A method for designing optimal flight height of UAV assisted communication with STAR-RIS

Abstract

The application discloses a kind of optimal flight height design methods of UAV carrying STAR-RIS auxiliary communication, comprising: setting the reflection split coefficient of STAR-RIS, phase shift matrix and the initial value of unmanned aerial vehicle flight height;Then respectively calculate the iterative expression of the reflection split coefficient of STAR-RIS and unmanned aerial vehicle flight height;The reflection split coefficient of STAR-RIS and the iterative expression of unmanned aerial vehicle flight height calculated are used to calculate the unmanned aerial vehicle flight height under current condition;Finally, whether the unmanned aerial vehicle height is judged to converge, if convergence, then the optimal flight height of unmanned aerial vehicle is obtained;If not convergence, then repeat the previous iteration step, until the convergence condition is satisfied.The application uses the advantage of unmanned aerial vehicle carrying STAR-RIS auxiliary communication under the scene of communication direct link blockage, effectively improves the performance of wireless communication system while ensuring the safe flight height of unmanned aerial vehicle.

Description

Technical Field

[0001] This invention relates to the field of Internet of Things (IoT) technology, and in particular to a method for designing the optimal flight altitude for a UAV equipped with STAR-RIS assisted communication. Background Technology

[0002] In the field of Internet of Things (IoT) technology, the growing demand for wireless connectivity and the emergence of the concept of interconnected everything necessitate new communication models, which will ultimately enable a multitude of new applications and disruptive technologies. With the vigorous development of IoT technology, various sensors, RFID, infrared sensors, and other devices can be used to collect data. However, the high energy consumption of existing technologies results in high communication costs. Therefore, Simultaneous Transmitting and Reflecting Reconfigurable Intelligent Surfaces (STAR-RIS) technology, as one of the key technologies proposed in IoT, has received extensive research from the industry.

[0003] When the direct link between the base station and the user is blocked, the gain of the direct channel is almost negligible. Constructing reflection and transmission links using STAR-RIS can effectively improve spectral efficiency and system energy efficiency. However, STAR-RIS is mostly mounted on building surfaces, which makes its performance less than ideal under certain unforeseen circumstances. In such cases, using drones to carry STAR-RIS can effectively solve this problem and further enhance system performance.

[0004] However, determining the optimal flight altitude for drones in dynamic environments remains a major challenge for the industry. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the aforementioned existing problems, the present invention is proposed.

[0007] Therefore, this invention provides a method for designing the optimal flight altitude for UAVs equipped with STAR-RIS assisted communication to solve the problem of poor performance of wireless communication systems in scenarios with limited communication environments.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] Set the initial values ​​for the STAR-RIS reflection splitting coefficient, phase shift matrix, and UAV flight altitude; then calculate the iterative expressions for the STAR-RIS reflection splitting coefficient and UAV flight altitude respectively.

[0010] The flight altitude of the UAV under the current conditions is calculated using the calculated STAR-RIS reflection splitting coefficient and the iterative expression of the UAV flight altitude.

[0011] Finally, determine whether the drone altitude has converged. If it has converged, the optimal flight altitude of the drone is obtained; if it has not converged, repeat the previous iterative steps until the convergence condition is met.

[0012] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication described in this invention, the specific steps for determining whether the UAV altitude has converged are: determining whether |H-H1|≤10 -5 If this convergence condition is met, the optimal flight altitude of the UAV is obtained; otherwise, let H = H1, β r =β r1 Then, re-execute the iterative expression using the calculated STAR-RIS reflection splitting coefficient and the UAV flight altitude to calculate the UAV flight altitude under the current conditions until H-H1|≤10 is satisfied. -5 At this point, the optimal flight altitude for the drone is obtained.

[0013] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication as described in this invention, wherein: the calculation of the STAR-RIS reflection splitting coefficient β r In the iterative expression, the STAR-RIS reflection splitting coefficient β r The iterative expression is represented as:

[0014]

[0015] In the formula, P max P represents the total transmit power of the base station. r P represents the power allocated by the base station to ground users. t This indicates the power allocated to the HAP by the base station.

[0016] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication as described in this invention, wherein: the reflection splitting coefficient β of the STAR-RIS... r In the iterative expression, C and D are represented as:

[0017]

[0018]

[0019] Where β0 and α represent the path loss and path loss factor per unit distance of 1m, σ 2 κ represents the noise power at the ground user and HAP, N is the number of STAR-RIS reflection and transmission units, and κ is the noise power at the ground user and HAP. BR and κ RU Let d represent the Ricean factor of the base station-to-UAV and UAV-to-ground user channels, respectively. BR and d RU d represents the distance from the base station to the drone and the distance from the drone to the ground user, respectively. RH This indicates the distance from the drone to the HAP.

[0020] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication described in this invention, wherein: the iterative expression for calculating the UAV flight altitude H is:

[0021]

[0022] In the formula, z HAP The z-axis represents the height of the HAP. b Indicates the height of the base station.

[0023] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication described in this invention, wherein: in the iterative expression of the UAV flight altitude H, A and B are represented as:

[0024]

[0025]

[0026] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication described in this invention, wherein: the calculated reflection splitting coefficient of STAR-RIS is used to obtain the phase shift matrix of STAR-RIS at this time, and the reflection phase shift matrix Φ is in the optimal phase shift matrix. r Represented as:

[0027]

[0028] In the formula, β r1 This represents the reflection splitting coefficient under the current conditions. This represents the reflection phase shift of the nth reflecting element.

[0029] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication described in this invention, wherein: the calculated reflection splitting coefficient of STAR-RIS is used to obtain the phase shift matrix of STAR-RIS at this time, and the transmission phase shift matrix Φ is included in the optimal phase shift matrix. t Represented as:

[0030]

[0031] In the formula, This represents the transmission phase shift of the nth transmission element.

[0032] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication as described in this invention, the reflection phase shift of the reflective element is specifically expressed as follows:

[0033]

[0034]

[0035] Where d represents the adjacent spacing between the reflecting and transmitting elements, λ represents the incident wave wavelength, and θ BR θ RU θ represents the departure angle of the base station relative to the drone and the arrival angle of the ground user relative to the drone, respectively. RH This represents the angle of arrival (HAP) relative to the drone.

[0036] As a preferred embodiment of the optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication as described in this invention, the transmission phase shift of the transmission element is specifically expressed as follows:

[0037]

[0038]

[0039] The beneficial effects of this invention are as follows: This invention combines the advantages of STAR-RIS and UAVs. In communication-limited scenarios, it utilizes the high maneuverability of UAVs and the ability of STAR-RIS to reflect and transmit signals to establish a more realistic wireless communication system. This invention can accurately derive the optimal flight altitude of UAVs using only the position information of each communication node in the system, and its computational complexity is low. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0041] Figure 1 A basic flowchart illustrating an optimal flight altitude design method for a UAV equipped with STAR-RIS assisted communication, provided in one embodiment of the present invention;

[0042] Figure 2 A wireless communication system model diagram of an optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication, provided as an embodiment of the present invention;

[0043] Figure 3 A comparison of the time complexity of this invention and conventional one-dimensional search for finding the optimal UAV altitude using a method for designing the optimal flight altitude with STAR-RIS assisted communication, as provided in one embodiment of this invention; Detailed Implementation

[0044] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0045] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0046] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0047] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0048] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] Example 1

[0051] Reference Figure 1-3 As one embodiment of the present invention, a method for designing the optimal flight altitude for a UAV equipped with STAR-RIS assisted communication is provided, such as... Figure 1 As shown, it includes the following steps:

[0052] S1: Set the initial values ​​of the STAR-RIS reflection splitting coefficient, phase shift matrix, and UAV flight altitude; then calculate the iterative expressions for the STAR-RIS reflection splitting coefficient and UAV flight altitude respectively.

[0053] Furthermore, this patent requires the drone to be equipped with a STAR-RIS-assisted wireless communication system, such as... Figure 2 As shown, the system includes a base station with a single antenna, a drone equipped with N passive reflection and transmission units STAR-RIS, a single-antenna ground user, and a single-antenna HAP.

[0054] Furthermore, the reflection splitting coefficient β of STAR-RIS is set. r The initial values ​​of the phase shift matrix and the UAV flight altitude H, where β r =0.5, H=10m;

[0055] Furthermore, the STAR-RIS reflection splitting coefficient β r The iterative expression is:

[0056]

[0057] In the formula, Pmax P represents the total transmit power of the base station. r P represents the power allocated by the base station to ground users. t The power allocated to the HAP by the base station, C and D, can be represented by the following formula:

[0058]

[0059]

[0060] Where β0 and α represent the path loss and path loss factor per unit distance of 1m, σ 2 κ represents the noise power at the ground user and HAP, N is the number of STAR-RIS reflection and transmission units, and κ is the noise power at the ground user and HAP. BR and κ RU Let d represent the Ricean factor of the base station-to-UAV and UAV-to-ground user channels, respectively. BR and d RU d represents the distance from the base station to the drone and the distance from the drone to the ground user, respectively. RH This indicates the distance from the drone to the HAP.

[0061] Furthermore, the iterative expression for the drone's flight altitude H is:

[0062]

[0063] In the formula, z HAP The z-axis represents the height of the HAP. b The heights of the base station, A and B, can be represented by the following formulas.

[0064]

[0065]

[0066] S2: Calculate the UAV's flight altitude under the current conditions using the calculated STAR-RIS reflection splitting coefficient and the iterative expression for the UAV's flight altitude;

[0067] Furthermore, by calculating the reflection splitting coefficient of STAR-RIS, the phase shift matrix of STAR-RIS at this point is obtained. The optimal phase shift matrix can be expressed as:

[0068]

[0069]

[0070] In the formula, Φ r Φ t Let β represent the reflection and transmission phase shift matrices, respectively. r1This represents the reflection splitting coefficient under the current conditions. The optimal reflection and transmission phase shifts of the nth reflecting and transmitting elements are represented as follows:

[0071]

[0072]

[0073] Where d represents the adjacent spacing between the reflecting and transmitting elements, λ represents the incident wave wavelength, and θ BR θ RU θ represents the departure angle of the base station relative to the drone and the arrival angle of the ground user relative to the drone, respectively. RH This represents the angle of arrival (HAP) relative to the drone.

[0074] S3: Finally, determine whether the drone altitude has converged. If it has converged, the optimal flight altitude of the drone is obtained; if it has not converged, repeat the previous iteration steps until the convergence condition is met.

[0075] Furthermore, determine whether |H-H1|≤10 is satisfied. -5 If this convergence condition is met, the optimal flight altitude of the UAV is obtained; otherwise, let H = H1, β r =β r1 Jump back to calculate the reflection splitting coefficient β under the current conditions. r1 And the phase shift matrix, recalculate the reflection splitting coefficient β under the current conditions. r1 The phase shift matrix is ​​used to calculate the UAV's flight altitude H1 under the current conditions;

[0076] Until |H-H1|≤10 -5 At this point, the optimal flight altitude for the drone is obtained.

[0077] It should be noted that solving for the UAV altitude using the optimal expression for the UAV avoids the excessive computation time problem caused by conventional one-dimensional search when the number of reflection and transmission units in STAR-RIS is large, thereby maximizing system performance. Therefore, this metric is a decisive one.

[0078] Example 2

[0079] Reference Figure 3 As an embodiment of the present invention, an optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication is provided. To verify its beneficial effects, a comparison of two schemes is provided.

[0080] Figure 3This paper presents a comparison of the time complexity of the proposed method for designing the optimal drone altitude and the conventional one-dimensional search method for finding the optimal drone altitude. As the number of reflection and transmission elements in STAR-RIS increases, the dimension of the STAR-RIS phase shift matrix also increases, leading to a sharp increase in the number of calculations when using a one-dimensional search to find the optimal drone altitude. However, using the proposed method for designing the optimal drone altitude, the computational complexity remains low regardless of the increase in the number of reflection and transmission elements in STAR-RIS.

[0081] It should be noted that the above embodiments are only used to illustrate the technical solutions 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 solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for designing the optimal flight altitude for a UAV equipped with STAR-RIS assisted communication, characterized in that, Includes the following steps: Set the initial values ​​for the STAR-RIS reflection splitting coefficient, phase shift matrix, and UAV flight altitude; calculate the iterative expressions for the STAR-RIS reflection splitting coefficient and UAV flight altitude respectively; The flight altitude of the UAV under the current conditions is calculated using the calculated STAR-RIS reflection splitting coefficient and the iterative expression of the UAV flight altitude. Finally, determine whether the drone altitude has converged. If it has converged, the optimal flight altitude of the drone is obtained; if it has not converged, repeat the previous iterative steps until the convergence condition is met. The reflection splitting coefficient of STAR-RIS The iterative expression is represented as: In the formula, This indicates the total transmit power of the base station. This indicates the power that the base station allocates to ground users. This indicates the power allocated to the HAP by the base station; The reflection splitting coefficient of STAR-RIS In the iterative expression, , Represented as: in, and This represents the path loss and path loss factor per unit distance of 1m. For noise power at ground users and HAP, This refers to the number of reflective and transmissive units in STAR-RIS. and These represent the Rice factors of the base station-to-drone and drone-to-ground user channels, respectively. and These represent the distances from the base station to the drone and from the drone to the ground user, respectively. Indicates the distance from the drone to the HAP; The drone's flight altitude The iterative expression is: In the formula, Indicates the height of the HAP. Indicates the height of the base station; The drone's flight altitude In the iterative expression, , Represented as: 。 2. The optimal flight altitude design for UAV equipped with STAR-RIS assisted communication as described in claim 1 The method is characterized by: The specific steps for determining whether the drone altitude has converged are as follows: determine whether the following conditions are met. If this convergence condition is met, the optimal flight altitude for the drone is obtained; otherwise, let... , Recalculate the reflection splitting coefficient of STAR-RIS under the current conditions. And the phase shift matrix and calculation of the UAV's flight altitude under the current conditions. until satisfied At this point, the optimal flight altitude for the drone is obtained.

3. The optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication as described in claim 2, characterized in that: Using the calculated STAR-RIS reflection splitting coefficient, the phase shift matrix of STAR-RIS at this point is obtained, and the reflection phase shift matrix is ​​the optimal phase shift matrix. Represented as: In the formula, This represents the reflection splitting coefficient under the current conditions. Indicates the first Optimal reflection phase shift for each reflecting element; The optimal reflection phase shift of the reflective element is specifically expressed as follows: in, This indicates the adjacent spacing between reflecting and transmitting units. Indicates the wavelength of the incident wave. , These represent the departure angle of the base station relative to the drone and the arrival angle of the ground user relative to the drone, respectively.

4. The optimal flight altitude design method for UAV equipped with STAR-RIS assisted communication as described in claim 3, characterized in that: Using the calculated STAR-RIS reflection splitting coefficient, the phase shift matrix of STAR-RIS at this point is obtained, and the transmission phase shift matrix is ​​the optimal phase shift matrix. Represented as: In the formula, Indicates the first Optimal transmission phase shift for each transmission element; The optimal transmission phase shift of the transmission element is specifically expressed as follows: in, This represents the angle of arrival (HAP) relative to the drone.

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