Channel modeling method and device suitable for satellite-ground communication

Abstract

The invention provides a channel modeling method and device suitable for satellite-ground communication, and the method comprises the steps: generating a satellite motion track, and setting ground environment parameters and simulation parameters; converting the satellite motion trail from a global coordinate system to a local coordinate system; acquiring a satellite position from the converted satellite motion trail, and performing ray tracing calculation based on plane wave hypothesis to obtain all effective ray paths between the satellite position and the position of a ground receiver; for each effective ray path, calculating large-scale fading caused by a meteorological environment and small-scale fading caused by ground end multipath propagation and multi-end movement; and a channel model is generated by combining large-scale fading and small-scale fading. According to the method, large-scale fading caused by the meteorological environment is modeled, the influence of meteorological attenuation on the multipath receiving power is considered, small-scale fading caused by multipath propagation and multi-end movement at the ground end is modeled, and the modeling accuracy is improved.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to a channel modeling method and device suitable for satellite-to-earth communication. Background Art

[0002] With the rapid development of communication applications, communication technology has undergone revolutionary changes. In order to meet technical and application requirements such as wider coverage, more connections, and ultra-high positioning accuracy, 6G wireless communication networks will adopt new paradigms and apply new technologies. The 6G vision can be summarized as "full coverage, full spectrum, full application, full sensory, full digital, and strong security". 6G will expand from local land coverage to global deep coverage on the basis of 5G. In order to build an integrated network of air, land, and sea and achieve global deep coverage, satellite communication is an indispensable part. For areas with high latitudes such as the polar regions that are difficult to cover by ground base stations, a communication network can be established through satellites to achieve true global coverage. At present, satellite communications have been widely used in navigation, broadcasting, earth observation and other fields due to its advantages such as wide coverage.

[0003] Channel characteristic analysis and modeling are the basis of system design, theoretical analysis, performance evaluation, optimization and deployment. In order to establish a stable and reliable satellite-to-ground communication system, it is necessary to accurately analyze the satellite-to-ground communication channel characteristics and establish an accurate satellite-to-ground communication channel model. At present, the existing technology has proposed a variety of channel models suitable for satellite communications. For example, the satellite-to-ground channel model based on geometric randomness introduces the concept of clusters to characterize the multipath effects generated by scatterers in the environment. It can be applied to different scenarios through parameter adjustment and has good versatility. However, it cannot accurately describe the propagation characteristics of electromagnetic waves in a specific environment, so it may not meet the high-precision requirements of 6G channels in specific fields. The channel modeling method based on ray tracing is based on geometrical optics (GO) and uniform diffraction theory (UTD), which can accurately describe the propagation characteristics of electromagnetic waves such as reflection and diffraction. By reconstructing the real scene, it can realize the simulation of specific scenes with high accuracy. Therefore, it is also widely used in satellite-to-ground communication channel modeling. However, this method does not fully consider the characteristics of the satellite-to-ground communication channel, resulting in a relatively low accuracy of the model. Summary of the invention

[0004] The present invention provides a channel modeling method and device suitable for satellite-to-ground communication, which is used to solve the problem of low model accuracy caused by the ray tracing algorithm in the prior art not fully considering the characteristics of the satellite-to-ground communication channel, and effectively model the satellite motion trajectory and improve the model accuracy. The technical solution proposed by the present invention is as follows: In a first aspect, the present invention provides a channel modeling method applicable to satellite-to-ground communication, comprising: Generate a satellite motion trajectory, and set ground environment parameters and simulation parameters; wherein the simulation parameters include the position of the ground receiver; According to ground environment parameters, the satellite motion trajectory is converted from the global coordinate system to the local coordinate system to obtain the converted satellite motion trajectory; The satellite position is obtained from the converted satellite motion trajectory, and ray tracing calculation is performed based on the plane wave assumption to obtain all valid ray paths between the satellite position and the position of the ground receiver; For each valid ray path, the large-scale fading caused by the meteorological environment is calculated; For each valid ray path, the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end is calculated; The channel model is generated by combining large-scale fading and small-scale fading.

[0005] Optionally, all the valid ray paths include line-of-sight paths and non-line-of-sight paths; The ray tracing calculation based on the plane wave assumption is performed to obtain all valid ray paths between the satellite position and the ground receiver position, including: Determine the virtual transmitting surface and the propagation direction of parallel rays according to the satellite position and the position of the ground receiver; Calculating a line-of-sight path from the satellite to a ground receiver based on the determined virtual transmitting surface and the parallel ray propagation direction; A visibility tree is established with the ground receiver as the root node, and the visibility tree is traversed to calculate the non-line-of-sight path.

[0006] Optionally, the visible tree includes a first visible tree and a second visible tree, and the non-line-of-sight path includes an effective reflection path and an effective diffraction path; The method of establishing a visible tree with the ground receiver as the root node and traversing the visible tree to calculate the non-line-of-sight path includes: According to the set maximum allowed reflection number of ray tracing, the first visible tree is established; Establishing a second visible tree according to the set maximum allowed diffraction number of ray tracing; An effective reflection path and an effective diffraction path are calculated according to the first visible tree and the second visible tree respectively; wherein the effective reflection path and the effective diffraction path satisfy: a starting point of the ray is within a virtual emission surface and a ray propagation direction is a ray propagation direction parallel to the ray propagation direction.

[0007] Optionally, the simulation parameters include simulation frequency; For each valid ray path, the large-scale fading caused by the meteorological environment is calculated, including: Considering the influence of the atmospheric environment, the atmospheric gas attenuation corresponding to each effective ray path is calculated; Considering the influence of rainfall, the rainfall attenuation corresponding to each valid ray path is calculated; Considering the influence of tropospheric scintillation, the tropospheric scintillation attenuation corresponding to each effective ray path is calculated; Considering the influence of ionospheric scintillation, the ionospheric scintillation fading corresponding to each effective ray path is calculated; The total attenuation caused by the meteorological environment is calculated according to the atmospheric gas attenuation, rainfall attenuation, tropospheric scintillation attenuation, ionospheric scintillation attenuation and simulation frequency to obtain the large-scale fading.

[0008] Optionally, the small-scale fading of the effective ray path is characterized by received power, Doppler shift and delay; For each valid ray path, the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end is calculated, including: Calculating the power generated by the effective ray path at the receiving end, and calculating the receiving power of each effective ray path according to the power generated by the effective ray path at the receiving end and the large-scale fading; Calculate the Doppler shift for each valid ray path; Compute the delay for each valid ray path.

[0009] Optionally, the generating a channel model by combining large-scale fading and small-scale fading includes: A channel impulse response is generated according to the received power, Doppler frequency shift and time delay of each effective ray path to obtain the channel model.

[0010] In a second aspect, the present invention provides a channel modeling device suitable for satellite-to-earth communication, comprising: A trajectory generation module is used to generate a satellite motion trajectory and set ground environment parameters and simulation parameters; wherein the simulation parameters include the position of the ground receiver; A coordinate conversion module, used to convert the satellite motion trajectory from a global coordinate system to a local coordinate system according to ground environment parameters, to obtain a converted satellite motion trajectory; A ray tracing module is used to obtain the satellite position from the converted satellite motion trajectory, perform ray tracing calculations based on the plane wave assumption, and obtain all valid ray paths between the satellite position and the position of the ground receiver; A first calculation module is used to calculate the large-scale fading caused by the meteorological environment for each valid ray path; The second calculation module is used to calculate the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end for each effective ray path; The model generation module is used to generate a channel model by combining large-scale fading and small-scale fading.

[0011] In a third aspect, the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the channel modeling method applicable to satellite-to-earth communication as described in the first aspect is implemented.

[0012] In a fourth aspect, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the channel modeling method applicable to satellite-to-earth communication as described in the first aspect is implemented.

[0013] In a fifth aspect, the present invention provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the channel modeling method applicable to satellite-to-earth communication as described in the first aspect is implemented.

[0014] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows: The channel modeling method suitable for satellite-to-ground communication provided by the present invention models the real satellite motion trajectory and ground environment, models the large-scale fading caused by the meteorological environment by converting the satellite trajectory to a local coordinate system and realizing ray tracing calculation based on the plane wave assumption, considers the influence of meteorological attenuation on multipath received power, and models the small-scale fading caused by multipath propagation and multi-terminal movement on the ground side, comprehensively considers multiple factors such as the satellite motion trajectory, meteorological environment, near-ground environment and multi-terminal movement, so that the model can more realistically reflect the complex situation in the channel, thereby improving the accuracy of modeling.

[0015] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0016] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a flow chart of a channel modeling method applicable to satellite-to-earth communication provided by the present invention.

[0019] Figure 2 It is a schematic diagram of the satellite motion trajectory in the global coordinate system provided by the present invention.

[0020] Figure 3 It is a schematic diagram of effective ray path propagation at the near-ground end of satellite-to-ground communication provided by the present invention.

[0021] Figure 4 It is a structural schematic diagram of a channel modeling device suitable for satellite-to-earth communication provided by the present invention.

[0022] Figure 5 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Satellites can be divided into low earth orbit (LEO) satellites, medium earth orbit (MEO) satellites and geostationary earth orbit (GEO) satellites according to their orbital altitude. Among them, low earth orbit satellites have an altitude range of about 500-2000 km, with relatively low transmission delay and power consumption, and are mostly used for earth observation, space stations, etc. MEO has an altitude range of 2000-35786 km and is widely used by navigation satellites. GEO is located in a circular orbit at an altitude of 35786 km, with a larger coverage area, and meteorological satellites are usually GEO satellites. Common frequency bands for satellite communications include Ku (12-18 GHz), K (18-26.5 GHz), Ka (26.5-40 GHz) and V (40-75 GHz).

[0025] In satellite communications, wireless signals transmitted to the ground will pass through the ionosphere and troposphere. The ionospheric effect has a significant impact on the propagation of electromagnetic waves below 10GHz. For the troposphere, the communication channel is greatly affected by weather changes such as clouds, rain, and fog. Therefore, the impact of the meteorological environment needs to be considered when modeling satellite communication channels. In addition, buildings near the ground receiver may block the communication signal, and multipath propagation needs to be considered. As the satellite moves, the satellite elevation angle will continue to change, and the multipath near the receiver will change dynamically. The high-speed movement of the satellite will cause large Doppler shift and Doppler shift changes, which will seriously reduce the performance of the system. Channel characteristic analysis and modeling are the basis of system design, theoretical analysis, performance evaluation, optimization and deployment. In order to establish a stable and reliable satellite-to-ground communication system, it is necessary to accurately analyze the characteristics of the satellite-to-ground communication channel and establish an accurate satellite-to-ground communication channel model.

[0026] The present invention provides a channel modeling method and device suitable for satellite-to-ground communication, which can effectively model the satellite motion trajectory, comprehensively consider the characteristics of the satellite-to-ground communication channel, and support satellite-to-ground multi-terminal mobile communication scenarios.

[0027] Combine the following Figure 1-Figure 5 A channel modeling method and device suitable for satellite-to-ground communication according to the present invention are described.

[0028] Figure 1 is a flow chart of a channel modeling method applicable to satellite-to-ground communication provided by the present invention, such as Figure 1 As shown, the method includes the following: Step S101: Generate a satellite motion trajectory, and set ground environment parameters and simulation parameters.

[0029] Based on the satellite's orbital parameters (including one or more of the semi-major axis, eccentricity, inclination, right ascension of the ascending node, etc.), the three-dimensional spatial position of the satellite within a given time range is calculated using the principles of celestial mechanics. These position data are usually stored in the form of a time series, representing the coordinates of the satellite at different time points. Generate satellite parameters, including the global coordinates of the satellite at different times, the instantaneous motion speed of the satellite at different times, the sampling time interval, the satellite transmission power, and the satellite antenna type.

[0030] Set the near-ground environmental parameters, including the global coordinates and local coordinates of the ground reference point, the three-dimensional vertex coordinates of the building in the local coordinate system, and the material electromagnetic parameters of the building. The material electromagnetic parameters include one or more of dielectric constant, conductivity, roughness and thickness.

[0031] The simulation parameters are set specifically including the simulation frequency, the motion trajectory or position coordinates of the ground receiver, the antenna type of the ground receiver, and the maximum allowed number of reflections, diffractions, and transmissions for ray tracing.

[0032] Set meteorological environment parameters and choose whether to consider ionospheric effect or tropospheric effect according to the simulation frequency. Tropospheric effect includes atmospheric attenuation, rainfall attenuation, and tropospheric scintillation. If ionospheric scintillation is considered, set the scintillation index. If rainfall attenuation is considered, set the rainfall intensity, annual rainfall exceedance probability, terrain height above the mean sea level, and annual average rainfall height above the mean sea level. If tropospheric scintillation is considered, set one or more of the following parameters: antenna energy efficiency, maximum aperture of ground-end antenna, and radio refractive index wet term parameter.

[0033] According to the satellite's orbit and the location of the ground station, the satellite-to-ground communication environment is deployed, including the ground station's antenna direction, height, gain and other parameters. At the same time, the impact of environmental factors such as terrain, buildings, and vegetation on signal propagation also needs to be considered.

[0034] Step S102: According to ground environment parameters, the satellite motion trajectory is converted from the global coordinate system to the local coordinate system to obtain the converted satellite motion trajectory.

[0035] The satellite motion trajectory is converted from the global coordinate system (such as the geocentric inertial coordinate system) to the local coordinate system (such as the coordinate system centered on the ground receiver). The conversion can simplify the ray tracing calculation process and make the relative position relationship between the starting point of the ray tracing, i.e. the satellite position, and the end point, i.e. the ground receiver position, more intuitive.

[0036] Step S103: Acquire the satellite position from the converted satellite motion trajectory, perform ray tracing calculation based on the plane wave assumption, and obtain all valid ray paths between the satellite position and the position of the ground receiver.

[0037] In the ray tracing process, it is usually assumed that the signal transmitted by the satellite is a plane wave, that is, the wave front is a plane. Based on the plane wave assumption, the satellite position at each time point in the converted satellite motion trajectory is selected as the transmitting point, and the ground receiver position is selected as the receiving point for ray tracing. The ray tracing algorithm takes into account factors such as the atmosphere and topography to simulate the propagation path of electromagnetic waves from the satellite to the ground receiver. Through ray tracing, all possible paths that reach the ground receiver after reflection and diffraction through the ground environment (such as one or more of the ground, buildings, trees, etc.) can be identified, including reflection paths, diffraction paths, etc., and the above-mentioned effective ray paths, i.e., multipaths, are combined.

[0038] Step S104: For each valid ray path, calculate the large-scale fading caused by the meteorological environment.

[0039] Considering the impact of meteorological conditions on signal propagation, these meteorological conditions will cause the attenuation of signal energy. The above-mentioned large-scale fading refers to the large-scale fading caused by one or more phenomena in the meteorological environment, such as rainfall attenuation, cloud and fog absorption, etc. For each valid ray path, the signal attenuation caused by the meteorological environment is calculated based on the meteorological environment parameters and the geometric characteristics of the signal propagation path (including one or more parameters such as path length and propagation angle).

[0040] Step S105: For each effective ray path, small-scale fading caused by multipath propagation and multi-terminal movement at the ground end is calculated.

[0041] Consider the multipath propagation effect around the ground receiver and possible receiver movement. Multipath propagation will cause delay spread and frequency selective fading of the signal, while the movement of the receiver may introduce Doppler frequency shift. The above-mentioned small-scale fading refers to the small-scale fading caused mainly by multipath propagation and multi-end movement near the ground, such as reflection and diffraction of different scatterers leading to coherent superposition of multipaths with different delays at the receiving end, dynamic changes of mobile receivers, etc. For each effective ray path, considering the complexity of the near-ground environment, combined with the ground environment, and the moving speed and direction of the receiver, the signal fluctuations and fading caused by multipath propagation and mobility are calculated by electromagnetic simulation methods.

[0042] Step S106: Generate a channel model by combining large-scale fading and small-scale fading.

[0043] The present invention models the real satellite motion trajectory and ground environment, and models the large-scale fading caused by the meteorological environment by converting the satellite trajectory to the local coordinate system and realizing ray tracing calculation based on the plane wave assumption. The influence of meteorological attenuation on multipath receiving power is considered, and the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end is modeled. By comprehensively considering multiple factors such as satellite motion trajectory, meteorological environment, near-ground environment and multi-terminal movement, the model can more realistically reflect the complex situation in the channel, such as atmospheric attenuation, multipath effect, Doppler frequency shift, etc., thereby improving the accuracy of the channel model.

[0044] This method supports a variety of application scenarios, such as satellites at different orbital altitudes, ground receivers at different geographical locations, and complex and changeable meteorological conditions. By adjusting the model parameters, it can flexibly adapt to different communication environments and requirements, providing strong support for the design of satellite-to-ground communication systems in different application scenarios. The performance of satellite-to-ground communication systems can be predicted and analyzed through accurate channel models, including key indicators such as signal attenuation. This helps provide a reference for performance optimization in the design phase of the communication system, thereby improving the overall performance and reliability of the system.

[0045] The above-mentioned step S102 converts the satellite motion trajectory from the global coordinate system to the local coordinate system according to the ground environment parameters to obtain the converted satellite motion trajectory, which specifically includes the following steps: S201, transform the satellite trajectory from the global coordinate system (such as Figure 2 Taking the latitude and longitude high coordinate system as an example, the satellite's motion trajectory can be converted from the latitude and longitude high coordinate system to the Earth-Centered Earth-Fixed (ECEF) coordinate system:

[0046] in,( , , ) is the satellite coordinate after the initial conversion, is the latitude (in degrees), is the longitude (unit: °), h is the altitude (unit: m), e is the eccentricity of the ellipsoid, R N is the radius of curvature of the angular circle of the reference ellipsoid, and a is the major semi-axis of the Earth ellipsoid. Figure 2 R E is the radius of the earth, and d is the distance from the satellite to the ground receiving point.

[0047] S202. Convert the satellite motion trajectory from the ECEF coordinate system to the East-North-Up (ENU) coordinate system:

[0048] in, is the satellite coordinate after secondary transformation, is the latitude of the ground reference point (in degrees), is the longitude of the ground reference point (in degrees), is the ECEF coordinate of the ground reference point.

[0049] In an optional embodiment, all the valid ray paths in the above step S103 include line-of-sight paths and non-line-of-sight paths; The ray tracing calculation based on the plane wave assumption described in step S103 above to obtain all valid ray paths between the satellite position and the ground receiver position specifically includes: S301. Determine a virtual transmitting surface and a parallel ray propagation direction according to a satellite position and a ground receiver position.

[0050] In order to simplify the starting conditions of ray tracing, the present invention defines a virtual emission surface at the satellite position. The position and shape of this surface can be determined in three-dimensional space according to the current position of the satellite, the current position of the ground receiver and the parameters of the set virtual emission surface. Specifically, the height h of the virtual emission surface is determined according to the satellite position and the position of the ground receiver. vir , radius size r vir , virtual launch surface center position p vir The virtual transmitting surface is a circular surface with a normal vector passing through the center and a radius of r, and the transmitting ray propagation direction is ,in, is the current position of the satellite, The current position of the ground receiver. The height h of the above virtual transmitting surface vir , users can set it according to actual needs.

[0051] S302: Calculate the line-of-sight path from the satellite to the ground receiver according to the determined virtual transmitting surface and the parallel ray propagation direction.

[0052] The line-of-sight path is the most direct propagation path between the satellite and the ground receiver without any reflection or diffraction. After determining the position of the virtual transmitting surface and the ground receiver, the straight-line distance and direction between the two can be directly calculated as the line-of-sight path. Specifically, the center of the circle connecting the ground receiver and the virtual transmitting surface, if the path is not blocked by other buildings in the environment, it means that there is a line-of-sight path between the satellite and the ground receiver and the path is recorded, otherwise the line-of-sight path is invalid.

[0053] S303: Establish a visible tree with the ground receiver as the root node, and traverse the visible tree to calculate the non-line-of-sight path.

[0054] The non-line-of-sight paths mentioned above include all paths that are reflected, transmitted or diffracted. In order to effectively find these paths, the present invention establishes a visible tree to simulate the propagation process of electromagnetic waves in the environment.

[0055] First, establish a visibility tree: Take the ground receiver as the root node and start to build a visibility tree. Each node of the visibility tree represents a possible reflection point or diffraction point (such as the ground, buildings, mountains, etc.). Determine which nodes are visible based on the ground environment data, that is, the electromagnetic wave can be transmitted from the satellite to the node, and from the node can be further transmitted to the ground receiver.

[0056] Second, traverse the visibility tree: Starting from the root node, traverse each branch of the visibility tree. For each branch, calculate the path from the satellite to the current node, and then from the current node to the ground receiver. It is necessary to consider multiple reflections or diffractions, evaluate the feasibility of each path, and retain all valid non-line-of-sight paths.

[0057] The present invention can more accurately simulate the characteristics of satellite-to-ground communication channels by calculating line-of-sight paths and non-line-of-sight paths respectively, and taking into account multiple factors such as ground environment and meteorological conditions, thereby improving the accuracy of the channel model. The establishment of a visible tree enables the model to handle complex ground environments, which helps to evaluate the performance of satellite-to-ground communication systems under different environments. Based on this, an accurate channel model can be established to predict and analyze signal coverage and signal quality under different satellite orbits and different ground receiver locations.

[0058] The ray tracing channel modeling method based on SBR, because the rays are emitted in the form of point sources at the transmitting end, as the propagation distance increases, the distance between adjacent rays increases. For communication scenarios with long propagation distances such as satellite-to-ground, effective multipath information cannot be received at the receiving end, which affects the accuracy of the model. Although the optimized SBR algorithm solves the above problems of the traditional SBR algorithm based on the parallel wave assumption, it requires a receiving sphere to make a reception judgment, and the reception judgment method for the parallel wave assumption is unclear. The accuracy of the model is greatly affected by the size of the receiving sphere. The existing ray tracing channel modeling method based on the mirror method does not support parallel wave propagation, and due to the long propagation distance between the transmitter and receiver in the satellite-to-ground scenario, the complexity is high.

[0059] The present invention establishes a virtual transmission plane and determines the initial ray propagation direction through the position of the transceiver, and ensures that all valid ray paths meet the parallel wave propagation assumption by establishing a reverse visible tree and determining the initial ray propagation direction. Moreover, by establishing a visible tree, on the one hand, unnecessary intersection judgments in the ray tracing process are reduced, reducing complexity, and on the other hand, the propagation path determined by the visible tree can accurately reach the receiving end, solving the problem of being unable to receive effective multipaths, and avoiding the problem of low model accuracy caused by unreasonable setting of the receiving sphere size.

[0060] In an optional embodiment, the step S303 described above, establishing a visibility tree with the ground receiver as the root node, and traversing the visibility tree to calculate the non-line-of-sight path, specifically includes: S1031. Set the maximum allowed number of reflections and diffractions for ray tracing. These parameters determine the complexity and accuracy of ray tracing. Load the environment model, including obstacles such as terrain, buildings, and vegetation that may affect ray propagation. By limiting the maximum number of reflections and diffractions, it is possible to reduce unnecessary calculations while ensuring a certain accuracy, thereby improving the calculation efficiency of ray tracing.

[0061] According to the set maximum allowed reflection number n of ray tracing, an n+1 level visible tree (hereinafter referred to as the first visible tree) is established. With the ground receiver as the root node, the potential reflection surfaces in the environment (such as the ground, building walls, etc.) are traversed. For each reflection surface, the possible reflection paths are recursively calculated according to the reflection law and the maximum allowed reflection number of ray tracing.

[0062] Specifically, taking the ground receiver as the initial virtual source, the visible surfaces about the ground receiver are calculated, the visible surfaces are set as child nodes of the virtual source, the mirror points of the receiver about these visible surfaces are calculated, and these mirror points are regarded as secondary virtual sources, and the visible surfaces about these secondary virtual sources are found, and so on, until the maximum allowed number of reflections is reached.

[0063] S1032. According to the set maximum allowable diffraction number m of ray tracing, an m+1 level visible tree (hereinafter referred to as the second visible tree) is established. The ground receiver is also used as the root node, and diffraction phenomena are considered, such as electromagnetic waves continuing to propagate around the edge of obstacles. The possible diffraction paths are calculated using diffraction theory (such as geometric diffraction theory GTD or consistent diffraction theory UTD) and the set maximum allowable diffraction number.

[0064] Specifically, the ground receiver is used as the initial virtual source, the visible wedge about the receiver is calculated, and added to the child node of the current visible tree, the two endpoints of the visible wedge are used as virtual sources, the union of the visible wedges of the two endpoints is taken as the next level visible wedge of the current visible wedge, and added to the corresponding child node, and so on until the maximum allowed diffraction number is reached. The above visible wedge refers to the wedge that is reachable by the ray path for the receiver.

[0065] S1033. Calculate the effective reflection path and the effective diffraction path according to the first visible tree and the second visible tree, respectively. Traverse the first visible tree and the second visible tree, and extract the effective reflection path and the effective diffraction path, respectively. Verify whether these paths meet the conditions: the starting point of the ray is within the virtual emission surface, the parallel ray propagation direction is the ray propagation direction, and it is not blocked by any obstacles such as buildings during the entire propagation process. Record the effective reflection path and diffraction path obtained by ray tracing, specifically including the position coordinate information of all interaction points contained in the path and the information of the surface or split where the interaction points are located.

[0066] By constructing a visible tree and calculating the effective reflection path and the effective diffraction path respectively, the present invention can more accurately simulate the propagation process of electromagnetic waves in a complex environment, thereby improving the accuracy and reliability of the simulation. The calculation results of the non-line-of-sight path are helpful for analyzing the impact of multipath effects on signal propagation, and provide strong support for signal processing and interference suppression. The method can handle scenes containing multiple obstacles and complex terrains, and is suitable for ray tracing simulation in various environments such as cities and mountainous areas.

[0067] In an optional embodiment, the simulation parameters include simulation frequency; The above step S104 calculates the large-scale fading caused by the meteorological environment for each valid ray path, specifically including: S401. Gases in the atmosphere, such as oxygen and water vapor, have a certain absorption effect on electromagnetic waves. By considering parameters such as atmospheric composition, temperature, and pressure, the attenuation of electromagnetic waves caused by atmospheric gas absorption during propagation can be calculated. The present invention considers the influence of the atmospheric environment and calculates the atmospheric gas attenuation corresponding to each effective ray path. , for example, the atmospheric gas attenuation corresponding to each effective ray path can be calculated according to ITU-R P.618 :

[0068] in, is the elevation angle corresponding to the path obtained by ray tracing, f represents the operating frequency, that is, the carrier frequency of the transmitter, A zenith (f) is the zenith attenuation, which can be obtained by looking up ITU-R P.618.

[0069] S402. Rainfall is a common meteorological phenomenon in satellite communications and has a significant impact on electromagnetic wave propagation. The present invention takes the impact of rainfall into consideration and calculates the rainfall attenuation corresponding to each effective ray path. For example, the rainfall attenuation can be calculated according to the rainfall attenuation model proposed in ITU-R P.838. :

[0070] Among them, the parameters and Both are related to the operating frequency , the pitch angle corresponding to the path The rainfall attenuation coefficient related to the polarization tilt angle can be obtained by looking up ITU-R P.838. is the equivalent path length experienced by the rainfall area, .

[0071] S403. Turbulence and temperature gradient changes in the troposphere can cause random changes in the propagation path of electromagnetic waves, thereby generating scintillation. This scintillation phenomenon can cause rapid fluctuations in signal strength, affecting communication quality. The present invention considers the impact of tropospheric scintillation and calculates the tropospheric scintillation attenuation corresponding to each effective ray path. For example, the tropospheric scintillation attenuation can be calculated using the following formula: :

[0072] Where p is the time percentage, is the standard deviation of the reference signal amplitude, is the average antenna coefficient. For related parameters, please refer to ITU-R P.618.

[0073] Calculating atmospheric gas attenuation helps evaluate the performance of high-band satellite communication systems. By calculating rainfall attenuation, the performance of the system in areas with frequent rainfall can be predicted and evaluated, and appropriate measures can be taken, such as increasing the transmission power, using more efficient coding and modulation methods, or one or more measures to mitigate the impact of rainfall.

[0074] The present invention calculates tropospheric scintillation attenuation to help evaluate the performance stability of satellite communication systems under complex meteorological conditions. By understanding the characteristics of scintillation attenuation, appropriate signal processing technology can be used to reduce the impact of scintillation on communication quality.

[0075] S404. The inhomogeneity of the ionosphere structure leads to ionosphere scintillation, which causes changes in the amplitude and phase of the signal. This scintillation phenomenon has a particularly significant impact on satellite communication systems with frequencies below 3 GHz. The present invention takes into account the impact of ionosphere scintillation and calculates the ionosphere scintillation fading corresponding to each effective ray path. :

[0076] Where S is the flicker index.

[0077] By calculating the ionospheric scintillation fading, we can understand the characteristics of ionospheric scintillation, so as to select the appropriate communication frequency band, polarization mode and modulation mode to reduce the impact of ionospheric scintillation on communication quality, which is of great significance for the design and optimization of satellite communication systems.

[0078] S405. Calculate the total attenuation caused by the meteorological environment based on the simulation frequency and meteorological parameters. The tropospheric effect has a more obvious impact on electromagnetic waves above 10 GHz, including atmospheric attenuation caused by clear air gas absorption, scintillation caused by atmospheric turbulence structure, and attenuation of electromagnetic waves caused by hydrometeors in the troposphere. The ionospheric effect has a more obvious impact on the propagation of electromagnetic waves below 10 GHz, and the impact on frequencies below 3 GHz is particularly significant. The total attenuation caused by the meteorological environment is also the above-mentioned large-scale fading. It can be calculated as

[0079] in, represents the total meteorological attenuation corresponding to the i-th path, represents the attenuation due to atmospheric gases, represents the rainfall attenuation, represents the tropospheric scintillation attenuation, Indicates ionospheric scintillation attenuation.

[0080] The present invention comprehensively considers atmospheric gas attenuation, rainfall attenuation, tropospheric scintillation attenuation and ionospheric scintillation attenuation, and can comprehensively evaluate the impact of the meteorological environment on the performance of the satellite communication system. This detailed fading calculation not only improves the accuracy and reliability of the channel model, but also provides important data support for system design and optimization. By understanding the fading characteristics under different meteorological conditions, effective countermeasures can be formulated to improve the reliability and stability of the satellite communication system and meet the communication needs in various complex environments.

[0081] In an alternative embodiment, referring to Figure 3 The diagram is a schematic diagram of effective ray path propagation near the ground end of satellite-to-ground communication. The small-scale fading parameters of the effective ray path are characterized by received power, Doppler frequency shift and delay; the small-scale fading caused by multipath propagation and multi-end movement at the ground end is calculated for each effective ray path as described in the above step S105, including: S501. Consider the multipath propagation at the ground end, that is, the signal may reach the receiving end through multiple paths such as direct, reflected, diffracted, and transmitted. These paths have different lengths and attenuations, which will cause changes in amplitude and phase when the signal is superimposed at the receiving end. The influence of meteorological attenuation (that is, the above-mentioned large-scale fading) on ​​the receiving power of the effective ray path is also considered. The present invention first calculates the power generated by the effective ray path at the receiving end, and then calculates the receiving power of each effective ray path based on the power generated by the effective ray path at the receiving end and the large-scale fading. :

[0082] in, is the power generated by the i-th effective ray path at the receiving end, is the electric field strength generated by the i-th effective ray path at the receiving end, is the gain of the receiving antenna, is the wavelength, is the impedance of free space.

[0083] Take an effective ray path that undergoes M reflections, N diffractions, and J transmissions as an example. Its electric field is It can be calculated by the following formula:

[0084] in, is the incident electric field, R is the reflection coefficient, D is the diffraction coefficient, T is the transmission coefficient, , , are the amplitude diffusion factors of the reflected wave, diffracted wave and transmitted wave respectively, k is the wave number, and r is the total path length.

[0085] S502, calculate the Doppler frequency shift of each effective ray path :

[0086] Where c is the propagation speed of electromagnetic waves in free space, is the satellite's speed, The speed of the receiver, is the moving speed of the object interacting with the ray, is the unit direction vector between two action points on the ray path, Represents the unit direction vector from the transmitter to the first action point, Represents the unit direction vector from the last action point to the receiving end.

[0087] S503, calculating the delay of each valid ray path ,in, is the total length of the i-th effective ray path, which is the sum of the distance from the satellite to the center of the virtual transmitting surface and the propagation path length calculated by ray tracing from the virtual transmitting surface to the receiver.

[0088] The present invention can more accurately simulate the signal propagation characteristics in the actual communication environment by considering the large-scale fading caused by the meteorological environment and the small-scale fading such as Doppler frequency shift caused by the multipath effect. By modeling the multipath propagation caused by the ground-end buildings and the Doppler frequency shift caused by the movement of the transceiver, it can help communication system designers better understand the fluctuation of the signal at the receiving end, including the fluctuation of power, the frequency offset and the change of delay. In the mobile communication system, the movement of the receiving end will cause the dynamic change of the signal propagation characteristics. By calculating the Doppler frequency shift and delay of each effective ray path, these changes can be tracked in real time, and the system parameters can be adjusted accordingly or corresponding compensation measures can be adopted to enhance the adaptability of the system to the dynamic environment.

[0089] In an optional embodiment, the multipath propagation phenomenon of the signal at the ground end is considered. Since the signal may reach the receiving end through multiple paths, these paths have different lengths and attenuations, which will cause the signal to produce changes in amplitude and phase when superimposed at the receiving end. If the receiving end (or transmitting end) is in a mobile state, the influence of the Doppler effect on the signal frequency must also be considered. The Doppler effect will cause the signal frequency to shift. Therefore, the present invention combines the large-scale fading caused by the meteorological environment, and the small-scale fading caused by multipath propagation near the ground and multi-terminal movement to establish a channel model. The generation of a channel model by combining large-scale fading and small-scale fading as described in the above step S106 specifically includes: Based on the received power of each valid ray path , Doppler shift and delay , generate a channel impulse response, and obtain the channel model. Channel impulse response The calculation formula is:

[0090] in, For time, is the amplitude of the i-th effective ray path, which can be obtained by After normalization, we get The phase of the i-th effective ray path includes the initial phase and the phase change caused by time delay and Doppler frequency shift. The number of valid ray paths computed for ray tracing, Impulse function. The calculation method of the phase change caused by the time delay and Doppler frequency shift can refer to the description in the prior art, and the phase change caused by the time delay For example:

[0091] The present invention is based on the received power The amplitude response is calculated, taking into account the phase changes caused by Doppler shift and delay. The above channel impulse response is obtained by superimposing the channel impulse responses of all valid ray paths: Specifically, the large-scale fading caused by the meteorological environment Mainly affects the overall power level of the signal. The present invention applies large-scale fading before generating the channel impulse response. To adjust the power of the receiving end to get the received power That is, the large-scale fading Implicit in the received power The channel impulse response is Magnitude through the effective ray path , Phase and delay Generate, where the amplitude By the above receiving power Normalized to get the phase It includes the initial phase and the phase change caused by time delay and Doppler frequency shift (i.e., small-scale fading parameters). That is, the channel model of the present invention combines the large-scale fading caused by the meteorological environment with the small-scale fading caused by multipath propagation near the ground and multi-terminal movement.

[0092] The ray tracing channel modeling method suitable for satellite-to-ground communication scenarios provided by the present invention models the actual satellite motion trajectory and ground environment. By converting the satellite trajectory into a local coordinate system and realizing ray tracing calculation based on the plane wave assumption, it models large-scale fading such as rainfall attenuation and ionospheric / tropospheric scintillation, considers the influence of meteorological attenuation on the received power of the effective ray path, and models the multipath propagation caused by ground-end buildings and the Doppler frequency shift caused by the movement of the transceiver and other effects, with high accuracy.

[0093] The channel model combines large-scale fading caused by the meteorological environment and small-scale fading caused by near-ground multipath propagation and multi-terminal movement, which enables the model to more comprehensively reflect the complex situation in the actual communication environment. By modeling the deployment of the real ground-end environment and the multi-terminal movement trajectories of satellites and ground receivers, the propagation characteristics of electromagnetic waves such as reflection and diffraction, and the influence of multi-spectrum frequency shift caused by multi-terminal movement, the accuracy of the channel model is improved. An accurate channel model helps the communication system to more accurately predict and respond to interference and fading in the channel, thereby improving the transmission efficiency and reliability of the system.

[0094] The channel modeling device applicable to satellite-to-ground communication provided by the present invention is described below. The channel modeling device applicable to satellite-to-ground communication described below and the channel modeling method applicable to satellite-to-ground communication described above can correspond to each other.

[0095] Reference Figure 4 As shown, the device comprises: The trajectory generation module 601 is used to generate the satellite motion trajectory and set the ground environment parameters and simulation parameters; wherein the simulation parameters include the position of the ground receiver; A coordinate conversion module 602 is used to convert the satellite motion trajectory from a global coordinate system to a local coordinate system according to ground environment parameters to obtain a converted satellite motion trajectory; A ray tracing module 603 is used to obtain the satellite position from the converted satellite motion trajectory, perform ray tracing calculation based on the plane wave assumption, and obtain all valid ray paths between the satellite position and the position of the ground receiver; A first calculation module 604 is used to calculate the large-scale fading caused by the meteorological environment for each valid ray path; The second calculation module 605 is used to calculate the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end for each effective ray path; The model generation module 606 is used to generate a channel model by combining large-scale fading and small-scale fading.

[0096] Figure 5 An example of a physical structure diagram of an electronic device is shown in FIG. Figure 5As shown, the electronic device may include: a processor (Processor) 710, a communication interface (Communications Interface) 720, a memory (memory) 730 and a communication bus 740, wherein the processor 710, the communication interface 720, and the memory 730 communicate with each other through the communication bus 740. The processor 710 may call the logic instructions in the memory 730 to execute the channel modeling method applicable to satellite-to-ground communication.

[0097] In addition, the logic instructions in the above-mentioned memory 730 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0098] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the channel modeling method suitable for satellite-to-earth communication provided by the above methods.

[0099] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the computer program is executed by a processor to execute the channel modeling method applicable to satellite-to-earth communication provided by the above methods.

[0100] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0101] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A channel modeling method suitable for satellite-to-ground communication, characterized in that: include: Generate a satellite motion trajectory, and set ground environment parameters and simulation parameters; wherein the simulation parameters include the position of the ground receiver; According to ground environment parameters, the satellite motion trajectory is converted from the global coordinate system to the local coordinate system to obtain the converted satellite motion trajectory; The satellite position is obtained from the converted satellite motion trajectory, and ray tracing calculation is performed based on the plane wave assumption to obtain all valid ray paths between the satellite position and the position of the ground receiver; For each valid ray path, the large-scale fading caused by the meteorological environment is calculated; For each valid ray path, the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end is calculated; The channel model is generated by combining large-scale fading and small-scale fading.

2. The channel modeling method applicable to satellite-to-ground communication according to claim 1, characterized in that: All valid ray paths include line-of-sight paths and non-line-of-sight paths; The ray tracing calculation based on the plane wave assumption is performed to obtain all valid ray paths between the satellite position and the ground receiver position, including: Determine the virtual transmitting surface and the propagation direction of parallel rays according to the satellite position and the position of the ground receiver; Calculating a line-of-sight path from the satellite to a ground receiver based on the determined virtual transmitting surface and the parallel ray propagation direction; A visibility tree is established with the ground receiver as the root node, and the visibility tree is traversed to calculate the non-line-of-sight path.

3. The channel modeling method applicable to satellite-to-ground communication according to claim 2, characterized in that: The visible tree includes a first visible tree and a second visible tree, and the non-line-of-sight path includes an effective reflection path and an effective diffraction path; The method of establishing a visible tree with the ground receiver as the root node and traversing the visible tree to calculate the non-line-of-sight path includes: According to the set maximum allowed reflection number of ray tracing, the first visible tree is established; Establishing a second visible tree according to the set maximum allowed diffraction number of ray tracing; An effective reflection path and an effective diffraction path are calculated according to the first visible tree and the second visible tree respectively; wherein the effective reflection path and the effective diffraction path satisfy: a starting point of the ray is within a virtual emission surface and a ray propagation direction is a ray propagation direction parallel to the ray propagation direction.

4. The channel modeling method applicable to satellite-to-ground communication according to claim 1, characterized in that: The simulation parameters include simulation frequency; For each valid ray path, the large-scale fading caused by the meteorological environment is calculated, including: Considering the influence of the atmospheric environment, the atmospheric gas attenuation corresponding to each effective ray path is calculated; Considering the influence of rainfall, the rainfall attenuation corresponding to each valid ray path is calculated; Considering the influence of tropospheric scintillation, the tropospheric scintillation attenuation corresponding to each effective ray path is calculated; Considering the influence of ionospheric scintillation, the ionospheric scintillation fading corresponding to each effective ray path is calculated; The total attenuation caused by the meteorological environment is calculated according to the atmospheric gas attenuation, rainfall attenuation, tropospheric scintillation attenuation, ionospheric scintillation attenuation and simulation frequency to obtain the large-scale fading.

5. The channel modeling method applicable to satellite-to-ground communication according to claim 1, characterized in that: Small-scale fading of effective ray paths is characterized by received power, Doppler shift, and time delay; For each valid ray path, the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end is calculated, including: Calculating the power generated by the effective ray path at the receiving end, and calculating the receiving power of each effective ray path according to the power generated by the effective ray path at the receiving end and the large-scale fading; Calculate the Doppler shift for each valid ray path; Compute the delay for each valid ray path.

6. The channel modeling method applicable to satellite-to-ground communication according to claim 5, characterized in that: The generating of the channel model by combining large-scale fading and small-scale fading comprises: A channel impulse response is generated according to the received power, Doppler frequency shift and time delay of each effective ray path to obtain the channel model.

7. A channel modeling device suitable for satellite-to-ground communication, characterized in that: include: A trajectory generation module is used to generate a satellite motion trajectory and set ground environment parameters and simulation parameters; wherein the simulation parameters include the position of the ground receiver; A coordinate conversion module, used to convert the satellite motion trajectory from a global coordinate system to a local coordinate system according to ground environment parameters, to obtain a converted satellite motion trajectory; A ray tracing module is used to obtain the satellite position from the converted satellite motion trajectory, perform ray tracing calculations based on the plane wave assumption, and obtain all valid ray paths between the satellite position and the position of the ground receiver; A first calculation module is used to calculate the large-scale fading caused by the meteorological environment for each valid ray path; The second calculation module is used to calculate the small-scale fading caused by multipath propagation and multi-terminal movement at the ground end for each effective ray path; The model generation module is used to generate a channel model by combining large-scale fading and small-scale fading.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the channel modeling method applicable to satellite-to-ground communication as claimed in any one of claims 1 to 6 is implemented.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the channel modeling method applicable to satellite-to-ground communication as claimed in any one of claims 1 to 6 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the channel modeling method applicable to satellite-to-ground communication as claimed in any one of claims 1 to 6 is implemented.

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