Reliable end-to-end transmission method supporting unmanned aerial vehicle cluster bee colony network

Abstract

The invention discloses an end-to-end reliable transmission method supporting an unmanned aerial vehicle cluster bee colony network. The problem that a traditional end-to-end reliable transmission control protocol is poor in transmission performance in a high dynamic scene of the unmanned aerial vehicle cluster bee colony network is mainly solved. The method has the following characteristics: 1) the rateless characteristic of the fountain code is utilized on an inferior link, so that the protocol does not need to execute timeout retransmission after packet loss; (2) a congestion detection and control mechanism is introduced, and network congestion is not indirectly judged by adopting transmission timeout; 3) the node adjusts the degree distribution mode of the fountain code, the relay node forwarding mode and the coding redundancy according to the network congestion degree and the link state; 4) adjusting the number of assembly lines and the size of a coding window through the current congestion index, and carrying out congestion control; according to the invention, the transmission rate can be improved and the service continuity can be maintained in a high-dynamic scene.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and particularly relates to an end-to-end reliable transmission method supporting a drone swarm network. Background Art

[0002] In a drone swarm network, end-to-end reliable data transmission is a core issue. These networks usually operate in an environment without the support of fixed infrastructure, and nodes dynamically establish connections through wireless communication. Due to the mobility of nodes and the instability of wireless channels, the network topology changes frequently, resulting in poor performance of traditional transmission protocols in such an environment. For example, the TCP protocol is mainly designed for wired networks, and its congestion control mechanism reduces the data sending rate when packet loss occurs to avoid network congestion. However, in a drone swarm network, packet loss is not always caused by congestion, but may also be due to routing failures or signal interference caused by node movement. Therefore, it is incorrect to regard packet loss caused by these non-congestion factors as network congestion, which will lead to frequent triggering of congestion control, resulting in reduced throughput and increased transmission delay. In addition, the per-packet end-to-end acknowledgment mechanism is inefficient in multi-hop networks because each intermediate node needs to wait for an acknowledgment from the downstream node, which will cause serious delay and efficiency problems in a network with a rapidly changing network topology. Solving this problem, that is, how to achieve efficient and reliable end-to-end data transmission in a drone swarm network, has important practical value for improving network performance and meeting key communication requirements. Especially in adversarial environments or emergencies, such as military communications and disaster relief, reliable data transmission is crucial for ensuring the success of missions and the safety of personnel. Therefore, researching and developing an end-to-end reliable transmission method suitable for the characteristics of a drone swarm network has important theoretical and application value for enhancing the practicality and reliability of the network.

[0003] Sreenivasa B.C and G.C.Bhanu Prakash proposed a congestion control method based on link layer measurements called Linkdb-TCP in their published paper "Linkdb-TCP: A Congestion Control Technique For MANET Based On Link Layer Measurements". The steps of this method are as follows: (1) The receiver predicts congestion by analyzing network latency, calculates the network latency using the information provided by the sender, and makes congestion predictions based on this. (2) Calculate the average latency by collecting the latency history of ten consecutive data packets and compare it with the previous latency to predict the congestion situation in the network. (3) Calculate the smoothed round-trip time (SRTT) and use it as an indicator of network congestion to control transmission parameters. (4) Adjust the congestion window (cwnd) according to the SRTT value, packet size, transmission rate, and the congestion window value of the previous packet to respond to congestion in the network. However, due to the frequent changes in the topology of communication nodes, which are dynamic and the link layer is unreliable, it will affect the accuracy of congestion prediction. At the same time, this method relies on the feedback of the receiver to adjust the behavior of the sender, which may not be timely enough in an environment with high latency or high packet loss rate. In addition, Linkdb-TCP behaves similarly to TCP when the network conditions are good, but when congestion occurs, it collects link parameters by sending special packets Linkdb, which may increase additional overhead and affect network performance.

[0004] Noor Mast et al. proposed a cross-layer solution called CSCC (Cross-layer Solution for Contention Control) in their published paper "ACross-Layer Solution for ContentionControl to Enhance TCP Performance in Wireless Ad-Hoc Networks", aiming to enhance the performance of TCP in infrastructureless networks. The steps of this method are as follows: (1) Each node calculates the weighted moving average (WMA) of the number of attempts to access the medium at the MAC layer to estimate channel contention. (2) When the WMA reaches the preset threshold CCThresh, the node starts to mark packets to notify the source node of the contention in the network. (3) After receiving the contention notification, the source node adjusts the size of its congestion window (cwnd) to control the proportion of packets injected into the network. (4) To ensure fairness for each flow, flows with larger cwnd are penalized more. However, since the calculation of WMA depends on the choice of the α value, this may lead to insufficient or overly sensitive response to the network contention situation, affecting network performance. In addition, the CSCC mechanism may face challenges in high-mobility environments because the rapid movement of nodes may lead to inaccurate contention estimation, thus affecting the congestion control effect of TCP.

[0005] In the paper "Fountain Code based Hop-by-Hop Reliable Data Transmission Scheme in Multi-Hop MANETs" published by Changdong Li et al., while combining digital fountain code technology, the computing resources of relay nodes are utilized, and a reliable transmission scheme called Fountain code-based Hop-by-Hop Reliable Data Transfer (FHRDT) is proposed. The steps of this method are as follows: (1) At the source node, the original data is grouped and encoded using fountain code to form encoded data packets. (2) The encoded data packets are transmitted hop by hop through the multi-hop network to the destination node. (3) At the intermediate nodes, the network layer performs re-encoding operations, while the transport layer attempts to decode data blocks, and generates new re-encoded data packets and sends them to the next hop in case of incomplete decoding. (4) At the destination node, fountain decoding is performed. After successful decoding, the source node is notified to release the cache through the end-to-end mechanism, and the previous node is notified to start transmitting the next data block. However, since the FHRDT scheme performs re-encoding operations at the intermediate nodes, it may introduce additional computational and storage overheads. Especially in a highly dynamic multi-hop network environment, the rapid movement of nodes may cause the re-encoded data packets to be unable to be generated in a timely or accurate manner, affecting the reliability and efficiency of the transmission. In addition, although the one-hop acknowledgment mechanism used in the FHRDT scheme reduces the waiting delay, it increases the control overhead. Especially when the packet loss rate is relatively high, more feedback messages may be required, thus increasing the burden on the network. Summary of the Invention

[0006] To solve the above problems existing in the prior art, the present invention provides an end-to-end reliable transmission method for supporting a drone swarm network. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0007] An end-to-end reliable transmission method for supporting a drone swarm network includes:

[0008] S100, in the connection establishment phase, the source node and the destination node establish a communication connection by mutually sending messages, and there are multiple relay nodes on the communication link;

[0009] S200, in the transmission phase, each current node periodically intercepts messages from its own message queue according to the coding window and encodes them into coding symbols in units of transmission rounds; performs congestion control and formulates a pipeline transmission strategy according to the estimated congestion degree, and transmits the coding symbols to the next node according to the pipeline transmission strategy until the destination node is reached; the destination node recovers the original message from the received coding symbols through the transmission rounds; the current node is the source node or a relay node;

[0010] S300. In the connection release phase, the source node and the destination node release the communication connection by sending messages to each other to end the transmission.

[0011] Beneficial effects:

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] First, based on fountain codes, the present invention proposes a reliable transmission protocol for supporting drone swarm networks. The source node and relay nodes sense the congestion status and link reliability information of the end-to-end path to provide a basis for formulating a pipelined transmission strategy, which can effectively cope with dynamic topology changes and packet loss problems in communication scenarios. Compared with existing protocols, the present invention can more reasonably distinguish between packet loss caused by network congestion and non-congestion, avoiding unnecessary congestion control triggers caused by misjudgment, thus significantly improving network performance.

[0014] Second, according to the network sensing results, the present invention proposes an adaptive coding transmission scheme for congestion and link reliability. The link reliability information is used to make decisions on the degree distribution pattern, relay node forwarding pattern, and coding redundancy, and the congestion information is used to adjust the number of pipelines and coding window parameters, further optimizing the continuity of data transmission and the utilization efficiency of network resources, so that high transmission stability and efficiency can still be maintained in the face of complex network conditions or frequent node movements.

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0016] Figure 1 is a flowchart of an end-to-end reliable transmission method for supporting drone swarm networks provided by the present invention;

[0017] Figure 2 is the overall implementation architecture diagram of the present invention.

[0018] Figure 3 is a schematic diagram of the connection establishment phase of the present invention;

[0019] Figure 4 is a flowchart of the encoder (source end) of the present invention in the transmission phase;

[0020] Figure 5 is a flowchart of the decoder (destination end) of the present invention in the transmission phase;

[0021] Figure 6 is a flowchart of the relay node of the present invention in the transmission phase;

[0022] Figure 7 is a schematic diagram of the degree feedback mode transmission of the present invention;

[0023] Figure 8 This is a schematic diagram of the connection release stage of the present invention;

[0024] Figure 9 This is a graph of the simulation results of the throughput performance of each function of the present invention. Specific Embodiments

[0025] The following further describes the present invention in detail with reference to specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0026] The technical idea for achieving the object of the present invention is as follows: According to the dynamic topology changes and packet loss situations of the network, adaptively adjust the degree of participation of relay nodes in encoding, construct an efficient transmission path, and reduce the performance loss caused by misjudging congestion; By real-time monitoring the network status and dynamically adjusting the transmission strategy, minimize the impact on network transmission caused by link failures due to the high mobility of nodes in high-dynamic scenarios, and improve the adaptability of the network to high-dynamic network scenarios. At the same time, the present invention optimizes the continuity of data transmission and the utilization efficiency of network resources through a pipelined transmission mechanism and a priority division scheme, ensuring that high efficiency and stable data transmission can still be maintained under complex network conditions or frequent node movements.

[0027] As Figure 1 shown, the present invention provides an end-to-end reliable transmission method for supporting an unmanned aerial vehicle swarm network, including:

[0028] S100. In the connection establishment stage, the source node and the destination node establish a communication connection by mutually sending messages, and there are multiple relay nodes on the communication link;

[0029] S200. In the transmission stage, each current node periodically intercepts messages from its own message queue according to the encoding window and encodes them into encoded symbols in units of transmission rounds; Perform congestion control and formulate a pipelined transmission strategy according to the estimated congestion degree, and transmit the encoded symbols to the next node according to the pipelined transmission strategy until the destination node is reached; The destination node recovers the original message from the received encoded symbols through transmission rounds; The current node is the source node or a relay node;

[0030] Among them, the source node of the present invention is the source end, which is provided with an encoder, the destination node is the destination end, which is provided with a decoder, and the relay node is provided with both a decoder and an encoder.

[0031] S300. In the connection release stage, the source node and the destination node release the communication connection by mutually sending messages to end the transmission.

[0032] In a specific embodiment of the present invention, in combination with Figure 2 and Figure 3 , S100 includes:

[0033] S110, The source node sends a CREQ message to the destination node and enters the CREQ_SENT state, waiting for confirmation from the destination node. The CREQ message carries a parameter set, indicating that the source node hopes to establish a connection.

[0034] S120, After receiving the CREQ message from the source node, the destination node confirms the request and sends a CREP message to the source node, indicating agreement to establish a connection and initialize the transmission, and getting ready to receive the upcoming coded symbols. The destination node enters the CREQ_RECEIVED state and waits for confirmation from the source node.

[0035] S130, After receiving the CREP message from the destination node, the source node sends a CCFM message to confirm the CREP message of the destination node. The source node enters the ESTABLISHED state and starts the transmission phase. After receiving the CCFM message, the destination node also enters the ESTABLISHED state, completing the connection establishment phase.

[0036] In a specific embodiment of the present invention, referring to Figure 4 , in S200, each current node periodically intercepts messages from its own message queue according to the coding window and encodes them into coded symbols in units of transmission rounds. Congestion control is performed according to the estimated congestion level and a pipeline transmission strategy is formulated, and the coded symbols are transmitted to the next node according to the pipeline transmission strategy until reaching the destination node, including:

[0037] S210a, The source node continuously receives original messages and stores them in its own message queue, and the relay node receives the messages transmitted by the previous node and stores them in its own message queue.

[0038] S210b, The current node sets the coding window length in each transmission round, and judges whether the length of its own message queue is less than the coding window size within a time interval. If so, it fills it up with all-zero bytes until it is not less than the coding window size. If the message queue is empty, it enters the step of connection release.

[0039] Among them, if it is the first transmission round, the source node sets the size of the coding window to 1, indicating to select 1 original message from the message queue to start probing the network bandwidth and making the network gradually adapt to the traffic. Otherwise, it increments the transmission round number by 1 and doubles the coding window until it reaches W cmax and then continues to increase in the way of incrementing by 1.

[0040] S210c, The current node takes out messages with the same size as the coding window from its own message queue, combines them into a byte block, and splits the byte block into several source symbols according to the source symbol size.

[0041] Among them, the size of the source symbol should not exceed the size of the merged byte block MBB (Merge Byte Block) at most, and the size of the source symbol is calculated according to the following formula: BDP is the end-to-end delay-bandwidth product, indicating the maximum amount of data in transit in the network. N typ It is related to the message type or packet loss rate. If the packet loss rate is lower than 1%, it is set to 1. If the packet loss rate is between 1% and 5%, it is set to 2. If the packet loss rate is higher than 5%, it is set to 4. Non-delay-sensitive services such as large files can be set to 8. Suppose it is desired to have a probability that at least one of the n encoded symbols sent in a network with a packet loss rate of p loss reaches successfully not less than a certain threshold P th , there is From this, it is solved that: The minimum source symbol size D is the total amount of data to be transmitted.

[0042] S210d, the current node reset the transmission number threshold, and encodes the several source symbols to obtain encoded symbols; after marking each encoded symbol with the current transmission round number, compress it into a data packet;

[0043] S210e, perform congestion control according to the estimated congestion degree and formulate a pipeline transmission strategy, and send the data packet to the next transmission node according to the pipeline transmission strategy until the transmission number reaches the threshold and then increase the encoding interval to continue sending;

[0044] The source node will set the number of encoded symbols to be generated according to the formulated pipeline transmission strategy, continuously generate encoded symbols, and send each encoded symbol after marking it with the current transmission round number.

[0045] S210f, the current node listens to the feedback information. If the source node receives the OVER message and the relay node receives the NOVER, return to S210a; if it receives the DFLT information, return to S210d.

[0046] In a specific embodiment of the present invention, the congestion control according to the estimated congestion degree in S200 includes:

[0047] S220a, for any current node, set the time interval T as the statistical period, and initialize the number of data packets N received within the T time period p (T) to 0, and initialize the maximum sequence numbers P of the packets received within the nth and the (n - 1)th time intervals T n and P n-1 to 0;

[0048] S220b, for any current node, whenever a data packet is received within the time interval T, then Np (T) is incremented by 1, and P is updated. n is the maximum sequence number of the data packets received within the current time interval T;

[0049] S220c, any current node, at the end of each time interval T, uses the formula to calculate the packet loss rate and use it as the reliability of the current link, and then update P n-1 is P n , initialize N p (T) is 0 for the next update calculation;

[0050] S220d, set the queue length threshold Q th , the available transmission rate threshold R th , the maximum queuing delay D max , three weight factors w 1 , w 2 , w 3 , the comprehensive congestion index threshold C th , the comprehensive congestion index reference upper limit C max , the coding window maximum value W cmax , the pipeline calculation constant θ;

[0051] S220e, the current node monitors its own transmission queue length Q, available transmission rate R, and maximum queuing delay in real time

[0052] S220f, the current node calculates the comprehensive congestion index as an estimator of the congestion degree;

[0053] S220f, if the comprehensive congestion index C ≥ C th , then trigger the congestion control mechanism to reduce the coding window size and the number of pipelines. The congestion control mechanism is:

[0054] Set the coding window size to be reduced in the next transmission round to

[0055] Set the new W cmax to the reduced window size W c , and recover at a rate of doubling per transmission round; set the number of pipelines L = min(current number of pipelines, ).

[0056] Among them, the comprehensive congestion index reference upper limit is C max , the coding window maximum value is W cmax .

[0057] In a specific embodiment of the present invention, formulating a pipeline transmission strategy according to the estimated congestion degree in S200 includes:

[0058] S230a, the source node sets the degree distribution decision threshold P th1 and P th2 (P th1 <P th2 ), and the relay node sets the behavior decision threshold p th , C th ;

[0059] S230b, before the start of each transmission round, the source node calculates the end-to-end packet loss rate P e2e , and the calculation method is the product of the packet loss rates of each link P e2e =ΠPLR i ;

[0060] S230c, after receiving the encoded symbols from the previous node, the relay node reads the packet loss rate PLR next of the next-hop link and the comprehensive congestion degree C;

[0061] S230d, the source node determines whether P e2e <P th1 holds. If so, the formulated pipeline transmission strategy is the degree 1 distribution strategy, and the formulated pipeline transmission strategy is that no XOR encoding is required; if P th1 ≤P e2e <P th2 , the formulated pipeline transmission strategy is the robust arc wave distribution; if P e2e ≥P th2 , the formulated pipeline transmission strategy is the degree feedback strategy; the degree feedback strategy includes: construction phase one, construction phase two, and completion phase;

[0062] S230e, the relay node determines whether PLR next <pt h and C<Ct h holds. If it holds, the relay node formulates the pipeline transmission strategy as directly forwarding the encoded symbols; if PLR next ≥pt h or C≥C th , then the relay node formulates the pipeline transmission strategy as the strategy of decoding and forwarding the encoded symbols while decoding;

[0063] S230f, both the source node and the relay node readjust their own pipeline transmission strategies with a single transmission round as the period.

[0064] In a specific embodiment of the present invention, the strategy of decoding and forwarding the encoded symbols while decoding includes:

[0065] S230e1. When the source node adopts a degree-1 distribution and a robust arc wave distribution for transmission, refer to Figure 5 , the relay node forwards according to Policy 1, and the Policy 1 is:

[0066] When the relay node receives the coded packet for the first time, it initializes the matching source node and destination node. While continuing to forward each coded packet, it performs the operation of decoding first and then encoding; the relay node uses the newly initialized destination node to perform decoding according to the above transmission steps. If all source symbols are successfully recovered, it replies with the NOVER message, and continues to encode the source symbols after successful decoding using the source node; the source node that receives the NOVER message pauses sending coded symbols, and the source node or relay node that receives the OVER message immediately enters the next transmission round;

[0067] S230e2. When adopting the degree feedback strategy for transmission, refer to Figure 6 , the relay node forwards according to Policy 2, and the Policy 2 is:

[0068] In the first construction stage, the source node randomly selects input symbols for encoding and sends coded symbols according to a constant degree value of 2 until it receives the BU1 feedback from the next hop. After the feedback is processed, it does not continue to forward in the source direction, and then enters the second construction stage. The current node will only receive coded symbols with a degree value of 2; if the coded symbol contains only input symbols of one color and all are located in a single component, then ignore the symbol and do not continue to forward it to the nodes in the destination direction; if the coded symbol consists of all-white nodes from two different components, it means that the two components can be merged into one, and the coded symbol should be processed and the bipartite graph should be updated; continue to judge whether the size of the combined component reaches the largest connected component. If so, send the BU1 feedback and immediately enter the second construction stage; if the coded symbol consists of one black and one white node, the component containing the white node can be recovered and the bipartite graph should be updated; finally, forward the coded symbol to the next node; the meaning of a component is that as long as the decoder can currently know the result of the exclusive OR operation of two source symbols, these two source symbols will be connected, and the set of all connected source symbols is called a component. The size of a component refers to the number of source symbols in the component, and a single unknown source symbol is the smallest component with a size of 1; the largest connected component refers to the component with the largest size among all components; a component is considered recovered when any one source symbol in the component is known, then all source symbols in the component become known, that is, the component has been recovered; a bipartite graph refers to the set composed of all components and all known source symbols. The known source symbols in the bipartite graph are black, and the unknown source symbols are white;

[0069] S230e3. When the source node adopts the degree feedback strategy for transmission, refer to Figure 6 , the relay node forwards according to Policy 3, and the Policy 3 is:

[0070] In the second construction phase, the source node randomly selects input symbols for encoding and sends the encoded symbols according to a constant degree value of 1 until it receives the BU2 feedback from the next hop; after this feedback is processed, it does not continue to forward in the source direction and then enters the completion phase; in the second construction phase, the current node only receives encoded symbols with a degree value of 1 and continues to forward them in the destination direction; while decoding, the bipartite graph should be restored, and at the same time, it is checked whether the maximum connected component has been restored. If so, the BU2 feedback is sent and the completion phase is entered; at this time, if the decoding is completed, the NOVER feedback is sent to the source node, and at the same time, the corresponding source node is initialized to synchronize the transmission rounds of adjacent nodes.

[0071] S230e4, when the degree feedback strategy is adopted for transmission, refer to Figure 6 , the relay node forwards according to Strategy 4, and the Strategy 4 is:

[0072] If the OVER feedback is received in the second construction phase, the source node stops sending. After this feedback is processed, it should continue to forward in the source direction and then transfer to the next transmission round; if the NOVER is received, it stops sending, enters the suspended state, and continues to forward this feedback in the source direction.

[0073] S230e5, when the degree feedback strategy is adopted for transmission, refer to Figure 6 , the relay node forwards according to Strategy 5, and the Strategy 5 is:

[0074] In the completion phase, the source node randomly selects input symbols for encoding and sends the encoded symbols according to the calculated optimal degree value until it receives the FDB feedback, and this feedback does not continue to forward in the source direction. Then the current optimal degree value is updated and the sending continues, remaining in the completion phase; in the completion phase, the destination node receives the encoded symbols with the optimal degree value. If the encoded symbol only contains input symbols of one color and all are located in a single component, then this symbol is ignored and not continued to be forwarded to the nodes in the destination direction; if the encoded symbol consists of all-white nodes from two different components, this encoded symbol should be processed and the bipartite graph should be updated; then the decoding progress FDB is fed back and this symbol is continued to be forwarded to the nodes in the destination direction; if the number of white nodes in the encoded symbol is 1, then the bipartite graph is updated, the decoding progress FDB is fed back, and this encoded symbol is continued to be forwarded to the nodes in the destination direction; if the destination node as a relay node completes decoding, the NOVER feedback is sent to the source direction, and at the same time, the corresponding source node is initialized, and the transmission phase of the source node is set according to the decoding phase of the next hop; if the destination node as the destination node completes decoding, only the OVER feedback needs to be sent to the source direction and then enter the next transmission round.

[0075] S230e6, when the degree feedback strategy is adopted for transmission, refer toFigure 6 , the relay node forwards according to Policy 6, and the Policy 6 is:

[0076] If an OVER feedback is received during the completion phase, the source node stops sending. After this feedback is processed, it should continue to be forwarded in the source direction and then enter the next transmission round; if a NOVER is received, it stops sending, enters the suspended state, and continues to forward this feedback in the source direction.

[0077] In a specific embodiment of the present invention, the number of pipelines in the pipeline transmission strategy is dynamically adjusted according to the link utilization rate, and the adjustment process includes:

[0078] Set the current pipeline stage number L and the transmission round completion time T cycle , the time T for the feedback to be sent back to the source node ACK , the link utilization rate threshold U th ;

[0079] Define the number of pipeline stages as the number of encoding (decoding) modules used to simultaneously complete a certain flow on a certain node. For example, for the source node, if there are two encoders encoding and transmitting different messages belonging to the same flow at this time, it is called a two-stage pipeline at this time.

[0080] The source node calculates the link utilization rate according to the following formula

[0081] If U < U th , then add a new pipeline, if U = U th then do not change the number of pipelines, if U > U th then delete a pipeline.

[0082] In a specific embodiment of the present invention, the expected number of encoded symbols is limited in both the degree-1 distribution strategy, the robust arc wave distribution strategy, and the degree feedback strategy;

[0083] For the degree-1 distribution strategy, the expected number of encoded symbols is: where k is the total number of source symbols into which the byte block merged from the messages in its own message queue in the current transmission round is split; δ is the maximum value of the probability of the occurrence of the decoding interruption event; the decoding interruption event refers to the situation that before successful decoding, the decoder has no encoded symbol with a degree value of 1;

[0084] For the robust arc wave distribution strategy, the expected number of encoded symbols is: refers to an infinitesimal of a higher order than when k approaches infinity;

[0085] For the degree feedback strategy, during the construction phase, the expected number of degree-2 encoded symbols required is: The number of coded symbols of degree 1 is: In the completion phase, the number of coded symbols required to recover k source symbols is The total overhead is: E tr (k) = E(N comp (k)) + E(N 1 ) + E(N 2 ), where α is the ratio of the number of source symbols contained in the largest connected component in the bipartite graph at the end of the construction phase to the total number k of source symbols in the current transmission round; c is the average degree of the source symbols, that is, before the start of the completion phase, the average number of times each source symbol participates in forming coded symbols, and is obtained according to the formula α + e -ca = 1; P(i) is the probability that the event of advancing the decoding progress occurs for the newly coded symbol in the completion phase; the event of advancing the decoding progress means that when the proportion of the currently recovered source symbols reaches , among all the source symbols that make up the new coded symbol, only one or two source symbols are unknown to the decoder, and the remaining source symbols that make up the new coded symbol are all known.

[0086] In a specific embodiment of the present invention, referring to Figure 7 , in S200, the destination node recovers the original message from the received coded symbols through the transmission round, including:

[0087] The destination node continuously receives coded symbols and checks whether the transmission round numbers in the coded symbols match. If they do not match, it retransmits the OVER / NOVER information and discards the coded symbol; it decodes the matching coded symbols. If all source symbols are successfully recovered, it replies the OVER / NOVER information to the source node; the destination node assembles the source symbols into byte blocks and then splits them into original messages again according to the length of a single original message.

[0088] In a specific embodiment of the present invention, referring to Figure 8 , S300 includes:

[0089] S310, after the destination node finishes transmitting, it starts to release the connection. After the source node finishes data transmission, it prepares to release the connection, sends a DREQ message to the destination node indicating that the source node hopes to disconnect, and enters the DREQ_SENT state, waiting for the confirmation of the destination node;

[0090] S320, after the destination node receives the DREQ message from the source node, it confirms the request and starts to prepare to disconnect; the destination node sends a DREP message to the source node indicating agreement to disconnect, and enters the DREQ_RECEIVED state, waiting for further actions of the source node;

[0091] S330, After the source node receives the DREP information from the destination node, it performs the final step of connection release, sends a DCFM packet segment to the destination node to confirm the DREP information of the destination node, and informs the source node that it is ready to release all relevant resources and enters the WAIT_RELEASE state, waiting for the final release signal from the destination node;

[0092] S340, After the destination node receives the DCFM information from the source node, it confirms that the connection release process is nearly complete, sends a DREL message to the source node indicating that all resources have been released and the connection has been completely disconnected; the destination node enters the CLOSED state, ready to accept new connection requests or end the communication;

[0093] S350, After the source node receives the DREL message, it also enters the CLOSED state to complete the release of the communication connection.

[0094] The following further illustrates the effect of the present invention in combination with simulation experiments:

[0095] 1. Simulation experiment conditions:

[0096] The application platform for the simulation experiment is: The processor is a 32-core AMD Ryzen Threadripper PRO 5975WX 64-bit CPU with a main frequency of 3.6 GHz and a memory of 128 GB.

[0097] The software platform for the simulation experiment is: Windows10 operating system.

[0098] The network scenario for the simulation experiment is a space of 200km×100km, in which several network nodes are randomly distributed. Each node can communicate with the nodes within the transmission range. The movement model of the nodes adopts the random waypoint model, and the movement of each node is independent.

[0099] The simulation parameters are set as shown in Table 1

[0100] Table 1 Simulation parameter table

[0101] Maximum Power 31 dBm Path Loss Exponent 2 Receiver Sensitivity -89 dBm Signal Propagation Loss 20 dB Routing Protocol DSR MAC Protocol TDMA

[0102] 2. Simulation content and result analysis:

[0103] Simulation 1, Under the network scenario in Table 1, each mechanism in the present invention is respectively adopted, and compared with traditional TCP at different node moving speeds. Randomly select two nodes as the source and destination nodes respectively, and compare the impact of random packet loss on the transmission performance. The results are obtained by averaging the results of 10 simulations for each data point, and the results are as Figure 9 .

[0104] From Figure 9It can be seen that the transmission effect obtained by adopting the present invention for reliable transmission in a dynamic scenario is better. Due to frequent packet loss caused by route switching in TCP, the congestion window always remains at a low level, and the performance drops sharply. When the node moving speed reaches about 120 m / s, its effective throughput approaches zero; when only transmitting degree-1 symbols, without overly complex coding calculations in the case of slow node movement speed, the transmission effect is good, but as the node movement speed increases, insufficient coding gain is introduced, and the throughput drops sharply; when only adopting the robust arc wave distribution, since this degree distribution function is more suitable for a single-hop erasure channel with random packet loss, its performance in the UAV swarm network is not ideal, and it appears inflexible and has mediocre performance in long-distance transmission with high dynamicity; when only adopting the degree feedback mode for transmission, since this mode divides the fountain code into multiple stages and the interaction of feedback information is more frequent, it is not worth the loss when the packet loss probability is small, so it is more suitable as a transmission scheme to combat high packet loss rates; when the relay node only participates in forwarding, it will cause waste of transmission resources in the first half due to the routing failure of the unstable path in the second half, because the relay node cannot proxy the source node to continue sending, and retransmission can only rely on the source node, so the transmission efficiency is low; when only adopting a single pipeline, it always has to wait for the confirmation feedback of successful decoding to perform the next round of coding. Especially when the feedback is lost or in long-path transmission, it will cause the confirmation information to be delivered late, and the sending end wastes time waiting during this period, so the performance is poor. The present invention improves the transmission performance by detecting the state of the transmission path and selecting an appropriate transmission strategy at the appropriate time.

[0105] It should be noted that the terms "first" and "second" in the present invention are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0106] Although the present application has been described in conjunction with various embodiments herein, however, in the process of implementing the claimed present application, those skilled in the art can understand and achieve other variations of the disclosed embodiments by viewing the accompanying drawings, the disclosure content, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude a plurality of cases.

[0107] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for end-to-end reliable transmission supporting drone cluster swarm network, characterized in that: include: S100, in the connection establishment phase, the source node and the destination node establish a communication connection by sending messages to each other, and there are multiple relay nodes on the communication link; S200, in the transmission phase, the current node periodically intercepts messages from its own message queue according to the coding window, and encodes them in units of transmission rounds to obtain coding symbols; congestion control and pipeline transmission strategy are performed according to the estimated congestion level, and the coding symbols are transmitted to the next node according to the pipeline transmission strategy until they reach the destination node; The destination node recovers the original message from the received coded symbols through the transmission round; the current node is a source node or a relay node; S300, in the connection release phase, the source node and the destination node release the communication connection by sending messages to each other, thereby ending the transmission.

2. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 1 is characterized in that: S100 includes: S110, the source node sends a CREQ message to the destination node and enters the CREQ_SENT state, waiting for confirmation from the destination node, wherein the CREQ message carries a parameter set, indicating that the source node wishes to establish a connection; S120, after receiving the CREQ information from the source node, the destination node confirms the request and sends a CREP message to the source node, indicating that it agrees to establish a connection and initialize the transmission, and is ready to receive the coded symbols that are coming. The destination node enters the CREQ_RECEIVED state and waits for confirmation from the source node. S130, after receiving the CREP information of the destination node, the source node sends a CCFM message to confirm the CREP information of the destination node; the source node enters the ESTABLISHED state and starts the transmission phase; the destination node also enters the ESTABLISHED state after receiving the CCFM message and completes the connection establishment phase.

3. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 1 is characterized in that: In S200, the current node periodically intercepts messages from its own message queue according to the coding window, and encodes them in units of transmission rounds to obtain coding symbols; performs congestion control and formulates a pipeline transmission strategy according to the estimated congestion level, and transmits the coding symbols to the next node according to the pipeline transmission strategy until the destination node is reached, including: S210a, the source node continues to receive the original message and adds it to its own message queue, and the relay node receives the message transmitted by the previous node and stores it in its own message queue; S210b, the current node sets the coding window length in each transmission round, and determines whether the length of its own message queue is less than the coding window size within a time interval. If so, it fills it with all zero bytes until it is not less than the coding window size; if the message queue is empty, it enters the step of connection release; S210c, the current node takes out messages of the same size as the coding window from its own message queue, merges them into byte blocks, and splits the byte blocks into a plurality of source symbols according to the source symbol size; S210d, the current node resets the transmission number threshold, and uses the plurality of source symbols to encode to obtain coded symbols; each coded symbol is marked with the current transmission round sequence number and then compressed into a data packet; S210e, performing congestion control and formulating a pipeline transmission strategy according to the estimated congestion level, and sending the data packet to the next transmission node according to the pipeline transmission strategy until the number of transmissions reaches a threshold and then increasing the coding interval to continue sending; S210f, the current node monitors the feedback information. If the source node receives an OVER message and the relay node receives a NOVER message, it returns to S210a; if it receives a DFLT message, it returns to S210d.

4. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 3 is characterized in that: The congestion control according to the estimated congestion degree in S200 includes: S220a, any current node sets the time interval T as the statistical period and initializes the number of data packets N received within the time period T p (T) is 0, and the maximum sequence number P of the packets received within the nth and n-1th time intervals T is initialized. n and P n-1 is 0; S220b, any current node, whenever a data packet is received within the time interval T, will p (T) increments by 1 and updates P n is the maximum sequence number of the data packets received within the current time interval T; S220c, any current node, at the end of each time interval T, uses the formula Calculate the packet loss rate and use it as the reliability of the current link, then update P n-1 P n , initialize N p (T) is 0, which is used for the next update calculation; S220d, set the queue length threshold Q th , Available transmission rate threshold R th , maximum queuing delay D max , three weight factors w1, w2, w3, comprehensive congestion index threshold C th , Comprehensive congestion index reference upper limit C max , maximum value of the coding window W cmax , pipeline calculation constant θ; S220e, the current node monitors its own sending queue length Q, available transmission rate R, and maximum queuing delay in real time S220f, current node calculates comprehensive congestion index As an estimator of congestion; S220f, if the comprehensive congestion index C≥C th , then the congestion control mechanism is triggered to reduce the encoding window size and the number of pipelines. The congestion control mechanism is: Set the next transmission round to reduce the encoding window size to The new W cmax Set to the reduced window size W c , and recover at a rate that doubles with each transmission round; set the number of pipelines 5. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 4 is characterized in that: In S200, the pipeline transmission strategy is formulated according to the estimated congestion level, including: S230a, the source node sets the degree distribution decision threshold P th1 and P th2 (P th1 <P th2 ), the relay node sets the behavior decision threshold p th , C th ; S230b, the source node calculates the end-to-end packet loss rate P before each transmission round starts e2e , calculated as the product of the packet loss rate of each link P e2e =∏PLR i ; S230c, after receiving the coding symbol from the previous node, the relay node reads the packet loss rate PLR ​​of the next hop link next and the comprehensive congestion level C; S230d, the source node determines P e2e <P th1 Is it true? If so, the pipeline transmission strategy is formulated as the degree 1 distribution strategy, and the pipeline transmission strategy is formulated as no XOR encoding is required; if P th1 ≤P e2e <P th2 , formulate the pipeline transmission strategy as robust arc wave distribution; if P e2e ≥P th2 ,The pipeline transmission strategy is formulated as the degree feedback strategy; the degree feedback strategy includes: construction phase 1, construction phase 2 and completion phase; S230e, the relay node determines the PLR next <p th And C <C th Is it true? If so, the relay node formulates a pipeline transmission strategy to directly forward the coded symbols; if PLR next ≥p th or C ≥ C th , then the relay node formulates a pipeline transmission strategy of decoding and forwarding coded symbols at the same time; S230f, the source node and the relay node both readjust their own pipeline transmission strategies based on a single transmission round.

6. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 5 is characterized in that: The strategy of forwarding coded symbols while decoding includes: S230e1, when the source node adopts degree 1 distribution and robust arc wave distribution transmission, the relay node forwards according to strategy 1, and the strategy 1 is: When the relay node receives the coded packet for the first time, it will initialize the matching source node and destination node, and continue to forward each coded packet while performing the operation of decoding first and then encoding; the relay node uses the newly initialized destination node to decode according to the above transmission steps. If all source symbols are successfully recovered, it will reply with NOVER information and continue to use the source node to encode the source symbols after successful decoding; the source node that receives the NOVER information will stop sending coded symbols, and the source node or relay node that receives the OVER information will immediately enter the next transmission round; S230e2, when the transmission is carried out using the degree feedback strategy, the relay node forwards according to strategy 2, where strategy 2 is: In the first construction phase, the source node randomly selects input symbols with a constant degree of 2 for encoding and sends the encoded symbols until it receives BU1 feedback from the next hop. After the feedback is processed, it does not continue to forward to the source direction, and then enters the second construction phase. The current node will only receive the encoded symbol with a degree of 2; if the encoded symbol contains only input symbols of one color and all are in a single component, the symbol is ignored and not forwarded to the node in the destination direction; if the encoded symbol is composed of all-white nodes from two different components, it means that the two components can be merged into one, and the encoded symbol should be processed and the monopartite graph should be updated; continue to determine whether the size of the combined component reaches the maximum connected component. If so, send BU1 feedback and immediately enter the second construction phase; if the encoded symbol is composed of two nodes, one black and one white, the component containing the white node can be restored and the monopartite graph is updated; finally, continue to forward the encoded symbol to the next node; S230e3, when the source node adopts the degree feedback strategy for transmission, the relay node follows strategy 3, which is: In the second construction phase, the source node randomly selects input symbols according to a constant degree value of 1 to encode and send the encoded symbols until it receives BU2 feedback from the next hop; after the feedback is processed, it does not continue to forward to the source direction, and then enters the completion phase; in the second construction phase, the current node will only receive the encoded symbols with a degree value of 1 and continue to forward them to the destination direction; while decoding, the one-part graph should be restored, and at the same time, check whether the largest connected component is restored. If so, send BU2 feedback and enter the completion phase; at this time, if the decoding is completed, send NOVER feedback to the source node, and initialize the corresponding source node at the same time to synchronize the transmission rounds of adjacent nodes; S230e4, when the degree feedback strategy is adopted for transmission, the relay node follows strategy 4, which is: If an OVER feedback is received in the second construction phase, the source node stops sending. After the feedback is processed, it should continue to forward it to the source direction and then enter the next transmission round. If a NOVER is received, it stops sending, enters the suspended state, and continues to forward the feedback to the source direction. S230e5, when the degree feedback strategy is adopted for transmission, the relay node follows strategy 5, which is: In the completion phase, the source node randomly selects input symbols according to the calculated optimal degree value for encoding and sends the encoded symbols until it receives FDB feedback, and the feedback does not continue to be forwarded to the source direction, then updates the current optimal degree value and continues to send, and remains in the completion phase; in the completion phase, the destination node receives the encoded symbol with the optimal degree value. If the encoded symbol contains only input symbols of one color and all are located in a single component, the symbol is ignored and not forwarded to the node in the destination direction; if the encoded symbol is composed of all-white nodes from two different components, the encoded symbol should be processed and the one-part graph should be updated; then the decoding progress FDB is fed back, and the symbol is continued to be forwarded to the node in the destination direction; if the number of white nodes of the encoded symbol is 1, the one-part graph is updated, the decoding progress FDB is fed back, and the encoded symbol is continued to be forwarded to the node in the destination direction; if the destination node as a relay node completes decoding, NOVER feedback is sent to the source direction, and the corresponding source node is initialized at the same time, and the transmission phase of the source node is set according to the decoding phase of the next hop; if the destination node as a destination node completes decoding, it only needs to send OVER feedback to the source direction and then enter the next transmission round; S230e6, when the transmission is carried out using the degree feedback strategy, the relay node forwards according to strategy 6, where strategy 6 is: If OVER feedback is received during the completion phase, the source node stops sending. After the feedback is processed, it should continue to forward it toward the source and then enter the next transmission round. If NOVER is received, it stops sending, enters the suspended state, and continues to forward the feedback toward the source.

7. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 5 is characterized in that: The number of pipelines in the pipeline transmission strategy is dynamically adjusted according to link utilization, and the adjustment process includes: Set the current pipeline level L and the transmission round completion time T cycle , the time taken for feedback to be transmitted back to the source node is T ACK , link utilization threshold U th ; The source node calculates the link utilization rate according to the following formula: If U is satisfied th , then add a new pipeline, if U = U th The number of pipelines will not be changed if U>U th Then delete a pipeline.​ 8. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 5 is characterized in that: The expected number of coding symbols is limited in the degree 1 distribution strategy, the robust arc wave distribution strategy and the degree feedback strategy; For the degree 1 distribution strategy, the expected number of encoding symbols is: Where k is the total number of source symbols that are split into byte blocks from messages taken from its own message queue in the current transmission round; δ is the maximum value of the probability of a decoding interruption event allowed; a decoding interruption event means that before decoding is successful, the decoder has no coded symbols with a degree value of 1; For the robust arc wave distribution strategy, the expected number of coded symbols is: It means that when k tends to infinity, infinitesimals of higher order; For the degree feedback strategy, during the construction phase, the expected number of degree 2 coding symbols required is: The number of encoding symbols for degree 1 is: In the completion phase, the number of coded symbols required to recover k source symbols is The total cost is: E tr (k) = E(N comp (k))+E(N1)+E(N2), α refers to the ratio of the number of source symbols contained in the largest connected component in the one-part graph to the total number of source symbols k in the current transmission round at the end of the construction phase; c refers to the average degree of the source symbols; P(i) refers to the probability of the event that the new encoded symbols advance the decoding progress in the completion phase.

9. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 1 is characterized in that: In S200, the destination node recovers the original message from the received coded symbols through the transmission rounds including: The destination node continuously receives the coded symbols and checks whether the transmission round sequence number in the coded symbols matches. If not, the OVER / NOVER information is retransmitted and the coded symbol is discarded. The matching coded symbols are decoded. If all source symbols are successfully recovered, the OVER / NOVER information is replied to the source node. The destination node assembles the source symbols into byte blocks and splits them into original messages again according to the length of a single original message.

10. The end-to-end reliable transmission method supporting drone cluster swarm network according to claim 1, characterized in that: S300 includes: S310, the destination node starts to release the connection after completing the transmission. After the source node completes the data transmission, it is ready to release the connection and sends a DREQ message to the destination node, indicating that the source node wishes to disconnect the connection, and enters the DREQ_SENT state, waiting for the confirmation of the destination node; S320, after receiving the DREQ information from the source node, the destination node confirms the request and starts to prepare to disconnect; the destination node sends a DREP message to the source node, indicating that it agrees to disconnect, and enters the DREQ_RECEIVED state, waiting for further action from the source node; S330, after receiving the DREP information from the destination node, the source node performs the final step of connection release, sends a DCFM message segment to the destination node, confirms the DREP information of the destination node, and informs the source node that it is ready to release all related resources, and enters the WAIT_RELEASE state, waiting for the final release signal from the destination node; S340, after receiving the DCFM information from the source node, the destination node confirms that the connection release process is nearly completed, and sends a DREL message to the source node, indicating that all resources have been released and the connection has been completely disconnected; the destination node enters the CLOSED state, ready to accept new connection requests or end communication; S350, after receiving the DREL information, the source node also enters the CLOSED state and completes the release of the communication connection.

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