A feedback ray tracing material parameter correction method

Abstract

The application discloses a feedback type ray tracking material parameter correction method, which comprises the following steps: through an existing material electromagnetic parameter library, wireless propagation simulation calculation is carried out on a high-precision three-dimensional map by using a ray tracking technology, and simulation is carried out to obtain received electric field intensity E S of each train running point and corresponding geographical position information of the point; received electric field intensity E T of a current position is obtained by a train signal receiver in an actual train operation process, and E T is saved in a channel database of a corresponding running position of the train; and received electric field intensity E S of each observation point obtained by simulation and received electric field intensity E T are used to correct each material electromagnetic parameter in a ray tracking material parameter library. According to the application, the description precision of the ray tracking calculation on the multipath effect of the wireless propagation in the environment can be improved by adjusting the ray electromagnetic parameters, the change of the railway environment is fed back in time, and more time-effective ray tracking calculation and channel modeling results can be obtained.

Description

Technical Field

[0001] This invention relates to the field of communications, and in particular to a feedback-based ray tracing method for correcting material parameters. Background Technology

[0002] Currently, domestic railway wireless networks are mainly used to support the CTCS-3 level train control system, transmitting safety-related information from trains to ground equipment. This makes wireless communication networks crucial in high-speed railway control. However, due to the complexity of rail transit scenarios, the resulting multipath effect of received signals causes the channel to change rapidly over time, potentially affecting the transmitted train control signals. Therefore, it is necessary to utilize ray tracing to accurately predict the channel and simulate the multipath propagation of radio electromagnetic waves, thereby assisting in the design of the wireless system.

[0003] Ray tracing technology primarily simulates and calculates all possible ray paths between transmitting and receiving antennas, enabling accurate prediction of radio electromagnetic wave multipath propagation. However, the implementation of ray tracing technology is highly dependent on scene information, especially accurate scene models and model parameters. Scene models can be obtained through various terrain survey techniques or manual modeling; however, model parameters, particularly the material electromagnetic parameters within the model, lack an effective method for measurement during the deployment planning of wireless network base stations, thus affecting the accuracy of field strength predictions using the aforementioned field strength prediction models. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a feedback-based ray tracing material parameter correction method that overcomes or at least partially solves the above problems.

[0005] To address the aforementioned technical problems, the embodiments of this application disclose the following technical solutions:

[0006] A feedback-based ray tracing material parameter correction method includes:

[0007] S100. Obtain a high-precision 3D map model of the entire target railway line, and set the base station antenna information for the entire railway line. Using the existing material electromagnetic parameter library, perform simulation calculations using ray tracing technology to obtain the received electric field intensity E at each observation point. S and the corresponding geographical location information;

[0008] S200. When the train arrives at each observation point, it acquires the geographical location information of the current observation point and obtains the current received electric field strength E through the train signal receiver. T and E T The channel database is stored at the corresponding running position of the train;

[0009] S300. When a train arrives at a station or enters a depot for maintenance, the E data stored in the channel database will be transferred. T Extract the data and use simulation to obtain the received electric field intensity E at each observation point. S and the received electric field strength E T Correct the electromagnetic parameters of each material in the ray tracing model;

[0010] S400. After all categories of materials have been calibrated, the material electromagnetic parameter library is updated. When wireless network planning needs to be re-executed, the updated material electromagnetic parameter library is directly called for simulation prediction.

[0011] Furthermore, in S100, the received electric field intensity Es is coherently superimposed from all ray results obtained at a certain observation point during the simulation, and its calculation formula is as follows:

[0012]

[0013] in, η is the receiving antenna gain, η0 is the characteristic impedance of air, λ is the radio wave operating frequency, and θ is the oscillating frequency. i and These are the azimuth and elevation angles of the signal received by the receiving antenna, E i N is the electric field of the wireless signal at the receiving antenna for each multipath propagation component. rays This indicates all types of ray results obtained from the observation point.

[0014] Furthermore, in S100, the existing material electromagnetic parameter library includes electromagnetic parameters for seven types of materials: vegetation, concrete buildings, soil, water surfaces, slope protection, metals, and air.

[0015] Furthermore, in S200, the geographical location information of the observation point can be determined by the relative position of the transponder between the train and the ground base station. The specific method is as follows: when the train reaches the corresponding observation point, it sends its ID to the train through the transponder set on the ground base station. At the same time, the relative position between the train and the ground base station is measured using the wheel-rail distance measuring instrument set on the train. Based on the transponder ID and the relative position, the current position P1 of the train is determined. Wherein, P1 = transponder ID + relative distance D between the train and the ground base station. The distance D is a fixed value because the trajectory of the rail transit train is fixed, and the distance D between the base stations of its communication network is also fixed.

[0016] Furthermore, in S100, the existing material electromagnetic parameter library includes electromagnetic parameters for seven types of materials: vegetation, concrete buildings, soil, water surfaces, slope protection, metals, and air.

[0017] Furthermore, in S300, the methods for correcting the electromagnetic parameters of various materials in the ray tracing model include:

[0018] S301. Select the set of all observation points in the ray tracing simulation that only exhibit direct propagation;

[0019] S302. Calculate the received electric field strength E at the selected observation point using simulation. S and the actual received electric field strength E T The principle of minimizing the mean square error is used to optimize and correct the air electromagnetic parameters in the model;

[0020] S303. After correcting the air electromagnetic parameters in the model, recalculate the simulated received electric field intensity E along the entire line using ray tracing. S' And re-establish its mapping with positional relationships;

[0021] S304. Select the set of all observation points that have only one reflection or direct light plus one reflection propagation, and classify them according to the type of reflecting material;

[0022] S305. For different sets of observation points reflecting different materials, simulate the received electric field intensity E at all selected observation points within each set. S' and the actual received electric field strength E T The principle of minimizing the mean square error is adopted to optimize each material individually, correct the electromagnetic parameters of all types of materials respectively, and update the material parameter library.

[0023] Furthermore, when the ray tracing simulation involves only a set of observation points with direct propagation, the electric field Ei of each multipath propagation component at the receiving antenna is calculated based on free-space propagation. The specific calculation formula is as follows:

[0024]

[0025] In the formula, E0 is the transmitted signal strength, and g T Let be the transmit antenna gain, j be the imaginary number, ω be the radio signal carrier frequency, and r be the propagation distance; k be the wave vector, which is determined by the complex permittivity of air; where, ε is the permittivity, and μ is the permeability.

[0026] Furthermore, the principle of minimizing the mean square error is used to optimize and correct the electromagnetic parameters of the air in the model. Specifically, the electromagnetic parameters of the air are adjusted so that the electromagnetic parameters of all selected observation points E within the set are optimized. S -E T Minimize the root mean square error; assuming there are n selected observation points in the set, by making... The minimum value is obtained, and the adjusted air electromagnetic constant is stored in the material parameter library.

[0027] Furthermore, in S304, all observation points that have only one reflection or direct light plus one reflection propagation are selected and classified according to the type of reflecting material. The type of reflecting material is the material other than air in the existing material electromagnetic parameter library, specifically including: vegetation, concrete buildings, soil, water surface, slope protection and metal.

[0028] Furthermore, in S305, when the first-order reflection model element corresponds to the set of observation points for vegetation, the complex permittivity corresponding to the vegetation is adjusted so that Es-E in the selected set of observation points is equal to... r’ The root mean square difference is minimized, and the adjusted complex dielectric constant of the vegetation material is obtained and stored in the material parameter library.

[0029] Furthermore, when a certain material cannot find a corresponding observation point for receiving signals from first-order reflection or direct light plus first-order reflection, the material parameters can be corrected by first adjusting the parameters of other materials and then finding a higher-order reflection.

[0030] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0031] This invention overcomes the problem of real-time updates to material parameters in conventional ray-tracing wireless coverage prediction and channel modeling. Environmental parameters change over time; different seasons and weather conditions can affect calculation results. In applications requiring high accuracy in channel modeling, such as channel equalization, inaccuracies in channel modeling can significantly impact the effectiveness of backend signal processing.

[0032] This invention utilizes ray tracing technology in conjunction with a high-precision 3D environment model to accurately describe the multipath effects of wireless propagation in the environment, thereby obtaining more accurate channel modeling results. Simultaneously, during train operation, the accuracy of the ray tracing algorithm is improved by receiving actual signals and correcting material parameters. By adjusting the electromagnetic parameters of the rays, changes in environmental parameters can be promptly fed back through parameter adjustments, resulting in more timely ray tracing calculations and channel modeling results.

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0035] Figure 1 This is a flowchart of a feedback-based ray tracing material parameter correction method in Embodiment 1 of the present invention;

[0036] Figure 2 This is a flowchart of the method for correcting the electromagnetic parameters of various materials in the ray tracing model in Embodiment 1 of the present invention. Detailed Implementation

[0037] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0038] To address the problems existing in the prior art, embodiments of the present invention provide a feedback-based ray tracing material parameter correction method.

[0039] Example 1

[0040] This embodiment discloses a feedback-based ray tracing material parameter correction method, such as... Figure 1 ,include:

[0041] S100. Obtain a high-precision 3D map model of the entire target railway line, and set the base station antenna information for the entire railway line. Using the existing material electromagnetic parameter library, perform simulation calculations using ray tracing technology to obtain the received electric field intensity E at each observation point. S and the corresponding geographical location information;

[0042] Specifically, in this embodiment, a high-precision 3D environment model of the entire target railway line is obtained through high-precision 3D map processing technologies such as oblique photography and laser point cloud. The relevant design content of the wireless communication system is then configured on the environment model, including setting the locations of base stations (repeaters) along the entire railway line, setting antenna height, azimuth angle, elevation angle, and antenna lobe diagram. The locations of all observation points along the railway line also need to be set. Using an existing material electromagnetic parameter library, ray tracing technology is used for simulation calculations, considering the propagation of rays in the environment, including direct, transmitted, reflected, diffracted, and scattered rays, to obtain the received electric field intensity Es at each point along the entire line and the corresponding geographical location information of that point.

[0043] In S100 of this embodiment, the received electric field intensity Es is coherently superimposed with all the ray results obtained from a certain observation point during the simulation process. The calculation formula is as follows:

[0044]

[0045] in, η is the receiving antenna gain, η0 is the characteristic impedance of air, λ is the radio wave operating frequency, and θ is the oscillating frequency. i and These are the azimuth and elevation angles of the signal received by the receiving antenna, E i N is the electric field of the wireless signal at the receiving antenna for each multipath propagation component. rays This indicates all types of ray results obtained from the observation point.

[0046] In S100 of this embodiment, the existing material electromagnetic parameter library includes electromagnetic parameters for seven types of materials: vegetation, concrete buildings, soil, water surfaces, slope protection, metal, and air. Specifically, the initial material electromagnetic parameter library needs to cover the main materials in the railway environment. The determination of the materials depends on the classification of map model materials by the environment model. Generally, railway environment materials can be divided into six categories: vegetation, concrete buildings, soil, water surfaces, slope protection, and metal. Adding the electromagnetic parameters for air, the material electromagnetic parameter library needs to store the electromagnetic parameters of these seven materials. This electromagnetic parameter is mainly the complex relative permittivity. The complex relative permittivity mainly affects the electric field E of the wireless signal at the receiving antenna for each multipath propagation component in the above formula. i Since the complex relative permittivity is an important parameter that needs to be considered in transmission, reflection and diffraction, more accurate electromagnetic parameters can ensure that the calculation of the electric field of the wireless signal of each multipath propagation component is more accurate in the ray tracing calculation, thereby improving the accuracy of ray tracing simulation calculation.

[0047] S200. When the train arrives at each observation point, it acquires the geographical location information of the current observation point and obtains the current received electric field strength E through the train signal receiver. T and E T The channel database is stored at the corresponding running position of the train;

[0048] In S200 of this embodiment, the geographical location information of the observation point can be determined by the relative position of the train and the transponder of the ground base station. The specific method is as follows: when the train runs to the corresponding observation point, it sends its ID to the train through the transponder set on the ground base station. At the same time, the relative position of the train and the ground base station is measured by the wheel-rail distance measuring instrument set on the train. Based on the transponder ID and the relative position, the current position P1 of the train is determined. Wherein, P1 = transponder ID + relative distance D between the train and the ground base station. The distance D is a fixed value because the trajectory of the rail transit train is fixed and the distance D between the base stations of its communication network is also fixed.

[0049] S300. When a train arrives at a station or enters a depot for maintenance, the E data stored in the channel database will be transferred. T Extract the data and use simulation to obtain the received electric field intensity E at each observation point. S and the received electric field strength E T Correct the electromagnetic parameters of each material in the ray tracing model;

[0050] In this embodiment S300, the method for correcting the electromagnetic parameters of each material in the ray tracing model includes:

[0051] S301. Select the set of all observation points in the ray tracing simulation that only exhibit direct propagation;

[0052] S302. Calculate the received electric field strength E at the selected observation point using simulation. S and the actual received electric field strength E T The principle of minimizing the mean square error is used to optimize and correct the air electromagnetic parameters in the model;

[0053] S303. After correcting the air electromagnetic parameters in the model, recalculate the simulated received electric field intensity E along the entire line using ray tracing. S' And re-establish its mapping with positional relationships;

[0054] S304. Select the set of all observation points that have only one reflection or direct light plus one reflection propagation, and classify them according to the type of reflecting material;

[0055] S305. For different sets of observation points reflecting different materials, simulate the received electric field intensity E at all selected observation points within each set. S' and the actual received electric field strength E T The principle of minimizing the mean square error is adopted to optimize each material individually, correct the electromagnetic parameters of all types of materials respectively, and update the material parameter library.

[0056] Specifically, when a train arrives at a station or enters a depot for maintenance, E2 stored in the channel database is retrieved. By comparing the difference between the simulated received electric field strength E1 and the actual received electric field strength E2 at each point, the electromagnetic parameters of the ray material in each part of the ray tracing model are corrected.

[0057] The parameter library mainly contains the relative complex permittivity of seven materials: air, vegetation, concrete buildings, soil, water surface, slope protection, and metal. Considering that air is a factor that needs to be considered as a propagation medium regardless of the propagation path, the parameters of air need to be corrected first.

[0058] The first step in performing air parameter correction is to identify and aggregate all observation points in the environment where only direct sunlight signals are present. These observation points are often found in railway areas with flat terrain and transmitting antennas above the track surface, and can be found in most open sections of railways.

[0059] When the ray tracing simulation uses only observation points with direct propagation, the electric field Ei of the wireless signal for each multipath propagation component at the receiving antenna is calculated based on free-space propagation. The specific calculation formula is as follows:

[0060]

[0061] In the formula, E0 is the transmitted signal strength, g T Let be the transmit antenna gain, j be the imaginary number, ω be the radio signal carrier frequency, and r be the propagation distance; k be the wave vector, which is determined by the complex permittivity of air; where, ε is the dielectric constant, and μ is the permeability. Although the dielectric constant and permeability of air can usually be simplified to 1, impurities and moisture in the air can affect the dielectric constant, making it not a completely real number, i.e., ε = ε' + iε". The magnitude of the imaginary part of the dielectric constant directly affects the real part of the received electric field strength, and the magnitude of the real part of the dielectric constant affects the phase of the propagating electric field. In a railway environment, the wireless propagation medium is mostly air. Even when encountering reflected or diffracted rays, the medium during the propagation process is still air. Therefore, correcting this parameter is a prerequisite for correcting all other parameters.

[0062] In this embodiment, the principle of minimizing the mean square error is used to optimize the air electromagnetic parameters in the correction model. The specific method is as follows:

[0063] By adjusting the electromagnetic parameters of the air, all selected observation points E within the set are made... S -E T Minimize the root mean square error; assuming there are n selected observation points in the set, by making... The minimum value is obtained, and the adjusted air electromagnetic constant is stored in the material parameter library.

[0064] After updating the air material parameters, the new material parameters are brought back into the ray tracing calculation to recalculate the received signal power across the entire line, obtaining the simulated received electric field strength E after the air material parameters have been corrected. S’ Select observation points that receive signals with only first-order reflection or only direct light plus first-order reflection. Classify all selected observation points according to the material type of the model element containing the reflection point. For example, find the set of observation points where the first-order reflection model element corresponds to vegetation. Adjust the complex permittivity corresponding to the vegetation to make E in the selected observation point set... T -E S The root mean square difference is minimized to obtain the adjusted complex dielectric constant of the vegetation material, which is then stored in the material parameter library.

[0065] In this embodiment, for first-order reflection or only direct incidence plus first-order reflection, after confirming the propagation path received at the observation point, the signal amplitudes of incident electromagnetic waves with different polarization directions before and after reflection on the surface of the three-dimensional model are calculated using the Fresnel reflection formula. The specific calculation formula is as follows:

[0066]

[0067]

[0068] In the formula, ε1 and ε2 are the relative complex permittivity of the materials on both sides of the reflecting interface, θ1 is the incident angle, and θ2 is the reflection angle. In the first-order reflection calculation, since the ray only undergoes one reflection during propagation and does not involve any diffraction or transmission, the incident medium at the reflecting interface is air, and the reflecting medium is the parameter of the model surface. Since the complex permittivity ε1 of air has been determined in step 13 above, the relative complex permittivity ε2 of the model surface material can be obtained by comparison calculation for each first-order reflection.

[0069] In some preferred embodiments, the above-described operations are performed on other materials in the material library to sequentially update the complex permittivity of the materials in the material parameter library. It should be noted that when a certain material cannot find a corresponding observation point for receiving signals with first-order reflection or direct + first-order reflection, the parameters of other materials can be adjusted first, and then the material parameters can be corrected by finding a higher-order reflection.

[0070] The reason why higher-order reflections are prioritized over lower-order reflections is that the computational cost of higher-order ray tracing calculations increases exponentially compared to lower-order calculations. Therefore, higher-order reflections are only used when lower-order calculations cannot confirm a certain material parameter. When using higher-order reflections, an upper limit on the calculation order must be set, such as finding a maximum of third-order reflections. If ray paths below third-order reflections cannot find the model surface corresponding to the material parameter, the material can be considered unimportant, and the parameter correction work for that material can be skipped.

[0071] S400. Once all material categories have been calibrated, the material electromagnetic parameter library is updated. When wireless network planning needs to be re-implemented, the updated material electromagnetic parameter library is directly called for simulation prediction. Specifically, once all material categories have been calibrated, the material electromagnetic parameter library is updated. Parameter calibration is performed periodically on the railway environment of a certain area. When wireless network planning needs to be re-implemented for that area, the timely material parameter library can be directly called for simulation prediction, improving the accuracy of the prediction results.

[0072] This embodiment discloses a feedback-based ray-tracing material parameter correction method, which overcomes the problem of real-time updates of material parameters in conventional ray-tracing wireless coverage prediction and channel modeling. Since environmental parameters change over time, different seasons and weather conditions can affect the calculation results. In applications such as channel equalization, where high accuracy in channel modeling is required, inaccuracies in channel modeling can significantly impact the effectiveness of backend signal processing.

[0073] This embodiment utilizes ray tracing technology in conjunction with a high-precision 3D environment model to accurately describe the multipath effects of wireless propagation in the environment, thereby obtaining more accurate channel modeling results. Simultaneously, during train operation, the accuracy of the ray tracing algorithm is improved by receiving actual signals and correcting material parameters. By adjusting the electromagnetic parameters of the rays, changes in environmental parameters can be promptly fed back through parameter adjustments, resulting in more timely ray tracing calculations and channel modeling results.

[0074] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0075] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0076] Those skilled in the art will also understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in alternative ways for each specific application; however, such implementation decisions should not be construed as departing from the scope of this disclosure.

[0077] The steps of the methods or algorithms described in conjunction with the embodiments herein can be directly embodied in hardware, software modules executed by a processor, or a combination thereof. The software modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can exist as discrete components in the user terminal.

[0078] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. This software code can be stored in memory units and executed by a processor. The memory units can be implemented within the processor or outside the processor; in the latter case, they are communicatively coupled to the processor via various means, as is well known in the art.

[0079] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A feedback-based ray tracing method for correcting material parameters, characterized in that, include: S100. Obtain a high-precision 3D map model of the entire target railway line, and set the base station antenna information for the entire railway line. Using the existing material electromagnetic parameter library, perform simulation calculations using ray tracing technology to obtain the received electric field intensity E at each observation point. S and the corresponding geographical location information; S200. When the train arrives at each observation point, it acquires the geographical location information of the current observation point and obtains the current received electric field strength E through the train signal receiver. T and E T The channel database is stored at the corresponding running position of the train; S300. When a train arrives at a station or enters a depot for maintenance, the E data stored in the channel database will be transferred. T Extract the data and use simulation to obtain the received electric field intensity E at each observation point. S and the received electric field strength E T Correct the electromagnetic parameters of each material in the ray tracing model; In S300, the methods for correcting the electromagnetic parameters of various materials in the ray tracing model include: S301. Select the set of all observation points in the ray tracing simulation that only exhibit direct propagation; S302. Calculate the received electric field strength E at the selected observation point using simulation. S and the actual received electric field strength E T The principle of minimizing the mean square error is used to optimize and correct the air electromagnetic parameters in the model; S303. After correcting the air electromagnetic parameters in the model, recalculate the simulated received electric field intensity E along the entire line using ray tracing. S' And re-establish its mapping with positional relationships; S304. Select the set of all observation points that have only one reflection or direct light plus one reflection propagation, and classify them according to the type of reflecting material; S305. For different sets of observation points reflecting different materials, simulate the received electric field intensity E at all selected observation points within each set. S' and the actual received electric field strength E T The principle of minimizing the mean square error is adopted to optimize each material individually, correct the electromagnetic parameters of all types of materials respectively, and update the material parameter library; S400. After all categories of materials have been calibrated, the material electromagnetic parameter library is updated. When wireless network planning needs to be re-executed, the updated material electromagnetic parameter library is directly called for simulation prediction.

2. The feedback-based ray tracing material parameter correction method as described in claim 1, characterized in that, In S100, the received electric field intensity Es is coherently superimposed from all ray results obtained at a certain observation point during the simulation. Its calculation formula is as follows: ； in, G ( θ i, φ i () is the receiving antenna gain. η 0 It is the characteristic impedance of air. λ It is the operating frequency of radio waves. θ i and φ i These are the azimuth and elevation angles of the signal received by the receiving antenna, respectively. E i It is the electric field of the wireless signal at the receiving antenna, representing the multipath propagation components. N rays This indicates all types of ray results obtained from the observation point.

3. The feedback-based ray tracing material parameter correction method as described in claim 1, characterized in that, In S100, the existing material electromagnetic parameter library includes electromagnetic parameters for seven types of materials: vegetation, concrete buildings, soil, water surfaces, slope protection, metals, and air.

4. The feedback-based ray tracing material parameter correction method as described in claim 1, characterized in that, In S200, the geographical location information of the observation point can be determined by the relative position of the train and the ground base station transponders. The specific method is as follows: when the train reaches the corresponding observation point, it sends its ID to the train through the transponder set on the ground base station. At the same time, the wheel-rail distance measuring instrument set on the train measures the relative position between the train and the ground base station. Based on the transponder ID and the relative position, the current position P1 of the train is determined. Wherein, P1 = transponder ID + relative distance D between the train and the ground base station. The distance D is a fixed value because the trajectory of the rail transit train is fixed, and the distance D between the base stations of its communication network is also fixed.

5. The feedback-based ray tracing material parameter correction method as described in claim 1, characterized in that, When the ray tracing simulation uses a set of observation points where only direct propagation exists, the electric field E of the wireless signal at the receiving antenna for each multipath propagation component is... i Based on free-space propagation calculations, the specific calculation formula is as follows: ； In the formula, E0 is the transmitted signal strength, and g T Let be the transmit antenna gain, j be the imaginary number, ω be the radio signal carrier frequency, t be the time variable parameter, and r be the propagation distance; k be the wave vector, which is determined by the complex permittivity of air; where, , is the dielectric constant, and μ is the magnetic permeability.

6. The feedback-based ray tracing material parameter correction method as described in claim 1, characterized in that, The principle of minimizing mean square error is used to optimize the air electromagnetic parameters in the correction model. The specific method is as follows: By adjusting the electromagnetic parameters of the air, all selected observation points E within the set are made... S -E T Minimize the root mean square error; assuming there are n selected observation points in the set, by making... The minimum value is obtained, and the adjusted air electromagnetic constant is stored in the material parameter library.

7. The feedback-based ray tracing material parameter correction method as described in claim 1, characterized in that, In S304, all observation points that have only one reflection or direct light plus one reflection propagation are selected and classified according to the type of reflecting material. The type of reflecting material is the material other than air in the existing material electromagnetic parameter library, specifically including: vegetation, concrete buildings, soil, water surface, slope protection and metal.

8. The feedback-based ray tracing material parameter correction method as described in claim 7, characterized in that, In S305, when the first-order reflection model element corresponds to the set of observation points for vegetation, the complex permittivity of the vegetation is adjusted so that Es-E in the selected set of observation points is equal to... r’ The root mean square difference is minimized, and the adjusted complex dielectric constant of the vegetation material is obtained and stored in the material parameter library.

9. The feedback-based ray tracing material parameter correction method as described in claim 1, characterized in that, When a certain material cannot find a corresponding observation point for receiving signals from first-order reflection or direct light plus first-order reflection, the material parameters are corrected by first adjusting the parameters of other materials and then finding a higher-order reflection.

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