A method for suppressing Doppler frequency offset in unmanned aerial vehicle ad hoc network

Abstract

The application provides a UAV ad hoc network Doppler frequency offset suppression method, relates to the field of unmanned aerial vehicles (UAVs), and is applied to a UAV. A mobile antenna is installed on the UAV. The method comprises the following steps: acquiring current flight control information of the UAV in a ground reference coordinate system and acquiring a current position of the mobile antenna in a rectangular coordinate system, wherein the rectangular coordinate system is consistent with the direction of the body coordinate system of the UAV; calculating a radial velocity caused by the movement of the UAV based on the current flight control information and the current position, and determining a speed control instruction according to the radial velocity; and driving the mobile antenna according to the speed control instruction to suppress the Doppler frequency offset of the communication link between the UAV and a ground base station. The application can effectively suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) technology, and in particular to a method for suppressing Doppler frequency offset in UAV self-organizing networks. Background Technology

[0002] With the development of integrated air-space-ground networks, drones have become key aerial nodes in ad-hoc networks. Leveraging their advantages such as flexible deployment, high mobility, and on-demand adjustable coverage, drones are widely used in typical scenarios such as power grid inspection, emergency communications, and low-Earth orbit satellite terminal relay. In power grid inspection scenarios, drone swarms can form multi-hop ad-hoc networks to collaboratively complete the distributed collection and transmission of transmission line inspection data. In emergency communications and satellite terminal relay scenarios, drones, acting as aerial relay nodes, need to quickly build dynamic ad-hoc networks to provide reliable communication links between ground users and low-Earth orbit satellites.

[0003] However, the nodes in an ad hoc UAV network are characterized by high-speed movement and rapid topology changes. When flying at high speed along power transmission lines, turning, and diving, or rapidly maneuvering to form a network in emergency scenarios, the relative motion between nodes introduces significant Doppler frequency offset and phase rotation into the communication link. In Doppler frequency offset-sensitive communication systems (such as long symbol systems, narrow subcarrier systems, and strictly coherent detection systems), the Doppler effect caused by UAV movement can directly disrupt carrier synchronization, leading to degraded demodulation performance, increased bit error rate, and even link interruption. In ad hoc network scenarios, the interruption of a single link can trigger network topology reconstruction and routing switching delays, severely impacting the overall reliability of power grid inspection data transmission, emergency communication networking, and satellite terminal relay. Summary of the Invention

[0004] This invention provides a method for suppressing Doppler frequency offset in UAV self-organizing networks, which solves the technical problem in the prior art that the Doppler effect caused by UAV movement directly destroys carrier synchronization, resulting in deterioration of demodulation performance, increase in bit error rate, and even link interruption.

[0005] This invention provides a method for suppressing Doppler frequency offset in unmanned aerial vehicle (UAV) self-organizing networks, comprising the following steps: The current flight control information of the UAV in the ground reference coordinate system is obtained, and the current position of the mobile antenna in the rectangular coordinate system is obtained, wherein the rectangular coordinate system is aligned with the body coordinate system of the UAV. Based on the current flight control information and the current position, calculate the radial velocity caused by the movement of the UAV, and determine the speed control command based on the radial velocity; The mobile antenna is driven according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

[0006] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network includes obtaining the current flight control information of the UAV in a geodetic reference coordinate system, comprising: A geodetic reference coordinate system is constructed using ground base stations as the origin. The position of the center of mass of the UAV in the geodetic coordinate system is obtained, as well as the velocity of the UAV's center of mass, attitude angles, and Euler angular velocity, wherein the attitude angles include the roll angle, pitch angle, and yaw angle of the UAV. The current flight control information is determined based on the UAV's center of mass position, the UAV's center of mass velocity, the UAV's attitude angle, and the Euler angular velocity.

[0007] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network includes calculating the radial velocity caused by the motion of the UAV based on the current flight control information and the current position, comprising: Based on the UAV attitude angles in the current flight control information, calculate the rotation matrix from the rectangular coordinate system to the geodetic reference coordinate system; Based on the current flight control information and the current position, determine the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system; Based on the current position, the Euler angular velocity in the current flight control information, and the rotation matrix, calculate the antenna-added velocity caused by the UAV's attitude rotation; Based on the UAV's center of mass velocity, the antenna-attached velocity, and the line-of-sight vector in the current flight control information, the radial velocity caused by the UAV's motion is calculated.

[0008] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network includes determining the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system based on the current flight control information and the current position. The origin of the rectangular coordinate system is set to a fixed offset relative to the centroid of the UAV; Based on the current position and the fixed offset, calculate the relative position of the mobile antenna with respect to the center of mass of the UAV; Based on the centroid position, rotation matrix, and relative position in the current flight control information, calculate the antenna position of the mobile antenna in the geodetic reference coordinate system. Based on the antenna position, the line-of-sight vector from the mobile antenna to the ground base station is determined in the rectangular coordinate system.

[0009] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network includes determining the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system based on the antenna position, comprising: Based on the antenna location, calculate the direction vector from the ground base station to the mobile antenna; The direction vector is normalized to obtain a unit line-of-sight vector; Using the inverse of the rotation matrix, the unit line-of-sight vector is transformed into the rectangular coordinate system to obtain the line-of-sight vector in the rectangular coordinate system.

[0010] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network, wherein determining the speed control command based on the radial velocity includes: A minimum motion compensation speed is generated based on the radial velocity, wherein the minimum motion compensation speed is a motion speed that is only along the direction of the line-of-sight vector and opposite to the direction of the radial velocity; The speed control command is determined based on the minimum motion compensation speed.

[0011] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network, wherein determining the speed control command based on the minimum motion compensation speed includes: The velocity component of the minimum motion compensation velocity in the direction of the line-of-sight vector is set to be equal to the negative value of the radial velocity, and the velocity component of the minimum motion compensation velocity in the direction perpendicular to the line-of-sight vector is zero. Based on the negative value of the radial velocity and the line-of-sight vector, a three-dimensional velocity vector is generated in the rectangular coordinate system, and the three-dimensional velocity vector is used as the minimum motion compensation velocity. The minimum motion compensation speed is converted into a speed control command for the mobile antenna.

[0012] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network, wherein driving the mobile antenna according to the speed control command includes: According to the speed control command, the mobile antenna is driven to move along the direction of the line-of-sight vector in the rectangular coordinate system, and the movement speed is equal in magnitude and opposite in direction to the radial speed.

[0013] According to the present invention, a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) self-organizing network is provided, wherein the mobile antenna has three-dimensional degrees of freedom of movement within the rectangular coordinate system.

[0014] The present invention also provides a Doppler frequency offset suppression device for unmanned aerial vehicle (UAV) self-organizing networks, comprising the following modules: The acquisition module is used to acquire the current flight control information of the UAV in the ground reference coordinate system, and to acquire the current position of the mobile antenna in the rectangular coordinate system, wherein the rectangular coordinate system is aligned with the UAV's body coordinate system. The calculation module is used to calculate the radial velocity caused by the movement of the UAV based on the current flight control information and the current position, and to determine the speed control command based on the radial velocity; The suppression module is used to drive the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

[0015] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the Doppler frequency offset suppression method for UAV ad hoc networks as described above.

[0016] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the Doppler frequency offset suppression method for UAV self-organizing networks as described above.

[0017] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the Doppler frequency offset suppression method for UAV self-organizing networks as described above.

[0018] This invention provides a method for suppressing Doppler frequency offset in an unmanned aerial vehicle (UAV) ad hoc network. The method involves acquiring the current flight control information of the UAV in a ground reference coordinate system and the current position of the mobile antenna in a rectangular coordinate system, wherein the rectangular coordinate system is aligned with the UAV's body coordinate system. Based on the current flight control information and the current position, the method calculates the radial velocity caused by the UAV's motion and determines a speed control command based on the radial velocity. The method then drives the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station. This invention addresses the technical problem that the Doppler effect caused by UAV motion directly disrupts carrier synchronization, leading to degraded demodulation performance, increased bit error rate, and even link interruption. Compared to existing technologies, this invention obtains flight control information in a geodetic reference coordinate system and the current antenna position in a rectangular coordinate system (aligned with the aircraft's coordinate system). Based on these two information, it accurately calculates the radial velocity caused by the UAV's motion and generates a velocity control command to drive the moving antenna in the opposite direction. This proactively suppresses Doppler frequency shift in the communication link from the source of motion, effectively avoiding carrier synchronization disruption, demodulation performance degradation, increased bit error rate, and link interruption. Since compensation is only applied to the radial velocity component, it avoids redundant antenna displacement introduced by non-radial motion, thus effectively suppressing Doppler frequency shift and its resulting phase changes within a limited range of motion. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is one of the flowcharts illustrating the Doppler frequency offset suppression method for UAV self-organizing networks provided by the present invention.

[0021] Figure 2 This is a system model diagram of the Doppler frequency offset suppression method for UAV self-organizing networks provided by the present invention.

[0022] Figure 3 This is the second flowchart of the Doppler frequency offset suppression method for UAV self-organizing networks provided by the present invention.

[0023] Figure 4 This is a simulation diagram of the UAV motion trajectory setting for the UAV self-organizing network Doppler frequency offset suppression method provided by the present invention.

[0024] Figure 5 This is a simulation setting diagram of the UAV motion speed for the UAV self-organizing network Doppler frequency offset suppression method provided by the present invention.

[0025] Figure 6 This is a simulation diagram of the Doppler compensation effect of the Doppler frequency offset suppression method for UAV self-organizing networks provided by the present invention.

[0026] Figure 7 This is a schematic diagram of the Doppler frequency offset suppression device for UAV self-organizing networks provided by the present invention.

[0027] Figure 8 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] The following is combined Figure 1 and Figure 3 The present invention describes a method for suppressing Doppler frequency offset in an ad hoc UAV network. This method is applicable to suppressing Doppler frequency offset in any ad hoc UAV network. The subject executing this method can be an electronic device or a Doppler frequency offset suppression device for ad hoc UAV networks installed in the electronic device. The Doppler frequency offset suppression device for ad hoc UAV networks can be implemented by software, hardware, or a combination of both.

[0030] Figure 1 This is one of the flowcharts illustrating the Doppler frequency offset suppression method for UAV self-organizing networks provided by the present invention, such as... Figure 1 As shown, the UAV self-organizing network Doppler frequency offset suppression method is applied to a UAV, which is equipped with a mobile antenna. The method includes the following: Step 101: Obtain the current flight control information of the UAV in the ground reference coordinate system, and obtain the current position of the mobile antenna in the rectangular coordinate system, wherein the rectangular coordinate system is aligned with the UAV's body coordinate system. It should be noted that the geodetic reference coordinate system is a fixed spatial reference system established with the ground base station as the origin, used to describe the absolute position and motion of the UAV; flight control information includes the UAV's center of mass position, velocity, attitude angle, and Euler angular velocity; the rectangular coordinate system is a local coordinate system fixed to the UAV body and aligned with its direction, with its three coordinate axes parallel to the front-back, left-right, and up-down directions of the body, respectively; the current position of the mobile antenna refers to the antenna's three-dimensional spatial coordinates in the rectangular coordinate system.

[0031] It's important to note that the mobile antenna possesses three degrees of freedom of movement within a rectangular coordinate system. These three degrees of freedom mean the antenna can move independently along the three coordinate axes of the rectangular coordinate system: the X-axis (front / back), the Y-axis (left / right), and the Z-axis (up / down). By granting the antenna these three degrees of freedom, it can generate velocity vectors in any direction, enabling precise movement along the line-of-sight vector. Without these three degrees of freedom, the antenna's movement would be restricted, potentially preventing it from moving along the line-of-sight and leading to compensation failure or inaccuracy.

[0032] In practical implementation, the flight control data packets within the current control cycle can be read through the UAV flight control system, and the three-dimensional position coordinates and three-dimensional velocity components of the UAV's center of mass in the Earth reference coordinate system can be obtained by parsing. At the same time, the roll angle, pitch angle, yaw angle and their corresponding angular velocities of the UAV can be read from the flight control system. The current coordinate values ​​of the moving antenna in the rectangular coordinate system can be read through the antenna position sensor or the encoder of the drive mechanism.

[0033] In specific implementations, such as Figure 2 As shown, the UAV platform acts as an aerial mobile node, with a cuboid coordinate system C (referred to as the C coordinate system) fixed to its body. This coordinate system is aligned with the UAV's body coordinate system and rotates synchronously with the UAV's attitude changes. A movable antenna is installed within the UAV platform's movable space, a cuboid region aligned with the C coordinate system, within which the antenna can move independently in three orthogonal directions. Wireless signal transmission between the UAV and the ground base station occurs via a communication link. The UAV's movement generates Doppler frequency shift on this link. By acquiring the UAV's flight control information (including center of mass position, velocity, attitude angles, and Euler angular velocity) and the antenna's current position in the C coordinate system, the required compensation motion for the antenna can be calculated in real time. This drives the antenna to move in the opposite direction along the line of sight within the movable space, thereby canceling the Doppler frequency shift and maintaining the stability of the communication link.

[0034] Step 102: Based on the current flight control information and the current position, calculate the radial velocity caused by the movement of the UAV, and determine the speed control command based on the radial velocity; It should be noted that radial velocity refers to the radial velocity component of the mobile antenna relative to the ground base station, that is, the projection value of the antenna's resultant velocity in the line-of-sight direction from the antenna to the base station; the speed control command is the control signal to be sent to the antenna drive mechanism to control the antenna's movement speed.

[0035] In practical implementation, the radial velocity affecting Doppler frequency offset can be extracted using flight control information and the current antenna position through coordinate transformation and vector operations. Then, a compensation velocity capable of offsetting this radial velocity is generated. Finally, this compensation velocity is converted into a speed control command recognizable by the antenna actuator. Specifically, the rotation matrix is ​​first calculated based on the attitude angles in the flight control information, and then the line-of-sight vector is calculated by combining the current antenna position and a fixed offset. Next, the projection of the antenna's resultant velocity onto the line-of-sight direction is calculated based on the centroid velocity, Euler angular velocity, and the current antenna position to obtain the radial velocity. Finally, the magnitude of the compensation velocity is set to be equal to the absolute value of the radial velocity, and its direction is opposite to the radial velocity.

[0036] Step 103: Drive the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

[0037] It should be noted that the speed control command is a command signal used to control the mobile antenna drive mechanism to perform corresponding movements; drive refers to making the mobile antenna move at the command speed through a mechanical actuator (such as a linear motor, voice coil motor, or MEMS driver).

[0038] In practical implementation, the calculated speed control command can be sent to the antenna drive control unit. The drive control unit generates the corresponding drive current or voltage according to the command, and controls the linear motor or piezoelectric actuator to drive the antenna to move along the line of sight. The real-time value of its movement speed is adjusted through closed-loop feedback to ensure that the actual movement speed accurately follows the command value, thereby effectively canceling the Doppler frequency shift in the communication link.

[0039] The Doppler frequency offset suppression method for UAV ad hoc networks provided in this invention obtains flight control information in the geodetic reference coordinate system and the current antenna position in the rectangular coordinate system (aligned with the body coordinate system). Based on these two information, the radial velocity caused by the UAV's motion can be accurately calculated, and a speed control command can be generated to drive the mobile antenna to move in the opposite direction. This actively suppresses the Doppler frequency offset of the communication link from the source of motion, effectively avoiding carrier synchronization failure, demodulation performance degradation, increased bit error rate, and link interruption. Since compensation is only performed on the radial velocity component, redundant antenna displacement introduced by non-radial motion is avoided, minimizing the range of motion of the mobile antenna. This allows for effective suppression of Doppler frequency offset and its caused phase changes within a limited range of motion.

[0040] Based on any of the above embodiments, obtaining the current flight control information of the UAV in the geodetic reference coordinate system includes: A geodetic reference coordinate system is constructed using ground base stations as the origin. The position of the center of mass of the UAV in the geodetic coordinate system is obtained, as well as the velocity of the UAV's center of mass, attitude angles, and Euler angular velocity, wherein the attitude angles include the roll angle, pitch angle, and yaw angle of the UAV. The current flight control information is determined based on the UAV's center of mass position, the UAV's center of mass velocity, the UAV's attitude angle, and the Euler angular velocity.

[0041] It should be noted that a ground base station is a fixed device at the ground end of a communication link, and its spatial location is known and unchanging; the geodetic reference coordinate system is a three-dimensional rectangular coordinate system with its origin located at the base station, and usually takes the east direction as the positive X-axis, the north direction as the positive Y-axis, and the sky direction as the positive Z-axis.

[0042] It should be noted that the center of mass position is the three-dimensional coordinate of the UAV's overall center of mass in the Earth's reference coordinate system; the center of mass velocity is the derivative of this position vector with respect to time, reflecting the speed and direction of the UAV's translation; the roll angle is the rotation angle about the X-axis (forward), the pitch angle is the rotation angle about the Y-axis (lateral), and the yaw angle is the rotation angle about the Z-axis (vertical); the Euler angular velocity is the rate of change of the three attitude angles with time. Among these, the center of mass position and velocity describe the overall translational state of the UAV; the attitude angles describe the orientation of the UAV; and the Euler angular velocity describes the rate of rotation of the UAV.

[0043] The Doppler frequency offset suppression method for UAV ad hoc networks provided in this invention constructs a geodetic reference coordinate system with the ground base station as the origin and acquires complete flight control information such as the centroid position, velocity, attitude angle, and Euler angular velocity. This provides a unified spatial reference and motion parameters for subsequent accurate extraction of radial velocity and coordinate transformation. This method avoids calculation errors caused by the use of multiple coordinate systems, ensures an accurate description of the UAV's motion state, and thus significantly improves the accuracy and real-time performance of Doppler frequency offset suppression.

[0044] Figure 3 This is the second flowchart of the Doppler frequency offset suppression method for UAV self-organizing networks provided by the present invention, as shown in Figure 3. Step 102 further includes steps 1021 to 1024: Step 1021: Calculate the rotation matrix from the rectangular coordinate system to the geodetic reference coordinate system based on the UAV attitude angle in the current flight control information; It should be noted that the rotation matrix is ​​a 3x3 orthogonal matrix composed of trigonometric function values ​​of the attitude angles. It is used to convert the coordinate representation of a vector in a rectangular coordinate system to its coordinate representation in a geodetic reference coordinate system, as follows: In the formula, , , , , , , , , These represent the roll angle, pitch angle, and yaw angle of the UAV, respectively.

[0045] In a practical implementation, the rotation matrix can be calculated based on the UAV's attitude angles: The attitude angles of the UAV include the roll angle. Pitch angle and yaw angle .

[0046] Step 1022: Based on the current flight control information and the current position, determine the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system; It should be noted that the line-of-sight vector is a unit vector representing the direction from the mobile antenna to the ground base station, and this vector is represented in a rectangular coordinate system.

[0047] In the specific implementation, the position of the antenna relative to the centroid is first calculated based on the fixed offset and the current position of the antenna. Then, the absolute position of the antenna in the geodetic coordinate system is calculated by combining the position of the centroid and the rotation matrix. Next, the direction vector from the antenna to the base station is calculated and normalized. Finally, the inverse of the rotation matrix is ​​used to transform the direction to the rectangular coordinate system to obtain the line-of-sight vector.

[0048] Step 1023: Based on the current position, the Euler angular velocity in the current flight control information, and the rotation matrix, calculate the antenna-added velocity caused by the attitude rotation of the UAV; It should be noted that the antenna-added velocity is the additional velocity generated by the movement of the antenna due to the UAV's own rotation (roll, pitch, yaw). Even if the antenna is stationary relative to the fuselage, it will still be subject to tangential motion. This added velocity is equal to the cross product of the UAV's angular velocity vector and the antenna's position vector relative to the center of mass. Specifically, the Euler angular velocity is first converted to an angular velocity vector in a rectangular coordinate system, and then the cross product of this angular velocity vector and the antenna's position vector relative to the center of mass is calculated to obtain the added velocity. This added velocity reflects the contribution of the UAV's attitude changes to the antenna velocity.

[0049] Step 1024: Calculate the radial velocity caused by the movement of the UAV based on the UAV's center of mass velocity, the antenna-attached velocity, and the line-of-sight vector in the current flight control information.

[0050] It should be noted that radial velocity is the radial velocity component of the mobile antenna relative to the ground base station, which is equal to the projection of the antenna's resultant velocity onto the line-of-sight direction. The antenna's resultant velocity consists of three parts: the translational velocity of the UAV's center of mass, the additional velocity of the antenna caused by the UAV's attitude rotation, and the active motion velocity of the antenna itself. Among these, the radial velocity caused by the UAV's motion only considers the first two parts, that is, it does not include the contribution of the antenna's active motion.

[0051] Let the velocity of the UAV's center of mass in the geodetic reference coordinate system (i.e., the velocity of the UAV's center of mass) be... The angular velocity of the UAV in the cuboid coordinate system is The position of the mobile antenna relative to the center of mass of the UAV (i.e., its relative position) is: The additional antenna velocity caused by attitude rotation is ,in, The angular velocity of the UAV in the cuboid coordinate system of the moving antenna is represented by the following formula: In the formula, , , , , , , , , These represent the roll angle, pitch angle, and yaw angle of the UAV, respectively. , , These represent the roll angle, pitch angle, and yaw angle in Euler angular velocity, respectively.

[0052] Since the antenna-added velocity is described in a cuboid coordinate system, it needs to be obtained through a rotation matrix. Only by transforming to the geodetic reference coordinate system can it be directly added to the centroid velocity vector. Therefore, the resultant velocity of the antenna caused by the UAV's motion in the geodetic reference coordinate system is: In the formula, This represents the active motion speed of the mobile antenna in the cuboid coordinate system, that is, the motion speed generated by the antenna itself through the driving mechanism. The radial velocity caused by the movement of the UAV can be offset by adjusting its size and direction, thereby suppressing the Doppler frequency shift.

[0053] The line-of-sight direction is represented by a unit line-of-sight vector. In the geodetic reference coordinate system, the unit line-of-sight vector from the base station to the mobile antenna is denoted as... Then the rate of change of the distance between the antenna and the base station (i.e., the radial velocity) is the projection of the antenna's resultant velocity onto the line-of-sight direction: (1) The rate of change of the distance from the ground base station to the antenna is: (2) Substitute the expression into the equation and use the line-of-sight vector in the cuboid coordinate system. ,in, Represents the unit line-of-sight vector. Representing the gaze vector, we can obtain: Define the radial velocity caused by the drone's own motion (excluding active antenna motion) as: The UAV ad hoc network Doppler frequency offset suppression method provided in this invention calculates the rotation matrix and line-of-sight vector to solve for the antenna-added velocity caused by attitude rotation. Combined with the centroid velocity projection, the radial velocity is obtained. This method accurately separates the contributions of UAV translation and rotation to the antenna velocity, precisely extracting the radial velocity component affecting Doppler frequency offset. This method avoids introducing non-radial motion into the compensation, providing a reliable input for subsequent minimum motion compensation and significantly improving the frequency offset suppression accuracy and link stability under high-speed maneuvering conditions.

[0054] Based on any of the above embodiments, determining the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system based on the current flight control information and the current position includes: The origin of the rectangular coordinate system is set to a fixed offset relative to the centroid of the UAV; Based on the current position and the fixed offset, calculate the relative position of the mobile antenna with respect to the center of mass of the UAV; Based on the centroid position, rotation matrix, and relative position in the current flight control information, calculate the antenna position of the mobile antenna in the geodetic reference coordinate system. Based on the antenna position, the line-of-sight vector from the mobile antenna to the ground base station is determined in the rectangular coordinate system.

[0055] It should be noted that the fixed offset is a constant three-dimensional vector representing the spatial offset of the origin of the rectangular coordinate system (i.e., the center point of the antenna's range of motion) relative to the center of mass of the UAV. It is determined by the UAV's mechanical structure and the antenna's installation position. Specifically, the fixed offset can be set according to the UAV's structural parameters, and this offset establishes the translational relationship between the rectangular coordinate system and the UAV's center of mass.

[0056] It should be noted that relative position refers to the position coordinates of the moving antenna in a coordinate system with the UAV's center of mass as the origin, which is equal to the vector sum of the fixed offset and the antenna's current position in the rectangular coordinate system. Specifically, let the fixed installation offset of the origin of the rectangular coordinate system relative to the UAV's center of mass be... Then the position of the mobile antenna relative to the center of mass of the UAV (i.e., the relative position) is: In the formula, Indicates relative position, in meters; Indicates a fixed bias; This indicates the current position of the mobile antenna.

[0057] It should be noted that the antenna position is the absolute spatial coordinate of the mobile antenna in the Earth reference coordinate system. Specifically, the position of the antenna relative to the ground base station (i.e., the antenna position) is: In the formula, Indicates the antenna position, in meters; Represents the rotation matrix; Indicates relative position; This indicates the location of the drone's center of mass.

[0058] Next, after calculating the antenna position, the distance from the base station to the antenna is calculated: In the formula, The unit is meters.

[0059] The unit line-of-sight vector (in geodetic coordinates) pointing from the base station to the antenna: In the formula, ,and .

[0060] Since the antenna actuator moves in a cuboid coordinate system C, the unit line-of-sight vector is transformed into the cuboid coordinate system to obtain the line-of-sight vector: In the formula, The matrix representing the inverse of the rotation matrix; Represents the line-of-sight vector; This represents the unit line-of-sight vector.

[0061] The Doppler frequency offset suppression method for UAV ad hoc networks provided in this invention involves setting a fixed offset, calculating the antenna's relative centroid position, and combining the rotation matrix with the centroid position to solve for the antenna's absolute position in the geodetic coordinate system, ultimately determining the line-of-sight vector in a rectangular coordinate system. This method achieves accurate mapping of the antenna position between different coordinate systems, effectively solving the time-varying rotation problem between the aircraft and the geodetic coordinate system. It provides a reliable spatial reference for subsequent accurate calculation of radial velocity and minimum motion compensation, significantly improving the accuracy of Doppler frequency offset suppression.

[0062] Based on any of the above embodiments, determining the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system based on the antenna position includes: Based on the antenna location, calculate the direction vector from the ground base station to the mobile antenna; The direction vector is normalized to obtain a unit line-of-sight vector; Using the inverse of the rotation matrix, the unit line-of-sight vector is transformed into the rectangular coordinate system to obtain the line-of-sight vector in the rectangular coordinate system.

[0063] It should be noted that the direction vector is a directed line segment from the ground base station to the mobile antenna, represented in the geodetic reference coordinate system, and its magnitude is equal to the straight-line distance between the antenna and the base station.

[0064] Understandably, normalization involves dividing the direction vector by its magnitude to obtain a unit vector with a magnitude of 1; the unit line-of-sight vector only represents direction and does not contain distance information. The inverse of the rotation matrix is ​​equal to its transpose (because the rotation matrix is ​​an orthogonal matrix), used to transform vectors in the geodetic reference coordinate system back to the rectangular coordinate system.

[0065] In practical implementation, the direction vector is a directed line segment from the ground base station to the mobile antenna, represented in the geodetic reference coordinate system, and its magnitude is equal to the straight-line distance between the antenna and the base station. Let the antenna position be... Since the base station is located at the origin, the direction vector is: d= Normalization involves dividing the direction vector by its magnitude to obtain a unit vector with a magnitude of 1. The unit line-of-sight vector only represents direction and does not contain distance information. The calculation formula is: Understandably, the inverse of a rotation matrix is ​​equal to its transpose (because a rotation matrix is ​​orthogonal), and it is used to transform vectors in a geodetic reference coordinate system back to a rectangular coordinate system. Let R be the rotation matrix from the rectangular coordinate system to the geodetic reference coordinate system, and let R' be its inverse. -1 =RT Then the line-of-sight vector in the rectangular coordinate system is: In the formula, The matrix representing the inverse of the rotation matrix; Represents the line-of-sight vector; This represents the unit line-of-sight vector.

[0066] The Doppler frequency offset suppression method for UAV ad hoc networks provided in this invention calculates and normalizes the direction vector to obtain a unit line-of-sight vector, and then uses the inverse of the rotation matrix to transform it to a rectangular coordinate system, achieving accurate acquisition and coordinate matching of the line-of-sight direction. This method effectively solves the time-varying rotation problem between the UAV system and the Earth system, providing a reliable directional reference for subsequent accurate projection of radial velocity and minimum motion compensation, and significantly improving the accuracy and robustness of Doppler frequency offset suppression.

[0067] Based on any of the above embodiments, determining the speed control command according to the radial velocity includes: A minimum motion compensation speed is generated based on the radial velocity, wherein the minimum motion compensation speed is a motion speed that is only along the direction of the line-of-sight vector and opposite to the direction of the radial velocity; The speed control command is determined based on the minimum motion compensation speed.

[0068] It should be noted that the minimum motion compensation speed is a velocity vector, parallel to the line-of-sight vector, with a magnitude equal to the absolute value of the radial velocity and a direction opposite to the radial velocity. The minimum motion compensation only compensates for the component along the line-of-sight direction, without generating any unnecessary motion perpendicular to it. The speed control command converts the minimum motion compensation speed into a signal format recognizable by the antenna drive mechanism, such as a voltage value, PWM duty cycle, or digital pulse frequency.

[0069] In practical implementation, the compensation direction can be determined based on the sign of the radial velocity. The magnitude of the compensation velocity vector is set to be equal to the absolute value of the radial velocity, and the direction is opposite to the radial velocity.

[0070] The Doppler frequency offset suppression method for UAV ad hoc networks provided in this invention generates a minimum motion compensation velocity that is only along the line-of-sight direction and opposite to the radial velocity, and determines the speed control command accordingly, thereby achieving precise cancellation of Doppler frequency offset at its source. This method avoids lateral redundant motion, minimizes antenna motion, reduces energy consumption and space requirements, and does not rely on pilot signals or complex estimations. It can still quickly and accurately suppress frequency offset under high-speed maneuvering conditions, significantly improving the stability of the communication link.

[0071] Based on any of the above embodiments, determining the speed control command according to the minimum motion compensation speed includes: The velocity component of the minimum motion compensation velocity in the direction of the line-of-sight vector is set to be equal to the negative value of the radial velocity, and the velocity component of the minimum motion compensation velocity in the direction perpendicular to the line-of-sight vector is zero. Based on the negative value of the radial velocity and the line-of-sight vector, a three-dimensional velocity vector is generated in the rectangular coordinate system, and the three-dimensional velocity vector is used as the minimum motion compensation velocity. The minimum motion compensation speed is converted into a speed control command for the mobile antenna.

[0072] It should be noted that the velocity component refers to the projected value of the compensated velocity vector in a specific direction; the direction perpendicular to the line-of-sight vector refers to any direction orthogonal to the line-of-sight vector; the negative value of the radial velocity represents a velocity value equal in magnitude but opposite in direction to the radial velocity. The three-dimensional velocity vector is a velocity vector in a rectangular coordinate system, and its three components correspond to the movement velocity of the antenna in the three axes of the rectangular coordinate system. The speed control command is the specific signal that drives the antenna actuator, such as PWM duty cycle, analog voltage, digital pulse sequence, or CAN bus command.

[0073] In the specific implementation, let the radial velocity be... The line-of-sight vector is (Unit vector in a rectangular coordinate system). Based on the principle of minimum motion compensation, the compensation velocity vector... Two conditions must be met simultaneously: first, the projection of the compensation velocity onto the line-of-sight direction must be equal to the negative value of the radial velocity, i.e., equal in magnitude but opposite in direction; second, the projection of the compensation velocity onto any direction perpendicular to the line-of-sight direction must be zero, i.e., no lateral movement is generated. Therefore, a three-dimensional velocity vector can be directly constructed, with its direction exactly the same as the line-of-sight vector, its magnitude equal to the absolute value of the radial velocity, and its direction opposite to the radial velocity. This three-dimensional velocity vector is the minimum motion compensation velocity. Subsequently, based on the physical characteristics of the antenna drive mechanism (e.g., the voltage-to-speed ratio coefficient, the conversion relationship between pulse frequency and speed, etc.), the minimum motion compensation velocity is converted into specific speed control commands. During the conversion, the components of the compensation velocity on the three axes of the rectangular coordinate system are multiplied by the corresponding conversion coefficients to obtain the signal values ​​required to drive the motors of each axis. Finally, these signal values ​​are packaged according to the drive interface protocol and sent to the antenna drive controller. Through the above steps, it is ensured that the antenna only generates movement along the line-of-sight direction that is equal in magnitude and opposite in direction to the radial velocity, thereby accurately canceling the radial velocity and without generating any lateral redundant movement.

[0074] The Doppler frequency offset suppression method for UAV ad hoc networks provided in this invention achieves minimal motion compensation only along the line-of-sight direction by setting the compensation velocity to be equal to the negative radial velocity in the line-of-sight direction and zero in the vertical direction. This generates a three-dimensional velocity vector in a rectangular coordinate system and converts it into a velocity control command. This avoids lateral redundant motion, reduces antenna movement range and energy consumption, and accurately compensates for radial velocity, significantly suppressing Doppler frequency offset and improving communication link stability in high-speed maneuvering scenarios.

[0075] Based on any of the above embodiments, driving the mobile antenna according to the speed control command includes: According to the speed control command, the mobile antenna is driven to move along the direction of the line-of-sight vector in the rectangular coordinate system, and the movement speed is equal in magnitude and opposite in direction to the radial speed.

[0076] It should be noted that "driving" refers to applying force or torque through an actuator to cause the antenna to move or accelerate; "moving along the line-of-sight vector" means that the antenna's trajectory is always parallel to the line-of-sight vector.

[0077] In practical implementation, speed control commands can be output to the antenna drive controller. The controller drives the antenna to move along the line of sight, with the magnitude of the speed equal to the absolute value of the radial speed, but in the opposite direction. Specifically, the speed control command is sent to the servo controller of the antenna drive unit. The servo controller generates a drive current based on the command, driving a linear motor or voice coil motor to move the antenna. Simultaneously, the actual antenna speed is fed back in real time through position or speed sensors, forming a closed-loop control to ensure that the actual speed accurately tracks the command value.

[0078] It is understandable that driving the mobile antenna to move along the line-of-sight vector in a rectangular coordinate system based on speed control commands can directly achieve physical cancellation of Doppler frequency offset, making the relative radial velocity between the antenna and the base station approach zero.

[0079] The Doppler frequency offset suppression method for UAV ad hoc networks provided in this invention, by driving a mobile antenna to move along the line-of-sight direction at a speed equal in magnitude but opposite in direction to its radial velocity, can precisely cancel the relative radial motion between the UAV and the ground base station from the physical source, making the radial velocity between the antenna and the base station approach zero, thereby effectively suppressing Doppler frequency offset. This method avoids the pilot overhead and tracking lag problems of traditional baseband compensation. Furthermore, because it moves only along the line-of-sight direction without generating lateral redundant displacement, it achieves minimal motion compensation, reduces the antenna's movement range and energy consumption, and significantly improves the stability of the communication link under high-speed maneuvering conditions.

[0080] The above embodiments will be illustrated with a specific example below: Let the fixed installation offset of the origin of the cuboid coordinate system relative to the centroid of the UAV be . Then the position of the mobile antenna relative to the center of mass of the UAV (i.e., the relative position) is: In the formula, Indicates relative position, in meters; Indicates a fixed bias; This indicates the current position of the mobile antenna.

[0081] It should be noted that the antenna position is the absolute spatial coordinate of the mobile antenna in the Earth reference coordinate system. Specifically, the position of the antenna relative to the ground base station (i.e., the antenna position) is: In the formula, Indicates the antenna position, in meters; Represents the rotation matrix; Indicates relative position; This indicates the location of the drone's center of mass.

[0082] Next, after calculating the antenna position, the distance from the base station to the antenna is calculated: In the formula, The unit is meters.

[0083] The unit line-of-sight vector (in geodetic coordinates) pointing from the base station to the antenna: In the formula, ,and .

[0084] Since the antenna actuator moves in a cuboid coordinate system C, the unit line-of-sight vector is transformed into the cuboid coordinate system to obtain the line-of-sight vector: In the formula, The matrix representing the inverse of the rotation matrix; Represents the line-of-sight vector; This represents the unit line-of-sight vector.

[0085] Let the velocity of the UAV's center of mass in the geodetic reference coordinate system (i.e., the velocity of the UAV's center of mass) be... The angular velocity of the UAV in the cuboid coordinate system is The position of the mobile antenna relative to the center of mass of the UAV (i.e., its relative position) is: The additional antenna velocity caused by attitude rotation is .

[0086] Since the antenna-added velocity is described in a cuboid coordinate system, it needs to be obtained through a rotation matrix. Only by transforming to the geodetic reference coordinate system can it be directly added to the centroid velocity vector. Therefore, the resultant velocity of the antenna caused by the UAV's motion in the geodetic reference coordinate system is: In the formula, This represents the active motion speed of the mobile antenna in the cuboid coordinate system, that is, the motion speed generated by the antenna itself through the driving mechanism. The radial velocity caused by the movement of the UAV can be offset by adjusting its size and direction, thereby suppressing the Doppler frequency shift.

[0087] The line-of-sight direction is represented by a unit line-of-sight vector. In the geodetic reference coordinate system, the unit line-of-sight vector from the base station to the mobile antenna is denoted as... Then the rate of change of the distance between the antenna and the base station (i.e., the radial velocity) is the projection of the antenna's resultant velocity onto the line-of-sight direction: (1) The rate of change of the distance from the ground base station to the antenna is: (2) Substitute the expression into the equation and use the line-of-sight vector in the cuboid coordinate system. ,in, Represents the unit line-of-sight vector. Representing the gaze vector, we can obtain: Define the radial velocity caused by the drone's own motion (excluding active antenna motion) as: The rate of change of distance can then be simplified to: Drone Doppler Shift The relationship with radial velocity is: in, For communication carrier frequency, This represents the speed of electromagnetic wave propagation.

[0088] To suppress Doppler frequency shift, it is necessary to make ,Right now: Because only along The directional velocity will change the distance from the base station to the antenna, while the perpendicular velocity will change the distance from the base station to the antenna. The speed will not change the distance, but will only increase unnecessary antenna movement. Therefore, the minimum movement compensation speed is: Substitution get: in, , Indicates a fixed bias. Let be the current position of the moving antenna. Substituting this into the equation yields the complete expression for the compensated velocity: Within each flight control cycle, the minimum motion compensation speed and position command are calculated based on the UAV flight control information, the relative position of the UAV and the base station, and the current antenna position. After compensation, the following are obtained: Therefore, the first-order Doppler frequency shift is suppressed.

[0089] In specific implementations, such as Figure 4 As shown, the ground base station is located at the origin of the coordinate system. The UAV starts from the starting point (200m, 100m, 10m) and flies along a three-dimensional trajectory, passing through points such as (400m, 100m, 18m), and finally reaching the endpoint (1000m, 50m, 75m). This trajectory encompasses typical maneuvers such as forward flight, altitude changes, and horizontal deviation, used to verify the Doppler frequency shift suppression effect of this method under different flight conditions. Figure 5 As shown, the UAV's speed gradually changes over time: the initial speed is approximately 157.5 km / h, then it slowly decreases, dropping to approximately 148.2 km / h at about 14.5 seconds, and finally recovers to 150.0 km / h at 20 seconds. The speed fluctuations are smooth throughout the process, simulating the speed changes of the UAV during typical maneuvers (such as cruise, turning, and deceleration), and is used to verify the adaptability and robustness of the Doppler frequency offset suppression method under different speed conditions. Figure 6 As shown, the curves of Doppler frequency offset over time are compared between the uncompensated and compensated versions using this method. Without compensation, the frequency offset fluctuates significantly, with a maximum value exceeding 1000Hz, severely impacting communication demodulation performance. However, after the movable antenna moves in the opposite direction at the minimum compensation speed, the frequency offset is stably suppressed to below 10Hz, verifying the effectiveness of this method in suppressing Doppler frequency offset under high-speed maneuvering conditions and significantly improving link stability.

[0090] The following describes the UAV self-organizing network Doppler frequency offset suppression device provided by the present invention. The UAV self-organizing network Doppler frequency offset suppression device described below can be referred to in correspondence with the UAV self-organizing network Doppler frequency offset suppression method described above. Figure 7 As shown, the UAV self-organizing network Doppler frequency offset suppression device includes: The acquisition module 10 is used to acquire the current flight control information of the UAV in the ground reference coordinate system and the current position of the mobile antenna in the rectangular coordinate system, wherein the rectangular coordinate system is aligned with the body coordinate system of the UAV. The calculation module 20 is used to calculate the radial velocity caused by the movement of the UAV based on the current flight control information and the current position, and to determine the speed control command based on the radial velocity; The suppression module 30 is used to drive the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

[0091] Figure 8 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 8 As shown, the electronic device may include a processor 810, a communications interface 820, a memory 830, and a communication bus 840, wherein the processor 810, communications interface 820, and memory 830 communicate with each other via the communication bus 840. The processor 810 can call logical instructions in the memory 830 to execute a Doppler frequency offset suppression method for UAV ad hoc networks. This method includes: acquiring the current flight control information of the UAV in a ground reference coordinate system, and acquiring the current position of the mobile antenna in a rectangular coordinate system, wherein the rectangular coordinate system is aligned with the UAV's body coordinate system; calculating the radial velocity caused by the UAV's motion based on the current flight control information and the current position, and determining a speed control command based on the radial velocity; and driving the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

[0092] Furthermore, the logical instructions in the aforementioned memory 830 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0093] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the UAV ad hoc network Doppler frequency offset suppression method provided by the above methods. The method includes: acquiring the current flight control information of the UAV in a ground reference coordinate system and acquiring the current position of the mobile antenna in a rectangular coordinate system, wherein the rectangular coordinate system is aligned with the body coordinate system of the UAV; calculating the radial velocity caused by the movement of the UAV based on the current flight control information and the current position, and determining a speed control command based on the radial velocity; and driving the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

[0094] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program implements the Doppler frequency offset suppression method for UAV ad hoc networks provided by the above methods. The method includes: acquiring the current flight control information of the UAV in a ground reference coordinate system and acquiring the current position of the mobile antenna in a rectangular coordinate system, wherein the rectangular coordinate system is aligned with the body coordinate system of the UAV; calculating the radial velocity caused by the movement of the UAV based on the current flight control information and the current position, and determining a speed control command based on the radial velocity; and driving the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

[0095] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0096] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0097] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for suppressing Doppler frequency offset in unmanned aerial vehicle (UAV) self-organizing networks, characterized in that, Applied to drones, the drones being equipped with a mobile antenna, including: The current flight control information of the UAV in the ground reference coordinate system is obtained, and the current position of the mobile antenna in the rectangular coordinate system is obtained, wherein the rectangular coordinate system is aligned with the body coordinate system of the UAV. Based on the current flight control information and the current position, calculate the radial velocity caused by the movement of the UAV, and determine the speed control command based on the radial velocity; The mobile antenna is driven according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

2. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 1, characterized in that, The process of obtaining the current flight control information of the UAV in the Earth reference coordinate system includes: A geodetic reference coordinate system is constructed using ground base stations as the origin. The position of the center of mass of the UAV in the geodetic coordinate system is obtained, as well as the velocity of the UAV's center of mass, attitude angles, and Euler angular velocity, wherein the attitude angles include the roll angle, pitch angle, and yaw angle of the UAV. The current flight control information is determined based on the UAV's center of mass position, the UAV's center of mass velocity, the UAV's attitude angle, and the Euler angular velocity.

3. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 1, characterized in that, The calculation of the radial velocity caused by the movement of the UAV based on the current flight control information and the current position includes: Based on the UAV attitude angles in the current flight control information, calculate the rotation matrix from the rectangular coordinate system to the geodetic reference coordinate system; Based on the current flight control information and the current position, determine the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system; Based on the current position, the Euler angular velocity in the current flight control information, and the rotation matrix, calculate the antenna-added velocity caused by the UAV's attitude rotation; Based on the UAV's center of mass velocity, the antenna-attached velocity, and the line-of-sight vector in the current flight control information, the radial velocity caused by the UAV's motion is calculated.

4. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 3, characterized in that, The step of determining the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system based on the current flight control information and the current position includes: The origin of the rectangular coordinate system is set to a fixed offset relative to the centroid of the UAV; Based on the current position and the fixed offset, calculate the relative position of the mobile antenna with respect to the center of mass of the UAV; Based on the centroid position, rotation matrix, and relative position in the current flight control information, calculate the antenna position of the mobile antenna in the geodetic reference coordinate system. Based on the antenna position, the line-of-sight vector from the mobile antenna to the ground base station is determined in the rectangular coordinate system.

5. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 4, characterized in that, Determining the line-of-sight vector from the mobile antenna to the ground base station in the rectangular coordinate system based on the antenna position includes: Based on the antenna location, calculate the direction vector from the ground base station to the mobile antenna; The direction vector is normalized to obtain a unit line-of-sight vector; Using the inverse of the rotation matrix, the unit line-of-sight vector is transformed into the rectangular coordinate system to obtain the line-of-sight vector in the rectangular coordinate system.

6. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 3, characterized in that, The step of determining the speed control command based on the radial velocity includes: A minimum motion compensation speed is generated based on the radial velocity, wherein the minimum motion compensation speed is a motion speed that is only along the direction of the line-of-sight vector and opposite to the direction of the radial velocity; The speed control command is determined based on the minimum motion compensation speed.

7. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 6, characterized in that, The step of determining the speed control command based on the minimum motion compensation speed includes: The velocity component of the minimum motion compensation velocity in the direction of the line-of-sight vector is set to be equal to the negative value of the radial velocity, and the velocity component of the minimum motion compensation velocity in the direction perpendicular to the line-of-sight vector is zero. Based on the negative value of the radial velocity and the line-of-sight vector, a three-dimensional velocity vector is generated in the rectangular coordinate system, and the three-dimensional velocity vector is used as the minimum motion compensation velocity. The minimum motion compensation speed is converted into a speed control command for the mobile antenna.

8. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 3, characterized in that, The step of driving the mobile antenna according to the speed control command includes: According to the speed control command, the mobile antenna is driven to move along the direction of the line-of-sight vector in the rectangular coordinate system, and the movement speed is equal in magnitude and opposite in direction to the radial speed.

9. The method for suppressing Doppler frequency offset in UAV self-organizing networks according to claim 1, characterized in that, The mobile antenna has three degrees of freedom of movement within the rectangular coordinate system.

10. A Doppler frequency offset suppression device for unmanned aerial vehicle (UAV) self-organizing networks, characterized in that, include: The acquisition module is used to acquire the current flight control information of the UAV in the ground reference coordinate system, and to acquire the current position of the mobile antenna in the rectangular coordinate system, wherein the rectangular coordinate system is aligned with the UAV's body coordinate system. The calculation module is used to calculate the radial velocity caused by the movement of the UAV based on the current flight control information and the current position, and to determine the speed control command based on the radial velocity; The suppression module is used to drive the mobile antenna according to the speed control command to suppress the Doppler frequency offset of the communication link between the UAV and the ground base station.

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