A method for unmanned aerial vehicle networking data link communication

Abstract

This invention discloses a data link communication method for UAV networking, relating to the field of UAV networking data link communication technology. The method includes: each UAV node obtaining a media access control layer (MAC) contention state vector through backoff state perception statistics; fusing the physical layer nominal rate with the contention state vector to calculate a composite link cost metric; flooding the link state message across the entire network and maintaining a network-wide composite link cost topology database; the source node performing shortest path calculation with the composite link cost metric as weight, selecting the path with the lowest total cost to forward data frames; and continuously monitoring changes in the contention state vector to determine whether route updates are needed. This invention, by incorporating the MAC contention backoff state into routing decisions, solves the problem of routing deviation caused by the mismatch between physical layer transmission capacity and MAC channel contention behavior, effectively improving data transmission efficiency in high-dynamic, multi-rate UAV networking.

Description

Technical Field

[0001] This invention relates to the field of UAV networking data link communication technology, and in particular to a UAV networking data link communication method. Background Technology

[0002] Data link communication in UAV networking is a key supporting technology for collaborative task execution by UAV swarms. In self-organizing networks composed of multiple UAVs, the high-speed movement of nodes leads to drastic changes in network topology, resulting in highly dynamic link states. Furthermore, due to differences in flight attitude, relative distance, and channel environment, the communication links of different UAVs often exhibit multiple transmission rates simultaneously. To ensure the reliability and timeliness of data transmission, routing protocols need to dynamically adjust forwarding strategies based on network conditions.

[0003] Existing technologies generate network-wide link rate and packet loss rate information based on optimized link-state routing protocols. By evaluating information transmission time and packet loss rate, they automatically select the most suitable routing strategy for the current network state and adaptively select the routing path with the least latency to perform data forwarding, aiming to improve information delivery rate and reduce network overhead in highly dynamic and multi-rate environments.

[0004] However, this method primarily bases its routing decisions on the physical layer nominal rate and end-to-end statistical parameters, failing to adequately consider the channel contention behavior of the media access control layer. In highly dynamic UAV swarms, when the network employs carrier sense multiple access (CSMI) mechanisms, if a low-speed UAV at a distant edge continuously occupies the channel and transmits long data frames, surrounding UAV nodes on high-speed links, despite having strong physical layer transmission capabilities, are forced into a prolonged backoff waiting process due to detected channel congestion. In this situation, the so-called minimum-latency path selected by the adaptive strategy based on the link nominal rate is actually limited by the channel occupancy time of the low-speed node, resulting in a significant increase in the actual end-to-end latency of the path. Existing methods fail to perceive the mismatch between the contention backoff state of the media access control layer and the physical layer transmission capability, causing routing decisions to deviate from the actual optimal solution in complex channel contention environments, thus severely restricting network transmission efficiency and resource utilization. Summary of the Invention

[0005] The purpose of this invention is to provide a data link communication method for UAV networking, which solves the problem in the prior art where the effective throughput of the selected path is limited and the end-to-end latency is significantly increased due to the lack of awareness of the contention backoff state of the media access control layer under the carrier sense multiple access mechanism.

[0006] To achieve the above objectives, the present invention provides a data link communication method for unmanned aerial vehicle (UAV) networking, comprising the following steps: Step 100: Each UAV node perceives the backoff state through the Media Access Control Layer and counts the Media Access Control Layer contention state vector within a preset time window, including the proportion of channel occupancy time, the average number of backoff waiting slots, and the average number of collisions. Step 200: Each UAV node fuses the physical layer nominal rate of the link between itself and its neighboring nodes with the media access control layer contention state vector to calculate the composite link cost metric for each neighboring node. Step 300: Each UAV node floods the link status message containing the composite link cost metric across the entire network and maintains a composite link cost topology database for the entire network locally. Step 400: The source node performs shortest path calculation based on the network composite link cost topology database, using the composite link cost metric as the weight, and uses the sum of the composite link cost metrics of each link as the total path cost. The path with the minimum end-to-end total path cost is selected as the main data forwarding path. Step 500: The source node forwards the data frame along the selected path. At the same time, each node continuously monitors the change in the local media access control layer contention state vector. When the change exceeds the preset trigger threshold, a route update is triggered.

[0007] Furthermore, in step 200, the composite link cost metric balances the accuracy of routing decisions with the lightweight nature of system operation, and is calculated in two cases: Lightweight computing: If and ,in To set the preset high load threshold, perform the following calculation formula: ; in, For lightweight computing, neighbor-oriented nodes The composite link cost metric; The basic backoff slot duration specified for carrier sense multiple access (CSMI) mechanism; For neighbor-oriented nodes The reference transmission delay; The average number of backoff waiting slots; This represents the proportion of time the channel is occupied. Accurate calculation: If or Immediately switch to the following calculation formula: ; in, To accurately calculate neighbor-oriented nodes The composite link cost metric; Preset collision penalty coefficient; This represents the average number of collisions.

[0008] Furthermore, in step 200, to avoid frequent switching of computation methods in critical states, the following rule is used to implement degradation: if the current node uses accurate computation, in continuous... Within each observation window, and , To delay the exit from the lower bound, the node is downgraded from accurate calculation back to lightweight calculation.

[0009] Furthermore, in step 100, the preset time window adopts a moving average window, and the length of the moving average window is adaptively adjusted according to the node movement speed: when the node movement speed exceeds a preset speed threshold, the moving average window length is shortened to a preset minimum window length; when the node movement speed is lower than the preset speed threshold, the moving average window length is extended to a preset maximum window length; the preset minimum window length is less than the preset maximum window length.

[0010] Furthermore, the flooding and diffusion of link status messages in step 300 adopts an incremental update mechanism: the link status message carries a monotonically increasing sequence number, and the receiving node judges the age of the link status message based on the sequence number, and only forwards the link status message whose sequence number is greater than the latest sequence number of the same publishing node recorded locally; each node publishes a new link status message when the change of any component in the media access control layer contention state vector exceeds a preset trigger threshold, and publishes link status messages periodically according to a preset heartbeat cycle.

[0011] Furthermore, in step 300, the process of constructing the full-network composite link cost topology database is as follows: Initialization phase: After the node starts up and the physical layer and media access control layer are ready, before constructing the link state message of this node for the first time, an empty network-wide composite link cost topology database is created in local memory, including: publishing point identifier, latest sequence number, latest update timestamp, composite link cost metric between the publishing node and each neighboring node, and aging timer. After this node has calculated the set of composite link cost metrics for each neighbor, it inserts the link state message of this node and the aging timer as the first database entry. Reception and Update Phase: Whenever a link-state message is received from a neighboring node, a comparison of the sequence number is performed. For link-state messages determined to be new, the following steps are executed to update the database: Extract the publisher node identifier from the new message; use the publisher node identifier as an index to search for the corresponding database entry in the network-wide composite link cost topology database; if a database entry for the current publisher node exists in the database, and the sequence number of the new message is greater than the latest sequence number recorded in the current database entry, then the link-state message of the new message is used to overwrite the current link-state message, and the aging timer is reset to zero and restarted; if a database entry for the current publisher node does not exist in the database, then a new database entry is created using the publisher node identifier of the new message as an index; the link-state message of the new message is filled into the corresponding fields, and an aging timer is created for the current database entry and started counting; if the sequence number of the new message is not greater than the latest sequence number recorded in the current database entry, then it is determined to be an expired message and discarded, and the database does not perform any update operations. Aging and Deletion Phase: The database maintenance module of each node checks the aging timers of all database entries at fixed intervals. When the aging timer count of any database entry exceeds the preset aging timeout threshold, the publishing node is determined to be invalid and the database entry and all its associated fields are deleted from the database.

[0012] Furthermore, step 400 also includes a backup path pre-calculation step: when the source node executes step 400, it simultaneously calculates the backup data forwarding path with the second smallest end-to-end composite cost and stores it in the local forwarding table; when an intermediate node on the primary data forwarding path triggers a route update due to a change in contention state, the source node temporarily switches to the backup data forwarding path to forward data frames, and resumes primary path forwarding after the primary path route update is completed.

[0013] Furthermore, step 400 also includes an edge node identification step: the source node counts the number of paths in the candidate forwarding path set for each node in the entire network that serve as intermediate forwarding nodes, and marks nodes with a number of paths lower than a preset edge threshold as edge nodes; in the path selection in step 400, a preset stability penalty weight is added to the total path cost of the path passing through the edge node before participating in the shortest path calculation.

[0014] Furthermore, step 500 also includes a long frame fragmentation management step: when it is detected that the composite link cost metric of a neighboring node exceeds a preset high cost threshold and the channel occupancy time ratio of the neighboring node exceeds a preset occupancy threshold, the node is determined to be a high channel occupancy node, and its upstream node performs fragmentation processing on the data frame to be forwarded to the node, splitting the data frame into multiple subframes with a length not exceeding the preset maximum fragment length and sending them in batches in sequence.

[0015] Furthermore, step 500 also includes a network partition detection and recovery step: when the source node cannot find a reachable path to the target node within a preset number of consecutive detections in the network-wide composite link cost topology database, a network partition is determined to have occurred, a delay-tolerant forwarding mode is initiated, the data frames to be sent are temporarily stored in a local buffer queue, and a network partition notification message is broadcast to the entire network; when the target node is detected to be reachable again after the network-wide composite link cost topology database is updated, the delay-tolerant forwarding mode is exited, a new path is selected according to step 400, and the temporarily stored data frames in the local buffer queue are forwarded to the target node in sequence.

[0016] Therefore, the present invention employs the above-mentioned UAV networking data link communication method, which has the following beneficial effects: 1. By fusing the media access control layer contention state vector with the physical layer nominal rate into a composite link cost metric, the method solves the technical problem that the existing routing mechanism only relies on the physical layer nominal rate and fails to detect the mismatch between the media access control layer contention backoff state and the physical layer transmission capacity. This method accurately reflects the actual end-to-end latency, automatically amplifies the link cost of low-speed, high-occupancy nodes, and enables the route to bypass highly contentious links. 2. Based on the adaptive switching between lightweight computing and accurate computing modes according to network state, the contradiction between computing power overhead and routing accuracy in highly dynamic scenarios is resolved. This results in low CPU utilization and control overhead when the channel environment is good; and sensitive capture of communication quality degradation trends when channel competition is fierce, achieving oscillation-resistant and precise scheduling. 3. By implementing data frame fragmentation for high-channel-occupancy nodes, the problem of low-speed nodes continuously occupying the channel with long frames, causing neighboring high-speed nodes to be forced to back off for a long time and resulting in severely limited effective throughput, is solved. This significantly reduces the waiting time of other high-priority control commands in the network and prevents system communication paralysis caused by individual nodes widening their backoff windows. 4. By setting up an independent high-priority queue for routing control messages and configuring smaller contention window parameters, the problem of routing update messages being blocked by data frames and causing routing lag in high-contention environments is solved, ensuring real-time synchronization of topology information and significantly reducing forwarding interruptions and packet loss caused by control message lag.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a flowchart of a UAV networking data link communication method according to the present invention; Figure 2 This is a flowchart of the long frame fragmentation management and transmission process of the present invention. Detailed Implementation

[0019] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely illustrates selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0020] Please see Figure 1 A method for unmanned aerial vehicle (UAV) networking data link communication includes the following steps: Step 100, Media Access Control Layer Backoff State Awareness: Step 100 uses the media access control layer backoff event as the data source, and outputs the media access control layer contention state vector of this node after statistical calculation. Step 100 further includes steps 101 to 103.

[0021] Step 101, collect data within the preset time window. The three types of media access control layer event counts: cumulative duration of channel being in an occupied state This refers to the cumulative duration during which carrier sensing detects a busy channel; the total number of backoff slots that this node waits for from its initial transmission attempt to gain a transmission opportunity on the channel. and the total number of sending attempts by this node The number of collisions that occurred during the sending attempts. Step 101 output includes , , , The collection results.

[0022] Step 102: Calculate the media access control layer contention state vector based on the acquisition results of step 101. , It consists of the following three components: (1) Channel occupancy time ratio The calculation formula is: ; in, This represents the proportion of channel occupancy time, with a value range of [value missing]. ; The cumulative duration during which the channel is occupied; This is a preset time window.

[0023] (2) Average number of retreat waiting slots The calculation formula is: ; in, The average number of backoff waiting slots, with a value range of [value missing]. real numbers; This represents the total number of backoff slots that this node has waited for from its first transmission attempt until it gains the opportunity to transmit through the channel. Total number of attempts sent for this node.

[0024] (3) Average number of collisions The calculation formula is: ; in, The average number of collisions, with a value range of [value missing]. real numbers; This represents the number of collisions that occurred during the sending attempts.

[0025] The above three components together describe the intensity of competition in the wireless channel where this node is located within the current time window, and together constitute the media access control layer contention state vector. .

[0026] Step 103, Adaptively adjust the moving average window length based on node movement speed: Each node obtains its current movement speed through a global navigation satellite system or inertial navigation sensor. Adjust the time window according to the following two situations. : (1) When Exceeding the preset speed threshold At that time, Shorten to the preset minimum window length This is to accelerate the response speed to changes in channel contention status; (2) When Below the preset speed threshold At that time, Extend to the preset maximum window length To improve statistical stability and reduce the interference of random jitter on the contention state vector of the media access control layer; in , and Determined by system parameter configuration. After step 103 is completed, the updated preset time window is output. Step 101 is used for the next statistical period.

[0027] Step 200, Calculation of composite link cost metric: Step 200 uses the media access control layer contention state vector and the physical layer reports of the current node and each neighboring node. The physical layer nominal rate of the link is the input, and the output is a set of composite link cost metrics. Step 200 further includes steps 201 to 202.

[0028] Step 201, Calculate the reference transmission delay: Calculate the neighbor-oriented delay using the ratio of the standard reference frame length to the physical layer nominal rate. The baseline transmission delay is calculated using the following formula: ; in, The standard reference frame length is configured uniformly for the system; For the current node and its neighboring nodes The physical layer nominal rate; For neighbor-oriented nodes The baseline transmission delay.

[0029] Step 202: Calculate the composite link cost metric. To balance the accuracy of routing decisions with the lightweight nature of system operation, an adaptive switching logic based on network state quantization is designed, including the following two scenarios: (1) Lightweight calculation: If and ,in To reduce computational complexity, the node determines that the current channel contention environment is in an "orderly backoff, conflict-free" state based on a preset high load threshold, and performs the following calculation formula: ; in, For lightweight computing, neighbor-oriented nodes The composite link cost metric; The basic backoff slot duration specified for the carrier sense multiple access (CSMI) mechanism is determined by the system parameter configuration; when hour, This indicates that the link is actually unavailable due to continuous channel occupancy, and the routing calculation will automatically avoid this link; when When it is large, A significant increase indicates that the contribution of backoff waiting time to path delay is not negligible; (2) Accurate calculation: If or If a node determines that the current link has entered a "contention-damage sensitive" state, it immediately switches to the following calculation formula to correct the routing cost using a collision penalty term. The calculation formula is as follows: ; in, To accurately calculate neighbor-oriented nodes The composite link cost metric; The preset collision penalty coefficient is determined by the system parameter configuration and is used to reflect the additional contribution of collision retransmission to the actual link delay.

[0030] (3) To avoid frequent switching of calculation methods (ping-pong effect) in critical states, if continuous Within each observation window ( Average number of collisions And the proportion of channel occupancy time , To delay the exit from the lower bound, the node is downgraded from accurate calculation back to lightweight calculation.

[0031] It should be noted that both lightweight computation and accurate computation generate results oriented towards neighbor nodes. Composite link cost metric The set of composite link cost metrics for each neighbor node is called the composite link cost metric set. .

[0032] Lightweight computing's input parameters only include the channel occupancy rate and the average backoff waiting slot count. These parameters can be directly reported by the physical layer carrier sense hardware via registers, offering microsecond-level real-time performance and extremely low CPU overhead. However, lightweight computing cannot detect data collisions and packet loss caused by hidden terminals or dense concurrency in non-saturated states. Accurate calculations further include the average number of collisions as input parameters. The statistics for the average number of collisions rely on software maintenance of the acknowledgment timeout timer and retransmission counter, accurately reflecting the intensity of collisions in link layer transmissions. However, its side effect is the introduction of millisecond-level statistical lag and additional interrupt handling overhead. If the channel is clean for a long period (…), Continuously calling for accurate calculations during this process will cause the computing power of the drone's embedded processor to idle ineffectively, and occasional single collisions may cause unnecessary changes in routing costs, triggering network-wide routing oscillations. Therefore, it is necessary to separately judge and calculate the composite link cost metric.

[0033] Step 300: Flooding and propagation of link state messages and maintenance of the network-wide composite link cost topology database: Step 300 takes the set of composite link cost metrics as input, constructs link state messages, floods them across the entire network, and simultaneously maintains a network-wide composite link cost topology database locally, outputting the network-wide composite link cost topology database maintained locally by each node. Step 300 further includes steps 301 to 303.

[0034] Step 301: Construct and publish link state messages: The link state message consists of the following fields: publisher node identifier, sequence number, timestamp, and a set of composite link cost metrics between the publisher node and each neighbor node; the sequence number monotonically increases each time a new message is published, and the timestamp records the time when the message is generated.

[0035] Step 302: The receiving node determines the age of the message based on the sequence number and updates the network-wide composite link cost topology database. After receiving the link status message, each node determines the age of the message based on the publisher node identifier and the sequence number. If the received sequence number is greater than the latest sequence number of the same publisher node already recorded locally, it is determined to be a new message, written into the local network-wide composite link cost topology database, and forwarded to neighboring nodes. Otherwise, it is determined to be an expired message and discarded, and no longer forwarded. Through the above incremental update mechanism, the number of link status messages propagating in the network is positively correlated with the magnitude of routing status changes, and control overhead is automatically reduced when the link status is stable.

[0036] It should be noted that the network-wide composite link cost topology database includes the publisher node identifier, the latest sequence number, the most recent update timestamp, the set of composite link cost metrics between the publisher node and each neighbor node, and the aging timer.

[0037] It should also be noted that each node maintains an independent aging timer, with the preset duration being the aging timeout threshold. Each time the entry is updated due to receiving a new message, the aging timer is reset to zero and starts counting again. If no valid link status message is received from the publishing node within the aging timeout threshold, the node is determined to have left the network partition or failed, and the entry and all its associated fields are deleted from the network-wide composite link cost topology database.

[0038] The construction process of the network-wide composite link cost topology database is as follows: (1) Initialization phase: After the node starts up and the physical layer and media access control layer are ready, before constructing the node's link state message for the first time, an empty network-wide composite link cost topology database is created in local memory, including: publisher identifier, latest sequence number, most recent update timestamp, composite link cost metric between the publisher node and each neighbor node, and aging timer. After the node has calculated the set of composite link cost metrics for each neighbor, it inserts the node's link state message and aging timer as the first database entry.

[0039] (2) Reception and Update Phase: Whenever a link state message is received from a neighboring node, the sequence number is compared between old and new messages according to step 302. For link state messages determined to be new messages, the following steps are performed to update the database: Extract the publishing node identifier from the new message, and use the publishing node identifier as an index to search for the corresponding database entry in the whole network composite link cost topology database; If a database entry for the currently publishing node exists in the database, and the sequence number of the new message is greater than the latest sequence number recorded in the current database entry, then the link status message of the new message will overwrite the current link status message, and the aging timer will be reset to zero and the timing will restart. If the database does not yet contain a database entry for the currently publishing node (i.e., the first time the link status message of this node is received), a new database entry is created using the publishing node identifier of the new message as the index; the link status message of the received message is filled into the corresponding fields, and an aging timer is created for the current database entry and starts counting; If the sequence number of a new message is not greater than the latest sequence number of the same publishing node already recorded locally, it is determined to be an expired message and discarded according to step 302, and the database does not perform any update operation.

[0040] (3) Aging and Deletion Phase: The database maintenance module of each node checks the aging timer of all database entries at a fixed period. When the aging timer count of any database entry exceeds the preset aging timeout threshold, the publishing node is determined to be invalid and the database entry and all its associated fields are deleted from the database.

[0041] Step 303: Determine the triggering conditions for publishing link status messages, including the following two cases: (1) When the media access control layer of this node competes for the state vector The change in any component exceeds a preset trigger threshold. When a significant change in the contention state occurs, a new link state message is immediately constructed and published to ensure that the entire network is promptly synchronized. It should be noted that the entire network refers to the set of all reachable drone nodes that are currently within the same network partition, connected by multi-hop relay relationships within the wireless transmission range, with this node as the root.

[0042] (2) Each node periodically publishes link status messages according to the preset heartbeat cycle in order to maintain the timeliness of the network composite link cost topology database when the nodes have not experienced significant changes in competitive status for a long time.

[0043] Step 400, Shortest path calculation and data forwarding path selection: Step 400 takes the entire network composite link cost topology database as input, performs shortest path calculation by the source node, selects the path with the minimum end-to-end composite cost as the primary data forwarding path, pre-calculates backup data forwarding paths, and outputs the primary data forwarding path and backup data forwarding paths. Step 400 further includes steps 401 to 402.

[0044] The source node is the drone node that initially generates the data frame to be sent and initiates the routing process in a specific data transmission task.

[0045] Step 401: Perform shortest path calculation and select the primary data forwarding path and backup data forwarding path: The source node uses the composite link cost metric of each link in the network composite link cost topology database. Using edge weights, the shortest path algorithm is used to calculate the optimal path from this node to the target node; the sum of the cost metrics of each link composite link is used as the total path cost, and the path with the smallest end-to-end total path cost is selected as the primary data forwarding path; while calculating the primary data forwarding path, the backup data forwarding path with the second smallest end-to-end total path cost is also calculated, and both the primary data forwarding path and the backup data forwarding path are stored in the local forwarding table for use in step 500 during route update.

[0046] Step 402, identify edge nodes and add stability penalty weights: The source node counts the number of paths from each node in the network composite link cost topology database as intermediate forwarding nodes in the candidate forwarding path set. ,Will Below the preset edge threshold Nodes that pass through edge nodes are marked as edge nodes; for candidate paths that pass through edge nodes, a preset stability penalty weight is added to their total path cost. Then, it participates in the total path cost comparison to reduce the dependence of route selection on highly dynamic edge nodes and reduce the number of route updates caused by frequent link interruptions at edge nodes; among which and Determined by system parameter configuration.

[0047] Step 500: Data frame forwarding, real-time monitoring, and route update. Step 500 takes the main data forwarding path output in step 400 as input, performs data frame forwarding, continuously monitors the media access control layer contention state vector, triggers route updates when necessary, and outputs data frames delivered to the target node via the forwarding path. Step 500 further includes steps 501 to 505.

[0048] Step 501: The source node forwards the data frame hop-by-hop along the main data forwarding path; during the forwarding process, each node continuously transmits the current media access control layer contention state vector. Competition for state vector with the media access control layer when the link state message was last published Compare: If any component and The absolute value of the difference between the corresponding components exceeds the preset trigger threshold. If the competition status changes significantly, the composite link cost metric is immediately updated and step 300 is executed, which in turn triggers step 400 to re-select a route.

[0049] Step 502: During the route update, if the intermediate node is temporarily unable to complete forwarding due to a change in the contention state of the primary data forwarding path, the source node automatically switches to the backup data forwarding path pre-calculated in step 400 to forward the data frame; after the primary path route update is completed, the source node resumes forwarding along the primary data forwarding path to reduce the data interruption time during the route update.

[0050] It should be noted that route update refers to the complete process in which, when the contention state of the media access control layer changes significantly, causing the currently used data forwarding path to be no longer optimal or unavailable, the relevant nodes in the network re-execute steps 300-400, and finally, each node recalculates its local forwarding table based on the updated network composite link cost topology database and achieves consistency in forwarding paths.

[0051] Step 503, as follows Figure 2 As shown, performing long frame fragmentation management on nodes with high channel occupancy includes the following two sub-steps: (1) Detecting high-channel-occupancy nodes: When a neighboring node is detected Composite link cost metric Exceeding the preset high cost threshold And the proportion of channel occupancy time of the neighboring node. Exceeding the preset occupancy threshold If the node is in high channel occupancy, it is determined that the node is a high channel occupancy node; otherwise, the complete data is sent directly.

[0052] (2) Perform data frame fragmentation: The upstream node of the node with high channel occupancy performs fragmentation processing on the data frame to be forwarded to this node, splitting the data frame into fragments with a length not exceeding the preset maximum fragment length. Multiple subframes of bits are transmitted sequentially in batches; each subframe independently competes for the channel at the Media Access Control layer, and the channel occupancy time for a single frame does not exceed [a certain duration]. This reduces the duration of a single channel occupation by the node, thereby reducing the backoff pressure on neighboring nodes; among which , and Determined by system parameter configuration.

[0053] Step 504: Set up a high-priority sending queue for routing control messages: Each node sets up an independent high-priority sending queue for routing control messages (including link status messages and network partition notification messages); the contention window parameter of the high-priority sending queue is smaller than the contention window parameter of the data frame sending queue, so that the routing control messages have priority in the channel contention and ensure the real-time performance of routing status information.

[0054] Specifically, routing control messages are set to high priority, while other messages are set to low priority. Two independent data frame transmission queues are established: a high-priority queue and a low-priority queue. When the MAC (Media Access Control) layer receives a frame to be sent from the upper layer, it determines the frame type based on the frame type field: if it is a routing control message, it is inserted at the end of the high-priority queue; otherwise, it is inserted at the end of the low-priority queue.

[0055] When the channel is idle and a node is ready to send the next frame, the MAC layer first checks the high-priority queue: If the high-priority queue is not empty, a frame is taken from the head of the high-priority queue and sent. If the high-priority queue is empty, a frame is taken from the head of the low-priority queue and sent.

[0056] A strict priority scheduling strategy is adopted, and high-priority queues always receive services before low-priority queues.

[0057] Step 505, Network Partition Detection and Delay-Tolerant Forwarding; When a drone swarm is performing a wide-area search mission, if one drone flies out of the main swarm's communication range and loses its multi-hop connection with the source node, the source node's routing protocol may not know whether this is a physical partition or a temporary link fluctuation, and it may continue to attempt to send data frames. Therefore, network partition detection and latency-tolerant forwarding are performed, including the following two scenarios: (1) When the source node cannot find a reachable path to the target node within a preset number of consecutive detections in the composite link cost topology database of the whole network, it is determined that a network partition has occurred; at this time, the source node starts the delay-tolerant forwarding mode, temporarily stores the data frame to be sent in the local buffer queue, and broadcasts the network partition notification message to the whole network. (2) After step 300 updates the network composite link cost topology database, if the target node is detected to be reachable again, exit the delay-tolerant forwarding mode, reselect the path according to step 400, and forward the data frames temporarily stored in the local buffer queue to the target node in order.

[0058] When a drone swarm's network topology splits into multiple uncommunicating independent partitions due to node movement, the system automatically detects partition events and switches to a latency-tolerant forwarding mode to prevent data frames from being invalidally discarded during unreachable periods. Once the partitions are restored, the system automatically restores regular routes and sends back cached data, achieving a "store-wait-carry-forward" intermittent communication capability.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for unmanned aerial vehicle networking data link communication, characterized in that, Includes the following steps: Step 100: Each UAV node perceives the backoff state through the Media Access Control Layer and counts the Media Access Control Layer contention state vector within a preset time window, including the proportion of channel occupancy time, the average number of backoff waiting slots, and the average number of collisions. Step 200: Each UAV node fuses the physical layer nominal rate of the link between itself and its neighboring nodes with the media access control layer contention state vector to calculate the composite link cost metric for each neighboring node. Step 300: Each UAV node floods the link status message containing the composite link cost metric across the entire network and maintains a composite link cost topology database for the entire network locally. Step 400: The source node performs shortest path calculation based on the network composite link cost topology database, using the composite link cost metric as the weight, and uses the sum of the composite link cost metrics of each link as the total path cost. The path with the minimum end-to-end total path cost is selected as the main data forwarding path. Step 500: The source node forwards the data frame along the selected path. At the same time, each node continuously monitors the change in the local media access control layer contention state vector. When the change exceeds the preset trigger threshold, a route update is triggered.

2. The unmanned aerial vehicle networking data link communication method of claim 1, wherein, In step 200, the composite link cost metric balances the accuracy of routing decisions with the lightweight nature of system operation, and is calculated in two cases: Lightweight computing: If and ,in To set the preset high load threshold, perform the following calculation formula: ； in, For lightweight computing, neighbor-oriented nodes The composite link cost metric; The basic backoff slot duration specified for carrier sense multiple access (CSMI) mechanism; For neighbor-oriented nodes The reference transmission delay; The average number of backoff waiting slots; This represents the proportion of time the channel is occupied. Accurate calculation: if or , switch immediately to the following calculation formula: ； wherein, to accurately calculate a composite link cost metric value for a neighbor node facing the middle of the link; is a preset collision penalty coefficient; is an average number of collisions.

3. The UAV networking data link communication method according to claim 2, characterized in that, The following rules are used to implement the degradation in step 200 to avoid frequent computation mode switching in critical states: if the current node uses accurate computation, in the consecutive observation windows, and , is the hysteresis exit lower limit, the node is degraded from accurate computation to lightweight computation.

4. The unmanned vehicle networking data link communication method of claim 1, wherein, In step 100, the preset time window adopts a moving average window, and the length of the moving average window is adaptively adjusted according to the node moving speed: when the node moving speed exceeds the preset speed threshold, the length of the moving average window is shortened to the preset minimum window length. When the node's movement speed is lower than the preset speed threshold, the moving average window length is extended to the preset maximum window length; the preset minimum window length is less than the preset maximum window length.

5. The unmanned vehicle networking data link communication method of claim 1, wherein, In step 300, the flooding and diffusion of link status messages adopts an incremental update mechanism: the link status message carries a monotonically increasing sequence number, and the receiving node judges the age of the link status message based on the sequence number, and only forwards the link status message with a sequence number greater than the latest sequence number of the same publishing node that has been recorded locally. When the change in any component of the contention state vector in the media access control layer exceeds a preset trigger threshold, each node publishes a new link state message and periodically publishes link state messages according to a preset heartbeat cycle.

6. The UAV networking data link communication method according to claim 1, characterized in that, In step 300, the construction process of the whole network composite link cost topology database is as follows: Initialization phase: After the node starts up and the physical layer and media access control layer are ready, before constructing the link state message of this node for the first time, an empty network-wide composite link cost topology database is created in local memory, including: publishing point identifier, latest sequence number, latest update timestamp, composite link cost metric between the publishing node and each neighboring node, and aging timer. After this node has calculated the set of composite link cost metrics for each neighbor, it inserts the link state message of this node and the aging timer as the first database entry. Reception and Update Phase: Whenever a link-state message is received from a neighboring node, a comparison of the sequence number is performed. For link-state messages determined to be new, the following steps are executed to update the database: Extract the publisher node identifier from the new message; use the publisher node identifier as an index to search for the corresponding database entry in the network-wide composite link cost topology database; if a database entry for the current publisher node exists in the database, and the sequence number of the new message is greater than the latest sequence number recorded in the current database entry, then the link-state message of the new message is used to overwrite the current link-state message, and the aging timer is reset to zero and restarted; if a database entry for the current publisher node does not exist in the database, then a new database entry is created using the publisher node identifier of the new message as an index; the link-state message of the new message is filled into the corresponding fields, and an aging timer is created for the current database entry and started counting; if the sequence number of the new message is not greater than the latest sequence number recorded in the current database entry, then it is determined to be an expired message and discarded, and the database does not perform any update operations. Aging and Deletion Phase: The database maintenance module of each node checks the aging timers of all database entries at fixed intervals. When the aging timer count of any database entry exceeds the preset aging timeout threshold, the publishing node is determined to be invalid and the database entry and all its associated fields are deleted from the database.

7. The UAV networking data link communication method according to claim 1, characterized in that, Step 400 also includes a backup path pre-calculation step: when the source node executes step 400, it simultaneously calculates the backup data forwarding path with the second smallest end-to-end composite cost and stores it in the local forwarding table; when an intermediate node on the primary data forwarding path triggers a route update due to a change in contention state, the source node temporarily switches to the backup data forwarding path to forward data frames, and resumes primary path forwarding after the primary path route update is completed.

8. The UAV networking data link communication method according to claim 1, characterized in that, Step 400 also includes an edge node identification step: the source node counts the number of paths in the candidate forwarding path set for each node in the entire network that serve as intermediate forwarding nodes, and marks nodes with a number of paths lower than a preset edge threshold as edge nodes; in the path selection in step 400, a preset stability penalty weight is added to the total path cost of the path passing through the edge node before participating in the shortest path calculation.

9. A UAV networking data link communication method according to claim 1, characterized in that, Step 500 also includes a long frame fragmentation management step: when it is detected that the composite link cost metric of a neighboring node exceeds a preset high cost threshold and the channel occupancy time ratio of the neighboring node exceeds a preset occupancy threshold, the node is determined to be a high channel occupancy node, and its upstream node performs fragmentation processing on the data frame to be forwarded to the node, splitting the data frame into multiple subframes with a length not exceeding the preset maximum fragment length and sending them in batches in sequence.

10. A UAV networking data link communication method according to claim 1, characterized in that, Step 500 also includes a network partition detection and recovery step: when the source node cannot find a reachable path to the target node within a preset number of consecutive detections in the network-wide composite link cost topology database, a network partition is determined to have occurred, a delay-tolerant forwarding mode is initiated, the data frames to be sent are temporarily stored in a local buffer queue, and a network partition notification message is broadcast to the entire network; when the target node is detected to be reachable again after the network-wide composite link cost topology database is updated, the delay-tolerant forwarding mode is exited, a new path is selected according to step 400, and the temporarily stored data frames in the local buffer queue are forwarded to the target node in sequence.

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