A cluster head election method for a directional communication-based satellite-free unmanned aerial vehicle network

Abstract

The application discloses a cluster head election method of a satellite navigation-free unmanned aerial vehicle network based on directional communication, and comprises the following steps: a slow node scans aerial nodes at a current wave position in a wave position polling mode and sends a scanning frame; if there is an aerial node at the current wave position, the aerial node sends a response frame to the slow node after receiving the scanning frame, and the slow node records the response frame after receiving the response frame; the slow node continues to scan aerial nodes at a next wave position in a wave position polling mode and sends a scanning frame; if there is no aerial node at the current wave position, the slow node cannot receive the response frame, continues to scan aerial nodes at the next wave position in a wave position polling mode and sends a scanning frame; until all wave positions are scanned, the slow node elects a cluster head according to the recording result and sends cluster head information to all aerial nodes in the form of a notification frame. The application can realize unmanned aerial vehicle cluster head election in the case of satellite navigation-free unmanned aerial vehicles and the case of mixed satellite navigation-free unmanned aerial vehicles.

Description

Technical Field

[0001] The present invention belongs to the technical field of unmanned aerial vehicle (UAV) self-organizing network communication, and in particular relates to a cluster head recommendation method for a satellite-free UAV network based on directional communication. Background Art

[0002] With the continuous advancement and development of drone technology, its application scenarios are no longer limited to a single drone, but are developing towards self-organizing and collaborative ad hoc networks.

[0003] In existing technologies, drone positioning and control are primarily achieved through base stations or satellite navigation systems. Once a drone can determine the exact coordinates of a target node and perceive its own posture, it can easily determine its position. However, in certain situations, such as when satellite navigation signals are intentionally jammed and become unreliable, or in environments without navigation signals, drone positioning cannot be achieved through base stations or satellite navigation systems, making drone positioning unreliable.

[0004] Therefore, in the environment of drone swarm operations, providing a drone networking method that does not rely on satellite navigation systems has become a difficult problem that needs to be overcome in this field. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a cluster head recommendation method for a satellite-free UAV network based on directional communication. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a cluster head recommendation method for a satellite-free UAV network based on directional communication, comprising:

[0007] The slow node scans the air node at the current wave position in a wave position polling manner and sends a scan frame;

[0008] If there is an aerial node at the current wave position, the aerial node receives the scan frame and sends a response frame to the slow node. After receiving the response frame, the slow node records it. The slow node continues to scan the aerial node at the next wave position in a wave position polling manner and sends a scan frame.

[0009] If there is no air node at the current wave position, the slow node continues to scan the air node at the next wave position in a wave position polling manner and sends a scan frame;

[0010] Until all wave positions are scanned, the slow node elects a cluster head based on its recorded results and sends the cluster head information to all air nodes in the form of a notification frame;

[0011] The aerial node performs self-verification to determine whether it is the cluster head.

[0012] Optionally, there are n wave positions, the time slots for the slow node to send scan frames are n, the time slots for receiving response frames are n, and the time slots for sending notification frames are x, where x represents the number of air nodes;

[0013] The time slot for slow nodes to elect cluster heads is 2n+x;

[0014] Each time slot includes a data phase and a protection phase. The data phase is 1.5T and the protection phase is 1T. T = T t +T s +T r , T t =a / b, T s =c / d, T r ≈T t , T t represents the sending delay, a represents the data length, b represents the sending rate, T s represents the propagation delay, c represents the maximum distance between the slow node and the air node, d represents the electromagnetic propagation speed, T r Indicates the receiving delay.

[0015] Optionally, the scan frame, response frame, and notification frame all include a frame header;

[0016] The frame header includes a fixed value of the data frame header, a source node MAC address, a destination node MAC address, a frame type, a subframe type, and a data frame length.

[0017] Optionally, the scan frame, the response frame, and the notification frame all include a data field;

[0018] Among them, the data field of the scanning frame includes the cluster number, time slot number, timestamp and CRC check; the data field of the response frame includes the presence or absence of the guide type, source node longitude, source node latitude, source node altitude, northeast sky speed, northeast sky acceleration and CRC check; the data field of the notification frame includes the node allocation ID number, cluster head node ID number, relative longitude, relative latitude, relative altitude and CRC check.

[0019] Optionally, before scanning in wave position polling mode, the following is also included:

[0020] Using the slow node as a reference point, the aerial area is divided into four areas arranged in an array, with each row and column consisting of two areas;

[0021] For the region, build a wave map and define the wave polling order.

[0022] Optionally, build a wavemap and define the wave polling order, including:

[0023] Based on the size of the beam transmitted by the array antenna of the slow node, the maximum range of the coverage beam position in the area and the range of each beam position are determined. The ranges of adjacent beam positions have overlapping areas.

[0024] Take the inscribed regular hexagon of each wave position range, and make the regular hexagons corresponding to adjacent wave positions tangent to each other. Determine the number of layers of regular hexagons corresponding to the wave positions within the maximum range of the wave positions covered in the area, and construct a wave position map.

[0025] The regular hexagon corresponding to the central wave position is used as the starting point of the wave position polling, and the wave position tangent to any side of the regular hexagon corresponding to the central wave position is used as the second point of the wave position polling. The wave position polling order is selected in a clockwise or counterclockwise manner.

[0026] Optionally, based on the size of the beam transmitted by the array antenna of the slow node, the maximum range of coverage beam positions within the area and the range of each beam position are determined, including:

[0027] According to the half-wave angle m of the wide beam transmitted by the array antenna of the slow node, the radius of the maximum range of the coverage position in the area is determined to be r1, r1 = sin(m);

[0028] According to the half-wave angle n of the narrow beam emitted by the array antenna of the slow node, the radius r2 of the range of each beam position in the area is determined, r2=sin(n).

[0029] Optionally, determining the number of regular hexagonal layers corresponding to the wave positions within the maximum range of wave positions covered in the area, and constructing a wave position map, including:

[0030] According to the radius r1 of the maximum range of wave positions covered in the area and the radius r2 of the range of each wave position in the area, the number of layers of regular hexagons corresponding to the wave positions within the maximum range of wave positions covered in the area is calculated, and the wave position map is constructed, whose expression is:

[0031]

[0032] Where s represents the number of layers, the center coordinates of the regular hexagon corresponding to the i-th wave position are expressed as (d·sinβ, d·cosβ), and the side length of the i-th virtual hexagon formed by the center line of the regular hexagon corresponding to the i-th wave position is expressed as:

[0033]

[0034] Among them, d and β satisfy the relationship:

[0035]

[0036] Where d represents the vertical distance from the center to the side of the regular hexagon corresponding to the i-th wave position, and β represents the angle between the perpendicular line from the center to the side of the regular hexagon corresponding to the i-th wave position and the y-axis.

[0037] Optionally, after receiving the response frame, the slow node records the following information:

[0038] After receiving the response frame, the slow node determines the wave position of the aerial node that sent the response frame and records the deflection angle and pitch angle corresponding to the wave position. The expression is:

[0039]

[0040] Where θ represents the beam deflection angle, represents the wave position pitch angle, x = d·sinβ, y = d·cosβ, x and y represent the center coordinates of the regular hexagon corresponding to the wave position;

[0041] After receiving the response frame, the slow node determines and records the relative distance D between the aerial node that sent the response frame and the slow node, which is expressed as:

[0042] D=(T2-T1)×V c ;

[0043] Among them, T1 represents the time when the air node receives the scanning frame, T2 represents the time when the air node sends the response frame, V c Represents the speed of electromagnetic propagation.

[0044] Optionally, the slow node elects a cluster head based on its recorded results, and sends the cluster head information to all the aerial nodes in the form of a notification frame, including:

[0045] The slow node elects the aerial node as the cluster head according to the preset rules based on the deflection angle and pitch angle corresponding to the wave position of the aerial node and the relative distance between the aerial node and the slow node;

[0046] The slow node calculates the longitude and latitude of the cluster head based on its own longitude and latitude, the deflection angle and pitch angle corresponding to the wave position of the aerial node, and the relative distance between the aerial node and the slow node. It uses this as the cluster head information and sends it to all aerial nodes in the form of a notification frame.

[0047] Beneficial effects of the present invention:

[0048] The application provides a cluster head election method of a satellite-free unmanned aerial vehicle network based on directional communication, wherein the slow node scans the aerial node at the current wave position in a wave position polling manner, and the slow node and the aerial node interact, so that the unmanned aerial vehicle can still autonomously elect a cluster head in a satellite-free environment, and self-organizing management and communication scheduling in the group are realized; thus, the autonomy of the system is enhanced, so that the unmanned aerial vehicle network can continuously operate in a GPS-free environment, and is suitable for a complex environment where satellite signals are limited or completely absent.

[0049] The application will be further described in detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 is a flow chart of the cluster head election method of the satellite-free unmanned aerial vehicle network based on directional communication provided by the embodiment of the application;

[0051] Figure 2 is a schematic diagram of the wave position polling sequence provided by the embodiment of the application, the cluster head election method of the satellite-free unmanned aerial vehicle network based on directional communication provided by the application comprises the following steps:

[0052] Figure 3 is a schematic diagram of the time slots required for the slow node to elect a cluster head provided by the embodiment of the application;

[0053] Figure 4 is a schematic diagram of the wave position projection provided by the embodiment of the application;

[0054] Figure 5 is a schematic diagram of the center coordinates of the regular hexagon corresponding to the i-th layer wave position provided by the embodiment of the application. DETAILED DESCRIPTION

[0055] The application will be further described in detail below with reference to the drawings and embodiments, but the embodiments of the application are not limited thereto.

[0056] Please refer to Figure 1 and Figure 2 , Figure 1 is a flow chart of the cluster head election method of the satellite-free unmanned aerial vehicle network based on directional communication provided by the embodiment of the application, Figure 2 is a schematic diagram of the wave position polling sequence provided by the embodiment of the application, the cluster head election method of the satellite-free unmanned aerial vehicle network based on directional communication provided by the application comprises the following steps:

[0057] S101, the slow node scans the aerial node at the current wave position in a wave position polling manner, and sends a scanning frame.

[0058] Specifically, in the embodiment, the wave position is provided with n, the time slots for the slow node to send the scanning frame are n, the time slots for receiving the response frame are n, and the time slots for sending the notification frame are x, wherein x represents the number of the aerial nodes.

[0059] See Figure 3 , Figure 3 This is a schematic diagram of the time slots required for a slow node to elect a cluster head provided by an embodiment of the present invention. The time slots for a slow node to elect a cluster head are 2n+x. Optionally, the number of aerial nodes is 16.

[0060] Each time slot includes a data phase and a protection phase. The data phase is 1.5T and the protection phase is 1T. T = T t +T s +T r , T t =a / b, T s =c / d, T r ≈T t , T t Indicates the transmission delay, a indicates the data length (bit), b indicates the transmission rate (bps), T s represents the propagation delay, c represents the maximum distance between the slow node and the air node (m), d represents the electromagnetic propagation speed (3×108m / s), T r Indicates the receiving delay. It should be noted that the data phase allows the sending of scan frames and the receiving of response frames, while the protection phase only allows the receiving of response frames.

[0061] Optionally, the slow node is a ground node or a sea node, and the aerial node is a drone.

[0062] In this embodiment, the scanning frame includes a frame header and a data field. The frame header of the scanning frame includes a fixed value of the data frame header (frame_head), a source node MAC address (addr_src), a destination node MAC address (addr_dst), a frame type (frame_type), a subframe type (frame_subtype) and a data frame length (frame_data_len). The data field of the scanning frame includes a cluster number (net_num), a time slot number (slot_num), a timestamp (timeStamp) and a CRC check (CRC).

[0063] S102. If the aerial node exists at the current wave position, the aerial node sends a response frame to the slow node after receiving the scan frame. The slow node receives the response frame and records it. The slow node continues to scan the aerial node at the next wave position in a wave position polling manner and sends a scan frame.

[0064] Specifically, in this embodiment, the response frame includes a frame header and a data field. The frame header of the response frame includes a fixed value of the data frame header (frame_head), the source node MAC address (addr_src), the destination node MAC address (addr_dst), the frame type (frame_type), the subframe type (frame_subtype) and the data frame length (frame_data_len). The data field of the response frame includes whether there is a guide type (type), the source node longitude (longitude), the source node latitude (latitude), the source node altitude (altitude), the northeast celestial speed (speed), the northeast celestial acceleration (ac_speed) and the CRC check (CRC).

[0065] S103: If there is no aerial node at the current wave position, the slow node continues to scan the aerial node at the next wave position in a wave position polling manner and sends a scan frame.

[0066] It should be noted that when there is no aerial node at the current wave position, the slow node will not receive a response frame within a certain period of time and will continue to scan the aerial node at the next wave position and send a scan frame.

[0067] S104: until all the wave positions are scanned, the slow node recommends a cluster head according to its recorded results, and sends the cluster head information to all aerial nodes in the form of a notification frame.

[0068] Specifically, in this embodiment, the notification frame includes a frame header and a data field. The notification frame header includes a fixed value of the data frame header (frame_head), the source node MAC address (addr_src), the destination node MAC address (addr_dst), the frame type (frame_type), the subframe type (frame_subtype) and the data frame length (frame_data_len). The notification frame data field includes the node allocation ID number (node_id), the cluster head node ID number (head_id), the relative longitude (head_id), the relative latitude (rela_la), the relative altitude (rela_al) and the CRC check (CRC).

[0069] S105: The aerial node performs self-verification to determine whether it is the cluster head.

[0070] In summary, the present invention provides a cluster head selection method for a satellite-free UAV network based on directional communication, which has the following beneficial effects:

[0071] 1. Enhanced self-organization capabilities of drone networks. By using slow nodes to scan aerial nodes in a wave position polling manner, drones can still autonomously elect cluster leaders in environments without satellite navigation, achieving self-organization management and communication scheduling within the group. This enhances the autonomy of the system, allowing drone networks to continue operating in GPS-free environments, making them suitable for complex environments where satellite signals are limited or completely absent.

[0072] 2. Reduced reliance on external navigation systems. This method relies on nodes within the network to perform cluster leader recommendation in the absence of satellite navigation, reducing reliance on external navigation systems and improving the survivability and adaptability of the UAV system in harsh environments. It is particularly suitable for missions in high-interference or hostile areas.

[0073] 3. Improved network stability and robustness. Through the cluster head selection method, the network can quickly respond to dynamic changes such as node movement, failure, or loss, maintaining network stability. The rational selection of cluster heads makes resource allocation more efficient and can effectively reduce communication interruptions caused by node failures or link instability.

[0074] 4. Optimized communication performance. The cluster head election method based on directional networks reduces interference and conflicts within the network by utilizing directional antennas and directional links, improving the success rate and efficiency of communication. The elected cluster head node can effectively manage communication within the cluster, reducing resource competition and data conflicts, thereby improving the communication performance of the entire network.

[0075] 5. Save energy consumption and extend network life. The elected cluster head node takes on the management and data aggregation tasks within the cluster, reducing the communication burden of non-cluster head nodes and thus reducing their energy consumption.

[0076] 6. Strong adaptability, suitable for a variety of application scenarios. This method can be applied to a variety of complex drone swarm missions, such as disaster relief and environmental monitoring, and is particularly suitable for environments without satellite navigation or with limited navigation. Through cluster head recommendation, the system can quickly adjust the network structure to adapt to different mission requirements and scenario changes.

[0077] In general, this invention improves the autonomy, stability and communication performance of drone networks, and has significant application advantages in complex environments.

[0078] In an optional embodiment of the present invention, please continue to refer to Figure 2 Before scanning in wave polling mode, it also includes:

[0079] Using the slow node as a reference point, the aerial area is divided into four areas arranged in an array, with each row and column consisting of two areas;

[0080] For the region, build a wave map and define the wave polling order.

[0081] In this embodiment, the wave positions scanned by the slow node are analyzed and designed to determine the coverage mode, and the parameters such as the number and pointing position of each sub-wave position corresponding to the beam transmitted by the array antenna in the slow node within a given scanning range are calculated.

[0082] The relationship between the communication distance and beamwidth between slow and airborne nodes depends on factors such as the communication scheme, antenna type, and channel capacity. Generally speaking, a smaller beamwidth increases the communication distance, but also increases the difficulty of signal alignment. Taking these factors into consideration, each node is designed to be equipped with one omnidirectional antenna and one directional antenna, both with a beamwidth of 15 degrees.

[0083] The wave position map is constructed based on the idea of ​​joint coverage of regular hexagons. Each regular hexagon corresponds to a sub-wave position. These sub-wave positions are numbered, and the wave position deflection angle and pitch angle are calculated. Specifically:

[0084] See Figure 4 , Figure 4 This is a schematic diagram of the beam position projection provided by an embodiment of the present invention. The array antenna is placed in the XOY plane of the unit sphere coordinate system. The center of the array coincides with the center of the unit sphere. The boundary of the beam position with the maximum range obtained by the array antenna intersects with a single beam position. Projection is performed to obtain a projected great circle, i.e., the maximum range of the beam position. The sub-beams of the array antenna are projected to obtain the range of each beam position. Taking into account the antenna widening effect, the projection is also a circle. The inscribed regular hexagons of the small circles corresponding to each beam position are jointly covered. The center beam position is numbered 1, and the beam positions above it are numbered starting from the upper beam position. Each beam position is marked layer by layer in a counterclockwise direction, as shown in Figure 2. Thus, the beam coverage problem in three-dimensional space is transformed into a two-dimensional plane, where the small projected circles corresponding to the beam positions are used to cover the projected great circle corresponding to the wide beam.

[0085] In an optional embodiment of the present invention, constructing a wavemap and defining a wavepoll sequence include:

[0086] Based on the size of the beam transmitted by the array antenna of the slow node, the maximum range of the coverage beam position in the area and the range of each beam position are determined. The ranges of adjacent beam positions have overlapping areas.

[0087] Take the inscribed regular hexagon of each wave position range, and make the regular hexagons corresponding to adjacent wave positions tangent to each other. Determine the number of layers of regular hexagons corresponding to the wave positions within the maximum range of the wave positions covered in the area, and construct a wave position map.

[0088] The regular hexagon corresponding to the central wave position is used as the starting point of the wave position polling, and the wave position tangent to any side of the regular hexagon corresponding to the central wave position is used as the second point of the wave position polling. The wave position polling order is selected in a clockwise or counterclockwise manner.

[0089] In an optional embodiment of the present invention, determining the maximum range of coverage beam positions within the area and the range of each beam position based on the size of the beam transmitted by the array antenna of the slow node includes:

[0090] According to the half-wave angle m of the wide beam transmitted by the array antenna of the slow node, the radius of the maximum range of the coverage position in the area is determined to be r1, r1 = sin(m);

[0091] According to the half-wave angle n of the narrow beam emitted by the array antenna of the slow node, the radius r2 of the range of each beam position in the area is determined, r2=sin(n).

[0092] In an optional embodiment of the present invention, determining the number of regular hexagonal layers corresponding to wave positions within a maximum range of wave positions covered in a region and constructing a wave position map includes:

[0093] According to the radius r1 of the maximum range of wave positions covered in the area and the radius r2 of the range of each wave position in the area, the number of layers of regular hexagons corresponding to the wave positions within the maximum range of wave positions covered in the area is calculated, and the wave position map is constructed, whose expression is:

[0094]

[0095] Where s represents the number of layers, see Figure 5 , Figure 5 This is a schematic diagram of obtaining the center coordinates of a regular hexagon corresponding to the i-th wave position provided by an embodiment of the present invention. The center coordinates of the regular hexagon corresponding to the i-th wave position are expressed as (d·sinβ, d·cosβ). The side length of the i-th virtual hexagon formed by connecting the centers of the regular hexagons corresponding to the i-th wave position is expressed as:

[0096]

[0097] Among them, d and β satisfy the relationship:

[0098]

[0099] Where d represents the vertical distance from the center to the edge of the regular hexagon corresponding to the i-th wave position, β represents the angle between the perpendicular line from the center to the edge of the regular hexagon corresponding to the i-th wave position and the y-axis, and the y-axis represents the y-axis in the geodetic coordinate system.

[0100] In an optional embodiment of the present invention, after receiving the response frame, the slow node records it, including:

[0101] After receiving the response frame, the slow node determines the wave position of the aerial node that sent the response frame and records the deflection angle and pitch angle corresponding to the wave position. The expression is:

[0102]

[0103] Where θ represents the beam deflection angle, represents the wave position pitch angle, x = dvsinβ, y = d·cosβ, x and y represent the center coordinates of the regular hexagon corresponding to the wave position; it should be noted that the deflection angle and pitch angle of the wave position can be obtained according to the positive and negative values ​​of x and y.

[0104] After receiving the response frame, the slow node determines and records the relative distance D between the aerial node that sent the response frame and the slow node, which is expressed as:

[0105] D=(T2-T1)×V c ;

[0106] Among them, T1 represents the time when the air node receives the scanning frame, T2 represents the time when the air node sends the response frame, and V c Represents the speed of electromagnetic propagation.

[0107] In an optional embodiment of the present invention, the slow node elects a cluster head based on its recorded results and sends the cluster head information to all air nodes in the form of a notification frame, including:

[0108] The slow node elects the aerial node as the cluster head according to the preset rules based on the deflection angle and pitch angle corresponding to the wave position of the aerial node and the relative distance between the aerial node and the slow node;

[0109] The slow node calculates the longitude and latitude of the cluster head based on its own longitude and latitude, the deflection angle and pitch angle corresponding to the wave position of the aerial node, and the relative distance between the aerial node and the slow node. It uses this as the cluster head information and sends it to all aerial nodes in the form of a notification frame.

[0110] In an optional embodiment of the present invention, the above-mentioned wave position design is simulated and tested, such as Figure 4 As shown in the figure, the coverage effect of the 1 / 4 spherical shell area is obtained by combining the wave position area to be scanned and the coverage method. The scanning node is located at the center of the spherical shell. According to the simulation calculation, the number of wave positions scanned for 1 / 4 sphere is 61, so 244 wave positions are required to cover the entire sphere, and 1 / 4 sphere is one area. It can be concluded that for a ground node, 122 wave positions are required to cover the area from 0 to 60° with itself as the center of the sphere.

[0111] It should be noted that, in this document, relational terms such as first and second are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not explicitly listed. Without further limitation, an element defined by the phrase "comprising a..." does not preclude the presence of additional identical elements in the article or device comprising the element. Terms such as "connected" or "connected" are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. References to orientations or positional relationships, such as "upper," "lower," "left," and "right," are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate description and simplify the description of the present invention. They do not indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention.

[0112] In the description of this specification, the reference terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0113] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A cluster head selection method for a satellite-free UAV network based on directional communication, characterized in that: include: The slow node scans the air node at the current wave position in a wave position polling manner and sends a scan frame; If the aerial node exists at the current wave position, the aerial node sends a response frame to the slow node after receiving the scan frame. The slow node receives the response frame and records it. The slow node continues to scan the aerial node at the next wave position in a wave position polling manner and sends a scan frame. Before scanning in wave position polling mode, it also includes: Taking the slow node as a reference point, the aerial area is divided into four areas arranged in an array, with each row and each column including two areas; For the area, a wave map is constructed and a wave polling sequence is defined, including: Determine, based on the size of the beam transmitted by the array antenna of the slow node, the maximum range of the coverage beam positions within the area and the range of each beam position, wherein the ranges of adjacent beam positions have an overlapping area; Take the inscribed regular hexagon of the range of each wave position, and the regular hexagons corresponding to adjacent wave positions are tangent to each other, determine the number of layers of regular hexagons corresponding to the wave positions within the maximum range of the wave positions covered in the area, and construct a wave position map; The regular hexagon corresponding to the central wave position is used as the starting point of the wave position polling, and the wave position tangent to any side of the regular hexagon corresponding to the central wave position is used as the second point of the wave position polling. The wave position polling order is selected in a clockwise or counterclockwise manner; If the aerial node does not exist at the current wave position, the slow node continues to scan the aerial node at the next wave position in a wave position polling manner and sends a scan frame; Until all the wave positions are scanned, the slow node elects a cluster head according to its recorded results and sends the cluster head information to all the aerial nodes in the form of a notification frame; The aerial node performs self-verification to determine whether it is the cluster head.

2. The cluster head selection method for a satellite-free UAV network based on directional communication according to claim 1 is characterized in that: The wave position is set The time slot for the slow node to send the scanning frame is The time slot for receiving the response frame is The time slot for sending notification frames is indivual, represents the number of aerial nodes; The time slot for the slow node to elect the cluster head is ; Each time slot includes a data phase and a protection phase. The data phase is , the protection stage is , , , , , Indicates the sending delay, Indicates the data length, Indicates the sending rate, represents the propagation delay, Indicates the maximum distance between the slow node and the air node, represents the electromagnetic propagation speed, Indicates the receiving delay.

3. The cluster head selection method for a satellite-free UAV network based on directional communication according to claim 1, characterized in that: The scanning frame, the response frame and the notification frame all include a frame header; The frame header includes a fixed value of a data frame header, a source node MAC address, a destination node MAC address, a frame type, a subframe type, and a data frame length.

4. The cluster head selection method for a satellite-free UAV network based on directional communication according to claim 1, characterized in that: The scanning frame, the response frame and the notification frame all include a data field; Among them, the data field of the scanning frame includes the cluster number, time slot number, timestamp and CRC check; the data field of the response frame includes the presence or absence of the guide type, source node longitude, source node latitude, source node altitude, northeast sky speed, northeast sky acceleration and CRC check; the data field of the notification frame includes the node allocation ID number, cluster head node ID number, relative longitude, relative latitude, relative altitude and CRC check.

5. The cluster head selection method for a satellite-free UAV network based on directional communication according to claim 1, characterized in that: Determining the maximum range of coverage beam positions within the area and the range of each beam position based on the size of the beam transmitted by the array antenna of the slow node includes: According to the half-wave angle of the wide beam transmitted by the array antenna of the slow node , determine the radius of the maximum range of the coverage wave position in the area as , ; According to the half-wave angle of the narrow beam transmitted by the array antenna of the slow node , determine the radius of the range of each wave position in the area , .

6. The cluster head selection method for a satellite-free UAV network based on directional communication according to claim 5, characterized in that: Determining the number of regular hexagonal layers corresponding to the wave positions within the maximum range of the wave positions covered in the area, and constructing a wave position map, including: The radius of the maximum range of the coverage wave position in the area is and the radius of each wave position within the area , calculate the number of regular hexagonal layers corresponding to the wave position within the maximum range of the wave position covered in the area, and construct a wave position map, whose expression is: ； in, Indicates the number of layers, The center coordinates of the regular hexagon corresponding to the layer wave position are expressed as , No. The first layer wave position is formed by connecting the centers of the regular hexagons The side length of a virtual hexagon is expressed as: ； in, and Satisfies the relationship: ； in, Indicates the The vertical distance from the center to the side of the regular hexagon corresponding to the layer wave position, Indicates the The perpendicular line from the center to the edge of the regular hexagon corresponding to the layer wave position is The angle between the axes.

7. The cluster head selection method for a satellite-free UAV network based on directional communication according to claim 6, characterized in that: After receiving the response frame, the slow node records the response frame, including: After receiving the response frame, the slow node determines the wave position of the aerial node that sent the response frame, and records the deflection angle and pitch angle corresponding to the wave position, which are expressed as follows: ； ； in, represents the beam deflection angle, Indicates the wave position pitch angle, , , and Indicates the center coordinates of the regular hexagon corresponding to the wave position; After receiving the response frame, the slow node determines and records the relative distance between the aerial node that sent the response frame and the slow node. , whose expression is: ； in, Indicates the time when the aerial node receives the scan frame. Indicates the time when the air node sends the response frame. Represents the speed of electromagnetic propagation.

8. The cluster head selection method for a satellite-free UAV network based on directional communication according to claim 7, characterized in that: The slow node elects a cluster head based on its recorded results and sends the cluster head information to all the air nodes in the form of a notification frame, including: The slow node elects the aerial node as the cluster head according to a preset rule based on the deflection angle and pitch angle corresponding to the wave position where the aerial node is located, and the relative distance between the aerial node and the slow node; The slow node calculates the longitude and latitude of the cluster head based on its own longitude and latitude, the deflection angle and pitch angle corresponding to the wave position of the aerial node, and the relative distance between the aerial node and the slow node, and sends it as cluster head information to all the aerial nodes in the form of a notification frame.

Images