A flight position design method of a UAV and active RIS assisted communication system
By integrating an active amplifier into the UAV and active RIS communication system, the flight position of the UAV is optimized, the problem of limited channel gain in wireless communication is solved, and higher frequency communication and higher ground user rates are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANJING UNIV OF POSTS & TELECOMM
- Filing Date
- 2023-03-17
- Publication Date
- 2026-07-03
Smart Images
Figure CN116390206B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wireless communication technology for unmanned aerial vehicles (UAVs) as aerial mobile base stations, and more particularly to a method for designing the flight position of a UAV and an active RIS-assisted communication system. Background Technology
[0002] In recent years, unmanned aerial vehicles (UAVs) and reconfigurable intelligent surfaces (RIS) have actively altered wireless communication channels through maneuver control and signal reconstruction, respectively, becoming two innovative technologies that promote the development of wireless communication networks. Simultaneously, with advancements in manufacturing technology and decreasing costs, the reliable, economical, and convenient characteristics of UAVs and RIS have provided more solutions to challenges in the field of wireless communication, showing broad application prospects in 5G and future 6G networks. While the introduction of RIS transforms the wireless communication environment from passive adaptation to active control, the "multiplicative effect" of the path loss in the RIS reflection link (which is the product of the path losses from the transmitter to the RIS and from the RIS to the receiver) means that the RIS reflection link can only provide very limited channel gain.
[0003] To address this issue, active RIS amplifies the reflected signal by integrating an active amplifier into the reflection unit, thereby enhancing the RIS's link control capabilities. Therefore, the combination of UAVs and active RIS will further provide channel gain for wireless communication, helping to overcome the increasing complexity of wireless channels and address key technologies for achieving higher frequency communication. Summary of the Invention
[0004] 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.
[0005] In view of the limited channel problem in the existing technology, the present invention is proposed.
[0006] Therefore, the purpose of this invention is to provide a flight position design method for UAVs and active RIS-assisted communication systems. The aim is to amplify reflected signals, enhance the link control capability of the RIS, and further provide channel gain for wireless communication when combined with an active RIS.
[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a flight position design method for an unmanned aerial vehicle (UAV) and an active RIS-assisted communication system, comprising the following steps: establishing a spatial rectangular coordinate system with the center of the active RIS as the origin and the plane where the active RIS is located as the yOz plane; setting the coordinates of the UAV as (x... q ,y q ,z q In a Cartesian coordinate system, the number M of reflective elements M covered by the UAV's directional antenna beam on the active RIS is calculated based on geometric positional relationships; the reception rate R of the ground user is calculated based on the number of reflective elements M; and based on the number of reflective elements M and the reception rate R, the three-dimensional coordinates (x, y, y) of the UAV are sequentially adjusted. q ,y q ,z q The calculation is performed; initial values are set, and the formula for calculating the three-dimensional coordinates of the UAV is iterated alternately. If convergence is achieved, the optimal position of the UAV is obtained. If convergence fails, recalculate the three-dimensional coordinates (x, y) of the UAV sequentially. q ,y q ,z q (This continues until convergence.)
[0008] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, the spatial rectangular coordinate system includes a downlink wireless communication system consisting of a UAV base station with a directional antenna, an active RIS deployed on a large scale on the exterior surface of a building, and ground users; the directional antenna of the UAV is always oriented towards the center of the active RIS, and the signal is reflected to the ground users through the active RIS.
[0009] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, the calculation expression for the number M of reflective elements covered by the UAV directional antenna beam on the active RIS is:
[0010]
[0011] Where λ represents the uniform distribution density of the reflective cells on the active RIS, (x q ,y q ,z q ) represents the coordinates of the UAV in a Cartesian coordinate system, and ξ represents the beamwidth of the directional antenna equipped on the UAV.
[0012] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, the calculation expression for the ground user receiving rate R is:
[0013]
[0014] Among them, P t Here, ρ represents the transmitted signal power, G represents the gain of the directional antenna, and ρ0 represents the path loss at a reference distance of 1 meter. d1 represents the distance from the UAV to the active RIS center, d2 represents the distance from the ground user to the active RIS center, α represents the path loss exponential factor, M represents the number of reflective units calculated in step 1, and P represents the distance from the UAV to the active RIS center. RIS P represents the total power consumption limit of the active RIS. c P represents the power consumption of each reflective unit switch and control circuit on an active RIS. DC This represents the power consumption of each reflective amplifier on the active RIS under DC bias. This represents the amplified noise power of each reflector unit on the active RIS. This represents the variance of Gaussian white noise in a wireless channel.
[0015] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, wherein: the UAV's three-dimensional coordinates (x... q ,y q ,z q ) in x q The calculation steps are as follows:
[0016] Establish the equation x q =g1(x q ), where g1(x q The specific expression for ) is:
[0017]
[0018] The equations for calculating A and B are as follows:
[0019]
[0020]
[0021] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, wherein: initial values are set t1 = 1, according to the equation x q =g1(x q Iterative calculation t1 = t1 + 1, until The iteration stops when ε is the set convergence threshold; finally, we obtain...
[0022] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, wherein: the UAV's three-dimensional coordinates (x... q ,y q ,z q ) in y q The calculation steps are as follows:
[0023] Establish equation y q =g2(y q ), where g2(y q The specific expression for ) is:
[0024]
[0025] The equation for calculating C is as follows:
[0026]
[0027] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system of the present invention, wherein: initial values are set t2 = 1, according to the equation y q =g2(y q Iterative calculation t2 = t2 + 1, until The iteration stops when ε is the set convergence threshold; finally, we obtain...
[0028] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, wherein: the UAV's three-dimensional coordinates (x... q ,y q ,z q ) in z q The calculation steps are as follows:
[0029] Establish equation z q =g3(z q ), where g3(z q The specific expression for ) is:
[0030]
[0031] Wherein, D is calculated by the following equation:
[0032]
[0033] As a preferred embodiment of the flight position design method for the UAV and active RIS-assisted communication system described in this invention, wherein: initial values are set t3 = 1, according to the equation z q=g3(z q Iterative calculation t3 = t3 + 1, until The iteration stops when ε is the set convergence threshold; finally, we obtain...
[0034] The beneficial effects of this invention are as follows: by integrating an active amplifier into the reflection unit, the reflected signal is amplified, thereby enhancing the link control capability of the RIS. The combination with the active RIS will further provide channel gain for wireless communication, which is beneficial for overcoming the increasing complexity of wireless channels and realizing higher frequency wireless communication. Attached Figure Description
[0035] 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:
[0036] Figure 1 This is a flowchart of an embodiment of the flight position design method for the UAV and the active RIS-assisted communication system of the present invention;
[0037] Figure 2 This is a schematic diagram of the UAV and active RIS-assisted communication system model of the present invention;
[0038] Figure 3 This is a simulation diagram illustrating the flight position design method of the UAV and active RIS-assisted communication system of the present invention. Detailed Implementation
[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0040] 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.
[0041] 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.
[0042] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.
[0043] Example 1
[0044] Reference Figure 1 and Figure 2 This is the first embodiment of the present invention, providing a flight position design method in an unmanned aerial vehicle (UAV) and an active RIS-assisted wireless communication system, comprising the following steps: First, establishing a spatial rectangular coordinate system with the center of the active RIS as the origin and the plane containing the active RIS as the yOz plane, and setting the coordinates of the UAV as (x... q ,y q ,z q In a Cartesian coordinate system, the number M of reflective elements M covered by the UAV's directional antenna beam on the active RIS is calculated based on geometric positional relationships. Then, the reception rate R for ground users is calculated based on the number of reflective elements M. Next, based on the number of reflective elements M and the reception rate R, the three-dimensional coordinates (x, y, y) of the UAV are sequentially adjusted. q ,y q ,z q The calculation is performed; finally, the formula for calculating the three-dimensional coordinates of the UAV is iterated alternately until the iteration converges, at which point the optimal position of the UAV is obtained.
[0045] This invention takes into account the changes in the number of RIS reflector units in the signal beam coverage area caused by the UAV's flight position. Under the condition that the active RIS has power limitations, the flight position design method proposed in this invention can effectively reduce computational complexity and improve the reachability of ground users, and has good practicality.
[0046] The present invention will now be described in further detail with reference to the accompanying drawings.
[0047] like Figure 1 As shown, this invention is a flight position design method in a UAV and active RIS-assisted wireless communication system. First, a downlink wireless communication system is constructed, consisting of a UAV base station equipped with a directional antenna, a large-scale deployment of active RIS systems on the exterior surfaces of buildings, and ground users. The directional antenna of the UAV is always oriented towards the center of the active RIS system, thereby avoiding beam loss from the directional antenna and fully utilizing the beamforming capability of the active RIS system. Signals are reflected to ground users through the active RIS system, such as... Figure 2 As shown, the drone flight position design includes the following steps:
[0048] S1: Establish a spatial rectangular coordinate system with the center of the active RIS as the origin and the plane containing the active RIS as the yOz plane. Assume the coordinates of the UAV are (x... q ,y q ,z q In a spatial rectangular coordinate system, the number M of reflective elements covered by the UAV directional antenna beam on the active RIS is calculated based on the geometric positional relationship.
[0049] The expression for calculating the number of reflecting elements M covered by the UAV directional antenna beam on the active RIS is:
[0050]
[0051] Where λ represents the uniform distribution density of the reflective cells on the active RIS, (x q ,y q ,z q ) represents the coordinates of the UAV in a Cartesian coordinate system, and ξ represents the beamwidth of the directional antenna equipped on the UAV.
[0052] S2: Calculate the receiving rate R of the ground user based on the number of reflecting units M in step 1;
[0053] The expression for calculating the terrestrial user reception rate R is:
[0054]
[0055] Among them, P t Here, ρ represents the transmitted signal power, G represents the gain of the directional antenna, and ρ0 represents the path loss at a reference distance of 1 meter. d1 represents the distance from the UAV to the active RIS center, d2 represents the distance from the ground user to the active RIS center, α represents the path loss exponential factor, M represents the number of reflective units calculated in step 1, and P represents the distance from the UAV to the active RIS center. RIS P represents the total power consumption limit of the active RIS. c P represents the power consumption of each reflective unit switch and control circuit on an active RIS. DC This represents the power consumption of each reflective amplifier on the active RIS under DC bias. This represents the amplified noise power of each reflector unit on the active RIS. This represents the variance of Gaussian white noise in a wireless channel.
[0056] S3: Based on the number of reflecting units M in step 1 and the receiving rate R in step 2, sequentially adjust the three-dimensional coordinates (x, y) of the UAV. q ,y q ,z q Perform calculations;
[0057] UAV three-dimensional coordinates (x)q ,y q ,z q ) in x q The calculation steps are as follows:
[0058] Step 3.1 Establish the equation x q =g1(x q ), where g1(x q The specific expression for ) is:
[0059]
[0060] A and B are calculated using the following equations:
[0061]
[0062]
[0063] S3.2 Set initial values t1 = 1, according to the equation x q =g1(x q Iterative calculation t1 = t1 + 1, until The iteration stops when ε is the set convergence threshold; finally, we obtain...
[0064] UAV three-dimensional coordinates (x) q ,y q ,z q ) in y q The calculation steps are as follows:
[0065] Step 3.3 Establish the equation y q =g2(y q ), where g2(y q The specific expression for ) is:
[0066]
[0067] Wherein, C is calculated by the following equation:
[0068]
[0069] S3.4 Set initial values t2 = 1, according to the equation y q =g2(y q Iterative calculation t2 = t2 + 1, until The iteration stops when ε is the set convergence threshold; finally, we obtain...
[0070] UAV three-dimensional coordinates (x) q ,y q ,z q ) in z q The calculation steps are as follows:
[0071] S3.5 Establish equation z q =g3(z q ), where g3(z q The specific expression for ) is:
[0072]
[0073] Wherein, D is calculated by the following equation:
[0074]
[0075] S3.6 Setting Initial Values t3 = 1, according to the equation z q =g3(z q Iterative calculation t3 = t3 + 1, until The iteration stops when ε is the set convergence threshold; finally, we obtain...
[0076] S4: Set initial values, and iterate the formula for calculating the UAV's 3D coordinates in step 3 alternately. If convergence occurs, the optimal position of the UAV is obtained. If convergence fails, repeat step 3 to recalculate the UAV's three-dimensional coordinates (x, y, y) sequentially. q ,y q ,z q (This continues until convergence.)
[0077] Finally, based on the optimal flight position, the UAV, acting as an airborne base station, transmits data to ground users with the assistance of RIS, thus completing the communication task.
[0078] Example 2
[0079] Reference Figure 3 This is the second embodiment of the present invention, which differs from the first embodiment in that:
[0080] Simulation experiments were conducted using MATLAB to verify the feasibility of the invention. The simulation results are as follows: Figure 3 As shown.
[0081] Figure 3The simulation results show a comparison of the reachability rates of ground users when the UAV is in different flight positions. As can be seen from the simulation figures, the optimal flight position calculated by the method of this invention is in good agreement with the optimal flight position obtained by the brute-force search method. The brute-force search method, also known as the exhaustive search method, lists all possible scenarios until the most accurate position is obtained, but it has high computational complexity and is time-consuming. Table 1 shows that the three-dimensional coordinates obtained by the method of this invention for calculating the UAV flight position are very close to those of the brute-force search method, demonstrating high accuracy and a short algorithm runtime. The method proposed in this invention can effectively reduce computational complexity. Simulations also demonstrate the impact of the UAV flight position on the reachability rate of ground users, showing that the reachability rate of ground users is maximized at the optimal flight position.
[0082] Table 1 shows the running results and timelines of the proposed method and the brute-force search method.
[0083] Algorithm Comparison Algorithm results (optimal 3D position of the UAV) Running time (s) The method proposed in this invention (85.1567,20.9998,21.9998) 1.0675s Brute-force search method (85.30,20.80,21.75) 1001.6137s
[0084] It is important to note that the constructions and arrangements of this application shown in several different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., changes in the size, dimensions, structure, shape, and proportions of various elements, as well as parameter values (e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of elements may be inverted or otherwise altered, and the nature or number or position of discrete elements may be changed or altered. Therefore, all such modifications are intended to be included within the scope of the invention. The order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the present invention is not limited to the specific embodiments, but extends to various modifications that still fall within the scope of the appended claims.
[0085] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the currently considered best mode for carrying out the invention, or those features that are not relevant to implementing the invention) may be omitted.
[0086] 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 flight positions for an unmanned aerial vehicle (UAV) and an active RIS-assisted communication system, characterized in that: include, A spatial rectangular coordinate system is established with the center of the active RIS as the origin and the plane containing the active RIS as the yOz plane; Set the drone's coordinates as The number of reflective elements covered by the UAV directional antenna beam on the active RIS is calculated based on the geometric positional relationships in a spatial rectangular coordinate system. ; Based on the number of reflective units Calculate the receiving rate of ground users ; Based on the number of reflective units and receiving rate The three-dimensional coordinates of the UAV were then sequentially... Perform calculations; Set initial values, and iterate the formula for calculating the UAV's three-dimensional coordinates alternately. If the receiving rate... If convergence occurs, the optimal position of the UAV is obtained. If the receiving rate If the convergence fails, recalculate the three-dimensional coordinates of the UAV sequentially. until convergence; The spatial rectangular coordinate system includes a downlink wireless communication system consisting of a drone base station with a directional antenna, an active RIS deployed on a large scale on the exterior surface of a building, and ground users; the directional antenna of the drone is always oriented towards the center of the active RIS, and the signal is reflected to the ground users through the active RIS; The number of reflective elements covered by the drone's directional antenna beam on the active RIS is [number missing]. The calculation expression is: in, This represents the uniform distribution density of reflective cells on an active RIS. This represents the coordinates of the UAV in a Cartesian coordinate system. This indicates the beamwidth of the directional antenna on the drone. The ground user reception rate The calculation expression is: in, Indicates the signal transmission power. This indicates the gain of the directional antenna. This represents the path loss at a reference distance of 1 meter. This indicates the distance from the drone to the active RIS center. This indicates the distance from the ground user to the active RIS center. An exponential factor representing path loss. Indicates the number of reflective units. This indicates the total power consumption limit of the active RIS. This represents the power consumption of each reflective unit switch and control circuit on an active RIS. This represents the power consumption of each reflective amplifier on the active RIS under DC bias. This represents the amplified noise power of each reflector unit on the active RIS. This represents the variance of Gaussian white noise in a wireless channel.
2. The flight position design method for the UAV and active RIS-assisted communication system according to claim 1, characterized in that: The three-dimensional coordinates of the UAV middle The calculation steps are as follows: Establish equations ,in The specific expression: in, and The calculation equation is as follows: 。 3. The flight position design method for the UAV and active RIS-assisted communication system according to claim 2, characterized in that: judge The steps to determine if the receiving rate converges are: setting an initial value. , According to the equation Iterative computation , ,until Stop iterating when the time comes, and get ,in The threshold for setting the convergence decision.
4. The flight position design method for the UAV and active RIS-assisted communication system according to claim 3, characterized in that: The three-dimensional coordinates of the UAV middle The calculation steps are as follows: Establish equations ,in The specific expression is: in, The calculation equation is as follows: 。 5. The flight position design method for the UAV and active RIS-assisted communication system according to claim 4, characterized in that: judge The steps to determine if the receiving rate converges are: setting an initial value. , According to the equation Iterative computation , ,until Stop iterating when the time comes, and get ,in The threshold for setting the convergence decision.
6. The flight position design method for the UAV and active RIS-assisted communication system according to claim 5, characterized in that: The three-dimensional coordinates of the UAV middle The calculation steps are as follows: Establish equations ,in The specific expression is: in, It is calculated from the following equation: 。 7. The flight position design method for the UAV and active RIS-assisted communication system according to claim 6, characterized in that: judge The steps to determine if the receiving rate converges are: setting an initial value. , According to the equation Iterative computation , ,until Stop iterating when the time comes, and get ,in The threshold for setting the convergence decision.