CN115801094A - Low-orbit satellite channel modeling method and device of double-sphere-center-cube 3D geometric structure - Google Patents
Low-orbit satellite channel modeling method and device of double-sphere-center-cube 3D geometric structure Download PDFInfo
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Abstract
The invention provides a low-orbit satellite channel modeling method and a low-orbit satellite channel modeling device of a double-sphere-center angle body 3D geometric structure, wherein the method comprises the following steps of: acquiring communication parameters and geometric parameters for constructing a double-sphere-center angle body; constructing a free space loss model; acquiring first measurement data, determining a communication elevation angle range of a receiving end, dividing intervals, and fitting shadow fading of a low-orbit satellite in different intervals in the overhead process into a dynamic shadow fading Gaussian mixture distribution model with time-varying parameters based on the first measurement data; acquiring second measurement data, fitting a multipath arrival angle of the low-orbit satellite in the overhead process into a parameter time-varying Laplacian distribution model, and determining a small-scale fading channel impulse response model based on the Laplacian distribution model; and determining a channel impulse response model of the low-orbit satellite based on the free space loss model, the dynamic shadow fading mixed Gaussian distribution model and the small-scale fading channel impulse response model. The method improves the accuracy of the low-orbit satellite communication channel characteristic description.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a low-orbit satellite channel modeling method and device of a double-sphere-center angle body 3D geometrical structure.
Background
Currently, 5G mobile communication systems are in large-scale commercial use, and research and exploration on 6G mobile communication technology are started in countries around the world; the conventional ground network cannot solve the problem of high-speed data communication in areas which are not covered by maritime, aviation and other ground networks. Satellite communication has the characteristics of wide coverage and large communication capacity, is an effective means for solving the problems, becomes an important component of a 6G communication system, and provides global seamless access capability; the international standardization organization 3GPP focuses on the effect and influence of satellite communication on a 6G mobile network in the relevant standards of a non-ground communication network; the 6G mobile communication technology integrated with satellite communication provides prospective basis for the new information service fields of virtual reality, smart cities, unattended operation and the like.
The satellite-ground link of the low-orbit satellite has dynamic time-varying characteristics such as high Doppler frequency shift, large communication time delay, nonlinear memory effect and the like, and the channel characteristics of the low-orbit satellite are urgently required to be analyzed and modeled; the low earth orbit satellite has a high communication frequency band, and the near earth orbit brings high-speed relative motion with the ground receiving terminal, resulting in a large-range doppler frequency shift and a high-speed doppler change rate (tens of times higher than that of the ground network). The transmission time delay of different time nodes in the process of the low-orbit satellite passing the top is different, and the transmission time delay is large (tens of milliseconds magnitude); at a ground receiving end, the influence of multipath effects caused by ground scatterers in different spaces on Doppler expansion and time delay expansion channel characteristics is obvious; at the satellite load end, because the satellite transmission power is limited and the heat dissipation efficiency is low, the satellite is in a saturation point working state for a long time, and signals are seriously distorted due to nonlinear memory effect brought by radio frequency devices such as an input/output filter, a high-power amplifier and the like. In order to accurately characterize the satellite-to-ground link channel of the low-orbit satellite and improve the signal transmission quality and transmission rate as much as possible on limited spectrum resources, modeling and analysis must be performed on the large-scale fading and small-scale fading characteristics of the low-orbit satellite.
At present, according to a modeling mode of a channel model, the channel model is mainly divided into a deterministic model, a stochastic model and a quasi-stochastic model. The deterministic model is applied to a specific scene, a detailed scene distribution condition needs to be obtained before modeling, and channel transmission characteristics are obtained through simulation deduction. The randomness model has better universality, and the probability density function of the channel is determined through theoretical calculation and channel measurement statistical parameters. The quasi-randomness model is based on a data result of channel measurement and a calculation method of a certainty model, and channel characteristics are divided into a certainty part and a statistic part for description.
In the invention patent with publication number CN 113644942A entitled "a geometric-based 3D MIMO LEO satellite air-space-ground channel modeling method", a modeling method for calculating time-varying channel parameters such as signal arrival angle, departure angle, time-varying propagation distance, and the like based on the geometric relationship between a mobile LEO (low earth orbit) satellite transmitting terminal, a mobile unmanned aerial vehicle terminal, and a mobile ground receiving terminal is disclosed. The method considers the scattering phenomenon of wireless signals generated at an unmanned aerial vehicle terminal and a receiver terminal as being intensively distributed on a spherical surface taking a receiving end as a center, and generates channel impulse response from a 3D MIMO LEO satellite transmitting end antenna to a relay end antenna and then to the receiving end antenna based on the scattering phenomenon; the method only describes the change of the relative position relation between the transmitting end and the receiving end, and does not realize the accurate description and modeling of the multipath arrival angle distribution time-varying characteristics in the satellite overhead process, so that the method cannot ensure the accuracy of the channel characteristic description of the low-orbit satellite.
As can be seen from the above, the conventional channel modeling method for the low-orbit satellite has a technical problem of low accuracy of describing the channel characteristics, and therefore how to improve the accuracy of describing the communication channel characteristics of the low-orbit satellite is a technical problem to be solved urgently.
Disclosure of Invention
In view of the above, the present invention provides a method and an apparatus for modeling a low-orbit satellite channel with a 3D geometry of a dual-centroid pyramid, so as to solve one or more problems in the prior art.
According to one aspect of the invention, the invention discloses a method for modeling a low-orbit satellite channel of a double-sphere-center angle 3D geometrical structure, which comprises the following steps:
acquiring communication parameters and geometric parameters for constructing a double-sphere-center angle body, wherein the geometric parameters comprise orbit height, earth radius, satellite position information and receiving end position information, and the communication parameters comprise communication frequency, transmission wavelength and electromagnetic wave propagation speed;
constructing a free space loss model based on the geometric parameters and the communication parameters;
acquiring first measurement data of a low-orbit satellite in the process of passing the top, wherein the first measurement data comprise satellite signals, determining a receiving end communication elevation angle range, carrying out interval division on the receiving end communication elevation angle range, and fitting shadow fading of the low-orbit satellite in different intervals in the process of passing the top into a dynamic shadow fading Gaussian mixed distribution model with time-varying parameters based on the first measurement data;
acquiring second measurement data of a low-orbit satellite in a process of passing through the top, wherein the second measurement data comprises a multipath arrival angle of the low-orbit satellite, fitting the multipath arrival angle of the low-orbit satellite in the process of passing through the top into a parameter time-varying Laplace distribution model based on the second measurement data, and determining a small-scale fading channel impulse response model based on the fitted Laplace distribution model;
and determining a channel impulse response model of the low-orbit satellite based on the free space loss model, the dynamic shadow fading mixed Gaussian distribution model and the small-scale fading channel impulse response model.
In some embodiments of the invention, the free space loss is expressed as:
wherein, f c Denotes a communication frequency, λ denotes a transmission wavelength, c denotes an electromagnetic wave propagation speed, d (t) denotes a time-varying transmission distance between a satellite transmitting end and a receiving end,
R E represents the radius of the earth, H represents the orbital altitude,
representing the time-varying LOS path angle of arrival, θ los (t) represents the time-varying LOS path arrival azimuth.
In some embodiments of the present invention, the dividing the receiving end communication elevation angle range into intervals includes:
determining a level value corresponding to each satellite signal;
determining an angle interval based on a numerical variation of the level values;
and dividing the receiving end communication elevation angle range into equal interval intervals based on the angle intervals.
In some embodiments of the present invention, the expression of the dynamic shadow fading gaussian mixture distribution model is:
where Δ θ represents the angular interval, s f Representing a shadow fade,. Epsilon.m represents the weight of the Gaussian distribution corresponding to the mth interval, and ∑ ε m ＝1，ε m > 0, M denotes the total number of partitioned intervals,
ξ represent the set of gaussian distribution weights and gaussian distribution parameters,
set of mean and variance parameters, p, representing each independent Gaussian distribution Process m The probability of the gaussian distribution corresponding to the mth interval is shown.
In some embodiments of the present invention, the expression of the parameter time-varying laplacian distribution model is:
wherein, the first and the second end of the pipe are connected with each other,
and
respectively showing the distribution range of the LOS path to the azimuth angle and the distribution range of the LOS path to the elevation angle,
χ represents the mean square error of the angular power spectrum, β and β' are normalization factors,
θ los (t) and
respectively, representing a time-varying LOS path arrival azimuth angle and a LOS path arrival elevation angle.
In some embodiments of the present invention, the expression of the small-scale fading channel impulse response model is:
wherein ssf los (t) denotes the small-scale fading channel impulse response of the direct path, ssf nlos (t) represents the small-scale fading channel impulse response of multipath, K (t) represents the time-varying Rice factor, f los Represents the direct path Doppler shift, phi los (t) represents the time-varying received phase of the direct path, S represents the total number of multipath rays,
indicating the s-th multipath doppler shift,
representing the time-varying reception phase of the s-th multipath.
In some embodiments of the invention, the expression of the channel impulse response model for a low orbit satellite is:
h(t)＝p l (t)×s f (t)×s s (t)；
wherein h (t) represents the channel impulse response of the low orbit satellite, p l (t) represents the free space loss, s f (t) represents shadow fading, s s (t) denotes small scale fading.
In some embodiments of the invention, the method further comprises: and constructing a 3D geometric model of the double-sphere-center angle body based on the geometric parameters, wherein the first sphere-center angle body takes the earth sphere as a vertex, and the second sphere-center angle body takes the receiving end as a vertex.
According to another aspect of the present invention, there is also disclosed a system for modeling low-orbit satellite channels in a 3D geometry with dual-centroid angles, the system comprising a processor and a memory, the memory having stored therein computer instructions, the processor being configured to execute the computer instructions stored in the memory, the system implementing the steps of the method according to any of the above embodiments when the computer instructions are executed by the processor.
According to another aspect of the present invention, a computer-readable storage medium is also disclosed, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any of the embodiments above.
According to the method and the device for modeling the low-orbit satellite channel with the double-sphere-center horn 3D geometrical structure, disclosed by the embodiment of the invention, the fitting of dynamic shadow fading is realized through mixed Gaussian distribution according to the measurement data of shadow fading in the satellite overhead process, and the mapping relation between a weight factor and a time-varying elevation angle is established, so that a dynamic shadow fading Gaussian mixed distribution model with time-varying parameters is obtained; according to the measurement data of the multipath arrival angle in the satellite over-top process, fitting the multipath arrival angle of the low-orbit satellite in the over-top process into a parameter time-varying Laplace distribution model; and then the low orbit satellite channel is described by adopting the channel impulse response model of the low orbit satellite constructed based on the model, so that the accuracy of communication channel characteristic description is improved.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. For purposes of illustrating and describing some portions of the present invention, corresponding parts may be exaggerated in the drawings, i.e., may be larger relative to other components in an exemplary device actually made according to the present invention. In the drawings:
fig. 1 is a schematic flow chart of a low-earth orbit satellite channel modeling method of a 3D geometry with a double-sphere-center cube according to an embodiment of the invention.
Fig. 2 is a schematic structural diagram of a low-earth-orbit satellite-earth link dual-sphere-center cube 3D geometric model according to an embodiment of the invention.
Fig. 3 is a schematic structural diagram illustrating a description of multipath distribution in a spherical cap-shaped effective scattering area according to an embodiment of the present invention.
Fig. 4 is a schematic logical structure diagram of the dual-sphere-center 3D geometry low-earth orbit satellite channel modeling system in the channel simulation process according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.
It should be emphasized that the term "comprises/comprising/comprises/having" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.
For the existing low-orbit satellite channel modeling method, the characteristic of low-orbit satellite channel characteristic description accuracy generally exists, for example, a shadow fading description method based on a first-order Markov multi-state channel model is disclosed in a patent application with the publication number of CN 112436882B and the name of LEO satellite channel modeling method and device based on a double Markov model, the method realizes the description of a small-scale fading multi-path dynamic birth and death process through measured data, and obtains a Leise channel model of an LEO satellite through determining channel parameters; however, in the method, the influence of the communication elevation angle change on the multipath signal in the process of low-orbit satellite overhead is not reflected in the process of computing the rice factor and describing the small-scale fading dynamic change, so that the description of the dynamic characteristic of the LEO satellite channel is difficult to realize, and the accuracy of the description of the low-orbit satellite channel characteristic cannot be ensured. For another example, in a patent with publication number CN 114448539A, entitled "a satellite mobile channel modeling method based on geometry and probability statistics composite application", a satellite mobile channel modeling method based on geometry and probability statistics composite application is disclosed, which simulates large-scale fading variation of different satellites through a geometric locus of LEO motion, realizes multi-path signal variation description of small-scale fading based on probability statistical data, and finally realizes multi-state channel characteristic description; however, in the process of combining large-scale fading and small-scale fading, the influence mechanism of the geometric relative relationship on the small-scale fading characteristics cannot be described only through the markov state transition process, so that the description accuracy of the LEO satellite communication channel characteristics is low. As can be seen from the above, although the conventional satellite channel modeling method can implement channel description of a low-orbit satellite, it has a problem of low accuracy of channel description, and in order to improve the accuracy of communication channel characteristic description of the low-orbit satellite, the present application discloses a low-orbit satellite channel modeling method and apparatus with a dual-sphere-center angular body 3D geometry.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps.
Fig. 1 is a schematic flow chart of a method for modeling a low-earth orbit satellite channel with a dual-sphere-center cube 3D geometry according to an embodiment of the present invention, and as shown in fig. 1, the method for modeling a low-earth orbit satellite channel with a dual-sphere-center cube 3D geometry at least includes steps S10 to S50.
Step S10: the method comprises the steps of obtaining communication parameters and geometric parameters used for constructing the double-sphere-center angle body, wherein the geometric parameters comprise orbit height, earth radius, satellite position information and receiving end position information, and the communication parameters comprise communication frequency, transmission wavelength and electromagnetic wave propagation speed.
In this step, the geometric parameters and communication parameters may be determined according to the actual simulated scene, which is a set of preset values or input values. In some embodiments, after the geometric parameters are obtained, a 3D geometric model with two spherical centers may be further constructed based on the geometric parameters, where the first spherical center uses the center of the earth as a vertex and the second spherical center uses the receiving end as a vertex. In some embodiments, for the pre-constructed 3D geometric model structure of the dual-sphere-center cube, the geometric parameters may be determined according to the pre-constructed 3D geometric model structure of the dual-sphere-center cube, wherein the satellite position information includes an initial access elevation angle, an LOS path arrival azimuth angle, and the like. The structure of the 3D geometric model of the double-spherical-center cube is shown in FIG. 2, H represents the height of the orbit, R E Representing the radius of the earth, UE the receiver location information, LEO a low orbit satellite,
indicates the LOS path to elevation angle, θ los Indicating the LOS path arrival azimuth, phi the initial access elevation,
represents the elevation of arrival distribution of the s-th multipath,
indicating the azimuthal distribution of arrival of the s-th multipath, D los Which represents the distance of the LOS path,
indicating the distance of the s-th multipath.
Illustratively, according to an embodiment of the invention, a 3D geometric model of a dual-sphere-center cube is constructed through the acquired geometric parameters based on the motion characteristics of the low-earth orbit satellite. Referring to fig. 2, the outer sphere center cube (the first sphere center cube) has the earth center as the vertex, and the satellite orbit plane constitutes an outer curved surface, which characterizes the geometric motion of the low-earth satellite. The inner sphere center angle body (the second sphere center angle body) takes the receiving end as a vertex, and scattering points related to the multipath effect are distributed on the spherical crown curved surface of the second sphere center angle body. During specific construction, the shapes of the orbit surface and the earth sphere of the satellite are approximate to a sphere, and a double-sphere-center angle geometric model is constructed according to the initial access elevation angle phi of the low-orbit satellite in the process of passing the top.
The application provides a low-orbit satellite-ground link time-varying non-stationary channel model based on a double-sphere-center angle body structure, wherein the model mainly comprises free space loss, shadow fading and small-scale fading parts. The large-scale fading mainly considers free space loss and shadow fading, and for other fading effects (such as flicker effect, cloud and rain fading and the like) existing in the large-scale fading, the fading is approximated to be a determined constant because the numerical change of the fading is related to long-term environment statistics; while for small scale fading effects the following assumptions exist: 1) Multipath signals are caused only by scatterers near the ground receiving end; 2) Only single reflection of the multipath signals is considered in the scattering process of the scatterer, and the influence of lower signal power after multiple reflections on channel response can be ignored; 3) The receiving end antenna is an omnidirectional antenna and can receive signals from all directions. Because the large-scale fading effect is mainly embodied in two aspects of free space loss and shadow fading effect, the channel impulse of the low-orbit satellite is h (t) = p correspondingly l (t)×s f (t)×s s (t), where h (t) denotes the channel impulse response, p l (t) represents the free space loss, s f (t) denotes shadow fading, s s (t) represents a small scale fading effect.
Step S20: and constructing a free space loss model based on the geometric parameters and the communication parameters.
Since the free space loss is related to the geometric position relationship between the satellite and the receiving end and the communication parameter, after the geometric parameter and the communication parameter are obtained based on step S10, a free space loss model can be further constructed based on the obtained geometric parameter and the obtained communication parameter.
Illustratively, before constructing the free space loss model, geometric parameters and communication parameter information are determined, wherein the geometric parameters comprise orbit height, earth radius, satellite position information, receiving end position information and the like, and the communication parameters comprise communication frequency, transmission wavelength, electromagnetic wave propagation speed and the like. At this time, the expression of the free space loss model constructed based on the relative distance between the satellite and the receiving end and the communication frequency is as follows:
wherein p is l (t) represents free space loss, f c Denotes a communication frequency (MHz), λ denotes a transmission wavelength (m), c denotes an electromagnetic wave propagation speed, and d (t) denotes a time-varying transmission distance (km) between a satellite transmitting end and a receiving end. The transmission distance D (t) is related to the geometric parameters in the double-sphere-center angle body 3D model structure, so that the transmission distance D (t) can be obtained according to the geometric position relation between the transmitting end and the receiving end
R E Represents the radius of the earth, H represents the orbital altitude,
representing the time-varying LOS path angle of elevation, θ los (t) represents the time-varying LOS path arrival azimuth.
Step S30: the method comprises the steps of obtaining first measurement data of a low-orbit satellite in the process of passing the top, wherein the first measurement data comprise satellite signals, determining a receiving end communication elevation angle range, carrying out interval division on the receiving end communication elevation angle range, and fitting shadow fading of the low-orbit satellite in different intervals in the process of passing the top into a dynamic shadow fading Gaussian mixed distribution model with time-varying parameters based on the first measurement data.
In the step, a fitting method of mixed Gaussian distribution is provided for the multimodal and asymmetric characteristics of shadow fading level distribution, and a mapping relation between a weight factor and a time-varying elevation angle is established. Wherein, divide the receiving end communication elevation angle scope into intervals, including: determining a level value corresponding to each satellite signal; determining an angle interval based on a numerical variation of the level values; and dividing the receiving end communication elevation angle range into equal interval intervals based on the angle intervals.
The method comprises the following steps of describing the dynamic shadow fading effect of the low-orbit satellite by adopting a Gaussian mixture distribution model, and establishing a mapping relation between a time-varying communication elevation angle and Gaussian mixture distribution parameters. Dividing the communication elevation angle of a receiving end by equal interval delta theta, and fitting shadow fading in different elevation angle ranges in the process of passing the top of the LEO satellite into a time-varying parameter Gaussian mixed distribution model
The corresponding expression is as follows.
Wherein, for each communication elevation angle interval, the Gaussian mixture distribution is composed of M Gaussian distributions with different mean values and variances, delta theta represents the angle interval, and s f Represents a shadow fading, ε m A weight value representing a Gaussian distribution corresponding to the mth interval, the weight value being related to a time-varying communication elevation angle and satisfying sigma epsilon m ＝1，ε m M > 0, denotes the number of divided intervals, p m The probability of the gaussian distribution corresponding to the mth interval is shown.
Representing a set of gaussian distribution weights and gaussian distribution parameters,
a set of mean and variance parameters representing each independent gaussian distribution process.
According to the low-orbit satellite channel modeling method of the double-sphere-center angle body 3D geometrical structure, the shadow fading is fitted through the mixed Gaussian distribution according to the measurement statistical data of the shadow fading in the satellite overhead process, and the mapping relation between the weight factor and the time-varying elevation angle is established, so that the shadow fading of the low-orbit satellite channel can be accurately described based on the parameter time-varying dynamic shadow fading Gaussian mixed distribution model.
Step S40: the method comprises the steps of obtaining second measurement data of a low-orbit satellite in the process of passing the top, fitting the multipath arrival angle of the low-orbit satellite in the process of passing the top into a parameter time-varying Laplace distribution model based on the second measurement data, and determining a small-scale fading channel impulse response model based on the fitted Laplace distribution model.
In this step, the position of the scattering point is limited on the surface of the spherical crown near the receiving end according to the effective access capacity range of the terminal, the distribution of the scattering point is directly related to the time-varying communication elevation angle (refer to fig. 3), and the multi-path distribution description method of the spherical crown effective scattering area can realize the continuous simulation of the multi-path life and death process in the satellite overhead process.
Illustratively, a small-scale fading channel impulse response model is constructed first, and the expression of the small-scale fading Channel Impulse Response (CIR) is as follows:
wherein ssf los (t) denotes the small-scale fading channel impulse response of the direct path, ssf nlos (t) represents the small-scale fading channel impulse response of multipath, K (t) represents the time-varying Rice Factor (Rician Factor), f los Represents the direct path Doppler shift, phi los (t) represents the time-varying received phase of the direct path, S represents the total number of multipath rays,
indicating the s-th multipath doppler shift,
representing the time-varying received phase of the s-th multipath.
And fitting the path arrival elevation angle and the path arrival azimuth angle of the low-orbit satellite in the process of passing the top to a Laplacian distribution model with time-varying parameters based on the second measurement data. Because the communication elevation angle of the low-orbit satellite and the user terminal is rapidly changed, the user terminal receives multipath components from surrounding scatterers, and the elevation angle is changed at any time to present a dynamic characteristic; that is, the time delay and arrival angle distribution of the multipath signals dynamically change along with the communication elevation angle, and the channel has time-varying non-stationary characteristics; the effective communication access elevation angle range of the low orbit satellite is limited, and the spatial distribution of the arrival angle of the multipath signal is not uniformly distributed in all directions but is intensively distributed in a spherical crown scattering plane. Therefore, the multi-path distribution of the spherical crown effective scattering area is provided based on the periodic numerical variation characteristics of the LOS path AAoA (azimuth angle of arrival) and the EAoA (elevation angle of arrival) in the satellite overhead process
And theta los (t) the distribution of effective multipath scattering points exhibits a time-varying characteristic. The schematic structure diagram of the multi-path distribution description of the spherical cap-shaped effective scattering area is shown in fig. 3.
Furthermore, the distribution of scattering points on the surface of the spherical crown at the receiving end determines the spatial arrival angle of the multipath signal
There are many types of distribution, functions that describe the spatial distribution of angles of arrival, such as gaussian distribution, uniform distribution, von mises distribution, laplace distribution, and the like. Considering the existence of significant LOS paths in low-orbit satellite channels, the present invention employs a Laplace distribution
And realizing the description of the multipath angle-of-arrival distribution. The PDF (probability density function) is shown as follows:
Θ is the value of the spatial angle of arrival (AAoA, EAoA), χ is the mean square error of the angular power spectrum (PAS),
is a normalization factor that makes the integral value 1.
Wherein, the distribution of the multipath scattering points is limited by the spherical crown effective scattering area, when the receiving end is initially accessed to the elevation phi = pi/6, the distribution range of the arrival angle of the multipath signal
And the energy of the multi-path signal is mostly concentrated near the LOS path, so the multi-path signal
And
the PDF of the distribution is as follows.
Wherein the content of the first and second substances,
and
respectively showing the distribution range of the LOS path to the azimuth angle and the distribution range of the LOS path to the elevation angle,
χ represents the mean square error of the angular power spectrum, β and β' are normalization factors,
θ los (t) and
respectively, representing a time-varying LOS path arrival azimuth angle and a LOS path arrival elevation angle. In this embodiment, since the range of the multipath signal EAoA is limited, the normalization factor β' is set to
In the expression, the corresponding relation between the multipath signal arrival angle distribution and the time-varying communication elevation angle is established; namely, the multipath distribution description method of the spherical crown effective scattering area realizes the effective representation of the multipath evolution process in the satellite over-the-top process.
Step S50: and determining a channel impulse response model of the low-orbit satellite based on the free space loss model, the dynamic shadow fading mixed Gaussian distribution model and the small-scale fading channel impulse response model.
In this step, after the free space loss model, the dynamic shadow fading gaussian distribution model and the small-scale fading channel impulse response model are determined based on the above steps S20 to S40, h (t) = p is further determined l (t)×s f (t)×s s (t) determining a channel impulse response model for the low orbit satellite. Wherein h (t) represents the channel impulse response of the low orbit satellite, p l (t) represents the free space loss, s f (t) denotes shadow fading, s s (t) denotes small scale fading.
In the embodiment, aiming at the problem of non-stationary time-varying characteristic description of shadow fading and small-scale fading caused by high-speed complex relative motion between a low-orbit satellite and a receiving end, the precise description of the channel characteristic is realized by a low-orbit satellite earth link time-varying non-stationary channel modeling method based on a double-sphere-center angle body structure. The method is characterized in that fitting of dynamic shadow fading is realized through mixed Gaussian distribution according to measurement statistical data of shadow fading in the satellite overhead process, and a mapping relation between a weight factor and a time-varying elevation angle is established. In addition, the continuous simulation of the multipath life-time process in the satellite overhead process is realized by a multipath distribution description method of the spherical crown-shaped effective scattering area. In conclusion, the channel model provided by the application divides the channel characteristics of the satellite-to-ground link of the LEO satellite into three main parts, namely free space loss, shadow fading and small-scale fading, and effectively realizes high-precision modeling and simulation of the channel transmission characteristics of the satellite-to-ground link of the LEO satellite.
Accordingly, the present invention also provides a system for modeling a low-orbit satellite channel in a 3D geometry with dual-centroid angles, the system comprising a processor and a memory, the memory having stored therein computer instructions, the processor being configured to execute the computer instructions stored in the memory, the system implementing the steps of the method according to any of the above embodiments when the computer instructions are executed by the processor.
Fig. 4 is a schematic diagram of a logical structure of a low-orbit satellite channel modeling system with a double-sphere-center angle body 3D geometric structure in a channel simulation process according to an embodiment of the present invention, and as shown in fig. 4, parameters are first input, where the parameters include an orbit height, a terminal moving speed, a relative position, a communication frequency point, a communication bandwidth, a channel scene, and the like, and then large-scale related parameters are generated based on the geometric parameters and the communication parameters, and then K-factor and shadow fading parameters are calculated to generate channel parameters, and finally, a channel impulse response of a low-orbit satellite is determined.
In the above embodiment, in the development process of the channel simulator, all functional modules of the channel are implemented in the FPGA portion, which results in high structural complexity of the logic circuit; channel slowly-varying parameters caused by partial large-scale fading and nonlinear effects are realized through a software platform, and the channel parameters are updated within a longer time range (ms/ns); the simulation of real-time and rapid change of the depicting channel is realized by a high-speed hardware platform, and the channel parameters are updated in a short time (ns/us). The system divides the updating frequency of the channel parameters into three levels when realizing channel simulation: fixed numerical value, relevant interval updating and single sampling interval updating; by the method, redundant parameter simulation can be effectively reduced, and the hardware processing efficiency is improved.
In addition, the invention also discloses a computer readable storage medium, on which a computer program is stored, which when executed by a processor implements the steps of the method according to any of the above embodiments.
Through the embodiment, the low-orbit satellite channel modeling method and the low-orbit satellite channel modeling device with the double-sphere-center angle 3D geometric structure realize high-precision modeling of dynamic shadow fading level distribution under the influence of time-varying communication elevation angles based on a hybrid Gaussian distribution fitting method, and solve the problems of effective modeling and description of a multipath effect evolution process in a satellite overhead process through a multipath distribution description method of a spherical-crown-shaped effective scattering area, so that the precision of low-orbit satellite communication channel characteristic description is improved. In addition, the updating frequency of the channel parameters is divided into three levels when the channel is simulated: the method has the advantages that the method can effectively reduce redundant parameter simulation and improve hardware processing efficiency by fixing numerical values, updating related intervals and updating single sampling intervals.
Those of ordinary skill in the art will appreciate that the various illustrative components, systems, and methods described in connection with the embodiments disclosed herein may be implemented as hardware, software, or combinations of both. Whether this is done in hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments can be stored in a machine-readable medium or transmitted by a data signal carried in a carrier wave over a transmission medium or a communication link. A "machine-readable medium" may include any medium that can store or transfer information. Examples of a machine-readable medium include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio Frequency (RF) links, and so forth. The code segments may be downloaded via computer networks such as the internet, intranets, etc.
It should also be noted that the exemplary embodiments mentioned in this patent describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above-described steps, that is, the steps may be performed in the order mentioned in the embodiments, may be performed in an order different from the order in the embodiments, or may be performed simultaneously.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments in the present invention.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made to the embodiment of the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for modeling a low earth orbit satellite channel in a 3D geometry with dual spherical centers, the method comprising:
the method comprises the steps of obtaining communication parameters and geometric parameters for constructing a double-sphere-center angle body, wherein the geometric parameters comprise orbit height, earth radius, satellite position information and receiving end position information, and the communication parameters comprise communication frequency, transmission wavelength and electromagnetic wave propagation speed;
constructing a free space loss model based on the geometric parameters and the communication parameters;
acquiring first measurement data of a low-orbit satellite in the process of passing the top, wherein the first measurement data comprise satellite signals, determining a receiving end communication elevation angle range, carrying out interval division on the receiving end communication elevation angle range, and fitting shadow fading of the low-orbit satellite in different intervals in the process of passing the top into a dynamic shadow fading Gaussian mixed distribution model with time-varying parameters based on the first measurement data;
acquiring second measurement data of a low-orbit satellite in a process of passing through the top, wherein the second measurement data comprise multipath arrival angles of the low-orbit satellite, fitting the multipath arrival angles of the low-orbit satellite in the process of passing through the top into a parameter time-varying Laplace distribution model based on the second measurement data, and determining a small-scale fading channel impulse response model based on the fitted Laplace distribution model;
and determining a channel impulse response model of the low-orbit satellite based on the free space loss model, the dynamic shadow fading mixed Gaussian distribution model and the small-scale fading channel impulse response model.
2. The method for modeling a low-earth orbit satellite channel with a 3D geometry having a double-centroid angle according to claim 1, wherein the free space loss is expressed as:
wherein f is c Denotes a communication frequency, λ denotes a transmission wavelength, c denotes an electromagnetic wave propagation velocity, d (t) denotes a time-varying transmission distance between a satellite transmitting end and a receiving end,
R E representing the radius of the earth, H the orbit altitude,
representing the time-varying LOS path angle of elevation, θ los (t) represents a time-varying LOS path arrival azimuth.
3. The method for modeling a low-earth orbit satellite channel with a 3D geometry having a double-sphere-center angle according to claim 1, wherein the step of interval dividing the elevation angle range of the receiving end communication comprises:
determining a level value corresponding to each satellite signal;
determining an angle interval based on a numerical variation of the level values;
and dividing the receiving end communication elevation angle range into equal interval intervals based on the angle intervals.
4. The method of claim 3, wherein the dynamic shadow fading Gaussian mixture distribution model is expressed by the following formula:
where Δ θ represents the angular interval, s f Represents a shadow fading, ε m Represents the weight of the Gaussian distribution corresponding to the mth interval, and ∑ ε m ＝1,ε m >0, M represents the total number of divided intervals,
ξ represent the set of gaussian distribution weights and gaussian distribution parameters,
set of mean and variance parameters, p, representing each independent Gaussian distribution process m The probability of the gaussian distribution corresponding to the mth interval is shown.
5. The method of modeling a low-earth orbit satellite channel with a 3D geometry having dual spherical centers as recited in claim 1, wherein the expression of the time-varying parameter laplacian distribution model is:
wherein, the first and the second end of the pipe are connected with each other,
and
respectively showing the distribution range of the LOS path to the azimuth angle and the distribution range of the LOS path to the elevation angle,
χ represents the mean square error of the angular power spectrum, β and β ′ Are all the normalization factors, and the normalization factors,
θ los (t) and
respectively, representing a time-varying LOS path arrival azimuth angle and a LOS path arrival elevation angle.
6. The method for modeling the low-orbit satellite channel with a 3D geometry having dual spherical centroids according to claim 5, wherein the expression of the small-scale fading channel impulse response model is as follows:
wherein ssf los (t) denotes the small-scale fading channel impulse response of the direct path, ssf nlos (t) represents the small-scale fading channel impulse response of multipath, K (t) represents the time-varying Rice factor, f los Indicating the direct path Doppler shift, phi los (t) represents the time-varying received phase of the direct path, S represents the total number of multipath rays,
indicating the s-th multipath doppler shift,
representing the time-varying received phase of the s-th multipath.
7. The method for modeling the channel of the low-orbit satellite with the 3D geometry of the double-sphere-center angle body according to claim 1, wherein the expression of the channel impulse response model of the low-orbit satellite is as follows:
h(t)＝p l (t)×s f (t)×s s (t)；
wherein h (t) represents the channel impulse response of the low orbit satellite, p l (t) represents the free space loss, s f (t) denotes shadow fading, s s (t) denotes small scale fading.
8. The method of modeling a low-earth orbit satellite channel for a dual-centroid angular 3D geometry of claim 1, further comprising: and constructing a 3D geometric model of the double-sphere-center angle body based on the geometric parameters, wherein the first sphere-center angle body takes the earth sphere as a vertex, and the second sphere-center angle body takes the receiving end as a vertex.
9. A system for low earth orbit satellite channel modeling of a 3D geometry of a dual spherical sector comprising a processor and a memory, wherein the memory has stored therein computer instructions for executing the computer instructions stored in the memory, the system implementing the steps of the method as claimed in any one of claims 1 to 8 when the computer instructions are executed by the processor.
10. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 8.
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| CN116455456A (en) * | 2023-04-28 | 2023-07-18 | 大连海事大学 | End-to-end communication performance analytic model establishment method based on low orbit satellite constellation |
| CN116633423A (en) * | 2023-07-24 | 2023-08-22 | 成都本原星通科技有限公司 | Low-orbit satellite auxiliary communication method based on reconfigurable intelligent surface |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116455456A (en) * | 2023-04-28 | 2023-07-18 | 大连海事大学 | End-to-end communication performance analytic model establishment method based on low orbit satellite constellation |
| CN116455456B (en) * | 2023-04-28 | 2024-01-02 | 大连海事大学 | End-to-end communication performance analytic model establishment method based on low orbit satellite constellation |
| CN116633423A (en) * | 2023-07-24 | 2023-08-22 | 成都本原星通科技有限公司 | Low-orbit satellite auxiliary communication method based on reconfigurable intelligent surface |
| CN116633423B (en) * | 2023-07-24 | 2023-10-13 | 成都本原星通科技有限公司 | Low-orbit satellite auxiliary communication method based on reconfigurable intelligent surface |
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