A data link simulation method under a complex electromagnetic interference environment

Abstract

The application discloses a data link simulation method in a complex electromagnetic interference environment and relates to the field of computer simulation and unmanned aerial vehicle communication anti-interference evaluation; solves the problem that a traditional simulation method cannot accurately and dynamically reproduce the performance of an unmanned aerial vehicle data link in a complex electromagnetic interference environment; the application starts a time step cycle by configuring a multi-interference style and a behavior strategy model, calculates spatial geometric parameters at each simulation time and generates a signal-to-interference channel impulse response matrix; performs time-frequency transformation on interference components to obtain energy distribution density, performs integral convolution on the energy distribution density and a signal separability function obtained by convolution of a sending symbol resolution characteristic function and a channel scattering function, and calculates a packet error rate; compares the packet error rate with a threshold value, triggers a behavior model to simulate protection and adaptive actions and updates a state, and high-fidelity simulation of a dynamic response process of the unmanned aerial vehicle data link in the complex electromagnetic interference is realized.

Description

Technical Field

[0001] This invention belongs to the field of computer simulation and anti-interference assessment of UAV communication, specifically a data link simulation method under complex electromagnetic interference environment. Background Technology

[0002] The UAV data link is the core communication channel for transmitting remote control commands and telemetry data back between the UAV and the ground control station. Its reliability directly determines the UAV's flight safety and mission execution capability. In complex electromagnetic interference environments, the data link may face various types of interference from multiple sources, including broadband noise suppression interference, frequency sweeping interference, and deceptive interference. These interference signals, after propagating through space, are superimposed on the useful signals at the UAV receiver, severely affecting the communication quality of the link.

[0003] Real-world flight testing is a direct means of evaluating the anti-interference performance of data links, but it has limitations such as high testing costs, high experimental risks, and the inability to reproduce the electromagnetic environment. Computer simulation methods can simulate the working state of data links under various electromagnetic interference conditions in a virtual environment, and have the advantages of low cost, repeatability, and controllable parameters, making them an important tool for anti-interference assessment.

[0004] Developing a high-precision UAV data link simulation method requires addressing three key technical challenges. First, how to uniformly model the spatial propagation channel shared by multiple interference sources and useful signals to accurately reflect the effects of multipath propagation, Doppler effects, and antenna pattern modulation on the interference signal. Second, how to quickly and accurately calculate performance indicators such as the link packet error rate from the complex channel response, establishing a quantitative mapping relationship between interference effects and link quality. Third, how to simulate the strategic behavioral responses of UAVs after link quality degradation in the simulation, to reproduce the dynamic coupling relationship between interference effects and platform behavior in real-world adversarial scenarios.

[0005] The following problems exist in the existing technology:

[0006] In existing simulation methods, the calculation of spatial geometric parameters usually uses preset fixed position points or simplified motion models, without considering the dynamic and continuous changes in the spatial position of the UAV and interference sources during actual movement, resulting in deviations between the spatial geometric relationship at the simulation moment and the actual flight state.

[0007] Traditional simulation methods generate the communication channel impulse response and the interference channel impulse response independently and then simply superimpose them. This fails to align all interference channel impulse responses to a unified time reference in the time delay domain before superposition. Due to the different spatial locations of each interference source and the ground control station, the time delays of each interference signal arriving at the UAV receiver vary. Direct superposition without alignment will distort the time delay relationship of each interference component in the communication channel impulse response matrix, and will not accurately reflect the true energy distribution of the interference signal on the time delay Doppler plane.

[0008] Existing simulation methods typically estimate packet error rate based on signal-to-interference-plus-noise ratio (SINR) thresholds or obtain statistical packet error rates through extensive waveform-level Monte Carlo simulations. However, the SINR threshold method cannot reflect the fine structure of the interference signal in the time-delay Doppler plane and its interaction with the receiver demodulation process, resulting in low evaluation accuracy. Monte Carlo simulations are computationally intensive and cannot meet the real-time requirements of dynamic simulations. Furthermore, existing methods lack analytical mapping techniques from physical channel response to link packet error rate.

[0009] In existing simulation methods, UAV trajectories are usually pre-fixed or executed according to scripts, without simulating the autonomous behavior adjustments made by the UAV based on its own protection logic when the link quality deteriorates. As a result, the simulation results cannot reflect the dynamic causal chain between interference, performance degradation and platform behavior response in real confrontation. Summary of the Invention

[0010] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes a data link simulation method under complex electromagnetic interference environment to solve the above-mentioned technical problem.

[0011] The first aspect of this invention provides a data link simulation method under complex electromagnetic interference environment, comprising the following steps:

[0012] S1: Configure the initial parameters for the UAV data link simulation. The initial parameters are the UAV's preset waypoint sequence and attitude parameters, the UAV's onboard data link terminal's antenna pattern parameters, the location and antenna pattern parameters of the ground control station, the preset motion paths of at least two interference sources and their antenna pattern parameters and interference patterns, the modulation method used by the data link, the UAV's behavior strategy model, and the preset total simulation duration and time step interval.

[0013] S2: Start the time-stepping loop of the UAV data link simulation. At each simulation moment, based on the UAV's preset waypoint sequence, the location of the ground control station, and the preset motion path of the interference source, calculate the line-of-sight distance and angle of arrival from the ground control station to the UAV, the line-of-sight distance and angle of arrival from each interference source to the UAV, and the relative radial velocity of each link as spatial geometric parameters.

[0014] S3: Based on the spatial geometric parameters, the antenna pattern parameters of the UAV airborne data link terminal, the antenna pattern parameters of the ground control station, and the antenna pattern parameters of each interference source, a method combining the free space propagation model and the statistical multipath model is used to generate the communication channel impulse response from the ground control station to the UAV and the interference channel impulse response from each interference source to the UAV. All interference channel impulse responses are aligned in the time delay domain and superimposed with the communication channel impulse response to form an interference channel impulse response matrix.

[0015] S4: Perform time-frequency transformation on the interference component in the signal-to-interference channel impulse response matrix to obtain the energy distribution density; convolve the time delay Doppler resolution characteristic function of each transmitted symbol in the transmitted symbol sequence generated by the modulation method used in the data link with the communication channel scattering function obtained by Fourier transform of the communication channel impulse response to obtain the signal separability function; perform integral convolution of the energy distribution density and the signal separability function in the time-frequency region of each transmitted symbol, and multiply the integral results of all transmitted symbols together to obtain the packet error rate of the UAV data link at the current simulation time;

[0016] S5: Compare the packet error rate with a preset first packet error rate threshold and a preset second packet error rate threshold; when the packet error rate exceeds the first packet error rate threshold, trigger the UAV behavior strategy model to simulate link loss protection behavior and forced return behavior; when the packet error rate exceeds the second packet error rate threshold, trigger the UAV behavior strategy model to simulate task load adaptive behavior, and update the UAV's spatial position and attitude parameters according to the simulated behavior.

[0017] Preferably, in step S1, the interference source's interference patterns include broadband noise suppression interference, frequency sweeping interference, and spoofing interference; wherein, the configuration parameters of broadband noise suppression interference include noise bandwidth and power spectral density; the configuration parameters of frequency sweeping interference include frequency sweep start frequency, frequency sweep end frequency, frequency sweep period, and frequency sweeping mode; and the spoofing interference uses the same modulation method as the data link, and its configuration parameters include synchronization parameters and spoofing data content.

[0018] The UAV behavior strategy model stores behavior rules in the form of conditional action pairs, where the condition consists of a packet error rate threshold and a duration, and the action consists of flight control commands and mission payload commands.

[0019] Preferably, step S2 includes the following steps:

[0020] Based on the UAV's preset waypoint sequence, the spatial position of the UAV at the current simulation time is calculated by interpolation; based on the preset motion paths of the interference sources, the spatial positions of each interference source at the current simulation time are calculated by interpolation.

[0021] The angle of arrival includes the azimuth and the elevation angle; the azimuth is measured clockwise with true north as the zero-degree reference; the elevation angle is measured with the local horizontal plane as the zero-degree reference, and upward is positive.

[0022] The relative radial velocity of each link is the projection of the difference between the velocity vector of the UAV and the velocity vector of the other end of the corresponding link onto the line of sight of both. The relative radial velocity is positive when the relative distance decreases and negative when the relative distance increases.

[0023] Preferably, in step S3, generating the communication channel impulse response from the ground control station to the UAV and the interference channel impulse response from each interference source to the UAV includes the following steps:

[0024] Based on the line-of-sight distance and angle of arrival from the ground control station to the UAV, the free space path loss is calculated according to the line-of-sight distance; at the same time, the antenna pattern parameters of the UAV's onboard data link terminal and the antenna pattern parameters of the ground control station are queried according to the angle of arrival to obtain the receiving antenna gain and transmitting antenna gain; based on the free space path loss, transmitting antenna gain and receiving antenna gain, the communication line-of-sight path component is formed.

[0025] Based on the line-of-sight distance and angle of arrival of each interference source to the UAV, the free space path loss is calculated according to the line-of-sight distance; at the same time, the antenna pattern parameters of the UAV's onboard data link terminal and the antenna pattern parameters of the interference source are queried according to the angle of arrival to obtain the receiving antenna gain and transmitting antenna gain; based on the free space path loss, transmitting antenna gain and receiving antenna gain, the interference line-of-sight path component is formed.

[0026] In addition to the communication line-of-sight path component and the interference line-of-sight path component, a multipath component is generated based on a preset multipath channel model.

[0027] For each path component among the communication line-of-sight path component, the interference line-of-sight path component, and the multipath component, the Doppler frequency shift is calculated based on the relative radial velocity of the corresponding link in the spatial geometry parameters, and is used as the Doppler frequency shift of that path component.

[0028] Arranging the communication line-of-sight path components and their multipath components in the time delay domain forms the communication channel impulse response; arranging the interference line-of-sight path components and their multipath components in the time delay domain forms the interference channel impulse response.

[0029] Preferably, in step S3, the step of aligning all interference channel impulse responses in the time delay domain and superimposing them with the communication channel impulse responses to form an interference channel impulse response matrix includes the following steps:

[0030] The zero-delay point of all the impulse responses of the aforementioned interference channels is unified to the start time of the signal transmitted by the ground control station, thus completing the time delay domain alignment;

[0031] At each time delay tap position after alignment, the complex value of the communication channel impulse response at that time delay tap is added to the complex value of each interference channel impulse response at that time delay tap to obtain the superimposed complex value of that time delay tap.

[0032] The superimposed complex values ​​of all time delay taps are arranged to form the impulse response matrix of the signal-to-interference channel.

[0033] Preferably, in step S4, the signal separability function The formula is:

[0034]

[0035] Where τ and v are the independent variables of the signal separability function, representing the time delay and Doppler frequency, respectively. and Let τ and v be the integral variables; The time delay Doppler resolution characteristic function of the transmitted symbol at the integration position The value at that location, The scattering function of the communication channel at the integration position The value at t represents the current simulation time.

[0036] Preferably, in step S4, the packet error rate PER(t) of the UAV data link at the current simulation moment includes the following steps:

[0037]

[0038] in, The energy distribution density, Let M be the detection area of ​​the m-th transmitted symbol on the time-delay Doppler plane, where M is the total number of transmitted symbols.

[0039] Preferably, step S5 includes the following steps:

[0040] When the packet error rate exceeds the first packet error rate threshold, the link loss protection behavior is triggered; the link loss protection behavior includes abandoning the current waypoint task, flying along a preset circling path with the current spatial location as the center, and starting the link loss timer;

[0041] If the packet error rate falls below the first packet error rate threshold before the link loss timer reaches the preset maximum tolerance time, the link loss protection behavior is lifted and the execution of subsequent waypoint tasks in the preset waypoint sequence is resumed; if the packet error rate still does not fall below the first packet error rate threshold when the link loss timer reaches the maximum tolerance time, a forced return flight behavior is triggered, which includes flying along a preset return path to a preset return point.

[0042] When the packet error rate exceeds the second packet error rate threshold, the task load adaptive behavior is triggered; the task load adaptive behavior includes reducing the video encoding bitrate to a preset low bitrate level and switching the communication mode to a preset anti-interference communication mode.

[0043] When the packet error rate falls below the second packet error rate threshold and continues for a preset recovery time, the task load adaptive behavior is deactivated and the system returns to normal bit rate and normal communication mode.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] This invention uses interpolation calculations based on a preset waypoint sequence and preset motion path to dynamically calculate the spatial positions of the UAV and various interference sources at each simulation moment by searching and linearly interpolating within a time interval. At the same time, it calculates the line-of-sight distance, azimuth angle, pitch angle, and relative radial velocity as spatial geometric parameters, ensuring the dynamic continuity of spatial geometric relationships and the accuracy of calculations during the simulation process.

[0046] This invention unifies the zero-delay point of all interference channel impulse responses to the starting time of the ground control station's transmitted signal through a time-delay domain alignment operation. Each interference source calculates its time-delay offset based on the difference between its distance from the ground control station to the UAV's line of sight and then shifts and aligns it. After alignment, it is superimposed with the communication channel impulse response at each time-delay tap position to form a physically unified communication channel impulse response matrix, ensuring the authenticity of the energy distribution of the interference components on the time-delay Doppler plane.

[0047] This invention constructs a signal separability function by performing a two-dimensional convolution between the delay Doppler resolution characteristic function of the transmitted symbol and the scattering function of the communication channel. Then, it performs an integral convolution and multiplication of the energy distribution density and the signal separability function within the detection region of each transmitted symbol, and directly calculates the packet error rate analytically without the need for waveform-by-waveform simulation. This achieves a fast and accurate mapping from the physical channel response to the link packet error rate.

[0048] This invention compares the packet error rate with a preset first packet error rate threshold and a second packet error rate threshold. When the packet error rate exceeds the first packet error rate threshold, it triggers link loss protection behavior and forced return behavior. When the packet error rate exceeds the second packet error rate threshold, it triggers task payload adaptive behavior. Based on the simulated behavior, it updates the UAV's spatial position and attitude parameters and feeds them back to the next simulation moment, thus realizing dynamic closed-loop simulation between interference, performance degradation and platform behavior response. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0050] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0051] Please see Figure 1 This invention provides a data link simulation method for complex electromagnetic interference environments, comprising the following steps:

[0052] S1: Configure the initial parameters for the UAV data link simulation. The initial parameters are the UAV's preset waypoint sequence and attitude parameters, the UAV's onboard data link terminal's antenna pattern parameters, the location and antenna pattern parameters of the ground control station, the preset motion paths of at least two interference sources and their antenna pattern parameters and interference patterns, the modulation method used by the data link, the UAV's behavior strategy model, and the preset total simulation duration and time step interval.

[0053] S2: Start the time-stepping loop of the UAV data link simulation. At each simulation moment, based on the UAV's preset waypoint sequence, the location of the ground control station, and the preset motion path of the interference source, calculate the line-of-sight distance and angle of arrival from the ground control station to the UAV, the line-of-sight distance and angle of arrival from each interference source to the UAV, and the relative radial velocity of each link as spatial geometric parameters.

[0054] S3: Based on the spatial geometric parameters, the antenna pattern parameters of the UAV airborne data link terminal, the antenna pattern parameters of the ground control station, and the antenna pattern parameters of each interference source, a method combining the free space propagation model and the statistical multipath model is used to generate the communication channel impulse response from the ground control station to the UAV and the interference channel impulse response from each interference source to the UAV. All interference channel impulse responses are aligned in the time delay domain and superimposed with the communication channel impulse response to form an interference channel impulse response matrix.

[0055] S4: Perform time-frequency transformation on the interference component in the signal-to-interference channel impulse response matrix to obtain the energy distribution density; convolve the time delay Doppler resolution characteristic function of each transmitted symbol in the transmitted symbol sequence generated by the modulation method used in the data link with the communication channel scattering function obtained by Fourier transform of the communication channel impulse response to obtain the signal separability function; perform integral convolution of the energy distribution density and the signal separability function in the time-frequency region of each transmitted symbol, and multiply the integral results of all transmitted symbols together to obtain the packet error rate of the UAV data link at the current simulation time;

[0056] S5: Compare the packet error rate with a preset first packet error rate threshold and a preset second packet error rate threshold; when the packet error rate exceeds the first packet error rate threshold, trigger the UAV behavior strategy model to simulate link loss protection behavior and forced return behavior; when the packet error rate exceeds the second packet error rate threshold, trigger the UAV behavior strategy model to simulate task load adaptive behavior, and update the UAV's spatial position and attitude parameters according to the simulated behavior.

[0057] Specifically, the initial simulation parameters for the UAV data link are configured, including the UAV's preset waypoint sequence and attitude parameters, the antenna pattern parameters of the UAV's onboard data link terminal, the location and antenna pattern parameters of the ground control station, the preset motion paths of at least two interference sources and their antenna pattern parameters and interference patterns, the modulation scheme used by the data link, the UAV's behavior strategy model, and the total simulation duration and time step interval. A time stepping loop is initiated, and at each simulation moment, spatial geometric parameters are dynamically calculated based on the preset waypoint sequence and the preset motion paths of the interference sources, including the line-of-sight distance and angle of arrival from the ground control station to the UAV and from each interference source to the UAV, and the relative radial velocity of each link. Based on the spatial geometric parameters and the antenna pattern parameters of each communication terminal, the communication channel impulse response and the impulse responses of each interference channel are generated. All interference channel impulse responses are aligned in the time delay domain and superimposed with the communication channel impulse response to form the signal-to-interference channel impulse response matrix. The energy distribution density is obtained by performing a time-frequency transformation on the interference components in the matrix. The signal separability function is obtained by convolving the time-delay Doppler resolution characteristic function of each symbol in the transmitted symbol sequence generated by the modulation method used in the data link with the scattering function of the communication channel impulse response. The energy distribution density and the signal separability function are then integrally convolved in the time-frequency region of each symbol, and the integral results of all symbols are multiplied together to obtain the packet error rate of the UAV data link at the current simulation moment. The packet error rate is compared with a preset first packet error rate threshold and a second packet error rate threshold. When the first packet error rate threshold is exceeded, the UAV behavior strategy model is triggered to simulate link loss protection behavior and forced return behavior. When the second packet error rate threshold is exceeded, the simulated task payload adaptive behavior is triggered. The UAV's spatial position and attitude parameters are updated according to the simulated behavior and fed back to the next simulation moment, forming a dynamic closed-loop simulation.

[0058] In one embodiment of the present invention, in step S1, the interference style of the interference source includes broadband noise suppression interference, frequency sweeping interference, and spoofing interference; wherein, the configuration parameters of broadband noise suppression interference include noise bandwidth and power spectral density; the configuration parameters of frequency sweeping interference include frequency sweep start frequency, frequency sweep end frequency, frequency sweep period, and frequency sweeping mode; and the spoofing interference adopts the same modulation method as the data link, and its configuration parameters include synchronization parameters and spoofing data content.

[0059] The UAV behavior strategy model stores behavior rules in the form of conditional action pairs, where the condition consists of a packet error rate threshold and a duration, and the action consists of flight control commands and mission payload commands.

[0060] Specifically, the system reads the UAV's preset waypoint sequence and attitude parameters from the UAV flight plan file. Each line in the file corresponds to complete information about a waypoint. The preset waypoint sequence consists of a set of three-dimensional spatial coordinate points arranged in chronological order. Each waypoint includes longitude, latitude, altitude, and the expected arrival time at that waypoint. The attitude parameters include the UAV's pitch, roll, and yaw angles at each waypoint.

[0061] A UAV-borne data link terminal refers to a communication device installed on a UAV, used to establish a data link with a ground control station. This terminal includes an antenna and a receiver. Antenna pattern parameters describe the radiation and reception gain characteristics of the antenna in different spatial directions. The antenna pattern parameters of the UAV-borne data link terminal are loaded in the form of an antenna pattern data file. This file is a pre-prepared text file containing a three-dimensional gain data table. Each row contains the azimuth angle, elevation angle, and the corresponding antenna gain value. The azimuth angle covers a range of 0 to 360 degrees, and the elevation angle covers a range of -90 to +90 degrees, with a typical angular resolution of 1 degree. The unit of antenna gain is decibels (dB). When querying antenna gain, if the azimuth or elevation angle value of the angle of arrival is not on the angle grid point of the discrete data table, a bilinear interpolation method is used to perform two-dimensional interpolation using the gain values ​​of the four adjacent grid points around the angle to calculate the corresponding gain value. If the queried angle happens to be on the angle grid point of the data table, the gain value corresponding to that angle is directly read. The antenna pattern parameters of the ground control station and each interference source are also loaded in the form of antenna pattern data files, with each interference source corresponding to an independent antenna pattern data file.

[0062] The location of the ground control station is represented by three-dimensional coordinates of longitude, latitude, and altitude. These location parameters are input by the operator through the simulation configuration interface or read from a preset scenario file and remain fixed throughout the simulation.

[0063] Interference sources are physical entities capable of emitting electromagnetic interference signals, including three types: ground-based fixed jamming stations, vehicle-mounted mobile jamming platforms, and aerial jamming drones. Each type of interference source is independently configured according to its preset motion path, antenna pattern parameters, and interference pattern.

[0064] The preset motion path configuration for each jamming source is the same as the preset waypoint sequence for the UAV, which is a set of three-dimensional spatial coordinate points arranged in chronological order. The preset motion path for each jamming source is configured independently and read from a preset scenario file. For example, if the jamming source is a ground-based fixed jamming station, its preset motion path is a fixed three-dimensional coordinate point that does not change over time; if the jamming source is a vehicle-mounted mobile jamming platform, its preset motion path is a set of coordinate points traveling at a constant speed of 40 kilometers per hour along a road.

[0065] Interference pattern is a key parameter describing the waveform characteristics of the interference signal. Interference patterns from various sources include broadband noise suppression interference, frequency sweeping interference, and deceptive interference. The interference pattern and configuration parameters are specified by the operator for each interference source individually through the simulation configuration interface, or read from a preset scenario file.

[0066] The configuration parameters for broadband noise suppression jamming include noise bandwidth and power spectral density. Noise bandwidth determines the frequency range covered by the jamming signal, measured in megahertz (MHz). Power spectral density determines the jamming power per unit bandwidth, measured in decibels per milliwatt (dW / MHz).

[0067] The configuration parameters for frequency sweeping jamming include the sweep start frequency, sweep end frequency, sweep period, and sweep mode. The sweep start frequency and sweep end frequency together define the frequency range swept by the jamming signal, both measured in Hertz (Hz). The sweep period defines the time required for one complete sweep, measured in seconds. The sweep mode defines how the instantaneous frequency of the jamming signal changes over time, including linear and logarithmic sweeps. In a linear sweep, the instantaneous frequency of the jamming signal changes linearly with time. In a logarithmic sweep, the instantaneous frequency of the jamming signal changes logarithmically with time.

[0068] The deceptive jamming employs the same modulation scheme as the data link, and its configuration parameters include synchronization parameters and deceptive data content. Synchronization parameters ensure that the deceptive jamming signal is synchronized with the real communication signal in time, frequency, and code phase, including carrier frequency offset, symbol timing offset, and spreading code phase offset. The carrier frequency offset is the difference between the carrier frequency of the deceptive jamming signal and the carrier frequency of the real communication signal, measured in Hertz. The symbol timing offset is the time offset between the start time of the deceptive jamming signal symbol and the start time of the real communication signal symbol, measured in microseconds. The spreading code phase offset is the phase difference between the spreading code of the deceptive jamming signal and the spreading code of the real communication signal, measured in chips. The deceptive data content consists of false information carried in the jamming signal, used to mislead the UAV into executing incorrect commands or receiving false data. Both the synchronization parameters and the deceptive data content are preset by the operator based on the simulation scenario.

[0069] The modulation scheme used in the data link is selected from a preset list of modulation schemes. The preset list of modulation schemes includes quadrature phase shift keying modulation, hexadecimal quadrature amplitude modulation, orthogonal frequency division multiplexing modulation, and direct sequence spread spectrum modulation.

[0070] The UAV behavior strategy model stores behavior rules in the form of condition-action pairs, which are loaded into a pre-defined behavior rule file. Each condition-action pair contains a condition field and an action field. The condition field includes a packet error rate threshold subfield and a duration subfield, while the action field includes a flight control command subfield and a mission payload command subfield. Each behavior rule consists of one condition and one action. The condition consists of a packet error rate threshold and a duration. The action consists of a flight control command and a mission payload command; the flight control command types include abandoning the current waypoint, hovering, returning to home, and restoring the waypoint; the mission payload command types include reducing the video encoding bitrate, switching communication modes, and restoring communication modes.

[0071] For example, in the condition section of a typical link loss protection behavior rule, the packet error rate threshold is 0.3, and the duration is 2.0 seconds. The action section includes flight control commands to abandon the current waypoint and a hovering command. The hovering command has a hovering radius of 100 meters and a hovering altitude of 50 meters above the current position. This rule means that when the uplink data link packet error rate exceeds 0.3 for 2.0 seconds, the UAV abandons the currently executing waypoint task and hovers along a circular path with a radius of 100 meters, centered on the current spatial position, at a hovering altitude of 50 meters above the current altitude.

[0072] The total simulation duration is set based on the duration of the hypothetical scenario, in seconds. The selection of the time step interval must satisfy the constraint of the channel coherence time. Channel coherence time The largest Doppler frequency shift The maximum relative radial velocity between the UAV and the ground control station or interference source and signal center frequency Decision, that is Where the speed of light c is 3.0 × Meters per second. For example, for the center frequency of a signal. The maximum relative radial velocity between the UAV and the ground control station or interference source is 2400 MHz. Calculations were performed for scenarios with speeds not exceeding 100 kilometers per hour. Approximately 222.4 Hz, The time step interval is approximately 2.25 milliseconds. The time step interval should be selected as one-quarter to one-tenth of the channel coherence time; therefore, the time step interval can be configured to 0.5 milliseconds. The total simulation duration can be configured to 600 seconds, at which point the entire simulation process contains approximately 1.2 million simulation moments.

[0073] In one embodiment of the present invention, step S2 includes the following steps:

[0074] Based on the UAV's preset waypoint sequence, the spatial position of the UAV at the current simulation time is calculated by interpolation; based on the preset motion paths of the interference sources, the spatial positions of each interference source at the current simulation time are calculated by interpolation.

[0075] The angle of arrival includes the azimuth and the elevation angle; the azimuth is measured clockwise with true north as the zero-degree reference; the elevation angle is measured with the local horizontal plane as the zero-degree reference, and upward is positive.

[0076] The relative radial velocity of each link is the projection of the difference between the velocity vector of the UAV and the velocity vector of the other end of the corresponding link onto the line of sight of both. The relative radial velocity is positive when the relative distance decreases and negative when the relative distance increases.

[0077] Specifically, after configuring the initial parameters for the UAV data link simulation, the time-stepping loop of the UAV data link simulation is initiated. UAV data link simulation refers to the calculation process of simulating the working state and performance of the data link between the UAV and the ground control station under complex electromagnetic interference environments using a computer program. The time-stepping loop means that the simulation program advances the simulation clock hour by hour, starting from simulation time zero, according to a preset time step interval, and executes a complete calculation process at each simulation time point until the simulation clock reaches the preset total simulation duration.

[0078] At each simulation moment, based on the UAV's preset waypoint sequence, the time interval in which the current simulation moment occurs is found, that is, the arrival time of the previous waypoint among two adjacent waypoints. The arrival time of the next waypoint is less than or equal to the current simulation time t. Greater than the current simulation time t. The spatial coordinates of the previous waypoint are: The spatial coordinates of the next waypoint are The interpolation scaling factor is calculated. Finally, the spatial coordinates of the UAV at the current simulation moment are obtained. ,Right now , , .

[0079] If the current simulation time coincides with the arrival time of a waypoint, the spatial coordinates of that waypoint are directly taken as the UAV's spatial position. The UAV's pitch, roll, and yaw angles are calculated using the same method as spatial position interpolation, based on the attitude parameters and corresponding times of two adjacent waypoints in the preset waypoint sequence. For each interference source, its three-dimensional spatial coordinates at the current simulation time are calculated using the same time interval lookup and linear interpolation method, based on its preset motion path. The ground control station's position remains fixed throughout the simulation; its configured three-dimensional coordinates are directly taken as its current spatial position, denoted as [missing information]. .

[0080] For the link between the ground control station and the drone, line-of-sight distance The Euclidean distance between the spatial location of the ground control station and the spatial location of the UAV is... Angle of arrival includes azimuth. and pitch angle ; Calculate the northward coordinate difference Eastward coordinate difference height difference ; The calculation is performed using a two-parameter arctangent function. With due north as the zero-degree reference, measurements are taken clockwise, and the value range is from 0 degrees to 360 degrees. The local horizontal plane is used as the zero-degree reference, with upwards being positive, and the value range is -90 degrees to +90 degrees. For each interference source to the UAV link, the spatial coordinates of the interference source are: The same method was used to calculate the line-of-sight distance between the interference source and the drone. Azimuth and pitch angle .

[0081] The velocity vector of the drone at the current simulation moment The calculation formula is as follows , , ,in , and , This represents the arrival time and spatial coordinates of two adjacent waypoints within the time interval of the current simulation moment. The ground control station is a fixed station, and its velocity vector is zero. For each interference source, its velocity vector is also obtained by differential calculation of adjacent coordinate points in its preset motion path. If a certain interference source is a fixed interference station, its velocity vector is zero.

[0082] Taking the connection between the ground control station and the UAV as an example, the unit vector in the line-of-sight direction... ,in, , , Let these be the components of the unit vector along the three coordinate axes, i.e. , , Relative radial velocity This is the projection of the drone's velocity vector onto the line-of-sight direction, i.e. The relative radial velocity is positive when the relative distance between the UAV and the other end of the link decreases, and negative when the relative distance increases. The relative radial velocity from each interference source to the UAV link is calculated using the same method.

[0083] In one embodiment of the present invention, step S3, generating the communication channel impulse response from the ground control station to the UAV and the interference channel impulse response from each interference source to the UAV, includes the following steps:

[0084] Based on the line-of-sight distance and angle of arrival from the ground control station to the UAV, the free space path loss is calculated according to the line-of-sight distance; at the same time, the antenna pattern parameters of the UAV's onboard data link terminal and the antenna pattern parameters of the ground control station are queried according to the angle of arrival to obtain the receiving antenna gain and transmitting antenna gain; based on the free space path loss, transmitting antenna gain and receiving antenna gain, the communication line-of-sight path component is formed.

[0085] Based on the line-of-sight distance and angle of arrival of each interference source to the UAV, the free space path loss is calculated according to the line-of-sight distance; at the same time, the antenna pattern parameters of the UAV's onboard data link terminal and the antenna pattern parameters of the interference source are queried according to the angle of arrival to obtain the receiving antenna gain and transmitting antenna gain; based on the free space path loss, transmitting antenna gain and receiving antenna gain, the interference line-of-sight path component is formed.

[0086] In addition to the communication line-of-sight path component and the interference line-of-sight path component, a multipath component is generated based on a preset multipath channel model.

[0087] For each path component among the communication line-of-sight path component, the interference line-of-sight path component, and the multipath component, the Doppler frequency shift is calculated based on the relative radial velocity of the corresponding link in the spatial geometry parameters, and is used as the Doppler frequency shift of that path component.

[0088] Arranging the communication line-of-sight path components and their multipath components in the time delay domain forms the communication channel impulse response; arranging the interference line-of-sight path components and their multipath components in the time delay domain forms the interference channel impulse response.

[0089] Specifically, for the link between the ground control station and the UAV, calculate the free space path loss. ,in The distance between the ground control station and the UAV is the line-of-sight distance, in meters. is the signal center frequency, in Hertz; c is the speed of light; free space path loss is in decibels.

[0090] Based on the angle of arrival from the ground control station to the UAV, the antenna pattern parameters of the UAV's onboard data link terminal are queried, and the receiving antenna gain in that angle of arrival direction is obtained by table lookup and interpolation calculation. The unit is decibels. The antenna pattern parameters of the ground control station are retrieved, and the transmit antenna gain in that direction of the angle of arrival is calculated through table lookup and interpolation. The unit is decibels.

[0091] The communication line-of-sight path component consists of complex amplitude Delay and Doppler shift Description. (Among them) , Phase of the communication line-of-sight path component ,in The signal wavelength is given. This is based on the relative radial velocity of the link between the ground control station and the UAV. Calculations yielded .

[0092] In addition to the communication line-of-sight path components, a set of multipath components is generated based on a preset multipath channel model. The number of multipath components... The value ranges from 4 to 20, and is preset according to the propagation environment of the simulation scenario, where i is the index of the multipath component (i=1,2,…). For each multipath component, the time delay of that multipath component. exist Add a random offset on top of the base ,Right now ,in It follows a preset time delay spread distribution, typically a uniform distribution within the range of 0 to the maximum time delay spread, with a typical maximum time delay spread value of 500 nanoseconds; the amplitude fading of this multipath component It follows a preset amplitude distribution, typically a Rayleigh distribution; the phase of this multipath component... Uniformly distributed in the range of 0 to 2π; the Doppler frequency shift of this multipath component .

[0093] Arrange the communication line-of-sight path components and all multipath components in the time-delay domain to form the communication channel impulse response. ;in, The propagation delay represents the time delay it takes for a signal to travel from the transmitter to the receiver. Its value ranges from zero to a preset maximum delay value. The maximum delay value is determined by the maximum delay spread parameter of the multipath channel model. The typical maximum delay value is the line-of-sight path delay plus 500 nanoseconds. It is a unit impulse function.

[0094] Then, for each interference source-to-UAV link, an interference channel impulse response is generated using the same method as the communication channel impulse response. For each interference source, the line-of-sight distance from the interference source to the UAV is used... The free-space path loss from the interference source to the UAV is calculated. Based on the angle of arrival from the interference source to the UAV in the spatial geometry parameters, the antenna pattern parameters of the UAV's onboard data link terminal and the interference source are queried to obtain the receiving antenna gain and transmitting antenna gain. Based on the free-space path loss, transmitting antenna gain, and receiving antenna gain, an interference line-of-sight path component is formed. In addition to the interference line-of-sight path component, a set of multipath components is generated according to a preset multipath channel model. For each path component, the Doppler frequency shift is calculated based on the relative radial velocity of the link from the interference source to the UAV in the spatial geometry parameters. The interference line-of-sight path component and all corresponding multipath components are arranged in the time delay domain to form the interference channel impulse response from the interference source to the UAV. , where k is the number of the interference source (k=1,2,…,K), and K is the total number of interference sources.

[0095] The process of generating the impulse response of the communication channel and the impulse response of the interference channel is a method combining the free-space propagation model and the statistical multipath model. The power attenuation of the line-of-sight path component is calculated based on the free-space path loss formula, and the complex amplitude is determined by combining the antenna gain. Its time delay is determined by dividing the line-of-sight distance by the speed of light, and the Doppler frequency shift is calculated by the relative radial velocity. This is the free-space propagation model. The time delay, amplitude, and phase of the multipath components are randomly generated using uniform, Rayleigh, and uniform distributions, respectively. This is the statistical multipath model. The line-of-sight path component and all multipath components are superimposed in the time delay domain to form the complete channel impulse response. This is the combination of the two models.

[0096] In one embodiment of the present invention, step S3, which involves aligning all interference channel impulse responses in the time delay domain and superimposing them with the communication channel impulse response to form an interference channel impulse response matrix, includes the following steps:

[0097] The zero-delay point of all the impulse responses of the aforementioned interference channels is unified to the start time of the signal transmitted by the ground control station, thus completing the time delay domain alignment;

[0098] At each time delay tap position after alignment, the complex value of the communication channel impulse response at that time delay tap is added to the complex value of each interference channel impulse response at that time delay tap to obtain the superimposed complex value of that time delay tap.

[0099] The superimposed complex values ​​of all time delay taps are arranged to form the impulse response matrix of the signal-to-interference channel.

[0100] Specifically, all impulse responses of the interference channels are aligned in the time delay domain. Time delay domain alignment means unifying the zero-delay points of all impulse responses of the interference channels to the same time reference, which is the start time of the signal transmitted by the ground control station.

[0101] Impulse response of each interference channel During generation, the zero-delay point is based on the start time of the signal emitted by the interference source. Due to the different spatial positions between each interference source and the ground control station, there is a time difference between the start time of the signal emitted by each interference source and the start time of the signal emitted by the ground control station. This time difference is determined by dividing the difference between the line-of-sight distance from each interference source to the UAV and the line-of-sight distance from the ground control station to the UAV by the speed of light, c.

[0102] For the k-th interference source, its time delay offset ,in Let k be the line-of-sight distance from the k-th interference source to the drone. This refers to the line-of-sight distance between the ground control station and the drone. When the interference source is farther from the drone than the ground control station, A positive value indicates that the interference signal arrived at the UAV later than the signal transmitted by the ground control station.

[0103] Translate the impulse response of the kth interference channel along the time delay axis The aligned interference channel impulse response is denoted as ,Right now Alignment operations are performed one by one on the impulse responses of all K interference channels, where K is the total number of interference sources.

[0104] After time-delay domain alignment is completed, the aligned impulse responses of all interference channels are superimposed with the impulse responses of the communication channel. The superposition operation is performed independently at each time-delay tap position. A time-delay tap refers to a tap on the time-delay axis with a preset time-delay resolution. Discrete time delay points, time delay resolution The typical value is 1 nanosecond. The delay taps are arranged in sequence l (l=0,1,2,…,L-1), where L is the total number of delay taps, and the propagation delay corresponds to the position of the l-th delay tap. .

[0105] At each time delay tap position The value of the communication channel impulse response at this time delay tap. The value of the impulse response of each aligned interference channel at this time delay tap By performing complex summation, we obtain the value of the impulse response of the signal-to-interference channel at that time delay tap. .in Indicates the propagation delay at the current simulation time t. The communication channel impulse response at the location, Indicates that in t and The impulse response of the signal-to-interference channel at the location.

[0106] The impulse responses of communication channels, interference channels, and signal-to-interference channels are all complex numbers. When adding complex numbers, the real and imaginary parts are calculated separately. The formulas for calculating the real and imaginary parts of the complex number sum are as follows: , , where Re[] represents taking the real part of the complex number, and Im[] represents taking the imaginary part of the complex number.

[0107] Perform a superposition operation on all delay taps, and arrange the superimposed complex values ​​of all delay taps in order of their delay to form the signal-to-interference channel impulse response matrix. The matrix is ​​based on the current simulation time t and the propagation delay. The index is used, and the matrix element is a complex number. Indicates that in t and The communication channel impulse response at the location.

[0108] In one embodiment of the present invention, in step S4, the signal separability function The formula is:

[0109]

[0110] Where τ and v are the independent variables of the signal separability function, representing the time delay and Doppler frequency, respectively. and Let τ and v be the integral variables; The time delay Doppler resolution characteristic function of the transmitted symbol at the integration position The value at that location, The scattering function of the communication channel at the integration position The value at t represents the current simulation time.

[0111] Specifically, the summation response of the interference component is separated from the impulse response matrix of the communication channel. The summation response of the interference component is the remaining part of the impulse response matrix after removing the communication channel impulse response component, at each propagation delay. At that point, the sum of the responses is [value]. Subtraction is a complex number subtraction.

[0112] A time-frequency transformation is performed on the summation response of the interference components. The time-frequency transformation transforms the summation response of the interference components from the propagation delay and time domain to the time-delay Doppler plane, obtaining the energy distribution of the interference components in this plane as a function of propagation delay and Doppler frequency.

[0113] In this embodiment, the time-frequency transformation employs a smoothed pseudo-Wigner-Willi distribution transform. The calculation process involves first applying a time smoothing window to the sum response of the interference components in the time direction, and then calculating the instantaneous autocorrelation function of the windowed signal along the time dimension.

[0114] Instantaneous autocorrelation function The sum of the disturbance components and the response s in time-delayed variables. The autocorrelation results below, i.e. ,in, It is the conjugate of s. The value of is determined by the window length of the time smoothing window, which iterates through all time points within the window. The typical window length for a time smoothing window is 64 sampling points, and the typical window length for a frequency smoothing window is 32 sampling points.

[0115] After the transformation, the energy distribution density of the interference component is obtained. The energy distribution density sometimes has a delay. The three independent variables are: Doppler frequency v, current simulation time t, and time delay. The time delay dimension, expressed in seconds, is represented on the Doppler plane and ranges from zero to a preset maximum time delay value. The Doppler frequency, v, represents the Doppler frequency dimension on the Doppler plane, expressed in Hertz (Hz), and its range is determined by the preset maximum Doppler frequency shift, typically ranging from -500 Hz to +500 Hz. The energy distribution density is a non-negative real number, representing the time delay... The interference energy density at the Doppler frequency v. The value of the energy distribution density is determined by the calculation results of the time-frequency transform; for the typical case where the time delay axis is divided with a time delay resolution of 1 nanosecond and the Doppler frequency axis is divided with a frequency resolution of 1 Hz, This represents the interference energy density value at the current simulation moment, at zero delay and zero Doppler frequency. This represents the interference energy density at the current simulation moment, with a time delay of 100 nanoseconds and a Doppler frequency of 50 Hz.

[0116] Impulse response of communication channels A Fourier transform is performed to transform the communication channel impulse response from the propagation delay dimension to the Doppler frequency dimension, yielding the communication channel scattering function. The Fourier transform is performed along the propagation delay dimension, and the transformation formula is as follows: Where j is the imaginary unit, satisfying =-1. The integration variable is The integral range covers the non-zero support region of the communication channel impulse response. The communication channel scattering function is denoted as... The value of the scattering function of this communication channel is a complex number, and its magnitude represents the time delay. The scattering amplitude at the Doppler frequency v, and its phase represents the corresponding phase rotation.

[0117] Obtain the delay-Doppler resolution characteristic function of the transmitted symbol A transmitted symbol refers to a unit waveform generated by the physical layer of the data link after mapping the bit sequence to be transmitted according to the modulation scheme and pulse shaping filter. The time delay Doppler resolution characteristic function of the transmitted symbol is the square of the absolute value of the ambiguity function of the transmitted symbol. This function is determined by the modulation scheme used by the data link. For a given modulation scheme and pulse shaping filter, this function is fixed and predictable.

[0118] For the various modulation schemes supported by this method The determinations are as follows: For single-carrier modulation methods using rectangular pulse shaping (without roll-off), including quadrature phase shift keying (QPSK) modulation and hexadecimal quadrature amplitude modulation (16QAM), the time delay Doppler resolution characteristic function is: ,when If the value is 0, then the value is 0; otherwise, it is 0. For Orthogonal Frequency Division Multiplexing (OFDM) modulation, the time delay Doppler resolution characteristic function of an OFDM symbol (including the cyclic prefix) is determined by the subcarrier spacing. and effective symbol length Decide: ,in Let be the total number of subcarriers. For direct sequence spread spectrum (DSSS) modulation, its time-delay Doppler resolution characteristic function is: ,in Let autocorrelation function be the spreading code. For chip cycle, This represents the spreading gain (the number of chips corresponding to each symbol). For single-carrier modulation using raised cosine or root-raised cosine pulse shaping filters, the time-domain waveform of the rectangular pulse is replaced with the corresponding impulse response g(t) of the pulse shaping filter for numerical calculation: Where g(t) is the time-domain impulse response of the pulse shaping filter. It is conjugate to it.

[0119] The time delay Doppler resolution characteristic function of the transmitted symbol With communication channel scattering function Perform two-dimensional convolution to obtain the signal separability function. In the signal separability function, and Let τ and v be the integration variables, and let the integration range cover the time-delay Doppler plane. and The non-zero support region; The communication channel impulse response serves as a parameter to identify the channel conditions corresponding to the current signal separability function. The time delay Doppler resolution characteristic function of the transmitted symbol at the integration position The value at that location, For the communication channel scattering function in The value at that location.

[0120] In one embodiment of the present invention, step S4, determining the packet error rate PER(t) of the UAV data link at the current simulation moment, includes the following steps:

[0121]

[0122] in, The energy distribution density, Let M be the detection area of ​​the m-th transmitted symbol on the time-delay Doppler plane, where M is the total number of transmitted symbols.

[0123] Specifically, packet error rate (BER) calculation is performed on all transmitted symbols contained in a coded data packet. A coded data packet is determined by the coding type used by the data link. At the physical layer, this data packet is mapped to M transmitted symbols that are transmitted sequentially, where M is the total number of transmitted symbols in the data packet. The value of M is determined by the frame structure of the data link. For example, for a quadrature phase shift keying (QPSK) modulation link using convolutional coding, a constraint length of 7, and a code rate of half, a 1000-bit data packet corresponds to M = 2000 transmitted symbols.

[0124] For the m-th transmitted symbol, its detection area on the time-delay Doppler plane is: Detection area The symbol period is determined based on the modulation scheme used in the data link. Symbol rate of the selected modulation scheme The reciprocal of, that is For orthogonal frequency division multiplexing modulation, the subcarrier spacing... It is the subcarrier spacing configured by the selected orthogonal frequency division multiplexing modulation scheme. In terms of latency, centered on zero latency and with a width of The interval, centered at the zero Doppler frequency and with a width of The rectangular region enclosed by the intervals. For single-carrier modulation, the detection region... In terms of latency, centered on zero latency and with a width of The interval, centered at the zero Doppler frequency and with a width equal to the receiver's Doppler tolerance, is defined in the Doppler frequency dimension. The rectangular region enclosed by the interval, receiver Doppler tolerance. Values One-tenth, that is .

[0125] For each transmitted symbol, calculate the probability that the symbol is hit by interference energy. The probability of being hit by interference energy is the ratio of the interference energy distribution density to the signal separability function for that transmitted symbol. Integral convolution within the range. Due to the signal separability function... It is a complex number (whose phase represents the phase rotation introduced by channel scattering), while the interference energy distribution density It is a non-negative real number, and when actually participating in the integration operation, it is taken as the magnitude of the signal separability function. This characterizes the leakage weight of interference energy within the signal detection region. That is, the probability of being hit by interference energy is: ,in To Modulo operation. Each of them place Multiply by the coordinates at that point The interference energy leakage weight, as represented, is then integrated over the entire detection area. The integration result is a dimensionless real number, ranging from 0 to 1, representing the probability that the m-th transmitted symbol is hit by interference energy, resulting in a demodulation error.

[0126] Perform integral convolution calculations on each of the M transmitted symbols in the data packet to obtain the probability that each transmitted symbol is hit by the interference energy. The probability that all M transmitted symbols are error-free is... This multiplication is based on the assumption that demodulation errors between transmitted symbols are independent of each other; that is, whether a transmitted symbol is hit by interference energy does not affect the detection results of other transmitted symbols. This assumption holds true in typical data links where transmitted symbols employ independent coding and interleaving.

[0127] The packet error rate PER(t) of the UAV data link at the current simulation moment is the probability that at least one transmitted symbol has an uncorrectable error, which is 1 minus the probability that all transmitted symbols have no errors. PER(t) is the packet error rate of the UAV data link at the current simulation moment, and its value is a real number between 0.0 and 1.0.

[0128] In one embodiment of the present invention, step S5 includes the following steps:

[0129] When the packet error rate exceeds the first packet error rate threshold, the link loss protection behavior is triggered; the link loss protection behavior includes abandoning the current waypoint task, flying along a preset circling path with the current spatial location as the center, and starting the link loss timer;

[0130] If the packet error rate falls below the first packet error rate threshold before the link loss timer reaches the preset maximum tolerance time, the link loss protection behavior is lifted and the execution of subsequent waypoint tasks in the preset waypoint sequence is resumed; if the packet error rate still does not fall below the first packet error rate threshold when the link loss timer reaches the maximum tolerance time, a forced return flight behavior is triggered, which includes flying along a preset return path to a preset return point.

[0131] When the packet error rate exceeds the second packet error rate threshold, the task load adaptive behavior is triggered; the task load adaptive behavior includes reducing the video encoding bitrate to a preset low bitrate level and switching the communication mode to a preset anti-interference communication mode.

[0132] When the packet error rate falls below the second packet error rate threshold and continues for a preset recovery time, the task load adaptive behavior is deactivated and the system returns to normal bit rate and normal communication mode.

[0133] Specifically, the first packet error rate threshold Second packet error rate threshold All of these are derived from drone behavior strategy models. The packet error rate threshold is preset in the condition part of the link loss protection behavior rule and the forced return behavior rule in the corresponding behavior strategy model. The value is determined based on the frame period of the uplink remote control link. Duration of link loss protection behavior rules in the behavior strategy model The uplink remote control link refers to the communication link from the ground control station to the UAV for sending flight control commands; the allowed number of consecutive frame drops within this duration. ,at the same time ;Typically, when For 20 milliseconds, At 2.0 seconds, =100, =0.01, but in actual simulations, it is usually taken as 0.1 to 0.3. The pre-set packet error rate threshold in the conditional part of the task load adaptive behavior rule in the corresponding behavior strategy model. The value is based on the fault tolerance threshold of video encoding in the downlink image transmission link. The downlink image transmission link refers to the communication link from the UAV to the ground control station to send mission payload data, and the typical value is 0.05.

[0134] The packet error rate PER(t) at the current simulation moment is compared with... Compare them. If PER(t) exceeds... If the link loss timer continues to accumulate, it will either start or continue accumulating. The link loss timer is used to accumulate packet loss rates that consistently exceed a certain threshold. The cumulative time. If the packet error rate has not exceeded [a certain threshold] before the current simulation time. If the link loss timer starts counting from zero, then the packet loss timer will start counting from zero. If the packet error rate has exceeded [a certain threshold] before the current simulation time, then [the timer will start counting from zero]. If the link loss timer accumulates to a certain value, an additional time step interval will be added to the existing accumulated time. When the accumulated time of the link loss timer reaches the duration of the link loss protection behavior rule in the behavior strategy model... When the link loss protection behavior is triggered, it is a protective flight procedure automatically executed by the UAV flight control system when it detects a severe deterioration in the uplink remote control link communication quality. The link loss protection behavior includes two operations: abandoning the current waypoint task and flying along a preset circling path. Abandoning the current waypoint task means that the UAV flight control logic terminates the execution of the currently traversed waypoint in the preset waypoint sequence and no longer continues flying along the preset waypoint sequence. Flying along the preset circling path means generating a circular circling path centered on the UAV's current spatial position, according to the circling radius and circling altitude rules in the behavior strategy model. The circling radius is the horizontal radius of the circling path, and the circling altitude is the flight altitude maintained by the UAV during the circling process. The circling path is circular on the horizontal plane, with the center being the UAV's current horizontal position when the link loss protection behavior is triggered. The UAV maintains a constant circling altitude while flying along the circling path. During the execution of the link loss protection behavior, the packet error rate at each subsequent simulation time point continues to be acquired. If the packet error rate falls back to [a certain value] before the link loss timer reaches the duration of the forced return navigation behavior rule in the behavior strategy model. Next, the link loss timer will be reset to zero, the link loss protection behavior will be removed, and the UAV will resume executing the remaining unfinished waypoint tasks in the preset waypoint sequence, flying from the current spatial location to the nearest unfinished waypoint.

[0135] If the accumulated time of the link loss timer reaches the duration of the forced return flight rule in the behavior strategy model, a forced return flight is triggered. When a forced return flight is triggered, the UAV terminates its current hovering flight. The forced return flight involves flying along a preset return path to a preset return point. The preset return point is the three-dimensional coordinate of the return point in the forced return flight rule of the behavior strategy model. The return altitude is the return altitude in the forced return flight rule of the behavior strategy model. The UAV first adjusts from its current spatial position to the return altitude, climbing if the current altitude is lower than the return altitude and descending if the current altitude is higher than the return altitude. After reaching the return altitude, it flies along a straight path between its current spatial position and the return point until it reaches the airspace above the return point.

[0136] The packet error rate PER(t) at the current simulation moment is compared with... Compare them. If PER(t) exceeds... If the error rate exceeds a certain threshold, the task load timer will either start or continue to accumulate. The task load timer is used to accumulate packets with a persistent error rate exceeding a certain threshold. The cumulative time is calculated in the same way as the link loss timer.

[0137] When the accumulated time of the task load timer reaches the duration of the task load adaptive behavior rule in the behavior strategy model, the task load adaptive behavior is triggered. The task load adaptive behavior includes reducing the video encoding bitrate to a preset low bitrate level and switching the communication mode to a preset anti-interference communication mode. The low bitrate level is the target bitrate in the action part of the task load adaptive behavior rule in the behavior strategy model. The anti-interference communication mode is a preset communication mode in the action part of the task load adaptive behavior rule in the behavior strategy model, including reducing the modulation order, increasing the spreading gain, or switching to a backup frequency.

[0138] If the adaptive behavior of the task payload is triggered, the packet error rate in subsequent simulations will drop back to [a certain value]. The recovery timer will then be started. Once the accumulated time of the recovery timer reaches the recovery duration stipulated in the task load adaptive behavior rule of the behavior strategy model, the task load adaptive behavior will be deactivated, the video encoding bitrate will return to the normal bitrate, and the communication mode will return to the normal communication mode. If the packet error rate exceeds the limit again before the recovery timer reaches the recovery duration... If the timer is reset to zero, the task load will continue to be in an adaptive state.

[0139] If no action is triggered at the current simulation moment, the UAV continues to fly along the preset waypoint sequence. The UAV's spatial position is calculated based on the preset waypoint sequence, and its attitude parameters are also calculated based on the attitude parameters in the preset waypoint sequence. If the current simulation moment is in a hovering flight state with link loss protection behavior, the UAV's spatial position is updated along the hovering path. During hovering flight, the UAV maintains a constant hovering radius and hovering altitude, and its spatial position moves uniformly along a circular trajectory on the horizontal plane. The linear velocity is determined by the UAV's cruise speed. The attitude parameters are determined based on the roll angle required for hovering flight, which is calculated from the hovering radius and flight speed through mechanical equilibrium relationships. The pitch and yaw angles are determined based on the tangent direction of the hovering path. If the current simulation moment is in a return-to-home flight state with forced return-to-home behavior, the UAV's spatial position is updated along a straight path from the current spatial position to the return-to-home point, and the flight speed is determined by the UAV's return-to-home speed. The attitude parameters are determined based on the return-to-home flight direction, the pitch angle is determined by the climb or descent rate, the yaw angle points towards the return-to-home point, and the roll angle is zero. If the task payload adaptive behavior is triggered at the current simulation moment, the UAV's operating mode parameters are updated to low bit rate mode or anti-interference communication mode. The operating mode parameters do not affect the UAV's spatial position and attitude, but they do affect the signal waveform characteristics of the downlink data link, thereby affecting the packet error rate calculation results in subsequent simulation moments.

[0140] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A data link simulation method under complex electromagnetic interference environment, characterized in that, Includes the following steps: S1: Configure the initial parameters for the UAV data link simulation. The initial parameters are the UAV's preset waypoint sequence and attitude parameters, the UAV's onboard data link terminal's antenna pattern parameters, the location and antenna pattern parameters of the ground control station, the preset motion paths of at least two interference sources and their antenna pattern parameters and interference patterns, the modulation method used by the data link, the UAV's behavior strategy model, and the preset total simulation duration and time step interval. S2: Start the time-stepping loop of the UAV data link simulation. At each simulation moment, based on the UAV's preset waypoint sequence, the location of the ground control station, and the preset motion path of the interference source, calculate the line-of-sight distance and angle of arrival from the ground control station to the UAV, the line-of-sight distance and angle of arrival from each interference source to the UAV, and the relative radial velocity of each link as spatial geometric parameters. S3: Based on the spatial geometric parameters, the antenna pattern parameters of the UAV airborne data link terminal, the antenna pattern parameters of the ground control station, and the antenna pattern parameters of each interference source, a method combining the free space propagation model and the statistical multipath model is used to generate the communication channel impulse response from the ground control station to the UAV and the interference channel impulse response from each interference source to the UAV. All interference channel impulse responses are aligned in the time delay domain and superimposed with the communication channel impulse response to form an interference channel impulse response matrix. S4: Perform time-frequency transformation on the interference component in the signal-to-interference channel impulse response matrix to obtain the energy distribution density; convolve the time delay Doppler resolution characteristic function of each transmitted symbol in the transmitted symbol sequence generated by the modulation method used in the data link with the communication channel scattering function obtained by Fourier transform of the communication channel impulse response to obtain the signal separability function; perform integral convolution of the energy distribution density and the signal separability function in the time-frequency region of each transmitted symbol, and multiply the integral results of all transmitted symbols together to obtain the packet error rate of the UAV data link at the current simulation time; S5: Compare the packet error rate with a preset first packet error rate threshold and a preset second packet error rate threshold; when the packet error rate exceeds the first packet error rate threshold, trigger the UAV behavior strategy model to simulate link loss protection behavior and forced return behavior; when the packet error rate exceeds the second packet error rate threshold, trigger the UAV behavior strategy model to simulate task load adaptive behavior, and update the UAV's spatial position and attitude parameters according to the simulated behavior.

2. The data link simulation method under complex electromagnetic interference environment according to claim 1, characterized in that, In S1, the interference source's interference patterns include broadband noise suppression interference, frequency sweeping interference, and spoofing interference; wherein, the configuration parameters of broadband noise suppression interference include noise bandwidth and power spectral density; the configuration parameters of frequency sweeping interference include frequency sweep start frequency, frequency sweep end frequency, frequency sweep period, and frequency sweeping mode; and the spoofing interference uses the same modulation method as the data link, and its configuration parameters include synchronization parameters and spoofing data content. The UAV behavior strategy model stores behavior rules in the form of conditional action pairs, where the condition consists of a packet error rate threshold and a duration, and the action consists of flight control commands and mission payload commands.

3. The data link simulation method under complex electromagnetic interference environment according to claim 1, characterized in that, S2 includes the following steps: Based on the UAV's preset waypoint sequence, the spatial position of the UAV at the current simulation time is calculated by interpolation; based on the preset motion paths of the interference sources, the spatial positions of each interference source at the current simulation time are calculated by interpolation. The angle of arrival includes the azimuth and the elevation angle; the azimuth is measured clockwise with true north as the zero-degree reference; the elevation angle is measured with the local horizontal plane as the zero-degree reference, and upward is positive. The relative radial velocity of each link is the projection of the difference between the velocity vector of the UAV and the velocity vector of the other end of the corresponding link onto the line of sight of both. The relative radial velocity is positive when the relative distance decreases and negative when the relative distance increases.

4. The data link simulation method under complex electromagnetic interference environment according to claim 1, characterized in that, In step S3, generating the communication channel impulse response from the ground control station to the UAV and the interference channel impulse response from each interference source to the UAV includes the following steps: Based on the line-of-sight distance and angle of arrival from the ground control station to the UAV, the free space path loss is calculated according to the line-of-sight distance; at the same time, the antenna pattern parameters of the UAV's onboard data link terminal and the antenna pattern parameters of the ground control station are queried according to the angle of arrival to obtain the receiving antenna gain and transmitting antenna gain; based on the free space path loss, transmitting antenna gain and receiving antenna gain, the communication line-of-sight path component is formed. Based on the line-of-sight distance and angle of arrival of each interference source to the UAV, the free space path loss is calculated according to the line-of-sight distance; at the same time, the antenna pattern parameters of the UAV's onboard data link terminal and the antenna pattern parameters of the interference source are queried according to the angle of arrival to obtain the receiving antenna gain and transmitting antenna gain; based on the free space path loss, transmitting antenna gain and receiving antenna gain, the interference line-of-sight path component is formed. In addition to the communication line-of-sight path component and the interference line-of-sight path component, a multipath component is generated based on a preset multipath channel model. For each path component among the communication line-of-sight path component, the interference line-of-sight path component, and the multipath component, the Doppler frequency shift is calculated based on the relative radial velocity of the corresponding link in the spatial geometry parameters, and is used as the Doppler frequency shift of that path component. Arranging the communication line-of-sight path components and their multipath components in the time delay domain forms the communication channel impulse response; arranging the interference line-of-sight path components and their multipath components in the time delay domain forms the interference channel impulse response.

5. The data link simulation method under complex electromagnetic interference environment according to claim 4, characterized in that, In step S3, the step of aligning all interference channel impulse responses in the time delay domain and superimposing them with the communication channel impulse responses to form an interference channel impulse response matrix includes the following steps: The zero-delay point of all the impulse responses of the aforementioned interference channels is unified to the start time of the signal transmitted by the ground control station, thus completing the time delay domain alignment; At each time delay tap position after alignment, the complex value of the communication channel impulse response at that time delay tap is added to the complex value of each interference channel impulse response at that time delay tap to obtain the superimposed complex value of that time delay tap. The superimposed complex values ​​of all time delay taps are arranged to form the impulse response matrix of the signal-to-interference channel.

6. The data link simulation method under complex electromagnetic interference environment according to claim 1, characterized in that, In S4, the signal separability function The formula is: Where τ and v are the independent variables of the signal separability function, representing the time delay and Doppler frequency, respectively. and Let τ and v be the integral variables; The time delay Doppler resolution characteristic function of the transmitted symbol at the integration position The value at that location, The scattering function of the communication channel at the integration position The value at t represents the current simulation time.

7. The data link simulation method under complex electromagnetic interference environment according to claim 6, characterized in that, In step S4, the packet error rate PER(t) of the UAV data link at the current simulation moment includes the following steps: in, The energy distribution density, Let M be the detection region of the m-th transmitted symbol on the time-delay Doppler plane, where M is the total number of transmitted symbols.

8. The data link simulation method under complex electromagnetic interference environment according to claim 1, characterized in that, S5 includes the following steps: When the packet error rate exceeds the first packet error rate threshold, the link loss protection behavior is triggered; the link loss protection behavior includes abandoning the current waypoint task, flying along a preset circling path with the current spatial location as the center, and starting the link loss timer; If the packet error rate falls below the first packet error rate threshold before the link loss timer reaches the preset maximum tolerance time, the link loss protection behavior is lifted and the execution of subsequent waypoint tasks in the preset waypoint sequence is resumed; if the packet error rate still does not fall below the first packet error rate threshold when the link loss timer reaches the maximum tolerance time, a forced return flight behavior is triggered, which includes flying along a preset return path to a preset return point. When the packet error rate exceeds the second packet error rate threshold, the task load adaptive behavior is triggered; the task load adaptive behavior includes reducing the video encoding bitrate to a preset low bitrate level and switching the communication mode to a preset anti-interference communication mode. When the packet error rate falls below the second packet error rate threshold and continues for a preset recovery time, the task load adaptive behavior is deactivated and the system returns to normal bit rate and normal communication mode.

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