Rotatable antenna enabled unmanned aerial vehicle communication method and system

Abstract

The invention discloses a rotatable antenna enabled unmanned aerial vehicle communication method and system, unmanned aerial vehicle network side equipment adopts a rotatable array antenna to serve multiple users, user transmission service requirements are considered, the unmanned aerial vehicle network side equipment adopts limited block length to measure information transmission rate, and the orientation of an antenna array and a precoder are jointly designed. And the unmanned aerial vehicle network side equipment rotates the antenna array to the optimal orientation, a precoder is adopted to weight a multi-user signal, the weighted multi-user signal is sent to each user in a short packet form, and a terminal user demodulates and decodes information required by the terminal user. The method has certain universality and is suitable for various system design criteria. Compared with the prior art, the signal receiving power can be effectively improved, and the system coverage range and the link reliability are improved. In addition, by flexibly adjusting the antenna direction, the channel correlation between the users can be reduced, and the multi-user channel vector tends to be orthogonal, so that the pre-coding gain is remarkably improved, and the multi-user communication performance of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a rotatable antenna-enabled UAV communication method and system. Background Technology

[0002] In future wireless communication networks, achieving integrated air-space-ground communication is one of the key technological development directions. Among these, unmanned aerial vehicle (UAV) communication technology, with its high flexibility and mobility, can dynamically adapt to various network needs, demonstrating enormous application potential, particularly in scenarios such as rural coverage, emergency communication, and disaster recovery. Meanwhile, deploying large-scale antenna arrays at base stations (BS) using massive MIMO can significantly improve spectral and energy efficiency. However, due to the physical size, weight, and power constraints of UAVs, large-scale deployment of MIMO systems on UAVs still faces many challenges. Against this backdrop, the introduction of millimeter-wave technology can not only utilize abundant spectrum resources to improve communication performance but also enable compact and lightweight antenna designs, thereby effectively alleviating the deployment challenges of large-scale MIMO systems on UAVs.

[0003] To improve the transmission performance of UAV MIMO communication systems, precoding design has become a research hotspot. Existing research has proposed various all-digital precoding schemes to optimize transmission efficiency. However, the high hardware cost and significant power consumption of all-digital architectures, requiring numerous radio frequency links, limit practical applications. Therefore, in recent years, hybrid digital-analog precoding technology has emerged as an efficient alternative, achieving a good balance between system performance, hardware cost, and energy consumption.

[0004] While existing research has made some progress in the field of UAV MIMO, most works assume that the UAV base station uses an ideal isotropic antenna with a fixed orientation and ignore the influence of actual antenna radiation characteristics. This leads to two key problems. First, the radiation pattern of an actual antenna has a certain directionality. A fixed antenna orientation may place some users in the low-gain sidelobe region, resulting in severe signal attenuation. Second, since signal propagation in UAV communication is dominated by line-of-sight (LoS) transmission, a fixed antenna orientation may cause some users to have similar azimuth cosine values, leading to highly correlated channel vectors and severe multi-user interference. Therefore, traditional UAV communication with fixed antenna orientation cannot meet the diverse transmission needs of users, and there is an urgent need for effective new UAV communication methods and designs enabled by rotatable antennas. However, since antenna rotation dynamically changes the user channel vector, it affects channel spatial correlation and precoding optimization design. Therefore, how to theoretically model and characterize the impact of antenna array rotation on system design and performance gain is a very challenging problem. At the same time, due to the severe coupling between antenna array orientation and precoder, the joint design optimization problem of array antenna orientation and precoder is very complex and difficult to solve. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a rotatable antenna-enabled UAV communication method and system to improve system transmission performance.

[0006] Technical Solution: To achieve the above objectives, the present invention provides the following technical solution:

[0007] A rotatable antenna-enabled UAV communication method, wherein the UAV network-side device uses a rotatable array antenna to transmit information to multiple terminal users, the method comprising the following steps:

[0008] Obtain multi-user communication content and service transmission requirements;

[0009] The performance of multi-user short packet transmission is evaluated based on the finite block length information theory, and the multi-user transmission requirements are equivalently converted into quality of service (QoS) constraints expressed in terms of user-end signal-to-noise ratio (SINR).

[0010] Under the premise of satisfying multi-user QoS constraints, based on system performance metrics and design criteria, and considering the radiation pattern of the antenna in the actual direction, a joint optimization problem of precoding and antenna array direction is constructed and solved to obtain the optimal precoding matrix and antenna array direction.

[0011] After adjusting the antenna array to the optimal orientation and using the optimal precoder to weight the multi-user signals, the signals are sent to each terminal user in the form of short packets.

[0012] Preferably, the rotation of the rotatable array antenna is achieved in any of the following ways: using a gimbal system, fixing the gimbal to the UAV body, configuring the array antenna on the gimbal, and controlling the angle of the gimbal to achieve the rotation of the antenna; or using a multi-rotor UAV with a tiltable body, changing the UAV attitude by adjusting the thrust of each rotor, driving the array antenna rigidly fixed to the body to rotate accordingly, thereby achieving dynamic adjustment of the antenna direction.

[0013] Preferably, the rotatable array antenna is an omnidirectional antenna or a directional antenna.

[0014] Preferably, the requirements for multi-user communication service transmission obtained by the UAV network-side device include the data transmission latency, transmission bandwidth, and maximum acceptable error probability of short packet transmission for each user.

[0015] Preferably, the UAV network-side device evaluates the multi-user short packet transmission performance based on the finite block length information theory and converts the multi-user transmission requirements into QoS constraints expressed in SINR. Specifically, it determines the block length of short packet transmission based on transmission bandwidth and transmission delay, determines the short packet transmission rate based on the finite block length achievable rate, and determines the minimum received SINR constraint corresponding to the minimum short packet transmission rate constraint of the user based on the monotonically increasing characteristic of the finite block length achievable rate expression with respect to the user SINR within the non-negative rate range. This converts the multi-user short packet transmission requirements into QoS constraints expressed in user SINR.

[0016] Preferably, the joint optimization problem of precoding and antenna array orientation based on system performance metrics and design criteria includes any of the following methods:

[0017] With minimizing transmission power as the design criterion, the joint design problem model of precoding and array antenna orientation is specifically as follows: under user QoS constraints, optimize the precoding matrix and antenna orientation to minimize transmission power;

[0018] With maximizing the weighted sum rate as the design criterion, the joint design problem model of precoding and array antenna orientation is specifically as follows: under the constraints of user QoS and total power, optimize the precoding matrix and antenna orientation to maximize the multi-user weighted short packet sum rate;

[0019] The system performance is measured using the maximum-minimum fairness criterion. The joint design problem model of precoding and array antenna orientation is specifically as follows: under the constraints of user QoS and total power, optimize the precoding matrix and antenna orientation to maximize the minimum user short packet transmission rate.

[0020] Preferably, the pre-encoder is a pure digital pre-encoder or a hybrid digital-analog pre-encoder.

[0021] As a preferred method, the approach to solving the joint optimization problem of precoding and antenna array orientation includes the following steps:

[0022] (1) Reconstruct the original optimization problem mathematically and construct a partial augmented Lagrangian optimization problem;

[0023] (2) Set the initial optimization variable values, and initialize the penalty factor and dual variable at the same time;

[0024] (3) Under the premise of fixing the penalty factor and dual variables, solve the optimization problem and update the original optimization variables;

[0025] (4) Calculate the constraint error norm of the current optimization variable. If the error norm is less than the preset threshold or the number of iterations reaches the upper limit, output the optimal precoding and antenna direction; otherwise, proceed to the next step to continue the iteration.

[0026] (5) When the error norm reaches below the preset value, update the dual variable; when the error norm does not reach the preset value, adaptively adjust the penalty factor; jump to step (3).

[0027] Preferably, when solving the joint optimization problem of precoding and antenna array orientation, the current communication environment is first evaluated, and it is determined whether there is a precoding scheme and antenna orientation that meet QoS and power constraints. If the conditions are met, the solution continues; otherwise, the process terminates. The evaluation methods include:

[0028] Randomly generate orientation samples for several antenna arrays;

[0029] The array orientation with the lowest user channel correlation is selected as the initial solution for the array orientation. The initial solution for the antenna orientation is obtained by calculating the outer product of the initial array orientation and the normalized vector of the base station with respect to the center of the user distribution location.

[0030] With fixed initial antenna and array orientations, the initial solution is obtained by solving the problem of minimizing transmission power under QoS constraints.

[0031] A rotatable antenna-enabled unmanned aerial vehicle (UAV) communication system includes a UAV network-side device and an end-user device. The UAV network-side device implements the rotatable antenna-enabled UAV communication method. The end-user device receives signals and demodulates and decodes them to obtain service information.

[0032] Beneficial Effects: This invention provides a rotatable antenna-enabled UAV communication method. By adjusting the UAV's attitude or gimbal system, the array antenna can be rotated omnidirectionally, allowing the UAV network-side equipment to dynamically adjust the antenna's main lobe direction to enhance the signal reception power for target users. Furthermore, the rotatable antenna allows for adaptive beam pointing adjustment, reducing multi-user channel correlation and providing additional optimization freedom for precoding design, thereby further improving UAV communication performance. It has the following beneficial effects:

[0033] (1) The radiation pattern of the directional antenna in the actual system is taken into consideration, which makes the proposed communication method more practical.

[0034] (2) Rotatable antenna-enabled UAV network-side equipment can dynamically adjust the direction of the main lobe of the antenna according to the user's location, so as to avoid the user falling into the low gain sidelobe region, thereby effectively improving the signal receiving power, improving the system coverage and link reliability.

[0035] (3) Rotatable antenna-enabled UAV network-side equipment can reduce channel correlation between users by flexibly adjusting the antenna direction, making the multi-user channel vectors tend to be orthogonal, thereby significantly improving the precoding gain and enhancing the multi-user communication performance of the system.

[0036] (4) This invention is applicable to commonly used system performance measurement criteria, including but not limited to minimizing transmission power, weighted sum rate and maximum minimum fairness, and has high universality.

[0037] (5) The present invention further transforms the original complex optimization problem with coupling constraints by transforming, reconstructing and decomposing the problem, and decomposes it into a series of small-scale sub-problems that can be solved quickly, thereby greatly reducing the difficulty of solving the problem and the computational complexity. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method according to an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of the UAV network-side device according to an embodiment of the present invention.

[0040] Figure 3 This is a comparison chart showing the minimum transmission power performance of the method of this invention under different base station transmitting antennas and that of traditional UAV communication using fixed antenna orientation, while meeting user QoS conditions.

[0041] Figure 4 This is a comparison chart showing the minimum transmission power performance of the method of the present invention and the traditional UAV communication using a fixed antenna orientation under different phase shifter phase resolutions, while meeting the user's QoS conditions. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1

[0044] This invention discloses a rotatable antenna-enabled UAV communication method, which uses a UAV as a network-side device to transmit information to multiple terminal users; the UAV network-side device employs a rotatable array antenna; such as Figure 1 As shown, the specific communication method of the UAV network-side equipment includes: acquiring multi-user communication content and service transmission requirements; evaluating the multi-user short packet transmission performance based on finite block length information theory, and converting the multi-user transmission requirements into QoS constraints represented by SINR; under the premise of satisfying the multi-user QoS constraints, constructing and solving a joint optimization problem of precoding and antenna array orientation according to specific system performance metrics and design criteria to obtain the optimal precoding matrix and antenna array orientation; adjusting the antenna array to the optimal orientation, and using the optimal precoder to weight the multi-user signals before sending them to each terminal user in the form of short packets. After receiving the transmitted information, the terminal user treats other user signals as interference, demodulates and decodes the signals required by itself to obtain communication service information.

[0045] In this embodiment, the UAV network side device adopts a rotatable array antenna. The omnidirectional rotation is achieved by: (1) using a gimbal system, fixing a high-precision gimbal to the UAV body, and configuring an array antenna on the gimbal. The omnidirectional rotation of the antenna is achieved by precisely controlling the angle of the gimbal; (2) using a multi-rotor UAV with a tiltable body, changing the attitude of the UAV by adjusting the thrust of each rotor, thereby driving the array antenna rigidly fixed to the body to rotate accordingly, and achieving dynamic adjustment of the antenna direction.

[0046] The rotatable array antenna in this embodiment is an omnidirectional antenna. In some other embodiments, the rotatable array antenna may also be a different type of directional antenna, such as a commonly used half-wave dipole directional antenna, to adapt to different communication needs.

[0047] Specifically, the UAV network-side equipment acquires the multi-user communication service transmission requirements, including the data transmission latency, transmission bandwidth, and maximum acceptable error probability of short packet transmission for each user. The UAV network-side equipment evaluates the multi-user short packet transmission performance based on finite block length information theory and converts the multi-user transmission requirements into QoS constraints expressed in SINR. Specifically, it determines the block length of short packet transmission based on transmission bandwidth and transmission latency, determines the short packet transmission rate based on the finite block length achievable rate, and, based on the monotonically increasing characteristic of the finite block length achievable rate expression with respect to user SINR within the non-negative rate range, uses methods such as the bisection method to determine the minimum received SINR constraint corresponding to the user's minimum short packet transmission rate constraint, thus converting the multi-user short packet transmission requirements into QoS constraints expressed in user SINR.

[0048] In specific implementation, based on specific performance metrics and design criteria, a joint optimization problem of precoding and antenna array orientation is constructed and solved, including but not limited to: (1) Using minimizing transmission power as the design criterion, the joint design problem model of precoding and antenna array orientation is specifically: under user QoS constraints, optimize the precoding matrix and antenna orientation to minimize transmission power; (2) Using maximizing the weighted sum rate as the design criterion, the joint design problem model of precoding and antenna array orientation is specifically: under user QoS and total power constraints, optimize the precoding matrix and antenna orientation to maximize the multi-user weighted short packet sum rate; (3) Using the maximum-minimum fairness criterion to measure system performance, the joint design problem model of precoding and antenna array orientation is specifically: under user QoS and total power constraints, optimize the precoding matrix and antenna orientation to maximize the minimum user short packet transmission rate.

[0049] The precoder used by the UAV network-side equipment can be a pure digital precoder or a hybrid digital-analog precoder.

[0050] In this embodiment, the method for solving the joint optimization problem of precoding and antenna array orientation includes the following steps:

[0051] (1) Reconstruct the original optimization problem mathematically and construct a partial augmented Lagrangian optimization problem;

[0052] (2) Set the initial optimization variable values, and initialize the penalty factor and dual variable at the same time;

[0053] (3) Under the premise of fixing the penalty factor and dual variables, solve the optimization problem and update the original optimization variables;

[0054] (4) Calculate the constraint error norm of the current optimization variable. If the error norm is less than the preset threshold or the number of iterations reaches the upper limit, output the optimal precoding and antenna direction; otherwise, proceed to the next step to continue the iteration.

[0055] (5) When the error norm reaches below the preset value, update the dual variable; when the error norm does not reach the preset value, adaptively adjust the penalty factor; jump to step (3).

[0056] By reconstructing, transforming, and decomposing the original optimization problem, the original complex optimization problem can be effectively broken down into a series of small-scale subproblems that can be solved quickly, thereby significantly reducing the difficulty of solving the problem and the computational complexity.

[0057] Specifically, in some embodiments, solving the optimization problem and updating the original optimization variables while keeping the penalty factor and dual variables fixed further includes:

[0058] The optimization variables are decomposed into multiple variable blocks, and there is no coupling between the different variable blocks in the constraints;

[0059] The augmented Lagrange problem is decomposed into a series of small-scale subproblems by using methods such as block coordinate descent. Each subproblem can be solved quickly or in a closed loop.

[0060] Specifically, the precoding can be solved using a block coordinate descent method, updating one matrix element at a time while keeping other elements fixed. The optimization problem for a single matrix element can be solved in a closed loop. Antenna orientation and array orientation can be solved quickly using a manifold optimization method.

[0061] In some embodiments, when solving the joint optimization problem of precoding and antenna array orientation, the current communication environment is first evaluated, and it is determined whether there is a precoding scheme and antenna orientation that meet QoS constraints and power constraints; if the conditions are met, the solution continues, otherwise the process is terminated.

[0062] Specifically, the current communication environment is assessed, and it is determined whether there are precoding schemes and antenna orientation combinations that meet QoS and power constraints. This includes:

[0063] Randomly generate orientation samples for several antenna arrays;

[0064] The array orientation with the lowest user channel correlation is selected as the initial solution for the array orientation. The initial solution for the antenna orientation is obtained by calculating the outer product of the initial array orientation and the normalized vector of the base station with respect to the center of the user distribution location.

[0065] With fixed initial antenna and array orientations, the initial solution is obtained by solving the problem of minimizing transmission power under QoS constraints.

[0066] This embodiment provides a rotatable antenna-enabled UAV communication method. By adjusting the UAV's attitude or gimbal system, the array antenna can be rotated omnidirectionally, allowing the UAV network-side equipment to dynamically adjust the antenna's main lobe direction to enhance the signal reception power for target users. Furthermore, the rotatable antenna can adaptively adjust the beam pointing to reduce multi-user channel correlation and provide additional optimization degrees of freedom for precoding design, thereby further improving UAV communication performance.

[0067] Example 2

[0068] This invention discloses a rotatable antenna-enabled unmanned aerial vehicle (UAV) communication system, including a UAV network-side device and an end-user device, for implementing the communication method described in Embodiment 1. Figure 2 As shown, the UAV network-side equipment uses a rotatable array antenna. The antenna array orientation and precoder are optimized to obtain the optimal antenna array orientation and precoding design. The precoder can adopt a pure digital precoding architecture or a hybrid precoding architecture. The UAV network-side equipment rotates the antenna array to the optimal direction and uses the optimal precoder to weight the multi-user signals and send them in the form of short packets. The terminal user equipment receives the signals and demodulates and decodes them to obtain service information.

[0069] The rotatable antenna-enabled UAV communication system provided in this embodiment uses a rotatable array antenna on the UAV network side device. It can select an omnidirectional antenna or different types of directional antennas according to the actual communication scenario. Taking into account the user's requirements for transmission reliability, latency and rate, the array antenna orientation and pre-encoder are jointly designed, and short packet transmission is used to achieve low latency communication, which can significantly improve the system transmission performance.

[0070] Example 3

[0071] This invention discloses a rotatable antenna-enabled UAV communication method, which, in conjunction with a specific scenario and with minimizing transmission power as the design criterion, exemplarily illustrates the communication process of the UAV network-side device. In this embodiment, the UAV network-side device adopts a hybrid precoding architecture. Under the constraints of user QoS and feasible phase of the analog precoder, it jointly designs the array antenna orientation and hybrid precoding to minimize transmission power, including the following steps:

[0072] Step 1: Consider a downlink single-cell short-packet multi-user MIMO system, in which a hovering drone acts as a base station. Each transmitting antenna directs to A ground user transmits a signal, and the drone hovers at the location. User collection This means that the coordinates of each user k are represented as follows: Assume users are randomly distributed on the ground. Within a circle with a radius of 100 meters centered on the user. Since drone communication primarily uses Low-Speed ​​(LoS) transmission, the distance from the drone base station to the user... The channel vector can be represented as Wherein, large-scale link gain is defined as

[0073]

[0074] GHz is the carrier frequency. It is an alignment vector. Considering the antenna spacing of the UAV network-side equipment is half a wavelength, then... ,in, and Representing users respectively The angles between the antenna coordinate axes and the array coordinate axes are defined here as the elevation angle and azimuth angle, respectively. Since many antennas have axisymmetric radiation patterns, we adopt... The radiation pattern used to represent an antenna is a continuous, smooth function of the elevation angle. When an unmanned aerial vehicle (UAV) base station uses an isotropic antenna, the radiation pattern can be represented as follows: When a half-wave dipole is used, the radiation pattern can be represented as follows: in, It is a normalization coefficient that makes To further simplify the representation, we introduce a set of orthogonal unit vectors. and Let represent the directions of the array coordinate axes and the antenna coordinate axes respectively, and they satisfy ... Thus, the azimuth and elevation angles can be expressed as follows: and ,in, This represents the normalized user direction vector. Therefore, we can use the channel vector... and unit alignment vector Rewritten as a function of the two vectors mentioned above and .

[0075] Step 2: The drone base station learns the multicast communication service requirements, specifically including transmission error probability requirements. , Minimum transmission rate requirement for user short packets bits / s / Hz, transmission bandwidth is B= MHz, transmission delay is The background noise power spectral density is -174 dBm / Hz.

[0076] Step 3: The UAV base station measures the multi-user short packet transmission performance based on the finite block length information theory. The base station uses a hybrid precoding architecture. Then, the user... The received signal is ,in, User Digital precoding, It is analog precoding. This refers to the number of RF links. We consider that analog precoding can be implemented using phase shifters with infinite precision readout and phase shifters with finite precision. Specifically, for phase shifters with infinite precision readout, the phase constraint for analog precoding can be expressed as... For a discrete phase shifter, the phase constraint can be expressed as: We use Indicate to the user The signal flow, using Indicates user Background noise.

[0077] To meet latency requirements, the UAV network-side equipment uses short packets to transmit signals to multiple users (e.g., long transmission block length). ), the transport block length is .user Will Treat it as background Gaussian noise, demodulate and decode the signal. Therefore, users The received SINR is

[0078]

[0079] According to the finite block length information theory, the user The achievable rate of short packets is

[0080]

[0081] in, , , It is a Gaussian Q-function. It is the inverse Gaussian Q-function, i.e. .

[0082] Therefore, the multi-user short packet transmission rate requirement can be expressed as: Because of the given The achievable rate of a finite block length Regarding user SINR Monotonically increasing, it can be calculated using the bisection method. The unique positive real solution , , , , This transforms the multi-user short packet transmission rate requirement into a QoS constraint represented by the user SINR. .

[0083] Step 4: Considering QoS constraints, feasible phase of simulated precoding, and antenna array rotation constraints, establish a model for minimizing transmission power optimization:

[0084]

[0085] in, It is digital precoding.

[0086] Introducing auxiliary variables , will optimize the problem Reconstructed

[0087] in, Then define the problem. Partial augmented Lagrange problem:

[0088]

[0089] Wherein, the objective function is

[0090]

[0091] here and As dual variables, It is a punishment factor. , and These represent the original variable and the dual variable, respectively.

[0092] Step 5: Randomly generate One antenna array facing Select the array with the lowest user channel correlation towards the initial solution. ,in, Generate antenna orientation ,in, This represents the outer product. When using a continuous phase shifter, the initial analog precode is set to... When using a discrete phase shifter, the initial analog precoding is set to... Then, solve the following optimization problem to obtain the initial digital precoding.

[0093]

[0094] in, The optimization problem described above can be transformed into a convex optimization problem and solved using tools such as CVX.

[0095] Step 6: Set the number of iterations ,initialization , , , Set the maximum number of iterations. Set error threshold .

[0096] Step 7: Fix the dual variable Solving partially augmented Lagrangian optimization problems under the condition of a penalty factor. To update the original optimization variables .

[0097] Step 8: Calculate the constraint error norm .like Then the subgradient method is used to update the dual variable.

[0098]

[0099]

[0100]

[0101] Otherwise, do not update the dual variable, i.e., set Update penalty factors .

[0102] Step 9: Check whether the constraint error norm and the number of iterations satisfy the algorithm's iterative convergence condition. If... or If the algorithm stops iterating, it will output the optimal array antenna orientation. and optimal hybrid precoding Otherwise, proceed to step 7.

[0103] More specifically, in this embodiment, since the augmented Lagrangian optimization problem has a decomposable structure, that is, the optimization variables can be decomposed into multiple variable blocks, and different variable blocks are not coupled in the constraints, the augmented Lagrangian problem can be decomposed into a series of small-scale subproblems using methods such as block coordinate descent. Each subproblem can be solved quickly or even in closed form. In step 7, a method for solving the augmented Lagrangian optimization problem of the orientation and hybrid precoding part of a rotatable antenna-enabled UAV communication antenna array specifically includes the following steps:

[0104] (7.1) Set the number of iterations ,initialization , , , Set the maximum number of iterations. Error threshold .

[0105] (7.2) Update digital precoding

[0106]

[0107] (7.3) Solve the following optimization problem to update the analog precoder.

[0108]

[0109] in, , .

[0110] (7.4) ,when ,right ,renew

[0111] ,right ,renew in, It is any phase; otherwise, update.

[0112]

[0113] Among them, when , ,otherwise, .definition ,when hour, ,otherwise, It is an equation The unique solution can be obtained using the binary search method.

[0114] (7.5) Solve the following optimization problem to update the antenna orientation. ,

[0115]

[0116] The objective function of the above optimization problem is defined as follows:

[0117]

[0118] (7.6) Solve the following optimization problem to update the antenna orientation. ,

[0119]

[0120] (7.7) Settings Calculate the difference of continuous objective functions

[0121]

[0122] like or Then terminate the iteration and output. , , and Otherwise, proceed to step (7.2).

[0123] More specifically, in this embodiment, in step (7.3), a method for updating the analog precoder employs a block coordinate descent approach, updating one matrix element at a time while keeping other elements fixed. The optimization problem for a single matrix element can be solved in a closed-form solution, specifically including the following steps:

[0124] (7.3.1) Initialize the number of iterations ,set up Set the maximum number of iterations. Sum of error thresholds .

[0125] (7.3.2) Initialization For any Execute steps (7.3.5)-(7.3.7).

[0126] (7.3.3) Calculation .

[0127] (7.3.4) If a continuous phase shifter is used, then calculate... .

[0128] (7.3.5) If a discrete phase shifter is used, calculate... .

[0129] (7.3.6) Calculation .

[0130] (7.3.7) Update .

[0131] (7.3.8) Update ,set up .

[0132] (7.3.9) If or Then output Otherwise, proceed to step (7.3.2).

[0133] More specifically, in this embodiment, in step (7.5), a method for updating the antenna orientation, since the considered antenna radiation pattern is a continuous function and the constraint condition is a unit spherical manifold, can be quickly solved using a manifold optimization method, specifically including the following steps:

[0134] (7.5.1) Initialize the number of iterations ,initialization Set the maximum number of iterations. Sum of error thresholds .

[0135] (7.5.2) Definition , , Calculate the Euclidean gradient

[0136]

[0137] (7.5.3) Calculate the gradient of the manifold ,in, Let x be the projection of x onto y in an M-dimensional modular manifold space.

[0138] (7.5.4) Calculate the search direction

[0139]

[0140] in, .

[0141] (7.5.5) Initialize step size , .

[0142] (7.5.6) If and Then set , If not, proceed to step (7.5.7); otherwise, proceed to step (7.5.8).

[0143] (7.5.7) Update ,set up .

[0144] (7.5.8) If or Output Otherwise, proceed to step (7.5.2).

[0145] More specifically, in this embodiment, in step (7.6), a method for updating the orientation of the antenna array coordinate axes can be quickly solved using manifold optimization methods because the antenna radiation pattern under consideration is a continuous function and the constraint condition is a unit spherical manifold. Specifically, it includes the following steps:

[0146] (7.6.1) Initialize the number of iterations ,initialization Set the maximum number of iterations. Sum of error thresholds .

[0147] (7.6.2) Calculate the Euclidean gradient

[0148]

[0149] in, .

[0150] (7.6.3) Calculate the manifold gradient .

[0151] (7.6.4) Calculate the search direction

[0152]

[0153] in, .

[0154] (7.6.5) Initialize step size , .

[0155] (7.6.6) If and Then set , If not, proceed to step (7.6.7); otherwise, proceed to step (7.6.8).

[0156] (7.6.7) Update ,set up .

[0157] (7.6.8) If or Output Otherwise, proceed to step (7.6.2).

[0158] The above describes the specific implementation and application of the method of the present invention in Example 3.

[0159] To verify the effectiveness of the rotatable antenna-enabled UAV communication method based on minimizing transmission power under QoS provided in Example 3, a simulation experiment is provided. The simulation experiment obtains the results for each experimental parameter configuration by averaging the experimental results of 100 random sample experiments from user channels.

[0160] Figure 3 The minimum transmission power performance of the method of the present invention and the traditional UAV communication using a fixed antenna orientation were compared under different base station transmitting antennas in Example 3 to meet user QoS conditions. RF link and continuous phase shifter services total User. By Figure 3 It can be seen that the method of the present invention always achieves optimal performance under different base station transmitting antennas.

[0161] Figure 4 This example demonstrates a comparison of the minimum transmission power performance of the method of the present invention with that of conventional UAV communication using a fixed antenna orientation under different phase shifter phase resolutions, while satisfying user QoS conditions. The base station uses... RF link and continuous phase shifter services total User. By Figure 4 It can be seen that the method of the present invention is superior to the existing fixed antenna orientation scheme. Moreover, as the resolution of the phase shifter increases, the transmission power required by the method of the present invention converges to the optimal power at a faster rate. In contrast, the existing fixed antenna orientation method has a slower convergence rate. This shows that the method of the present invention can, to a certain extent, make up for the performance loss caused by the limited resolution of the phase shifter, further demonstrating the advantages of the method of the present invention.

[0162] Any aspects of this invention not described in detail are well-known to those skilled in the art.

[0163] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A rotatable antenna-enabled UAV communication method, characterized in that, The UAV network-side equipment uses a rotatable array antenna to transmit information to multiple end users. The method includes the following steps: Obtain multi-user communication content and service transmission requirements; The performance of multi-user short packet transmission is evaluated based on the finite block length information theory, and the multi-user transmission requirements are equivalently converted into quality of service (QoS) constraints expressed in terms of user-end signal-to-noise ratio (SINR). Under the premise of satisfying multi-user QoS constraints, based on system performance metrics and design criteria, and considering the radiation pattern of the antenna in the actual direction, a joint optimization problem of precoding and antenna array direction is constructed and solved to obtain the optimal precoding matrix and antenna array direction. After adjusting the antenna array to the optimal orientation and using the optimal precoder to weight the multi-user signals, the signals are sent to each terminal user in the form of short packets.

2. The UAV communication method with a rotatable antenna enabled according to claim 1, characterized in that, The rotation of the rotatable array antenna is achieved in any of the following ways: using a gimbal system, the gimbal is fixedly installed on the UAV body, and the array antenna is configured on the gimbal. The antenna rotation is achieved by controlling the angle of the gimbal; or using a multi-rotor UAV with a tiltable body, the UAV attitude is changed by adjusting the thrust of each rotor, which drives the array antenna, which is rigidly fixed to the body, to rotate accordingly, thereby achieving dynamic adjustment of the antenna direction.

3. The UAV communication method with a rotatable antenna enabled according to claim 1, characterized in that, The rotatable array antenna can be an omnidirectional antenna or a directional antenna.

4. The UAV communication method with a rotatable antenna enabled according to claim 1, characterized in that, The requirements for multi-user communication service transmission obtained by the UAV network-side equipment include the data transmission latency, transmission bandwidth, and maximum acceptable error probability of short packet transmission for each user.

5. A rotatable antenna-enabled UAV communication method according to claim 1, characterized in that, The aforementioned UAV network-side equipment evaluates the multi-user short packet transmission performance based on the finite block length information theory and converts the multi-user transmission requirements into QoS constraints expressed in SINR. Specifically, it determines the block length of short packet transmission based on transmission bandwidth and transmission delay, determines the short packet transmission rate based on the finite block length achievable rate, and determines the minimum received SINR constraint corresponding to the minimum short packet transmission rate constraint of the user based on the monotonically increasing characteristic of the finite block length achievable rate expression with respect to the user SINR within the non-negative rate range. This converts the multi-user short packet transmission requirements into QoS constraints expressed in user SINR.

6. A rotatable antenna-enabled UAV communication method according to claim 1, characterized in that, The aforementioned joint optimization problem of precoding and antenna array orientation, based on system performance metrics and design criteria, includes any of the following methods: With minimizing transmission power as the design criterion, the joint design problem model of precoding and array antenna orientation is specifically as follows: under user QoS constraints, optimize the precoding matrix and antenna orientation to minimize transmission power; With maximizing the weighted sum rate as the design criterion, the joint design problem model of precoding and array antenna orientation is specifically as follows: under the constraints of user QoS and total power, optimize the precoding matrix and antenna orientation to maximize the multi-user weighted short packet sum rate; The system performance is measured using the maximum-minimum fairness criterion. The joint design problem model of precoding and array antenna orientation is specifically as follows: under the constraints of user QoS and total power, optimize the precoding matrix and antenna orientation to maximize the minimum user short packet transmission rate.

7. A rotatable antenna-enabled UAV communication method according to claim 1, characterized in that, The precoder can be a pure digital precoder or a hybrid digital-analog precoder.

8. A rotatable antenna-enabled UAV communication method according to claim 1, characterized in that, The method for solving the joint optimization problem of precoding and antenna array orientation includes the following steps: (1) Reconstruct the original optimization problem mathematically and construct a partial augmented Lagrangian optimization problem; (2) Set the initial optimization variable values, and initialize the penalty factor and dual variable at the same time; (3) Under the premise of fixing the penalty factor and dual variables, solve the optimization problem and update the original optimization variables; (4) Calculate the constraint error norm of the current optimization variable. If the error norm is less than the preset threshold or the number of iterations reaches the upper limit, output the optimal precoding and antenna direction; otherwise, proceed to the next step to continue the iteration. (5) When the error norm reaches below the preset value, update the dual variable; when the error norm does not reach the preset value, adaptively adjust the penalty factor. Skip to step (3).

9. A rotatable antenna-enabled UAV communication method according to claim 1, characterized in that, When solving the joint optimization problem of precoding and antenna array orientation, the current communication environment is first evaluated, and it is determined whether there is a precoding scheme and antenna orientation that meet QoS constraints and power constraints. If the conditions are met, the solution process continues; otherwise, the process terminates. The evaluation methods include: Randomly generate orientation samples for several antenna arrays; The array orientation with the lowest user channel correlation is selected as the initial solution for the array orientation. The initial solution for the antenna orientation is obtained by calculating the outer product of the initial array orientation and the normalized vector of the base station with respect to the center of the user distribution location. With fixed initial antenna and array orientations, the initial solution is obtained by solving the problem of minimizing transmission power under QoS constraints.

10. A rotatable antenna-enabled unmanned aerial vehicle (UAV) communication system, comprising UAV network-side equipment and end-user equipment, characterized in that, The UAV network-side device implements a UAV communication method with rotatable antenna enabled according to any one of claims 1-9; the terminal user equipment receives signals and demodulates and decodes them to obtain service information.

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