CN113949474B

CN113949474B - Unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance

Info

Publication number: CN113949474B
Application number: CN202111135455.0A
Authority: CN
Inventors: 练柱先; 苏胤杰; 王亚军; 靳标; 张贞凯
Original assignee: Jiangsu University of Science and Technology
Current assignee: Jiangsu University of Science and Technology
Priority date: 2021-09-27
Filing date: 2021-09-27
Publication date: 2023-08-22
Anticipated expiration: 2041-09-27
Also published as: CN113949474A

Abstract

The invention discloses an unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance, which comprises the steps of building an unmanned aerial vehicle geometric model based on intelligent reflecting surface assistance according to the position relation among an unmanned aerial vehicle, an intelligent reflecting surface and a receiving end, and obtaining complex channel gain of a channel; according to the geometric model of the unmanned aerial vehicle, the optimization problem is designed according to the received signal power maximization principle; simplifying and optimizing problems; solving the optimal reflection phase of the intelligent reflection surface; determining time-varying parameters among the unmanned aerial vehicle, the user side and the intelligent reflecting surface; and solving a space-time correlation function based on the assistance of the intelligent reflection surface through the obtained reflection phase and time-varying parameters, and determining the influence of the intelligent reflection on the unmanned aerial vehicle channel characteristic through correlation analysis. The communication system adopting the intelligent reflecting surface can obviously improve the receiving power of the signal and reduce the multipath fading phenomenon of the received signal, and the model building method can provide powerful support for exploring key technologies of the 6G communication system.

Description

Unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance

Technical Field

The invention relates to a wireless communication technology, in particular to an unmanned aerial vehicle geometric model building method based on intelligent reflection surface assistance.

Background

In recent years, with the rapid development of unmanned aerial vehicle manufacturing technology, unmanned aerial vehicles play a vital role in pesticide spraying, express delivery transportation, disaster relief, rescue and the like. The high flexibility and deployment cost cheapness of unmanned aerial vehicles, which act as airborne mobile base stations or relay mobile base stations in wireless communications, has attracted widespread attention in industry and academia. Notably, the propagation environment between the drone and the client is not controllable, affecting the system performance of the drone communication system. The intelligent reflection surface IRS is composed of units with adjustable amplitude, phase and frequency, and can control the propagation environment between a transmitting end and a receiving end. The literature already shows that: by adjusting the reflection phase of the intelligent reflection surface IRS, the power of the received signal can be improved, and the multipath fading phenomenon can be eliminated. As an emerging technology, the challenge is to study the application of intelligent reflector IRSs in unmanned aerial vehicle communication systems. Accurate channel modeling can provide basis for future system performance analysis and precoding algorithm design.

In the disclosure of the prior art, the capability of the intelligent reflection surface IRS to eliminate the doppler effect and multipath fading is studied somewhat, but because of the high-speed movement characteristic of the UAV, the UAV channel of the UAV is a non-stable process, so that the technology cannot be directly applied to the UAV communication scene. Some consider the effect of the drone path on the performance of the reconstructed intelligent surface assisted drone communication system, but this technique ignores the consideration of the sum of the number of intelligent reflection units. There are also three-dimensional geometric channel models of non-stationary 6G communication systems that use intelligent reflection surface IRS to control the propagation environment between the transceivers and assume that the reflection phase is determined by the propagation distance between the transceivers, but the technique ignores the effect of time-varying doppler shift on the channel statistics. There have also been some studies on a wideband non-stationary random channel model of an intelligent reflection-aided MIMO communication system, which considers the effect of intelligent reflection on channel statistics, but which ignores the consideration of the reflection phase of the intelligent reflection unit.

In summary, unmanned aerial vehicle UAV channel modeling based on intelligent reflection surface IRS assistance is in an initial stage, and statistical characteristics of the intelligent reflection surface IRS on the unmanned aerial vehicle UAV channel are yet to be explored, so that accurate unmanned aerial vehicle UAV channel modeling based on intelligent reflection surface IRS assistance is very necessary.

Disclosure of Invention

The invention aims to: the invention aims to provide an accurate unmanned aerial vehicle modeling method based on reflection surface assistance, and the establishment of the model can provide basis for future system performance analysis and precoding algorithm design.

The technical scheme is as follows: the invention discloses an unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance, which comprises the following steps:

s1, establishing an unmanned aerial vehicle geometric model based on the assistance of an intelligent reflection surface IRS according to the position relation among an unmanned aerial vehicle UAV, the intelligent reflection surface IRS and a receiving end, and obtaining the complex channel gain of a channel;

s2, designing an optimization problem according to an unmanned aerial vehicle geometric model based on intelligent reflection surface IRS assistance and a received signal power maximization principle;

s3, mainly concentrating the power of the received signal on a direct component reflected by the intelligent reflection surface IRS, so as to simplify the problem of optimization;

s4, solving the optimal IRS reflection phase of the intelligent reflection surface according to the simplified optimization problem;

s5, determining time-varying parameters among the unmanned aerial vehicle, the user and the intelligent reflection surface IRS;

s6, obtaining time-varying reflection phases, time-varying distances and time-varying Doppler frequency shifts in the step S4 and the step S5, solving a space-time correlation function assisted by the intelligent reflection surface IRS, and determining the influence of the intelligent reflection surface IRS on the unmanned aerial vehicle channel characteristics through correlation analysis.

Further, the complex channel gain based on the intelligent reflection surface-aided geometric model in step S1 is expressed as follows:

wherein,

wherein t represents a time variable, h _pq (t) represents an unmanned aerial vehicle UAV antenna unit p and a user antenna unit qComplex channel gain of the multipath component between,complex channel gain representing direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, +.>Complex channel gain representing scattering component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, +.>Representing complex channel gain of direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q after being reflected by intelligent reflection surface IRS, +.>Representing complex channel gain, theta, of scattering components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q scattered by intelligent reflection surface IRS and scatterer _mn (t) represents the reflection phase of the intelligent reflection surface IRS at the time t, G _t Indicating the gain of the transmitting antenna, G _r Indicating the gain of the receiving antenna, < >>Representing the path loss of the unmanned aerial vehicle UAV to the user, K representing the Lais factor, ++>Representing path loss from unmanned aerial vehicle UAV to intelligent reflection surface IRS, pi representing circumference rate, lambda representing carrier wavelength, and xi _pq (t) represents a time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, f _pq (t) time-varying Doppler shift, N, representing direct components between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q ₁ Representing scatterer->Number of->Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance, ζ between _n1q (t) represents scatterers->And the time-varying distance between the subscriber-side antenna elements q,/->Representing a scattered body->Time-varying doppler shift, ζ, of the scattering component of (a) _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift, N, of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, N) -th intelligent reflection unit ₂ Representing scatterer->Number of->Representing (m, n) -th smart reflective units and scatterersTime-varying distance between->Representing scatterer->And a subscriber antenna unitTime-varying distance between elements q +.>Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q through intelligent reflection surface IRS and scattererThe time-varying doppler shift after that.

Further, the optimization problem in step S2 is expressed as follows:

wherein t represents a time variable, θ _mn (t) the reflection phase of the intelligent reflection surface IRS at time t,represents statistical mean operation, h _pq (t) represents the complex channel gain of the link between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q.

Further, step S3 includes the steps of:

s31, considering the received signal power in the comparison set, simplifying the optimization problem of the step S2, wherein the simplified formula is as follows:

wherein,

wherein, representing statistical mean operation, t representing time variable, < ->And->Representing the auxiliary variables, cos (·) representing the cosine function,>representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, +.>Indicating the multipath component path between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via (m, n) -th intelligenceTime-varying phase after reflection unit, N ₁ Representing scatterer->Number of->Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via scatterers +.>Later time-varying phase,/->Representing the time-varying phase of multipath components between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q after passing through (M ', N') -th intelligent reflection units, M representing the number of intelligent reflection surface IRS row reflection units, N representing the number of intelligent reflection surface IRS column reflection units, pi representing the circumference ratio, lambda representing the carrier wavelength, and xi _pq (t) represents a time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, f _pq (t) time-varying Doppler shift representing direct components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, < >>Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between->Representing scatterersAnd the time-varying distance between the subscriber-side antenna elements q,/->Indicating no presence ofTime-varying doppler shift, ζ, of the scattering component between the man-machine UAV antenna unit p and the user antenna unit q _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift, θ, of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, n) -th intelligent reflection unit _mn (t) represents the time-varying reflection phase of the (m, n) -th smart reflection unit, G _t Indicating the gain of the transmitting antenna, G _r Indicating the gain of the receiving antenna, < >>Representing the path loss of the unmanned aerial vehicle UAV to the user, K representing the Lais factor, ++>Representing path loss, delta, of unmanned aerial vehicle UAV to intelligent reflective surface IRS _M Representing the spacing, delta, between adjacent antennas of a row of reflecting elements _N Representing the antenna spacing adjacent to the column reflection unit;

s32, presuming the auxiliary variable isAnd->Wherein->And assuming that the time-varying reflection phase of the smart reflective surface is +.>The optimization problem is further simplified as follows:

wherein, and->All represent auxiliary variables.

Further, the optimal intelligent reflection surface IRS reflection phase θ obtained in step S4 _mn (t) is represented by the following formula:

wherein,

wherein pi represents the circumference ratio, lambda represents the carrier wavelength, t represents the time variable, and ζ _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, n) -th intelligent reflection unit,representing the auxiliary variables, sgn (·) representing the sign function, arctan (·) representing the arctangent function, χ _A Represent the auxiliary variable χ _B Representing auxiliary variables +.>Representing the auxiliary variables, cos (·) representing the cosine function,>representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, sin (·) representing a sine function, +.>Representing auxiliary variables +. >Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via scatterers +.>Later time-varying phase,/->Representing scatterer->Azimuth angle of->Representing scatterer->Is>Representing azimuthal probability density function, +.>Representing the elevation probability density function.

Further, step S5 includes the steps of:

s51, solving UAV antenna unit p of unmanned aerial vehicleTime-varying distance ζ of user side antenna element q _pq (t) the calculation formula is as follows:

ξ _pq (t)＝||d _pq (t)|| (6)；

wherein,

v _R ＝v _R [cosγ _R ,sinγ _R ,0]；

wherein, I represent the norm calculation is performed such that, t represents a time variable, ζ _pq (t) represents the time-varying distance, d, between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q _pq (t) represents a time-varying distance vector between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q,position vector, N representing unmanned aerial vehicle UAV antenna unit p _T Represents the number of unmanned aerial vehicle UAV antenna units, p represents the unmanned aerial vehicle UAV antenna unit position index, delta _T Representing the distance, θ, between adjacent antenna units of an unmanned aerial vehicle UAV _T Representing unmanned aerial vehicle UAV antenna unit direction, sin (·) representing sine function, cos (·) representing cosine function, tan (·) representing tangent function, ζ _TR Representing horizontal distance, θ, between unmanned aerial vehicle UAV and user _TR Representing the direction of the unmanned aerial vehicle UAV antenna unit relative to the user, beta _TR Representing elevation angle of unmanned aerial vehicle UAV antenna unit relative to user，/>Position vector, N, representing user side antenna element q _R Representing the number of antenna elements at the user end, q representing the index of the position of the antenna elements at the user end, delta _R Represents the spacing of adjacent antenna units at the user end, theta _R Indicating the direction of the antenna unit at the user end, v _T Representing unmanned aerial vehicle UAV velocity vector, v _R Representing the velocity vector of the user terminal, v _T Representing unmanned aerial vehicle UAV speed size, +.>Representing the elevation angle of the UAV movement direction of the unmanned aerial vehicle, gamma _T Representing the azimuth angle of the movement direction of the UAV of the unmanned aerial vehicle, v _R Indicating the speed of user terminal and gamma _R Representing the azimuth angle of the movement direction of the user side;

solving time-varying Doppler shift f of direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q _pq (t) the calculation formula is as follows:

wherein λ represents a carrier wavelength;

s52, solving the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q to be respectively to the scatterersTime-varying distance of (2)And->The calculation formula is as follows:

wherein,

wherein, representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance vector between- >Representing scatterer->And a time-varying distance vector between the subscriber-side antenna elements q,>representing user side to diffuser->Horizontal distance of>Representing scatterer->Azimuth angle of->Representing scatterer->Is a normal angle of elevation of (2);

solving time-varying Doppler shift of scattering components between unmanned aerial vehicle UAV antenna unit p and user antenna unit qThe calculation formula is as follows:

wherein λ represents a carrier wavelength;

s53, solving time-varying distance xi of unmanned aerial vehicle UAV antenna unit p, user antenna unit q and (m, n) -th intelligent reflecting unit respectively _pmn (t) and ζ _mnq (t) the calculation formula is as follows:

ξ _pmn (t)＝||d _pmn (t)|| (11)；

ξ _mnq (t)＝||d _mnq (t)|| (12)；

wherein,

wherein, xi _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance, d, between the (m, n) -th smart reflection unit and the user antenna unit q _pmn (t) represents a time-varying distance vector between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit, d _mnq (t) represents a time-varying distance vector between the (m, n) -th smart reflection unit reflection and the client antenna unit q,representing the position vector of the (M, n) -th intelligent reflection unit, M represents the number of the row reflection units of the intelligent reflection surface, M represents the row position index of the intelligent reflection unit, delta _M Representing the spacing, θ, between adjacent row reflective units of an intelligent reflective surface IRS _IRS Indicating the arrangement direction of the intelligent reflection surface IRS, N indicating the number of the column reflection units of the intelligent reflection surface, N indicating the column position index of the intelligent reflection units, delta _N Representing the distance, ζ, between adjacent columns of reflecting units of the intelligent reflecting surface _IRSR Representing the horizontal distance between the intelligent reflecting surface and the user side;

solving time-varying Doppler frequency shift f of multipath component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q after passing through (m, n) -th intelligent reflection unit _pqmn (t) the calculation formula is as follows:

s54, solving the scattererAnd the time-varying distance +.>The calculation formula is as follows:

wherein,

wherein, representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing a scattered body->And a time-varying distance vector between the subscriber-side antenna elements q,>representing user side to diffuser->Horizontal distance of>Representing scatterer->Azimuth angle of->Representing scatterer->Is a normal angle of elevation of (2);

solving multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q through intelligent reflection surface IRS and scattererPost-time-varying Doppler shift ∈>The calculation formula is as follows:

further, step S6 includes the steps of:

S61, solving a space-time correlation function of an unmanned aerial vehicle geometric channel assisted by an intelligent reflection surface IRS by using the time-varying parameters obtained in the step S3 and the step S4, wherein the calculation formula is as follows:

wherein:

wherein, space-time correlation representing direct component between unmanned aerial vehicle UAV antenna unit and user antenna unit, +.>Space-time correlation of scattering components between unmanned aerial vehicle UAV antenna unit and user antenna unit is represented,/->Representing the space-time correlation of direct components between an unmanned aerial vehicle UAV antenna unit and a user antenna unit, reflected by an intelligent reflection surface IRS, +.>Representing intelligent reflection surface IRS and scatterer between UAV antenna unit and user antenna unit>The temporal correlation of the reflected scattering component, t, represents the time variable, δ _T Representing antenna spacing, delta, between unmanned aerial vehicle UAV antenna units _R Represents the antenna spacing between the antenna units of the user terminal, τ represents the propagation delay, and K is the tableThe Curie factor, lambda represents the carrier wavelength, pi represents the circumference ratio, and 3.14, xi are taken _pq (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q _p′q′ (t+τ) represents the time-varying distance, f, between the unmanned aerial vehicle UAV antenna unit p' and the user antenna unit q _pq (t) time-varying Doppler shift representing direct components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, f _p′q′ (t+τ) represents the time-varying Doppler shift of the direct component direct link between the unmanned aerial vehicle UAV antenna unit p 'and the user antenna unit q', ∈ ->Representing unmanned aerial vehicle UAV antenna unit p and scattererTime-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing unmanned aerial vehicle UAV antenna unit p' and diffuser->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q'>Representing unmannedTime-varying Doppler shift of the scattering component between the aircraft UAV antenna unit p and the user antenna unit q, < >>Time-varying Doppler shift indicative of scattering components between unmanned aerial vehicle UAV antenna unit p' and user antenna unit q->Representing scatterer->Azimuth angle of->Representing scatterer->Is>Representing scatterer->Probability density function of azimuth angle +.>Representing scatterer->Probability density function, ζ, of elevation angle _pmn (t) represents the time-varying distance, ζ, of the link between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance, ζ, of the link between the (m, n) -th smart reflection unit and the user antenna unit q _p′mn (t+τ) represents the time-varying propagation distance, ζ, of the link between the unmanned aerial vehicle UAV antenna unit p' and the (m, n) -th smart reflection unit _mnq′ (t + tau) represents the time-varying propagation distance of the link between the (m, n) -th smart reflection unit and the subscriber-side antenna unit q',f _pqmn (t) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, n) -th intelligent reflection unit, f _p′q′mn (t+τ) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p 'and the user side antenna unit q' after (M, N) -th smart reflection units, N represents the number of column reflection units of the smart reflection surface IRS, N represents the column position index of the smart reflection units, M represents the number of row reflection units of the smart reflection surface IRS, M represents the row position index of the smart reflection units>Representing scatterer->And the time-varying propagation distance of the link between the subscriber side antenna elements q,representing scatterer->And the time-varying propagation distance of the link between the subscriber-side antenna unit q>Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via intelligent reflecting surface IRS and scatterer +.>Post time-varying Doppler shift, < >>Representing multipath components between unmanned aerial vehicle UAV antenna unit p 'and user antenna unit q' through intelligent reflecting surface IRS and scatterer +. >Time-varying Doppler frequency of reflected componentsRemove (L)>Representing scatterer->Is used in the azimuth angle of (2),representing scatterer->Is>Representing scatterer->Probability density function of azimuth angle +.>Representing scatterer->Exp (·) represents an exponential function, κ represents a scattering environment factor, μ represents an average angle of arrival of the scattering component, I ₀ Represents a zero-order Bessel function, |·| represents an absolute value function, β _max Representing the maximum elevation angle of the scatterer;

s62, determining the influence of the intelligent reflection surface IRS, the number of the intelligent reflection units and the size of the intelligent reflection units on the UAV channel statistical characteristics by using the obtained space-time correlation function.

The beneficial effects are that: compared with the prior art, the unmanned aerial vehicle geometric model based on the intelligent reflection surface assistance considers the influence of the intelligent reflection surface IRS on the unmanned aerial vehicle UAV channel characteristics, considers the optimal reflection phase under the received signal power maximization principle, and describes the unmanned aerial vehicle channel characteristics by adopting time-varying parameters; meanwhile, the influence of the number and the size of IRS reflecting units of the intelligent reflecting surface on the Doppler frequency shift and the multipath fading phenomenon of the unmanned aerial vehicle channel is considered; therefore, the invention can better explore the influence of the IRS of the intelligent reflecting surface on the statistical characteristics of the unmanned aerial vehicle channel.

Drawings

FIG. 1 is a schematic diagram of a geometric model of an unmanned aerial vehicle under the assistance of an intelligent reflection surface IRS;

FIG. 2 is a graph showing the comparison of absolute envelope amplitudes at different reflection phases of an intelligent reflection surface IRS;

FIG. 3 is a graph showing the comparison of absolute envelope magnitudes for different numbers of reflective units of an intelligent reflective surface IRS;

FIG. 4 is a graph showing the comparison of absolute envelope amplitudes for different reflective element geometries of an intelligent reflective surface IRS;

FIG. 5 is a graph comparing unmanned aerial vehicle channel spatial correlation functions for different numbers of intelligent reflection surface IRS reflection units;

fig. 6 is a graph comparing intelligent reflective surface IRS-assisted unmanned aerial vehicle channel time correlation functions at different unmanned aerial vehicle movement speeds.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.

According to the invention, the intelligent reflection surface IRS is adopted to control the propagation environment of the UAV channel of the unmanned aerial vehicle, the optimal received signal power is considered, and the optimal IRS reflection phase of the intelligent reflection surface is obtained. The invention considers the capability of the intelligent reflection surface IRS to change the unmanned aerial vehicle channel propagation environment, namely the influence of the number of the intelligent reflection surface IRS reflection units and the sizes of the reflection units on the unmanned aerial vehicle channel statistical characteristics. According to the invention, the unmanned aerial vehicle channel assisted by the intelligent reflection surface IRS is considered, the influence of the intelligent reflection surface IRS on the unmanned aerial vehicle channel statistical characteristic is explored, and the basis is better provided for system performance analysis and precoding algorithm design in the future.

The invention discloses an unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance, which comprises the following steps:

s1, establishing an unmanned aerial vehicle geometric model according to the position relation among an unmanned aerial vehicle UAV, an intelligent reflection surface IRS and a receiving end, and obtaining complex channel gain of a channel;

the invention considers the change of the intelligent reflection surface IRS to the channel propagation environment, and provides an unmanned aerial vehicle UAV channel model based on the assistance of the intelligent reflection surface IRS, wherein the complex gain of the channel is expressed as follows:

wherein,

wherein t represents a time variable, h _pq (t) represents the complex channel gain of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q,complex channel gain representing direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, +.>Complex channel gain representing scattering component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, +.>Representing complex channel gain of direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q after being reflected by intelligent reflection surface IRS, +.>Representing complex channel gain, theta, of scattering components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q scattered by intelligent reflection surface IRS and scatterer _mn (t) represents the reflection phase of the intelligent reflection surface IRS at the time t, G _t Indicating the gain of the transmitting antenna, G _r Indicating the gain of the receiving antenna, < >>Representing the path loss of the unmanned aerial vehicle UAV to the user, K representing the Lais factor, ++>Representing path loss from unmanned aerial vehicle UAV to intelligent reflection surface IRS, pi representing circumference rate, lambda representing carrier wavelength, and xi _pq (t) represents a time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, f _pq (t) time-varying Doppler shift, N, representing direct components between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q ₁ Representing scatterer->Number of->Representing unmanned aerial vehicle UAV antenna unit p and diffuser->The time-varying distance between the two,representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing a scattered body->Time-varying doppler shift, ζ, of the scattering component of (a) _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift, N, of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, N) -th intelligent reflection unit ₂ Representing scatterer->Number of->Representing (m, n) -th smart reflective units and scatterersTime-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing the intelligent inversion of multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit qPlane IRS and diffuser->The time-varying doppler shift after that.

S2, designing an optimization problem according to an unmanned aerial vehicle communication scene based on intelligent reflection surface IRS assistance and a received signal power maximization principle;

the invention considers the influence of the IRS of the intelligent reflecting surface on the unmanned aerial vehicle channel propagation environment, so the invention designs and optimizes the problem by taking the received signal power maximization as a principle. Wherein the optimization problem is expressed as follows:

S3, mainly concentrating the power of the received signal on a direct component reflected by the intelligent reflection surface IRS, so as to simplify the problem of optimization; specific:

s31, a received signal consists of a direct component, a scattered component, a direct component via the intelligent reflection surface IRS and a scattered component via the intelligent reflection surface, which leads to the complexity of solving the optimization problem. In order to reduce complexity, the invention considers the concentrated received signal power, and the optimization problem of simplification can be expressed as:

/>

Wherein,

wherein, representing statistical mean operation, t representing time variable, < ->And->Representing the auxiliary variables, cos (·) representing the cosine function,>representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, +.>Representing time-varying phase of direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q after (m, N) -th intelligent reflecting unit, N ₁ Representing scatterer->Number of->Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via scatterers +.>Later time-varying phase,/->Representing the time-varying phase of multipath components between an unmanned aerial vehicle UAV antenna unit p and a user antenna unit q after passing through an M 'th row and an N' th column intelligent reflecting units, M representing the number of intelligent reflecting surface IRS row reflecting units, N representing the number of intelligent reflecting surface IRS column reflecting units, pi representing the circumference ratio, taking 3.14, lambda representing the carrier wavelength, and xi _pq (t) represents a time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, f _pq (t) time-varying Doppler shift representing direct components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, < >>Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between- >Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Time-varying Doppler shift, ζ, representing a scattering component between an unmanned aerial vehicle UAV antenna unit p and a user antenna unit q _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift, θ, of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, n) -th intelligent reflection unit _mn (t) represents the time-varying reflection phase of the (m, n) -th smart reflection unit, G _t Indicating the gain of the transmitting antenna, G _r Indicating the gain of the receiving antenna, < >>Representing the path loss of the unmanned aerial vehicle UAV to the user, K representing the Lais factor, ++>Representing path loss, delta, of unmanned aerial vehicle UAV to intelligent reflective surface IRS _M Representing the spacing, delta, between adjacent antennas of a row of reflecting elements _N Representing the antenna spacing adjacent to the column reflecting element.

S32, assumption auxiliary variableAnd auxiliary variable +.>Wherein->And assuming that the time-varying reflection phase of the smart reflective surface is +.>The optimization problem is further simplified as follows:

wherein, representing the auxiliary variable.

S4, solving the optimization problem to obtain an optimal IRS reflection phase of the intelligent reflection surface;

The simplified optimization problem can be solved in a literature-existing manner, and the optimal IRS reflection phase of the intelligent reflection surface can be expressed by the following formula:

wherein,

wherein pi represents the circumference ratio, 3.14 is taken, lambda represents the carrier wavelength, t represents the time variable, and xi _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the multipath component path (m, n) -th between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit qTime-varying Doppler shift after the intelligent reflection unit, sgn (·) represents a sign function, arctan (·) represents an arctan function, χ _A Represent the auxiliary variable χ _B Represents the auxiliary variable(s),representing the auxiliary variables, cos (·) representing the cosine function,>representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, sin (·) representing a sine function, +.>Representing auxiliary variables +.>Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via scatterers +.>Later time-varying phase,/->Representing scatterer->Azimuth angle of->Representing scatterer->Is>Representing azimuthal probability density function, +. >Representing the elevation probability density function.

s51, solving time-varying azimuth angle and time-varying elevation angle parameters among a receiving end, an intelligent reflecting surface IRS and a scatterer, and solving time-varying distance xi from an unmanned aerial vehicle UAV antenna unit p to a user end antenna unit q _pq (t) the calculation formula is as follows:

ξ _pq (t)＝||d _pq (t)|| (6)；

wherein,

v _R ＝v _R [cosγ _R ,sinγ _R ,0]；

wherein, I represent the norm calculation is performed such that, t represents a time variable, ζ _pq (t) represents the time-varying distance, d, between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q _pq (t) represents a time-varying distance vector between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q,position vector, N representing unmanned aerial vehicle UAV antenna unit p _T Represents the number of unmanned aerial vehicle UAV antenna units, p represents the unmanned aerial vehicle UAV antenna unit position index, delta _T Representing the distance, θ, between adjacent antenna units of an unmanned aerial vehicle UAV _T Represents the unmanned aerial vehicle UAV antenna unit direction, tan (·) represents the tangent function, ζ _TR Representing horizontal distance, θ, between unmanned aerial vehicle UAV and user _TR Representing the direction of the unmanned aerial vehicle UAV antenna unit relative to the user, beta _TR Representing the elevation angle of the unmanned aerial vehicle UAV antenna unit relative to the user's end,position vector, N, representing user side antenna element q _R Representing the number of antenna elements at the user end, q representing the index of the position of the antenna elements at the user end, delta _R Represents the spacing of adjacent antenna units at the user end, theta _R Indicating the direction of the antenna unit at the user end, v _T Representing unmanned aerial vehicle UAV velocity vector, v _R Representing the velocity vector of the user terminal, v _T Representing unmanned aerial vehicle UAV speed size, +.>Representing the elevation angle of the UAV movement direction of the unmanned aerial vehicle, gamma _T Representing the azimuth angle of the movement direction of the UAV of the unmanned aerial vehicle, v _R Indicating the speed of user terminal and gamma _R Indicating the azimuth angle of the movement direction of the user side.

where λ represents the carrier wavelength.

wherein,

wherein, representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing unmanned aerial vehicle UAV antenna unit p and scattererTime-varying distance vector between->Representing scatterer->And a time-varying distance vector between the subscriber-side antenna elements q,>representing user side to diffuser- >Horizontal distance of>Representing scatterer->Azimuth angle of->Representing scatterer->Is>Position vector v representing user side antenna element q _R Representing the client velocity vector.

where λ represents the carrier wavelength.

S53, solving intelligent reflection units of unmanned aerial vehicle UAV antenna unit p, user antenna unit q and (m, n) -th respectivelyTime-varying distance ζ of (2) _pmn (t) and ζ _mnq (t) the calculation formula is as follows:

ξ _pmn (t)＝||d _pmn (t)|| (11)；

ξ _mnq (t)＝||d _mnq (t)|| (12)；

wherein,

wherein, xi _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance, d, between the (m, n) -th smart reflection unit and the user antenna unit q _pmn (t) represents a time-varying distance vector between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit, d _mnq (t) represents a time-varying distance vector between the (m, n) -th smart reflection unit reflection and the client antenna unit q,representing the position vector of the (M, n) -th intelligent reflection unit, M represents the number of the row reflection units of the intelligent reflection surface, M represents the row position index of the intelligent reflection unit, delta _M Representing the spacing, θ, between adjacent row reflective units of an intelligent reflective surface IRS _IRS Indicating the arrangement direction of the intelligent reflection surface IRS, N indicating the number of the column reflection units of the intelligent reflection surface, N indicating the column position index of the intelligent reflection units, delta _N Representing the distance, ζ, between adjacent columns of reflecting units of the intelligent reflecting surface _IRSR Representing the horizontal distance between the intelligent reflecting surface and the user side.

Solving unmanned aerial vehicle UAV antenna unit p and useTime-varying Doppler shift f after multipath component among user antenna units q passes through (m, n) -th intelligent reflecting unit _pqmn (t) the calculation formula is as follows:

wherein,

wherein, representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing a scattered body->And a time-varying distance vector between the subscriber-side antenna elements q,>representing user side to diffuser->Horizontal distance of>Representing scatterer->Azimuth angle of->Representing scatterer->Is a standard for a large number of different angles of elevation.

Solving for intelligent reflecting surfaces and scatterersDoppler shift of the scattered component>The calculation formula is as follows:

S61, solving an unmanned aerial vehicle geometric channel space-time correlation function assisted by an intelligent reflection surface IRS by utilizing the time-varying reflection phase, the time-varying azimuth angle parameter and the time-varying elevation angle parameter obtained in the step S4 and the step S5, wherein the calculation formula is as follows:

wherein:

/>

wherein, space-time correlation representing direct component between unmanned aerial vehicle UAV antenna unit and user antenna unit, +.>Space-time correlation of scattering components between unmanned aerial vehicle UAV antenna unit and user antenna unit is represented,/->Representing unmanned aerial vehicle UAV antenna unit and user antennaSpace-time correlation of direct components reflected by intelligent reflection surface IRS between line units, +.>Representing intelligent reflection surface IRS and scatterer between UAV antenna unit and user antenna unit>The temporal correlation of the reflected scattering component, t, represents the time variable, δ _T Representing antenna spacing, delta, between unmanned aerial vehicle UAV antenna units _R The antenna distance between the antenna units at the user end is represented by tau, the propagation delay is represented by K, the Lees factor is represented by lambda, the carrier wavelength is represented by pi, the circumference ratio is represented by 3.14, and xi _pq (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q _p′q′ (t+τ) represents the time-varying distance, f, between the unmanned aerial vehicle UAV antenna unit p' and the user antenna unit q _pq (t) time-varying Doppler shift representing direct components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, f _p′q′ (t+τ) represents the time-varying Doppler shift of the direct component direct link between the unmanned aerial vehicle UAV antenna unit p 'and the user antenna unit q', ∈ ->Representing unmanned aerial vehicle UAV antenna unit p and scattererTime-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->UAV antenna for representing unmanned aerial vehicleUnit p' and scatterer->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q'>Time-varying Doppler shift indicative of scattering components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, < >>Time-varying Doppler shift indicative of scattering components between unmanned aerial vehicle UAV antenna unit p' and user antenna unit q->Representing scatterer->Azimuth angle of->Representing scatterer->Is used for the control of the angle of elevation of (a),representing scatterer->Probability density function of azimuth angle +.>Representing scatterer->Probability density function, ζ, of elevation angle _pmn (t) represents the time-varying distance, ζ, of the link between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance, ζ, of the link between the (m, n) -th smart reflection unit and the user antenna unit q _p′mn (t+τ) represents the time-varying propagation distance, ζ, of the link between the unmanned aerial vehicle UAV antenna unit p' and the (m, n) -th smart reflection unit _mnq′ (t+τ) represents the time-varying propagation distance of the link between the (m, n) -th smart reflection unit and the user antenna unit q', f _pqmn (t) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, n) -th intelligent reflection unit, f _p′q′mn (t+τ) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p 'and the user side antenna unit q' after (M, N) -th smart reflection units, N represents the number of column reflection units of the smart reflection surface IRS, N represents the column position index of the smart reflection units, M represents the number of row reflection units of the smart reflection surface IRS, M represents the row position index of the smart reflection units>Representing scatterer->And the time-varying propagation distance of the link between the subscriber-side antenna units q,/->Representing scatterer->And the time-varying propagation distance of the link between the subscriber-side antenna unit q>UAV antenna list for representing unmanned aerial vehicleMultipath components between element p and user antenna element q pass through intelligent reflection surface IRS and scatterer +.>Post time-varying Doppler shift, < >>Representing multipath components between unmanned aerial vehicle UAV antenna unit p 'and user antenna unit q' through intelligent reflecting surface IRS and scatterer +. >Time-varying doppler shift of the reflected component,/->Representing scatterer->Azimuth angle of->Representing scatterer->Is>Representing scatterer->Probability density function of azimuth angle +.>Representing scatterer->Exp (·) represents an exponential function, κ represents a scattering environment factor, μ represents an average angle of arrival of the scattering component, I ₀ Representing zeroOrder Bessel function, |·| represents absolute value function, β _max Representing the maximum elevation angle of the diffuser.

Fig. 1 is a schematic diagram of a geometric model of an unmanned aerial vehicle under the assistance of an intelligent reflection surface IRS. In fig. 1, the invention uses three-dimensional ellipse-cylinder to simulate intelligent reflective surface IRS, unmanned aerial vehicle UAV and scatterers around the receiving end. The intelligent reflecting surface adopts a uniform plane reflecting array unit, the number of reflecting units in each row is assumed to be M, the number of reflecting units in each column is assumed to be N, and the intelligent reflecting surface IRS is assumed to be configured on the surface of a building, so that all users in the cell can be served. The height of the unmanned aerial vehicle UAV is obviously higher than that of a ground building, no building shielding exists between the unmanned aerial vehicle UAV and the intelligent reflection surface IRS, and a direct link is assumed between the unmanned aerial vehicle UAV and the intelligent reflection surface IRS.

Fig. 2 is a graph comparing absolute envelope amplitudes of a conventional unmanned aerial vehicle channel model and an unmanned aerial vehicle channel model based on intelligent reflection surface IRS assistance under different IRS reflection phases. In fig. 2, the time-varying phase of phase 1 of the IRS reflection unit is: θ _mn (t) =0; the time-varying phase of phase 2 of the IRS reflection unit is:wherein, xi _pmn (t) and ζ _mnq (t) time-varying distances between the unmanned aerial vehicle antenna unit and the user terminal antenna unit and the intelligent reflection unit, respectively; the time-varying phase of phase 3 of the IRS reflection unit is the optimal reflection phase proposed by the present invention. It can be seen from fig. 2 that the absolute envelope amplitude of the received signal can be obviously improved by adopting the intelligent reflection surface IRS, and meanwhile, the absolute envelope amplitude of the received signal can be enhanced by adjusting the time-varying phase of the intelligent reflection surface, so that it is verified that the model of the invention can effectively change the propagation environment between the unmanned aerial vehicle and the receiving end.

FIG. 3 shows the absolute numbers of different reflection units of the IRSThe graph is compared against the envelope magnitude. Fig. 4 is a graph showing the comparison of absolute envelope amplitudes at different reflective element geometries of the intelligent reflective surface IRS. It can be seen from fig. 3 and 4 that the number of smart reflection units and the geometrical area (delta) of the smart reflection units are increased _M δ _N ) The absolute envelope amplitude of the received signal can be significantly emphasized.

FIG. 5 is a graph comparing unmanned aerial vehicle channel spatial correlation functions for different numbers of intelligent reflection surface IRS reflection units; it can be seen from fig. 5 that the spatial correlation of the smart reflector IRS-assisted unmanned aerial vehicle channel model is related to the number of smart reflecting units. The initial value of the spatial correlation is reduced along with the increase of the intelligent reflection unit, and meanwhile, the non-stationary characteristic of the space of the intelligent reflection surface IRS-assisted unmanned aerial vehicle channel model is also displayed.

FIG. 6 is a graph comparing the correlation functions of the intelligent reflection surface IRS-assisted unmanned aerial vehicle channel time at different unmanned aerial vehicle movement speeds; from fig. 6, it can be seen that the time correlation function of the unmanned aerial vehicle channel is obviously enhanced after the intelligent reflection surface IRS is adopted.

In summary, the unmanned aerial vehicle geometric model building method based on the intelligent reflecting surface assistance comprises the following steps of: designing an optimization problem by taking the maximization of the received signal power as a target, and solving the optimization problem to obtain an optimal time-varying reflection phase; a time-varying distance parameter design step: obtaining a time-varying distance parameter and a time-varying Doppler frequency shift parameter among the unmanned aerial vehicle, the receiving end and the intelligent reflecting surface according to the geometrical model assisted by the intelligent reflecting surface; and a channel statistical characteristic analysis step: and analyzing the statistical characteristics of the unmanned aerial vehicle MIMO channel model based on the assistance of the intelligent reflecting surface according to the time-varying reflecting phase and the time-varying distance parameters of the intelligent reflecting surface. In the invention, the communication system adopting the intelligent reflecting surface can obviously improve the receiving power of the signal and reduce the multipath fading phenomenon of the received signal, so that the model building method can provide powerful support for exploring the key technology of the 6G communication system.

Claims

1. The unmanned aerial vehicle geometric model building method based on the intelligent reflecting surface assistance is characterized by comprising the following steps of:

the complex channel gain is expressed as follows:

wherein,

wherein t represents a time variable, h _pq (t) represents the complex channel gain of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q,complex channel gain representing direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, +.>Complex channel gain representing scattering component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q，/>Representing complex channel gain of direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q after being reflected by intelligent reflection surface IRS, +.>Representing complex channel gain, theta, of scattering components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q scattered by intelligent reflection surface IRS and scatterer _mn (t) represents the reflection phase of the intelligent reflection surface IRS at the time t, G _t Indicating the gain of the transmitting antenna, G _r Indicating the gain of the receiving antenna, < > >Representing the path loss of the unmanned aerial vehicle UAV to the user, K representing the Lais factor, ++>Representing path loss from unmanned aerial vehicle UAV to intelligent reflection surface IRS, pi representing circumference rate, lambda representing carrier wavelength, and xi _pq (t) represents a time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, f _pq (t) time-varying Doppler shift, N, representing direct components between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q ₁ Representing scatterer->Number of->Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing a scattered body->Time-varying doppler shift, ζ, of the scattering component of (a) _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift, N, of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, N) -th intelligent reflection unit ₂ Representing scatterer->Number of xi _mnn2 (t) represents (m, n) -th smart reflection unit and scattererTime-varying distance between->Representing scatterer- >And the time-varying distance between the subscriber-side antenna elements q,/->Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q through intelligent reflection surface IRS and scattererPost time-varying doppler shift;

2. The unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance according to claim 1, wherein the optimization problem in step S2 is expressed as follows:

wherein t represents a time variable, θ _mn (t) the reflection phase of the intelligent reflection surface IRS at time t,represents statistical mean operation, h _pq (t) represents the complex channel gain of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q.

3. The unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance according to claim 1, wherein the step S3 comprises the following steps:

s31, considering the received signal power in the comparison set, simplifying the optimization problem of the step S1, wherein the simplified formula is as follows:

wherein,

wherein, representing statistical mean operation, t representing time variable, < ->And->Representing the auxiliary variables, cos (·) representing the cosine function,>time-varying phase representing direct component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, +.>Representing the time-varying phase of the multipath component between unmanned aerial vehicle UAV antenna unit p and user antenna unit q after passing through (m, N) -th intelligent reflection unit, N ₁ Representing scatterer->Number of->Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via scatterers +.>Later time-varying phase,/->Representing the time-varying phase of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (M ', n') -th intelligent reflection unit, M representing the intelligent reflection surface IRS row The number of reflecting units, N represents the number of IRS column reflecting units of the intelligent reflecting surface, pi represents the circumference ratio, lambda represents the carrier wavelength, and xi _pq (t) represents a time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, f _pq (t) time-varying Doppler shift representing direct components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, < >>Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing a scattered body->Time-varying doppler shift, ζ, of the scattering component of (a) _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift, θ, of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, n) -th intelligent reflection unit _mn (t) represents the time-varying reflection phase of the (m, n) -th smart reflection unit, G _t Indicating the gain of the transmitting antenna, G _r Indicating the gain of the receiving antenna, < >>Representing the path loss of the unmanned aerial vehicle UAV to the user, K representing the Lais factor, ++>Representing path loss, delta, of unmanned aerial vehicle UAV to intelligent reflective surface IRS _M Representing the spacing, delta, between adjacent antennas of a row of reflecting elements _N Representing the antenna spacing adjacent to the column reflection unit;

wherein, and->All represent auxiliary variables.

4. The unmanned aerial vehicle geometric model establishment method based on intelligent reflection surface assistance according to claim 1, wherein the optimal intelligent reflection surface IRS reflection phase θ obtained in step S4 _mn (t) is made ofThe formula is:

wherein,

wherein pi represents the circumference ratio, lambda represents the carrier wavelength, t represents the time variable, and ζ _pmn (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance between the (m, n) -th smart reflection unit and the user antenna unit q, f _pqmn (t) represents the time-varying Doppler shift of the reflected component via the (m, n) -th smart reflection unit,representing the auxiliary variables, sgn (·) representing the sign function, arctan (·) representing the arctangent function, χ _A Represent the auxiliary variable χ _B Representing auxiliary variables +.>Representing the auxiliary variables, cos (·) representing the cosine function,>representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q, sin (·) representing a sine function, +. >Represents the auxiliary variable(s),representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via scatterers +.>Later time-varying phase,/->Representing scatterer->Azimuth angle of->Representing scatterer->Is>Representing azimuthal probability density function, +.>Representing the elevation probability density function.

5. The unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance according to claim 1, wherein the step S5 comprises the following steps:

s51, solving time-varying distance xi from unmanned aerial vehicle UAV antenna unit p to user antenna unit q _pq (t) the calculation formula is as follows:

ξ _pq (t)＝||d _pq (t)|| (6)；

wherein the method comprises the steps of

v _R ＝v _R [cosγ _R ,sinγ _R ,0]；

Wherein, I represent the norm calculation is performed such that, t represents a time variable, ζ _pq (t) represents the time-varying distance, d, between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q _pq (t) represents a time-varying distance vector between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q,position vector, N representing unmanned aerial vehicle UAV antenna unit p _T Represents the number of unmanned aerial vehicle UAV antenna units, p represents the unmanned aerial vehicle UAV antenna unit position index, delta _T Representing the distance, θ, between adjacent antenna units of an unmanned aerial vehicle UAV _T Representing unmanned aerial vehicle UAV antenna unit direction, sin (·) representing sine function, cos (·) representing cosine function, tan (·) representing tangent function, ζ _TR Representing horizontal distance, θ, between unmanned aerial vehicle UAV and user _TR Representing the direction of the unmanned aerial vehicle UAV antenna unit relative to the user, beta _TR Representing the elevation angle of the unmanned aerial vehicle UAV antenna unit relative to the user, < >>Position vector, N, representing user side antenna element q _R Representing the number of antenna elements at the user end, q representing the index of the position of the antenna elements at the user end, delta _R Represents the spacing of adjacent antenna units at the user end, theta _R Indicating the direction of the antenna unit at the user end, v _T Representing unmanned aerial vehicle UAV velocity vector, v _R Representing the velocity vector of the user terminal, v _T Representing unmanned aerial vehicle UAV speed size, +.>Representing the elevation angle of the UAV movement direction of the unmanned aerial vehicle, gamma _T Representing the azimuth angle of the movement direction of the UAV of the unmanned aerial vehicle, v _R Indicating the speed of user terminal and gamma _R Representing the azimuth angle of the movement direction of the user side;

wherein λ represents a carrier wavelength;

s52, solving the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q to be respectively to the scatterersTime-varying distance +.>And->The calculation formula is as follows:

wherein,

wherein, representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between- >Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance vector between->Representing scatterer->And a time-varying distance vector between the subscriber side antenna elements q,representing user side to diffuser->Horizontal distance of>Representing scatterer->Azimuth angle of->Representing scatterersIs a normal angle of elevation of (2);

via scatterersTime-varying Doppler shift of the scattered component->The calculation formula is as follows:

wherein λ represents a carrier wavelength;

ξ _pmn (t)＝||d _pmn (t)|| (11)；

ξ _mnq (t)＝||d _mnq (t)|| (12)；

wherein,

solving time-varying Doppler shift f of reflected component by (m, n) -th intelligent reflecting unit _pqmn (t) calculatingThe formula is as follows:

wherein,

6. the unmanned aerial vehicle geometric model building method based on intelligent reflecting surface assistance according to claim 1, wherein the step S6 comprises the following steps:

Wherein:

wherein, space-time correlation representing direct component between unmanned aerial vehicle UAV antenna unit and user antenna unit, +.>Space-time correlation representing scattering components between unmanned aerial vehicle UAV antenna unit and user antenna unit，/>Representing the space-time correlation of direct components between an unmanned aerial vehicle UAV antenna unit and a user antenna unit, reflected by an intelligent reflection surface IRS, +.>Representing intelligent reflection surface IRS and scatterer between UAV antenna unit and user antenna unit>The temporal correlation of the reflected scattering component, t, represents the time variable, δ _T Representing antenna spacing, delta, between unmanned aerial vehicle UAV antenna units _R Represents the antenna spacing between the antenna units at the user end, τ represents the propagation delay, K represents the Lees factor, λ represents the carrier wavelength, pi represents the circumference ratio, ζ _pq (t) represents the time-varying distance, ζ, between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q _p′q′ (t+τ) represents the time-varying distance, f, between the unmanned aerial vehicle UAV antenna unit p' and the user antenna unit q _pq (t) time-varying Doppler shift representing direct components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, f _p′q′ (t+τ) represents the time-varying Doppler shift of the direct component direct link between the unmanned aerial vehicle UAV antenna unit p 'and the user antenna unit q', ∈ - >Representing unmanned aerial vehicle UAV antenna unit p and diffuser->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q,/->Representing unmanned aerial vehicle UAV antenna unit p' and diffuser->Time-varying distance between->Representing scatterer->And the time-varying distance between the subscriber-side antenna elements q'>Time-varying Doppler shift indicative of scattering components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q, < >>Time-varying Doppler shift indicative of scattering components between unmanned aerial vehicle UAV antenna unit p' and user antenna unit q->Representing scatterer->Azimuth angle of->Representing scatterer->Is>Representing scatterer->Probability density function of azimuth angle +.>Representing scatterer->Probability density function, ζ, of elevation angle _pmn (t) represents the time-varying distance, ζ, of the link between the unmanned aerial vehicle UAV antenna unit p and the (m, n) -th smart reflection unit _mnq (t) represents the time-varying distance, ζ, of the link between the (m, n) -th smart reflection unit and the user antenna unit q _p′mn (t+τ) represents the time-varying propagation distance, ζ, of the link between the unmanned aerial vehicle UAV antenna unit p' and the (m, n) -th smart reflection unit _mnq′ (t+τ) represents the time-varying propagation distance of the link between the (m, n) -th smart reflection unit and the user antenna unit q', f _pqmn (t) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user antenna unit q after passing through the (m, n) -th intelligent reflection unit, f _p′q′mn (t+τ) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p 'and the user side antenna unit q' after (M, N) -th smart reflection units, N represents the number of column reflection units of the smart reflection surface IRS, N represents the column position index of the smart reflection units, M represents the number of row reflection units of the smart reflection surface IRS, M represents the row position index of the smart reflection units>Representing scatterer->And the time-varying propagation distance of the link between the subscriber-side antenna units q,/->Representing scatterer->And the time-varying propagation distance of the link between the subscriber-side antenna unit q>Representing multipath components between unmanned aerial vehicle UAV antenna unit p and user antenna unit q via intelligent reflecting surface IRS and scatterer +.>Post time-varying Doppler shift, < >>Representing multipath components between unmanned aerial vehicle UAV antenna unit p 'and user antenna unit q' through intelligent reflecting surface IRS and scatterer +.>Time-varying doppler shift of the reflected component,/->Representing scatterer->Azimuth angle of->Representing scatterer->Is>Representing scatterer->Probability density function of azimuth angle +. >Representing scatterer->Exp (·) represents an exponential function, κ represents a scattering environment factor, μ represents an average angle of arrival of the scattering component, I ₀ Represents a zero-order Bessel function, |·| represents an absolute value function, β _max Representing the maximum elevation angle of the scatterer;