CN114584192A - Anti-jitter robust beamforming optimization method for millimeter wave unmanned aerial vehicle communication system - Google Patents
Anti-jitter robust beamforming optimization method for millimeter wave unmanned aerial vehicle communication system Download PDFInfo
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Abstract
The invention discloses an anti-jitter robust beamforming optimization method for a millimeter wave unmanned aerial vehicle communication system, which comprises the steps that the millimeter wave communication system of an unmanned aerial vehicle receives feedback information of a GPS positioning channel and a user return channel in real time, obtains an unmanned aerial vehicle transmitting beamforming vector, and obtains pitch angle and azimuth angle information between the unmanned aerial vehicle and a ground user, so that an upper limit value of a jitter error of the unmanned aerial vehicle is obtained; a jitter error model is introduced, the downlink transmission capacity sum of a plurality of ground users is calculated according to the unmanned aerial vehicle transmitting beam forming vector and the noise power, and the transmitting beam forming optimization problem is determined; and (3) carrying out deterministic transformation on the optimization problem of the jitter error model based on a convex hull theory, and solving by using a continuous convex approximation method to obtain beam forming vector parameters. The unmanned aerial vehicle millimeter wave communication system with the optimal anti-jitter robust wave performance is determined based on the unmanned aerial vehicle millimeter wave transmitting beam forming optimization problem model with known vector parameters, and the anti-jitter capability of the unmanned aerial vehicle millimeter wave communication system is improved.
Description
Technical Field
The invention relates to the technical field of millimeter wave communication of an unmanned aerial vehicle, in particular to an anti-jitter robust beamforming optimization method of a millimeter wave unmanned aerial vehicle communication system.
Background
In recent years, the implementation of unmanned aerial vehicle data communication by using millimeter wave technology has become a research hotspot in academia and industry. On the one hand, the characteristic of millimeter wave signal short wavelength high frequency provides a feasible scheme for solving the problems of unmanned aerial vehicle load limitation and frequency spectrum resource shortage, and is favorable for improving the information transmission rate. On the other hand, the unmanned aerial vehicle can be flexibly arranged in the air, and the high flying position enables a line-of-sight path to exist in the communication process, so that the coverage range of millimeter wave communication can be greatly expanded, the network connectivity can be improved, and the unmanned aerial vehicle becomes an excellent carrying platform of the millimeter wave communication technology. However, unlike the ground cellular network with a stable infrastructure, the drone is susceptible to airflow and self-vibration due to the limitations of atmospheric turbulence and flight control capability, and random jitter such as yaw jitter in the horizontal direction or pitch jitter in the vertical direction is generated, so that the beam pointing direction is angularly deviated, thereby causing inefficient and unstable information transmission of the air-ground transmission link.
The millimeter wave is more susceptible to the influence of angle errors caused by unmanned aerial vehicle jitter due to the characteristic of directional narrow beams, and the performance of a communication system can generate more adverse influence due to beam angle deviation. Therefore, the negative impact of the jitter characteristic of the drone in the millimeter wave drone communication system is more negligible.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides an anti-jitter robust beamforming optimization method for a millimeter wave unmanned aerial vehicle communication system; by optimizing the millimeter wave transmitting beam forming vector of the unmanned aerial vehicle, the sum of downlink transmission capacity of multiple users under the worst condition is maximized, so that the millimeter wave communication system of the unmanned aerial vehicle has stronger robustness to the shaking of the unmanned aerial vehicle.
The technical scheme is as follows: the invention provides a jitter-resistant robust beamforming optimization method for a millimeter wave unmanned aerial vehicle communication system, which comprises the following steps:
receiving feedback information of GPS positioning and user return channels in real time through an unmanned aerial vehicle millimeter wave communication system, analyzing millimeter wave transmitting beams transmitted to a plurality of ground users by a multi-antenna unmanned aerial vehicle base station in the feedback information, obtaining unmanned aerial vehicle transmitting beam forming vectors according to the millimeter wave transmitting beams, and extracting position data of the unmanned aerial vehicle and the ground users from the feedback information;
calculating based on the position data of the unmanned aerial vehicle and the ground user, determining pitch angle and azimuth angle information between the unmanned aerial vehicle and the ground user, calculating all pitch angle and azimuth angle information between the unmanned aerial vehicle and the ground user in the whole flying process of the unmanned aerial vehicle, and obtaining an upper limit value of a jitter error in the flying process of the unmanned aerial vehicle;
inputting the upper limit value of the jitter error into a jitter error model of a millimeter wave air-ground channel of the unmanned aerial vehicle, calculating the sum of downlink transmission capacities of a plurality of ground users according to the transmitted beam forming vector of the unmanned aerial vehicle and the noise power from the unmanned aerial vehicle to the ground users, and determining the optimization problem of the millimeter wave transmitted beam forming of the unmanned aerial vehicle; the unmanned aerial vehicle millimeter wave air-ground channel jitter error model is constructed according to the communication characteristics of the unmanned aerial vehicle millimeter wave air-ground channel;
carrying out deterministic transformation on the jitter error model on the unmanned aerial vehicle millimeter wave emission beam forming optimization problem based on a convex hull theory to obtain a deterministic problem;
solving the certainty problem by using a continuous convex approximation method to obtain vector parameters of the unmanned aerial vehicle millimeter wave transmission beam forming optimization problem;
and determining the unmanned aerial vehicle millimeter wave communication system with the optimal anti-jitter robust wave performance based on the unmanned aerial vehicle millimeter wave transmitting beam forming optimization problem model with known vector parameters.
In a further embodiment, the pitch angle and azimuth angle information calculation formulas between the drone and the ground user are respectively:
in the formula, qu=(xu,yu)TAnd q isk(xk,yk)THorizontal coordinates, x, representing unmanned aerial vehicle and ground user, respectivelyτAnd yττ ∈ { u, k } denotes the coordinates of the horizontal x-direction and y-direction of the drone (ground user), respectively,h is the flying height of the unmanned aerial vehicle, and T is the transposed symbol of the vector.
In a further embodiment, the formula for calculating the millimeter wave air-ground channel jitter error model of the drone is as follows:
in the formula, hkIs a vector of the channel to be transmitted,is a constant, c is the speed of light, fcIs the carrier center frequency and is the carrier center frequency, the distance between the drone and the ground user,is an antenna array vector, θkAndpitch and azimuth angles between the drone and the ground user,andrespectively, an estimated value of a pitch angle and an estimated value of an azimuth angle between the unmanned aerial vehicle and a ground user, delta thetakAndrespectively a pitching angle shaking error and an azimuth angle shaking error caused by the shaking of the unmanned aerial vehicle,andrespectively an upper limit value of a pitching angle jitter error and an upper limit value of an azimuth angle jitter error;
wherein d is the distance between adjacent antenna elements of the uniform planar array, λ is the carrier wavelength, and m is not less than 1x≤Mx,1≤my≤My,MxAnd MyThe number of the row antennas and the number of the column antennas of the uniform planar array are respectively.
In a further embodiment, the expression for determining the millimeter wave transmission beamforming optimization problem of the unmanned aerial vehicle is as follows:
in the formula (I), the compound is shown in the specification,is the upper limit value of the transmitting power of the unmanned aerial vehicle,for multi-user downlink transmission of capacity sum, wkTransmitting a beamforming vector for the drone;
wherein the downlink transmission capacity of multiple users isThe calculation formula of (2) is as follows:
in the formula, HkFor a channel matrix, ΛkIs HkIs determined by the uncertainty set of (a),representing the noise power of the drone to ground user communication link,for the kth beamforming vector wkThe conjugate of (a) the transposed vector (v),for the ith ≠ k beamforming vectors wiThe conjugate transpose vector of (1);
wherein HkUncertain set Λ ofkThe calculation expression of (a) is:
in the formula, hkFor the purpose of the channel vector,is hkThe conjugate of (2) is transposed the vector.
In a further embodiment, the method of obtaining a deterministic problem is:
according to the convex hull theory, the uncertain channel matrix containing the jitter error can be expressed as a deterministic form of the weighted sum of finite or infinite discrete samples in an uncertain set, and the expression of the uncertain channel matrix is as follows:
in the formula, LkThe number of the total samples is the number of the samples,is the weighting coefficient for the jth sample,determining the jth sample according to the discretized angle information; by usingSubstitute HkThe problem (P1) is approximately represented as a deterministic problem (P2) and the calculation formula is:
s.t. (4b) (8b)
in a further embodiment, the deterministic problem is solved using a continuous convex approximation method as follows:
the non-convex problem is converted into a convex optimization problem by using a continuous convex approximation method,
the conversion calculation formula is:
maxwk,a,fk,pka (9a)
(4b) (9e)
in the formula (I), the compound is shown in the specification, representing the real part, a, f, of Ak,pkRepresents the auxiliary variables introduced in the optimization problem,is wk,fk,pkIs possible.
In a further embodiment, the method for obtaining the vector parameters of the unmanned aerial vehicle millimeter wave transmission beam forming optimization problem includes:
initializing a beam forming vector, and presetting an auxiliary variable and iteration precision in an unmanned aerial vehicle air-ground channel jitter error model;
substituting the beamforming vector and the auxiliary variable into a formula of a continuous convex approximation method for comparison, and selecting and outputting the beamforming vector and the auxiliary variable which meet the value range of the formula of the continuous convex approximation method;
and judging whether the difference between the iteration values of the two previous and next multi-user downlink transmission capacity sums is smaller than the iteration precision or not according to the multi-user downlink transmission capacity sums, outputting a beam forming vector if the difference is smaller than the iteration precision, and circularly comparing whether the beam forming vector and the auxiliary variable meet the value range of a convex approximation method or not if the difference is larger than the iteration precision.
Has the advantages that: compared with the prior art, the invention has the following advantages:
the advantages of the unmanned aerial vehicle communication system and the millimeter wave technology are complementary by combining the unmanned aerial vehicle communication system and the millimeter wave technology, and meanwhile, a deterministic conversion method of a jitter error model based on a convex hull theory is provided for the jitter characteristic of unmanned aerial vehicle jitter, so that the problem of uncertain angle errors caused by unmanned aerial vehicle jitter is effectively solved, and the jitter resistance of the unmanned aerial vehicle millimeter wave communication system is improved.
Aiming at the problem of multi-user downlink transmission capacity and maximization of an unmanned aerial vehicle millimeter wave system under the worst condition, an iterative solution algorithm based on continuous convex approximation is provided, a non-convex problem is converted into a convex form, the optimal suboptimal solution of an original problem is obtained through optimization of a beam forming vector and convergence under finite iterations, and the service quality requirement of unmanned aerial vehicle millimeter wave downlink data transmission in a task window is guaranteed.
Drawings
Fig. 1 is a system model diagram of an anti-jitter robust beamforming optimization method of a millimeter wave unmanned aerial vehicle communication system according to the present invention;
fig. 2 is a schematic diagram of the unmanned aerial vehicle dithering of the anti-dithering robust beamforming optimization method for the millimeter wave unmanned aerial vehicle communication system according to the present invention;
FIG. 3 is a flowchart of an algorithm of the anti-jitter robust beamforming optimization method of the millimeter wave unmanned aerial vehicle communication system according to the present invention;
FIG. 4 is a beam diagram of a beamforming vector w _1 under the robust beamforming scheme for anti-jitter proposed in the present invention;
fig. 5 is a graph of the multi-user downlink transmission capacity and the variation trend with the maximum value of jitter error under the anti-jitter robust beamforming scheme and the non-robust beamforming scheme.
Detailed Description
In order to more fully understand the technical content of the present invention, the technical solution of the present invention will be further described and illustrated with reference to the following specific embodiments, but not limited thereto.
The invention provides a jitter-resistant robust beamforming optimization method for a millimeter wave unmanned aerial vehicle communication system, which comprises the following steps:
receiving feedback information of GPS positioning and user return channels in real time through an unmanned aerial vehicle millimeter wave communication system, analyzing millimeter wave transmitting beams transmitted to a plurality of ground users by a multi-antenna unmanned aerial vehicle base station in the feedback information, obtaining unmanned aerial vehicle transmitting beam forming vectors according to the millimeter wave transmitting beams, and extracting position data of the unmanned aerial vehicle and the ground users from the feedback information;
calculating based on the position data of the unmanned aerial vehicle and the ground user, determining pitch angle and azimuth angle information between the unmanned aerial vehicle and the ground user, calculating all pitch angle and azimuth angle information between the unmanned aerial vehicle and the ground user in the whole flying process of the unmanned aerial vehicle, and obtaining an upper limit value of a jitter error in the flying process of the unmanned aerial vehicle;
inputting the upper limit value of the jitter error into a jitter error model of a millimeter wave air-ground channel of the unmanned aerial vehicle, calculating the sum of downlink transmission capacities of a plurality of ground users according to the transmitted beam forming vector of the unmanned aerial vehicle and the noise power from the unmanned aerial vehicle to the ground users, and determining the optimization problem of the millimeter wave transmitted beam forming of the unmanned aerial vehicle; the unmanned aerial vehicle millimeter wave air-ground channel jitter error model is constructed according to the communication characteristics of the unmanned aerial vehicle millimeter wave air-ground channel;
carrying out deterministic conversion on the jitter error model on the problem of optimization of millimeter wave transmitting beam forming of the unmanned aerial vehicle based on a convex hull theory to obtain a deterministic problem;
solving the certainty problem by using a continuous convex approximation method to obtain vector parameters of the unmanned aerial vehicle millimeter wave transmission beam forming optimization problem;
and determining the unmanned aerial vehicle millimeter wave communication system with the optimal anti-jitter robust wave performance based on the unmanned aerial vehicle millimeter wave transmitting beam forming optimization problem model with known vector parameters.
In a further embodiment, the pitch angle and azimuth angle information between the drone and the ground user are calculated by the following formulas:
in the formula, qu=(xu,yu)TAnd q isk(xk,yk)THorizontal coordinates, x, representing unmanned aerial vehicle and ground user, respectivelyτAnd yττ ∈ { u, k } denotes the coordinates of the horizontal x-direction and y-direction of the drone (ground user), respectively,h is the flying height of the unmanned aerial vehicle, and T is the transposed symbol of the vector.
In a further embodiment, the formula for calculating the millimeter wave air-ground channel jitter error model of the drone is as follows:
in the formula, hkFor the purpose of the channel vector,is a constant, c is the speed of light, fcIs the carrier center frequency and is the carrier center frequency, the distance between the drone and the ground user,is an antenna array vector, θkAndpitch and azimuth angles between the drone and the ground user,andrespectively between unmanned aerial vehicle and ground userEstimated values of pitch and azimuth angles, Delta thetakAndrespectively a pitching angle shaking error and an azimuth angle shaking error caused by the shaking of the unmanned aerial vehicle,andrespectively an upper limit value of a pitching angle jitter error and an upper limit value of an azimuth angle jitter error;
wherein d is the distance between adjacent antenna elements of the uniform planar array, λ is the carrier wavelength, and m is not less than 1x≤Mx,1≤my≤My,MxAnd MyThe number of the row antennas and the number of the column antennas of the uniform planar array are respectively.
In a further embodiment, an optimization algorithm expression for establishing the unmanned aerial vehicle millimeter wave transmission beam forming optimization problem is as follows:
in the formula (I), the compound is shown in the specification,is the upper limit value of the transmitting power of the unmanned aerial vehicle,for multi-user downlink transmission of capacity sum, wkTransmitting a beamforming vector for the drone;
in the formula, HkFor a channel matrix, ΛkIs HkIs determined by the uncertainty set of (a),representing the noise power of the drone to ground user communication link,for the kth beamforming vector wkThe conjugate of the transposed vector of (a),for the ith ≠ k beamforming vectors wiThe conjugate transpose vector of (1);
wherein HkUncertain set Λ ofkThe calculation expression of (a) is:
in the formula, hkFor the purpose of the channel vector,is hkThe conjugate of (2) transposes the vector.
In a further embodiment, the optimization algorithm combines the convex hull theory to perform deterministic transformation on the jitter error model, and the method for obtaining the deterministic problem comprises the following steps:
according to the convex hull theory, the uncertain channel matrix containing the jitter error can be expressed as a deterministic form of the weighted sum of finite or infinite discrete samples in an uncertain set, and the expression of the uncertain channel matrix is as follows:
in the formula, LkTo be the total number of samples,is the weighting coefficient for the jth sample,determining the jth sample according to the discretized angle information; by usingSubstitute HkThe problem (P1) is approximately represented as a deterministic problem (P2) with the calculation formula:
s.t. (4b) (8b)
in a further embodiment, the deterministic problem is solved using a continuous convex approximation method as follows:
the non-convex problem is converted into a convex optimization problem by using a continuous convex approximation method,
the conversion calculation formula is:
(4b) (9e)
in the formula (I), the compound is shown in the specification, representing the real part, a, f, of Ak,pkRepresents the auxiliary variables introduced in the optimization problem,is wk,fk,pkIs possible.
In a further embodiment, the method for outputting the millimeter wave drone anti-jitter robust beamforming vector parameters comprises:
initializing a beam forming vector, and presetting an auxiliary variable and iteration precision in an unmanned aerial vehicle air-ground channel jitter error model;
substituting the beamforming vector and the auxiliary variable into a formula of a continuous convex approximation method for comparison, and selecting and outputting the beamforming vector and the auxiliary variable which meet the value range of the formula of the continuous convex approximation method;
and judging whether the difference of the iteration values of the multi-user downlink transmission capacity sums in the previous and subsequent times is smaller than the iteration precision or not according to the multi-user downlink transmission capacity sum, outputting a beam forming vector if the difference is smaller than the iteration precision, and circularly comparing whether the beam forming vector and the auxiliary variable meet the value range of a convex approximation method or not if the difference is larger than the iteration precision.
The output vector parameters are in a multi-antenna millimeter wave unmanned aerial vehicle system, and the signal weighted value of each array element in the antenna array is adjusted in a self-adaptive manner according to the beam forming technology; and then the transmission beam direction of the millimeter wave unmanned aerial vehicle is adjusted, so that the main lobe direction of the beam is aligned to the target user, and other users are in the null space of the target user, the interference among users is reduced, and the anti-jitter capability of the millimeter wave communication system of the unmanned aerial vehicle is effectively improved.
The invention is further illustrated with reference to example 1:
as shown in fig. 1, the system model of the present invention considers an unmanned plane millimeter wave downlink communication system, which includes an unmanned plane base station and K ground users. The unmanned aerial vehicle adopts a uniform plane antenna array, and is equipped with M-MxMyThe ground user is equipped with a single antenna.
Assuming that an air-ground node transmission channel is a line-of-sight transmission channel, considering the communication characteristics of a millimeter wave air-ground channel of the unmanned aerial vehicle, establishing an unmanned aerial vehicle air-ground channel model based on angle jitter errors as follows: +
Whereinc is the speed of light, fcIs the carrier center frequency, qu=(xu,yu)TAnd q isk=(xk,yk)THorizontal coordinates representing the drone and the ground user respectively,h is the flying height of the unmanned aerial vehicle, akAs an antenna array vector, it can be expressed as:
wherein d is the distance between adjacent antenna elements of the uniform planar array, λ is the carrier wavelength, 1 ≦ mx≤Mx,1≤my≤My,M=Mx×MyIs the total antenna number of the uniform planar array. ThetakAndrepresenting the pitch and azimuth angles between the drone and the ground user, respectively. The angle information between the drone and the ground user may be expressed as:
different from ground cellular network, because do not have fixed ground support facility, unmanned aerial vehicle's stability can't be guaranteed, lead to its vertical direction and horizontal direction to appear the angle shake error. The unmanned aerial vehicle shaking model is shown in fig. 2, the left figure is a schematic diagram of millimeter wave emission beams of an unmanned aerial vehicle with a vertical section, and the right figure is a schematic diagram of millimeter wave emission beams of an unmanned aerial vehicle with a horizontal section. Considering the jitter characteristics of the unmanned aerial vehicle, an angle jitter error model based on the unmanned aerial vehicle jitter can be established as follows:
whereinAndrespectively, an estimated value of a pitch angle and an estimated value of an azimuth angle between the unmanned aerial vehicle and a ground user, delta thetakAndrespective pitch angle jitter error and azimuth caused by unmanned aerial vehicle jitterThe error in the angular jitter is a function of,andthe maximum value of the pitching angle jitter error and the maximum value of the azimuth angle jitter error are respectively. The uncertainty angle jitter error model is used to characterize the uncertainty channel matrix, which can be expressed as:
Assuming that the drone transmit signal can be expressed as:
wherein s iskThe information sent for the drone is sent by the drone, representing unmanned aerial vehicle millimeter wave transmit beamforming vectors. Thus, the signal received by the kth terrestrial user can be specifically expressed as:
whereinIs additive white gaussian noise for the unmanned aerial vehicle to ground user communication link. The signal-to-interference-and-noise ratio of the k-th ground user from the drone obtained by the above equation can be expressed as follows:
according to equations (1-8), considering the worst case, the sum of the multi-user downlink transmission capacities can be expressed as:
further constructing an optimization problem of millimeter wave transmission beam forming of the unmanned aerial vehicle containing angle jitter errors, maximizing the downlink transmission capacity of multiple users, and specifically modeling as follows:
Next, the optimization problem (1-10) is processed and converted into a form that can be solved. Firstly, a deterministic conversion method of a jitter error model based on a convex hull theory is provided. According to convex hull theory, the uncertain channel matrix containing the jitter error can be expressed in a deterministic fashion as a weighted sum of a finite or infinite number of discrete samples in an uncertain set, i.e.
Wherein L iskTo be the total number of samples,is the weighting coefficient for the jth sample,is the jth sample.ByIt is determined that,discretizing by the following formula:
thus, adoptSubstitute HkThe problem (P1) can be equivalently represented as a deterministic problem (P2):
s.t. (10b) (1-13b)
the objective function in the optimization problem (1-13) is non-convex, by introducing auxiliary variables a, fk,pkIts equivalence is converted into the following form:
(10b) (1-14e)
since the constraints (1-14c) are non-convex and difficult to solve, we apply the continuous convex approximation method to convert it into a convex form by first-order Taylor expansion. Given aIs provided with
Whereby (1-14c) can be converted into:
to this end, the original non-convex optimization problem can be equivalently transformed into the following form:
s.t. (10b),(14b),(14d),(16) (1-17b)
finally, an anti-jitter robust beamforming algorithm of the millimeter wave communication system of the unmanned aerial vehicle is designed, and an unmanned aerial vehicle transmitting beamforming vector which enables downlink transmission capacity of multiple users to be maximized is obtained through continuous convex approximation iterative solution, wherein the specific algorithm is shown in fig. 3, and the process is as follows:
step 1: initializing beamforming vectorsAuxiliary variableAndlet n equal to 0 and epsilon equal to 10-4。
Step 2: in the beamforming vectorAnd auxiliary variablesBased on the formula (1-17) to calculate the beam forming vectorAnd auxiliary variables
And step 3: and judging whether the objective function value of the formula (1-9) converges on epsilon or not, namely whether the difference between the iteration values of the previous iteration and the next iteration is smaller than the iteration precision or not. If yes, continue step 4, otherwise, go to step 2 after making n ═ n + 1.
The output vector parameters are in a multi-antenna millimeter wave unmanned aerial vehicle system, and the signal weighted value of each array element in the antenna array is adjusted in a self-adaptive manner according to the beam forming technology; further adjusting the transmission beam direction of the millimeter wave unmanned aerial vehicle to ensure thatThe main lobe direction of the obtained wave beam is aligned to the target user, and meanwhile, other users are in the null space of the target user, so that the interference among the users is reduced. Further described with reference to FIG. 4; FIG. 4 shows a beamforming vector w under the robust beamforming scheme for anti-jitter proposed in the present invention1The beam pattern of (a). The rectangular area in the figure is an angle jitter error range caused by unmanned aerial vehicle jitter. As can be seen from the figure, w1The main lobe of (1) points to the direction of the user 1, and the normalized transmission power is higher than-0.1 dB. At the same time, w1The null space aligns to the uncertain areas where the users 2 and 3 are located, and the normalized transmitting power of the null space is lower than-50 dB, which means that the anti-jitter robust beamforming scheme provided by the invention can effectively improve the anti-jitter capability of the millimeter wave communication system of the unmanned aerial vehicle, and simultaneously reduces the interference between the users.
Fig. 5 is a graph of a multi-user downlink transmission and a capacity variation trend with a maximum value of an angle error under an anti-jitter robust beamforming scheme and a non-robust beamforming scheme. As can be seen from the figure, as the maximum value of the pitch angle jitter error and the maximum value of the azimuth angle jitter error increase, the downlink transmission and capacity of the robust and non-robust schemes are continuously reduced. However, the descending rate of the robust scheme is obviously slower than that of the non-robust scheme, because the robust scheme considers the angle jitter error caused by the unmanned aerial vehicle jitter during optimization and has robustness on the jitter error, and the non-robust scheme does not consider the influence of the unmanned aerial vehicle jitter, so that the beam pointing direction is deviated, and the performance of the millimeter wave system of the unmanned aerial vehicle is rapidly reduced.
Therefore, the advantages of the unmanned aerial vehicle communication system and the millimeter wave technology are complemented by combining the two technologies, and meanwhile, a deterministic conversion method of a jitter error model based on a convex hull theory is provided for the jitter characteristic of the unmanned aerial vehicle jitter, so that the problem of uncertain angle errors caused by the unmanned aerial vehicle jitter is effectively solved, and the jitter resistance of the unmanned aerial vehicle millimeter wave communication system is improved.
Aiming at the problem of multi-user downlink transmission capacity and maximization of an unmanned aerial vehicle millimeter wave system under the worst condition, an iterative solution algorithm based on continuous convex approximation is provided, a non-convex problem is converted into a convex form, the optimal suboptimal solution of an original problem is obtained through optimization of a beam forming vector and convergence under finite iterations, and the service quality requirement of unmanned aerial vehicle millimeter wave downlink data transmission in a task window is guaranteed.
Embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
Embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (7)
1. A jitter-resistant robust beamforming optimization method for a millimeter wave unmanned aerial vehicle communication system is characterized by comprising the following steps:
receiving feedback information of GPS positioning and user return channels in real time through an unmanned aerial vehicle millimeter wave communication system, analyzing millimeter wave transmitting beams transmitted to a plurality of ground users by a multi-antenna unmanned aerial vehicle base station in the feedback information, obtaining unmanned aerial vehicle transmitting beam forming vectors according to the millimeter wave transmitting beams, and extracting position data of the unmanned aerial vehicle and the ground users from the feedback information;
calculating based on the position data of the unmanned aerial vehicle and the ground user, determining pitch angle and azimuth angle information between the unmanned aerial vehicle and the ground user, calculating all pitch angle and azimuth angle information between the unmanned aerial vehicle and the ground user in the whole flying process of the unmanned aerial vehicle, and obtaining an upper limit value of a jitter error in the flying process of the unmanned aerial vehicle;
inputting the upper limit value of the jitter error into a jitter error model of a millimeter wave air-ground channel of the unmanned aerial vehicle, calculating the sum of downlink transmission capacities of a plurality of ground users according to the transmitted beam forming vector of the unmanned aerial vehicle and the noise power from the unmanned aerial vehicle to the ground users, and determining the optimization problem of the millimeter wave transmitted beam forming of the unmanned aerial vehicle; the unmanned aerial vehicle millimeter wave air-ground channel jitter error model is constructed according to the communication characteristics of the unmanned aerial vehicle millimeter wave air-ground channel;
carrying out deterministic conversion on the jitter error model on the problem of optimization of millimeter wave transmitting beam forming of the unmanned aerial vehicle based on a convex hull theory to obtain a deterministic problem;
solving the certainty problem by using a continuous convex approximation method to obtain vector parameters of the unmanned aerial vehicle millimeter wave transmission beam forming optimization problem;
and determining the unmanned aerial vehicle millimeter wave communication system with the optimal anti-jitter robust wave performance based on the unmanned aerial vehicle millimeter wave transmitting beam forming optimization problem model with known vector parameters.
2. The method of claim 1, wherein the calculation formulas for pitch angle and azimuth angle information between the drone and the ground user are respectively:
in the formula, qu=(xu,yu)TAnd q isk(xk,yk)THorizontal coordinates, x, representing unmanned aerial vehicle and ground user, respectivelyτAnd yττ ∈ { u, k } denotes the coordinates of the horizontal x-direction and y-direction of the drone (ground user), respectively,h is the flying height of the unmanned aerial vehicle, and T is the transposed symbol of the vector.
3. The method of claim 1, wherein the formula for calculating the millimeter wave space-ground channel jitter error model of the drone is as follows:
in the formula, hkFor the purpose of the channel vector,is a constant, c is the speed of light, fcIs the carrier center frequency and is the carrier center frequency, the distance between the drone and the ground user,is an antenna array vector, θkAndpitch and azimuth angles between the drone and the ground user,andrespectively, an estimated value of a pitch angle and an estimated value of an azimuth angle between the unmanned aerial vehicle and a ground user, delta thetakAndrespectively a pitching angle shaking error and an azimuth angle shaking error caused by the shaking of the unmanned aerial vehicle,andrespectively an upper limit value of a pitching angle jitter error and an upper limit value of an azimuth angle jitter error;
wherein d is the distance between adjacent antenna elements of the uniform planar array, λ is the carrier wavelength, and m is greater than or equal to 1x≤Mx,1≤my≤My,MxAnd MyThe number of the row antennas and the number of the column antennas of the uniform planar array are respectively.
4. The method of claim 1, wherein the determining an expression of the drone millimeter wave transmit beamforming optimization problem is:
in the formula (I), the compound is shown in the specification,is the upper limit value of the transmitting power of the unmanned aerial vehicle,for multiple users downlink transmission capacity sum, wkTransmitting a beamforming vector for the drone;
wherein the downlink transmission capacity of multiple users isThe calculation formula of (2) is as follows:
in the formula, HkFor a channel matrix, ΛkIs HkIs determined by the uncertainty set of (a),representing the noise power of the drone to ground user communication link,for the kth beamforming vector wkThe conjugate of (a) the transposed vector (v),for the i ≠ k beamforming vectors wiThe conjugate transpose vector of (1);
wherein HkUncertain set Λ ofkThe calculation expression of (a) is:
5. The method for optimizing anti-jitter robust beamforming for a millimeter wave drone communication system of claim 1, wherein the method for obtaining the deterministic problem is:
according to the convex hull theory, the uncertain channel matrix containing the jitter error is expressed as a deterministic form of the weighted sum of finite or infinite discrete samples in an uncertain set, and the expression of the uncertain channel matrix is as follows:
in the formula, LkTo be the total number of samples,is the weighting coefficient for the jth sample,determining the jth sample according to the discretized angle information; by usingSubstitute HkThe problem (P1) is approximately represented as a deterministic problem (P2) and the calculation formula is:
s.t. (4b) (8b)。
6. the method for optimizing anti-jitter robust beamforming for a millimeter wave drone communication system of claim 1, wherein the method for solving the deterministic problem using the continuous convex approximation method is:
the non-convex problem is converted into a convex optimization problem by using a continuous convex approximation method,
the conversion calculation formula is:
(4b) (9e)
7. The method of claim 1, wherein the method for obtaining vector parameters of the unmanned aerial vehicle millimeter wave transmission beamforming optimization problem comprises:
initializing a beam forming vector, and presetting an auxiliary variable and iteration precision in an unmanned aerial vehicle air-ground channel jitter error model;
substituting the beamforming vector and the auxiliary variable into a formula of a continuous convex approximation method for comparison, and selecting and outputting the beamforming vector and the auxiliary variable which meet the value range of the formula of the continuous convex approximation method;
and judging whether the difference of the iteration values of the multi-user downlink transmission capacity sums in the previous and subsequent times is smaller than the iteration precision or not according to the multi-user downlink transmission capacity sum, outputting a beam forming vector if the difference is smaller than the iteration precision, and circularly comparing whether the beam forming vector and the auxiliary variable meet the value range of a convex approximation method or not if the difference is larger than the iteration precision.
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CN115842582A (en) * | 2022-11-24 | 2023-03-24 | 南通大学 | Wireless transmission method and device for resisting random jitter of unmanned aerial vehicle |
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CN115685067A (en) * | 2022-11-07 | 2023-02-03 | 江西理工大学 | Normal-mode signal blind estimation method and system for positioning and tracking of multi-rotor unmanned aerial vehicle |
CN115842582A (en) * | 2022-11-24 | 2023-03-24 | 南通大学 | Wireless transmission method and device for resisting random jitter of unmanned aerial vehicle |
CN115842582B (en) * | 2022-11-24 | 2023-09-15 | 南通大学 | Wireless transmission method and device for resisting random jitter of unmanned aerial vehicle |
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