A method for modeling an in-car channel of a high-speed train

Abstract

The application provides a modeling method of a high-speed train carriage channel, and belongs to the technical field of train communication. The method comprises the following steps: modeling a geometric model of a high-speed train carriage scene; generating a channel impulse response in the high-speed train carriage scene based on the geometric model; modeling a directional antenna model of the high-speed train carriage scene; obtaining direct component power, reflected component power and scattered component power based on the modeling result of the directional antenna model of the high-speed train carriage scene and the generated channel impulse response; and generating high-speed train carriage scene channel statistical characteristics based on the obtained direct component power, reflected component power and scattered component power, so as to complete the modeling of the high-speed train carriage channel. Through the introduction of the fine modeling of the directional antenna radiation mode and the multipath reflected component, the accuracy of the GBSM model under the carriage is significantly improved, and the analysis of the time correlation and the space correlation under the carriage scene is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of train communication, and particularly relates to a modeling method of a channel in a high-speed train carriage. BACKGROUND

[0002] Under the background of intelligent high-speed rail and smart rail, constructing a high-precision 5G MIMO (Multiple-Input Multiple-Output) channel model in a high-speed train carriage is an important technical basis for realizing high-quality wireless coverage, improving passenger experience and train operation efficiency. However, the existing channel modeling methods for high-speed train carriage scenarios have the following key technical defects:

[0003] Firstly, although the existing statistical modeling and deterministic modeling methods can effectively represent the large-scale characteristics of the channel in the carriage scenario, they generally lack in-depth analysis of the time correlation and spatial correlation of the channel. The lack of time correlation analysis results in the model being unable to reflect the non-stationary characteristics of the channel, and the lack of spatial correlation analysis limits the optimization of the antenna array spacing of the MIMO system and the improvement of the system capacity.

[0004] Secondly, the existing Geometry Based Stochastic Models (GBSM) cannot be directly applied to the carriage scenario. Specifically, (1) the train carriage is closed and narrow, and is suitable for deploying directional antennas for coverage, and the existing GBSM model lacks representation of the radiation pattern of directional antennas; (2) the existing GBSM model fails to accurately represent the multi-path reflection characteristics in the carriage, especially the influence of strong reflection components generated by the end wall, windows and side walls on the channel impulse response.

[0005] Accurate modeling of the channel in the high-speed train carriage is the basis for deploying 5G systems in the carriage, which helps to ensure high-quality wireless connections in the high-speed train carriage and improve passenger experience and train operation efficiency. The existing channel models cannot be applied to the unique environment of the high-speed train carriage and cannot support the deployment and optimization of MIMO systems.

[0006] In the prior art, a narrowband test system is built to measure the path loss in the high-speed rail carriage and the glass, and a dynamic path loss prediction model is proposed by combining a high-precision 3D carriage model and a ray tracing technology. For the first time, multiple variable coupling effects such as base station height, station-track distance and signal frequency are included in the quantitative analysis, which can accurately predict the large-scale fading characteristics of the channel in different scenarios (such as plains, tunnels and viaducts). However, this method has the problem of high implementation complexity, as it needs to rely on a large amount of measured data to calibrate material parameters and propagation models, and mainly targets large-scale channel characteristics, without modeling the small-scale characteristics such as multipath effect and delay spread.

[0007] The prior art also discloses a three-dimensional space statistical channel modeling method for an indoor space, which can derive important space-time channel parameters such as a Doppler power spectrum, a space-time correlation, and a channel capacity, and analyzes the mechanism relationship between the space model parameters and the main lobe angle of the directional antenna by using the space-time characteristic parameters of the channel. However, the method does not consider the influence of a specific environment on the channel model. The train carriage scene has the characteristics of being closed and narrow, and there are multiple propagation paths such as direct radiation, reflection, scattering, and the area where backscattering occurs is complex, and it is necessary to be suitable for the characteristics of the environment.

[0008] Through the above analysis, the existing technical solutions have the following disadvantages: (1) The existing channel model in the carriage mainly analyzes the large-scale characteristics of the channel, lacks analysis of the small-scale characteristics of the channel and the correlation of the channel, and cannot support the deployment of the 5G system in the carriage. (2) The existing GBSM model cannot be applied to the carriage scene. Since the carriage is closed and narrow, it is suitable to deploy directional antennas for coverage, but the existing GBSM model lacks representation of the radiation mode of the directional antenna. (3) The existing GBSM model cannot accurately represent the multi-path reflection characteristics in the carriage, especially the influence of strong reflection components generated by the end wall, the window, and the side wall on the channel impulse response. SUMMARY

[0009] In view of the above problems in the prior art, the present application provides a modeling method for a channel in a high-speed train carriage, which solves the problem of insufficient analysis of the small-scale characteristics of the channel and the correlation of the channel in the current high-speed train carriage scene, and proposes a GBSM model suitable for the carriage scene.

[0010] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: a modeling method for a channel in a high-speed train carriage, comprising the following steps:

[0011] Modeling the geometric model of the high-speed train carriage scene;

[0012] Based on the geometric model, generating the channel impulse response in the high-speed train carriage scene;

[0013] Modeling the directional antenna model of the high-speed train carriage scene;

[0014] Based on the modeling results of the directional antenna model of the high-speed train carriage scene and the generated channel impulse response, obtaining the direct component power, the reflection component power and the scattering component power;

[0015] Based on the obtained direct component power, reflection component power and scattering component power, generating the channel statistical characteristics of the high-speed train carriage scene, and completing the modeling of the channel in the high-speed train carriage.

[0016] The beneficial effects of this invention are as follows: Based on the existing GBSM model, and combined with the unique electromagnetic propagation environment characteristics of high-speed train carriages, this invention proposes an improved GBSM channel modeling method in the 3.5GHz band. By introducing refined modeling of directional antenna radiation modes and multipath reflection components, the accuracy of the GBSM model under the carriage is significantly improved, and the analysis of temporal and spatial correlations in the carriage scenario is realized.

[0017] Furthermore, the expression for the channel impulse response is as follows:

[0018]

[0019] in, This represents the channel impulse response between any two antenna elements of the transmitter and receiver. , and These represent the impact responses of the direct component, the scattered component, and the reflected component, respectively.

[0020] Channel response of direct component Represented as:

[0021]

[0022] in, and Let K-factors be the total K-factor and the K-factors of the direct component, respectively. j Represents the imaginary unit. Indicates the maximum Doppler frequency shift. t Indicates time, Indicates the wavelength of the signal. and These represent the horizontal and vertical angles of arrival of the direct trajectory, respectively. Indicates the propagation delay of the direct path. Indicates the time delay unknown. ( ) represents a function of time delay. Antenna element pq The propagation distance of the direct beam. Represented as:

[0023]

[0024]

[0025] in, and These represent the coordinates of the transmitter and receiver, respectively. and These represent the number of antenna elements in the transmitting antenna and the number of antenna elements in the receiving antenna, respectively. and denote the first p transmit antenna element and the first q receive antenna element, respectively, and denote the antenna element spacing of the transmit antenna and the receive antenna, respectively, and denote the tilt angle of the transmit antenna and the receive antenna, respectively, and denote the horizontal and vertical coordinates of the receive antenna element, respectively, and denote the horizontal and vertical coordinates of the transmit antenna element, respectively.

[0026] the first n scatter component channel impulse response is denoted as:

[0027]

[0028] where N denotes the number of scatterers, denotes the power of the first n scatter path, denotes the random phase variation of the first n scatter path, which is subject to a normal distribution , and denote the horizontal and vertical angles of arrival of the first n scatter path, respectively, denotes the time delay of the first n scatter path, denotes the propagation distance of the first n scatter path, is denoted as:

[0029]

[0030]

[0031]

[0032] where, denotes the distance between the first p element of the transmit antenna and the first n scatterer, denotes the distance between the first n scatterer and the first q element of the receive antenna, , , , They represent the first n The starting horizontal angle, starting pitch angle, arrival horizontal angle, and arrival pitch angle of the scattering path. and They represent the first n The distance from the first scatterer to the transmitting antenna is the same as the distance from the second scatterer to the transmitting antenna. n The distance from each scatterer to the receiving antenna, and Represented as:

[0033]

[0034]

[0035] in, , , Indicates the first n The coordinates of the scatterer and We obtain it from the following formula:

[0036]

[0037] in, This represents a parameter related to the location of the scatterer, when the scatterer is located on the top of the carriage and the left and right side walls, respectively. Represented as:

[0038]

[0039] in, Indicates the height of the car roof. Indicates the height of the receiving antenna. This indicates the positions of the left and right side walls of the carriage in the coordinate system. The x-coordinate of the receiving antenna; the first... n Horizontal angle of arrival of the scattering path With the pitch angle reached It follows a two-dimensional von Mises distribution, and its probability density function is... Represented as:

[0040]

[0041] in, and Both represent parameters that characterize the distribution density of the scatterer. and These represent the average horizontal angle of arrival and the average vertical angle of arrival of the scattered path, respectively. Represents the zeroth-order Bessel function;

[0042] No. l Channel impulse response of the reflected component denotes the direct component,

[0043]

[0044] denotes the direct component, denotes the impulse response of the l th scattering component, denotes the l th reflection component, K factor of the th reflection component, l denotes the time delay of the th reflection component, l denotes the propagation distance of the th reflection component, l denotes the arrival horizontal angle of the th reflection component, l denotes the arrival elevation angle of the , , Based on the geometric relationship of the reflection component, the following formula is used for calculation:

[0045]

[0046]

[0047]

[0048] wherein, , , , , denotes the distance between the two antenna units on the reflection surface projection, pq denotes the distance between the transmitting antenna unit and the reflection surface, p denotes the distance between the receiving antenna unit and the reflection surface, q and denotes the height of the transmitting antenna and the height of the receiving antenna respectively, denotes the longitudinal coordinate of the transmitting antenna, denotes the longitudinal coordinate of the receiving antenna.

[0049] The above further scheme has the beneficial effect that the channel impulse response of the direct component, the reflection component, and the scattering component is respectively modeled according to the environmental characteristics of the vehicle cabin.

[0050] Further, the expression of the direct component power is as follows:

[0051] ​

[0052] wherein, represents the direct component power;

[0053] The expression of the reflected component power is as follows:

[0054]

[0055] wherein, and both represent the reflected component power, represents the gain matrix of the antenna, and respectively represent the departure horizontal angle and the departure elevation angle of the l th reflected path, and respectively represent the departure horizontal angle and the departure elevation angle of the direct path, and respectively represent the propagation distance of the direct path and the propagation distance of the l th reflected path, represents the power of the direct path, represents the power loss in the reflection process, is calculated by the following formula:

[0056]

[0057]

[0058]

[0059]

[0060] wherein, and respectively represent the parallel reflection coefficient and the perpendicular reflection coefficient, represents the incident angle of the reflected path, represents the dielectric constant in vacuum, represents the complex relative dielectric constant of the surface of the reflecting medium, and respectively represent the real part of the dielectric constant and the conductivity of the reflecting surface material, j represents the imaginary unit, f represents the frequency of the electromagnetic wave;

[0061] The expression of the scattered component power is as follows:

[0062]

[0063] wherein, represents the scattered component power, and They represent the first n The angles of departure from the horizontal and vertical scattering components, and These represent the angles of departure from the horizontal and the angles of departure from the pitch of the direct component, respectively. and Representing antenna elements pq The propagation distance of the direct trajectory and the first n The propagation distance of the scattering path.

[0064] Furthermore, the channel statistical characteristics of the high-speed train carriage 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.

[0065] The beneficial effect of the above-mentioned further scheme is that it models the power of the direct component, the reflected component and the scattered component respectively, which is used to derive the time-varying space-time correlation function of various components.

[0066] Furthermore, the expression for the time-varying space-time correlation function of the direct component is as follows:

[0067]

[0068] in, The time-varying spacetime correlation function representing the direct component, Indicates time, Indicates time interval, and This indicates the antenna element spacing between the transmitting and receiving antennas. and Let K-factors be the total K-factor and the K-factors of the direct component, respectively. j Represents the imaginary unit. Antenna element pq The propagation distance of the direct beam. Antenna element The propagation distance of the direct beam. Indicates the wavelength of the signal. Indicates the maximum Doppler frequency shift. and These represent the horizontal and vertical angles of arrival of the direct trajectory, respectively.

[0069] The expression for the time-varying space-time correlation function of the reflection component is as follows:

[0070]

[0071] in, The time-varying spacetime correlation function representing the reflection component. l Indicates the first l Bar reflection component,L denotes the total number of reflection components, denotes the first l reflection component, K factor, denotes the propagation distance of the pq reflection path between the antenna elements, l denotes the propagation distance of the reflection path between the antenna elements, denotes the propagation distance of the l reflection path between the antenna elements, denotes the arrival horizontal angle of the first l reflection component, denotes the arrival elevation angle of the first l reflection component;

[0072] The expression of the time-varying spatial correlation function of the scattering components is as follows:

[0073]

[0074]

[0075] wherein, denotes the time-varying spatial correlation function of the scattering components, denotes the propagation distance of the pq scattering path between the antenna elements, n denotes the propagation distance of the scattering path between the antenna elements, denotes the propagation distance of the n-th scattering path between the antenna elements, denotes the arrival horizontal angle and the arrival elevation angle of the n n-th scattering path, respectively, denotes and as a function of, denotes the probability density function, denotes the integral of and , respectively, and denote the inverse function of and , respectively, and denote the cumulative distribution function of and , respectively, and denote the arrival horizontal angle and the arrival elevation angle of the n n-th scattering path, respectively.

[0076] The beneficial effect of the further scheme is that time-varying space-time correlation functions of the direct component, the reflection component and the scattering component are derived for analyzing the change of channel correlation.

[0077] Further, the expression of the dispersion characteristic is as follows:

[0078]

[0079] wherein, denotes the dispersion characteristic of the multipath signal in the time delay domain, and denote the power and the time delay of the first k component, respectively.

[0080] The beneficial effect of the further scheme is that the root mean square time delay spread of the high-speed train carriage channel is derived by using the model, the dispersion characteristic of the channel is analyzed, and the accuracy of the model is verified BRIEF DESCRIPTION OF DRAWINGS

[0081] Figure 1 is a flow chart of the method of the present application.

[0082] Figure 2 is a side view of the high-speed train carriage scene geometric model in the present application.

[0083] Figure 3 is a front view of the high-speed train carriage scene geometric model in the present application.

[0084] Figure 4 is a schematic diagram of the geometric relationship between the direct component and the scattering component in the present embodiment.

[0085] Figure 5 is a schematic diagram of the geometric relationship of the reflection component in the present embodiment.

[0086] Figure 6 is an antenna horizontal pattern and a vertical pattern in the present embodiment.

[0087] Figure 7 is a schematic diagram of the root mean square time delay spread comparison result in the present embodiment.

[0088] Figure 8 is a schematic diagram of the time correlation of only the scattering component in the present embodiment.

[0089] Figure 9 is a schematic diagram of the time correlation of the direct component in the present embodiment, without considering the reflection component.

[0090] Figure 10 is a schematic diagram of the time correlation of the direct component in the present embodiment, considering the reflection component.

[0091] Figure 11This is a schematic diagram illustrating the spatial correlation of only the scattering component in this embodiment.

[0092] Figure 12 This is a schematic diagram showing the presence of a direct component in this embodiment, without considering the spatial correlation of the reflected component.

[0093] Figure 13 This embodiment includes a direct component, and a schematic diagram considering the spatial correlation of the reflected component. Detailed Implementation

[0094] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0095] Example

[0096] like Figure 1 As shown, this invention provides a method for modeling the channel inside a high-speed train carriage, the implementation of which is as follows:

[0097] Model the geometric model of the high-speed train carriage scene;

[0098] Based on a geometric model, the channel impulse response in a high-speed train carriage scenario is generated.

[0099] Modeling a directional antenna model for a high-speed train carriage scenario;

[0100] Based on the modeling results of the directional antenna model of the high-speed train carriage scene and the generated channel impulse response, the direct component power, reflected component power and scattered component power are obtained.

[0101] Based on the obtained direct component power, reflected component power, and scattered component power, channel statistical features of the high-speed train carriage scene are generated to complete the modeling of the channel inside the high-speed train carriage. The channel statistical features of the high-speed train carriage 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.

[0102] In this embodiment, the high-speed train carriage scene geometry model is constructed as follows: for the sake of simple description of the high-speed train carriage environment, the carriage can be modeled as a three-dimensional cuboid model. According to the actual size of the carriage, the length of the cuboid model is determined to be 18.5 meters, the width is 3.36 meters, and the height is 2.5 meters. At the same time, there are windows arranged at certain intervals on the left and right walls, and the windows are rectangular. The distance from the window to the bottom of the carriage is 0.8 m, the distance from the first window to the front wall is 0.5 m, the height of the window is 0.8 m, the length of the window is 1.6 m, and the distance between adjacent windows is 2 m. There are 9 windows on each of the left and right walls. Secondly, there are end doors on the front and rear walls, which are generally assumed to be open. The end door is located in the center of the front and rear walls, with a width of 0.9 m and a height of 2 m. The side view and front view of the carriage are shown in Figure 2 and Figure 3 .

[0103] In this embodiment, the high-speed train carriage scene channel impulse response is generated as follows:

[0104] Based on the constructed geometry model, the scatterers are randomly distributed on the four walls of the carriage. At the same time, the reflection phenomenon exists on the left and right side walls and the rear wall of the carriage. 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 reflecting surfaces in the rectangular carriage is used to obtain the direct component, reflection component, and scattering component of the channel in the carriage. The sum of the three components is added to obtain the time-varying impulse response of the channel in the carriage. The channel impulse response between any two antenna elements of the transmitter and the receiver can be represented as:

[0105] (1)

[0106] wherein, , , are the impulse responses of the direct component, scattering component, and reflection component, respectively. The geometric relationship of the direct component and the scattering component is shown in Figure 4 :

[0107] The channel response of the direct component is represented as

[0108] (2)

[0109] wherein, and represent the total K factor and the K factor of the direct component, respectively, j represents the imaginary unit, represents the maximum Doppler shift, t represents time, represents the wavelength of the signal, and These represent the horizontal and vertical angles of arrival of the direct trajectory, respectively. Indicates the propagation delay of the direct path. Indicates the time delay unknown. ( ) represents a function of time delay. Antenna element pq The propagation distance of the direct beam. Represented as:

[0110] (3)

[0111] (4)

[0112] in, and These represent the coordinates of the transmitter and receiver, respectively. and These represent the number of antenna elements in the transmitting antenna and the number of antenna elements in the receiving antenna, respectively. and They represent the first p The first transmitting antenna element and the first q One receiving antenna unit, and This indicates the antenna element spacing between the transmitting and receiving antennas. and These represent the tilt angles of the transmitting and receiving antennas, respectively. and The x and y coordinates of the receiving antenna element are represented. and This represents the x and y coordinates of the transmitting antenna element. n Channel impulse response of scattering components It can be represented as:

[0113] (5)

[0114] Where N represents the number of scatterers. Indicates the first n The power of the scattering path, Indicates the first n The random phase variation of the scattering path follows a certain order. The normal distribution and They represent the first n The horizontal and vertical angles of arrival of the scattered path. Indicates the first n The time delay of the scattering path, Indicates the first n The propagation distance of the scattering path, is expressed as:

[0115] (6)

[0116] and can be calculated using the following equations, respectively:

[0117] (7)

[0118] (8)

[0119] wherein, denotes the distance between the jth element of the transmitting antenna and the ith scatterer, p denotes the distance between the ith scatterer and the jth element of the receiving antenna, , n , , n , q , , , , denote the departure horizontal angle, the departure elevation angle, the arrival horizontal angle and the arrival elevation angle of the ith scattering path, respectively, n and denote the distance of the ith scatterer to the transmitting antenna and the distance of the ith scatterer to the receiving antenna, respectively. and n are expressed as: n

[0120] (9)

[0121] (10)

[0122] wherein, , , denote the coordinates of the ith scatterer, n and can be calculated using the following equations:

[0123] (11) wherein,

[0124] denotes a parameter related to the scatterer position, and when the scatterer is located at the top of the vehicle cabin and at the left and right side walls, respectively, the expressions of are as follows, respectively:

[0125] (12)​​​

[0126] wherein, denotes the height of the roof, denotes the height of the receiving antenna, denotes the position of the left side wall of the vehicle cabin in the coordinate system, denotes the abscissa of the receiving antenna. The n horizontal angle of arrival of the m-th scattering path and the elevation angle of arrival of the m-th scattering path are subject to a two-dimensional von Mises distribution with the probability density function

[0127] (13)

[0128] wherein, and both denote parameters characterizing the distribution density of the scatterers, and denote the mean horizontal angle of arrival and the mean elevation angle of arrival of the scattering paths, respectively, denotes the zeroth Bessel function.

[0129] The geometric relationship of the reflection components is shown in Figure 5 .

[0130] The l channel impulse response of the m-th reflection component can be represented as

[0131] (14)

[0132] wherein, denotes the impulse response of the m-th scattering component, l denotes the factor of the m-th reflection component, l denotes the imaginary unit, K denotes the time delay of the m-th reflection component, j denotes the propagation distance of the m-th reflection component, denotes the horizontal angle of arrival of the m-th reflection component, l denotes the elevation angle of arrival of the m-th reflection component, , l , Based on the geometric relationship of the reflection components, the following equations are used for the calculation: l l (15)

[0133] (15)

[0134] ​​​​​ (16)

[0135] (17)

[0136] wherein, , , , , denotes pq the distance of the two antenna elements on the reflection surface projection, and denote the distance between the transmitting antenna element p and the receiving antenna element q and the reflection surface, and the height of the transmitting antenna and the height of the receiving antenna, respectively, denotes the ordinate of the transmitting antenna, denotes the ordinate of the receiving antenna.

[0137] In this embodiment, the antenna model of the high-speed train carriage scene is constructed as follows: considering the narrow and closed characteristics of the carriage, it is more reasonable to deploy directional antennas inside the carriage for coverage. Next, the key parameters of the directional antenna are defined: the maximum gain of the antenna is 15 dBi, the horizontal beam width is 65°, and the vertical beam width is 30°. The parabolic model is used to approximate the radiation pattern, and the calculation formula is as follows:

[0138] (18)

[0139] (19)

[0140] wherein, denotes the gain of the antenna in the horizontal direction, denotes the gain of the antenna in the vertical direction, denotes the maximum gain of the antenna, and denote the horizontal angle and the horizontal beam width, respectively, and denote the vertical angle and the vertical beam width, respectively. The horizontal pattern and the vertical pattern of the directional antenna are shown in Figure 6 From the horizontal pattern and the vertical pattern of the antenna, the three-dimensional pattern of the antenna can be further derived, i.e. the antenna gain matrix in any spatial direction wherein represents the departure horizontal angle of the propagation component, represents the departure pitch angle of the propagation component.

[0141] In this embodiment, the powers of the direct component, reflected component, and scattered component are as follows:

[0142] The powers of the direct component, reflected component, and scattered component are all represented using their corresponding K-factors, denoted as [equations omitted for brevity]. , , Total K factor Defined as the ratio of the power of the non-scattering component to the power of the scattering component, the power of the scattering component is defined as 1, i.e. , Next, the power corresponding to the direct component, reflected component, and scattered component is calculated based on their respective power relationships.

[0143] Direct component power: The power of the direct component is defined as the K-factor of the direct component, i.e. , This represents the direct component power.

[0144] Reflection component power: The power of the reflection component is defined as the K-factor of the reflection component. The calculation method for the power of the l-th reflection component is as follows:

[0145] (20)

[0146] in, and Both represent the reflected component power. This represents the antenna gain matrix. and They represent the first l The angles of departure from the horizontal and the angles of departure from the pitch of the reflected components. and These represent the angles of departure from the horizontal and the angles of departure from the pitch of the direct component, respectively. and Representing the propagation distance of the direct trajectory and the first... l The propagation distance of the reflection path, The power representing the direct component, The power loss during reflection can be represented by the parallel reflection coefficient and the perpendicular reflection coefficient, and the calculation formula is shown below:

[0147] (twenty one)

[0148] (twenty two)

[0149] (twenty three)

[0150] in, and These represent the parallel reflection coefficient and the perpendicular reflection coefficient, respectively. incident angle of reflection path, ε0 represents the permittivity in vacuum, which is 8.854187817 x 10-12 farad-meter -1 , εr is the complex relative permittivity of the reflecting surface, which can be calculated by the following formula:

[0151] (24)

[0152] wherein, and respectively represent the real part of the permittivity and the conductivity of the reflecting surface material, j j represents the imaginary unit, f f represents the frequency of the electromagnetic wave, based on the modeling of the geometric mode, the reflection phenomenon occurs at the end wall and the side wall, wherein the material of the reflecting surface at the end wall is a smooth wooden surface, and the material of the reflecting surface at the side wall is glass or metal body, the electromagnetic parameters of the three possible reflecting surface materials are shown in Table 1, Table 1 is an electromagnetic parameter table of the reflecting surface material.

[0153] Table 1

[0154]

[0155] Scattering component power: the definition of the scattering component power is similar to that of the reflection component, and the total power of all scattering components is 1, i.e. , the n th scattering component is calculated as follows:

[0156] (25)

[0157] wherein, G represents the gain matrix of the antenna, , and n respectively represent the departure horizontal angle and the departure elevation angle of the th scattering component, and respectively represent the departure horizontal angle and the departure elevation angle of the direct component, and pq respectively represent the propagation distance of the direct path between the antenna elements and the propagation distance of the n th scattering path.

[0158] In this embodiment, the statistical characteristics of the high-speed train carriage scene channel are generated as follows:

[0159] (1) Time-varying space-time correlation function

[0160] The correlation characteristics of two arbitrary channel impulse responses can be represented as:

[0161] (26)

[0162] in, This represents the complex conjugate operation. Let be the expectation operator. Considering that the direct component, reflection component, and scattering component are independent, the time-varying space-time correlation function can be further expressed as:

[0163] (27)

[0164] In equation (27), when and When, the time-dependent function can be obtained, when and When the time-varying space-time correlation function is obtained, the spatial correlation function can be expressed as:

[0165] (28)

[0166] The time-varying spacetime correlation function of the reflection component can be expressed as:

[0167] (29)

[0168] in, The time-varying spacetime correlation function representing the reflection component. l Indicates the first l Bar reflection component, L This represents the total number of reflected components. Indicates the first l bar reflection component K factor, Antenna element pq Interval l The propagation distance of the reflection path, Antenna element Interval l The propagation distance of the reflection path, Indicates the first l The horizontal angle at which the reflected component arrives. Indicates the first l The pitch angle at which the reflected component arrives;

[0169] The time-varying space-time correlation function of the scattering component can be expressed as:

[0170] (30)

[0171] in, The time-varying space-time correlation function representing the scattering component, Antenna element pq Interval n The propagation distance of the scattering path, denotes the antenna element denotes the propagation distance of the n-th scattering path, denotes the propagation distance of the n-th scattering path, denotes the arrival horizontal angle and the arrival elevation angle of the n-th scattering path, n denotes the arrival horizontal angle and the arrival elevation angle of the n-th scattering path, denotes the function of denotes the function of denotes the function of denotes the integral of denotes the integral of denotes the inverse function of denotes the inverse function of denotes the cumulative distribution function of denotes the cumulative distribution function of denotes the arrival horizontal angle and the arrival elevation angle of the n-th scattering path. denotes the arrival horizontal angle and the arrival elevation angle of the n-th scattering path. denotes the arrival horizontal angle and the arrival elevation angle of the n-th scattering path. denotes the arrival horizontal angle and the arrival elevation angle of the n-th scattering path. n

[0172] (30)

[0173] (31)

[0174] denotes the inverse function of denotes the inverse function of denotes the cumulative distribution function of denotes the cumulative distribution function of denotes the cumulative distribution function of denotes the cumulative distribution function of denotes the cumulative distribution function of denotes the cumulative distribution function of denotes the cumulative distribution function of

[0175] (2) Root mean square delay spread

[0176] Root mean square delay spread (RMS Delay Spread) is used to describe the dispersion characteristics of multipath signals in the delay domain, which can be calculated by the following formula:

[0177] (32)

[0178] denotes the inverse function of denotes the inverse function of ​​​​respectively represent the power and delay of the k-th component.

[0179] In this embodiment, the following verifies and analyzes the high-speed train carriage scene channel model.

[0180] In order to verify the accuracy of the proposed model, the three-dimensional scene of the high-speed train carriage is modeled, and the simulation is performed using the ray tracing technology. After processing the simulation results, the root mean square delay spread is obtained. The results are compared with the root mean square delay spread calculated in formula (32) and the root mean square delay spread of the 3GPP standard model, and the results are shown in Figure 7 The results in the figure show that there is a significant difference between the 3GPP standard model and the ray tracing results, which indicates that the existing standard channel model is difficult to accurately represent the channel characteristics of the high-speed train carriage scene. It should be particularly pointed out that when considering the influence of the reflection component (REF), the GBSM modeling results and the ray tracing data show better consistency, which not only verifies the accuracy of the model, but also proves the necessity of considering the reflection component in the carriage channel modeling.

[0181] Figure 8 、 Figure 9 and Figure 10 respectively show the absolute values of the time correlation functions of different propagation components. Assuming that the receiving antenna moves towards the transmitting antenna at a speed of 2m / s: when there is only a scattering component, the time correlation of each receiving position quickly decays and eventually stabilizes at about 0.1; when there is a direct component, the time correlation briefly decreases and stabilizes at about 0.9; when there is a reflection component, all receiving positions exhibit a sustained decay characteristic, and the closer the receiving end to the transformer antenna, the lower the time correlation, which indicates that the reflection component can effectively reduce the time correlation of the receiving antenna.

[0182] Figure 11 、 Figure 12 and Figure 13 respectively show the absolute value variation of the spatial correlation function of different propagation components. The experimental results show that: when the receiving end only has a scattering component, the spatial correlation continuously decays with the increase of the receiving antenna (Rx) spacing; when there is a direct component, the spatial correlation always fluctuates at a high level of 0.8-0.9; when the reflection component is introduced, the spatial correlation presents a non-monotonic characteristic of first decreasing and then increasing, and the minimum value 0.1 appears when the receiving antenna spacing reaches about 0.3 meters. These data confirm that the reflection component can significantly reduce the spatial correlation of different receiving positions, and can reduce the correlation to about 0.1 under the condition of optimal antenna spacing, thereby greatly improving the channel capacity of the MIMO system.

[0183] To sum up, the application establishes a GBSM channel model suitable for a high-speed train carriage environment; the application models a directional antenna for coverage according to the characteristics of a closed and narrow carriage scene, so that the model is closer to an actual application scene; the application considers specific conditions inside the carriage, introduces reflection components under different conditions in the channel model, and improves the accuracy of the model; the application considers possible motion conditions under the carriage scene, analyzes channel characteristics inside the carriage under time-varying conditions; and the application analyzes small-scale characteristics such as time correlation and space correlation inside the carriage, and supplements the blank of existing research.

Claims

1. A method for modeling the channel inside a high-speed train carriage, characterized in that, Includes the following steps: Model the geometric model of the high-speed train carriage scene; Based on a geometric model, the channel impulse response in a high-speed train carriage scenario is generated. Modeling a directional antenna model for a high-speed train carriage scenario; Based on the modeling results of the directional antenna model of the high-speed train carriage scene and the generated channel impulse response, the direct component power, reflected component power and scattered component power are obtained. The expression for the direct-emission component power is as follows: in, Indicates the direct component power; The K-factor representing the direct component; The expression for the power of the reflected component is as follows: in, and Both represent the reflected component power. This represents the antenna gain matrix. and They represent the first l The angle of departure from the horizontal and the angle of departure from the pitch of the reflection path. and These represent the angles of departure from the horizontal and the angles of departure from the pitch of the direct component, respectively. and Representing the propagation distance of the direct trajectory and the first... l The propagation distance of the reflection path, Indicates the direct component power. This represents the power loss during the reflection process. Calculated using the following formula: in, and These represent the parallel reflection coefficient and the perpendicular reflection coefficient, respectively. The angle of incidence represents the reflection path. Represents the vacuum dielectric constant. The complex relative permittivity of the reflective medium surface is represented by the following: and Let represent the real part of the dielectric constant and the conductivity of the reflective surface material, respectively. j Represents the imaginary unit. f Indicates the frequency of electromagnetic waves; The expression for the power of the scattering component is as follows: in, Represents the power of the scattered component. and These represent the angles of departure from the horizontal and the angles of departure from the pitch of the nth scattering path, respectively. and These represent the angles of departure from the horizontal and the angles of departure from the pitch of the direct component, respectively. and Representing antenna elements pq The propagation distance of the direct trajectory and the first n The propagation distance of the scattering path; Based on the obtained direct component power, reflected component power, and scattered component power, the channel statistical characteristics of the high-speed train carriage scene are generated, and the channel modeling of the high-speed train carriage is completed.

2. The modeling method for the in-car passageway of a high-speed train according to claim 1, characterized in that, The expression for the channel impulse response is as follows: in, This represents the channel impulse response between any two antenna elements of the transmitter and receiver. , and These represent the impact responses of the direct component, the scattered component, and the reflected component, respectively. Channel response of direct component Represented as: in, and Let K-factors be the total K-factor and the K-factors of the direct component, respectively. j Represents the imaginary unit. Indicates the maximum Doppler frequency shift. t Indicates time, Indicates the wavelength of the signal. and Let represent the cosine values ​​of the horizontal angle and the pitch angle of the direct trajectory, respectively. Indicates the propagation delay of the direct path. Indicates the time delay unknown. ( ) represents a function of time delay. Antenna element pq The propagation distance of the direct beam. Represented as: in, and These represent the coordinates of the transmitter and receiver, respectively. and These represent the number of antenna elements in the transmitting antenna and the number of antenna elements in the receiving antenna, respectively. and They represent the first p The first transmitting antenna element and the first q One receiving antenna unit, and These represent the spacing between antenna elements of the transmitting antenna and the spacing between antenna elements of the receiving antenna, respectively. and These represent the tilt angles of the transmitting and receiving antennas, respectively. and The x and y coordinates of the receiving antenna element are represented. and Represents the x and y coordinates of the transmitting antenna element; Channel impulse response of scattering components Represented as: Where N represents the total number of scattering paths, Indicates the first n The power of the scattering path, Indicates the first n The random phase variation of the scattering path follows a certain order. The normal distribution and They represent the first n The cosine values ​​of the horizontal and vertical angles of arrival of the scattered path. Indicates the first n The time delay of the scattering path, Indicates the first n The propagation distance of the scattering path, Represented as: in, Indicates the transmitting antenna number p Unit The distance to the scatterer that produces the nth scattering path. This indicates the scatterer that generates the nth scattering path to the receiving antenna. q The distance between antenna elements , , , They represent the first n The starting horizontal angle, starting pitch angle, arrival horizontal angle, and arrival pitch angle of the scattering path. and Let represent the distances from the scatterer generating the nth scattering path to the transmitting antenna and the distances from the scatterer generating the nth scattering path to the receiving antenna, respectively. and Represented as: in, , , This represents the coordinates of the scatterer that produces the nth scattering path. and We obtain it from the following formula: in, This represents a parameter related to the location of the scatterer, when the scatterer is located on the top of the carriage and the left and right side walls, respectively. Represented as: in, Indicates the height of the car roof. Indicates the height of the receiving antenna. This indicates the positions of the left and right side walls of the carriage in the coordinate system. The x-coordinate of the receiving antenna; the first... n Horizontal angle of arrival of the scattering path With the pitch angle reached It follows a two-dimensional von Mises distribution, and its probability density function is... Represented as: in, and Both represent parameters that characterize the distribution density of the scatterer. and These represent the average horizontal angle of arrival and the average vertical angle of arrival of the scattered path, respectively. Represents the zeroth-order Bessel function; No. l Channel impulse response of a single reflection path Represented as: in, Indicates the first l Impact response of a single reflector path Indicates the first l The reflection path K factor, Indicates the first l The time delay of the reflection path, Indicates the first l The propagation distance of the reflection path, Indicates the first l The cosine of the horizontal angle at which the reflection path reaches the target. Indicates the first l The cosine of the pitch angle at which the reflection path arrives. , , Based on the geometric relationship of the reflection path, it is calculated using the following formula: in, , , , , express pq The distance between the two antenna elements projected onto the reflector surface. Indicates transmitting antenna element p The distance between the reflective surface and the reflective surface. Indicates receiving antenna unit q The distance between the reflective surface and the reflective surface. and The heights of the transmitting antenna and the receiving antenna, respectively. The vertical coordinate of the transmitting antenna is represented. This represents the vertical coordinate of the receiving antenna.

3. The modeling method for the in-car passageway of a high-speed train according to claim 1, characterized in that, The channel statistical characteristics of the high-speed train carriage 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.

4. The modeling method for the in-car passage of a high-speed train according to claim 3, characterized in that, The expression for the time-varying space-time correlation function of the direct component is as follows: in, The time-varying spacetime correlation function representing the direct component, Indicates time, Indicates time interval, and This indicates the antenna element spacing between the transmitting and receiving antennas. and Let K-factors be the total K-factor and the K-factors of the direct component, respectively. j Represents the imaginary unit. Antenna element pq The propagation distance of the direct beam. Antenna element The propagation distance of the direct beam. Indicates the wavelength of the signal. Indicates the maximum Doppler frequency shift. and These represent the cosine values ​​of the horizontal angle and the pitch angle of the direct trajectory, respectively. The expression for the time-varying space-time correlation function of the reflection component is as follows: in, The time-varying spacetime correlation function representing the reflection component. l Indicates the first l Reflection path, L This represents the total number of reflection paths. Indicates the first l The reflection path K factor, Indicates the first l The cosine of the horizontal angle at which the reflection path reaches the target. Indicates the first l The cosine of the pitch angle at which the reflection path arrives; The expression for the time-varying space-time correlation function of the scattering component is as follows: in, The time-varying space-time correlation function representing the scattering component, Antenna element pq Interval n The propagation distance of the scattering path, Antenna element The propagation distance of the nth scattering path. and They represent the first n The cosine values ​​of the horizontal and vertical angles of arrival of the scattered path. Represents the probability density function. Indicates to and The points, and They represent and inverse function, and They represent and The cumulative distribution function, and They represent the first n The horizontal and vertical angles of arrival of the scattering path.

5. The modeling method for the in-car channel of a high-speed train according to claim 3, characterized in that, The expression for the diffusion characteristic is as follows: in, This represents the dispersion characteristics of multipath signals in the time delay domain. and They represent the first k Power and time delay of the component.

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