring, ocean observation, and underwater equipment coordination. Existing technologies typically introduce erasure coding methods such as fountain codes at the hop-by-hop level. By sending more coded packets than the original data packets in each hop and combining this with feedback information or retransmission operations, the probability of recovering the original data packets under packet-deleted channel conditions is improved. This type of fountain code-based hop-by-hop reliable transmission method can, to some extent, mitigate the impact of high bit error rates and large propagation delays in underwater acoustic channels, and has become one of the fundamental technical solutions for achieving hop-by-hop reliable transmission in underwater acoustic multi-hop transmission.

[0003] The existing technology has the following shortcomings: Existing fountain code-based hop-by-hop transmission methods often assume relatively stable communication conditions within a transmission process, failing to utilize underwater acoustic neighbor time to characterize the actual available continuous communication periods between nodes. The transmission process easily spans multiple non-contiguous neighbor time intervals, leading to additional waiting delays and repeated handshake overhead. Existing schemes generally rely on multiple rounds of feedback to progressively determine whether the original data packet has been fully recovered; the number of feedback packets increases with the transmission stage, resulting in high feedback costs in underwater acoustic networks with large propagation delays and limited energy. Simultaneously, the encoding end often employs fixed redundancy configurations or coarse-grained adjustment strategies, failing to adjust the number of primary and redundant encoded packets in a timely manner based on the statistical characteristics of the packet deletion channel. This often necessitates large static redundancy configurations to ensure reliability, further increasing the total number of encoded packets, making it difficult to balance reliable transmission with overall transmission overhead control. To address these issues, this invention proposes a solution. Summary of the Invention

[0004] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks includes: In a preferred embodiment, S101 underwater acoustic neighbor time and stage transmission capacity are determined. Under the constraint of underwater acoustic neighbor time, the system determines the underwater acoustic neighbor transmission capacity according to the set of original data packets to be transmitted, the underwater acoustic neighbor time corresponding to the current hop, and the underwater acoustic link bearer parameter group. Based on this, the system divides the set of original data packets to be transmitted into transmission stages, so that each transmission stage can complete the transmission of encoded packets and provide statistical feedback within one underwater acoustic neighbor time. S102 Encoded Packet Construction and Transmission: Based on the set of original data packets for the stage, the underwater acoustic neighbor transmission capacity, and the estimated packet error rate, the system determines the number and degree of redundant encoded packets for this stage. It constructs a set of stage encoded packets consisting of encoded packets with a degree corresponding one-to-one with the original data packets for the stage and redundant encoded packets covering all the original data packets for the stage. Under the constraint of the underwater acoustic neighbor transmission capacity, the system completes the transmission of the encoded packets for this stage. S103 receives, decodes, and constructs statistical feedback. Under the packet deletion channel condition, the receiving side receives the set of stage coded packets for this stage, completes the decoding of the stage coded packets based on the set of stage coded packets and the set of stage original data packets, and after determining that the transmission of the stage coded packets has ended, constructs a statistical feedback packet containing only the number of received coded packets and the original data packet recovery flag bit string arranged according to the sequence number of the stage original data packets, and sends the statistical feedback packet once in this stage. S104 Parameter Update and Stage Cyclic Control: The transmitting side updates the packet error rate estimate and determines the number of original data packets for the next transmission stage based on the number of original data packets, the number of redundant encoded packets, the number of received encoded packets carried in the statistical feedback packet, and the original data packet recovery flag bit string. While keeping the underwater acoustic neighbor time and underwater acoustic neighbor transmission capacity constraints unchanged, it determines whether the current hop transmission process has ended or whether the next transmission stage needs to be started. When it is determined that the next transmission stage needs to be started, the encoded packet construction and transmission, reception decoding and statistical feedback construction, as well as parameter update and stage cyclic control are re-executed.

[0006] In a preferred embodiment, the set of raw data packets to be transmitted represents the sequence of raw data packets that need to be reliably transmitted within the current hop range; the underwater acoustic neighbor time represents the duration for which two nodes remain within the communicable distance under relative motion conditions; the underwater acoustic link bearer parameter set represents the actual transmission capacity of the link within this duration; the underwater acoustic neighbor transmission capacity represents the upper limit of the number of encoded packets that can be transmitted within the underwater acoustic neighbor time; and the stage raw data packet set represents the allocation result of the raw data packets after dividing the set of raw data packets to be transmitted into transmission stages under the constraint of underwater acoustic neighbor transmission capacity, providing an input basis for the encoding construction and statistical feedback of subsequent transmission stages.

[0007] In a preferred embodiment, after obtaining the communication distance and relative speed between the sending and receiving nodes of the current hop, the system determines the current hop acoustic neighbor time by combining it with a preset underwater acoustic propagation speed. The acoustic neighbor time represents the duration for which the two nodes maintain a continuous communicable state within the communicable distance. Under the constraint of the acoustic neighbor time, the system uses the link bit rate and data packet length in the underwater acoustic link bearer parameter group to determine the acoustic neighbor transmission capacity. The acoustic neighbor transmission capacity reflects the number of data packets that can actually be sent according to the link bit rate within the current acoustic neighbor time. When dividing the current hop transmission phase and constructing the phase coding packet, the acoustic neighbor transmission capacity is used as the upper limit of the number of coding packets that can be sent in the current phase.

[0008] In a preferred embodiment, during the S102 encoding packet construction and transmission, the system generates an encoding packet with a degree of one for each original data packet in the stage original data packet set, so that the encoding packets with a degree of one correspond one-to-one with the stage original data packets; at the same time, the number of redundant encoding packets and the degree of redundant encoding packets are determined according to the packet error rate estimate, and multiple redundant encoding packets are generated, each of which contains the encoding results of multiple original data packets; the stage encoding packet set consists of all encoding packets with a degree of one and all redundant encoding packets, and is transmitted under the constraint of underwater acoustic neighbor transmission capacity after construction is completed.

[0009] In a preferred embodiment, when generating redundant coded packets, the system groups the set of original data packets for each stage according to a preset grouping rule, so that the number of original data packets in each group matches the estimated packet error rate. When constructing any redundant coded packet, at least one original data packet is selected from each group to participate in a bitwise XOR operation to generate the redundant coded packet. The system also tries to make the number of times each original data packet is included in the redundant coded packets as close as possible within the entire range of redundant coded packets. This increases the probability of recovering the original data packet corresponding to a coded packet that was not correctly received under packet deletion channel conditions. This makes the transmission error probability of each original data packet in the time-varying underwater acoustic channel basically equal, which is convenient for recovering the original data packet using the redundant coded packets in the subsequent decoding process.

[0010] In a preferred embodiment, in step S103, receiving, decoding, and statistical feedback construction, the receiving side determines whether the transmission of the current stage's encoded packets has ended by detecting the sequence number of the encoded packets in the detected stage's encoded packet set and combining this with a preset time interval. After determining that the current stage's transmission has ended, the receiving side calculates the number of encoded packets received in the current stage based on the successfully received encoded packets, and forms an original data packet recovery flag bit string arranged according to the sequence number of the original data packets in the stage based on the recovered original data packets. This constructs a statistical feedback packet, which is then sent once within the current stage.

[0011] In a preferred embodiment, the payload of the statistical feedback packet only includes the number of encoded packets received in this stage and the original data packet recovery flag bit string arranged according to the original data packet sequence number of the stage. It does not carry the encoded packet sequence number list, retransmission request information and channel state information. It is used to characterize the encoded packet reception and original data packet recovery status in this stage without introducing packet-by-packet acknowledgment and channel state reporting, and to compress the length of the feedback packet while ensuring the availability of a single statistical feedback.

[0012] In a preferred embodiment, in step S104, parameter update and stage loop control, after receiving the statistical feedback packet, the sending side determines the current packet deletion status based on the number of original data packets in this stage, the number of redundant encoded packets in this stage, and the number of received encoded packets, and obtains an updated packet error rate estimate; and counts the number of original data packets that have not been recovered by the end of this stage based on the original data packet recovery flag bit string, and uses this number as the number of original data packets for the next transmission stage, for subsequent encoded packet construction and transmission. In a preferred embodiment, after obtaining the updated packet error rate estimate and the number of original data packets in the next transmission stage, the transmitting side configures the number of redundant coded packets and the redundancy of coded packets in the next transmission stage according to the updated packet error rate estimate. This ensures that the number of coded packets expected to be successfully received in the next transmission stage under the packet-deleted underwater acoustic channel condition is approximately equal to the number of original data packets in that stage, thereby reducing the transmission overhead of redundant coded packets while meeting the requirement for reliable recovery of the original data packets in this hop.

[0013] In a preferred embodiment, when the number of unrecovered original data packets is zero, the sending side determines that all original data packets to be transmitted in this hop have been successfully recovered and terminates the transmission process of this hop; when the number of unrecovered original data packets is greater than zero, the sending side, while keeping the underwater acoustic neighbor time and underwater acoustic neighbor transmission capacity unchanged, reconfigures the number of redundant coded packets and the degree of redundant coded packets in the next transmission stage according to the updated packet error rate estimate, and repeatedly executes the steps of coded packet construction and transmission, reception decoding and statistical feedback construction, as well as parameter update and stage loop control, until the preset stopping condition is met, thereby achieving adaptive adjustment of the packet deletion channel characteristics by relying only on a single statistical feedback.

[0014] The present invention provides a low-overhead, low-feedback hop-by-hop coding transmission method suitable for underwater acoustic networks, with the following effects and advantages: This invention divides the set of raw data packets to be transmitted in the current hop into stages under the time constraint of underwater acoustic neighbors. By limiting each transmission and reception process to a single continuous communication period, it avoids introducing additional waiting delays and repeated handshakes by spanning multiple discontinuous communication conditions, making the current hop transmission process more concentrated and controllable in time. On this basis, at the end of each transmission stage, only one statistical feedback is sent, which centrally reports the number of received coded packets and the recovery status of the raw data packets. This is used to update the packet error rate estimate and adjust the configuration of subsequent stages with one coded packet and redundant coded packets. This allows the redundancy overhead to adaptively shrink or relax according to the packet deletion channel state, reducing the number of invalid coded packets and repeated feedback. Through the combined effect of stage division, single statistical feedback, and redundancy configuration adjustment, this method effectively reduces the number of feedback rounds per hop and the total number of coded packets and feedback packets while meeting the reliable transmission requirements of the set of raw data packets to be transmitted in the current hop. This reduces the transmission burden and processing overhead of energy-constrained underwater acoustic nodes, shortens end-to-end transmission delay, and improves the transmission efficiency and service carrying capacity of multi-hop underwater acoustic networks under high bit error rate packet deletion conditions. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0016] Figure 2 This is a schematic diagram of the redundant encoding packet of the present invention; Figure 3 This is a schematic diagram of the header structure of the encoded packet of the present invention; Figure 4 This is a flowchart of the receiving node decoding process of the present invention; Figure 5 This is a schematic diagram of the feedback packet structure of the present invention; Figure 6 This is a comparison chart of the feedback overhead of the present invention; Figure 7 This is a comparison diagram of the coding overhead of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides a low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks. Addressing the limitations of energy, high error rates, and significant feedback costs in underwater acoustic networks, this method maintains the hop-by-hop fountain coded transmission framework while utilizing underwater acoustic neighbor time to characterize the actual available continuous communication period within a hop. Within this period, the original data packet to be transmitted in the current hop is divided into several transmission stages. Each stage sends only one statistical feedback at the end, summarizing only the number of received coded packets and the recovery status of the original data packet. Based on this feedback, the redundancy configuration of subsequent stages is adjusted, enabling the system to complete reliable transmission with minimal feedback rounds under packet-deleted channel conditions, while keeping the additional coding overhead within an acceptable range.

[0019] Based on the above design concept, this method constructs a hop-by-hop encoded transmission process that sequentially executes the following steps: determination of underwater acoustic neighbor time and stage transmission capacity, construction and transmission of encoded packets, reception, decoding and statistical feedback construction, and parameter updates and stage loop control. (Refer to...) Figure 1 , Figure 1 This is a schematic diagram of the method flow of the present invention, which includes: S101 underwater acoustic neighbor time and stage transmission capacity determination is used to determine the underwater acoustic neighbor transmission capacity based on the set of raw data packets to be transmitted, the underwater acoustic neighbor time corresponding to this hop, and the underwater acoustic link bearer parameter set. Based on this, the set of raw data packets to be transmitted is divided into stages, and the underwater acoustic neighbor transmission capacity and stage raw data packet set are output. Specifically, the set of raw data packets to be transmitted represents the sequence of raw data packets that need to be reliably transmitted within this hop range; the underwater acoustic neighbor time represents the duration for which this hop maintains continuous communicability within the communicable distance. The system can estimate the underwater acoustic neighbor time of this hop based on the communication distance and relative speed between the sending and receiving nodes of this hop, combined with a preset underwater acoustic propagation speed; the underwater acoustic link bearer parameter set characterizes the actual transmission capacity of the link within this duration; the underwater acoustic neighbor transmission capacity represents the upper limit of the number of encoded packets that can be transmitted within the underwater acoustic neighbor time; and the stage raw data packet set represents the allocation result of the raw data packets after dividing the set of raw data packets to be transmitted into transmission stages under the constraint of the underwater acoustic neighbor transmission capacity, providing an input basis for the encoding construction and statistical feedback of subsequent transmission stages. This step enables the system to complete the transmission phase of sending and single statistical feedback under the time constraints of underwater acoustic neighbors, avoiding additional waiting delays and increased feedback rounds caused by the transmission phase spanning multiple discontinuous communication conditions.

[0020] S102, the construction and transmission of encoded packets, determines the number and degree of redundant encoded packets for this stage based on the original data packet set, the underwater acoustic neighbor transmission capacity, and the packet error rate estimate. Under the constraint of the underwater acoustic neighbor transmission capacity, it constructs a stage encoded packet set consisting of encoded packets of degree one and redundant encoded packets, and completes the transmission of the encoded packets for this stage, outputting the stage encoded packet set. The original data packet set represents the sequence of original data packets that need reliable transmission in this stage; the underwater acoustic neighbor transmission capacity represents the upper limit of the number of encoded packets allowed to be transmitted within the corresponding underwater acoustic neighbor time; the packet error rate estimate represents the proportion of encoded packets lost under the current packet deletion channel conditions; and the stage encoded packet set represents all encoded packets actually generated and transmitted in this stage, providing an input basis for subsequent statistical feedback and original data packet recovery. This step enables the system to automatically configure the number and degree of redundant encoded packets under given packet error rate conditions and underwater acoustic neighbor transmission capacity constraints, improving the reliable transmission probability of a single transmission stage in the packet deletion channel while controlling redundancy overhead and coding complexity.

[0021] S103 receives, decodes, and constructs statistical feedback packets. Based on the stage's coded packet set and the stage's original data packet set, under packet-deletion channel conditions, it completes the reception and decoding of the stage's coded packets, constructs and sends a feedback packet containing statistics and recovery flags, and outputs the number of received coded packets. The original data packet recovery flag bit string and the feedback packet. The stage encoded packet set represents the entire sequence of encoded packets sent by the sender in this stage; the stage original data packet set represents the entire original data packet that needs to be reliably recovered in this stage; and the number of received encoded packets... The flag bit string indicates the total number of encoded packets successfully received by the receiver in this stage; the original data packet recovery flag bit string records whether each original data packet has been successfully recovered at the end of this stage. This step enables the system to provide the necessary statistical and recovery status information for subsequent packet deletion estimation and stage loop control through a single statistical feedback method, without adding multiple rounds of feedback interaction.

[0022] The S104 parameter update and stage loop control update the packet error rate estimate for the current stage based on the number of original data packets, redundant coded packets, received coded packets, and the original data packet recovery flag. It also determines the number of original data packets for the next transmission stage, decides whether the current hop transmission process has ended or needs to start the next transmission stage, and outputs the updated packet error rate estimate and the number of original data packets for the next stage. Specifically, the number of original data packets in the current stage represents the number of original data packets that need reliable transmission when entering the S102 encoding construction and transmission step in the current transmission stage; the number of redundant coded packets in the current stage represents the number of redundant coded packets configured to offset the packet deletion effect in the current transmission stage; the number of received coded packets represents the total number of coded packets successfully received by the receiver in the current transmission stage; and the original data packet recovery flag bit string indicates whether each original data packet has been recovered by the receiver at the end of the current transmission stage. This step enables the system to update the packet error rate estimate and the number of unrecovered original data packets based on a single statistical feedback, controlling the cyclic execution of the transmission stage within the current hop, and achieving adaptive adjustment to the characteristics of the packet deletion channel without increasing the number of additional feedback rounds.

[0023] By executing the above steps sequentially, this method reconstructs the original hop-by-hop fountain coding transmission, which relied on multiple rounds of feedback and a large amount of redundancy, into a staged execution process within the time scale of underwater acoustic neighbors. The redundant configuration and staged cyclic control are driven by low-overhead single statistical feedback, which enables the system to effectively reduce the number of feedback rounds per hop and compress the total number of coded packets and feedback packets while meeting the requirement of reliable transmission of the original data packet set to be transmitted in this hop. This demonstrates the characteristics of low-overhead, low-feedback hop-by-hop coding transmission suitable for underwater acoustic networks.

[0024] The implementation process and operational effects of the method of the present invention will be described in detail below with reference to specific embodiments. It should be understood that the embodiments are only used to illustrate the technical solution of the present invention, and not to limit it. The relevant steps, parameters, and module divisions can be appropriately adjusted without changing the essence of the invention.

[0025] In an optional embodiment, S101 underwater acoustic neighbor time and stage transmission capacity are determined to complete the transmission stage of transmission and single statistical feedback under underwater acoustic neighbor time constraints.

[0026] In the above embodiments, the system first considers the time of underwater acoustic neighbors. and the link bit rate in the underwater acoustic link bearer parameter group and packet length Calculate the underwater acoustic neighbor transmission capacity, denoted as And determine it according to the following formula: ;in, This indicates a floor function, used to ensure that the planned number of encoded packets does not exceed the actual transmission capacity of the link during the duration of a single underwater acoustic neighbor relationship; link bit rate. This represents the number of data bits that can be sent per unit of time, and the data packet length. This indicates the bit length of a single data packet. (This is used to obtain the underwater acoustic neighbor transmission capacity.) Then, the system divides the set of raw data packets to be transmitted into stages based on this capacity. The system first counts the total number of raw data packets in the set of raw data packets to be transmitted; when this number is not greater than... When the number of data packets to be transmitted is greater than a certain threshold, the system will directly treat the original set of data packets to be transmitted as a single transmission stage; when the number of data packets is greater than a certain threshold, the system will directly treat the original set of data packets to be transmitted as a single transmission stage. At that time, the system divides the set of original data packets to be transmitted into multiple transmission stages according to their original order, and the number of original data packets contained in each stage does not exceed [number missing]. This process generates the initial data packet set for the current hop. Through this step, the method constrains the capacity of a single transmission stage based on underwater acoustic neighbor time, ensuring that each transmission stage can complete transmission and single statistical feedback within this constraint. This reduces feedback rounds, lowers waiting latency, and improves the adaptability and transmission efficiency of the method in mobile underwater acoustic network environments.

[0027] In an optional embodiment, S102 encoding packet construction and transmission is used to automatically configure the number and degree of redundant encoding packets under given packet error rate conditions and underwater acoustic neighbor transmission capacity constraints, thereby improving the reliable transmission probability of a single transmission stage in the packet deletion channel while controlling redundancy overhead and encoding complexity.

[0028] In the above embodiment, the system first counts the number of original data packets for the current stage in the original data packet set for that stage, denoted as . This represents the number of raw data packets that need to be reliably transmitted in this stage. Given a packet error rate estimate... Under these conditions, the system determines the number of redundant encoded packets for this stage based on the principle that, on average, the receiving side should receive approximately the same number of encoded packets as the original data packets. The preferred setting is as follows: and satisfy the following constraints: ;in, Indicates the number of raw data packets in the stage. This indicates the number of redundant encoded packets generated in this stage. This represents the current packet error rate estimate. The above relationship ensures that, assuming the packet error rate estimate is reasonable, after the coded packet is transmitted through the packet deletion channel, the receiving end can obtain approximately [value missing] on average. Each encoded packet. Combining the underwater acoustic neighbor time and stage transmission capacity determination results from the previous step, this embodiment ensures that the sum of the number of original data packets and the number of redundant encoded packets in each stage does not exceed the corresponding underwater acoustic neighbor transmission capacity when performing stage division and redundant coding configuration, so that the encoded packets of this stage can be sent within a single underwater acoustic neighbor time.

[0029] After configuring the number of redundant encoded packets, the system designs the degree distribution of the redundant encoded packets based on the original data packet set for each stage. The system aims to cover all original data packets with as few redundant encoded packets as possible, approximating the degree of unsuccessfully received packets that the receiver expects to compensate for through redundant encoded packets as the number of encoded packets. and order On average, each redundant coded packet can cover all The original data packets provide coverage. To achieve this goal, this embodiment makes the degree of each redundant coded packet correspond to the reciprocal of the packet error rate estimate, preferably making the degree of the redundant coded packet equal to... And determine according to the following formula: ;in, This indicates the redundancy level, used to represent the number of original data packets contained in each redundant coded packet. This represents the floor function, used in practical implementations to limit the redundancy coding packet degree to an integer value. After the system degree design is completed, it will round down the original data packet set of each stage. The original data packets are sorted and grouped according to their original sequence numbers, and the number of groups is denoted as . The number of original data packets contained in each group is denoted as . , Determined according to the following formula: ;in, This indicates the number of raw data packets contained in each raw data packet group. Because... The result is not necessarily an integer; the system is formed before... After each initial group of raw data packets, any insufficient positions in the last raw data packet group are filled by randomly selecting a certain number of raw data packets from the preceding raw data packet groups, ensuring that all raw data packet groups have the same number of elements. Through this grouping method, the system can provide a candidate raw data packet from each raw data packet group for each redundant encoded packet during subsequent construction of redundant encoded packets, ensuring that the frequency of each raw data packet appearing in the redundant encoded packets is as balanced as possible.

[0030] When constructing a specific redundant coded packet, the system selects one original data packet from each original data packet group that has not yet participated in the construction of the current redundant coded packet. The selected original data packet is then subjected to a bitwise XOR operation to obtain a value with a degree of... The system constructs redundant encoded packets. After completing the construction of the current redundant encoded packet, it marks the original data packets that have already participated in the construction of this redundant encoded packet as used during the current construction process. Then, it reselects original data packets that have not yet participated in the construction of this redundant encoded packet from each group of original data packets and repeats the bitwise XOR operation until a redundant encoded packet is constructed. A redundant encoded packet. (See reference) Figure 2 , Figure 2 The diagram illustrates the redundant encoding of this invention. The system groups x original data packets from the initial set of original data packets according to their original sequence numbers, forming several groups of original data packets. Each redundant encoding packet selects one original data packet from each group and performs a bitwise XOR operation to obtain a redundant encoding packet of degree G. This ensures that the frequency of each original data packet appearing in all redundant encoding packets is as balanced as possible. Through this grouping and selection method, the number of times each original data packet is included in the redundant encoding packets is approximately equal throughout the entire set of redundant encoding packets. This is beneficial for recovering most of the original data packets using redundant encoding packets when packet deletion occurs.

[0031] While constructing the redundant encoded packets, the system generates an encoded packet with a degree of one for each original data packet in the original data packet set of the stage, so that each encoded packet with a degree of one corresponds one-to-one with the data packet of the current stage. One original data packet. A single encoded packet does not involve bitwise XOR operations on multiple original data packets. The receiving side can directly recover the corresponding original data packet during decoding, which helps reduce the encoding and decoding overhead of online fountain codes. The system will... Each degree is a coded packet and Redundant coded packets are merged to form the stage coded packet set for this stage, and the stage coded packet set is then processed. Each encoded packet is randomly rearranged, and a sequence number is assigned to each encoded packet in this stage. The sequence number ranges from one to... To balance the transmission error probability of the original data packets in a time-varying underwater acoustic channel, the transmission order in this embodiment is set to descend from the sequence number of the encoded packets, i.e., starting from sequence number 1. The encoded packets are sent sequentially from the first packet to the last. This sending order ensures that the encoded packets corresponding to any given original data packet are distributed as evenly as possible across the entire sending sequence, thus mitigating the adverse effects on each original data packet during changes in channel conditions caused by relative node movement. The system employs a unified encoded packet structure in this step, referencing... Figure 3 , Figure 3This is a schematic diagram of the header structure of the encoded packet of the present invention. The encoded packet consists of a frame header, a data field, and a frame trailer. The frame header includes at least a source node level field, a source node identifier field, a destination node identifier field, a frame type field, an encoded packet sequence number field, an encoded packet degree field, and a sequence number field of the original data packets participating in the encoding. The frame trailer is provided with a cyclic redundancy check field to verify the frame header and data field of the encoded packet.

[0032] By executing this step, this method, under the constraint of underwater acoustic neighbor transmission capacity, uses packet error rate estimation to simultaneously determine the number and degree of redundant coded packets. It adopts a simplified coding structure that relies solely on bit XOR operations, so that the degree-one coded packets in the stage coded packet set cooperate with the redundant coded packets. Under the premise of controlling the number of redundant coded packets and the complexity of coding operations, it improves the reliable transmission probability of a single transmission stage in the packet deletion channel, providing a stable coding foundation for subsequent decoding recovery based on single statistical feedback.

[0033] In an optional embodiment, S103 receives decoding and statistical feedback construction S103, which is used to provide the required statistical information and recovery status information for subsequent packet deletion estimation and stage loop control in a single statistical feedback manner without increasing multiple rounds of feedback interaction.

[0034] In the above embodiment, the system first receives the set of stage coded packets for this stage under the packet deletion channel condition. The packet deletion channel is used to characterize the characteristic that the coded packets are either correctly received or deleted when transmitted on the underwater acoustic channel. The receiving side buffers each successfully received coded packet and sorts them according to the coded packet sequence number carried in the coded packet header.

[0035] The system performs an online fountain code decoding process based on the cached encoded packets. For details, please refer to [link / reference]. Figure 4 , Figure 4 This is a flowchart of the receiving node decoding process of the present invention. During decoding, in each loop, the system preferentially selects encoded packets with a degree of one and directly writes them as the corresponding original data packets into the original data packet recovery set. After recovering all currently received encoded packets with a degree of one, the system iterates through the received encoded packets with a degree greater than one, and XORs the recovered original data packets bitwise to gradually reduce the degree of the encoded packets or recover new original data packets. Whenever a new original data packet is added to the original data packet recovery set, the system uses the updated original data packet recovery set to re-iterate through the remaining encoded packets with a degree greater than one until there are no more encoded packets whose degree can be further reduced or new original data packets can be recovered.

[0036] After completing the above statistical and recovery flag construction, the system generates the feedback packet for this stage. The feedback packet uses the source node hierarchy field, source node identifier field, destination node identifier field, and encoded packet sequence number field in the frame header. The frame type field is filled with the corresponding value for the feedback frame to distinguish it from a data frame. The payload includes a field for the number of received encoded packets and a recovery flag bit string arranged according to the original data packet sequence number. The frame trailer includes a cyclic redundancy check field for verifying the frame header and payload. The field layout of the feedback packet is shown in the reference section. Figure 5 , Figure 5 This is a schematic diagram of the feedback packet structure of the present invention.

[0037] During the decoding process, the system simultaneously monitors whether the transmission of encoded packets in this phase has ended. When an encoded packet with a sequence number of one is received, it determines that the transmission of encoded packets in this phase has been completed; or, when the sequence number of the most recently received encoded packet is greater than one and there is a subsequent time interval... If no new encoded packets are received within a certain time interval, the transmission of encoded packets in this phase is also considered complete. The aforementioned time interval corresponds to the sum of the transmission durations of three consecutive encoded packets, and is used to reliably determine the end of transmission without introducing excessive waiting delay. After determining the end of transmission in this phase, the system counts the number of encoded packets successfully received in this phase within the reserved state switching time slot, and records this number as . The system constructs a recovery flag bit string arranged by the original data packet sequence number based on the original data packet recovery set. Each bit is used to identify whether the corresponding original data packet has been recovered; a value of one indicates recovery, and a value of zero indicates no recovery. After completing the above statistics and flag construction, the system constructs the feedback packet for this stage. Preferably, the feedback packet inherits the unified encoded packet header structure used in S102. It distinguishes between data frames and feedback frames by filling in the corresponding value of the feedback frame in the frame type field. The payload carries the number of received encoded packets and the recovery flag bit string. A cyclic redundancy check field is set in the frame tail to verify the header and payload of the feedback packet. After completing the construction of the feedback packet, the system sends the feedback packet to the sending side, completing the single statistical feedback for this stage.

[0038] By executing this step, the system constructs and sends a statistical feedback packet only once at the end of each transmission phase, and this feedback packet carries the number of encoded packets received in this phase. The system also tracks the recovery status of each original data packet. Instead of multiple packet-by-packet feedbacks or multiple rounds of feedback interactions in conventional schemes, it uses a single statistical feedback to replace the previous approach. This effectively reduces the number of feedback packets and feedback control overhead while maintaining transparency and visibility of decoding progress and packet deletion status. It provides a complete statistical basis for the packet deletion adaptive coding parameter update based on packet error rate estimation in subsequent steps.

[0039] In an optional embodiment, the parameter update and stage loop control step S104 is used to update the packet error rate estimate and the number of unrecovered original data packets based on a single statistical feedback, control the loop execution of the transmission stage within the current hop, and achieve adaptive adjustment of the packet deletion channel characteristics without increasing the number of additional feedback rounds.

[0040] In the above embodiment, after receiving the feedback packet returned by the receiving side, the system first reads the number of encoded packets received in the current transmission phase from the feedback packet and records this number as... The system determines the number of raw data packets in this phase. Number of redundant coded packets and the number of coded packets received Calculate the packet error rate estimate for this stage. The packet error rate estimate is determined according to the following formula: ;in, This represents the packet error rate estimate for the current transmission phase, used to characterize the proportion of coded packets lost in the packet deletion channel; Indicates the number of raw data packets in this stage; Indicates the number of redundant coded packets in this stage; This indicates the number of encoded packets successfully received by the receiving side in this stage. Based on this definition, the system can update the packet error rate estimate at the end of each transmission stage based on single statistical feedback, allowing the redundant coding configuration in subsequent transmission stages to be adjusted according to the latest packet deletion situation.

[0041] The system simultaneously recovers the flag bit string of the original data packet carried in the feedback packet, counts the number of original data packets that have not been recovered by the receiving side at the end of this phase, and records this number as the new... New This indicates the number of original data packets that still require reliable transmission when entering the next transmission stage. The system adjusts this based on the new... The value of determines whether the current hop transmission process terminates or whether the next transmission phase needs to be started: when a new hop... When the system determines that the original data packets to be transmitted in this hop have been successfully recovered in the current transmission phase, the transmission process of this hop ends, and a new transmission phase is not started; when a new... At that time, while maintaining the underwater acoustic neighbor time and underwater acoustic neighbor transmission capacity constraints given in S101, the system, based on the new... and the updated package error rate estimate Recalculate the number of new redundant coded packets The next transmission phase is reconstructed according to the method in S102, and the next transmission phase is started. Within this hop range, the construction and transmission of the encoded packets in S102, the reception, decoding and statistical feedback construction in S103, and the parameter update and phase loop control steps in this step are repeated until all original data packets are recovered by the receiving side or the preset stopping condition is met.

[0042] Through this step, the system relies solely on the single statistical feedback update packet error rate estimate and the number of unrecovered original data packets in S103, and controls whether to enter the next transmission stage based on the updated parameters. This allows the single-stage statistical feedback design and the simplified coding structure based on packet error rate to form a closed loop under the constraints of underwater acoustic neighbor time and underwater acoustic neighbor transmission capacity. This enables adaptive tracking and correction of packet deletion channel characteristics without increasing the number of feedback cycles, thereby improving the overall efficiency and reliability of hop-by-hop coded transmission in multi-hop underwater acoustic networks.

[0043] In another optional embodiment, to verify the performance of the hop-by-hop coding transmission method constructed by sequentially executing steps S101 to S104 in the embodiment in a hop-by-hop transmission scenario of an underwater acoustic network, simulation tests were conducted on this method and several comparative methods. The average number of feedback packets and the average number of encoded packets were used as evaluation indicators for feedback overhead and coding overhead, respectively. The comparative methods included nine encoding and decoding schemes: COFCNC (a component-based OFC without completion phase), simplified OFC, IOFC, chained construction, secure LT code, and LT code. Among them, COFCNC is a component-based OFC scheme without a completion phase; LT code and OFC are traditional fountain codes; IOFC is a scheme based on OFC with a performance optimization mechanism; and chained construction and secure LT code are schemes based on OFC and LT code with security optimization mechanisms, respectively. In the simulation scenario, the same underwater acoustic network topology, node motion model, and original number of data packets were used. Several comparative methods were constructed by changing the encoding and feedback methods, and the average number of feedback packets and the average number of encoded packets for each method were statistically analyzed under the same packet deletion channel conditions. Reference Figure 6 Figure 6 and Figure 7 are comparison diagrams of the feedback overhead of the present invention, used to show the number of feedback packets for ten methods, including the present method, under the same simulation conditions; Figure 7 is a comparison diagram of the coding overhead of the present invention, used to show the average number of coding packets for each method under the same decoding success probability requirement.

[0044] Regarding feedback overhead, such as Figure 6 As shown, the average number of feedback packets is used as a metric for feedback overhead. When the number of original data packets is less than 500, under the same amount of original data packet recovery, compared with COFCNC ( Compared to other coding schemes such as chain-based construction, OFC, IOFC, secure LT codes, and LT codes, the hop-by-hop coding transmission method, with its low overhead and minimal feedback, has a smaller average number of feedback packets. When the number of original packets exceeds 500, transmitting such a large number of packets in a single underwater acoustic network scenario with time constraints for underwater acoustic neighbors is typically difficult. In this extended scenario, with the same amount of original packet recovery, the average number of feedback packets in this method is still significantly lower than the other eight coding schemes, only slightly higher than the overhead of LT codes. However, as shown in Figure 7, even with a significantly higher average number of encoded packets for LT codes, this method still has an advantage in terms of overall transmission overhead, balancing feedback and coding overhead. Figure 6 It can be seen that this method achieves the minimum number of feedback packets under most original data packet count conditions. As the number of original data packets increases, the average growth rate of the number of feedback packets remains at the lowest level, indicating that using single statistical feedback at the end of each transmission stage can effectively reduce the number of feedback rounds and the number of feedback packets.

[0045] Regarding coding overhead, as shown in Figure 7, the average number of encoded packets is used as a metric for coding overhead. Our method has the lowest average number of encoded packets among all compared methods. The average number of encoded packets increases linearly with the number of original data packets, but the slope is small. This indicates that by performing staged transmission under underwater acoustic neighbor time constraints and adjusting redundancy configuration based on statistical feedback, a lower number of redundant encoded packets can be achieved under packet-deletion channel conditions, demonstrating an advantage from a coding overhead perspective. In summary... Figure 6 and Figure 7 It can be seen that the hop-by-hop encoding transmission method, which is executed sequentially from step S101 to step S104, can reduce the average number of feedback packets and the average number of encoding packets in both dimensions of feedback overhead and encoding overhead, while ensuring the reliable recovery of the original data packet set to be transmitted in this hop, thereby reducing the overall transmission overhead and latency of the multi-hop underwater acoustic network. It has the advantages of low overhead and low feedback that are suitable for the characteristics of underwater acoustic networks.

[0046] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0047] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0048] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0049] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0050] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0051] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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. A low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks, characterized in that, include: S101 Underwater acoustic neighbor time and stage transmission capacity determination: Under the constraint of underwater acoustic neighbor time, the system determines the underwater acoustic neighbor transmission capacity according to the set of original data packets to be transmitted, the underwater acoustic neighbor time corresponding to this hop, and the underwater acoustic link carrying parameter group. Based on this, the system divides the set of original data packets to be transmitted into transmission stages, so that each transmission stage can complete the transmission of encoded packets and provide statistical feedback within one underwater acoustic neighbor time. S102 Encoded Packet Construction and Transmission: Based on the set of original data packets for the stage, the underwater acoustic neighbor transmission capacity, and the estimated packet error rate, the system determines the number and degree of redundant encoded packets for this stage. It constructs a set of stage encoded packets consisting of encoded packets with a degree corresponding one-to-one with the original data packets for the stage and redundant encoded packets covering all the original data packets for the stage. Under the constraint of the underwater acoustic neighbor transmission capacity, the system completes the transmission of the encoded packets for this stage. S103 receives, decodes, and constructs statistical feedback. Under the packet deletion channel condition, the receiving side receives the set of stage coded packets for this stage, completes the decoding of the stage coded packets based on the set of stage coded packets and the set of stage original data packets, and after determining that the transmission of the stage coded packets has ended, constructs a statistical feedback packet containing only the number of received coded packets and the original data packet recovery flag bit string arranged according to the sequence number of the stage original data packets, and sends the statistical feedback packet once in this stage. S104 Parameter Update and Stage Cyclic Control: The transmitting side updates the packet error rate estimate and determines the number of original data packets for the next transmission stage based on the number of original data packets, the number of redundant encoded packets, the number of received encoded packets carried in the statistical feedback packet, and the original data packet recovery flag bit string. While keeping the underwater acoustic neighbor time and underwater acoustic neighbor transmission capacity constraints unchanged, it determines whether the current hop transmission process has ended or whether the next transmission stage needs to be started. When it is determined that the next transmission stage needs to be started, the encoded packet construction and transmission, reception decoding and statistical feedback construction, as well as parameter update and stage cyclic control are re-executed.

2. The low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 1, characterized in that, In the determination of underwater acoustic neighbor time and stage transmission capacity in S101, the set of original data packets to be transmitted is used to represent the sequence of original data packets that need to be reliably transmitted within the current hop range; underwater acoustic neighbor time is used to represent the duration for which two nodes continuously remain within the communicable distance under relative motion conditions; underwater acoustic link bearer parameter set is used to characterize the actual transmission capacity of the link within this duration; underwater acoustic neighbor transmission capacity is used to represent the upper limit of the number of encoded packets that can be transmitted within the underwater acoustic neighbor time. The stage raw data packet set is used to represent the allocation result of the raw data packets after dividing the set of raw data packets to be transmitted according to the transmission stage under the constraint of underwater acoustic neighbor transmission capacity, and provides the input basis for the encoding construction and statistical feedback of each subsequent transmission stage.

3. The low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 2, characterized in that, After obtaining the communication distance and relative speed between the sending and receiving nodes of the current hop, the system determines the current hop acoustic neighbor time by combining the preset underwater acoustic propagation speed. The acoustic neighbor time represents the duration for which the two nodes maintain a continuous communicable state within the communicable distance. Under the constraint of the acoustic neighbor time, the system uses the link bit rate and data packet length in the underwater acoustic link bearer parameter group to determine the acoustic neighbor transmission capacity. The acoustic neighbor transmission capacity reflects the number of data packets that can actually be sent according to the link bit rate within the current acoustic neighbor time. When dividing the current hop transmission phase and constructing the phase coding packet, the acoustic neighbor transmission capacity is used as the upper limit of the number of coding packets that can be sent in the current phase.

4. The low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 1, characterized in that, In the S102 encoding packet construction and transmission, the system generates an encoding packet with a degree of one for each original data packet in the stage's original data packet set, so that the encoding packets with a degree of one correspond one-to-one with the stage's original data packets; at the same time, the number of redundant encoding packets and the degree of redundant encoding packets are determined based on the packet error rate estimate, and multiple redundant encoding packets are generated. Each redundant encoding packet contains the encoding results of multiple original data packets; the stage encoding packet set consists of all encoding packets with a degree of one and all redundant encoding packets, and is transmitted under the constraint of underwater acoustic neighbor transmission capacity after construction.

5. The low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 4, characterized in that, When generating redundant coded packets, the system groups the original data packet set of the stage according to the preset grouping rules, so that the number of original data packets in each group matches the packet error rate estimate. When constructing any redundant coded packet, at least one original data packet is selected from each group to participate in the bitwise XOR operation to generate the redundant coded packet. Within the entire range of redundant coded packets, the number of times each original data packet is included is made as close as possible. This increases the probability of recovering the original data packet corresponding to a coded packet that was not correctly received by relying on the redundant coded packet under packet deletion channel conditions. This makes the transmission error probability of each original data packet in the time-varying underwater acoustic channel basically equal, which is convenient for recovering the original data packet by using the redundant coded packet in the subsequent decoding process.

6. The low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 1, characterized in that, In step S103, the receiving side detects the sequence number of the encoded packets in the detection phase encoded packet set and determines whether the transmission of the encoded packets in this phase has ended by combining the preset time interval. After determining that the transmission of this phase has ended, the number of encoded packets received in this phase is calculated based on the encoded packets successfully received in this phase. The original data packets that have been recovered are used to form a string of original data packet recovery flag bits arranged according to the original data packet sequence number in the phase. The statistical feedback packet is constructed in this way and sent once in this phase.

7. The low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 6, characterized in that, The payload of the statistical feedback packet only contains the number of encoded packets received in this stage and the original data packet recovery flag bit string arranged according to the original data packet sequence number of the stage. It does not carry the encoded packet sequence number list, retransmission request information and channel state information. It is used to characterize the encoded packet reception and original data packet recovery status in this stage without introducing packet-by-packet acknowledgment and channel state reporting, and to compress the length of the feedback packet while ensuring the availability of a single statistical feedback.

8. The low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 1, characterized in that, In step S104, parameter update and stage loop control, after receiving the statistical feedback packet, the sending side determines the current packet deletion status based on the number of original data packets in this stage, the number of redundant encoded packets in this stage, and the number of received encoded packets, and obtains the updated packet error rate estimate; and counts the number of original data packets that have not been recovered by the end of this stage based on the original data packet recovery flag bit string, and uses this number as the number of original data packets for the next transmission stage, which is used for subsequent encoded packet construction and transmission.

9. A low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 8, characterized in that, After obtaining the updated packet error rate estimate and the number of original data packets in the next transmission stage, the sending side configures the number of redundant coded packets and the redundancy of coded packets in the next transmission stage according to the updated packet error rate estimate. This ensures that the number of coded packets expected to be successfully received in the next transmission stage under the packet deletion underwater acoustic channel condition is basically equal to the number of original data packets in that stage, thereby reducing the transmission overhead of redundant coded packets while meeting the requirement of reliable recovery of the original data packets in this hop.

10. A low-overhead, low-feedback hop-by-hop coded transmission method suitable for underwater acoustic networks according to claim 8, characterized in that, When the number of unrecovered original data packets is zero, the sending side determines that all the original data packets to be transmitted in this hop have been successfully recovered and terminates the transmission process of this hop. When the number of unrecovered original data packets is greater than zero, the sending side, while keeping the underwater acoustic neighbor time and underwater acoustic neighbor transmission capacity unchanged, reconfigures the number of redundant coded packets and the degree of redundant coded packets in the next transmission stage according to the updated packet error rate estimate. It repeats the steps of coded packet construction and transmission, reception decoding and statistical feedback construction, parameter update and stage loop control until the preset stopping condition is met, thereby achieving adaptive adjustment of the packet deletion channel characteristics by relying only on a single statistical feedback.

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