CN113949474A - Unmanned aerial vehicle geometric model establishing method based on assistance of intelligent reflecting surface - Google Patents

Unmanned aerial vehicle geometric model establishing method based on assistance of intelligent reflecting surface Download PDF

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CN113949474A
CN113949474A CN202111135455.0A CN202111135455A CN113949474A CN 113949474 A CN113949474 A CN 113949474A CN 202111135455 A CN202111135455 A CN 202111135455A CN 113949474 A CN113949474 A CN 113949474A
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CN113949474B (en
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练柱先
苏胤杰
王亚军
靳标
张贞凯
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Jiangsu University of Science and Technology
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Abstract

The invention discloses an unmanned aerial vehicle geometric model building method based on intelligent reflector assistance, which comprises the steps of building an unmanned aerial vehicle geometric model based on intelligent reflector assistance according to the position relation among an unmanned aerial vehicle, an intelligent reflector and a receiving end, and obtaining the complex channel gain of a channel; designing an optimization problem according to a geometric model of the unmanned aerial vehicle and a received signal power maximization principle; simplifying the optimization problem; solving the optimal reflection phase of the intelligent reflecting 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 reflecting surface through the obtained reflecting phase and the time-varying parameters, and determining the influence of the intelligent reflecting surface on the channel characteristics of the unmanned aerial vehicle 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 establishing method can provide powerful support for the exploration of the key technology of the 6G communication system.

Description

Unmanned aerial vehicle geometric model establishing method based on assistance of intelligent reflecting surface
Technical Field
The invention relates to a wireless communication technology, in particular to an unmanned aerial vehicle geometric model building method based on the assistance of an intelligent reflecting surface.
Background
In recent years, with the rapid development of the manufacturing technology of the unmanned aerial vehicle, the unmanned aerial vehicle plays a vital role in pesticide spraying, express transportation, disaster relief and emergency rescue and the like. The high flexibility and low cost of deployment of drones, which act as aerial mobile base stations or relay mobile base stations in wireless communications, have attracted a great deal of attention from the industry and academia. It is noted that the propagation environment between the drone and the user end is not controllable, which affects the system performance of the drone communication system. The intelligent reflector IRS consists of units with adjustable amplitude, phase and frequency, and can control the propagation environment between the transmitting end and the receiving end. The existing literature 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 the intelligent reflective surface IRS in the communication system of the drone. Accurate channel modeling can provide a basis for system performance analysis and precoding algorithm design in the future.
In the disclosure of the prior art, some studies have been made on the capability of the intelligent reflector IRS to eliminate doppler effect and multipath fading, but due to the high-speed moving characteristic of the unmanned aerial vehicle UAV, the unmanned aerial vehicle UAV channel is a non-stationary process, and therefore, the technology cannot be directly applied to the unmanned aerial vehicle communication scene. Some consider the effect of the drone path on the performance of a reconstructed smart surface assisted drone communication system, but this technique ignores the consideration of the sum of the number of smart reflective units. Some consider a three-dimensional geometric channel model of a non-stationary 6G communication system, which uses an intelligent reflector IRS to control the propagation environment between the transmitting and receiving ends, and assumes that the reflection phase is determined by the propagation distance between the transmitting and receiving ends, but this technique ignores the influence of the time-varying doppler shift on the channel statistics. Some studies have also been made on a wideband non-stationary random channel model of an intelligent reflector-assisted MIMO communication system, which takes into account the influence of an intelligent reflector on the statistical properties of the channel, but ignores the consideration of the reflection phase of the intelligent reflector unit.
In summary, the unmanned aerial vehicle UAV channel modeling based on the assistance of the intelligent reflector IRS is in an initial stage, and the statistical characteristics of the intelligent reflector IRS on the unmanned aerial vehicle UAV channel remain to be explored, so that an accurate unmanned aerial vehicle UAV channel modeling based on the assistance of the intelligent reflector IRS is very necessary.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide an accurate unmanned aerial vehicle modeling method based on reflector assistance, and the model can be established to provide a basis for system performance analysis and precoding algorithm design in the future.
The technical scheme is as follows: the invention discloses an unmanned aerial vehicle geometric model building method based on intelligent reflector assistance, which comprises the following steps:
s1, establishing an unmanned aerial vehicle geometric model based on the assistance of the intelligent reflector IRS according to the position relation among the unmanned aerial vehicle UAV, the intelligent reflector IRS and the receiving end, and obtaining the complex channel gain of a channel;
s2, designing an optimization problem according to an intelligent reflector IRS-assisted unmanned aerial vehicle geometric model based on a received signal power maximization principle;
s3, according to the power of the received signal, mainly focusing on the direct component reflected by the intelligent reflecting surface IRS, simplifying the optimization problem;
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 side and the intelligent reflector IRS;
s6, obtaining a time-varying reflection phase, a time-varying distance and a time-varying Doppler shift through the steps S4 and S5, solving a space-time correlation function based on the assistance of the intelligent reflecting surface IRS, and determining the influence of the intelligent reflecting surface IRS on the channel characteristics of the unmanned aerial vehicle through correlation analysis.
Further, the complex channel gain based on the geometry model assisted by the intelligent reflector in step S1 is expressed as follows:
Figure BDA0003281860190000021
wherein ,
Figure BDA0003281860190000022
Figure BDA0003281860190000023
Figure BDA0003281860190000024
Figure BDA0003281860190000025
wherein t represents a time variable, hpq(t) represents the complex channel gain of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000026
represents the complex channel gain of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000031
represents the complex channel gain of the scattering component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000032
represents the complex channel gain of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user-side antenna unit q after being reflected by the intelligent reflecting surface IRS,
Figure BDA0003281860190000033
represents the complex channel gain theta of the scattering component between the UAV antenna unit p and the user terminal antenna unit q after being scattered by the intelligent reflector IRS and the scatterermn(t) shows the reflection phase of the Intelligent reflective surface IRS at time t, GtIndicating originating antennaGain, GrThe gain of the receiving-end antenna is shown,
Figure BDA0003281860190000034
representing the path loss from the unmanned aerial vehicle UAV to the user terminal, K represents the rice factor,
Figure BDA0003281860190000035
representing the path loss from the unmanned aerial vehicle UAV to the intelligent reflector IRS, pi representing the circumferential ratio, lambda representing the carrier wavelength, ξpq(t) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fpq(t) time varying Doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, N1Representing scatterers
Figure BDA0003281860190000036
The number of the (c) component (a),
Figure BDA0003281860190000037
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000038
Time-varying distance between, xin1q(t) represents a scattering body
Figure BDA0003281860190000039
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA00032818601900000310
representing a scattering body
Figure BDA00032818601900000311
Time-varying doppler shift of the scattered component of (xi)pmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the multipath component between the UAV antenna unit p and the user-side antenna unit q via (m, n) -th intelligenceTime varying Doppler shift after reflection unit, N2Representing scatterers
Figure BDA00032818601900000312
The number of the (c) component (a),
Figure BDA00032818601900000313
expressing (m, n) -th intelligent reflection unit and scatterer
Figure BDA00032818601900000314
The time-varying distance between them,
Figure BDA00032818601900000315
representing scatterers
Figure BDA00032818601900000316
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA00032818601900000317
showing multipath components between the UAV antenna unit p and the user side antenna unit q via the intelligent reflector IRS and the scatterer
Figure BDA00032818601900000318
The latter time-varying doppler shift.
Further, the optimization problem in step S2 is expressed as follows:
Figure BDA00032818601900000319
where t represents a time variable, θmn(t) denotes the reflection phase of the intelligent reflective surface IRS at time t,
Figure BDA00032818601900000320
represents a statistical mean operation, hpq(t) represents the complex channel gain of the link between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q.
Further, step S3 includes the following steps:
s31, considering the concentrated received signal power, simplifying the optimization problem of step S2, the simplified formula is as follows:
Figure BDA0003281860190000041
wherein ,
Figure BDA0003281860190000042
Figure BDA0003281860190000043
Figure BDA0003281860190000044
Figure BDA0003281860190000045
Figure BDA0003281860190000046
Figure BDA0003281860190000047
Figure BDA0003281860190000048
Figure BDA0003281860190000049
wherein ,
Figure BDA00032818601900000410
representing a statistical mean operation, t represents a time variable,
Figure BDA00032818601900000411
and
Figure BDA00032818601900000412
representing an auxiliary variable, cos (-) representing a cosine function,
Figure BDA00032818601900000413
representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA00032818601900000414
represents the time-varying phase of the multipath component between the UAV antenna unit p and the user terminal antenna unit q after passing through the (m, N) -th intelligent reflection unit, N1Representing scatterers
Figure BDA00032818601900000415
The number of the (c) component (a),
Figure BDA00032818601900000416
represents multipath components between the UAV antenna unit p and the user-side antenna unit q via scatterers
Figure BDA0003281860190000051
The phase of the latter time-varying phase,
Figure BDA0003281860190000052
the time-varying phase of multipath components between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user side antenna unit q after passing through an (M ', N') -th intelligent reflection unit is represented, M represents the number of IRS row reflection units of an intelligent reflection surface, N represents the number of IRS column reflection units of the intelligent reflection surface, pi represents a circumferential ratio, lambda represents a carrier wavelength, and xi representspq(t) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fpq(t) represents the time-varying doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000053
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000054
The time-varying distance between them,
Figure BDA0003281860190000055
representing scatterers
Figure BDA0003281860190000056
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000057
time varying doppler shift, ξ, representing the scattering component between unmanned aerial vehicle UAV antenna unit p and user side antenna unit qpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the time-varying Doppler shift, theta, of multipath components between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, n) -th intelligent reflection unitmn(t) represents the time-varying reflection phase, G, of the (m, n) -th intelligent reflection unittIndicating the originating antenna gain, GrThe gain of the receiving-end antenna is shown,
Figure BDA0003281860190000058
representing the path loss from the unmanned aerial vehicle UAV to the user terminal, K represents the rice factor,
Figure BDA0003281860190000059
representing the path loss, δ, of the UAV to the IRSMRepresenting the antenna spacing, δ, of adjacent row reflector elementsNThe antenna spacing adjacent to the column reflection unit is shown;
s32, assuming the auxiliary variable is
Figure BDA00032818601900000510
And
Figure BDA00032818601900000511
wherein
Figure BDA00032818601900000512
And assuming a time-varying reflection phase of the intelligent reflection surface as
Figure BDA00032818601900000513
The optimization problem is further simplified as follows:
Figure BDA00032818601900000514
wherein ,
Figure BDA00032818601900000515
and
Figure BDA00032818601900000516
both represent auxiliary variables.
Further, the optimal intelligent reflective surface IRS reflection phase θ obtained in step S4mn(t) is represented by the following formula:
Figure BDA00032818601900000517
wherein ,
Figure BDA0003281860190000061
Figure BDA0003281860190000062
Figure BDA0003281860190000063
where π denotes the circumference ratio, λ denotes the carrier wavelength, t denotes the time variable, ξpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the time-varying Doppler shift of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q after passing through the (m, n) -th intelligent reflection unit,
Figure BDA0003281860190000064
representing an auxiliary variable, sgn (·) representing a sign function, arctan (·) representing an arctangent function, χARepresenting an auxiliary variable, χBThe auxiliary variable is represented by a number of variables,
Figure BDA0003281860190000065
representing an auxiliary variable, cos (-) representing a cosine function,
Figure BDA0003281860190000066
representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q, sin (-) represents a sinusoidal function,
Figure BDA0003281860190000067
the auxiliary variable is represented by a number of variables,
Figure BDA0003281860190000068
represents multipath components between the UAV antenna unit p and the user-side antenna unit q via scatterers
Figure BDA0003281860190000069
The phase of the latter time-varying phase,
Figure BDA00032818601900000610
representing scatterers
Figure BDA00032818601900000611
The azimuth angle of (a) is,
Figure BDA00032818601900000612
representing scatterers
Figure BDA00032818601900000613
The angle of elevation of (a) is,
Figure BDA00032818601900000614
a function representing the probability density of the azimuth,
Figure BDA00032818601900000615
representing the elevation probability density function.
Further, step S5 includes the following steps:
s51, solving time-varying distance xi from Unmanned Aerial Vehicle (UAV) antenna unit p to user terminal antenna unit qpq(t), the calculation formula is as follows:
ξpq(t)＝||dpq(t)|| (6)；
wherein ,
Figure BDA00032818601900000616
Figure BDA00032818601900000617
Figure BDA0003281860190000071
Figure BDA0003281860190000072
vR＝vR[cosγR,sinγR,0]；
wherein, | | · | | represents norm operation, t represents time variable, ξpq(t) represents the time varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, dpq(t) shows unmanned aerial vehicle UAV antenna unit p and useThe time-varying distance vector between the subscriber antenna elements q,
Figure BDA0003281860190000073
representing the position vector of the unmanned aerial vehicle UAV antenna unit p, NTRepresenting the number of UAV antenna units, p represents the UAV antenna unit position index, δTRepresents the spacing, theta, of adjacent antenna units of the unmanned aerial vehicle UAVTRepresenting the unmanned aerial vehicle UAV antenna unit direction, sin (·) representing a sine function, cos (·) representing a cosine function, tan (·) representing a tangent function, ξTRRepresents the horizontal distance, θ, of the unmanned aerial vehicle UAV and the user terminalTRIndicating the direction, beta, of the unmanned aerial vehicle UAV antenna unit relative to the user sideTRRepresenting the elevation angle of the unmanned aerial vehicle UAV antenna unit relative to the user's end,
Figure BDA0003281860190000074
representing the location vector of the subscriber terminal antenna unit q, NRRepresenting the number of antenna units at the subscriber end, q representing the index of the location of the antenna units at the subscriber end, deltaRRepresents the distance between adjacent antenna units at the user end, thetaRIndicating the direction of the antenna unit at the subscriber end, vTRepresenting unmanned aerial vehicle UAV velocity vector, vRRepresenting the velocity vector, v, of the user terminalTRepresenting the magnitude of the unmanned aerial vehicle UAV velocity,
Figure BDA00032818601900000711
elevation angle, gamma, representing the direction of movement of an Unmanned Aerial Vehicle (UAV)TIndicating the direction of the unmanned aerial vehicle UAV movement, vRIndicates the velocity of the user terminal, gammaRRepresenting the moving direction azimuth of the user terminal;
solving for a time-varying Doppler shift f of the direct component between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user-side antenna unit qpq(t), the calculation formula is as follows:
Figure BDA0003281860190000075
wherein λ represents a carrier wavelength;
s52, obtainingSolving that the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q respectively reach the scatterer
Figure BDA0003281860190000076
Time-varying distance of
Figure BDA0003281860190000077
And
Figure BDA0003281860190000078
the calculation formula is as follows:
Figure BDA0003281860190000079
Figure BDA00032818601900000710
wherein ,
Figure BDA0003281860190000081
Figure BDA0003281860190000082
wherein ,
Figure BDA0003281860190000083
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000084
The time-varying distance between them,
Figure BDA0003281860190000085
representing scatterers
Figure BDA0003281860190000086
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000087
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000088
A time-varying distance vector between the two,
Figure BDA0003281860190000089
representing scatterers
Figure BDA00032818601900000810
And the time-varying distance vector between the subscriber terminal antenna unit q,
Figure BDA00032818601900000811
representing client-to-scatterers
Figure BDA00032818601900000812
The horizontal distance of (a) is,
Figure BDA00032818601900000813
representing scatterers
Figure BDA00032818601900000814
The azimuth angle of (a) is,
Figure BDA00032818601900000815
representing scatterers
Figure BDA00032818601900000816
Elevation angle of (d);
solving for time-varying Doppler shift of scattering components between Unmanned Aerial Vehicle (UAV) antenna unit p and user side antenna unit q
Figure BDA00032818601900000817
The calculation formula is as follows:
Figure BDA00032818601900000818
wherein λ represents a carrier wavelength;
s53, solving time-varying distances xi between an Unmanned Aerial Vehicle (UAV) antenna unit p, a user side antenna unit q and an intelligent reflection unit (m, n) -thpmn(t) and ξmnq(t), the calculation formula is as follows:
ξpmn(t)＝||dpmn(t)|| (11)；
ξmnq(t)＝||dmnq(t)|| (12)；
wherein ,
Figure BDA00032818601900000819
Figure BDA00032818601900000820
Figure BDA00032818601900000821
wherein ,ξpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, dpmn(t) represents the time-varying distance vector between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unit, dmnq(t) represents a time-varying distance vector between the reflection of the (m, n) -th intelligent reflection unit and the user terminal antenna unit q,
Figure BDA0003281860190000091
representing the position vector of the (M, n) -th intelligent reflection unit, M representing the number of line reflection units of the intelligent reflection surface, M representing the line position index of the intelligent reflection unit, deltaMIndicating the spacing, θ, of adjacent row reflective elements of the intelligent reflective surface IRSIRSIndicating the arrangement direction of the intelligent reflecting surface IRS, N indicating the number of column reflecting units of the intelligent reflecting surface, N indicating the column position index of the intelligent reflecting units, deltaNIndicating the spacing, xi, of adjacent column reflecting elements of the intelligent reflecting surfaceIRSRRepresenting the horizontal distance between the intelligent reflecting surface and the user side;
solving the time-varying Doppler frequency shift f of multipath components between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user side antenna unit q after passing through an (m, n) -th intelligent reflection unitpqmn(t), the calculation formula is as follows:
Figure BDA0003281860190000092
s54 solving scatterers
Figure BDA0003281860190000093
Time varying distance from user terminal antenna unit q
Figure BDA0003281860190000094
The calculation formula is as follows:
Figure BDA0003281860190000095
wherein ,
Figure BDA0003281860190000096
wherein ,
Figure BDA0003281860190000097
representing scatterers
Figure BDA0003281860190000098
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000099
representing a scattering body
Figure BDA00032818601900000910
And the time-varying distance vector between the subscriber terminal antenna unit q,
Figure BDA00032818601900000911
representing client-to-scatterers
Figure BDA00032818601900000912
The horizontal distance of (a) is,
Figure BDA00032818601900000913
representing scatterers
Figure BDA00032818601900000914
The azimuth angle of (a) is,
Figure BDA00032818601900000915
representing scatterers
Figure BDA00032818601900000916
Elevation angle of (d);
solving multipath components between UAV antenna unit p and user side antenna unit q through intelligent reflecting surface IRS and scatterer
Figure BDA00032818601900000917
Later time-varying Doppler shift
Figure BDA00032818601900000918
The calculation formula is as follows:
Figure BDA00032818601900000919
further, step S6 includes the following steps:
s61, solving the space-time correlation function of the geometrical channel of the unmanned aerial vehicle assisted by the intelligent reflector IRS by using the time-varying parameters obtained in the steps S3 and S4, wherein the calculation formula is as follows:
Figure BDA00032818601900000920
Figure BDA0003281860190000101
Figure BDA0003281860190000102
Figure BDA0003281860190000103
wherein ：
Figure BDA0003281860190000104
Figure BDA0003281860190000105
Figure BDA0003281860190000106
Figure BDA0003281860190000107
wherein ,
Figure BDA0003281860190000108
represents the space-time correlation of the direct component between the unmanned aerial vehicle UAV antenna unit and the user-side antenna unit,
Figure BDA0003281860190000109
represents the space-time correlation of the scattering components between the unmanned aerial vehicle UAV antenna units and the user-side antenna units,
Figure BDA00032818601900001010
indicating that the space between the UAV antenna unit and the user side antenna unit is reflected by the intelligent reflection surface IRSThe space-time correlation of the direct component of (c),
Figure BDA00032818601900001011
indicating that between the UAV antenna unit and the user side antenna unit via the intelligent reflection surface IRS and scatterer
Figure BDA00032818601900001012
The space-time dependence of the reflected scattered component, t representing the time variable, δTRepresenting the antenna spacing, δ, between the unmanned aerial vehicle UAV antenna unitsRThe antenna spacing between the antenna units at the user terminal is represented, tau represents propagation delay, K represents Rice factor, lambda represents carrier wavelength, pi represents circumferential ratio, and is taken as 3.14 and xipq(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit qp′q′(t + τ) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p 'and the user-side antenna unit q', fpq(t) time varying Doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fp′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 terminal antenna unit q',
Figure BDA0003281860190000111
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000112
The time-varying distance between them,
Figure BDA0003281860190000113
representing scatterers
Figure BDA0003281860190000114
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000115
representing unmanned aerial vehicle UAV antenna unit p' and scatterers
Figure BDA0003281860190000116
The time-varying distance between them,
Figure BDA0003281860190000117
representing scatterers
Figure BDA0003281860190000118
And the time varying distance between the subscriber side antenna unit q',
Figure BDA0003281860190000119
represents the time-varying doppler shift of the scattering component between the unmanned aerial vehicle UAV antenna unit p and the user-side antenna unit q,
Figure BDA00032818601900001110
represents the time-varying doppler shift of the scattering component between the unmanned aerial vehicle UAV antenna unit p 'and the user-side antenna unit q',
Figure BDA00032818601900001111
representing scatterers
Figure BDA00032818601900001112
The azimuth angle of (a) is,
Figure BDA00032818601900001113
representing scatterers
Figure BDA00032818601900001114
The angle of elevation of (a) is,
Figure BDA00032818601900001115
representing scatterers
Figure BDA00032818601900001116
The probability density function of the azimuth angle,
Figure BDA00032818601900001117
representing scatterers
Figure BDA00032818601900001118
Probability density function of elevation angle of, ξpmn(t) represents the time-varying distance, ξ, of the link between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th intelligent reflection unitmnq(t) represents the time-varying distance, ξ, of the link between the (m, n) -th intelligent reflection unit and the user terminal antenna unit qp′mn(t + τ) represents the time-varying propagation distance, ξ, of the link between unmanned aerial vehicle UAV antenna units p' and (m, n) -th smart reflector unitsmnq′(t + τ) represents the time-varying propagation distance of the link between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q', fpqmn(t) represents the time-varying Doppler shift of the multipath component between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, n) -th intelligent reflection unit, fp′q′mn(t + τ) represents the time-varying Doppler shift of the multipath component between the UAV antenna unit p 'and the user-side antenna unit q' after passing through the (M, N) -th intelligent reflection unit, N represents the number of column reflection units of the intelligent reflection surface IRS, N represents the column position index of the intelligent reflection unit, M represents the number of row reflection units of the intelligent reflection surface IRS, M represents the row position index of the intelligent reflection unit,
Figure BDA00032818601900001119
representing scatterers
Figure BDA00032818601900001120
And the time-varying propagation distance of the link between the subscriber side antenna unit q,
Figure BDA00032818601900001121
representing scatterers
Figure BDA00032818601900001122
And the time-varying propagation distance of the link between the subscriber side antenna unit q',
Figure BDA00032818601900001123
showing multipath components between the UAV antenna unit p and the user side antenna unit q via the intelligent reflector IRS and the scatterer
Figure BDA00032818601900001124
The latter time-varying doppler shift is then,
Figure BDA00032818601900001125
represents multipath components between the UAV antenna unit p 'and the user terminal antenna unit q' via the intelligent reflection surface IRS and the scatterer
Figure BDA00032818601900001126
The time-varying doppler shift of the reflected component,
Figure BDA00032818601900001127
representing scatterers
Figure BDA00032818601900001128
The azimuth angle of (a) is,
Figure BDA00032818601900001129
representing scatterers
Figure BDA00032818601900001130
The angle of elevation of (a) is,
Figure BDA00032818601900001131
representing scatterers
Figure BDA00032818601900001132
The probability density function of the azimuth angle,
Figure BDA00032818601900001133
representing scatterers
Figure BDA00032818601900001134
Exp (-) represents an exponential function, κ represents a scattering environment factor, μ represents the average angle of arrival of the scattered component, I0Representing a Bessel function of zero order, |, representing an absolute value function, βmaxRepresents the maximum elevation angle of the scatterer;
s62, determining the influence of the intelligent reflecting surface IRS, the number of the intelligent reflecting units and the size of the intelligent reflecting units on the channel statistical characteristics of the unmanned aerial vehicle UAV by using the obtained space-time correlation function.
Has the advantages that: compared with the prior art, the unmanned aerial vehicle geometric model based on the assistance of the intelligent reflector considers the influence of the IRS on the UAV (unmanned aerial vehicle) channel characteristics, considers the optimal reflection phase under the received signal power maximization principle, and adopts the time-varying parameters to describe the channel characteristics of the UAV channel; 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 an unmanned aerial vehicle channel is considered; therefore, the method can better explore the influence of the intelligent reflector IRS on the channel statistical characteristics of the unmanned aerial vehicle.
Drawings
FIG. 1 is a schematic diagram of a geometric model of an unmanned aerial vehicle with the aid of an intelligent reflector IRS;
FIG. 2 is a comparison graph of absolute envelope amplitudes of the intelligent reflective surface IRS at different reflection phases;
FIG. 3 is a comparison graph of absolute envelope amplitudes for different numbers of reflection units of the intelligent reflection surface IRS;
FIG. 4 is a comparison graph of absolute envelope amplitudes for different reflection unit geometric areas of the intelligent reflection surface IRS;
FIG. 5 is a comparison graph of the channel spatial correlation function of the UAV with different numbers of IRS reflection units on the intelligent reflection surface;
fig. 6 is a comparison graph of the intelligent reflector IRS assisted drone channel time correlation function at different drone 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 invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
According to the invention, the intelligent reflector IRS is adopted to control the propagation environment of the UAV channel, the optimal received signal power is considered, and the optimal intelligent reflector IRS reflection phase is obtained. The invention considers the capability of the intelligent reflector IRS to change the unmanned aerial vehicle channel propagation environment, namely the influence of the number of the intelligent reflector IRS reflection units and the size of the reflection units on the unmanned aerial vehicle channel statistical characteristics. The invention considers the unmanned aerial vehicle channel assisted by the intelligent reflector IRS, explores the influence of the intelligent reflector IRS on the statistical characteristics of the unmanned aerial vehicle channel, and better provides a basis 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 reflector assistance, which comprises the following steps:
s1, establishing a geometric model of the unmanned aerial vehicle according to the position relation among the unmanned aerial vehicle UAV, the intelligent reflector IRS and the receiving end, and obtaining the complex channel gain of the channel;
the invention considers the change of the intelligent reflector IRS to the channel propagation environment, and provides an Unmanned Aerial Vehicle (UAV) channel model based on the assistance of the intelligent reflector IRS, wherein the complex gain of the channel is expressed as follows:
Figure BDA0003281860190000131
wherein ,
Figure BDA0003281860190000132
Figure BDA0003281860190000133
Figure BDA0003281860190000134
Figure BDA0003281860190000135
wherein,t represents a time variable, hpq(t) represents the complex channel gain of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000136
represents the complex channel gain of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000137
represents the complex channel gain of the scattering component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000138
represents the complex channel gain of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user-side antenna unit q after being reflected by the intelligent reflecting surface IRS,
Figure BDA0003281860190000139
represents the complex channel gain theta of the scattering component between the UAV antenna unit p and the user terminal antenna unit q after being scattered by the intelligent reflector IRS and the scatterermn(t) shows the reflection phase of the Intelligent reflective surface IRS at time t, GtIndicating the originating antenna gain, GrThe gain of the receiving-end antenna is shown,
Figure BDA00032818601900001310
representing the path loss from the unmanned aerial vehicle UAV to the user terminal, K represents the rice factor,
Figure BDA00032818601900001311
representing the path loss from the unmanned aerial vehicle UAV to the intelligent reflector IRS, pi representing the circumferential ratio, lambda representing the carrier wavelength, ξpq(t) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fpq(t) time varying Doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, N1Representing scatterers
Figure BDA0003281860190000141
The number of the (c) component (a),
Figure BDA0003281860190000142
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000143
The time-varying distance between them,
Figure BDA0003281860190000144
representing scatterers
Figure BDA0003281860190000145
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000146
representing a scattering body
Figure BDA0003281860190000147
Time-varying doppler shift of the scattered component of (xi)pmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the time-varying Doppler shift between the multipath components of the UAV antenna unit p and the user-side antenna unit q after passing through the (m, N) -th intelligent reflection unit, N2Representing scatterers
Figure BDA0003281860190000148
The number of the (c) component (a),
Figure BDA0003281860190000149
expressing (m, n) -th intelligent reflection unit and scatterer
Figure BDA00032818601900001410
The time-varying distance between them,
Figure BDA00032818601900001411
representing scatterers
Figure BDA00032818601900001412
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA00032818601900001413
showing multipath components between the UAV antenna unit p and the user side antenna unit q via the intelligent reflector IRS and the scatterer
Figure BDA00032818601900001414
The latter time-varying doppler shift.
S2, designing an optimization problem according to an intelligent reflector IRS-assisted unmanned aerial vehicle communication scene by using a received signal power maximization principle;
the invention considers the influence of the intelligent reflector IRS on the unmanned aerial vehicle channel propagation environment, so the optimization problem is designed according to the principle of maximizing the received signal power. Wherein the optimization problem is represented as follows:
Figure BDA00032818601900001415
where t represents a time variable, θmn(t) denotes the reflection phase of the intelligent reflective surface IRS at time t,
Figure BDA00032818601900001416
represents a statistical mean operation, hpq(t) represents the complex channel gain of the link between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q.
S3, according to the power of the received signal, mainly focusing on the direct component reflected by the intelligent reflecting surface IRS, simplifying the optimization problem; specifically, the method comprises the following steps:
s31, the received signal is composed of a direct component, a scattering component, a direct component passing through the intelligent reflecting surface IRS and a scattering component passing through the intelligent reflecting surface, and the complexity of solving the optimization problem is caused. In order to reduce complexity, the invention considers more concentrated received signal power, and the simplified optimization problem can be expressed as:
Figure BDA0003281860190000151
wherein ,
Figure BDA0003281860190000152
Figure BDA0003281860190000153
Figure BDA0003281860190000154
Figure BDA0003281860190000155
Figure BDA0003281860190000156
Figure BDA0003281860190000157
Figure BDA0003281860190000158
Figure BDA0003281860190000159
wherein ,
Figure BDA00032818601900001510
representing a statistical mean operation, t represents a time variable,
Figure BDA00032818601900001511
and
Figure BDA00032818601900001512
representing an auxiliary variable, cos (-) representing a cosine function,
Figure BDA00032818601900001513
representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA00032818601900001514
represents the time-varying phase, N, of the direct component between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, N) -th intelligent reflection unit1Representing scatterers
Figure BDA00032818601900001515
The number of the (c) component (a),
Figure BDA00032818601900001516
represents multipath components between the UAV antenna unit p and the user-side antenna unit q via scatterers
Figure BDA00032818601900001517
The phase of the latter time-varying phase,
Figure BDA00032818601900001518
the time-varying phase of multipath components between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user side antenna unit q after passing through an M 'th row and an N' th column of intelligent reflection units is represented, M represents the number of the intelligent reflection surface IRS row reflection units, N represents the number of the intelligent reflection surface IRS column reflection units, pi represents a circumferential ratio, 3.14 is taken, lambda represents a carrier wavelength, and xi represents a circular degreepq(t) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fpq(t) represents the time-varying doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000161
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000162
The time-varying distance between them,
Figure BDA0003281860190000163
representing scatterers
Figure BDA0003281860190000164
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000165
time varying doppler shift, ξ, representing the scattering component between unmanned aerial vehicle UAV antenna unit p and user side antenna unit qpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the time-varying Doppler shift, theta, of multipath components between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, n) -th intelligent reflection unitmn(t) represents the time-varying reflection phase, G, of the (m, n) -th intelligent reflection unittIndicating the originating antenna gain, GrThe gain of the receiving-end antenna is shown,
Figure BDA0003281860190000166
representing the path loss from the unmanned aerial vehicle UAV to the user terminal, K represents the rice factor,
Figure BDA0003281860190000167
representing the path loss, δ, of the UAV to the IRSMRepresenting the antenna spacing, δ, of adjacent row reflector elementsNIndicating the antenna spacing adjacent the column reflector element.
S32, assuming auxiliary variables
Figure BDA0003281860190000168
And auxiliary variables
Figure BDA0003281860190000169
wherein
Figure BDA00032818601900001610
And assuming a time-varying reflection phase of the intelligent reflection surface as
Figure BDA00032818601900001611
The optimization problem is further simplified as follows:
Figure BDA00032818601900001612
wherein ,
Figure BDA00032818601900001613
representing the auxiliary variable.
S4, solving the optimization problem to obtain the optimal IRS reflection phase of the intelligent reflection surface;
the simplified optimization problem can be solved by adopting a method existing in the literature, and the optimal IRS reflection phase of the intelligent reflection surface can be represented by the following formula:
Figure BDA00032818601900001614
wherein ,
Figure BDA0003281860190000171
Figure BDA0003281860190000172
Figure BDA0003281860190000173
where π represents the circumference ratio, 3.14 is taken, λ represents the carrier wavelength, t represents the time variable, ξpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the time-varying Doppler shift of multipath components between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, n) -th intelligent reflection unit, sgn (·) represents a sign function, arctan (·) represents an arctangent function, and χ represents a linear functionARepresenting an auxiliary variable, χBThe auxiliary variable is represented by a number of variables,
Figure BDA0003281860190000174
representing an auxiliary variable, cos (-) representing a cosine function,
Figure BDA0003281860190000175
representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q, sin (-) represents a sinusoidal function,
Figure BDA0003281860190000176
the auxiliary variable is represented by a number of variables,
Figure BDA0003281860190000177
represents multipath components between the UAV antenna unit p and the user-side antenna unit q via scatterers
Figure BDA0003281860190000178
The phase of the latter time-varying phase,
Figure BDA0003281860190000179
representing scatterers
Figure BDA00032818601900001710
The azimuth angle of (a) is,
Figure BDA00032818601900001711
representing scatterers
Figure BDA00032818601900001712
The angle of elevation of (a) is,
Figure BDA00032818601900001713
a function representing the probability density of the azimuth,
Figure BDA00032818601900001714
representing the elevation probability density function.
S5, determining time-varying parameters among the unmanned aerial vehicle, the user side and the intelligent reflector IRS;
s51, solving time-varying azimuth angle and time-varying elevation angle parameters between the transceiving end, the intelligent reflecting surface IRS and the scatterer, and obtaining the time-varying distance xi from the UAV antenna unit p to the user end antenna unit qpq(t), the calculation formula is as follows:
ξpq(t)＝||dpq(t)|| (6)；
wherein ,
Figure BDA00032818601900001715
Figure BDA00032818601900001716
Figure BDA00032818601900001717
Figure BDA00032818601900001718
vR＝vR[cosγR,sinγR,0]；
wherein, | | · | | represents norm operation, t represents time variable, ξpq(t) represents the time varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, dpq(t) represents the time-varying distance vector between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure BDA0003281860190000181
representing the position vector of the unmanned aerial vehicle UAV antenna unit p, NTRepresenting the number of UAV antenna units, p represents the UAV antenna unit position index, δTRepresents the spacing, theta, of adjacent antenna units of the unmanned aerial vehicle UAVTRepresenting unmanned aerial vehicle UAV antenna unit orientation, tan (·) represents tangent function, ξTRRepresents the horizontal distance, θ, of the unmanned aerial vehicle UAV and the user terminalTRIndicating the direction, beta, of the unmanned aerial vehicle UAV antenna unit relative to the user sideTRRepresenting the elevation angle of the unmanned aerial vehicle UAV antenna unit relative to the user's end,
Figure BDA0003281860190000182
representing the location vector of the subscriber terminal antenna unit q, NRRepresenting the number of antenna units at the subscriber end, q representing the index of the location of the antenna units at the subscriber end, deltaRRepresents the distance between adjacent antenna units at the user end, thetaRIndicating the direction of the antenna unit at the subscriber end, vTRepresenting unmanned aerial vehicle UAV velocity vector, vRRepresenting the velocity vector, v, of the user terminalTRepresenting the magnitude of the unmanned aerial vehicle UAV velocity,
Figure BDA0003281860190000183
elevation angle, gamma, representing the direction of movement of an Unmanned Aerial Vehicle (UAV)TIndicating the direction of the unmanned aerial vehicle UAV movement, vRIndicates the velocity of the user terminal, gammaRIndicating the azimuth of the moving direction of the user terminal.
Solving for a time-varying Doppler shift f of the direct component between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user-side antenna unit qpq(t), the calculation formula is as follows:
Figure BDA0003281860190000184
where λ represents the carrier wavelength.
S52, solving the problem that the UAV antenna unit p and the user-side antenna unit q are respectively connected to scatterers
Figure BDA0003281860190000185
Time-varying distance of
Figure BDA0003281860190000186
And
Figure BDA0003281860190000187
the calculation formula is as follows:
Figure BDA0003281860190000188
Figure BDA0003281860190000189
wherein ,
Figure BDA00032818601900001810
Figure BDA00032818601900001811
wherein ,
Figure BDA00032818601900001812
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA00032818601900001813
The time-varying distance between them,
Figure BDA00032818601900001814
representing scatterers
Figure BDA0003281860190000191
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000192
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000193
A time-varying distance vector between the two,
Figure BDA0003281860190000194
representing scatterers
Figure BDA0003281860190000195
And the time-varying distance vector between the subscriber terminal antenna unit q,
Figure BDA0003281860190000196
representing client-to-scatterers
Figure BDA0003281860190000197
The horizontal distance of (a) is,
Figure BDA0003281860190000198
representing scatterers
Figure BDA0003281860190000199
The azimuth angle of (a) is,
Figure BDA00032818601900001910
representing scatterers
Figure BDA00032818601900001911
The angle of elevation of (a) is,
Figure BDA00032818601900001912
representing the position vector, v, of the subscriber terminal antenna element qRRepresenting the velocity vector of the user terminal.
Solving for time-varying Doppler shift of scattering components between Unmanned Aerial Vehicle (UAV) antenna unit p and user side antenna unit q
Figure BDA00032818601900001913
The calculation formula is as follows:
Figure BDA00032818601900001914
where λ represents the carrier wavelength.
S53, solving time-varying distances xi between an Unmanned Aerial Vehicle (UAV) antenna unit p, a user side antenna unit q and an intelligent reflection unit (m, n) -thpmn(t) and ξmnq(t), the calculation formula is as follows:
ξpmn(t)＝||dpmn(t)|| (11)；
ξmnq(t)＝||dmnq(t)|| (12)；
wherein ,
Figure BDA00032818601900001915
Figure BDA00032818601900001916
Figure BDA00032818601900001917
wherein ,ξpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, dpmn(t) represents the time-varying distance vector between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unit, dmnq(t) represents a time-varying distance vector between the reflection of the (m, n) -th intelligent reflection unit and the user terminal antenna unit q,
Figure BDA00032818601900001918
representing the position vector of the (M, n) -th intelligent reflection unit, M representing the number of line reflection units of the intelligent reflection surface, M representing the line position index of the intelligent reflection unit, deltaMIndicating the spacing, θ, of adjacent row reflective elements of the intelligent reflective surface IRSIRSIndicating the arrangement direction of the IRS of the intelligent reflecting surface, N indicating the number of the column reflecting units of the intelligent reflecting surface, N indicating the intelligent reflecting sheetColumn position index of element, deltaNIndicating the spacing, xi, of adjacent column reflecting elements of the intelligent reflecting surfaceIRSRIndicating the horizontal distance between the intelligent reflecting surface and the user terminal.
Solving the time-varying Doppler frequency shift f of multipath components between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user side antenna unit q after passing through an (m, n) -th intelligent reflection unitpqmn(t), the calculation formula is as follows:
Figure BDA0003281860190000201
s54 solving scatterers
Figure BDA0003281860190000202
Time varying distance from user terminal antenna unit q
Figure BDA0003281860190000203
The calculation formula is as follows:
Figure BDA0003281860190000204
wherein ,
Figure BDA0003281860190000205
wherein ,
Figure BDA0003281860190000206
representing scatterers
Figure BDA0003281860190000207
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000208
representing a scattering body
Figure BDA0003281860190000209
And the user terminal antenna unit qThe time-varying distance vector of (a),
Figure BDA00032818601900002010
representing client-to-scatterers
Figure BDA00032818601900002011
The horizontal distance of (a) is,
Figure BDA00032818601900002012
representing scatterers
Figure BDA00032818601900002013
The azimuth angle of (a) is,
Figure BDA00032818601900002014
representing scatterers
Figure BDA00032818601900002015
The elevation angle of (c).
Solving for the passing intelligent reflecting surface and scatterer
Figure BDA00032818601900002016
Doppler shift of scattered component
Figure BDA00032818601900002017
The calculation formula is as follows:
Figure BDA00032818601900002018
s6, obtaining a time-varying reflection phase, a time-varying distance and a time-varying Doppler shift through the steps S4 and S5, solving a space-time correlation function based on the assistance of the intelligent reflecting surface IRS, and determining the influence of the intelligent reflecting surface IRS on the channel characteristics of the unmanned aerial vehicle through correlation analysis.
S61, obtaining time-varying reflection phase, time-varying azimuth angle parameter and time-varying elevation angle parameter in the step S4 and the step S5, and solving an intelligent reflector IRS-assisted unmanned aerial vehicle geometric channel space-time correlation function, wherein the calculation formula is as follows:
Figure BDA00032818601900002019
Figure BDA0003281860190000211
Figure BDA0003281860190000212
Figure BDA0003281860190000213
wherein ：
Figure BDA0003281860190000214
Figure BDA0003281860190000215
Figure BDA0003281860190000216
Figure BDA0003281860190000217
wherein ,
Figure BDA0003281860190000218
represents the space-time correlation of the direct component between the unmanned aerial vehicle UAV antenna unit and the user-side antenna unit,
Figure BDA0003281860190000219
represents the space-time correlation of the scattering components between the unmanned aerial vehicle UAV antenna units and the user-side antenna units,
Figure BDA00032818601900002110
represents the space-time correlation of the direct component reflected by the intelligent reflecting surface IRS between the unmanned aerial vehicle UAV antenna unit and the user-side antenna unit,
Figure BDA00032818601900002111
indicating that between the UAV antenna unit and the user side antenna unit via the intelligent reflection surface IRS and scatterer
Figure BDA00032818601900002112
The space-time dependence of the reflected scattered component, t representing the time variable, δTRepresenting the antenna spacing, δ, between the unmanned aerial vehicle UAV antenna unitsRThe antenna spacing between the antenna units at the user terminal is represented, tau represents propagation delay, K represents Rice factor, lambda represents carrier wavelength, pi represents circumferential ratio, and is taken as 3.14 and xipq(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit qp′q′(t + τ) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p 'and the user-side antenna unit q', fpq(t) time varying Doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fp′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 terminal antenna unit q',
Figure BDA0003281860190000221
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure BDA0003281860190000222
The time-varying distance between them,
Figure BDA0003281860190000223
representing scatterers
Figure BDA0003281860190000224
And the time-varying distance between the subscriber-side antenna unit q,
Figure BDA0003281860190000225
representing unmanned aerial vehicle UAV antenna unit p' and scatterers
Figure BDA0003281860190000226
The time-varying distance between them,
Figure BDA0003281860190000227
representing scatterers
Figure BDA0003281860190000228
And the time varying distance between the subscriber side antenna unit q',
Figure BDA0003281860190000229
represents the time-varying doppler shift of the scattering component between the unmanned aerial vehicle UAV antenna unit p and the user-side antenna unit q,
Figure BDA00032818601900002210
represents the time-varying doppler shift of the scattering component between the unmanned aerial vehicle UAV antenna unit p 'and the user-side antenna unit q',
Figure BDA00032818601900002211
representing scatterers
Figure BDA00032818601900002212
The azimuth angle of (a) is,
Figure BDA00032818601900002213
representing scatterers
Figure BDA00032818601900002214
The angle of elevation of (a) is,
Figure BDA00032818601900002215
representing scatterers
Figure BDA00032818601900002216
The probability density function of the azimuth angle,
Figure BDA00032818601900002217
representing scatterers
Figure BDA00032818601900002218
Probability density function of elevation angle of, ξpmn(t) represents the time-varying distance, ξ, of the link between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th intelligent reflection unitmnq(t) represents the time-varying distance, ξ, of the link between the (m, n) -th intelligent reflection unit and the user terminal antenna unit qp′mn(t + τ) represents the time-varying propagation distance, ξ, of the link between unmanned aerial vehicle UAV antenna units p' and (m, n) -th smart reflector unitsmnq′(t + τ) represents the time-varying propagation distance of the link between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q', fpqmn(t) represents the time-varying Doppler shift of the multipath component between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, n) -th intelligent reflection unit, fp′q′mn(t + τ) represents the time-varying Doppler shift of the multipath component between the UAV antenna unit p 'and the user-side antenna unit q' after passing through the (M, N) -th intelligent reflection unit, N represents the number of column reflection units of the intelligent reflection surface IRS, N represents the column position index of the intelligent reflection unit, M represents the number of row reflection units of the intelligent reflection surface IRS, M represents the row position index of the intelligent reflection unit,
Figure BDA00032818601900002219
representing scatterers
Figure BDA00032818601900002220
And the time-varying propagation distance of the link between the subscriber side antenna unit q,
Figure BDA00032818601900002221
representing scatterers
Figure BDA00032818601900002222
And the time-varying propagation distance of the link between the subscriber side antenna unit q',
Figure BDA00032818601900002223
showing multipath components between the UAV antenna unit p and the user side antenna unit q via the intelligent reflector IRS and the scatterer
Figure BDA00032818601900002224
The latter time-varying doppler shift is then,
Figure BDA00032818601900002225
represents multipath components between the UAV antenna unit p 'and the user terminal antenna unit q' via the intelligent reflection surface IRS and the scatterer
Figure BDA00032818601900002226
The time-varying doppler shift of the reflected component,
Figure BDA00032818601900002227
representing scatterers
Figure BDA00032818601900002228
The azimuth angle of (a) is,
Figure BDA00032818601900002229
representing scatterers
Figure BDA00032818601900002230
The angle of elevation of (a) is,
Figure BDA00032818601900002231
representing scatterers
Figure BDA00032818601900002232
The probability density function of the azimuth angle,
Figure BDA00032818601900002233
representing scatterers
Figure BDA00032818601900002234
Exp (-) represents an exponential function, κ represents a scattering environment factor, μ represents the average angle of arrival of the scattered component, I0Representing a Bessel function of zero order, |, representing an absolute value function, βmaxRepresenting the maximum elevation angle of the scatterer.
S62, determining the influence of the intelligent reflecting surface IRS, the number of the intelligent reflecting units and the size of the intelligent reflecting units on the channel statistical characteristics of the unmanned aerial vehicle UAV by using the obtained space-time correlation function.
Fig. 1 is a schematic diagram of a geometric model of an unmanned aerial vehicle with the assistance of an intelligent reflector IRS. In fig. 1, the invention uses a three-dimensional ellipse-cylinder to simulate an intelligent reflecting surface IRS, an 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 local cell can be serviced. The height of the Unmanned Aerial Vehicle (UAV) is obviously higher than that of a ground building, no building is shielded between the UAV and the intelligent reflecting surface IRS, and a direct link is assumed between the UAV and the intelligent reflecting surface IRS.
Fig. 2 is a comparison graph of absolute envelope amplitudes of a conventional unmanned aerial vehicle channel model and an unmanned aerial vehicle channel model based on intelligent reflector IRS assistance in different IRS reflection phases. In fig. 2, the time-varying phase of phase 1 of the IRS reflection unit is: thetamn(t) ═ 0; the time-varying phase of phase 2 of the IRS reflection unit is:
Figure BDA0003281860190000231
wherein ,ξpmn(t) and ξmnq(t) time-varying distances between the unmanned aerial vehicle antenna unit and the intelligent reflection unit and between the user side antenna unit and the intelligent reflection unit respectively; the time-varying phase of the phase 3 of the IRS reflection unit is the optimal reflection phase proposed by the present invention. Fig. 2 shows that the absolute envelope amplitude of the received signal can be significantly increased by using the intelligent reflector IRS, and that the absolute envelope amplitude of the received signal can be enhanced by adjusting the time-varying phase of the intelligent reflector, thereby verifying that the model of the present invention can effectively change the propagation environment between the unmanned aerial vehicle and the receiving end.
FIG. 3 shows the number of different reflection units of the IRS of the intelligent reflection surfaceAbsolute envelope magnitude comparison of bottom. Fig. 4 is a comparison graph of absolute envelope amplitudes of the intelligent reflecting surface IRS in different reflecting unit geometric areas. It can be seen from fig. 3 and 4 that the number of the intelligent reflection units and the geometric area (δ) of the intelligent reflection units are increasedMδN) The absolute envelope amplitude of the received signal can be significantly enhanced.
FIG. 5 is a comparison graph of the channel spatial correlation function of the UAV with different numbers of IRS reflection units on the intelligent reflection surface; from fig. 5 it can be seen that the spatial correlation of the intelligent reflector IRS assisted drone channel model is related to the number of intelligent reflection 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 existing in the unmanned aerial vehicle channel model assisted by the intelligent reflection surface IRS is displayed.
FIG. 6 is a comparison graph of the channel time correlation function of the intelligent reflector IRS assisted unmanned aerial vehicle at different unmanned aerial vehicle movement speeds; it can be seen from fig. 6 that the time correlation function of the channel of the drone is obviously enhanced after the intelligent reflector IRS is adopted.
To sum up, the unmanned aerial vehicle geometric model building method based on the assistance of the intelligent reflector comprises the steps of designing the time-varying reflection phase of the intelligent reflector: the received signal power maximization is taken as a target design optimization problem, and the optimization problem is solved to obtain an optimal time-varying reflection phase; designing time-varying distance parameters: obtaining time-varying distance parameters and time-varying Doppler frequency shift parameters among the unmanned aerial vehicle, the receiving end and the intelligent reflecting surface according to the intelligent reflecting surface assisted geometric model; analyzing the statistical characteristics of the channel: and analyzing the statistical characteristics of the unmanned aerial vehicle MIMO channel model based on the assistance of the intelligent reflector according to the parameters of the time-varying reflection phase and the time-varying distance of the intelligent reflector. 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, therefore, the model establishing method can provide powerful support for the exploration of the key technology of the 6G communication system.

Claims (7)

1. An unmanned aerial vehicle geometric model building method based on assistance of an intelligent reflecting surface is characterized by comprising the following steps:
s1, establishing an unmanned aerial vehicle geometric model based on the assistance of the intelligent reflector IRS according to the position relation among the unmanned aerial vehicle UAV, the intelligent reflector IRS and the receiving end, and obtaining the complex channel gain of a channel;
s2, designing an optimization problem according to an intelligent reflector IRS-assisted unmanned aerial vehicle geometric model based on a received signal power maximization principle;
s3, according to the power of the received signal, mainly focusing on the direct component reflected by the intelligent reflecting surface IRS, simplifying the optimization problem;
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 side and the intelligent reflector IRS;
s6, obtaining a time-varying reflection phase, a time-varying distance and a time-varying Doppler shift through the steps S4 and S5, solving a space-time correlation function based on the assistance of the intelligent reflecting surface IRS, and determining the influence of the intelligent reflecting surface IRS on the channel characteristics of the unmanned aerial vehicle through correlation analysis.
2. The method for building geometric model of unmanned aerial vehicle based on assistance of intelligent reflector according to claim 1, wherein the complex channel gain obtained in step S1 is expressed as follows:
Figure FDA0003281860180000011
wherein ,
Figure FDA0003281860180000012
Figure FDA0003281860180000013
Figure FDA0003281860180000014
Figure FDA0003281860180000015
wherein t represents a time variable, hpq(t) represents the complex channel gain of the multipath component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure FDA0003281860180000016
represents the complex channel gain of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure FDA0003281860180000021
represents the complex channel gain of the scattering component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure FDA0003281860180000022
represents the complex channel gain of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user-side antenna unit q after being reflected by the intelligent reflecting surface IRS,
Figure FDA0003281860180000023
represents the complex channel gain theta of the scattering component between the UAV antenna unit p and the user terminal antenna unit q after being scattered by the intelligent reflector IRS and the scatterermn(t) shows the reflection phase of the Intelligent reflective surface IRS at time t, GtIndicating the originating antenna gain, GrThe gain of the receiving-end antenna is shown,
Figure FDA0003281860180000024
representing the path loss from the unmanned aerial vehicle UAV to the user terminal, K represents the rice factor,
Figure FDA0003281860180000025
representing the path loss from the unmanned aerial vehicle UAV to the intelligent reflector IRS, pi representing the circumferential ratio, lambda representing the carrier wavelength, ξpq(t) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fpq(t) time varying Doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, N1Representing scatterers
Figure FDA0003281860180000026
The number of the (c) component (a),
Figure FDA0003281860180000027
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure FDA0003281860180000028
The time-varying distance between them,
Figure FDA0003281860180000029
representing scatterers
Figure FDA00032818601800000210
And the time-varying distance between the subscriber-side antenna unit q,
Figure FDA00032818601800000211
representing a scattering body
Figure FDA00032818601800000212
Time-varying doppler shift of the scattered component of (xi)pmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the time-varying Doppler shift between the multipath components of the UAV antenna unit p and the user-side antenna unit q after passing through the (m, N) -th intelligent reflection unit, N2Representing scatterers
Figure FDA00032818601800000213
The number of the (c) component (a),
Figure FDA00032818601800000214
expressing (m, n) -th intelligent reflection unit and scatterer
Figure FDA00032818601800000215
The time-varying distance between them,
Figure FDA00032818601800000216
representing scatterers
Figure FDA00032818601800000217
And the time-varying distance between the subscriber-side antenna unit q,
Figure FDA00032818601800000218
showing multipath components between the UAV antenna unit p and the user side antenna unit q via the intelligent reflector IRS and the scatterer
Figure FDA00032818601800000219
The latter time-varying doppler shift.
3. The method for establishing the geometric model of the unmanned aerial vehicle based on the assistance of the intelligent reflecting surface of claim 1, wherein the optimization problem in the step S2 is represented as follows:
Figure FDA00032818601800000220
where t represents a time variable, θmn(t) denotes the reflection phase of the intelligent reflective surface IRS at time t,
Figure FDA00032818601800000221
represents a statistical mean operation, hpq(t) shows unmanned aerial vehicle UAV antenna unit p and user sideThe complex channel gain of the multipath components between the antenna elements q.
4. The method for building geometric model of unmanned aerial vehicle based on assistance of intelligent reflector according to claim 1, wherein step S3 comprises the following steps:
s31, considering the concentrated received signal power, simplifying the optimization problem of step S1, the simplified formula is as follows:
Figure FDA0003281860180000031
wherein ,
Figure FDA0003281860180000032
Figure FDA0003281860180000033
Figure FDA0003281860180000034
Figure FDA0003281860180000035
Figure FDA0003281860180000036
Figure FDA0003281860180000037
Figure FDA0003281860180000038
Figure FDA0003281860180000039
wherein ,
Figure FDA00032818601800000310
representing a statistical mean operation, t represents a time variable,
Figure FDA00032818601800000311
and
Figure FDA00032818601800000312
representing an auxiliary variable, cos (-) representing a cosine function,
Figure FDA00032818601800000313
representing the time-varying phase of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure FDA0003281860180000041
represents the time-varying phase of the multipath component between the UAV antenna unit p and the user terminal antenna unit q after passing through the (m, N) -th intelligent reflection unit, N1Representing scatterers
Figure FDA0003281860180000042
The number of the (c) component (a),
Figure FDA0003281860180000043
represents multipath components between the UAV antenna unit p and the user-side antenna unit q via scatterers
Figure FDA0003281860180000044
The phase of the latter time-varying phase,
Figure FDA0003281860180000045
the time-varying phase of multipath components between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user side antenna unit q after passing through an (M ', N') -th intelligent reflection unit is represented, M represents the number of IRS row reflection units of an intelligent reflection surface, N represents the number of IRS column reflection units of the intelligent reflection surface, pi represents a circumferential ratio, lambda represents a carrier wavelength, and xi representspq(t) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fpq(t) represents the time-varying doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure FDA0003281860180000046
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure FDA0003281860180000047
The time-varying distance between them,
Figure FDA0003281860180000048
representing scatterers
Figure FDA0003281860180000049
And the time-varying distance between the subscriber-side antenna unit q,
Figure FDA00032818601800000410
representing a scattering body
Figure FDA00032818601800000411
Time-varying doppler shift of the scattered component of (xi)pmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents the time-varying Doppler shift, theta, of multipath components between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, n) -th intelligent reflection unitmn(t) represents the time-varying reflection phase, G, of the (m, n) -th intelligent reflection unittIndicating the originating antenna gain, GrThe gain of the receiving-end antenna is shown,
Figure FDA00032818601800000412
representing the path loss from the unmanned aerial vehicle UAV to the user terminal, K represents the rice factor,
Figure FDA00032818601800000413
representing the path loss, δ, of the UAV to the IRSMRepresenting the antenna spacing, δ, of adjacent row reflector elementsNThe antenna spacing adjacent to the column reflection unit is shown;
s32, assuming the auxiliary variable is
Figure FDA00032818601800000414
And
Figure FDA00032818601800000415
wherein
Figure FDA00032818601800000416
And assuming a time-varying reflection phase of the intelligent reflection surface as
Figure FDA00032818601800000417
The optimization problem is further simplified as follows:
Figure FDA00032818601800000418
wherein ,
Figure FDA00032818601800000419
and
Figure FDA00032818601800000420
both represent auxiliary variables.
5. The smart reflex-based according to claim 1The surface-assisted unmanned aerial vehicle geometric model building method is characterized in that the optimal intelligent reflecting surface IRS reflection phase theta obtained in the step S4mn(t) is represented by the following formula:
Figure FDA0003281860180000051
wherein ,
Figure FDA0003281860180000052
Figure FDA0003281860180000053
Figure FDA0003281860180000054
where π denotes the circumference ratio, λ denotes the carrier wavelength, t denotes the time variable, ξpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, fpqmn(t) represents a time-varying Doppler shift of the reflection component via the (m, n) -th smart reflective element,
Figure FDA0003281860180000055
representing an auxiliary variable, sgn (·) representing a sign function, arctan (·) representing an arctangent function, χARepresenting an auxiliary variable, χBThe auxiliary variable is represented by a number of variables,
Figure FDA0003281860180000056
representing an auxiliary variable, cos (-) representing a cosine function,
Figure FDA0003281860180000057
representing the time-varying phase between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q, sin (-) represents a sinusoidal function,
Figure FDA0003281860180000058
the auxiliary variable is represented by a number of variables,
Figure FDA0003281860180000059
represents multipath components between the UAV antenna unit p and the user-side antenna unit q via scatterers
Figure FDA00032818601800000510
The phase of the latter time-varying phase,
Figure FDA00032818601800000511
representing scatterers
Figure FDA00032818601800000512
The azimuth angle of (a) is,
Figure FDA00032818601800000513
representing scatterers
Figure FDA00032818601800000514
The angle of elevation of (a) is,
Figure FDA00032818601800000515
a function representing the probability density of the azimuth,
Figure FDA00032818601800000516
representing the elevation probability density function.
6. The method for building geometric model of unmanned aerial vehicle based on assistance of intelligent reflector according to claim 1, wherein step S5 comprises the following steps:
s51, solving the time-varying distance from the UAV antenna unit p to the user terminal antenna unit qξpq(t), the calculation formula is as follows:
ξpq(t)＝||dpq(t)|| (6)；
wherein ,
Figure FDA0003281860180000061
Figure FDA0003281860180000062
Figure FDA0003281860180000063
Figure FDA0003281860180000064
vR＝vR[cosγR,sinγR,0]；
wherein, | | · | | represents norm operation, t represents time variable, ξpq(t) represents the time varying distance between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, dpq(t) represents the time-varying distance vector between the unmanned aerial vehicle UAV antenna unit p and the user terminal antenna unit q,
Figure FDA0003281860180000065
representing the position vector of the unmanned aerial vehicle UAV antenna unit p, NTRepresenting the number of UAV antenna units, p represents the UAV antenna unit position index, δTRepresents the spacing, theta, of adjacent antenna units of the unmanned aerial vehicle UAVTRepresenting the unmanned aerial vehicle UAV antenna unit direction, sin (·) representing a sine function, cos (·) representing a cosine function, tan (·) representing a tangent function, ξTRRepresents the horizontal distance, θ, of the unmanned aerial vehicle UAV and the user terminalTRIndicating the direction, beta, of the unmanned aerial vehicle UAV antenna unit relative to the user sideTRTo indicate nobodyThe elevation angle of the aerial unit of the aerial UAV relative to the user's end,
Figure FDA0003281860180000066
representing the location vector of the subscriber terminal antenna unit q, NRRepresenting the number of antenna units at the subscriber end, q representing the index of the location of the antenna units at the subscriber end, deltaRRepresents the distance between adjacent antenna units at the user end, thetaRIndicating the direction of the antenna unit at the subscriber end, vTRepresenting unmanned aerial vehicle UAV velocity vector, vRRepresenting the velocity vector, v, of the user terminalTRepresenting the magnitude of the unmanned aerial vehicle UAV velocity,
Figure FDA0003281860180000067
elevation angle, gamma, representing the direction of movement of an Unmanned Aerial Vehicle (UAV)TIndicating the direction of the unmanned aerial vehicle UAV movement, vRIndicates the velocity of the user terminal, gammaRRepresenting the moving direction azimuth of the user terminal;
solving for a time-varying Doppler shift f of the direct component between an Unmanned Aerial Vehicle (UAV) antenna unit p and a user-side antenna unit qpq(t), the calculation formula is as follows:
Figure FDA0003281860180000068
wherein λ represents a carrier wavelength;
s52, solving the problem that the UAV antenna unit p and the user-side antenna unit q are respectively connected to scatterers
Figure FDA0003281860180000069
Time-varying distance of
Figure FDA00032818601800000610
And
Figure FDA00032818601800000611
the calculation formula is as follows:
Figure FDA0003281860180000071
Figure FDA0003281860180000072
wherein ,
Figure FDA0003281860180000073
Figure FDA0003281860180000074
wherein ,
Figure FDA0003281860180000075
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure FDA0003281860180000076
The time-varying distance between them,
Figure FDA0003281860180000077
representing scatterers
Figure FDA0003281860180000078
And the time-varying distance between the subscriber-side antenna unit q,
Figure FDA0003281860180000079
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure FDA00032818601800000710
A time-varying distance vector between the two,
Figure FDA00032818601800000711
representing scatterers
Figure FDA00032818601800000712
And the time-varying distance vector between the subscriber terminal antenna unit q,
Figure FDA00032818601800000713
representing client-to-scatterers
Figure FDA00032818601800000714
The horizontal distance of (a) is,
Figure FDA00032818601800000715
representing scatterers
Figure FDA00032818601800000716
The azimuth angle of (a) is,
Figure FDA00032818601800000717
representing scatterers
Figure FDA00032818601800000718
Elevation angle of (d);
through scattering body
Figure FDA00032818601800000719
Time-varying Doppler shift of scattered component
Figure FDA00032818601800000720
The calculation formula is as follows:
Figure FDA00032818601800000721
wherein λ represents a carrier wavelength;
s53, solving time-varying distances xi between an Unmanned Aerial Vehicle (UAV) antenna unit p, a user side antenna unit q and an intelligent reflection unit (m, n) -thpmn(t) and ξmnq(t), the calculation formula is as follows:
ξpmn(t)＝||dpmn(t)|| (11)；
ξmnq(t)＝||dmnq(t)|| (12)；
wherein ,
Figure FDA00032818601800000722
Figure FDA00032818601800000723
Figure FDA00032818601800000724
wherein ,ξpmn(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unitmnq(t) represents the time-varying distance between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q, dpmn(t) represents the time-varying distance vector between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th smart reflector unit, dmnq(t) represents a time-varying distance vector between the reflection of the (m, n) -th intelligent reflection unit and the user terminal antenna unit q,
Figure FDA0003281860180000081
representing the position vector of the (M, n) -th intelligent reflection unit, M representing the number of line reflection units of the intelligent reflection surface, M representing the line position index of the intelligent reflection unit, deltaMIndicating the spacing, θ, of adjacent row reflective elements of the intelligent reflective surface IRSIRSIndicating the arrangement direction of the intelligent reflecting surface IRS, N indicating the number of column reflecting units of the intelligent reflecting surface, N indicating the column position index of the intelligent reflecting units, deltaNIndicating the spacing, xi, of adjacent column reflecting elements of the intelligent reflecting surfaceIRSRRepresenting the horizontal distance between the intelligent reflecting surface and the user side;
solving for (m, n) -th intelligent reflection unit reflection componentTime varying Doppler shift fpqmn(t), the calculation formula is as follows:
Figure FDA0003281860180000082
s54 solving scatterers
Figure FDA0003281860180000083
Time varying distance from user terminal antenna unit q
Figure FDA0003281860180000084
The calculation formula is as follows:
Figure FDA0003281860180000085
wherein ,
Figure FDA0003281860180000086
wherein ,
Figure FDA0003281860180000087
representing scatterers
Figure FDA0003281860180000088
And the time-varying distance between the subscriber-side antenna unit q,
Figure FDA0003281860180000089
representing a scattering body
Figure FDA00032818601800000810
And the time-varying distance vector between the subscriber terminal antenna unit q,
Figure FDA00032818601800000811
for indicatingClient-to-scatterer
Figure FDA00032818601800000812
The horizontal distance of (a) is,
Figure FDA00032818601800000813
representing scatterers
Figure FDA00032818601800000814
The azimuth angle of (a) is,
Figure FDA00032818601800000815
representing scatterers
Figure FDA00032818601800000816
Elevation angle of (d);
solving for the passing intelligent reflecting surface and scatterer
Figure FDA00032818601800000817
Doppler shift of scattered component
Figure FDA00032818601800000818
The calculation formula is as follows:
Figure FDA00032818601800000819
7. the method for building geometric model of unmanned aerial vehicle based on assistance of intelligent reflector according to claim 1, wherein step S6 comprises the following steps:
s61, solving the space-time correlation function of the geometrical channel of the unmanned aerial vehicle assisted by the intelligent reflector IRS by using the time-varying parameters obtained in the steps S3 and S4, wherein the calculation formula is as follows:
Figure FDA00032818601800000820
Figure FDA0003281860180000091
Figure FDA0003281860180000092
Figure FDA0003281860180000093
wherein ：
Figure FDA0003281860180000094
Figure FDA0003281860180000095
Figure FDA0003281860180000096
Figure FDA0003281860180000097
wherein ,
Figure FDA0003281860180000098
represents the space-time correlation of the direct component between the unmanned aerial vehicle UAV antenna unit and the user-side antenna unit,
Figure FDA0003281860180000099
represents the space-time correlation of the scattering components between the unmanned aerial vehicle UAV antenna units and the user-side antenna units,
Figure FDA00032818601800000910
represents the space-time correlation of the direct component reflected by the intelligent reflecting surface IRS between the unmanned aerial vehicle UAV antenna unit and the user-side antenna unit,
Figure FDA00032818601800000911
indicating that between the UAV antenna unit and the user side antenna unit via the intelligent reflection surface IRS and scatterer
Figure FDA00032818601800000912
The space-time dependence of the reflected scattered component, t representing the time variable, δTRepresenting the antenna spacing, δ, between the unmanned aerial vehicle UAV antenna unitsRThe antenna spacing between the antenna units at the user terminal is represented, tau represents propagation delay, K represents Rice factor, lambda represents carrier wavelength, pi represents circumferential ratio, and xipq(t) represents the time-varying distance, ξ, between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit qp′q′(t + τ) represents the time-varying distance between the unmanned aerial vehicle UAV antenna unit p 'and the user-side antenna unit q', fpq(t) time varying Doppler shift of the direct component between the unmanned aerial vehicle UAV antenna unit p and the user side antenna unit q, fp′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 terminal antenna unit q',
Figure FDA0003281860180000101
representing unmanned aerial vehicle UAV antenna unit p and scatterers
Figure FDA0003281860180000102
The time-varying distance between them,
Figure FDA0003281860180000103
representing scatterers
Figure FDA0003281860180000104
And the time-varying distance between the subscriber-side antenna unit q,
Figure FDA0003281860180000105
representing unmanned aerial vehicle UAV antenna unit p' and scatterers
Figure FDA0003281860180000106
The time-varying distance between them,
Figure FDA0003281860180000107
representing scatterers
Figure FDA0003281860180000108
And the time varying distance between the subscriber side antenna unit q',
Figure FDA0003281860180000109
represents the time-varying doppler shift of the scattering component between the unmanned aerial vehicle UAV antenna unit p and the user-side antenna unit q,
Figure FDA00032818601800001010
represents the time-varying doppler shift of the scattering component between the unmanned aerial vehicle UAV antenna unit p 'and the user-side antenna unit q',
Figure FDA00032818601800001011
representing scatterers
Figure FDA00032818601800001012
The azimuth angle of (a) is,
Figure FDA00032818601800001013
representing scatterers
Figure FDA00032818601800001014
The angle of elevation of (a) is,
Figure FDA00032818601800001015
representing scatterers
Figure FDA00032818601800001016
The probability density function of the azimuth angle,
Figure FDA00032818601800001017
representing scatterers
Figure FDA00032818601800001018
Probability density function of elevation angle of, ξpmn(t) represents the time-varying distance, ξ, of the link between the unmanned aerial vehicle UAV antenna units p and the (m, n) -th intelligent reflection unitmnq(t) represents the time-varying distance, ξ, of the link between the (m, n) -th intelligent reflection unit and the user terminal antenna unit qp′mn(t + τ) represents the time-varying propagation distance, ξ, of the link between unmanned aerial vehicle UAV antenna units p' and (m, n) -th smart reflector unitsmnq′(t + τ) represents the time-varying propagation distance of the link between the (m, n) -th intelligent reflection unit and the user terminal antenna unit q', fpqmn(t) represents the time-varying Doppler shift of the multipath component between the UAV antenna unit p and the user-side antenna unit q after passing through the (m, n) -th intelligent reflection unit, fp′q′mn(t + τ) represents the time-varying Doppler shift of the multipath component between the UAV antenna unit p 'and the user-side antenna unit q' after passing through the (M, N) -th intelligent reflection unit, N represents the number of column reflection units of the intelligent reflection surface IRS, N represents the column position index of the intelligent reflection unit, M represents the number of row reflection units of the intelligent reflection surface IRS, M represents the row position index of the intelligent reflection unit,
Figure FDA00032818601800001019
representing scatterers
Figure FDA00032818601800001020
And the time-varying propagation distance of the link between the subscriber side antenna unit q,
Figure FDA00032818601800001021
representing scatterers
Figure FDA00032818601800001022
And the time-varying propagation distance of the link between the subscriber side antenna unit q',
Figure FDA00032818601800001023
showing multipath components between the UAV antenna unit p and the user side antenna unit q via the intelligent reflector IRS and the scatterer
Figure FDA00032818601800001024
The latter time-varying doppler shift is then,
Figure FDA00032818601800001025
represents multipath components between the UAV antenna unit p 'and the user terminal antenna unit q' via the intelligent reflection surface IRS and the scatterer
Figure FDA00032818601800001026
The time-varying doppler shift of the reflected component,
Figure FDA00032818601800001027
representing scatterers
Figure FDA00032818601800001028
The azimuth angle of (a) is,
Figure FDA00032818601800001029
representing scatterers
Figure FDA00032818601800001030
The angle of elevation of (a) is,
Figure FDA00032818601800001031
representing scatterers
Figure FDA00032818601800001032
Probability density of azimuthThe function of the function is that of the function,
Figure FDA00032818601800001033
representing scatterers
Figure FDA00032818601800001034
Exp (-) represents an exponential function, κ represents a scattering environment factor, μ represents the average angle of arrival of the scattered component, I0Representing a Bessel function of zero order, |, representing an absolute value function, βmaxRepresents the maximum elevation angle of the scatterer;
s62, determining the influence of the intelligent reflecting surface IRS, the number of the intelligent reflecting units and the size of the intelligent reflecting units on the channel statistical characteristics of the unmanned aerial vehicle UAV by using the obtained space-time correlation function.
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