Low-orbit satellite channel modeling method and device based on double-sphere center-angle body 3D geometric structure

Abstract

The present invention provides a low-orbit satellite channel modeling method and device of a double-sphere center angle body 3D geometric structure, including: obtaining communication parameters and geometric parameters for constructing a double-sphere center angle body; constructing a free space loss model; obtaining first measurement data, determining the communication angle range of the receiving end and dividing the intervals, fitting the shadow fading of the low-orbit satellite in different intervals during the overpass process to a dynamic shadow fading Gaussian mixed distribution model with time-varying parameters based on the first measurement data; obtaining second measurement data, fitting the multipath arrival angle of the low-orbit satellite during the overpass process to a Laplace distribution model with time-varying parameters, determining a small-scale fading channel impulse response model based on the Laplace distribution model; determining the 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 description of the characteristics of the low-orbit satellite communication channel.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a low-orbit satellite channel modeling method and device with a double-sphere center angle body 3D geometric structure. Background Art

[0002] At present, 5G mobile communication systems have been commercialized on a large scale, and countries around the world have started research and exploration of 6G mobile communication technology; traditional ground networks cannot solve the problem of high-speed data communication in maritime, aviation and other areas not yet covered by ground networks. Satellite communication has the characteristics of wide coverage and large communication capacity, and is an effective means to solve the above problems. It will become an important part of the 6G communication system and provide global seamless access capabilities; the International Organization for Standardization 3GPP has focused on the role and impact of satellite communication on 6G mobile networks in the relevant standards of non-terrestrial communication networks; 6G mobile communication technology integrated with satellite communication will provide a forward-looking foundation for new information service fields such as virtual reality, smart cities, and unmanned operations.

[0003] The low-orbit satellite-to-ground link has dynamic time-varying characteristics such as high Doppler frequency shift, large communication delay, and nonlinear memory effect. It is urgent to analyze and model the channel characteristics of low-orbit satellites. The low-orbit satellite communication frequency band is relatively high, and the low-earth orbit brings high-speed relative motion with the ground receiving terminal, resulting in a large range of Doppler frequency shift and high-speed Doppler change rate (tens of times higher than the ground network). The transmission delay at different time nodes during the low-orbit satellite overpass is different, and the transmission delay is large (tens of milliseconds). At the ground receiving end, the multipath effect caused by different spatial ground scatterers has a significant impact on the Doppler expansion and delay expansion channel characteristics. At the satellite payload end, due to the limited transmission power of the satellite and the low heat dissipation efficiency, it is in a saturation point working state for a long time. The nonlinear memory effect brought by RF devices such as input / output filters and high-power amplifiers causes serious signal distortion. In order to accurately characterize the channel characteristics of the low-orbit satellite-to-ground link and improve the signal transmission quality and transmission rate as much as possible on limited spectrum resources, it is necessary to model and analyze the large-scale fading and small-scale fading characteristics of low-orbit satellites.

[0004] At present, according to the modeling method of channel models, channel models are mainly divided into deterministic models, random models and quasi-random models. Deterministic models are applied in specific scenarios. Before modeling, detailed scene distribution needs to be obtained, and channel transmission characteristics are obtained through simulation. The random model has good universality, and the probability density function of the channel is determined by theoretical calculation and channel measurement statistical parameters. The quasi-random model is based on the data results of channel measurement and the calculation method of the deterministic model, and describes the channel characteristics into deterministic and statistical parts.

[0005] In the invention patent with the publication number CN 113644942 A and the name "A geometry-based 3D MIMO LEO satellite air-ground channel modeling method", a modeling method for calculating time-varying channel parameters such as signal arrival angle, departure angle, and time-varying propagation distance based on the geometric relationship between the mobile LEO (low earth orbit) satellite transmitter, mobile drone terminal, and mobile ground receiver is disclosed. This method considers the scattering phenomenon of wireless signals generated by the drone terminal and the receiver terminal to be concentrated on a sphere centered on the receiver, and based on this, generates a channel impulse response from the 3D MIMO LEO satellite transmitter antenna to the relay antenna and then to the receiver antenna; this method only describes the change in the relative position relationship between the transmitter and the receiver, and does not achieve accurate description and modeling of the time-varying characteristics of the multipath arrival angle distribution during the satellite passing overhead, so it cannot ensure the accuracy of the low-orbit satellite channel characteristic description.

[0006] From the above content, it can be seen that the existing low-orbit satellite channel modeling method has the technical problem of low accuracy in describing channel characteristics. Therefore, how to improve the accuracy of low-orbit satellite communication channel characteristic description is a technical problem that needs to be solved urgently. Summary of the invention

[0007] In view of this, the present invention provides a method and device for low-orbit satellite channel modeling with a double-sphere center angle body 3D geometric structure to solve one or more problems existing in the prior art.

[0008] According to one aspect of the present invention, the present invention discloses a low-orbit satellite channel modeling method of a double-sphere center angle body 3D geometric structure, the method comprising:

[0009] Acquire communication parameters and geometric parameters for constructing a double-sphere center angle body, wherein the geometric parameters include orbital altitude, earth radius, satellite position information, and receiving end position information, and the communication parameters include communication frequency, transmission wavelength, and electromagnetic wave propagation speed;

[0010] Constructing a free space loss model based on the geometric parameters and communication parameters;

[0011] Acquire first measurement data of a low-orbit satellite during a process of passing overhead, the first measurement data including a satellite signal, determine a communication elevation angle range of a receiving end, divide the communication elevation angle range of the receiving end into intervals, and fit shadow fading of the low-orbit satellite in different intervals during the process of passing overhead into a dynamic shadow fading Gaussian mixture distribution model with time-varying parameters based on the first measurement data;

[0012] Acquire second measurement data of the low-orbit satellite during the process of passing overhead, the second measurement data including the multipath arrival angle of the low-orbit satellite, fit the multipath arrival angle of the low-orbit satellite during the process of passing overhead into a Laplace distribution model with time-varying parameters based on the second measurement data, and determine a small-scale fading channel impulse response model based on the fitted Laplace distribution model;

[0013] The channel impulse response model of the low-orbit satellite is determined based on the free space loss model, the dynamic shadow fading mixed Gaussian distribution model and the small-scale fading channel impulse response model.

[0014] In some embodiments of the present invention, the free space loss is expressed as:

[0015]

[0016] Among them, f c represents the communication frequency, λ represents the transmission wavelength, c represents the electromagnetic wave propagation speed, d(t) represents the time-varying transmission distance between the satellite transmitter and the receiver, R E represents the radius of the earth, H represents the orbital altitude, represents the time-varying LOS path arrival elevation angle, θ los (t) represents the time-varying LOS path arrival azimuth.

[0017] In some embodiments of the present invention, dividing the receiving end communication angle range into intervals includes:

[0018] Determine the level value corresponding to each satellite signal;

[0019] Determining the angle interval based on the numerical change of the level value;

[0020] The receiving end communication angular range is divided into equally spaced intervals based on the angular interval.

[0021] In some embodiments of the present invention, the expression of the dynamic shadow fading Gaussian mixture distribution model is:

[0022]

[0023] Where Δθ represents the angle interval, s f represents shadow fading, εm 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 represents the set of Gaussian distribution weights and Gaussian distribution parameters, represents the mean and variance parameter set of each independent Gaussian distribution process, pm Represents the probability of the Gaussian distribution corresponding to the mth interval.

[0024] In some embodiments of the present invention, the expression of the Laplace distribution model with time-varying parameters is:

[0025]

[0026]

[0027] in, and They represent the distribution range of the LOS path arrival azimuth angle and the distribution range of the LOS path arrival elevation angle, respectively. χ represents the mean square error of the angular power spectrum, β and β′ are normalization factors, θ los (t) and They represent the time-varying LOS path arrival azimuth and LOS path arrival elevation, respectively.

[0028] In some embodiments of the present invention, the expression of the impulse response model of the small-scale fading channel is:

[0029]

[0030] Among them, ssf los (t) represents the impulse response of the small-scale fading channel in the direct path, ssf nlos (t) represents the impulse response of the multipath small-scale fading channel, K(t) represents the time-varying Ricean factor, and f los represents the direct path Doppler shift, φ los (t) represents the time-varying receiving phase of the direct path, S represents the total number of multipath rays, represents the s-th multipath Doppler shift, represents the time-varying received phase of the s-th multipath.

[0031] In some embodiments of the present invention, the channel impulse response model of the low-orbit satellite is expressed as:

[0032] h(t)=p l (t)×s f (t)×s s (t);

[0033] Where h(t) represents the channel impulse response of the low-orbit satellite, p l (t) represents free space loss, s f (t) represents shadow fading, s s (t) represents small-scale fading.

[0034] In some embodiments of the present invention, the method further comprises: constructing a double-spherical-center angle body 3D geometric model based on the geometric parameters, wherein a first spherical-center angle body has the center of the earth as a vertex, and a second spherical-center angle body has the receiving end as a vertex.

[0035] According to another aspect of the present invention, a low-orbit satellite channel modeling system with a dual-sphere center angle body 3D geometric structure is also disclosed. The system includes a processor and a memory, wherein the memory stores computer instructions, and the processor is used to execute the computer instructions stored in the memory. When the computer instructions are executed by the processor, the system implements the steps of the method described in any of the above embodiments.

[0036] According to another aspect of the present invention, a computer-readable storage medium is disclosed, on which a computer program is stored. When the program is executed by a processor, the steps of the method described in any of the above embodiments are implemented.

[0037] The low-orbit satellite channel modeling method and device of the double-sphere center angle body 3D geometric structure disclosed in the embodiment of the present invention implement the fitting of dynamic shadow fading through mixed Gaussian distribution based on the measurement data of shadow fading during the satellite passing over the top, establish a mapping relationship between weight factors and time-varying elevation angles, thereby obtaining a dynamic shadow fading Gaussian mixed distribution model with time-varying parameters; and based on the measurement data of the multipath arrival angle during the satellite passing over the top, fit the multipath arrival angle of the low-orbit satellite during the passing over the top into a Laplace distribution model with time-varying parameters; and then use the channel impulse response model of the low-orbit satellite constructed based on the above model to describe the low-orbit satellite channel, thereby improving the accuracy of the description of the communication channel characteristics.

[0038] Additional advantages, purposes, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The purposes and other advantages of the present invention may be achieved and obtained by the structures specifically pointed out in the written description, claims, and drawings.

[0039] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention. The components in the drawings are not drawn to scale, but are only for illustrating the principles of the present invention. In order to facilitate the illustration and description of some parts of the present invention, the corresponding parts in the drawings may be enlarged, that is, they may become larger relative to other components in the exemplary device actually manufactured according to the present invention. In the drawings:

[0041] Figure 1 The figure is a flow chart of a method for modeling a low-orbit satellite channel with a double-sphere center angle body 3D geometric structure according to an embodiment of the present invention.

[0042] Figure 2 It is a structural schematic diagram of a double-sphere center angle body 3D geometric model of a low-orbit satellite ground link according to an embodiment of the present invention.

[0043] Figure 3 A schematic structural diagram of a spherical crown-shaped effective scattering region multipath distribution description according to an embodiment of the present invention.

[0044] Figure 4 The figure is a schematic diagram of the logical structure of a low-orbit satellite channel modeling system with a dual-sphere center angle body 3D geometric structure during a channel simulation process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0046] It should be noted here that in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0047] It should be emphasized that the terms “include / comprises / has” when used herein refer to the presence of features, elements, steps or components, but do not exclude the presence or addition of one or more other features, elements, steps or components.

[0048] For the existing low-orbit satellite channel modeling methods, there is generally a characteristic of low accuracy in describing the characteristics of the low-orbit satellite channel. For example, a patent application with publication number CN 112436882 B and titled "LEO Satellite Channel Modeling Method and Device Based on Dual Markov Model" discloses a shadow fading description method based on a first-order Markov multi-state channel model. This method uses measured data to describe the dynamic birth and death process of small-scale fading multipaths, and obtains the Ricean channel model of the LEO satellite by determining the channel parameters; however, in this method, the influence of the change in communication angle on the multipath signal during the low-orbit satellite passing over the top is not reflected in the calculation of the Ricean factor and the description of the dynamic changes of small-scale fading. It is difficult to describe the dynamic characteristics of the LEO satellite channel, and thus it is impossible to ensure the accuracy of the description of the characteristics of the low-orbit satellite channel. For another example, the patent with publication number CN 114448539 A and titled "Satellite mobile channel modeling method based on composite application of geometry and probability statistics" discloses a satellite mobile channel modeling method based on composite application of geometry and probability statistics. The method simulates the large-scale fading changes of different satellites through the geometric trajectory of LEO movement, and realizes the description of multipath signal changes of small-scale fading based on probability statistics, and finally realizes the description of multi-state channel characteristics; however, in the process of combining large-scale fading with small-scale fading, the influence mechanism of geometric relative relationship on small-scale fading characteristics cannot be described only through the Markov state transition process, resulting in low accuracy of LEO satellite communication channel characteristic description. From the above content, it can be seen that although the existing satellite channel modeling methods can realize the channel description of low-orbit satellites, they all have the problem of low channel description accuracy. In order to improve the accuracy of low-orbit satellite communication channel characteristic description, the present application discloses a low-orbit satellite channel modeling method and device with a double-sphere center angle body 3D geometric structure.

[0049] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0050] Figure 1 FIG. 1 is a flow chart of a method for modeling a low-orbit satellite channel of a double-sphere center angle body 3D geometric structure according to an embodiment of the present invention. Figure 1 As shown, the low-orbit satellite channel modeling method of the double-sphere center angle body 3D geometric structure at least includes steps S10 to S50.

[0051] Step S10: Acquire communication parameters and geometric parameters for constructing a double-sphere center angle body, wherein the geometric parameters include orbital altitude, earth radius, satellite position information, and receiving end position information, and the communication parameters include communication frequency, transmission wavelength, and electromagnetic wave propagation speed.

[0052] In this step, the geometric parameters and communication parameters can be determined according to the actual simulation scenario, which is a set of preset values ​​or input values. In some embodiments, after the geometric parameters are obtained, a dual-sphere center angle body 3D geometric model can be further constructed based on the geometric parameters, wherein the first sphere center angle body has the center of the earth as the vertex, and the second sphere center angle body has the receiving end as the vertex. In some embodiments, for a pre-constructed dual-sphere center angle body 3D geometric model structure, the geometric parameters can be determined according to a pre-established dual-sphere center angle body 3D geometric model structure, wherein the satellite position information includes the initial access elevation angle, the LOS path arrival elevation angle, and the LOS path arrival azimuth angle, etc. The dual-sphere center angle body 3D geometric model structure is as follows: Figure 2 As shown, in Figure 2 In the figure, H represents the orbit height, R E represents the radius of the earth, UE represents the receiving end location information, LEO represents a low-orbit satellite, represents the LOS path arrival elevation angle, θ los represents the LOS path arrival azimuth, Φ represents the initial access elevation angle, represents the elevation angle distribution of the s-th multipath, represents the arrival azimuth distribution of the sth multipath, D los Indicates the LOS distance, Indicates the distance of the sth multipath.

[0053] Exemplarily, an embodiment of the present invention constructs a 3D geometric model of a double-sphere center angle body based on the motion characteristics of a low-orbit satellite using the acquired geometric parameters. Figure 2 The outer spherical center angle body (first spherical center angle body) takes the center of the earth as the vertex, and the satellite orbital plane constitutes the outer curved surface, which characterizes the geometric motion characteristics of the low-orbit satellite. The inner spherical center angle body (second spherical center angle body) takes the receiving end as the vertex, and the scattering points related to the multipath effect are distributed on the spherical cap curved surface of the second spherical center angle body. In the specific construction, the satellite orbital plane and the shape of the earth are approximated as a sphere, and the double spherical center angle geometric model is constructed according to the initial access elevation angle Φ of the low-orbit satellite passing through the top.

[0054] Based on the above-mentioned dual-sphere center angle body geometric model of the low-orbit satellite satellite-to-ground link, the present application proposes a time-varying non-stationary channel model of the low-orbit satellite satellite-to-ground link based on the dual-sphere center angle body structure. The model mainly includes free space loss, shadow fading, and small-scale fading parts. Among them, large-scale fading mainly considers free space loss and shadow fading, and for other fading effects (scintillation effect, cloud and rain fading, etc.) existing in large-scale fading, because their numerical changes are related to long-term environmental statistics, their fading is approximated as a certain constant; and for small-scale fading effects, there are the following assumptions: 1) Multipath signals are only caused by scatterers near the ground receiving end; 2) The scattering process of multipath signals in the scatterer only considers a single reflection, and the signal power after multiple reflections is low and the impact on the channel response can be ignored; 3) The receiving antenna is an omnidirectional antenna that can receive signals from all directions. Since the large-scale fading effect is mainly reflected in the two aspects of free space loss and shadow fading effect, the channel impulse response of the low-orbit satellite should be h(t)=p l (t)×s f (t)×s s (t), where h(t) represents the channel impulse response and p l (t) represents free space loss, s f (t) represents shadow fading, s s (t) represents the small-scale fading effect.

[0055] Step S20: constructing a free space loss model based on the geometric parameters and communication parameters.

[0056] Since the free space loss is related to the geometric position relationship between the satellite and the receiving end and the communication parameters, after the geometric parameters and communication parameters are obtained based on step S10, a free space loss model can be further constructed based on the obtained geometric parameters and communication parameters.

[0057] Exemplarily, before constructing the free space loss model, first determine the geometric parameters and communication parameter information, the geometric parameters include orbital altitude, earth radius, satellite position information and receiving end position information, and the communication parameters include communication frequency, transmission wavelength and electromagnetic wave propagation speed. 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:

[0058]

[0059] Among them, p l (t) represents the free space loss, f crepresents the communication frequency (MHz), λ represents the transmission wavelength (m), c represents the electromagnetic wave propagation speed, and d(t) represents the time-varying transmission distance between the satellite transmitter and the receiver (km). The transmission distance d(t) is related to the geometric parameters in the 3D model structure of the double-sphere center angle body. Therefore, according to the geometric position relationship between the transmitter and the receiver, it can be obtained R E represents the radius of the earth, H represents the orbital altitude, represents the time-varying LOS path arrival elevation angle, θ los (t) represents the time-varying LOS path arrival azimuth.

[0060] Step S30: Acquire first measurement data of the low-orbit satellite during its overpass process, wherein the first measurement data includes a satellite signal, determine a communication angular range of a receiving end, divide the communication angular range of the receiving end into intervals, and fit the shadow fading of the low-orbit satellite in different intervals during its overpass process into a dynamic shadow fading Gaussian mixture distribution model with time-varying parameters based on the first measurement data.

[0061] In this step, a fitting method of mixed Gaussian distribution is proposed for the multi-peak and asymmetric characteristics of shadow fading level distribution, and a mapping relationship between weight factors and time-varying elevation angles is established. The receiving end communication elevation angle range is divided into intervals, including: determining the level value corresponding to each satellite signal; determining the angle interval based on the numerical change of the level value; and dividing the receiving end communication elevation angle range into equally spaced intervals based on the angle interval.

[0062] This step uses the Gaussian mixture distribution model to describe the dynamic shadow fading effect of low-orbit satellites, and establishes a mapping relationship between the time-varying communication angle and the Gaussian mixture distribution parameters. The receiving end communication angle is divided into equal intervals Δθ, and the shadow fading in different elevation angles during the LEO satellite passing through is fitted into a Gaussian mixture distribution model with time-varying parameters. The corresponding expressions are as follows.

[0063]

[0064] Among them, for each communication angle interval, the Gaussian mixture distribution is composed of M Gaussian distributions with different means and variances, Δθ represents the angle interval, s f represents shadow fading, ε m represents the weight of the Gaussian distribution corresponding to the mth interval. The weight value is related to the time-varying belief angle and satisfies ∑ε m =1,ε m > 0, M represents the number of intervals divided, p m Represents the probability of the Gaussian distribution corresponding to the mth interval. represents the set of Gaussian distribution weights and Gaussian distribution parameters, Represents the set of mean and variance parameters of each independent Gaussian distribution process.

[0065] From the above content, it can be seen that the low-orbit satellite channel modeling method of the double-sphere center angle body 3D geometric structure of the present invention is based on the measured statistical data of shadow fading during the satellite passing over the top, and realizes the fitting of dynamic shadow fading through a mixed Gaussian distribution, and establishes a mapping relationship between weight factors and time-varying elevation angles. Therefore, the dynamic shadow fading Gaussian mixture distribution model based on time-varying parameters can accurately describe the shadow fading of the low-orbit satellite channel.

[0066] Step S40: Acquire second measurement data of the low-orbit satellite during its overhead process, wherein the second measurement data includes the multipath arrival angle of the low-orbit satellite, and fit the multipath arrival angle of the low-orbit satellite during its overhead process into a Laplace distribution model with time-varying parameters based on the second measurement data, and determine a small-scale fading channel impulse response model based on the fitted Laplace distribution model.

[0067] In this step, the scattering point position is limited to the spherical cap surface near the receiving end according to the effective access capability range of the terminal. The distribution of scattering points is directly related to the time-varying communication angle (refer to Figure 3 ), the multipath distribution description method of the spherical crown effective scattering area can realize the continuous simulation of the multipath generation and death process during the satellite passing through the top.

[0068] Exemplarily, firstly, a small-scale fading channel impulse response model is constructed, and the small-scale fading channel impulse response (CIR) expression is:

[0069]

[0070] Among them, ssf los (t) represents the impulse response of the small-scale fading channel in the direct path, ssf nlos (t) represents the impulse response of the multipath small-scale fading channel, K(t) represents the time-varying Rician Factor, and f los represents the direct path Doppler shift, φ los (t) represents the time-varying receiving phase of the direct path, S represents the total number of multipath rays, represents the s-th multipath Doppler shift, represents the time-varying received phase of the s-th multipath.

[0071] Furthermore, based on the second measurement data, the elevation angle of arrival and the azimuth angle of arrival of the low-orbit satellite during the overhead process are fitted into a Laplace distribution model with time-varying parameters. Among them, due to the rapid change of the communication elevation angle between the low-orbit satellite and the user terminal, the multipath components received by the user terminal from the surrounding scatterers will show dynamic characteristics with the time-varying elevation angle; that is, the time delay and arrival angle distribution of the multipath signal change dynamically with the communication elevation angle, and the channel shows time-varying non-stationary characteristics; the effective communication access elevation range of low-orbit satellites is limited, and the spatial distribution of the multipath signal arrival angle is not uniformly distributed in all directions, but is concentrated in the spherical crown scattering surface. Therefore, based on the periodic numerical change characteristics of the LOS path AAoA (arrival azimuth) and EAoA (arrival elevation) during the satellite's overhead process, the present application proposes a multipath distribution in the spherical crown effective scattering area. With θ los The effective multipath scattering point distribution under the influence of (t) shows time-varying characteristics. The structural diagram of the multipath distribution description of the spherical crown effective scattering area is shown in Figure 3 shown.

[0072] Furthermore, the distribution of scattering points on the receiving end's spherical cap surface determines the spatial arrival angle of the multipath signal. There are many functions for describing the spatial arrival angle distribution, such as Gaussian distribution, uniform distribution, von Mises distribution and Laplace distribution. Considering the significant LOS path in the low-orbit satellite channel, the present invention adopts Laplace distribution The multipath arrival angle distribution description is realized. Its PDF (probability density function) is shown as follows:

[0073]

[0074] Θ is the spatial angle of arrival (AAoA, EAoA) value, χ is the mean square error of the angular power spectrum (PAS), is the normalization factor that makes the integral value equal to 1.

[0075] Among them, the distribution of multipath scattering points is limited by the spherical crown effective scattering area. When the initial access elevation angle of the receiving end is Φ=π / 6, the arrival angle distribution range of the multipath signal is And the energy of multipath signals is mostly concentrated near the LOS path, so the multipath signal and The PDF of the distribution is shown below.

[0076]

[0077]

[0078] in, and They represent the distribution range of the LOS path arrival azimuth angle and the distribution range of the LOS path arrival elevation angle, respectively. χ represents the mean square error of the angular power spectrum, β and β′ are normalization factors, θ los (t) and They represent the time-varying LOS path arrival azimuth and LOS path arrival elevation, respectively. In this embodiment, since the multipath signal EAoA range is limited, the normalization factor β′ is set to In the above expression, the corresponding relationship between the multipath signal arrival angle distribution and the time-varying belief angle is established; that is, the multipath distribution description method of the spherical crown effective scattering area is used to achieve effective characterization of the multipath evolution process during the satellite passing over the top.

[0079] Step S50: Determine the 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.

[0080] In this step, after the free space loss model, the dynamic shadow fading mixed Gaussian distribution model and the small-scale fading channel impulse response model are determined based on the above steps S20 to S40, the following is further performed based on h(t)=p l (t)×s f (t)×s s (t) determines the channel impulse response model of the low-orbit satellite. Where h(t) represents the channel impulse response of the low-orbit satellite, p l (t) represents free space loss, s f (t) represents shadow fading, s s (t) represents small-scale fading.

[0081] In the above embodiment, in order to describe the non-stationary time-varying characteristics of shadow fading and small-scale fading caused by the high-speed and complex relative motion between the low-orbit satellite and the receiving end, a method for modeling the time-varying non-stationary channel of the low-orbit satellite satellite-to-ground link based on a double-spherical center angle body structure is used to achieve an accurate description of the channel characteristics. That is, according to the measured statistical data of shadow fading during the satellite passing over the top, the dynamic shadow fading is fitted by a mixed Gaussian distribution, and a mapping relationship between the weight factor and the time-varying elevation angle is established. In addition, the multipath distribution description method of the spherical crown effective scattering area is used to achieve continuous simulation of the multipath birth and death process during the satellite passing over the top. In summary, the channel model proposed in this application divides the LEO satellite satellite-to-ground link channel characteristics into three main parts: free space loss, shadow fading, and small-scale fading, which effectively realizes the high-precision modeling and simulation of the LEO satellite satellite-to-ground link channel transmission characteristics.

[0082] Correspondingly, the present invention also provides a low-orbit satellite channel modeling system with a double-sphere center angle body 3D geometric structure, the system comprising a processor and a memory, the memory storing computer instructions, the processor being used to execute the computer instructions stored in the memory, and when the computer instructions are executed by the processor, the system implements the steps of the method described in any of the above embodiments.

[0083] Figure 4 FIG. 1 is a schematic diagram of the logical structure of a low-orbit satellite channel modeling system of a double-sphere center angle body 3D geometric structure during a channel simulation process according to an embodiment of the present invention. Figure 4 As shown in the figure, firstly, the parameters are input, including orbital altitude, terminal movement speed, relative position, communication frequency, communication bandwidth, channel scenario, etc., and then large-scale related parameters are generated based on the above-mentioned geometric parameters and communication parameters, and then the K factor and shadow fading parameters are calculated to generate channel parameters, and finally the channel impulse response of the low-orbit satellite is determined.

[0084] In the above embodiment, during the development of the channel simulator, all the functional modules of the channel are implemented in the FPGA part, which will lead to high complexity of the logic circuit structure; the slowly changing parameters of the channel caused by some large-scale fading and nonlinear effects are implemented through the software platform, and the channel parameters are updated in a longer time range (ms / ns); the simulation that depicts the real-time rapid changes of the channel is implemented through a high-speed hardware platform, and the channel parameters are updated in a short time (ns / us). When implementing channel simulation, the system divides the update frequency of channel parameters into three levels: fixed value, related interval update, and single sampling interval update; this method can effectively reduce redundant parameter simulation and improve hardware processing efficiency.

[0085] In addition, the invention also discloses a computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, the steps of the method described in any of the above embodiments are implemented.

[0086] Through the above embodiments, it can be found that the low-orbit satellite channel modeling method and device of the double-spherical center angle body 3D geometric structure of the present application realizes high-precision modeling of the dynamic shadow fading level distribution under the influence of time-varying communication angle based on the fitting method of mixed Gaussian distribution, and solves the problem of effective modeling and description of the evolution process of multipath effect during the satellite passing through the top through the multipath distribution description method of the spherical crown effective scattering area, thereby improving the accuracy of the description of the characteristics of the low-orbit satellite communication channel. In addition, when simulating the channel, the update frequency of the channel parameters is divided into three levels: fixed value, related interval update, and single sampling interval update. In this way, redundant parameter simulation can be effectively reduced and the hardware processing efficiency can be improved.

[0087] It should be understood by those skilled in the art that the exemplary components, systems and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software or a combination of the two. Whether it is performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, etc. When implemented in software, the elements of the present invention are programs or code segments used to perform the required tasks. The program or code segment can be stored in a machine-readable medium or transmitted on a transmission medium or a communication link via a data signal carried in a carrier. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, optical fiber media, radio frequency (RF) links, and the like. The code segment can be downloaded via a computer network such as the Internet, an intranet, etc.

[0088] It should also be noted that the exemplary embodiments mentioned in the present invention 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 steps, that is, the steps can be performed in the order mentioned in the embodiments, or in a different order from the embodiments, or several steps can be performed simultaneously.

[0089] In the present invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with features of other embodiments or replace features of other embodiments.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low-orbit satellite channel modeling method with a double-sphere center angle body 3D geometric structure, characterized in that: The method comprises: Acquire communication parameters and geometric parameters for constructing a double-sphere center angle body, wherein the geometric parameters include orbital altitude, earth radius, satellite position information, and receiving end position information, the communication parameters include communication frequency, transmission wavelength, and electromagnetic wave propagation speed, and the satellite position information includes initial access elevation angle, LOS path arrival elevation angle, and LOS path arrival azimuth angle; Constructing a free space loss model based on the geometric parameters and communication parameters; Acquire first measurement data of a low-orbit satellite during a process of passing overhead, the first measurement data including a satellite signal, determine a communication elevation angle range of a receiving end, divide the communication elevation angle range of the receiving end into intervals, and fit shadow fading of the low-orbit satellite in different intervals during the process of passing overhead into a dynamic shadow fading Gaussian mixture distribution model with time-varying parameters based on the first measurement data; Acquire second measurement data of the low-orbit satellite during the process of passing overhead, the second measurement data including the multipath arrival angle of the low-orbit satellite, fit the multipath arrival angle of the low-orbit satellite during the process of passing overhead into a Laplace distribution model with time-varying parameters based on the second measurement data, and determine a small-scale fading channel impulse response model based on the fitted Laplace distribution model; 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 expression of the dynamic shadow fading Gaussian mixture distribution model is: Where Δθ represents the angle interval, s f represents 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 represents the set of Gaussian distribution weights and Gaussian distribution parameters, represents the mean and variance parameter set of each independent Gaussian distribution process, p m Represents the probability of the Gaussian distribution corresponding to the mth interval; The expression of the Laplace distribution model with time-varying parameters is: in, and They represent the distribution range of the LOS path arrival azimuth angle and the distribution range of the LOS path arrival elevation angle, respectively. χ represents the mean square error of the angular power spectrum, β and β ′ are normalization factors, θ los (t) and They represent the time-varying LOS path arrival azimuth and LOS path arrival elevation respectively; The expression of the impulse response model of small-scale fading channel is: Among them, ssf los (t) represents the impulse response of the small-scale fading channel in the direct path, ssf nlos (t) represents the impulse response of the multipath small-scale fading channel, K(t) represents the time-varying Ricean factor, and f los represents the direct path Doppler shift, φ los (t) represents the time-varying receiving phase of the direct path, S represents the total number of multipath rays, represents the s-th multipath Doppler shift, represents the time-varying received phase of the s-th multipath.

2. The low-orbit satellite channel modeling method of the double-sphere center angle body 3D geometric structure according to claim 1 is characterized in that: The free space loss can be expressed as: Among them, f c represents the communication frequency, λ represents the transmission wavelength, c represents the electromagnetic wave propagation speed, d(t) represents the time-varying transmission distance between the satellite transmitter and the receiver, R E represents the radius of the earth, H represents the orbital altitude, represents the time-varying LOS path arrival elevation angle, θ los (t) represents the time-varying LOS path arrival azimuth.

3. The low-orbit satellite channel modeling method of the double-sphere center angle body 3D geometric structure according to claim 1 is characterized in that: Dividing the receiving end communication angle range into intervals includes: Determine the level value corresponding to each satellite signal; Determining the angle interval based on the numerical change of the level value; The receiving end communication angular range is divided into equally spaced intervals based on the angular interval.

4. The low-orbit satellite channel modeling method of the double-sphere center angle body 3D geometric structure according to claim 1 is characterized in that: The expression of the channel impulse response model of low-orbit satellite is: h(t)=p l (t)×s f (t)×s s (t); Where h(t) represents the channel impulse response of the low-orbit satellite, p l (t) represents free space loss, s f (t) represents shadow fading, s s (t) represents small-scale fading.

5. The low-orbit satellite channel modeling method of the double-sphere center angle body 3D geometric structure according to claim 1 is characterized in that: The method further comprises: constructing a double-spherical-center angle body 3D geometric model based on the geometric parameters, wherein a first spherical-center angle body has the center of the earth as a vertex, and a second spherical-center angle body has the receiving end as a vertex.

6. A low-orbit satellite channel modeling system with a dual-sphere center angle body 3D geometric structure, the system comprising a processor and a memory, characterized in that: The memory stores computer instructions, and the processor is used to execute the computer instructions stored in the memory. When the computer instructions are executed by the processor, the system implements the steps of the method as claimed in any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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