CN114124262B - Broadband high-altitude platform channel model building method based on intelligent reflecting surface - Google Patents
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Abstract
The invention discloses a broadband high-altitude platform channel model building method based on an intelligent reflecting surface, which comprises the following steps: s1, establishing a broadband high-altitude platform channel model based on an intelligent reflecting surface, and obtaining complex channel gain of the channel model; s2, designing an optimization problem based on the reflection phase of the reflection unit in the intelligent reflection surface; s3, simplifying the optimization problem into a reflection phase when the reflection component of the intelligent reflection unit in the intelligent reflection surface IRS is maximum; s4, obtaining an optimal intelligent reflection surface IRS time-varying reflection phase; s5, determining time-varying parameters among the high-altitude platform, the user side and the intelligent reflection surface IRS; s6, solving a space-time correlation function of the broadband high-altitude platform channel model based on the intelligent reflection surface, and determining the influence of the intelligent reflection surface IRS on the high-altitude platform channel characteristic through correlation analysis. The invention can provide powerful support for exploring key technologies of the 6G communication system.
Description
Technical Field
The invention relates to a wireless communication technology, in particular to a broadband high-altitude platform channel model building method based on an intelligent reflecting surface.
Background
As users become more interested in having more demanding services, current technology is difficult to meet increasing data demands, such as virtual reality, autopilot, haptic internet, etc., scientists and researchers are looking for new and innovative ways to provide wireless communication services. One of the more likely methods is to use a High Altitude Platform (HAP). High-altitude platform communication has larger coverage and flexibility.
It should be noted that the communication environment between the aerial platform and the client is filled with uncontrollable variables that interfere with the system quality of the aerial platform communication system. The intelligent reflection surface IRS is composed of a plurality of antenna units capable of adjusting amplitude, phase and frequency, and has the capability of controlling the communication environment between a transmitting end and a user end.
The intelligent reflection surface IRS is composed of units with adjustable amplitude, phase and frequency, and can control the propagation environment between the transmitting end and the user end. There are already documents that can demonstrate: IRSs with adjustable phase and frequency can eliminate or mitigate doppler effects and multipath fading phenomena caused by mobile subscriber side motion.
As a new and potentially powerful technology, the challenge to be faced is to study the application of intelligent reflector IRS in high-altitude platform communication systems. Proper channel modeling can provide basis for future system performance analysis and coding algorithm design.
In combination with the above description, the establishment of the channel model of the high-altitude platform based on the intelligent reflection surface is in the beginning stage, and the statistical characteristics of the IRS of the intelligent reflection surface to the high-altitude platform also needs to be further studied. Therefore, it is necessary for the present invention to model the channel of the high-altitude platform based on the intelligent reflection surface IRS, and the establishment of the model can provide basis for future system performance analysis and coding algorithm design.
Disclosure of Invention
The invention aims to: the invention aims to provide a broadband high-altitude platform channel model building method based on an intelligent reflecting surface.
The technical scheme is as follows: the invention discloses a broadband high-altitude platform channel model building method based on an intelligent reflecting surface, which comprises the following steps:
s1, taking the surrounding of a user terminal Rx and the propagation environments around an intelligent reflection surface IRS and an overhead platform Tx into consideration, adopting a three-dimensional multi-cylinder to represent a scatterer around the user terminal, adopting a three-dimensional multi-ellipse-cylinder to represent the scatterer between the overhead platform Tx and the intelligent reflection surface IRS, establishing a broadband overhead platform channel model based on the intelligent reflection surface, and obtaining the complex channel gain of the channel model;
s2, in order to improve the communication quality to the greatest extent so as to achieve the optimal received signal power, and based on the principle, according to a broadband high-altitude platform channel model based on the intelligent reflecting surface, adopting statistical mean value operation to design an optimization problem based on the reflecting phase of a reflecting unit in the intelligent reflecting surface;
S3, because the reflection component of the intelligent reflection unit in the intelligent reflection surface IRS in the channel model accounts for the main part of the complex channel gain of the model, the evaluation of the optimal time-varying reflection phase of the intelligent reflection surface IRS is simplified into a reflection phase when the reflection component of the intelligent reflection unit in the intelligent reflection surface IRS is maximum;
s4, according to the harmonic addition theorem, obtaining the optimal IRS time-varying reflection phase of the intelligent reflection surface;
s5, determining time-varying parameters among the high-altitude platform Tx, the user terminal Rx, the intelligent reflection surface IRS and the scatterer according to the motion conditions of the high-altitude platform and the user terminal, wherein the time-varying parameters comprise the high-altitude platform Tx and the scattererUser terminal Rx and scatterer->Intelligent reflector IRS and diffuser->And user side Rx and diffuser->Time-varying azimuth and time-varying elevation parameters in between;
s6, solving a space-time correlation function based on a broadband high-altitude platform channel model of the intelligent reflection surface through the optimal IRS time-varying reflection phase of the intelligent reflection surface obtained in the step S4 and the time-varying parameters obtained in the step S5, and determining the influence of the IRS of the intelligent reflection surface on the high-altitude platform channel characteristic through correlation analysis.
Further, the intelligent reflection-based method obtained in step S1 Complex channel gain h of wideband high-altitude platform channel model of face pq,uw The calculation formula of (t) is:
wherein t represents a time variable, L represents the number of times of a total tap, L represents the first tap, c l Indicating the gain effect brought about by the first tap,complex channel gain representing scattered components of high altitude platform (q, p) -th antenna element and user (w, u) -th antenna element at the first tap, < >>Representing complex channel gain reflected by an intelligent reflection surface IRS between an aerial platform (q, p) -th and a user side (w, u) -th antenna unit at the first tap;Representing complex channel gain of direct component of aerial platform antenna unit (q, p) -th and user (w, u) -th antenna unit after being reflected by intelligent reflection surface IRS when first tap, and>representing the complex channel gain of the scattered component of the (q, p) -th antenna element after reflection by the IRS and the scatterer at the first tap.
Further, the optimization problem in step S2 is expressed as follows:
wherein t represents a time variable, θ mn (t) represents the smart reflective surface IRS time-varying reflection phase,represents statistical mean operation, h pq,uw (t) represents the complex channel gain of the intelligent reflector-based wideband high altitude platform channel model.
Further, in step S3, the complex channel gain in step S1 is brought into the optimization problem in step S2, and the optimization problem is further expressed as:
wherein ,θmn (t) represents the smart reflective surface IRS time-varying reflection phase,representing statistical mean operations, L representing the number of times a total of taps, L representing the first tap, c l Indicating the gain effect brought about by the first tap, t indicating the time variable, (-)>Complex channel gain representing scattered components of high altitude platform (q, p) -th antenna element and user (w, u) -th antenna element at the first tap, < >>And the complex channel gain reflected by the intelligent reflection surface IRS between the aerial platform (q, p) -th and the user side (w, u) -th antenna unit at the first tap is represented.
Furthermore, the signal complex channel gain is mainly governed by a single-hop component SB of the intelligent reflection unit, the influence of a double-hop component DB is ignored, and the optimization problem is simplified as follows:
wherein ,representing high-altitude platform (q, p) -th antenna element and user (w, u) -th antennaComplex channel gain of unit scatter component, +.>Representing complex channel gains of direct components of the high-altitude platform antenna units (q, p) -th and the user (w, u) -th antenna units after being reflected by the intelligent reflection surface IRS;
based on the complex exponential nature, the above problem is again expressed as:
wherein Nl,1 Representing scatterersNumber n of (2) l,1 Represents the nth l,1 Individual scatterers (a-> andRepresenting the auxiliary variables, cos (·) representing the cosine function, >Representing the scattered body between the first tap high-altitude platform antenna element and the user antenna element +.>Later time-varying phase,/->Representing the time-varying phase of the direct component between the 1 st tap high altitude platform antenna unit and the user antenna unit after passing through the (m, n) -th intelligent reflection unit, +.>Representing the passing between the 1 st tap high altitude platform antenna unit and the user antenna unit(m ', n') -th the time-varying phase of the direct component after reflection by the smart reflection unit;
according to formula (5)It can be seen that->And->When constant and equal, +.>Taking the maximum value;
wherein The specific expression is:
wherein ,the time-varying phase of direct component between the 1 st tap high-altitude platform antenna unit and the user antenna unit after passing through the (m, n) -th intelligent reflecting unit is represented, pi represents the circumference ratio, lambda represents the carrier wavelength, and xi pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element, f IRSR (t) time-varying Doppler shift of the intelligent reflection surface IRS reaching the user terminal Rx, f IRST (t) represents the time-varying Doppler shift of the arrival of the transmitting end Rx at the intelligent reflection surface IRS.
Further, the step S4 specifically includes:
assuming that the auxiliary variable is andAnd assume that the optimal intelligent reflection surface IRS time-varying reflection phase isWherein make->Wherein pi represents the circumference ratio, t represents the time variable, lambda represents the carrier wavelength, and ζ pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element, f IRST (t) time-varying Doppler shift, f, of the high altitude platform Tx reaching the intelligent reflective surface IRS IRSR (t) represents the time-varying doppler shift of the intelligent reflection surface IRS to the user Rx;
at this time, the liquid crystal display device,the solution problem for the optimal reflection phase is expressed as:
wherein ,representing statistical mean operations, L representing the number of times a total of taps, L representing the first tap, N l,1 Representing scatterer->Number n of (2) l,1 Represents the nth l,1 Individual scatterers (a-> andRepresenting auxiliary variables +.>Representing the scattered body between the first tap high-altitude platform antenna element and the user antenna element +.>The time-varying phase of the latter is,representing azimuthal probability density function, +.>Representing elevation probability density function, ++>Representing from->Arrive at the user end azimuth after scattering, +.>Representing from- >The scattered elevation angle reaches the user side;
according to the harmonic addition theorem, in order to reach the maximum value of the equation, it is necessary to ensure that:
wherein sgn (·) represents the sign function, χ A and χB Represents an auxiliary variable, cos (·) represents a cosine function, tan -1 (. Cndot.) represents the inverse of the tangent function;
at this timeExpressed as:
wherein pi represents the circumference ratio;
the optimal smart reflector IRS time-varying reflection phase is expressed as follows:
wherein ,indicating the optimal smart reflector IRS time-varying reflection phase.
Further, the step S5 specifically includes:
high altitude platform and scattererThe time-varying azimuth angle between:
wherein ,representing a high-altitude platform and scatterers->Time-varying azimuth angle between, t represents time variable, delta 1 Represents an auxiliary variable, pi represents a circumference ratio, < +.>Representing scatterer->An ordinate in the coordinate system;
high altitude platform and scattererThe time-varying elevation angle between:
wherein ,representing a high-altitude platform and scatterers->Time-varying elevation angle in between, t represents time variable, arctan (·) represents inverse of tangent function, H T Represents the height of the high-altitude platform, H R Indicating the height of the user side, R indicates the diffuser +.>Distance between projection and user side, +.>Representing scatterer->Elevation angle relative to the user side- >Representing the scattering body around the high-altitude platform and the user side->Time-varying distances between projections of (a);
user terminal and scattererThe time-varying azimuth angle between:
wherein ,representing user side and diffuser->Time-varying azimuth angle between, t represents time variable, delta 2 Represents an auxiliary variable, pi represents a circumference ratio, < +.>Representing scatterer->An ordinate in the coordinate system;
high altitude platform and scattererThe time-varying elevation angle between:
wherein ,representing user side and diffuser->Time-varying elevation angle in between, t represents the time variable, arctan (·) represents the inverse of the tangent function, R represents the scatterer +.>Distance between projection and user side, +.>Representing scatterer->Elevation angle relative to the user side->Representing the scattering body around the high-altitude platform and the user side->Time-varying distances between projections of (a);
intelligent reflector IRS and scattererThe time-varying azimuth angle between:
wherein ,representing intelligent reflector IRS and diffuser->Time-varying azimuth angle between, t represents time variable, delta 4 Represents an auxiliary variable, pi represents a circumference ratio, < +.>Representing scatterer->An ordinate in the coordinate system;
intelligent reflector IRS and scattererThe time-varying elevation angle between:
wherein ,representing intelligent reflector IRS and diffuser- >Time-varying elevation angle therebetween, arctan (·) represents the inverse of the tangent function, H IRS Indicating the height of the intelligent reflection surface IRS, H R Representing the height of the user side Rx +.>Representing scatterer->Distance between projection of the user side Rx, tan (. Cndot.) represents tangent function,/-, etc.>Representing scatterer->Elevation angle relative to the user side Rx->Representing the high altitude platform Tx and scatterer->Time-varying distances between projections of (a);
user terminal Rx and scattererTime-varying betweenThe azimuth angle is:
wherein ,representing the user side Rx and scatterer->Time-varying azimuth angle, delta 5 Representing the auxiliary variable; user terminal Rx and diffuser->The time-varying elevation angle between:
wherein ,representing the user side Rx and scatterer->Time-varying elevation angle between->Representing scatterer->Distance between projection to the user side Rx, < >>Representing the user side Rx and scatterer->Time-varying distance between projections, < >>Representing the user side Rx and scatterer->Elevation angle between.
Further, the step S6 specifically includes:
s61, solving a space-time correlation function of a broadband high-altitude platform channel model based on the intelligent reflection surface IRS through the optimal intelligent reflection surface IRS time-varying reflection phase obtained in the step S4 and the time-varying function obtained in the step S5, wherein the calculation formula is as follows:
wherein ,ρ1,pq,uw,p′q′,u′w′ (t,d P ,d Q ,d U ,d W ) Represents h at tap 1 pq,uw(t) and hp'q',u'w' (t) a spatio-temporal correlation function between,a spatio-temporal correlation function representing the scattering component between Rx and Tx at tap 1,A spatio-temporal correlation function representing the direct component reflected by IRS between Rx and Tx at tap 1,Representing the spatio-temporal correlation function of the scattered components between Rx and Tx at tap 1, through IRS and scatterer reflection, ρ l,pq,uw,p′q′,u′w′ (t,d P ,d Q ,d U ,d W ) Represents h at the first tap pq,uw(t) and hp'q',u'w' (t) a spatiotemporal correlation function between +.>Representing the spatio-temporal correlation function of the scattering component between Rx and Tx at the first tap, +.>A space-time correlation function representing the scattered component between Rx and Tx at the first tap via IRS and scatterer reflection; h is a pq,uw (t) represents the complex channel gain between the (q, p) -th antenna element and the (w, u) -th antenna element, h p'q',u'w' (t) represents the complex channel gain, d, between the (q ', p') -th antenna element and the (w ', u') -th antenna element P and dQ Representing the difference in the abscissas of two antenna elements (q, p) and (q ', p') in the high-altitude platform, d U and dW Representing the difference between the abscissas of the two antenna elements (w, u) and (w ', u') at the user end, respectively;
s62, determining the influence of the intelligent reflection surface IRS, the number of the intelligent reflection units and the size of the intelligent reflection units on the channel statistical characteristics of the high-altitude platform by using the space-time correlation function obtained in the step S61;
The intelligent reflection surface IRS and the intelligent reflection unit number are increased, and the intelligent reflection unit size is increased, so that the multipath fading phenomenon can be effectively reduced; the degree of reduction in the spatial-temporal correlation decreases as the number of intelligent reflective surfaces IRS, intelligent reflective units increases, and the size of the intelligent reflective units increases.
In another embodiment of the invention, an apparatus comprises a memory and a processor, wherein:
a memory for storing a computer program capable of running on the processor;
and the processor is used for executing the steps of the intelligent reflection surface-based broadband high-altitude platform channel model building method when the computer program is run.
In yet another embodiment of the present invention, a storage medium has a computer program stored thereon, which when executed by at least one processor implements the steps of the smart reflector-based wideband aerial platform channel model building method described above.
The beneficial effects are that: compared with the prior art, the method for establishing the broadband high-altitude platform channel model based on the intelligent reflection surface takes the influence of the IRS of the intelligent reflection surface on the broadband high-altitude platform channel characteristic into consideration, takes the optimal reflection phase into consideration under the received signal power maximization principle, and adopts time-varying parameters to describe the broadband high-altitude platform channel characteristic; meanwhile, the invention considers the influence of the number and the size of IRS reflecting units of the intelligent reflecting surface on the Doppler frequency shift and the multipath fading phenomenon of the broadband high-altitude platform channel; therefore, the invention can better explore the influence of the IRS of the intelligent reflecting surface on the channel statistics characteristics of the broadband high-altitude platform. The modeling method can provide powerful support for exploring key technologies of the 6G communication system.
Drawings
FIG. 1 is a schematic diagram of a broadband high-altitude platform channel model based on an intelligent reflection surface;
FIG. 2 is a graph showing the comparison of absolute envelope amplitudes at different reflection phases of an intelligent reflection surface IRS;
FIG. 3 is a graph showing the comparison of absolute envelope magnitudes for different numbers of reflective units of an intelligent reflective surface IRS;
FIG. 4 is a graph comparing the received spatial correlation functions for different numbers of reflective units of the intelligent reflective surface IRS;
fig. 5 is a graph comparing the received spatial correlation functions for different numbers of reflection units of the intelligent reflection surface IRS.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
The invention adopts the intelligent reflection surface IRS to control the propagation environment of the high-altitude platform, considers the optimal received signal power, and obtains the optimal IRS reflection phase of the intelligent reflection surface; the capability of the intelligent reflection surface IRS for changing the propagation environment of the high-altitude platform channel is considered, namely the influence of the number of the intelligent reflection surface IRS reflection units and the sizes of the reflection units on the statistical characteristics of the high-altitude platform channel; the influence of the intelligent reflection surface IRS on the statistical characteristics of the high-altitude platform channel is explored by taking the high-altitude platform channel assisted by the intelligent reflection surface IRS into consideration, and a basis is better provided for system performance analysis and precoding algorithm design in the future.
The invention discloses a broadband high-altitude platform channel model building method based on an intelligent reflecting surface, which comprises the following steps:
s1, considering the capability of the intelligent reflection surface IRS for changing the channel propagation environment, namely the intelligent reflection surface IRS has the effects of reducing multipath fading and improving signal strength, and the intelligent reflection surface IRS is applied to a communication scene of a high-altitude platform. Taking the surrounding of the user end Rx and the propagation environments of the intelligent reflection surface IRS and the surrounding of the high-altitude platform Tx into consideration, respectively adopting a three-dimensional multi-cylinder and a three-dimensional multi-ellipse-cylinder to establish a broadband high-altitude platform channel model based on the intelligent reflection surface, and obtaining the complex channel gain of the model.
The established broadband high-altitude platform channel model based on the intelligent reflecting surface is shown in fig. 1, wherein a three-dimensional multi-cylinder represents a scatterer around a user terminal, a three-dimensional multi-ellipse-cylinder represents the scatterer between the intelligent reflecting surface IRS and the high-altitude platform Tx, and the model takes the propagation environments around the user terminal Rx and the intelligent reflecting surface IRS and the user terminal Rx into consideration, and is modeled by adopting the three-dimensional multi-cylinder and the three-dimensional multi-ellipse-cylinder respectively. The invention adopts a three-dimensional cylinder to simulate the intelligent reflection surface IRS, the high-altitude platform and the scatterers around the user side. The intelligent reflection surface IRS of the invention adopts a uniform plane reflection array unit, the number of the reflection units of each row is assumed to be M, the number of the reflection units of each column is assumed to be N, and the intelligent reflection surface IRS is assumed to be configured on the surface of a building, so that all users of the cell can be served. The height of the high-altitude platform is obviously higher than that of a ground building, no building shielding exists between the high-altitude platform and the intelligent reflection surface IRS, and a direct link is assumed between the high-altitude platform and the intelligent reflection surface IRS.
The obtained complex channel gain h based on the geometric model of the intelligent reflecting surface pq,uw The calculation formula of (t) is:
wherein t represents a time variable, L represents the number of times of a total tap, L represents the first tap, c l Indicating the gain effect brought about by the first tap,complex channel gain representing scattered components of high altitude platform (q, p) -th antenna element and user (w, u) -th antenna element at the first tap, < >>Representing complex channel gain of the intelligent reflection surface IRS reflection between the aerial platform (q, p) -th and the user (w, u) -th antenna unit at the first tap-> wherein ,Representing complex channel gain of direct component of aerial platform antenna unit (q, p) -th and user (w, u) -th antenna unit after being reflected by intelligent reflection surface IRS when first tap, and>representing the complex channel gain of the scattered component of the (q, p) -th antenna element after reflection by the IRS and the scatterer at the first tap.
wherein ,
wherein ,Nl,1 Representing scatterersNumber n of (2) l,1 Represents the nth l,1 Scattering bodies G t Indicating the gain of the transmitting antenna Tx, G r Indicating the gain of the antenna Rx of the user terminal, gamma TR Represents the path loss between Tx and Rx, λ represents the carrier wavelength, pi represents the circumference ratio, ζ pq,nl1 (t) represents (q, p) -th transmitting antenna element and scatterer +. >The time-varying propagation distance between them,representing (w, u) -th receive antenna element and scatterer +.>Time-varying propagation distance between f T Represents the maximum Doppler shift of Tx, cos (. Cndot.) represents the cosine function,/->Representing the high altitude platform Tx and scatterer->Time-varying azimuth angle, gamma T Indicating the moving azimuth angle of Tx, f R Represents the maximum Doppler shift of Rx, +.>Representing scatterer->Time-varying azimuth angle gamma with user Rx R Representing the moving azimuth of Rx, +.>Representing scatterer->Time-varying elevation angle between the user terminal and the user terminal; k represents the Lees factor, N represents the number of row reflecting elements of the IRS, M represents the number of column reflecting elements of the IRS, G represents the IRS antenna gain, gamma TIR Represents path loss, ζ, between Tx, IRS and Rx pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance, α, between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element IRS,T (t) represents the time-varying azimuth angle, beta, between the high altitude platform Tx and the smart reflective surface IRS IRS,R (t) represents the time-varying elevation angle, θ, between the intelligent reflective surface IRS and the user terminal Rx mn (t) represents a time-varying reflection phase; n (N) l,2 Representing scatterer->Number n of (2) l,2 Represents the nth l,2 Individual scatterers (a- >Representing (n, m) -th reflection unit and scatterer +.>Time-varying propagation distance between->Representing a scattered body->Time-varying propagation distance between reaching (w, u) -th receiving antenna elements, +.>Indicate meridian->Scattered time-varying elevation angle to the user side, +.>Representing the user side Rx and scatterer->Time-varying azimuth angles therebetween.
S2, in order to improve the communication quality to the greatest extent so as to achieve the optimal received signal power, and based on the principle, the optimization problem of the reflection phase of the reflection unit in the intelligent reflection surface is designed based on the broadband high-altitude platform channel model based on the intelligent reflection surface;
the optimization problem is expressed as follows:
wherein t represents a time variable, θ mn (t) represents the smart reflective surface IRS time-varying reflection phase,represents statistical mean operation, h pq,uw (t) represents the complex channel gain of the intelligent reflector-based wideband high altitude platform channel model.
S3, because the reflection component of the intelligent reflection unit in the intelligent reflection surface IRS in the channel model provided by the invention accounts for the main part of the complex channel gain of the model, the evaluation of the optimal time-varying reflection phase of the intelligent reflection surface IRS can be simplified into the reflection phase when the reflection component of the intelligent reflection unit in the intelligent reflection surface IRS is maximum; specific:
S31, according to the complex channel gain in step S1, the optimization problem in step S2 is expressed as follows:
wherein ,θmn (t) represents the smart reflective surface IRS time-varying reflection phase,representing statistical mean operations, L representing the number of times a total of taps, L representing the first tap, c l Indicating the gain effect brought about by the first tap, t indicating the time variable, (-)>Complex channel gain representing scattered components of high altitude platform (q, p) -th antenna element and user (w, u) -th antenna element at the first tap, < >>And the complex channel gain reflected by the intelligent reflection surface IRS between the aerial platform (q, p) -th and the user side (w, u) -th antenna unit at the first tap is represented.
S32, the signal complex channel gain of the model of the invention is mainly governed by a single-hop component (SB) of the intelligent reflection unit, the influence of the double-hop component (DB) is ignored, and the optimization problem can be simplified as follows:
wherein ,complex channel gain representing scattered components of high-altitude platform (q, p) -th antenna element and user (w, u) -th antenna element, < >>The complex channel gains of direct components after the antenna units (q, p) -th of the high-altitude platform and the antenna units (w, u) -th of the user side are reflected by the intelligent reflection surface IRS are shown.
The above problem can be expressed in turn as:
wherein ,Nl1 Representing scatterersNumber n of (2) l,1 Represents the nth l,1 Individual scatterers (a-> andRepresenting the auxiliary variables, cos (·) representing the cosine function,>representing the scattered body between the first tap high-altitude platform antenna element and the user antenna element +.>Later time-varying phase,/->Representing time-varying phase of direct component between 1 st tap high altitude platform antenna unit and user antenna unit after being reflected by (m, n) -th intelligent reflecting unit, < + >>Representing the time-varying phase of the direct component between the 1 st tap high altitude platform antenna unit and the user antenna unit after being reflected by the (m ', n') -th intelligent reflection unit.
wherein ,
wherein ,cl Representing the gain effect from the first tap, c 1 Represents the gain effect brought by the 1 st tap, K represents the rice factor, λ represents the carrier wavelength, pi represents the circumference ratio,representing (q, p) -th transmitting antenna elements and scatterersTime-varying propagation distance between->Representing (w, u) -th receive antenna element and scatterer +.>Time-varying propagation distance between f T Represents the maximum Doppler shift of Tx, cos (. Cndot.) represents the cosine function,/->Representing the high altitude platform Tx and scatterer->Time-varying azimuth angle between gamma T Indicating the moving azimuth angle of Tx, f R Indicating the maximum doppler shift of Rx, Representing scatterer->Time-varying azimuth angle gamma between the antenna and the user terminal Rx R Representing the moving azimuth of Rx, +.>Representing scatterer->Time-varying elevation angle, ζ, between the user terminal Rx pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance, α, between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element IRS,T (t) represents the time-varying azimuth angle, beta, between the aerial platform Tx and the smart reflective surface IRS IRS,R (t) represents the time-varying elevation angle, θ, between the intelligent reflective surface IRS and the user terminal Rx mn And (t) represents a time-varying reflection phase.
According to equation (5)It can be seen that->And (3) withWhen constant and equal, +.>Taking the maximum value;
wherein The specific expression is: />
wherein ,the method is characterized in that the method is used for representing the time-varying phase after passing through an (m, n) -th intelligent reflection unit between a 1 st tap high-altitude platform antenna unit and a user antenna unit, pi represents the circumference ratio, lambda represents the carrier wavelength, and xi represents the carrier wavelength pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element, f IRST (t) represents the time-varying Doppler shift of the arrival of the transmitting end Rx at the intelligent reflection surface IRS, f IRST (t)＝f T cos(α IRS,T (t)-γ T), wherein ,fT Represents the maximum Doppler shift of Tx, cos (. Cndot.) represents the cosine function,/->Representing the high altitude platform and scatterer->Time-varying azimuth angle between gamma T Indicating the moving azimuth angle of Tx, f IRSR (t) time-varying Doppler shift of the intelligent reflection surface IRS reaching the user terminal Rx, f IRSR (t)＝f R cos(π-γ R )cosβ IRS,R (t) wherein f R Represents the maximum Doppler shift of Rx, gamma R Representing the azimuth angle of movement of Rx, beta IRS,R (t) represents the time-varying elevation angle between the intelligent reflection surface IRS and the user terminal Rx.
S4, according to the harmonic addition theorem, obtaining the optimal IRS time-varying reflection phase of the intelligent reflection surface; the method comprises the following steps:
assuming that the auxiliary variable is andAnd assume that the optimal intelligent reflection surface IRS time-varying reflection phase isWherein make->Wherein t represents a time variable, lambda represents a carrier wavelength, and zeta pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element, f IRST (t) represents the time-varying Doppler shift of the arrival of the transmitting end Rx at the intelligent reflection surface IRS, f IRSR (t) represents the time-varying Doppler shift of the intelligent reflection surface IRS to the user terminal Rx.
At this time, the liquid crystal display device,the solution problem for the optimal reflection phase is expressed as:
wherein ,representing statistical mean operations, L representing the number of times a total of taps, L representing the first tap, N l,1 Representing scatterer->Number n of (2) l,1 Represents the nth l,1 Individual scatterers (a->Representing auxiliary variables +.>Representing the scattered body between the first tap high-altitude platform antenna element and the user antenna element +.>Later time-varying phase,/->Representing azimuthal probability density function, +.>Representing elevation probability density function, ++>Representing the user side Rx and scattererAzimuth angle between->Representing the user side Rx and scatterer->Elevation angle between.
According to the harmonic addition theorem, in order to reach the maximum value of the equation, it is necessary to ensure that:
wherein sgn (·) represents a sign function, cos (·) represents a cosine function, tan -1 (. Cndot.) represents the inverse of the tangent function, χ A 、χ B Andrepresenting auxiliary variables +.> wherein ,Representing a scattered body between the first tap high-altitude platform antenna element and the user antenna element>The time-varying phase of the latter.
At this timeExpressed as:
wherein ,
the optimal smart reflector IRS time-varying reflection phase is expressed as follows:
wherein ,indicating the optimal smart reflector IRS time-varying reflection phase.
S5, according to the motion conditions of the high-altitude platform and the user side, determining time-varying parameters among the high-altitude platform Tx, the user side Rx, the intelligent reflection surface IRS and the scatterer respectively.
The time-varying parameters include the altitude platform Tx and scatterersUser terminal Rx and scatterer->Intelligent reflection surface IRS and scattererAnd user side Rx and diffuser->Time-varying azimuth and time-varying elevation parameters in between. The method comprises the following steps:
wherein Representing a high-altitude platform and scatterers->Time-varying azimuth angle between +.>Representing a high-altitude platform and scatterers->Time-varying elevation angle between->Representing user side and diffuser->A time-varying azimuth angle between the two,representing user side and diffuser->Time-varying elevation angle between, t represents time variable, delta 1 and δ2 Represents an auxiliary variable, pi represents a circumference ratio, < +.>Representing scatterer->The ordinate in the coordinate system, arctan (·) represents the inverse of the tangent function, H T Indicating the height of Tx, H R Represents the height of Rx, R represents the scatterer +.>Distance between projection of user side, tan (-) represents tangent function,/-, and>representing scatterer->Elevation angle relative to the user side->Representing the scattering body around the high-altitude platform and the user side->Is expressed by the time-varying distance between projections of (a), arccos (·) represents the inverse of the cosine function, ζ T,R (t) represents the time-varying horizontal distance between the high-altitude platform and the user terminal, < >>Representing intelligent reflecting surface and scatterer>Distance between projections, < > >Representing the user side and the diffuser->Time-varying distance, ζ, between projections of (a) IRS,T (t) represents the time-varying horizontal distance, ζ, between the intelligent reflective surface IRS and the aerial platform IRS,R (t) represents an intelligent reflecting surfaceTime-varying horizontal distance between IRS and user side, < >>Representing the user side and the diffuser->Time-varying distance between projections, < >>Representing intelligent reflector IRS and diffuser->Time-varying azimuth angle between +.>Representing intelligent reflector IRS and diffuser->Time-varying elevation angle between->Representing the user side Rx and scatterer->Time-varying azimuth angle between +.>Representing the user side Rx and scatterer->Time-varying elevation angle, delta 4 、δ 5 Representing auxiliary variables +.>Representing scatterer->Ordinate in the coordinate system, H IRS Indicating the height of the intelligent reflector IRS, < >>Representing scatterer->Distance between projection to the user side Rx, < >>Representing scatterer->Elevation angle relative to the user side Rx->Representing high altitude platform Tx and scatterersTime-varying distance between projections, < >>Representing scatterer->With respect to the time-varying elevation angle of the user terminal Rx,representing the user side Rx and scatterer->Time-varying distance, ζ, between projections of (a) IRS,R (t) represents the time-varying horizontal distance between the intelligent reflective surface IRS and the user terminal Rx, < ->Indicating intelligent reflector IRS and diffuser- >Distance between projections, < >>Representing the user side Rx and scatterer->Time-varying distances between projections of (a).
S6, solving a space-time correlation function based on a broadband high-altitude platform channel model of the intelligent reflection surface through the optimal IRS time-varying reflection phase of the intelligent reflection surface obtained in the step S4 and the time-varying function obtained in the step S5, and determining the influence of the IRS of the intelligent reflection surface on the high-altitude platform channel characteristic through correlation analysis; specific:
s61, solving a space-time correlation function of a broadband high-altitude platform channel model based on the intelligent reflection surface IRS through the optimal intelligent reflection surface IRS time-varying reflection phase obtained in the step S4 and the time-varying function obtained in the step S5, wherein the calculation formula is as follows:
wherein ,ρ1,pq,uw,p′q′,u′w′ (t,d P ,d Q ,d U ,d W ) Represents h at tap 1 pq,uw(t) and hp'q',u'w' (t) a spatio-temporal correlation function between,a spatio-temporal correlation function representing the scattering component between Rx and Tx at tap 1,A spatio-temporal correlation function representing the direct component reflected by IRS between Rx and Tx at tap 1,A space-time correlation function representing the scattered component between Rx and Tx at tap 1 via IRS and scatterer reflection;
ρ l,pq,uw,p′q′,u′w′ (t,d P ,d Q ,d U ,d W ) Represents h at the first tap pq,uw(t) and hp'q',u'w' (t) a spatio-temporal correlation function between, Representing the spatio-temporal correlation function of the scattering component between Rx and Tx at the first tap, +.>A space-time correlation function representing the scattered component between Rx and Tx at the first tap via IRS and scatterer reflection; h is a pq,uw (t) represents the complex channel gain between the (q, p) -th antenna element and the (w, u) -th antenna element, h p'q',u'w' (t) represents the complex channel gain, d, between the (q ', p') -th antenna element and the (w ', u') -th antenna element P and dQ Representing the difference in the abscissas of two antenna elements (q, p) and (q ', p') in the high-altitude platform, d U and dW Representing the difference in the abscissas of the two antenna elements (w, u) and (w ', u') of the user side, respectively.
wherein ,
where pi represents the circumference ratio, lambda represents the carrier wavelength, M represents the number of column reflection units of the intelligent reflection surface IRS, N represents the number of row reflection units of the intelligent reflection surface IRS,representing auxiliary variables, A IRS-SB 、B IRS-SB Representing the auxiliary variable, cos (·) representing the cosine function, α IRS,T Representing azimuth angle between intelligent reflector IRS and high altitude platform Tx, beta IRS,T Representing elevation angle between intelligent reflection surface IRS and high altitude platform Tx, sin (·) representing sine function, beta IRS,R Representing elevation angle, θ, between intelligent reflective surface IRS and user Rx R Indicating the Rx direction of the user terminal, A SB 、B SB 、C SB 、D SB and ESB Represents an auxiliary variable, K represents the Leis factor, < ->Representing the user side Rx and scatterer->Azimuth probability density function,/->Representing the user side Rx and scatterer->Elevation probability density function, R represents the receiving end Rx to scatterer +.>Distance, ζ T,R Represents the horizontal distance between the high-altitude platform Tx and the user terminal Rx, f T Indicating the maximum Doppler shift, gamma, of the high altitude platform Tx R Representing the moving azimuth angle of the user terminal Rx, f R Indicating the maximum Doppler shift of the user side Rx, < >>Representing the user side Rx and scatterer->Azimuth angle of->Representing the user side Rx and scatterer->Elevation angle of A DB 、B DB 、C DB 、D DB and EDB Representing auxiliary variables +.>Representing the user side Rx and scatterer->Azimuth probability density function,/->Representing the user side Rx and scatterer->Elevation probability density function->Representing the user side Rx and scatterer->Azimuth angle between->Representing the user side Rx and scatterer->Elevation angle delta between M Represents the line spacing between adjacent reflective elements, +.>Representing the user side Rx and scatterer->Distance of propagation, ζ IRS,R Representing the propagation distance between the smart reflective IRS and the user Rx>Representing the user side Rx and scatterer->Azimuth angle, θ between IRS Indicating IRS direction, delta N Representing the column spacing between adjacent reflective elements.
S62, determining the influence of the intelligent reflection surface IRS, the number of the intelligent reflection units and the size of the intelligent reflection units on the channel statistical characteristics of the high-altitude platform by using the space-time correlation function obtained in the step S61;
increasing the intelligent reflection surface IRS, the number of intelligent reflection units and the size of the intelligent reflection units can effectively reduce multipath fading. The degree of reduction in the spatial-temporal correlation decreases as the number of intelligent reflective surfaces IRS, intelligent reflective units increases, and the size of the intelligent reflective units increases.
The invention also provides an apparatus comprising a memory and a processor, wherein:
a memory for storing a computer program capable of running on the processor;
and the processor is used for executing the steps of the intelligent reflection surface-based broadband high-altitude platform channel model building method when the computer program is run.
The invention also provides a storage medium, wherein the storage medium is stored with a computer program, and the computer program realizes the steps of the intelligent reflection surface-based broadband high-altitude platform channel model building method when being executed by at least one processor.
Fig. 2 is a graph comparing absolute envelope amplitudes of a conventional high-altitude platform channel model and a high-altitude channel model based on an intelligent reflection surface under different intelligent reflection IRS reflection phases. In fig. 2, the time-varying phase of the smart reflective IRS reflective unit of method one is: θ mn (t) =0; the time-varying phase of the intelligent reflection IRS reflection unit and the scattering component lose phase; the time-varying phase of the IRS reflection unit of method three is in phase with the scattering component. It can be seen from fig. 2 that the absolute envelope amplitude of the received signal can be obviously improved by adopting the intelligent reflection surface IRS, and meanwhile, the absolute envelope amplitude of the received signal can be enhanced by adjusting the time-varying phase of the intelligent reflection surface, so that it is verified that the model of the invention can effectively change the propagation environment between the high-altitude platform and the receiving end.
Fig. 3 is a graph of absolute envelope magnitude comparisons for different numbers of reflective units of the intelligent reflective surface IRS. It can be seen from fig. 3 that increasing the number of intelligent reflection units significantly enhances the absolute envelope amplitude of the received signal.
FIG. 4 is a graph comparing the received spatial correlation functions for different numbers of reflective units of the intelligent reflective surface IRS; fig. 5 is a graph comparing the received spatial correlation functions for different numbers of reflection units of the intelligent reflection surface IRS. It can be seen that the degree of space-time correlation reduction decreases with increasing number of intelligent reflective IRS reflective units. Thus, the smart reflective IRS assistance model may describe the spatiotemporal non-stationarity of the smart reflective IRS system.
Claims (10)
1. The method for establishing the broadband high-altitude platform channel model based on the intelligent reflecting surface is characterized by comprising the following steps of:
s1, taking the surrounding of a user terminal Rx and the propagation environments around an intelligent reflection surface IRS and an overhead platform Tx into consideration, adopting a three-dimensional multi-cylinder to represent a scatterer around the user terminal, adopting a three-dimensional multi-ellipse-cylinder to represent the scatterer between the overhead platform Tx and the intelligent reflection surface IRS, establishing a broadband overhead platform channel model based on the intelligent reflection surface, and obtaining the complex channel gain of the channel model;
s2, in order to improve the communication quality to the greatest extent so as to achieve the optimal received signal power, and based on the principle, according to a broadband high-altitude platform channel model based on the intelligent reflecting surface, adopting statistical mean value operation to design an optimization problem based on the reflecting phase of a reflecting unit in the intelligent reflecting surface;
s3, because the reflection component of the intelligent reflection unit in the intelligent reflection surface IRS in the channel model accounts for the main part of the complex channel gain of the model, the evaluation of the optimal time-varying reflection phase of the intelligent reflection surface IRS is simplified into a reflection phase when the reflection component of the intelligent reflection unit in the intelligent reflection surface IRS is maximum;
s4, according to the harmonic addition theorem, obtaining the optimal IRS time-varying reflection phase of the intelligent reflection surface;
S5, determining time-varying parameters among the high-altitude platform Tx, the user terminal Rx, the intelligent reflection surface IRS and the scatterer according to the motion conditions of the high-altitude platform and the user terminal, wherein the time-varying parameters comprise the high-altitude platform Tx and the scattererUser terminal Rx and scatterer->Intelligent reflector IRS and diffuser->And user side Rx and diffuser->Time-varying azimuth and time-varying elevation parameters in between;
s6, solving a space-time correlation function based on a broadband high-altitude platform channel model of the intelligent reflection surface through the optimal IRS time-varying reflection phase of the intelligent reflection surface obtained in the step S4 and the time-varying parameters obtained in the step S5, and determining the influence of the IRS of the intelligent reflection surface on the high-altitude platform channel characteristic through correlation analysis.
2. The method for establishing a wideband high-altitude platform channel model based on an intelligent reflecting surface as claimed in claim 1, wherein the complex channel gain h of the wideband high-altitude platform channel model based on the intelligent reflecting surface obtained in step S1 is pq,uw The calculation formula of (t) is:
wherein t represents a time variable, L represents the number of times of a total tap, L represents the first tap, c l Indicating the gain effect brought about by the first tap,complex channel gain representing scattered components of high altitude platform (q, p) -th antenna element and user (w, u) -th antenna element at the first tap, < > >Representing complex channel gain reflected by an intelligent reflection surface IRS between an aerial platform (q, p) -th and a user side (w, u) -th antenna unit at the first tap; Representing complex channel gain of direct component of aerial platform antenna unit (q, p) -th and user (w, u) -th antenna unit after being reflected by intelligent reflection surface IRS when first tap, and>representing the complex channel gain of the scattered component of the (q, p) -th antenna element after reflection by the IRS and the scatterer at the first tap.
3. The method for establishing a wideband high-altitude platform channel model based on intelligent reflecting surfaces as claimed in claim 1, wherein the optimization problem in step S2 is expressed as follows:
wherein t represents a time variable, θ mn (t) represents the smart reflective surface IRS time-varying reflection phase,represents statistical mean operation, h pq,uw (t) represents the complex channel gain of the intelligent reflector-based wideband high altitude platform channel model.
4. The method for building a wideband high altitude platform channel model based on intelligent reflecting surface according to claim 3, wherein in step S3, the complex channel gain in step S1 is brought into the optimization problem in step S2, and the optimization problem is further expressed as:
wherein L represents the number of times of a total tap, L represents the first tap, c l Indicating the gain effect brought about by the first tap,complex channel gain representing scattered components of high altitude platform (q, p) -th antenna element and user (w, u) -th antenna element at the first tap, < >>And the complex channel gain reflected by the intelligent reflection surface IRS between the aerial platform (q, p) -th and the user side (w, u) -th antenna unit at the first tap is represented.
5. The method for building the broadband high-altitude platform channel model based on the intelligent reflecting surface according to claim 4, wherein the signal complex channel gain is mainly governed by a single-hop component SB of the intelligent reflecting unit, the influence of a double-hop component DB is ignored, and the optimization problem is simplified as follows:
wherein ,representing complex channel gains of direct components of the aerial platform antenna units (q, p) -th and the user antenna units (w, u) -th after being reflected by the intelligent reflection surface IRS in the first tap;
based on the complex exponential nature, the above problem is again expressed as:
wherein ,Nl1 Representing scatterersNumber n of (2) l,1 Represents the nth l,1 Individual scatterers (a-> andRepresenting the auxiliary variables, cos (·) representing the cosine function,>representing the scattered body between the first tap high-altitude platform antenna element and the user antenna element +.>Later time-varying phase,/->Representing the time-varying phase of the direct component between the 1 st tap high altitude platform antenna unit and the user antenna unit after passing through the (m, n) -th intelligent reflection unit, +. >Representing the time-varying phase of the direct component between the 1 st tap high altitude platform antenna unit and the user antenna unit after being reflected by the (m ', n') -th intelligent reflection unit;
according to formula (5)It can be seen that->And->When constant and equal, +.>Taking the maximum value;
wherein The specific expression is:
wherein ,representation ofTime-varying phase of direct component between 1 st tap high altitude platform antenna unit and user antenna unit after passing through (m, n) -th intelligent reflecting unit, pi represents circumference ratio, lambda represents carrier wave wavelength, xi pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element, f IRSR (t) time-varying Doppler shift of the intelligent reflection surface IRS reaching the user terminal Rx, f IRST (t) represents the time-varying Doppler shift of the arrival of the transmitting end Rx at the intelligent reflection surface IRS.
6. The method for establishing the broadband high-altitude platform channel model based on the intelligent reflecting surface according to claim 1, wherein the step S4 is specifically:
assuming that the auxiliary variable is andAnd assume that the optimal intelligent reflection surface IRS time-varying reflection phase isWherein make->Wherein pi represents the circumference ratio, t represents the time variable, lambda represents the carrier wavelength, and ζ pq,mn (t) represents the time-varying propagation distance, ζ, between the (q, p) -th transmitting antenna element and the (n, m) -th reflecting element mn,uw (t) represents the time-varying propagation distance between the (n, m) -th reflecting element and the (w, u) -th receiving antenna element, f IRST (t) time-varying Doppler shift, f, of the high altitude platform Tx reaching the intelligent reflective surface IRS IRSR (t) represents the time-varying doppler shift of the intelligent reflection surface IRS to the user Rx;
at this time, the liquid crystal display device,the solution problem for the optimal reflection phase is expressed as:
wherein ,representing statistical mean operations, L representing the number of times a total of taps, L representing the first tap, N l,1 Representing scatterer->Number n of (2) l,1 Represents the nth l,1 Individual scatterers (a-> andRepresenting auxiliary variables +.>Representing the scattered body between the first tap high-altitude platform antenna element and the user antenna element +.>Later time-varying phase,/->Representing azimuthal probability density function, +.>Representing elevation probability density function, ++>Representing from->Arrive at the user end azimuth after scattering, +.>Representing from->The scattered elevation angle reaches the user side;
according to the harmonic addition theorem, in order to reach the maximum value of the equation, it is necessary to ensure that:
wherein sgn (·) represents the sign function, χ A and χB Represents an auxiliary variable, cos (·) represents a cosine function, tan -1 (. Cndot.) represents the inverse of the tangent function;
at this timeExpressed as:
the optimal smart reflector IRS time-varying reflection phase is expressed as follows:
wherein ,representation ofThe optimal intelligent reflection surface IRS time-varying reflection phase.
7. The method for establishing the broadband high-altitude platform channel model based on the intelligent reflecting surface according to claim 1, wherein the step S5 is specifically:
high altitude platform and scattererThe time-varying azimuth angle between:
wherein ,representing a high-altitude platform and scatterers->Time-varying azimuth angle between, t represents time variable, delta 1 Represents an auxiliary variable, pi represents a circumference ratio, < +.>Representing scatterer->An ordinate in the coordinate system;
high altitude platform and scattererThe time-varying elevation angle between:
wherein ,representing a high-altitude platform and scatterers->Time-varying elevation angle therebetween, arctan (·) represents the inverse of the tangent function, H T Represents the height of the high-altitude platform, H R Indicating the height of the user side, R indicates the diffuser +.>Distance between projection and user side, +.>Representing scatterer->Elevation angle relative to the user side->Representing the scattering body around the high-altitude platform and the user side->Time-varying distances between projections of (a);
user terminal and scattererThe time-varying azimuth angle between:
wherein ,representing user side and diffuser->Time-varying azimuth angle, delta 2 Representing the auxiliary variable;
high altitude platform and scattererThe time-varying elevation angle between:
wherein ,representing user side and diffuser->Time-varying elevation angle between->Representing the scattering body around the high-altitude platform and the user side->Time-varying distances between projections of (a);
intelligent reflector IRS and scattererThe time-varying azimuth angle between:
wherein ,representing smart reflectionsPlane IRS and diffuser->Time-varying azimuth angle, delta 4 Represents the auxiliary variable(s),representing scatterer->An ordinate in the coordinate system;
intelligent reflector IRS and scattererThe time-varying elevation angle between:
wherein ,representing intelligent reflector IRS and diffuser->Time-varying elevation angle between H IRS Indicating the height of the intelligent reflector IRS, < >>Representing scatterer->The distance from the projection of the user side Rx, tan (-) represents the tangent function,representing the user side Rx and scatterer->Elevation angle between->Representing the high altitude platform Tx and scatterer->Time-varying distances between projections of (a);
user terminal Rx and scattererThe time-varying azimuth angle between:
wherein ,representing the user side Rx and scatterer->Time-varying azimuth angle, delta 5 Representing the auxiliary variable;
User terminal Rx and scattererThe time-varying elevation angle between:
wherein ,representing the user side Rx and scatterer->Time-varying elevation angle between->Representing the user side Rx and scatterer->Time-varying distances between projections of (a).
8. The method for establishing the broadband high-altitude platform channel model based on the intelligent reflecting surface according to claim 1, wherein the step S6 is specifically:
s61, solving a space-time correlation function of a broadband high-altitude platform channel model based on the intelligent reflection surface IRS through the optimal intelligent reflection surface IRS time-varying reflection phase obtained in the step S4 and the time-varying function obtained in the step S5, wherein the calculation formula is as follows:
wherein ,ρ1,pq,uw,p′q′,u′w′ (t,d P ,d Q ,d U ,d W ) Represents h at tap 1 pq,uw(t) and hp'q',u'w' (t) a spatio-temporal correlation function between,a spatio-temporal correlation function representing the scattering component between Rx and Tx at tap 1,A spatio-temporal correlation function representing the direct component reflected by IRS between Rx and Tx at tap 1,Representing the spatio-temporal correlation function of the scattered components between Rx and Tx at tap 1, through IRS and scatterer reflection, ρ l,pq,uw,p′q′,u′w′ (t,d P ,d Q ,d U ,d W ) Represents h at the first tap pq,uw(t) and hp'q',u'w' (t) a spatiotemporal correlation function between +.>Representing the spatio-temporal correlation function of the scattering component between Rx and Tx at the first tap, +. >A space-time correlation function representing the scattered component between Rx and Tx at the first tap via IRS and scatterer reflection; h is a pq,uw (t) represents the complex channel gain between the (q, p) -th antenna element and the (w, u) -th antenna element, h p'q',u'w' (t) represents the complex channel gain, d, between the (q ', p') -th antenna element and the (w ', u') -th antenna element P and dQ Representing the difference in the abscissas of two antenna elements (q, p) and (q ', p') in the high-altitude platform, d U and dW Representing the difference between the abscissas of the two antenna elements (w, u) and (w ', u') at the user end, respectively;
s62, determining the influence of the intelligent reflection surface IRS, the number of the intelligent reflection units and the size of the intelligent reflection units on the channel statistical characteristics of the high-altitude platform by using the space-time correlation function obtained in the step S61.
9. An apparatus comprising a memory and a processor, wherein:
a memory for storing a computer program capable of running on the processor;
a processor for performing the steps of the intelligent reflector based broadband aerial platform channel model building method according to any one of claims 1-8 when running said computer program.
10. A storage medium having stored thereon a computer program which, when executed by at least one processor, implements the steps of the intelligent reflection-based broadband aerial platform channel model building method according to any of claims 1-8.
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