Multi-dimensional multiplexing MAC (Media Access Control) access method

Abstract

The invention discloses a multi-dimensional multiplexing MAC access method, which comprises the following steps: constructing an unmanned aerial vehicle wireless communication system which comprises an unmanned aerial vehicle network consisting of unmanned aerial vehicle nodes and a full duplex lift-off platform, and the unmanned aerial vehicle network adopts a clustering structure; in an unmanned aerial vehicle network establishment stage, a lift-off platform divides an unmanned aerial vehicle network into different resource regions according to the coverage range of the OAM beams in different modes by sending the OAM beams in different modes to the region where the unmanned aerial vehicle nodes are located; the OAM wave beam comprises a multi-mode synchronization frame which is used for performing inter-cluster synchronization and intra-cluster synchronization; in the communication transmission stage, different clusters communicate with a lift-off platform through OAM beams of corresponding modes, and nodes in the clusters communicate with each other in a time division multiplexing mode. In a network recombination stage, after monitoring a synchronization frame from a lift-off platform and determining a corresponding resource area, a newly added unmanned aerial vehicle node applies for entering a cluster to a cluster head node.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technology and relates to a multi-dimensional multiplexing media (Media Access Control, MAC) access method based on vortex orbital angular momentum (Orbital Angular Momentum, OAM) and time, aiming to improve the communication capacity and transmission efficiency of dense networks. Background Art

[0002] The widespread application of wireless communications has led to insufficient spectrum resources. To this end, technologies such as frequency division multiplexing, time division multiplexing, and space division multiplexing have been proposed one after another. However, the advent of the mobile Internet and big data era has made the demand for large-capacity and even ultra-large-capacity communications increasingly prominent.

[0003] Orbital angular momentum can be considered a new degree of freedom, serving as a carrier of data and information. Applying orbital angular momentum to communications involves modulating conventional signals within a specific frequency band into vortex signals carrying orbital angular momentum. Theoretically, a single carrier frequency can be expanded into an infinite number of vortex signals with the same frequency but varying orbital angular momentum. These vortex signals are orthogonal, with modal values ​​that can take on any integer value. They propagate across space without interfering with each other, facilitating the reuse of vortex beams. Therefore, the reuse of orbital angular momentum can theoretically increase the communication capacity of a system infinitely.

[0004] Faced with the future demands for ultra-high-capacity data transmission, traditional planar electromagnetic wave communication technologies face the dilemma of depleted spectrum resources. Vortex beams can transmit high-quality, high-capacity information over limited channel resources, improving communication capacity and spectral efficiency, and meeting the ultra-high-capacity requirements of future wireless communication systems. However, because traditional MAC protocols are based on traditional time and frequency dimensions, they are not well adapted for vortex communication systems. This not only reduces communication speeds but also fails to fully exploit the potential of orbital angular momentum. Summary of the Invention

[0005] The purpose of the present invention is to provide a multi-dimensional multiplexing MAC access method to solve the problems of difficult UAV network access and limited communication capacity.

[0006] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0007] A multi-dimensional multiplexing MAC access method, comprising:

[0008] Constructing a UAV wireless communication system, including a UAV network composed of UAV nodes and a full-duplex launch platform, wherein the UAV network adopts a cluster structure;

[0009] During the UAV network establishment phase, the launch platform sends OAM beams of different modes to the area where the UAV nodes are located, dividing the UAV network into different resource areas according to the coverage range of each OAM beam. The OAM beams contain multi-modal synchronization frames for inter-cluster synchronization and intra-cluster synchronization.

[0010] In the communication transmission phase, different clusters communicate with the launch platform using OAM beams of corresponding modes, and nodes within a cluster communicate through time division multiplexing.

[0011] During the network reorganization phase, the newly joined UAV node applies to the cluster head node for cluster entry after monitoring the synchronization frame from the launch platform and determining the corresponding resource area.

[0012] Furthermore, the launch platform sends OAM beams of different modes to the area where the drone nodes are located, dividing the drone network into different resource areas according to the coverage range of each mode OAM beam, including:

[0013] The launch platform HAP first sends OAM beams to cover the area where all UAV nodes are located, and divides the UAV network into different resource areas according to the coverage range of different modal OAM beams;

[0014] During the HAP's OAM beam transmission, all UAV nodes are in a listening state. The UAV nodes receive different synchronization frames from the HAP and parse the synchronization frames and the VT frames contained therein. The VT frames contain resource area identifiers to distinguish the communication areas of different clusters, thereby obtaining modal information, which includes the modal identifier of the resource area. The modal information then confirms the corresponding resource area based on the modal information and uses a random backoff mechanism to request access to the UAV network. The corresponding node identity information is generated according to the network access order. The first UAV node to access the resource area automatically becomes the cluster head node of the corresponding cluster in the resource area and broadcasts the cluster head information. The cluster structure is generated after the remaining UAV nodes in the same resource area join the cluster, thus completing the establishment of the UAV network.

[0015] Furthermore, the frame structure of the UAV network is divided into synchronization frames and mission frames. The synchronization frames are used to confirm resource areas and calibrate alignment, and the mission frames are used to transmit data packets. The mission frames are further divided into OAM gaps and time gaps. In the time gaps, time division multiple access is used for intra-cluster communication; in the OAM gaps, mode division multiple access is used for inter-cluster communication between cluster heads.

[0016] Furthermore, the resource area covered by the vortex beam with a modal value of L is defined as C L , the upper limit of the number of drone nodes it carries is m L, all UAV nodes are uniquely determined by two parameters, L and K. L is the modal value of the OAM beam corresponding to the resource area where the UAV node is located, and K is the sequence of access to the resource area.

[0017] Furthermore, the synchronization process during the drone network establishment phase includes:

[0018] The OAM beam sent by the HAP contains multi-mode synchronization frames; the multi-mode synchronization frames include inter-cluster synchronization frames and intra-cluster synchronization frames;

[0019] Inter-cluster synchronization: At the arrival of each transmission cycle, all drone nodes continuously listen to the synchronization frame from the HAP and align the drone nodes between clusters by parsing the inter-cluster synchronization frame;

[0020] Intra-cluster synchronization: The cluster head node first broadcasts the intra-cluster synchronization frame within the cluster, which contains control information and time slot allocation table. Each node in the cluster listens and parses it. After parsing the control information and time slot allocation table received from the cluster head node, the cluster node first calibrates and aligns according to the intra-cluster synchronization frame, and then determines whether there is a transmission task in the current transmission phase. If the drone node does not receive a transmission task, it will resynchronize and enter a dormant state and wait for the next synchronization.

[0021] Furthermore, during the process of the drone node accessing the drone network:

[0022] First, after synchronization, the UAV nodes confirm the corresponding resource areas in advance based on the acquired modal information. Then, different inter-cluster OAM transmission channels are divided according to different resource areas. UAV nodes in the same resource area belong to the same cluster.

[0023] Within the same cluster, nodes in the cluster divide independent time slots for each node in the access order according to the allocation information in the time slot allocation table, which represents different intra-cluster time transmission channels;

[0024] The nodes in the cluster that receive the transmission task transmit the task and exchange information with the cluster head node in an orderly manner within their respective time slots; the cluster head node listens and collects the data sent by the nodes in the cluster during the time slots, and concentrates on communicating with the HAP during the OAM slots to send the data of its cluster.

[0025] Furthermore, when the UAV node hears the clustering information through the inter-cluster synchronization frame, it immediately uses the random backoff mechanism to send an access request to the HAP, waits for the request to be confirmed, and then accesses the UAV network until all UAV nodes join the UAV network;

[0026] After waiting for all drone nodes to join the network, the cluster head node immediately broadcasts the cluster head information; after continuously sending the information for a preset time, it enters the listening state and waits for other drone nodes to apply to join the cluster after hearing the cluster head information;

[0027] If the applying drone node and the cluster head node that sends the cluster head information are located in the same resource area, the cluster head node confirms the cluster entry application; if they are not in the same resource area, the cluster head node rejects the cluster entry application; drone nodes that fail to successfully enter the cluster continue to listen and wait for new cluster head information; while clustering, the cluster head node generates a list of nodes in the cluster according to the order in which the drone nodes enter the cluster until all drone nodes complete the cluster entry process.

[0028] Furthermore, during the communication transmission phase:

[0029] Intra-cluster communication: In TDMA mode, nodes within a cluster transition from a dormant phase to a listening phase, receiving and parsing the time slot allocation table and task information from the cluster head node. The time slot allocation table is planned based on the node ID. After parsing, the nodes within the cluster determine whether there is a transmission task. If not, they enter a dormant state and wait for the next round of transmission tasks to start. If there is a transmission task, they determine the transmission task and wait for the arrival of their respective time slots for data transmission. After completing the transmission, the node enters a dormant state and waits for the next round of tasks to start.

[0030] Inter-cluster communication: During the intra-cluster communication phase, the cluster head node listens to the transmission information of all nodes within the cluster, aggregates the information after the transmission of each node within the cluster is completed, and then switches to the OAM beam with the corresponding modal value to transmit with the HAP. The cluster head nodes communicate with each other using the HAP as a relay.

[0031] Furthermore, during the network reorganization phase:

[0032] After a new UAV node is started, it continuously listens for synchronization frames from the HAP. When the new UAV node receives the synchronization frame, it parses the VT frame in the synchronization frame to obtain the modal information of the current coverage area and confirms the corresponding resource area in advance based on the modal information. At the same time, the synchronization frame also contains the cluster head node information of each cluster. After parsing the synchronization frame to obtain information, the new node can initiate a cluster entry request to the cluster head node of its cluster. After receiving the request, the cluster head node determines whether the number of nodes in the current cluster has reached the load limit. If not, it agrees to the cluster entry request.

[0033] When the cluster head node does not receive the return information from a cluster node for several consecutive cycles, it determines that the cluster node has left the UAV network, deletes its ID from the cluster node list, and updates the UAV network topology information;

[0034] If the original cluster head node fails and exits the UAV network, the next node in the cluster will become the cluster head node according to the ID list.

[0035] A terminal device comprises a processor, a memory and a computer program stored in the memory; when the processor executes the computer program, the multi-dimensional multiplexing MAC access method is implemented.

[0036] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the multi-dimensional multiplexing MAC access method is implemented.

[0037] Compared with the prior art, the present invention has the following technical features:

[0038] Compared to traditional MAC communication methods based on single time-division multiplexing, this method leverages the characteristics of vortex beams to add modal multiplexing to dense UAV networks, breaking through the single dimension and achieving multi-dimensional resource reuse. Inter-cluster networks use vortex beams of different modes for independent communication, reducing resource congestion, while intra-cluster networks ensure the reliability of communication links through TDMA. This method can effectively expand communication capacity and has promising application prospects in improving the communication efficiency of dense UAV networks in small areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A small-area dense UAV network communication system model based on vortex mode;

[0040] Figure 2 It is the frame structure of the UAV node;

[0041] Figure 3 This is an OAM resource allocation time slot diagram in one embodiment of the present invention;

[0042] Figure 4 A time slot allocation sequence diagram according to an embodiment of the present invention;

[0043] Figure 5 A flowchart of the network access process and cluster structure generation process of drone nodes in one embodiment of the present invention;

[0044] Figure 6 This is a specific flow chart of the UAV network communication transmission stage in one embodiment of the present invention. DETAILED DESCRIPTION

[0045] The dense deployment of drone nodes in a small-area unmanned aerial vehicle (UAV) network expands the communication capacity of the UAV network, but also increases the complexity of the network structure and signaling overhead. The present invention provides a MAC layer access method based on vortex orbital angular momentum and time two-dimensional multiplexing. By dividing the UAV network into a two-level topological cluster structure, the inter-cluster network uses vortex beams of different modes for independent communication to reduce spectrum resource congestion. The intra-cluster network uses time division multiplexing (TDMA) to ensure the reliability of the communication link. This effectively solves the problems of difficult UAV network access and limited communication capacity, and realizes multi-dimensional resource reuse.

[0046] The communication system model targeted by the method of the present invention is as follows: Figure 1 As shown. Limited communication capacity is a typical problem faced by drone networks, and due to the high density distribution of drone terminals in small-area drone networks, a single network access protocol based on time resources cannot solve this problem. The MAC layer, as a sublayer of the data link layer, is the connection hub between the network layer and the physical layer, and has attracted much attention in the research and design of drone communication networking systems. Therefore, the present invention considers adding a new dimension of multiplexing to meet the growing communication needs, and performs joint multiplexing by superimposing the new resource dimension of modality on the basis of traditional time resources to improve the wireless communication transmission capacity.

[0047] Consider a dense UAV communication network consisting of a full-duplex High Access Point (HAP) and a large number of half-duplex UAVs (UAVs) nodes. The UAV nodes are densely dispersed approximately evenly in the service area, and the HAP is located directly above the service area. The UAV nodes are responsible for collecting and transmitting information, while the HAP is responsible for establishing inter-network connections and assisting UAV network communication, providing a channel for information interaction. Therefore, the HAP needs to achieve both uplink and downlink transmission to meet the communication capacity and transmission efficiency of the dense network. Full-duplex technology requires more advanced transceiver antennas to achieve this. Therefore, here, only the HAP is set as a UAV node with full-duplex communication technology.

[0048] The present invention provides a multi-dimensional multiplexing MAC access method, comprising:

[0049] Constructing a UAV wireless communication system, including a UAV network composed of UAV nodes and a full-duplex launch platform, wherein the UAV network adopts a cluster structure;

[0050] During the UAV network establishment phase, the launch platform sends OAM beams of different modes to the area where the UAV nodes are located, dividing the UAV network into different resource areas according to the coverage range of each OAM beam. The OAM beams contain multi-modal synchronization frames for inter-cluster synchronization and intra-cluster synchronization.

[0051] In the communication transmission phase, different clusters communicate with the launch platform using OAM beams of corresponding modes, and nodes within a cluster communicate through time division multiplexing.

[0052] During the network reorganization phase, the newly joined UAV node applies to the cluster head node for cluster entry after monitoring the synchronization frame from the launch platform and determining the corresponding resource area.

[0053] 1. Drone network establishment phase.

[0054] 1.1 Synchronization and resource allocation.

[0055] For UAV networks in a small area, the HAP equipped with a uniform circular array (UCA) sends signals to the UAV network through OAM beams.

[0056] (1) Resource regional division.

[0057] The HAP first sends a non-zero mode OAM beam to cover the area where all drone nodes are located, and divides the drone network into different resource areas according to the coverage range of different mode OAM beams. Assuming that in one embodiment, the radius of the drone network is small, the three-mode vortex beam can cover the area where all drone networks are located, so the entire drone network is divided into three resource areas C1, C2, and C3; where the mode value is defined as L (L∈{1,2,3}), and the resource area covered by the vortex beam with the mode value L is defined as C L (L∈{1, 2, 3}).

[0058] Assume that each resource region C L The upper limit of the number of drone nodes carried is m L All drone nodes are uniquely determined by two parameters, L and K. L is the modal value of the OAM beam corresponding to the resource area where the node is located, and K is the order of accessing the resource area (K∈{1,2,3,…,m L});like Figure 1 As shown in FIG, a specific UAV network-oriented UCA is mounted on the HAP as an antenna for transmitting and receiving OAM beams, and the array faces the UAV network area.

[0059] During the HAP's OAM beam transmission, all drone nodes are in a listening state. The drone nodes receive different synchronization frames from the HAP and parse the synchronization frames and the VT frames contained therein to obtain modal information. The modal information includes the modal identifier of the resource area, that is, the modal value of the OAM beam corresponding to the resource area. Therefore, the drone node determines to join the cluster corresponding to the resource area based on the obtained modal value. The corresponding resource area is then confirmed based on the modal information and a random backoff mechanism is used to request access to the drone network. The corresponding node identity information (Identity Document, ID) is generated according to the network access order. The first drone node to access the resource area automatically becomes the cluster head node of the corresponding cluster in the resource area and broadcasts the cluster head information, waiting for the remaining drone nodes in the same resource area to join the cluster to complete the cluster structure generation. This completes the establishment of the drone network and generates a secondary network architecture containing multiple clusters.

[0060] The frame structure of the UAV network is divided into synchronization frames and mission frames. The synchronization frames are used to confirm resource areas and calibrate alignment, and the mission frames are used to transmit data packets. The mission frames are further divided into OAM gaps and time gaps. In the time gaps, time division multiple access (TDMA) is used for intra-cluster communication. In the OAM gaps, mode division multiple access (MDMA) is used for communication between cluster heads, that is, inter-cluster communication.

[0061] (2) Synchronization.

[0062] The OAM beam sent by the HAP contains multimodal synchronization frames to ensure that UAV nodes are strictly aligned with the transmission start position. The multimodal synchronization frames include VT frames, inter-cluster synchronization frames, and intra-cluster synchronization frames. VT frames contain resource area identifiers to distinguish the communication areas of different clusters. Inter-cluster synchronization frames contain clustering information, which includes the number of clusters in the UAV network, the cluster head node of each cluster, and the total number of intra-cluster nodes.

[0063] Inter-cluster synchronization: At the arrival of each transmission cycle, all drone nodes continuously listen to the synchronization frame from the HAP and complete the alignment of drone nodes between clusters during the parsing of the inter-cluster synchronization frame.

[0064] Intra-cluster synchronization: The cluster head node first broadcasts the intra-cluster synchronization frame within the cluster, which contains control information and time slot allocation table. Each node in the cluster listens and parses it. After parsing the control information and time slot allocation table received from the cluster head node, the cluster node first calibrates and aligns according to the intra-cluster synchronization frame, and then determines whether there is a transmission task in the current transmission phase. If the drone node does not receive a transmission task, it will resynchronize and enter a dormant state and wait for the next synchronization.

[0065] Among them, control information refers to all information except useful data information, including time synchronization information, node identification, request / response information, etc. to ensure that all nodes in the cluster are strictly aligned with the transmission start time; the time slot allocation table contains the transmission tasks of each drone node and the time channel division information of the nodes in the cluster.

[0066] (3) Channel allocation.

[0067] When a UAV node accesses the UAV network, it first obtains clustering information based on the inter-cluster synchronization frame, accesses different inter-cluster channels according to the requirements of the clustering information, and then allocates different intra-cluster channels to each node in the cluster. The specific steps are as follows:

[0068] In step 2.1, after synchronization, the UAV nodes first confirm the corresponding resource area in advance based on the modal information parsed in the VT frame; then, different inter-cluster OAM transmission channels are divided according to different resource areas. UAV nodes in the same resource area belong to the same cluster.

[0069] In step 2.2, within the same cluster, the nodes in the cluster divide independent time slots for each node in the access order according to the allocation information in the time slot allocation table, which represent different intra-cluster time transmission channels.

[0070] In step 2.3, the nodes in the cluster that receive the transmission task transmit the task and exchange information with the cluster head node in an orderly manner within their respective time slots; the cluster head node listens and collects the data sent by the nodes in the cluster during the time slots, and concentrates on communicating with the HAP to send the data of its cluster during the OAM slots.

[0071] from Figure 3 As can be seen in the two-dimensional channel partitioning method below, each row represents a cluster, and each small square represents the transmission channel for each node. Each node that successfully joins the network has a corresponding intra-cluster transmission time slot on the intra-cluster channel. Within the intra-cluster transmission channel, nodes in the same cluster not only communicate directly to exchange information, but also need to periodically send broadcast messages to maintain various information lists.

[0072] 1.2 Drone node access stage.

[0073] The frame structure diagram of the MAC protocol based on vortex mode and time division multiplexing can be found in Figure 4 The clustering information of OAM beams with different modal values ​​is distinguished by the inter-cluster synchronization frame carrying OAM information; T L ∈{1, 2, 3} represents different resource regions C L The timeslot length of the frame carrying OAM information.

[0074] (1) The drone node joins the network.

[0075] When the UAV node hears the clustering information, it immediately uses the random backoff mechanism to send an access request to the HAP, waits for the request to be confirmed, and then joins the UAV network until all UAV nodes join the UAV network. During the network access process, the UAV node is assigned a node ID of LK, where L∈{1,2,3}, K∈{1,2,3,…,m L}(L depends on the resource area where the cluster is connected, K is the order of accessing the cluster, m L For this resource area C L The first connected drone node (i.e., the node with K=1) automatically becomes the cluster head node under the clustering of the resource area.

[0076] (2) Cluster structure generation.

[0077] After waiting for all drone nodes to join the network, the cluster head node immediately broadcasts the cluster head information, such as node i; after continuously sending for a certain period of time, it enters the listening state and waits for other drone nodes to apply to join the cluster after hearing the cluster head information.

[0078] If the applying drone node and the cluster head node that sends the cluster head information are located in the same resource area, the cluster head node confirms the cluster entry application, such as node j; if they are not in the same resource area, the cluster head node rejects the cluster entry application, such as node k; drone nodes that fail to successfully enter the cluster continue to listen and wait for new cluster head information; while clustering, the cluster head node generates a list of nodes in the cluster according to the order in which the drone nodes enter the cluster until all drone nodes complete the cluster entry process.

[0079] 2. Communication transmission stage.

[0080] After the node list in the cluster is generated, it is assumed that the HAP and the drone nodes have completed time synchronization, and then enter the communication transmission phase, see Figure 6 ,Clustered network communication can be divided into two states: inter-cluster and intra-cluster, and this stage is carried out periodically.

[0081] 2.1 Intra-cluster communication.

[0082] In TDMA mode, the nodes in the cluster change from the dormant stage to the listening stage, receiving and parsing the time slot allocation table and task information from the cluster head node; the time slot allocation table is planned according to the node ID; after parsing, the nodes in the cluster determine whether there is a transmission task. If not, they enter the dormant state and wait for the next round of transmission tasks to start, such as node 2 in the cluster; if there is a transmission task, they clarify the transmission task and wait for the arrival of their respective time slots for data transmission, such as node 1 and node m in the cluster; after completing the transmission, the node enters the dormant state and waits for the next round of tasks to start.

[0083] 2.2 Inter-cluster communication.

[0084] During the intra-cluster communication phase, the cluster head node listens to the transmission information of all intra-cluster nodes, waits for the transmission of the intra-cluster nodes to be completed, summarizes the information, and then switches to the OAM beam of the corresponding modal value to transmit with the HAP; the cluster head nodes communicate with each other through the HAP as a relay. Because the cluster head nodes are in different resource areas, each cluster of drone networks can interact with the HAP at the same time.

[0085] 3. Network reorganization stage.

[0086] 3.1 New drone node added.

[0087] After the new drone node is started, it continuously listens to the synchronization frame from the HAP. When the new drone node receives the synchronization frame, it parses the VT frame in the synchronization frame to obtain the modal information of the current coverage area and confirms the corresponding resource area in advance based on the modal information. At the same time, the synchronization frame also contains the cluster head node information of each cluster. After the new node parses the synchronization frame to obtain the information, it can initiate a cluster entry request to the cluster head node of its cluster. After receiving the request, the cluster head node determines whether the number of nodes in the current cluster has reached the load limit. If not, it agrees to the cluster entry request.

[0088] 3.2 The old drone node exits.

[0089] When the cluster head node does not receive feedback information from a cluster node for multiple consecutive cycles, it determines that the cluster node has left the UAV network, deletes its ID from the cluster node list, and updates the UAV network topology information.

[0090] 3.3 Cluster head node replacement

[0091] If the original cluster head node fails and exits the UAV network, the next node in the cluster will become the cluster head node according to the ID list, and so on.

[0092] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A multi-dimensional multiplexing MAC access method, characterized in that: include: Constructing a UAV wireless communication system, including a UAV network composed of UAV nodes and a full-duplex launch platform, wherein the UAV network adopts a cluster structure; During the UAV network establishment phase, the launch platform sends OAM beams of different modes to the area where the UAV nodes are located, dividing the UAV network into different resource areas according to the coverage range of each OAM beam. The OAM beams contain multi-modal synchronization frames for inter-cluster synchronization and intra-cluster synchronization. In the communication transmission phase, different clusters communicate with the launch platform using OAM beams of corresponding modes, and nodes within a cluster communicate through time division multiplexing. During the network reorganization phase, the newly joined UAV node monitors the synchronization frame from the launch platform and determines the corresponding resource area, and then applies to the cluster head node to join the cluster.

2. The multi-dimensional multiplexing MAC access method according to claim 1, characterized in that: The launch platform sends OAM beams of different modes to the area where the drone nodes are located. According to the coverage range of each mode OAM beam, the drone network is divided into different resource areas, including: The launch platform HAP first sends OAM beams to cover the area where all UAV nodes are located, and divides the UAV network into different resource areas according to the coverage range of different modal OAM beams; During the HAP's OAM beam transmission, all UAV nodes are in a listening state. The UAV nodes receive different synchronization frames from the HAP and parse the synchronization frames and the VT frames contained therein. The VT frames contain resource area identifiers to distinguish the communication areas of different clusters, thereby obtaining modal information, which includes the modal identifier of the resource area. The modal information then confirms the corresponding resource area based on the modal information and uses a random backoff mechanism to request access to the UAV network. The corresponding node identity information is generated according to the network access order. The first UAV node to access the resource area automatically becomes the cluster head node of the corresponding cluster in the resource area and broadcasts the cluster head information. The cluster structure is generated after the remaining UAV nodes in the same resource area join the cluster, thus completing the establishment of the UAV network.

3. The multi-dimensional multiplexing MAC access method according to claim 1, wherein: The frame structure of the UAV network is divided into synchronization frames and mission frames. The synchronization frames are used to confirm resource areas and calibrate alignment, and the mission frames are used to transmit data packets. The mission frames are further divided into OAM gaps and time gaps. In the time gaps, time division multiple access is used for intra-cluster communication; in the OAM gaps, mode division multiple access is used for inter-cluster communication between cluster heads.

4. The multi-dimensional multiplexing MAC access method according to claim 1, wherein: The synchronization process during the drone network establishment phase includes: The OAM beam sent by the HAP contains multi-mode synchronization frames; the multi-mode synchronization frames include inter-cluster synchronization frames and intra-cluster synchronization frames; Inter-cluster synchronization: At the arrival of each transmission cycle, all drone nodes continuously listen to the synchronization frame from the HAP and align the drone nodes between clusters by parsing the inter-cluster synchronization frame; Intra-cluster synchronization: The cluster head node first broadcasts the intra-cluster synchronization frame within the cluster, which contains control information and time slot allocation table. Each node in the cluster listens and parses it. After parsing the control information and time slot allocation table received from the cluster head node, the cluster node first calibrates and aligns according to the intra-cluster synchronization frame, and then determines whether there is a transmission task in the current transmission phase. If the drone node does not receive a transmission task, it will resynchronize and enter a dormant state and wait for the next synchronization.

5. The multi-dimensional multiplexing MAC access method according to claim 1, wherein: During the process of UAV node accessing the UAV network: First, after synchronization, the UAV nodes confirm the corresponding resource areas in advance based on the acquired modal information. Then, different inter-cluster OAM transmission channels are divided according to different resource areas. UAV nodes in the same resource area belong to the same cluster. Within the same cluster, nodes in the cluster divide independent time slots for each node in the access order according to the allocation information in the time slot allocation table, which represents different intra-cluster time transmission channels; The nodes in the cluster that receive the transmission task transmit the task and exchange information with the cluster head node in an orderly manner within their respective time slots; the cluster head node listens and collects the data sent by the nodes in the cluster during the time slots, and concentrates on communicating with the HAP during the OAM slots to send the data of its cluster.

6. The multi-dimensional multiplexing MAC access method according to claim 1, characterized in that: When the UAV node hears the clustering information through the inter-cluster synchronization frame, it immediately uses the random backoff mechanism to send an access request to the HAP, waits for the request to be confirmed, and then accesses the UAV network until all UAV nodes join the UAV network; After waiting for all drone nodes to join the network, the cluster head node immediately broadcasts the cluster head information; after continuously sending the information for a preset time, it enters the listening state and waits for other drone nodes to apply to join the cluster after hearing the cluster head information; If the applying UAV node and the cluster head node that sends the cluster head information are located in the same resource area, the cluster head node confirms the cluster entry application; If they are not in the same resource area, the cluster head node will reject the cluster entry application; The drone nodes that have not successfully joined the cluster continue to listen and wait for new cluster head information; while clustering, the cluster head node generates a list of nodes in the cluster according to the order in which the drone nodes joined the cluster until all drone nodes complete the clustering process.

7. The multi-dimensional multiplexing MAC access method according to claim 1, characterized in that: During the communication transmission phase: Intra-cluster communication: In TDMA mode, nodes within a cluster transition from a dormant phase to a listening phase, receiving and parsing the time slot allocation table and task information from the cluster head node. The time slot allocation table is planned based on the node ID. After parsing, the nodes within the cluster determine whether there is a transmission task. If not, they enter a dormant state and wait for the next round of transmission tasks to start. If there is a transmission task, they determine the transmission task and wait for the arrival of their respective time slots for data transmission. After completing the transmission, the node enters a dormant state and waits for the next round of tasks to start. Inter-cluster communication: During the intra-cluster communication phase, the cluster head node listens to the transmission information of all nodes within the cluster, aggregates the information after the transmission of each node within the cluster is completed, and then switches to the OAM beam with the corresponding modal value to transmit with the HAP. The cluster head nodes communicate with each other using the HAP as a relay.

8. The multi-dimensional multiplexing MAC access method according to claim 1, characterized in that: During the network reorganization phase: After a new UAV node is started, it continuously listens for synchronization frames from the HAP. When the new UAV node receives the synchronization frame, it parses the VT frame in the synchronization frame to obtain the modal information of the current coverage area and confirms the corresponding resource area in advance based on the modal information. At the same time, the synchronization frame also contains the cluster head node information of each cluster. After parsing the synchronization frame to obtain information, the new node can initiate a cluster entry request to the cluster head node of its cluster. After receiving the request, the cluster head node determines whether the number of nodes in the current cluster has reached the load limit. If not, it agrees to the cluster entry request. When the cluster head node does not receive the return information from a cluster node for several consecutive cycles, it determines that the cluster node has left the UAV network, deletes its ID from the cluster node list, and updates the UAV network topology information; If the original cluster head node fails and exits the UAV network, the next node in the cluster will become the cluster head node according to the ID list.

9. A terminal device comprising a processor, a memory, and a computer program stored in the memory; characterized in that: When the processor executes the computer program, the multi-dimensional multiplexing MAC access method according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium storing a computer program; wherein: When the computer program is executed by a processor, the multi-dimensional multiplexing MAC access method according to any one of claims 1 to 8 is implemented.

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