Satellite-ground data transmission test method and system for railway low-orbit satellite integrated network

Abstract

The invention provides a satellite-ground data transmission test method and system for a railway low-orbit satellite integrated network, and belongs to the technical field of railway train satellite communication test equipment. The invention provides a set of complete satellite-to-ground data transmission test scheme for railway low-orbit satellites, a controllable and repeatable railway-satellite converged communication simulation environment is firstly constructed in a laboratory through a mode of combining semi-physical simulation and external field test, communication performance prediction and parameter optimization are performed in advance, and the communication performance is optimized; the simulation model is reversely corrected on the basis of actual measurement data feedback, so that closed-loop optimization of the test process is realized, the outfield test resource cost can be greatly reduced, and the accuracy of a test result can be improved; the outfield test scheme provided by the invention comprises a test index system with three levels of coverage performance, service quality and service bearing, can comprehensively evaluate the communication capability of the low-orbit satellite in the railway environment, and can help to promote the landing application of the satellite internet in the railway field.

Description

Technical Field

[0001] This invention relates to the technical field of satellite communication testing equipment for railway trains, and specifically to a satellite-to-ground data transmission testing method and system for integrated low-orbit satellite networks for railways. Background Technology

[0002] Dedicated mobile communication for railways is a crucial infrastructure and key technological equipment for the informatization, digitalization, and intelligentization of railways, playing a vital role in supporting railway operations, ensuring traffic safety, improving transportation efficiency, and enhancing maintenance levels. Currently, the widely used dedicated railway integrated digital mobile communication system (Global System for Mobile Communications – Railway, GSM-R) belongs to the second generation of mobile communication systems. It has limited bandwidth and low data rates, and the network's service capacity and capabilities are very limited. Communication equipment manufacturers are gradually reducing the production of related equipment, shifting their focus to providing technical services and existing spare parts. There is an urgent need to accelerate the deep integration of next-generation information technologies with railways, focusing on intelligent construction, intelligent equipment, and intelligent operation. This requires leveraging next-generation mobile communication technologies to empower intelligent high-speed rail, providing high-bandwidth, high-connectivity, low-latency, and highly reliable transmission channels to address the needs of enhanced mobile broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliable low-latency communication (uRLLC).

[0003] However, 5G-R-based intelligent high-speed rail mobile communication systems may face coverage difficulties in extreme environments due to base station damage or deployment challenges. Relying solely on traditional terrestrial cellular coverage methods will be insufficient to meet emergency rescue network needs during severe natural disasters such as floods, earthquakes, and mudslides. Furthermore, in areas without dedicated network coverage along railway lines, the secure and efficient transmission of train control and maintenance data requires robust information and communication technologies. Low-Earth orbit (LEO) satellites, unaffected by terrain and surface disasters, offer wide coverage, all-weather operation, high bandwidth, and low latency, making them the most effective solution for filling terrestrial network coverage gaps. Therefore, applying LEO satellite internet to intelligent high-speed rail holds immense potential and promise. Currently, research and verification of intelligent high-speed rail data backhaul technology based on LEO satellite internet, grounded in 5G-R, is of significant importance, addressing the communication service needs of intelligent high-speed rail in areas such as train control, operation and maintenance, management, and engineering construction.

[0004] Due to the significant differences in transmission characteristics between low-Earth orbit (LEO) satellite-to-ground links and terrestrial cellular links, testing the communication performance of railway satellite-to-ground links is a prerequisite and guarantee for the application of satellites in railways. However, LEO satellite communication has only gradually gained widespread attention in recent years, and the formulation of its communication standards and the deployment of communication systems are still incomplete. Furthermore, the rapid overhead movement of LEO satellites and the relatively small scale of domestic LEO constellations make LEO satellite testing quite difficult. In addition, the high speed of high-speed rail, forming a high-speed link between the transmitting and receiving ends of LEO satellites, poses an even greater challenge to conducting rapid, accurate, and efficient testing; currently, there is no comprehensive testing solution.

[0005] In summary, there are currently few domestic and international cases of applying satellite communication to the railway sector, and even fewer testing methods specifically for railway satellite applications. Existing cases mostly involve using high-orbit satellites for low-speed railway communication or utilizing satellites for railway positioning and navigation, such as the BeiDou Navigation Satellite System. These applications differ significantly from low-orbit satellite communication in terms of coverage, latency, link stability, and terminal complexity, and are far removed from the characteristics of the "low-orbit satellite + high-speed rail" scenario, making them difficult to directly apply. Existing railway satellite testing work mainly focuses on static or low-speed moving scenarios. For low-orbit satellite systems, their short zenith window time and high satellite movement speed, coupled with the high-speed relative motion between the satellite and the train in high-speed train operation scenarios, make link establishment and maintenance difficult, further shortening the testing window. Furthermore, traditional testing typically relies on actual train operation or prolonged occupation of railway resources for experiments, resulting in long testing cycles, high costs, low testing frequency, and poor repeatability, making it difficult to meet the needs of large-scale, multi-parameter, and multi-scenario testing. Summary of the Invention

[0006] The purpose of this invention is to provide a satellite-to-ground data transmission testing method and system for low-orbit satellite integrated networks for railways, so as to solve at least one of the technical problems existing in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a satellite-to-ground data transmission testing method for a low-orbit satellite integrated network for railways, comprising:

[0009] VTD is used to build a railway operating environment, including a basic railway environment, static scenes of buildings, base stations, and trackside equipment, and dynamic scenes of moving trains.

[0010] Railway operation data acquisition: In train simulation operation, the train position coordinates, coordinates and types of surrounding obstacles, and key train speed indicators are acquired in real time in different typical railway environments;

[0011] STK is used to build a satellite operation scenario, including constellation type, number of satellites, satellite orbit parameters and gateway station locations; railway operation data obtained from VTD is imported into STK to obtain key information about ground trains and realize the reproduction of the railway operation environment in STK;

[0012] In STK, satellite scenarios are run, and at fixed sampling intervals, the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage are calculated based on ephemeris information and train operation information.

[0013] The acquired signal fading data, power data, and frequency offset data are added to the ideal waveform file to create a simulation waveform file within a certain simulation time.

[0014] The prepared simulation waveform file is analyzed to display the RSRP, RSSI, and SNR information of the received data packets in real time, thereby realizing the analysis of key communication indicators of railway trains.

[0015] As a further limitation of the first aspect of the invention, a travel path is set for the train, and the train will travel according to the prescribed route. At the same time, the train perceives the surrounding environment by analyzing and processing sensor data, and makes decisions based on this.

[0016] As a further limitation of the first aspect of the present invention, the simulated waveform file corresponds to the data packet arriving at the train receiving end, and is used to represent the changes in the signal when it arrives at the train receiving end from the satellite transmitter in real satellite-to-ground data transmission.

[0017] As a further limitation of the first aspect of the present invention, the method for calculating Doppler frequency offset at different vehicle speeds is shown in the following formula:

[0018] ;

[0019] in The Doppler frequency shift is caused by satellite motion. For vehicle speed, Original signal carrier frequency, At the speed of light, The angle between the train's direction of movement and the satellite-to-ground link;

[0020] in, ;

[0021] in For the satellite's angular velocity, satisfying ,in The gravitational constant of Earth, For the Earth's radius, The angle of elevation.

[0022] As a further limitation of the first aspect of the present invention, the determination of link connectivity can be based on a minimum elevation angle threshold for the satellite-to-ground link. And compare the real-time elevation angle of the satellite-to-ground link obtained in STK. and ,when ≥ When the signal is active, the link is connected; otherwise, the link is disconnected. For calculating signal coverage, a minimum signal-to-noise ratio threshold is set for the ground receiver. In STK, uniform sampling is performed within a certain area of ​​the ground surface to obtain the real-time signal-to-noise ratio of each sampling point. Search near The locations of these locations, and the area enclosed by these locations, constitute the signal coverage area.

[0023] As a further limitation of the first aspect of the present invention, regarding signal coverage performance, an RSRP threshold that meets the minimum requirements for train communication is set. The RSRP obtained by the host computer software is compared with the threshold, and the length of the coverage area exceeding the RSRP threshold is statistically analyzed to assess signal coverage performance. Regarding signal holding performance, the changes in RSRP and SNR over time are analyzed. The proportion of time during which both RSRP and SNR are greater than the threshold is statistically analyzed to assess signal holding performance. Regarding communication capacity, it is calculated using Shannon's formula and the SNR obtained by the host computer software. Regarding latency, it is obtained by dividing the propagation distance of the satellite-to-ground link obtained in STK by the speed of light. Regarding packet loss rate, it is calculated by statistically analyzing the total number of data packets transmitted by the integrated testing instrument. And the total number of data packets successfully received by the host computer. ,pass get.

[0024] Secondly, the present invention provides a satellite-to-ground data transmission test system for integrated low-orbit satellite networks for railways, comprising:

[0025] The first module is used to build a railway operating environment using VTD, including a basic railway environment, static scenes of buildings, base stations, trackside equipment, and dynamic scenes of moving trains.

[0026] The first acquisition module is used to acquire railway operation data: during train simulation operation, it acquires the train position coordinates, coordinates and types of surrounding obstacles, and key indicators of train speed in real time in different typical railway environments;

[0027] The second module is used to build satellite operation scenarios using STK, including constellation type, number of satellites, satellite orbit parameters, and gateway station locations; it imports railway operation data obtained from VTD into STK to obtain key information about ground trains and realize the reproduction of the railway operation environment in STK;

[0028] The calculation module is used to run satellite scenarios in STK. At fixed sampling intervals, it calculates the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage indicators based on ephemeris information and train operation information.

[0029] The analysis module is used to add key data such as acquired signal fading data, power data, and frequency offset data to an ideal waveform file, thereby creating a simulation waveform file within a certain simulation time. The module then analyzes the created simulation waveform file and displays the RSRP, RSSI, and SNR information of the received data packets in real time, enabling the analysis of key communication indicators for railway trains.

[0030] Thirdly, the present invention provides a non-transitory computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the satellite-to-ground data transmission test method for railway low-orbit satellite integrated network as described in the first aspect.

[0031] Fourthly, the present invention provides a computer device including a memory and a processor, wherein the processor and the memory communicate with each other, the memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to execute the satellite-to-ground data transmission test method for railway low-orbit satellite integrated network as described in the first aspect.

[0032] Fifthly, the present invention provides an electronic device, comprising: a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to cause the electronic device to execute instructions for implementing the satellite-to-ground data transmission test method for a low-orbit satellite integrated network for railways as described in the first aspect.

[0033] Terminology Explanation: 1) Low Earth Orbit (LEO) satellite: refers to satellites with an orbital altitude of 500-2000 km above the Earth's surface. Unlike medium and high Earth Orbit (MEO) satellites, LEO satellites offer advantages such as low latency and high bandwidth transmission. 2) Railway satellite-to-ground data communication: refers to a method of providing communication for railways using LEO satellites as relays, which can complement the advantages of railway terrestrial private networks. 3) Network coverage performance: refers to the signal coverage capability of a satellite communication system within a specified area, usually characterized by indicators such as signal strength and coverage rate. 4) Quality of service (QoS): refers to the quality of service provided by LEO satellites to railway users and services, usually characterized by indicators such as access performance, mobility performance, and channel maintenance performance. 5) Service carrying capacity: refers to the ability of LEO satellites to carry critical railway services, usually characterized by indicators such as transmission latency and packet loss rate.

[0034] The beneficial effects of this invention are as follows: Addressing the problems of high testing costs, short testing windows, difficulty in reproducing data, and limited scenario scope in traditional satellite testing, which are ill-suited to the high-speed, frequently switching low-Earth orbit (LEO) satellite railway communication scenarios, this invention proposes a complete satellite-to-ground data transmission testing scheme specifically for LEO satellites used in railways. By combining "hybrid hardware simulation + field testing," a controllable and repeatable railway-satellite integrated communication simulation environment is first constructed in the laboratory to predict communication performance and optimize parameters in advance. Then, the simulation model is corrected based on feedback from measured data, thereby achieving closed-loop optimization of the testing process. This not only significantly reduces the resource costs of field testing but also helps improve the accuracy of test results. The proposed field testing scheme includes a three-tiered testing index system encompassing coverage performance, service quality, and service carrying capacity, comprehensively evaluating the communication capabilities of LEO satellites in a railway environment and contributing to the promotion of satellite internet applications in the railway sector.

[0035] The advantages of additional aspects of the invention will be set forth more clearly in the following description or will be learned by practice of the invention. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of the railway satellite-to-ground data communication performance testing method according to an embodiment of the present invention.

[0038] Figure 2 This is a diagram of the hardware-in-the-loop simulation system architecture described in an embodiment of the present invention.

[0039] Figure 3 This is a test architecture diagram for train receiving satellite data according to an embodiment of the present invention. Detailed Implementation

[0040] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0041] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as here.

[0043] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0044] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0045] To facilitate understanding of the present invention, the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0046] Those skilled in the art should understand that the accompanying drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0047] This invention proposes a testing method for satellite-to-ground data transmission in integrated low-Earth orbit (LEO) satellite networks for railways. Dedicated testing equipment is designed to test indicators such as satellite network coverage, satellite network service quality (QoS), and the performance of satellite communication in carrying railway application services. Satellite communication performance is tested and evaluated at three levels: physical signal, QoS, and service function. Physical signal testing primarily assesses coverage performance in different railway areas; QoS mainly tests the performance of the satellite communication network itself in providing services, including access performance, mobility performance, and channel maintenance performance; and service function testing assesses key communication indicators such as bandwidth, latency, and packet loss rate of satellite communication carrying railway application services under operational conditions. The method proposed in this invention enables effective testing of key indicators of LEO satellite communication for railways, promoting the application of LEO satellite communication in the railway sector. This invention also proposes a simulation and testing method for typical application scenarios of "LEO satellite + high-speed railway," aiming to improve testing efficiency, reduce costs, and enhance test repeatability and coverage. Based on the typical application scenario of "low-Earth orbit satellite + high-speed rail," this study employs a combination of laboratory hardware-in-the-loop simulation and field testing. First, a railway-satellite integrated communication simulation test platform is built in the laboratory. Professional software such as STK and VTD are used to conduct high-frequency, high-fidelity, and low-cost simulation tests of railway operations, rapidly verifying the system design and parameter configuration, effectively reducing the blind spots and resource waste of field testing. Subsequently, field testing is conducted to verify the simulation platform model in a real railway satellite environment. Real-world data is used to update the simulation platform, achieving a cyclical improvement between internal and external testing, enhancing testing efficiency and accuracy, and reducing the human and material costs required for testing.

[0048] This invention proposes a testing scheme combining in-laboratory hardware-in-the-loop (HIL) simulation and field testing for testing satellite-to-ground data transmission in a low-Earth orbit (LEO) satellite integrated network for railways. Preliminary verification through HIL provides initial schemes and parameter settings for field testing; field test data provides feedback to the HIL platform for simulation model optimization. This cyclical promotion significantly improves testing efficiency and accuracy. The proposed in-laboratory HIL testing scheme achieves high-precision simulation of dynamic satellite-to-ground interaction through railway and satellite environment modeling. Simulated satellite-to-ground fading data is used to create simulated data packets, enabling physical testing that approximates a field environment, allowing for low-cost and repeatable preliminary verification in the laboratory. The proposed field testing scheme for railway satellite-to-ground data communication verifies the performance of LEO satellites carrying railway services in terms of coverage, service quality, and service carrying capacity, providing a specific testing architecture and methods that can serve as a reference for conducting field tests in relevant scenarios.

[0049] Example 1

[0050] In this embodiment 1, a satellite-to-ground data transmission test system for a low-orbit satellite integrated network for railways is first provided, including: a first setup module for building a railway operating environment using VTD, including a basic railway environment, static scenes of buildings, base stations, and trackside equipment, and a dynamic scene of moving trains; a first acquisition module for acquiring railway operating data: in train simulation operation, real-time acquisition of train position coordinates, coordinates and types of surrounding environmental obstacles, and key train speed indicators in different typical railway environments; and a second setup module for building a satellite operating scenario using STK, including constellation type, number of satellites, satellite orbit parameters, and gateway station locations; and the acquisition of railway operating data from VTD. The system imports data into STK to obtain key information about ground trains, enabling the reproduction of the railway operating environment within STK. A calculation module runs satellite scenarios in STK, calculating the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage at fixed sampling intervals based on ephemeris and train operation information. An analysis module adds the acquired signal fading, power, and frequency offset data to an ideal waveform file, creating a simulated waveform file within a certain simulation timeframe. The created simulated waveform file is then analyzed, displaying the RSRP, RSSI, and SNR information of received data packets in real time, thus enabling the analysis of key railway train communication indicators.

[0051] In this embodiment, the above-described system is used to implement a satellite-to-ground data transmission test method for integrated low-orbit satellite networks for railways. This includes: building a railway operating environment using VTD, including a basic railway environment, static scenarios of buildings, base stations, and trackside equipment, and a dynamic scenario of moving trains; acquiring railway operating data: during train simulation, real-time acquisition of train position coordinates, coordinates and types of surrounding obstacles, and key train speed indicators in different typical railway environments; building a satellite operating scenario using STK, including constellation type, number of satellites, satellite orbit parameters, and gateway station locations; importing railway operating data acquired from VTD into STK to obtain key ground train information, thus reproducing the railway operating environment in STK; running the satellite scenario in STK, calculating the satellite-to-ground link signal fading magnitude, link connectivity, and signal coverage indicators at fixed sampling intervals based on ephemeris information and train operating information; adding the acquired signal fading data, power data, and frequency offset data to an ideal waveform file to create a simulation waveform file within a certain simulation time; analyzing the created simulation waveform file to display the RSRP, RSSI, and SNR information of received data packets in real time, thus analyzing key communication indicators of railway trains.

[0052] Specifically, the train is programmed with its own route, and it will travel along the prescribed route. At the same time, the train will analyze and process sensor data to perceive its surrounding environment and make decisions based on this information.

[0053] The simulated waveform file corresponds to the data packet arriving at the train receiving end, and is used to represent the changes in the signal when it arrives at the train receiving end during real satellite-to-ground data transmission.

[0054] The calculation method for Doppler frequency deviation at different vehicle speeds is shown in the following formula:

[0055] ;

[0056] in The Doppler frequency shift is caused by satellite motion. For vehicle speed, Original signal carrier frequency, At the speed of light, The angle between the train's direction of movement and the satellite-to-ground link;

[0057] in, ;

[0058] in For the satellite's angular velocity, satisfying ,in The gravitational constant of Earth, For the Earth's radius, The angle of elevation.

[0059] To determine link connectivity, a minimum elevation angle threshold for the satellite-to-ground link can be set. And compare the real-time elevation angle of the satellite-to-ground link obtained in STK. and ,when ≥ When the signal is active, the link is connected; otherwise, the link is disconnected. For calculating signal coverage, a minimum signal-to-noise ratio threshold is set for the ground receiver. In STK, uniform sampling is performed within a certain area of ​​the ground surface to obtain the real-time signal-to-noise ratio of each sampling point. Search near The locations of these locations, and the area enclosed by these locations, constitute the signal coverage area.

[0060] For signal coverage performance, an RSRP threshold meeting the minimum requirements for train communication is set. The RSRP obtained from the host computer software is compared with the threshold, and the length of the coverage area exceeding the RSRP threshold is statistically analyzed to assess signal coverage performance. For signal holding performance, the changes in RSRP and SNR over time are analyzed. The proportion of time during which both RSRP and SNR are greater than the threshold is statistically analyzed to assess signal holding performance. For communication capacity, the SNR obtained from the host computer software is calculated using Shannon's formula. For latency, the propagation distance of the satellite-to-ground link obtained from STK is divided by the speed of light. For packet loss rate, the total number of data packets transmitted by the integrated testing instrument is statistically analyzed. And the total number of data packets successfully received by the host computer. ,pass get.

[0061] Example 2

[0062] This embodiment proposes a communication performance testing method for the integrated scenario of "low-Earth orbit satellite + high-speed rail," aiming to solve the problems of high testing cost, low efficiency, and poor repeatability in existing technologies. This method combines laboratory hardware-in-the-loop simulation with field measurements to construct a closed-loop optimized testing system, such as... Figure 1 As shown, it can quickly and efficiently complete multi-scenario, multi-parameter railway satellite communication testing tasks without relying on long-term railway resources.

[0063] This embodiment proposes a laboratory hardware-in-the-loop (HIL) simulation test scheme, consisting of a software platform and a hardware platform. The software platform is implemented using traffic simulation software VTD and satellite simulation software STK, while the hardware simulation platform comprises a comprehensive testing instrument, a GPS synchronization unit, and the satellite terminal under test. The HIL simulation test architecture diagram is shown below. Figure 2 As shown.

[0064] Due to its strong simulation capabilities and outstanding high-precision real-time rendering effects, VTD is currently widely used as a mainstream simulation software by major OEMs and in the rail transit industry. It runs on the Linux platform, and its simulation elements include pedestrians / animals, traffic models, virtual worlds, weather / lighting, sensor simulation, and vehicle dynamics. VTD's road models are developed based on the OpenDRIVE standard, supporting standards such as OpenDrive, OpenCRG, and OpenSCENARIO. It supports lane-level road modeling, with no limit on development mileage, a rich built-in scene library, and supports user-defined development. It supports importing high-precision maps in OpenDRIVE format and OSM format maps. The construction of VTD traffic scenes mainly includes static scene setup and dynamic scene setup.

[0065] VTD can be used to build high-speed rail operation scenarios, including static scenes such as tracks, trackside equipment, trackside buildings, and vegetation. VTD's Road Designer is an interactive road network modeler that can be used as the foundation for creating 3D worlds. It contains a large number of built-in 3D objects and texture resources, and can create complete databases and basic building blocks.

[0066] STK is a widely used satellite simulation tool that supports custom satellite constellations, orbital root numbers, number of satellites, and other key parameters. It can achieve large-scale low-Earth orbit satellite modeling and obtain key indicators such as satellite position coordinates, satellite signal fading, and satellite link connectivity in real time.

[0067] The main steps of the laboratory-based semi-physical testing scheme proposed in this embodiment are as follows:

[0068] The testing system mainly includes a railway operation scenario construction module, a railway operation data acquisition module, a satellite operation scenario construction module, a communication indicator acquisition module, a waveform file generation module, and a hardware simulation and performance analysis module. The descriptions and functions of each module are as follows:

[0069] 1) Railway Operation Scenario Construction Module. This module utilizes VTD to build a railway operation environment, including static scenarios such as basic railway infrastructure, buildings, base stations, and trackside equipment, as well as dynamic scenarios involving moving trains. Trains are programmed with their travel paths, and will follow the prescribed routes. Simultaneously, trains can analyze and process sensor data to perceive their surroundings and make decisions based on this information, performing a series of operations such as deceleration, acceleration, and braking. Typical railway scenarios are also constructed, including those for plains, cuttings, viaducts, plateaus, and emergency rescue.

[0070] 2) Railway Operation Data Acquisition Module. During train simulation operation, the module acquires and saves key indicators such as train position coordinates, coordinates and types of surrounding obstacles, and train speed in real time in different typical railway environments.

[0071] 3) Satellite Operation Scenario Construction Module. This module uses STK to construct satellite operation scenarios, including constellation type, number of satellites, satellite orbital parameters, and gateway station locations. Furthermore, railway operation data obtained from VTD is imported into STK to acquire key information about ground objects such as trains, enabling the reproduction of the railway operation environment within STK.

[0072] 4) Communication Indicator Acquisition Module. In STK, a satellite scenario is run. At fixed sampling intervals, indicators such as the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage are calculated based on ephemeris information and train operation information. These indicators are saved as input for subsequent hardware platform use.

[0073] Calculating signal fading in satellite-to-ground links requires using path loss models, transmit antenna gain models, and receive antenna gain models. The logarithmic form of the path loss can be expressed as:

[0074] (1)

[0075] in For free space path loss, The signal loss due to rainfall and clouds as it passes through the atmosphere. The atmospheric absorption loss experienced by the satellite signal as it passes through the atmosphere can be calculated using the methods provided in ITU-R P.618 and ITU-R P.676, respectively. The transmitting antenna gain model can be the antenna gain model defined in ITU-R S.1528, and the ground-based satellite terminal receiving antenna gain model can be the antenna gain model defined in ITU-R S.465.

[0076] To determine link connectivity, a minimum elevation angle threshold for the satellite-to-ground link can be set. And compare the real-time elevation angle of the satellite-to-ground link obtained in STK. and ,when ≥ When the signal is strong, the link is active; otherwise, the link is weak.

[0077] To calculate signal coverage, a minimum signal-to-noise ratio threshold that the ground receiver can receive can be set. In STK, uniform sampling is performed within a certain area of ​​the ground surface to obtain the real-time signal-to-noise ratio of each sampling point. Search near The locations of these locations define the signal coverage area, where the real-time signal-to-noise ratio (SNR) is... The calculation method is as follows:

[0078] (2)

[0079] in For satellite signal transmission power, Boltzmann's constant, This is the receiver's equivalent thermal noise power. This refers to the communication bandwidth.

[0080] 5) Waveform File Generation Module. Using MATLAB, key data such as signal fading, power, and frequency offset acquired from the software platform are added to an ideal waveform file. This enables the creation of a simulated waveform file within a specific simulation timeframe. Signal fading and power data can be added by adjusting the signal amplitude in the ideal waveform file within MATLAB. Frequency offset data can be added by applying a corresponding small-scale channel fading model to the ideal waveform file within MATLAB. This simulated waveform file corresponds to the data packet arriving at the train receiver in the software platform, representing the changes in signal strength from the satellite transmitter to the train receiver during real satellite-to-ground data transmission.

[0081] 6) Hardware Simulation and Performance Analysis Module. This section is the hardware implementation part of the hardware-in-the-loop simulation. The prepared simulation waveform file is transmitted through the integrated testing instrument and received by the satellite terminal under test. This satellite terminal is the one used on the train receiver side in a real environment and is synchronized by a GPS synchronization unit. The satellite terminal has a reception statistics function, which can display information such as RSRP, RSSI, and SNR of received data packets in real time through the host computer software. The recorded information can then be imported into data analysis software such as MATLAB for further analysis, realizing the analysis of key communication indicators of railway trains such as signal coverage performance, hold-up performance, communication capacity, latency, and packet loss rate.

[0082] For signal coverage performance, an RSRP threshold that meets the minimum requirements for train communication is set. The RSRP obtained by the host computer software is compared with the threshold, and the length of the coverage area that exceeds the RSRP threshold is counted to analyze the signal coverage performance.

[0083] To assess signal retention performance, the changes in RSRP and SNR over time are analyzed. The signal retention performance is assessed by statistically analyzing the proportion of time during which both RSRP and SNR are greater than the threshold in the total simulation time.

[0084] For communication capacity, the SNR obtained from the host computer software can be calculated using Shannon's formula. The calculation method is as follows:

[0085] (3);

[0086] The time delay can be obtained by dividing the satellite-to-ground link propagation distance obtained in STK by the speed of light;

[0087] To determine the packet loss rate, one can count the total number of data packets transmitted by the integrated testing instrument. And the total number of data packets successfully received by the host computer. ,pass Yes, it can be obtained.

[0088] In this embodiment, the above steps enable a preliminary evaluation of the railway satellite communication network performance in the laboratory before field testing. By adjusting and optimizing the simulation model and parameter configuration (such as terminal power, handover threshold, link scheduling strategy, etc.) in a controllable and repeatable experimental environment, a stable and efficient initial solution is provided for field testing, thereby improving the efficiency and success rate of field testing.

[0089] This embodiment also proposes a field testing scheme. Field testing requires a comprehensive evaluation of the satellite communication system's performance in different railway application scenarios to ensure it meets business requirements and service quality standards. This includes coverage capability testing of low-Earth orbit (LEO) satellite communication in typical railway scenarios, LEO satellite communication network service quality testing, and application function testing of satellite communication carrying railway services.

[0090] The testing system includes a railway train, a host computer, a portable satellite terminal, low-Earth orbit (LEO) satellites, a gateway station, and an operator network. The host computer is divided into a transmitter host computer and a receiver host computer. The receiver host computer is interconnected with the portable satellite terminal, and the transmitter host computer periodically sends test data packets through the operator network. The portable satellite terminal, capable of receiving LEO satellite data, is housed inside the train along with the receiver host computer, and its antenna is magnetically mounted on the roof. The LEO satellites and gateway station utilize existing equipment from domestic LEO satellite companies. The specific system composition and testing architecture are as follows: Figure 3 As shown.

[0091] In this embodiment, the proposed test items and test methods are as follows:

[0092] Test 1: Low-orbit satellite communication coverage test in railway scenarios.

[0093] The test content includes: testing the changes in satellite link signal-to-noise ratio under different vehicle speeds, driving environments, and weather conditions to verify whether the minimum requirements for normal coverage are met. The test also examines the magnitude of the Doppler frequency offset of the signal received at the receiver under different vehicle speeds, and whether data packets can be received normally under these conditions. The calculation method for Doppler frequency offset at different vehicle speeds is shown in the following formula:

[0094] (4)

[0095] in The Doppler frequency shift is caused by satellite motion. For vehicle speed, Original signal carrier frequency, At the speed of light, This is the angle between the train's direction of movement and the satellite-to-ground link. It can be calculated using the following formula:

[0096] (5)

[0097] in For the satellite's angular velocity, satisfying ,in The gravitational constant of Earth, For the Earth's radius, The angle of elevation.

[0098] The testing method includes the following steps:

[0099] Connect the test equipment according to the block diagram;

[0100] Under different vehicle speed conditions, the test is conducted for a certain period of time. The operator's host computer periodically sends test data packets and records the signal-to-noise ratio of the test data packets received by the vehicle's host computer during this period, paying attention to the changes in signal-to-noise ratio caused by changes in vehicle speed. Using tools such as a spectrum analyzer, the Doppler frequency offset of the signal received by the vehicle's host computer during the test period is recorded, and it is also recorded whether the data packets can be demodulated and received normally when the frequency offset is different.

[0101] Under different vehicle driving environments, such as plains, viaducts, road cuts, and tunnels, tests were conducted for a certain period of time using the same testing method as above, focusing on the changes in signal-to-noise ratio and Doppler frequency shift caused by environmental occlusion.

[0102] Under different weather conditions, such as sunny days and rainy / snowy days, test for a certain period of time using the same testing method as above, and pay attention to the changes in signal-to-noise ratio and Doppler frequency shift caused by weather factors.

[0103] Plot the signal-to-noise ratio curves under different vehicle speeds, environmental conditions, and weather conditions to observe the variation patterns of coverage areas with good, good, and poor coverage, as well as the sensitivity of influencing factors; plot the joint curve of Doppler frequency offset and data packet reception rate to observe the impact of the magnitude of Doppler frequency offset on satellite network coverage performance.

[0104] Test 2: Service quality test of low-orbit satellite communication network in railway scenario.

[0105] The testing included assessing the access performance of the low-Earth orbit satellite communication network during train operation, its communication maintenance capability during movement, and service stability during multi-point link handover. Key service quality indicators (SQIs) were emphasized, including access establishment success rate, channel hold-up time, mobility interruption rate, and handover latency.

[0106] The testing methods include:

[0107] Connect the test equipment according to the block diagram;

[0108] Under different train speed conditions, access tests were conducted during the train start-up phase, stable operation phase, and when entering the edge region of the satellite beam, and the terminal access latency and access success rate were recorded.

[0109] While the train is in motion, test for a period of time and record whether the communication session can be maintained continuously, paying attention to the connection interruption rate in scenarios with obstructions such as crossing complex terrain.

[0110] During train movement, the occurrence time and response time of multiple inter-satellite handover events are recorded to analyze whether inter-satellite handover leads to connection interruption or performance degradation.

[0111] Plot the correlation between performance indicators such as vehicle speed, driving environment, switching frequency, interruption probability, and access latency, and analyze the service maintenance performance of the train's connection with the satellite during movement in different scenarios.

[0112] Test 3: Performance test of low-orbit satellite communication carrying railway application services in railway scenarios.

[0113] The test content includes: testing the service carrying capacity of the low-orbit satellite communication system in typical railway business scenarios, such as dispatching instructions, train control signals, video transmission, passenger Wi-Fi, etc., and evaluating its performance in key indicators such as bandwidth, latency, and packet loss rate to meet the railway communication needs in a real operating environment.

[0114] The testing methods include:

[0115] Connect the test equipment according to the block diagram;

[0116] Under different vehicle speed conditions, voice, video, and control command services were tested respectively, and the actual available bandwidth, latency, and packet loss rate under each service were measured.

[0117] Test services such as voice, video, and control commands in complex driving environments, focusing on the impact of obstruction and frequent switching scenarios on service performance, especially the performance of critical driving services such as train control services, and record the actual available bandwidth, latency, and packet loss rate.

[0118] Test services such as voice, video, and control commands under different weather conditions, record the service continuity and performance change curves under conditions such as rain and snow, and record the actual available bandwidth, latency, and packet loss rate.

[0119] The performance indicators of various services under different operating conditions are summarized, and a three-dimensional performance curve of bandwidth-packet loss rate-latency is plotted to analyze the correlation between the indicators and their impact on the availability of railway applications.

[0120] In this embodiment, the above-mentioned testing method was used to verify the railway satellite communication service capability in a real field environment. The field test data can also help improve the accuracy of the hardware-in-the-loop simulation system and correct unreasonable settings and models in the simulation. Through the cyclical verification of hardware-in-the-loop simulation and field testing, it is helpful to build a high-precision, high-efficiency, and high-reliability railway satellite ground-to-space data communication performance testing platform.

[0121] Example 3

[0122] This embodiment 3 provides a non-transitory computer-readable storage medium for storing computer instructions. When these computer instructions are executed by a processor, they implement the above-described method for testing satellite-to-ground data transmission in a low-orbit satellite-railway integrated network. The method includes:

[0123] VTD is used to build a railway operating environment, including a basic railway environment, static scenes of buildings, base stations, and trackside equipment, and dynamic scenes of moving trains.

[0124] Railway operation data acquisition: In train simulation operation, the train position coordinates, coordinates and types of surrounding obstacles, and key train speed indicators are acquired in real time in different typical railway environments;

[0125] STK is used to build a satellite operation scenario, including constellation type, number of satellites, satellite orbit parameters and gateway station locations; railway operation data obtained from VTD is imported into STK to obtain key information about ground trains and realize the reproduction of the railway operation environment in STK;

[0126] In STK, satellite scenarios are run, and at fixed sampling intervals, the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage are calculated based on ephemeris information and train operation information.

[0127] The acquired signal fading data, power data, and frequency offset data are added to the ideal waveform file to create a simulation waveform file within a certain simulation time.

[0128] The prepared simulation waveform file is analyzed to display the RSRP, RSSI, and SNR information of the received data packets in real time, thereby realizing the analysis of key communication indicators of railway trains.

[0129] Example 4

[0130] This embodiment 4 provides a computer device, including a memory and a processor. The processor and the memory communicate with each other. The memory stores program instructions that can be executed by the processor. The processor calls the program instructions to execute the satellite-to-ground data transmission test method for a low-orbit satellite integrated network for railways as described above. The method includes:

[0131] VTD is used to build a railway operating environment, including a basic railway environment, static scenes of buildings, base stations, and trackside equipment, and dynamic scenes of moving trains.

[0132] Railway operation data acquisition: In train simulation operation, the train position coordinates, coordinates and types of surrounding obstacles, and key train speed indicators are acquired in real time in different typical railway environments;

[0133] STK is used to build a satellite operation scenario, including constellation type, number of satellites, satellite orbit parameters and gateway station locations; railway operation data obtained from VTD is imported into STK to obtain key information about ground trains and realize the reproduction of the railway operation environment in STK;

[0134] In STK, satellite scenarios are run, and at fixed sampling intervals, the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage are calculated based on ephemeris information and train operation information.

[0135] The acquired signal fading data, power data, and frequency offset data are added to the ideal waveform file to create a simulation waveform file within a certain simulation time.

[0136] The prepared simulation waveform file is analyzed to display the RSRP, RSSI, and SNR information of the received data packets in real time, thereby realizing the analysis of key communication indicators of railway trains.

[0137] Example 5

[0138] This embodiment 5 provides an electronic device, including: a processor, a memory, and a computer program; wherein, the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory to cause the electronic device to execute instructions for implementing the above-described test method for satellite-to-ground data transmission for a low-orbit satellite-railway integrated network, the method including:

[0139] VTD is used to build a railway operating environment, including a basic railway environment, static scenes of buildings, base stations, and trackside equipment, and dynamic scenes of moving trains.

[0140] Railway operation data acquisition: In train simulation operation, the train position coordinates, coordinates and types of surrounding obstacles, and key train speed indicators are acquired in real time in different typical railway environments;

[0141] STK is used to build a satellite operation scenario, including constellation type, number of satellites, satellite orbit parameters and gateway station locations; railway operation data obtained from VTD is imported into STK to obtain key information about ground trains and realize the reproduction of the railway operation environment in STK;

[0142] In STK, satellite scenarios are run, and at fixed sampling intervals, the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage are calculated based on ephemeris information and train operation information.

[0143] The acquired signal fading data, power data, and frequency offset data are added to the ideal waveform file to create a simulation waveform file within a certain simulation time.

[0144] The prepared simulation waveform file is analyzed to display the RSRP, RSSI, and SNR information of the received data packets in real time, thereby realizing the analysis of key communication indicators of railway trains.

[0145] In summary, this invention proposes a testing scheme combining laboratory hardware-in-the-loop (HIL) simulation and field testing for testing satellite-to-ground data transmission in a low-Earth orbit (LEO) satellite integrated network for railways. Prior verification through laboratory HIL simulation provides preliminary schemes and parameter settings for field testing; field test data allows for feedback to the HIL simulation platform for simulation model optimization. This cyclical promotion significantly improves testing efficiency and accuracy. This invention proposes a laboratory HIL simulation testing scheme that achieves high-precision simulation of dynamic satellite-to-ground interaction through railway and satellite environment modeling. Simulated satellite-to-ground fading data is used to create simulated data packets, enabling physical testing that approximates a field environment, achieving low-cost and repeatable prior verification in the laboratory. This invention also proposes a field testing scheme for railway satellite-to-ground data communication, verifying the performance of LEO satellites carrying railway services in terms of coverage, service quality, and service carrying capacity. It provides a specific testing architecture and methods, offering a reference for conducting field tests in relevant scenarios.

[0146] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0147] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1A device that provides the functions specified in one or more boxes.

[0148] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0149] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment, whereby a series of operational steps are performed to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0150] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or variations that can be made by those skilled in the art without creative effort should be included within the scope of protection of the present invention.

Claims

1. A method for testing data transmission between a satellite and the ground in a railway-oriented integrated network of low earth orbit satellites, characterized in that, include: VTD is used to build a railway operating environment, including a basic railway environment, static scenes of buildings, base stations, and trackside equipment, and dynamic scenes of moving trains. Railway operation data acquisition: In train simulation operation, the train position coordinates, coordinates and types of surrounding obstacles, and key train speed indicators are acquired in real time in different typical railway environments; Use STK to build a satellite operation scenario, including constellation type, number of satellites, satellite orbital parameters, and gateway station locations; Railway operation data obtained from VTD will be imported into STK to obtain key information about ground trains and realize the reproduction of the railway operation environment in STK; In STK, satellite scenarios are run, and at fixed sampling intervals, the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage are calculated based on ephemeris information and train operation information. The acquired signal fading data, power data, and frequency offset data are added to the ideal waveform file to create a simulation waveform file within a certain simulation time. The prepared simulation waveform file is analyzed to display the RSRP, RSSI, and SNR information of the received data packets in real time, thereby realizing the analysis of key communication indicators of railway trains.

2. The method of claim 1, wherein the method is a method of testing a satellite-to-ground data transmission of a railway-oriented integrated network of low earth orbit satellites, and The train is programmed with its own route, and it will travel along the prescribed route. At the same time, the train will analyze and process sensor data to perceive its surrounding environment and make decisions based on this information.

3. The method of claim 1, wherein the method is a method of testing a satellite-to-ground data transmission of a railway-oriented integrated network of low earth orbit satellites, and The simulated waveform file corresponds to the data packet arriving at the train receiving end, and is used to represent the changes in the signal when it arrives at the train receiving end during real satellite-to-ground data transmission.

4. The method of claim 1, wherein the method is a method of testing a satellite-to-ground data transmission of a railway-oriented integrated network of low earth orbit satellites, and The calculation method for Doppler frequency deviation at different vehicle speeds is shown in the following formula: ； in The Doppler frequency shift is caused by satellite motion. For vehicle speed, Original signal carrier frequency, At the speed of light, The angle between the train's direction of movement and the satellite-to-ground link; in, ; in For the satellite's angular velocity, satisfying ,in The gravitational constant of Earth, For the Earth's radius, The angle of elevation.

5. The satellite-to-ground data transmission test method for low-orbit satellite integrated networks for railways according to claim 1, characterized in that, To determine link connectivity, a minimum elevation angle threshold for the satellite-to-ground link can be set. And compare the real-time elevation angle of the satellite-to-ground link obtained in STK. and ,when ≥ When the signal is active, the link is connected; otherwise, the link is disconnected. For calculating signal coverage, a minimum signal-to-noise ratio threshold is set for the ground receiver. In STK, uniform sampling is performed within a certain area of ​​the ground surface to obtain the real-time signal-to-noise ratio of each sampling point. Search near The locations of these locations, and the area enclosed by these locations, constitute the signal coverage area.

6. The satellite-to-ground data transmission test method for low-orbit satellite integrated networks for railways according to claim 1, characterized in that, For signal coverage performance, an RSRP threshold meeting the minimum requirements for train communication is set. The RSRP obtained from the host computer software is compared with the threshold, and the length of the coverage area exceeding the RSRP threshold is statistically analyzed to assess signal coverage performance. For signal holding performance, the changes in RSRP and SNR over time are analyzed. The proportion of time during which both RSRP and SNR are greater than the threshold is statistically analyzed to assess signal holding performance. For communication capacity, the SNR obtained from the host computer software is calculated using Shannon's formula. For latency, the propagation distance of the satellite-to-ground link obtained from STK is divided by the speed of light. For packet loss rate, the total number of data packets transmitted by the integrated testing instrument is statistically analyzed. And the total number of data packets successfully received by the host computer. ,pass get.

7. A satellite-to-ground data transmission test system for integrated low-orbit satellite networks for railways, characterized in that, include: The first module is used to build a railway operating environment using VTD, including a basic railway environment, static scenes of buildings, base stations, trackside equipment, and dynamic scenes of moving trains. The first acquisition module is used to acquire railway operation data: during train simulation operation, it acquires the train position coordinates, coordinates and types of surrounding obstacles, and key indicators of train speed in real time in different typical railway environments; The second module is used to build satellite operation scenarios using STK, including constellation type, number of satellites, satellite orbital parameters, and gateway station locations; Railway operation data obtained from VTD will be imported into STK to obtain key information about ground trains and realize the reproduction of the railway operation environment in STK; The calculation module is used to run satellite scenarios in STK. At fixed sampling intervals, it calculates the magnitude of satellite-to-ground link signal fading, link connectivity, and signal coverage indicators based on ephemeris information and train operation information. The analysis module is used to add key data such as acquired signal fading data, power data, and frequency offset data to an ideal waveform file, thereby creating a simulation waveform file within a certain simulation time. The module then analyzes the created simulation waveform file and displays the RSRP, RSSI, and SNR information of the received data packets in real time, enabling the analysis of key communication indicators for railway trains.

8. A non-transitory computer-readable storage medium, characterized in that, The non-transitory computer-readable storage medium is used to store computer instructions, which, when executed by a processor, implement the satellite-to-ground data transmission test method for railway low-orbit satellite integrated networks as described in any one of claims 1-6.

9. A computer device, characterized in that, The device includes a memory and a processor, which communicate with each other. The memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to execute the satellite-to-ground data transmission test method for a low-orbit satellite integrated network for railways as described in any one of claims 1-6.

10. An electronic device, characterized in that, include: The device includes a processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to cause the electronic device to execute instructions for implementing the satellite-to-ground data transmission test method for a low-orbit satellite integrated network for railways as described in any one of claims 1-6.

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