Modeling method for channel in high-speed train compartment

Abstract

The invention provides a modeling method for a channel in a high-speed train compartment, and belongs to the technical field of train communication. The method comprises the following steps: modeling a geometric model of a high-speed train compartment scene; generating a channel impact response in the high-speed train compartment scene based on the geometric model; modeling the directional antenna model of the high-speed train compartment scene; obtaining direct component power, reflection component power and scattering component power based on the modeling result of the directional antenna model of the high-speed train compartment scene and the generated channel impact response; and based on the obtained direct component power, the reflection component power and the scattering component power, generating high-speed train compartment scene channel statistical characteristics, and completing modeling of the channel in the high-speed train compartment. By introducing the directional antenna radiation mode and the refined modeling of the multipath reflection component, the accuracy of the GBSM under the carriage is remarkably improved, and the analysis of the time correlation and the space correlation under the carriage scene is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of train communications, and in particular relates to a modeling method for channels within a high-speed train compartment. Background Art

[0002] In the context of the development of intelligent high-speed rail and smart railways, building a high-precision 5G MIMO (Multiple-Input Multiple-Output) channel model within high-speed train carriages is an important technical foundation for achieving high-quality wireless coverage, improving passenger experience, and enhancing train operational efficiency. However, existing channel modeling methods for high-speed train carriages have the following key technical flaws: First, while existing statistical and deterministic modeling methods can effectively characterize the large-scale characteristics of the channel in vehicle scenarios, they generally lack in-depth analysis of the channel's temporal and spatial correlations. The lack of temporal correlation analysis prevents the model from reflecting the non-stationary characteristics of the channel, while the lack of spatial correlation analysis limits the optimization of MIMO system antenna array spacing and the potential for improving system capacity.

[0003] Secondly, existing geometry-based stochastic modeling methods (GBSM) cannot be directly applied to train compartment scenarios. Specifically, (1) train compartments are long and narrow, suitable for deploying directional antennas for coverage. Existing GBSM models lack the ability to characterize the radiation pattern of directional antennas. (2) Existing GBSM models fail to accurately characterize the multipath reflection characteristics within the compartment, especially the impact of strong reflection components generated by surfaces such as end walls, windows, and side walls on the channel impulse response.

[0004] Accurately modeling the channels within high-speed train carriages is fundamental to deploying 5G systems within these carriages. This helps ensure high-quality wireless connectivity within high-speed train carriages, improving the passenger experience and operational efficiency. Existing channel models are not suitable for the unique environment of high-speed train carriages and cannot support the deployment and optimization of MIMO systems.

[0005] Existing techniques involve building narrowband test systems to measure path loss inside high-speed rail cars and through glass. Combining high-precision 3D car models with ray tracing technology, a dynamic path loss prediction model has been proposed. This model, for the first time, incorporates the effects of multiple variables, such as base station height, station-track distance, and signal frequency, into its quantitative analysis. This allows for accurate prediction of large-scale channel fading characteristics in diverse scenarios, such as plains, tunnels, and viaducts. However, this method is complex to implement, requiring extensive field data to calibrate material parameters and propagation models. Furthermore, it primarily targets large-scale channel characteristics, without modeling small-scale features such as multipath effects and delay spread.

[0006] Existing technologies also disclose a three-dimensional spatial statistical channel modeling method for indoor environments. This method can derive important space-time channel parameters, such as the Doppler power spectrum, space-time correlation, and channel capacity. It uses the channel's space-time characteristic parameters to analyze the spatial model parameters and the mechanistic relationship between the angles of the directional antenna's main lobes. However, this method does not consider the impact of the specific environment on the channel model. High-speed train carriages are enclosed and long, with radio waves having multiple propagation paths, including direct radiation, reflection, and scattering. Furthermore, the areas where backscattering occurs are complex, requiring a specific approach tailored to the specific environmental characteristics.

[0007] Through the above analysis, the existing technical solutions have the following deficiencies: (1) The existing in-car channel model mainly analyzes the large-scale characteristics of the channel, lacks analysis of the small-scale characteristics of the channel and the channel correlation, and cannot support the deployment of 5G systems in the car. (2) The existing GBSM model is not applicable to the car scene. Since the car is closed and long, it is suitable for deploying directional antennas for coverage, but the existing GBSM model lacks the representation of the directional antenna radiation pattern. (3) The existing GBSM model fails to accurately represent the multipath reflection characteristics in the car, especially the impact of strong reflection components generated by surfaces such as end walls, windows, and side walls on the channel impulse response. Summary of the Invention

[0008] In response to the above-mentioned deficiencies in the prior art, the present invention provides a modeling method for channels within high-speed train carriages, which solves the problem of insufficient analysis of small-scale channel characteristics and channel correlation in current high-speed train carriage scenarios, and proposes a GBSM model suitable for carriage scenarios.

[0009] In order to achieve the above objectives, the present invention adopts a technical solution: a method for modeling a channel in a high-speed train compartment, comprising the following steps: Modeling the geometric model of the high-speed train carriage scene; Generate channel impulse responses in high-speed train compartment scenarios based on geometric models; Modeling of directional antenna models for high-speed train carriage scenarios; Based on the modeling results of the directional antenna model of the high-speed train compartment scenario and the generated channel impulse response, the direct component power, reflected component power and scattered component power are obtained; Based on the obtained direct component power, reflected component power and scattered component power, the statistical characteristics of the high-speed train compartment scene channel are generated to complete the modeling of the channel inside the high-speed train compartment.

[0010] The present invention has the following beneficial effects: Based on the existing GBSM model, this paper combines the unique electromagnetic propagation environment characteristics of high-speed train carriages to propose an improved GBSM channel modeling method for the 3.5 GHz frequency band. By introducing refined modeling of directional antenna radiation patterns and multipath reflection components, the accuracy of the GBSM model for the carriage environment is significantly improved, enabling the analysis of temporal and spatial correlations in the carriage scenario.

[0011] Furthermore, the expression of the channel impulse response is as follows:

[0012] in, represents the channel impulse response between any two antenna units of the transmitter and the receiver, 、 and Represent the impulse responses of direct component, scattered component and reflected component respectively; Channel response of the direct component Expressed as:

[0013] in, and Represent the total K factor and the direct component K factor, j represents the imaginary unit, represents the maximum Doppler shift, t Indicates time, represents the wavelength of the signal, and They represent the horizontal angle and elevation angle of the direct path, represents the propagation delay of the direct path, Indicates the unknown delay, ( ) represents the function of delay, Indicates antenna unit pq The propagation distance of the direct path, Expressed as:

[0014]

[0015] in, and are the coordinates of the transmitter and receiver respectively, and Respectively represent the number of antenna elements of the transmitting antenna and the number of antenna elements of the receiving antenna, and Respectively represent p The transmitting antenna unit and theq receiving antenna units, and They represent the antenna unit spacing of the transmitting antenna and the antenna unit spacing of the receiving antenna, and Represent the tilt angles of the transmitting antenna and the receiving antenna, and represents the horizontal and vertical coordinates of the receiving antenna unit, and Represents the horizontal and vertical coordinates of the transmitting antenna unit.

[0016] No. n Channel impulse response of the stripe scattered component Expressed as:

[0017] Where N is the number of scatterers, Indicates the n The power of the scattered path, Indicates the n The random phase variation of the strip scattering path obeys The normal distribution of and Respectively represent n The arrival horizontal angle and elevation angle of the scattered path, Indicates the n The time delay of the scattering path, Indicates the n The propagation distance of the scattering path, Expressed as:

[0018]

[0019]

[0020] in, Indicates the transmitting antenna p units To n The distance between the scatterers, Indicates the n scatterer to the receiving antenna q The distance between antenna elements, 、 、 、 Respectively represent n The departure horizontal angle, departure elevation angle, arrival horizontal angle and arrival elevation angle of each scattered path, and Respectively representn The distance from the first scatterer to the transmitting antenna is n The distance from the scatterer to the receiving antenna, and Expressed as:

[0021]

[0022] in, , , Indicates the n The coordinates of the scatterers, and It is obtained by the following formula:

[0023] in, Represents parameters related to the position of the scatterer. When the scatterers are located on the top and left and right side walls of the car, Expressed as:

[0024] in, Indicates the height of the roof. represents the height of the receiving antenna, Indicates the position of the left and right side walls of the carriage in the coordinate system, represents the horizontal coordinate of the receiving antenna; n Horizontal angle of arrival of the stripe scattering path and arrival pitch angle It obeys the two-dimensional von Mises distribution, and its probability density function Expressed as:

[0025] in, and are parameters that describe the distribution density of scatterers. and are the average arrival horizontal angle and average arrival elevation angle of the scattering path, represents the zero-order Bessel function; No. l Channel impulse response of the reflected component Expressed as:

[0026] in, Indicates the l The impulse response of the stripe scattered component, Indicates the l The reflection componentK factor, Indicates the l The time delay of the reflected component, Indicates the l The propagation distance of the reflected component, Indicates the l The horizontal angle of arrival of the reflected component, Indicates the l The arrival pitch angle of the reflected component, 、 、 Based on the geometric relationship of the reflection components, it is calculated using the following formula:

[0027]

[0028]

[0029] in, , , , , express pq The distance between the two antenna units projected on the reflecting surface, Represents the transmitting antenna unit p The distance to the reflecting surface, Represents the receiving antenna unit q The distance to the reflecting surface, and The height of the transmitting antenna and the height of the receiving antenna, represents the ordinate of the transmitting antenna, Indicates the vertical coordinate of the receiving antenna.

[0030] The beneficial effect of the above further solution is that, according to the environmental characteristics of the vehicle compartment, the channel impulse responses of the direct component, the reflected component and the scattered component are modeled respectively.

[0031] Furthermore, the expression of the direct component power is as follows:

[0032] in, Indicates the direct component power; The expression of the reflected component power is as follows:

[0033] in, and Both represent the reflected component power, represents the antenna gain matrix, and Respectively represent l The horizontal angle and elevation angle of the reflected component, and They represent the horizontal angle and elevation angle of the direct component, and Represents the propagation distance of the direct path and the l The propagation distance of the reflection path, Indicates the power of the direct path, represents the power loss during the reflection process, Calculated by the following formula:

[0034]

[0035]

[0036]

[0037] in, and represent the parallel reflection coefficient and the vertical reflection coefficient respectively, represents the incident angle of the reflection path, is the dielectric constant in vacuum, represents the complex relative permittivity of the reflecting medium surface, and represent the real part of the dielectric constant and conductivity of the reflective surface material, j represents the imaginary unit, f Indicates the frequency of electromagnetic waves; The expression of the scattered component power is as follows:

[0038] in, represents the scattered component power, and Respectively represent n The horizontal angle and elevation angle of the strip scattering component, and They represent the horizontal angle and elevation angle of the direct component, and Represent antenna units respectively pq The propagation distance of the direct path is n The propagation distance of a scattering path.

[0039] Furthermore, the channel statistical characteristics of the high-speed train compartment scene include the time-varying space-time correlation function of the direct component, the time-varying space-time correlation function of the reflected component, the time-varying space-time correlation function of the scattered component, and the diffusion characteristics.

[0040] The beneficial effect of the above further solution is that the powers of the direct component, the reflected component and the scattered component are modeled separately to derive the time-varying space-time correlation functions of the various components.

[0041] Furthermore, the expression of the time-varying space-time correlation function of the direct component is as follows:

[0042] in, represents the time-varying space-time correlation function of the direct component, Indicates time, Indicates the time interval, and Indicates the antenna unit spacing between the transmitting antenna and the receiving antenna, and Represent the total K factor and the direct component K factor, j represents the imaginary unit, Indicates antenna unit pq The propagation distance of the direct path, Indicates antenna unit The propagation distance of the direct path, represents the wavelength of the signal, represents the maximum Doppler shift, and They represent the horizontal angle and elevation angle of arrival of the straight path respectively; The expression of the time-varying space-time correlation function of the reflection component is as follows:

[0043] in, represents the time-varying space-time correlation function of the reflection component, l Indicates the l The reflected component, L represents the total number of reflection components, Indicates the l The reflection component K factor, Indicates antenna unit pq Intermediate l The propagation distance of the reflection path, Indicates antenna unit Intermediate l The propagation distance of the reflection path, Indicates the l The horizontal angle of arrival of the reflected component, Indicates the l Arrival pitch angle of the stripe reflection component; The expression of the time-varying space-time correlation function of the scattered component is as follows:

[0044]

[0045] in, represents the time-varying space-time correlation function of the scattered component, Indicates antenna unit pq Intermediate n The propagation distance of the scattering path, Indicates antenna unit The propagation distance of the nth scattering path, and Respectively represent n The arrival horizontal angle and elevation angle of the scattered path, express and function, represents the probability density function, Express and The points, and Respectively and The inverse function of and Respectively and The cumulative distribution function of and Respectively represent n The horizontal angle and elevation angle of arrival of the scattered path.

[0046] The beneficial effect of the above further solution is that the time-varying space-time correlation function of the direct component, the reflected component and the scattered component is derived, which is used to analyze the change of channel correlation.

[0047] Furthermore, the diffusion characteristic is expressed as follows:

[0048] in, Represents the dispersion characteristics of multipath signals in the delay domain, and Respectively represent k The power and delay of the strip components.

[0049] The beneficial effects of the above further solution are: the RMS delay spread of the high-speed train carriage channel is derived using the model, the dispersion characteristics of the channel are analyzed, and the accuracy of the model is verified. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 Flow chart of the method of the present invention.

[0050] Figure 2 It is a side view of the geometric model of the high-speed train carriage scene in the present invention.

[0051] Figure 3 This is a front view of the geometric model of the high-speed train carriage scene in the present invention.

[0052] Figure 4 Schematic diagram of the geometric relationship between the direct component and the scattered component in this embodiment.

[0053] Figure 5 Schematic diagram of the geometric relationship of the reflection components in this embodiment.

[0054] Figure 6 These are the horizontal and vertical radiation patterns of the antenna in this embodiment.

[0055] Figure 7 Schematic diagram of the comparison results of the RMS delay spread in this embodiment.

[0056] Figure 8 FIG. 4 is a schematic diagram of the time correlation of only the scattered component in this embodiment.

[0057] Figure 9 This is a schematic diagram of the time correlation of the embodiment in which the direct component exists and the reflected component is not considered.

[0058] Figure 10 Because there is a direct component in this embodiment, a schematic diagram of the time correlation of the reflected component is considered.

[0059] Figure 11 FIG. 4 is a schematic diagram of the spatial correlation of only the scattered component in this embodiment.

[0060] Figure 12 This is a schematic diagram showing that the direct component exists in this embodiment and the spatial correlation of the reflected component is not considered.

[0061] Figure 13 Because there is a direct component in this embodiment, a schematic diagram of spatial correlation of the reflected component is considered. DETAILED DESCRIPTION

[0062] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0063] Example like Figure 1 As shown, the present invention provides a modeling method for a channel in a high-speed train compartment, and its implementation method is as follows: Modeling the geometric model of the high-speed train carriage scene; Generate channel impulse responses in high-speed train compartment scenarios based on geometric models; Modeling of directional antenna models for high-speed train carriage scenarios; Based on the modeling results of the directional antenna model of the high-speed train compartment scenario and the generated channel impulse response, the direct component power, reflected component power and scattered component power are obtained; Based on the obtained direct component power, reflected component power and scattered component power, the statistical characteristics of the high-speed train compartment scene channel are generated to complete the modeling of the channel inside the high-speed train compartment. The statistical characteristics of the high-speed train compartment scene channel include the time-varying space-time correlation function of the direct component, the time-varying space-time correlation function of the reflected component, the time-varying space-time correlation function of the scattered component and the diffusion characteristics.

[0064] In this embodiment, the geometric model of the high-speed train car scene is constructed as follows: In order to concisely describe the high-speed rail car environment, the car can be modeled as a three-dimensional rectangular model. According to the actual size of the car, the rectangular model is determined to be 18.5 meters long, 3.36 meters wide, and 2.5 meters high. At the same time, there are windows arranged at certain intervals on the left and right walls. The windows are rectangular, the windows are 0.8m away from the bottom of the car, the first window is 0.5m away from the front wall, the window height is 0.8m, the length is 1.6m, and the distance between adjacent windows is 2m. There are 9 windows on each of the left and right walls. Secondly, there are end doors on the front and rear walls. The end doors are generally open by default. The end doors are located in the center of the front and rear end walls, with a width of 0.9m and a height of 2m. The side view and front view of the car are as follows Figure 2 and Figure 3 shown.

[0065] In this embodiment, the channel impulse response of the high-speed train compartment scenario is generated as follows: Based on the constructed geometric model, the scatterers are randomly distributed on the four walls of the carriage; at the same time, the reflection phenomenon on the left and right side walls and the rear end wall of the carriage is considered. A directional multi-antenna array is configured on the transmitter, and a uniform multi-antenna array is configured on the receiver. The geometric relationship between the transmitter, receiver, scatterers, and reflective surfaces in the rectangular carriage is used to obtain the direct component, reflected component, and scattered component of the channel in the carriage. The three components are added together to obtain the time-varying impulse response of the channel in the carriage. Channel impulse response between any two antenna units of the transmitter and receiver It can be expressed as: (1) in, 、 、 are the impulse responses of direct component, scattered component and reflected component respectively. The geometric relationship between direct component and scattered component is as follows: Figure 4 As shown: Channel response of the direct component Expressed as (2) in, and Represent the total K factor and the direct component K factor, j represents the imaginary unit, represents the maximum Doppler shift, t Indicates time, represents the wavelength of the signal, and They represent the horizontal angle and elevation angle of the direct path, represents the propagation delay of the direct path, Indicates the unknown delay, ( ) represents the function of delay, Indicates antenna unit pq The propagation distance of the direct path, Expressed as: (3) (4) in, and are the coordinates of the transmitter and receiver respectively, and Respectively represent the number of antenna elements of the transmitting antenna and the number of antenna elements of the receiving antenna, and Respectively represent p The transmitting antenna unit and the q receiving antenna units, and Indicates the antenna unit spacing between the transmitting antenna and the receiving antenna, and Represent the tilt angles of the transmitting antenna and the receiving antenna, and represents the horizontal and vertical coordinates of the receiving antenna unit, and Indicates the horizontal and vertical coordinates of the transmitting antenna unit. n Channel impulse response of the stripe scattered component It can be expressed as: (5) Where N is the number of scatterers, Indicates the n The power of the scattered path, Indicates the n The random phase variation of the strip scattering path obeys The normal distribution of and Respectively represent n The arrival horizontal angle and elevation angle of the scattered path, Indicates the n The time delay of the scattering path, Indicates the n The propagation distance of the scattering path, Expressed as: (6) and They can be calculated using the following formulas: (7) (8) in, Indicates the transmitting antenna p units To n The distance between the scatterers, Indicates the n scatterer to the receiving antenna q The distance between antenna elements, 、 、 、 Respectively represent n The departure horizontal angle, departure elevation angle, arrival horizontal angle and arrival elevation angle of each scattered path, and Respectively represent n The distance from the first scatterer to the transmitting antenna is n The distance from the scatterer to the receiving antenna. and Expressed as: (9) (10) in, , , Indicates the n The coordinates of the scatterers, and The following formula can be used for calculation: (11) in, Represents parameters related to the position of the scatterer. When the scatterers are located on the top and left and right side walls of the car, The expressions are as follows: (12) in, Indicates the height of the roof. represents the height of the receiving antenna, Indicates the position of the left and right side walls of the carriage in the coordinate system, Indicates the horizontal coordinate of the receiving antenna. n Horizontal angle of arrival of the stripe scattering path and arrival pitch angle It obeys the two-dimensional von Mises distribution, and its probability density function Expressed as: (13) in, and are parameters that describe the distribution density of scatterers. and are the average arrival horizontal angle and average arrival elevation angle of the scattering path, represents the zero-order Bessel function.

[0066] The geometric relationship of the reflection components is as follows Figure 5 shown.

[0067] No. l Channel impulse response of the reflected component It can be expressed as (14) in, Indicates the l The impulse response of the stripe scattered component, Indicates the l The reflection component K factor, j represents the imaginary unit, Indicates the l The time delay of the reflected component, Indicates the l The propagation distance of the reflected component, Indicates the l The horizontal angle of arrival of the reflected component, Indicates the l The arrival pitch angle of the reflected component, 、 、 Based on the geometric relationship of the reflection components, it is calculated using the following formula: (15) (16) (17) in, , , , , express pq The distance between the two antenna units projected on the reflecting surface, and Represent the transmitting antenna units p With receiving antenna unit q The distance to the reflecting surface, and The height of the transmitting antenna and the height of the receiving antenna, represents the ordinate of the transmitting antenna, Indicates the vertical coordinate of the receiving antenna.

[0068] In this example, the antenna model for a high-speed train carriage scenario is constructed as follows: Considering the narrow, long, and enclosed nature of the carriage, deploying a directional antenna for coverage is a more reasonable option. Next, the key parameters of the directional antenna are defined: a maximum antenna gain of 15dBi, a horizontal beamwidth of 65°, and a vertical beamwidth of 30°. A parabolic model is used to approximate the radiation pattern, using the following calculation formula: (18) (19) in, represents the antenna gain in the horizontal direction, Indicates the gain of the antenna in the vertical direction, represents the maximum gain of the antenna, and represent the horizontal angle and horizontal beam width respectively, and Represents the vertical angle and vertical beam width respectively. The horizontal and vertical radiation patterns of the directional antenna are as follows Figure 6 As shown, the antenna's horizontal and vertical patterns can be used to further derive the antenna's three-dimensional pattern, that is, the antenna gain matrix in any spatial direction. ,in represents the departure horizontal angle of the propagating component, Represents the departure elevation angle of the propagating component.

[0069] In this embodiment, the powers of the direct component, the reflected component, and the scattered component are generated as follows: The power of the direct component, reflected component and scattered component are all expressed using the corresponding K factor, which is recorded as 、 、 Total K Factor It is defined as the ratio of the power of the non-scattered component to the scattered component. The power of the scattered component is defined as 1, that is, 、 Next, the power corresponding to the direct component, reflected component and scattered component is calculated respectively according to the power relationship between the three.

[0070] Direct component power: The power of the direct component is defined as the K factor of the direct component, that is, , Indicates the direct component power.

[0071] Reflected component power: The power of the reflected component is defined as the K factor of the reflected component. The calculation method for the lth reflected component power is as follows: (20) in, and Both represent the reflected component power, represents the antenna gain matrix, and Respectively represent l The horizontal angle and elevation angle of the reflected component, and They represent the horizontal angle and elevation angle of the direct component, and Represents the propagation distance of the direct path and the l The propagation distance of the reflection path, represents the power of the direct component, It represents the power loss during the reflection process, which can be calculated using the parallel reflection coefficient and the vertical reflection coefficient. The calculation formula is as follows: (twenty one) (twenty two) (twenty three) in, and represent the parallel reflection coefficient and the vertical reflection coefficient respectively, represents the incident angle of the reflection path, Represents the dielectric constant in a vacuum, which is 8.854187817×10-12 Faraday meter. -1 , is the complex relative permittivity of the reflecting medium surface, which can be calculated by the following formula: (twenty four) in, and represent the real part of the dielectric constant and conductivity of the reflective surface material, j represents the imaginary unit, f Represents the frequency of the electromagnetic wave. Based on the modeling of the geometric model, the reflection phenomenon occurs at the end wall and side wall. The material of the reflective surface at the end wall is a smooth wooden surface, and the reflective surface material at the side wall is glass or metal car body. The electromagnetic parameters of these three possible reflective surface materials are shown in Table 1 below. Table 1 is the electromagnetic parameter table of the reflective surface material.

[0072] Table 1

[0073] Scattering component power: The definition of scattered component power is similar to that of reflected component. The total power of all scattered components is 1, that is, , No. n The power of the stripe scattered component is calculated as follows: (25) in, represents the antenna gain matrix, 、 Respectively represent n The horizontal angle and elevation angle of the strip scattering component, and They represent the horizontal angle and elevation angle of the direct component, and Represent antenna units respectively pq The propagation distance of the direct path is n The propagation distance of a scattering path.

[0074] In this embodiment, the channel statistical features of the high-speed train compartment scene are generated as follows: (1) Time-varying space-time correlation function The correlation characteristics of two arbitrary channel impulse responses can be expressed as: (26) in, represents the complex conjugate operation, is the expectation operator. Considering that the direct component, reflected component and scattered component are independent of each other, the time-varying space-time correlation function can be further expressed as: (27) In formula (27), when and When , the time correlation function can be obtained. and When , the spatial correlation function can be obtained. Among them, the time-varying spatial-temporal correlation function of the direct component can be expressed as: (28) The time-varying space-time correlation function of the reflection component can be expressed as (29) in, represents the time-varying space-time correlation function of the reflection component, l Indicates the l The reflected component, L represents the total number of reflection components, Indicates the l The reflection component K factor, Indicates antenna unit pq Intermediate l The propagation distance of the reflection path, Indicates antenna unit Intermediate l The propagation distance of the reflection path, Indicates the l The horizontal angle of arrival of the reflected component, Indicates the l Arrival elevation angle of the stripe reflection component; The time-varying space-time correlation function of the scattered component can be expressed as: (30) in, represents the time-varying space-time correlation function of the scattered component, Indicates antenna unit pq Intermediate n The propagation distance of the scattering path, Indicates antenna unit The propagation distance of the nth scattering path, and Respectively represent n The arrival horizontal angle and elevation angle of the scattered path, express and function, Express and The points, and Respectively and The inverse function of and Respectively and The cumulative distribution function of and Respectively represent n The horizontal angle and elevation angle of arrival of the scattered path.

[0075] Equation (30) calculates the time-varying space-time correlation function of the scattered component when the number of scatterers is infinite. In practice, the number of scatterers is usually limited, and appropriate numerical calculation methods are needed to estimate the parameters of the arrival angle. The Method of Equal Areas (MEA) is a low-complexity and high-precision parameter calculation method. The formulas for calculating the horizontal angle of arrival and the pitch angle of arrival of the scattered component using the MEA method are as follows: (31) in, and Respectively and The inverse function of and They are and The cumulative distribution function (CDF) of , that is, the CDF of the von Mises distribution.

[0076] (2) Root mean square delay spread The root mean square delay spread (RMS Delay Spread) is used to describe the dispersion characteristics of multipath signals in the delay domain and can be calculated using the following formula: (32) in, and represent the power and delay of the kth component respectively.

[0077] In this embodiment, the high-speed train carriage scenario channel model is verified and the results are analyzed as follows.

[0078] In order to verify the accuracy of the proposed model, the present invention modeled a three-dimensional scene of a high-speed train carriage and simulated it using ray tracing technology. The RMS delay spread was obtained after processing the simulation results. This result was compared with the RMS delay spread calculated in Equation (32) and the RMS delay spread of the 3GPP standard model. The results are shown in Figure 2. Figure 7 As shown in the figure, the results show significant differences between the 3GPP standard model and the ray tracing results, indicating that existing standard channel models are unable to accurately characterize the channel characteristics of high-speed rail carriage scenarios. It is worth noting that when the influence of the reflected component (REF) is considered, the GBSM modeling results show better consistency with the ray tracing data. This not only verifies the accuracy of the proposed model, but also proves the necessity of considering the reflected component in carriage channel modeling.

[0079] Figure 8 、 Figure 9 and Figure 10 The absolute values of the time correlation functions for different propagation components are shown. Assuming the receiving antenna moves toward the transmitting antenna at a speed of 2 m / s, when only the scattered component is present, the time correlation at each receiving position decays rapidly and eventually stabilizes around 0.1. When the direct component is present, the time correlation briefly decreases before stabilizing at approximately 0.9. When the reflected component is present, all receiving positions exhibit a continuous decay characteristic, and the closer the receiving end is to the transformer antenna, the lower the time correlation. This phenomenon indicates that the reflected component can effectively reduce the time correlation of the receiving antenna.

[0080] Figure 11 、 Figure 12 and Figure 13 The absolute value variation of the spatial correlation function for different propagation components is demonstrated. The experimental results show that when only scattered components are present at the receiver, the spatial correlation continuously decays with increasing receive antenna (Rx) spacing. When direct components are present, the spatial correlation fluctuates consistently between 0.8 and 0.9. When reflected components are introduced, the spatial correlation exhibits a non-monotonic characteristic of first decreasing and then increasing, reaching a minimum value of 0.1 when the receive antenna spacing reaches approximately 0.3 meters. These data confirm that reflected components can significantly reduce the spatial correlation between different receiving locations, reducing it to approximately 0.1 at optimal antenna spacing, thereby significantly improving the channel capacity of the MIMO system.

[0081] In summary, the present invention establishes a GBSM channel model suitable for the high-speed train compartment environment; the present invention models a directional antenna for coverage based on the closed and narrow characteristics of the compartment scene, making the model closer to the actual application scenario; the present invention takes into account the specific conditions inside the compartment and introduces reflection components under different situations into the channel model, thereby improving the accuracy of the model; the present invention takes into account the possible movement conditions in the compartment scene and analyzes the channel characteristics inside the compartment under time-varying conditions; the present invention analyzes small-scale characteristics such as time correlation and spatial correlation inside the compartment, filling the gaps in existing research.

Claims

1. A method for modeling a channel in a high-speed train compartment, characterized in that: The following steps are involved: Modeling the geometric model of the high-speed train carriage scene; Generate channel impulse responses in high-speed train compartment scenarios based on geometric models; Modeling of directional antenna models for high-speed train carriage scenarios; Based on the modeling results of the directional antenna model of the high-speed train compartment scenario and the generated channel impulse response, the direct component power, reflected component power and scattered component power are obtained; Based on the obtained direct component power, reflected component power and scattered component power, the statistical characteristics of the high-speed train compartment scene channel are generated to complete the modeling of the channel inside the high-speed train compartment.

2. The method for modeling a channel in a high-speed train compartment according to claim 1, characterized in that: The expression of the channel impulse response is as follows: in, represents the channel impulse response between any two antenna units of the transmitter and the receiver, 、 and Represent the impulse responses of direct component, scattered component and reflected component respectively; Channel response of the direct component Expressed as: in, and Represent the total K factor and the direct component K factor, j represents the imaginary unit, represents the maximum Doppler shift, t Indicates time, represents the wavelength of the signal, and They represent the horizontal angle and elevation angle of the direct path, represents the propagation delay of the direct path, Indicates the unknown delay, ( ) represents the function of delay, Indicates antenna unit pq The propagation distance of the direct path, Expressed as: in, and are the coordinates of the transmitter and receiver respectively, and Respectively represent the number of antenna elements of the transmitting antenna and the number of antenna elements of the receiving antenna, and Respectively represent p The transmitting antenna unit and the q receiving antenna units, and They represent the antenna unit spacing of the transmitting antenna and the antenna unit spacing of the receiving antenna, and Represent the tilt angles of the transmitting antenna and the receiving antenna, and represents the horizontal and vertical coordinates of the receiving antenna unit, and Represents the horizontal and vertical coordinates of the transmitting antenna unit. No. n Channel impulse response of the stripe scattered component Expressed as: Where N is the number of scatterers, Indicates the n The power of the scattered path, Indicates the n The random phase variation of the strip scattering path obeys The normal distribution of and Respectively represent n The arrival horizontal angle and elevation angle of the scattered path, Indicates the n The time delay of the scattering path, Indicates the n The propagation distance of the scattering path, Expressed as: in, Indicates the transmitting antenna p units To n The distance between the scatterers, Indicates the n scatterer to the receiving antenna q The distance between antenna elements, 、 、 、 Respectively represent n The departure horizontal angle, departure elevation angle, arrival horizontal angle and arrival elevation angle of each scattered path, and Respectively represent n The distance from the first scatterer to the transmitting antenna is n The distance from the scatterer to the receiving antenna, and Expressed as: in, , , Indicates the n The coordinates of the scatterers, and It is obtained by the following formula: in, Represents parameters related to the position of the scatterer. When the scatterers are located on the top and left and right side walls of the car, Expressed as: in, Indicates the height of the roof. represents the height of the receiving antenna, Indicates the position of the left and right side walls of the carriage in the coordinate system, represents the horizontal coordinate of the receiving antenna; n Horizontal angle of arrival of the stripe scattering path and arrival pitch angle It obeys the two-dimensional von Mises distribution, and its probability density function Expressed as: in, and are parameters that describe the distribution density of scatterers. and are the average arrival horizontal angle and average arrival elevation angle of the scattering path, represents the zero-order Bessel function; No. l Channel impulse response of the reflected component Expressed as: in, Indicates the l The impulse response of the stripe scattered component, Indicates the l The reflection component K factor, Indicates the l The time delay of the reflected component, Indicates the l The propagation distance of the reflected component, Indicates the l The horizontal angle of arrival of the reflected component, Indicates the l The arrival pitch angle of the reflected component, 、 、 Based on the geometric relationship of the reflection components, it is calculated using the following formula: in, , , , , express pq The distance between the two antenna units projected on the reflecting surface, Represents the transmitting antenna unit p The distance to the reflecting surface, Represents the receiving antenna unit q The distance to the reflecting surface, and The height of the transmitting antenna and the height of the receiving antenna, represents the ordinate of the transmitting antenna, Indicates the vertical coordinate of the receiving antenna.

3. The method for modeling a channel in a high-speed train compartment according to claim 2, characterized in that: The expression of the direct component power is as follows: in, Indicates the direct component power; The expression of the reflected component power is as follows: in, and Both represent the reflected component power, represents the antenna gain matrix, and Respectively represent l The horizontal angle and elevation angle of the reflected component, and They represent the horizontal angle and elevation angle of the direct component, and Represents the propagation distance of the direct path and the l The propagation distance of the reflection path, Indicates the power of the direct diameter represents the power loss during the reflection process, Calculated by the following formula: in, and represent the parallel reflection coefficient and the vertical reflection coefficient respectively, represents the incident angle of the reflection path, is the dielectric constant in vacuum, represents the complex relative permittivity of the reflecting medium surface, and represent the real part of the dielectric constant and conductivity of the reflective surface material, j represents the imaginary unit, f Indicates the frequency of electromagnetic waves; The expression of the scattered component power is as follows: in, represents the scattered component power, and Respectively represent n The horizontal angle and elevation angle of the strip scattering component, and They represent the horizontal angle and elevation angle of the direct component, and Represent antenna units respectively pq The propagation distance of the direct path is n The propagation distance of a scattering path.

4. The method for modeling a channel in a high-speed train compartment according to claim 1, characterized in that: The channel statistical characteristics of the high-speed train compartment scene include the time-varying space-time correlation function of the direct component, the time-varying space-time correlation function of the reflected component, the time-varying space-time correlation function of the scattered component, and the diffusion characteristics.

5. The method for modeling a channel in a high-speed train compartment according to claim 4, characterized in that: The expression of the time-varying space-time correlation function of the direct component is as follows: in, represents the time-varying space-time correlation function of the direct component, Indicates time, Indicates the time interval, and Indicates the antenna unit spacing between the transmitting antenna and the receiving antenna, and Represent the total K factor and the direct component K factor, j represents the imaginary unit, Indicates antenna unit pq The propagation distance of the direct path, Indicates antenna unit The propagation distance of the direct path, represents the wavelength of the signal, represents the maximum Doppler shift, and They represent the horizontal angle and elevation angle of arrival of the straight path respectively; The expression of the time-varying space-time correlation function of the reflection component is as follows: in, represents the time-varying space-time correlation function of the reflection component, l Indicates the l The reflected component, L represents the total number of reflection components, Indicates the l The reflection component K factor, Indicates antenna unit pq Intermediate l The propagation distance of the reflection path, Indicates antenna unit Intermediate l The propagation distance of the reflection path, Indicates the l The horizontal angle of arrival of the reflected component, Indicates the l Arrival pitch angle of the stripe reflection component; The expression of the time-varying space-time correlation function of the scattered component is as follows: in, represents the time-varying space-time correlation function of the scattered component, Indicates antenna unit pq Intermediate n The propagation distance of the scattering path, Indicates antenna unit The propagation distance of the nth scattering path, and Respectively represent n The arrival horizontal angle and elevation angle of the scattered path, express and function, represents the probability density function, Express and The points, and Respectively and The inverse function of and Respectively and The cumulative distribution function of and Respectively represent n The horizontal angle and elevation angle of arrival of the scattered path.

6. The method for modeling a channel in a high-speed train compartment according to claim 4, characterized in that: The expression of the diffusion characteristic is as follows: in, Represents the dispersion characteristics of multipath signals in the delay domain, and Respectively represent k The power and delay of the strip components.

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