Ionospheric interference optimization method and system for gnss receivers

Abstract

The application relates to the field of satellite positioning, and discloses a GNSS receiver ionospheric interference optimization method and system. The method comprises the following steps: a GNSS receiver performs positioning according to differential correction data received from a ground-based augmentation system, and calculates a positioning accuracy index; the GNSS receiver acquires local ionospheric interference intensity information; and in response to the calculated positioning accuracy index being worse than a first threshold and the local ionospheric interference intensity being higher than a second threshold, the GNSS receiver is switched to perform positioning according to differential correction data received from a network-based augmentation system. The application can dynamically perceive the occurrence of ionospheric interference, and realizes accurate positioning in the presence of strong ionospheric interference.

Description

Technical Field

[0001] This application relates to the field of satellite positioning, and in particular to ionospheric interference optimization technology for GNSS receivers. Background Technology

[0002] This section is intended to provide background or context for the embodiments of this application as set forth in the claims. The description herein is not intended to imply that it is prior art that has been disclosed, simply because it is included in this section.

[0003] Ionospheric delay error is one of the main sources of error affecting GNSS positioning accuracy. When electromagnetic wave signals pass through the ionosphere, the path will bend and refract, causing electromagnetic wave propagation errors. GNSS receivers will be affected, and the degree of impact depends on the frequency of the GNSS and the concentration of total free electrons (TEC).

[0004] Ionospheric activity affects all reference station networks, and its extent depends on the network structure. For network structures with distances of 50–70 km, the ionosphere significantly impacts the quality of network corrections. Under conditions of intense ionospheric activity, the ionospheric residuals in the network correction model data increase significantly, making integer ambiguity resolution more difficult, increasing the fixed time, and consequently reducing the available solutions. Furthermore, the long inter-station distances cause the ionospheric error model to deviate from reality, leading to larger residuals. Under the combined influence of these two factors, the rover cannot quickly obtain high-precision positioning solutions.

[0005] Network-based satellite augmentation systems (GNSS) broadcast services are not limited by bandwidth, allowing for the broadcasting of more content. Furthermore, the age at which users receive correction data is shorter than with satellite-based systems, enabling GNSS receivers to achieve faster convergence times and higher accuracy. Additionally, they are not constrained by the coverage area of ​​ground-based augmentation systems; services can still be used in areas not covered by ground-based systems as long as there is a network, greatly expanding the usable area.

[0006] Methods for correcting ionospheric delay errors generally include dual-frequency correction, differential positioning, half-sum correction, and ionospheric modeling. In practical applications, the choice of ionospheric delay correction strategy depends on the specific type of GNSS user. For dual-frequency GNSS receiver users, by considering the inverse relationship between the ionospheric delay effect and the square of the signal frequency, ionospheric-delay composite observations are formed, thereby minimizing the impact of ionospheric delay in the observation domain. For single-frequency GNSS receiver users, ionospheric delay can be eliminated by forming half-sum observations or corrected using a model.

[0007] Based on the above technical solutions, on the one hand, it is impossible to perceive the ionospheric interference and its severity in real time, and on the other hand, it is impossible to solve the problem of severe ionospheric interference in real time. Summary of the Invention

[0008] The purpose of this application is to provide a method and system for optimizing ionospheric interference in a GNSS receiver, which can dynamically sense the occurrence of ionospheric interference and achieve accurate positioning under strong ionospheric interference.

[0009] This application discloses a method for optimizing ionospheric interference in a GNSS receiver, including:

[0010] The GNSS receiver uses differential correction data received from the ground-based augmentation system to perform positioning and calculates positioning accuracy indicators;

[0011] The GNSS receiver acquires local ionospheric interference intensity information;

[0012] In response to a calculated positioning accuracy index being worse than a first threshold and the local ionospheric interference intensity being higher than a second threshold, the GNSS receiver switches to positioning based on differential correction data received from the network satellite-based augmentation system.

[0013] By adopting an intelligent switching scheme between ground-based augmentation systems and network-based satellite augmentation systems, the GNSS receiver will automatically switch between the two systems based on the positioning performance of the cellular network and the GNSS receiver. Depending on the operating location of the GNSS receiver, when ionospheric interference is severe, it will sense ionospheric interference in real time and switch to the network-based satellite augmentation system to improve the anti-ionospheric effect and enhance the positioning performance of the GNSS receiver.

[0014] In a preferred embodiment, when the GNSS receiver switches to performing a first positioning based on differential correction data received from the network satellite-based augmentation system, it still simultaneously performs a second positioning based on differential correction data received from the ground-based augmentation system.

[0015] If the duration for which the positioning accuracy index of the first positioning is higher than the positioning accuracy index of the second positioning exceeds a third threshold, the GNSS receiver switches to positioning based on differential correction data received from the ground-based augmentation system.

[0016] After the ionospheric interference weakens and disappears, the system automatically switches to a ground-based augmentation system, which can ensure the positioning accuracy of the GNSS receiver and reduce the computational resource consumption for positioning.

[0017] In a preferred embodiment, it also includes:

[0018] When the calculated positioning accuracy index is worse than a first threshold and the local ionospheric interference intensity is higher than a second threshold, the GNSS receiver switches to positioning based on differential correction data received from the network satellite-based augmentation system, and uses the PPP-AR algorithm to resolve and eliminate ambiguities in the GNSS observation data.

[0019] When switching to a network-based satellite augmentation system, the PPP-AR algorithm can be used to solve and eliminate ambiguities in GNSS observation data, thereby enhancing positioning accuracy. When switching to a ground-based augmentation system, PPP-AR is not used, thus reducing the amount of computation and speeding up the positioning calculation.

[0020] In a preferred embodiment, the local ionospheric interference intensity information is broadcast by the ground-based augmentation system. Specifically, the local ionospheric interference intensity information may be carried in RTCM messages broadcast by the ground-based augmentation system.

[0021] RTCM messages are meant to be sent continuously. Using RTCM messages with a proprietary protocol to carry local ionospheric interference intensity information eliminates the need to add new messages, thus reducing the air interface resource consumption for transmitting local ionospheric interference intensity information.

[0022] In various embodiments of this application, the positioning accuracy index may be differential age, whether the positioning is fixed under the ground-based augmentation system, ionospheric interference parameters, etc. This application does not limit the specific form of the positioning accuracy index, among which differential age is preferred.

[0023] In a preferred embodiment, before the GNSS receiver acquires local ionospheric interference intensity information, it further includes:

[0024] The server of the ground-based augmentation system receives the GNSS receiver location information transmitted back by the GNSS receiver and determines the grid location of the GNSS receiver in the ground-based augmentation system.

[0025] The ground-based augmentation system receives raw satellite observation data in real time through base stations at multiple different locations, and the server calculates ionospheric interference data for each grid based on the raw satellite observation data.

[0026] For grids with ionospheric interference intensity higher than the fourth threshold, the server notifies the GNSS receivers within the grid of the ionospheric interference intensity in real time.

[0027] Because ionospheric interference intensity is only transmitted to grids where the ionospheric interference intensity is higher than a predetermined threshold, the amount of data transmitted over the air interface can be reduced, and the computational resources of the GNSS receiver used to process the transmitted ionospheric interference intensity can be saved.

[0028] In a preferred embodiment, the ground-based augmentation system and the network satellite-based augmentation system communicate with the GNSS receiver using a cellular mobile communication system.

[0029] It is possible to achieve communication with GNSS receivers by taking advantage of the existing cellular mobile communication system's wide coverage, low communication latency, and low communication cost.

[0030] This application also discloses a GNSS receiver ionospheric interference optimization system, comprising:

[0031] Memory, used to store computer-executable instructions; and,

[0032] A processor, coupled to the memory, is configured to implement the steps of the method as described above when executing the computer-executable instructions.

[0033] This application also discloses a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the method described above.

[0034] The various technical features disclosed in the above-described invention, the various technical features disclosed in the following embodiments and examples, and the various technical features disclosed in the accompanying drawings can be freely combined to form various new technical solutions (all of which should be considered as having been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed. Features C and D are equivalent technical means that serve the same function, and technically only one needs to be used; it is impossible to use both simultaneously. Feature E can be technically combined with feature C. Therefore, the solution A+B+C+D should not be considered as having been recorded because it is technically infeasible, while the solution A+B+C+E should be considered as having been recorded. Attached Figure Description

[0035] Figure 1 This is a schematic flowchart of a GNSS receiver ionospheric interference optimization method according to one embodiment of this application;

[0036] Figure 2 This is a more detailed flowchart of a GNSS receiver ionospheric interference optimization method according to one embodiment of this application;

[0037] Figure 3 This is a flowchart illustrating a GNSS receiver ionospheric interference optimization method according to another embodiment of this application. Detailed Implementation

[0038] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0039] Explanation of some concepts:

[0040] Ground-Based Augmentation System (GBAS) is a ground-based reference system that provides accuracy, reliability, and availability enhancements to Global Navigation Satellite Systems (GNSS). Similar to Satellite-Based Augmentation Systems (SBAS), the primary purpose of GBAS is to improve GNSS performance. However, GBAS is mainly targeted at specific areas, such as the vicinity of airports, providing higher accuracy and integrity. GBAS achieves this by using ground reference stations to receive GNSS signals and calculate correction data. These reference stations transmit the correction data to broadcast stations, which then transmit the data to user equipment, such as GNSS receivers on aircraft. This correction data helps eliminate GNSS positioning errors, thereby improving accuracy. GBAS is primarily used in the civil aviation sector, especially around airports, to provide accurate flight approach, landing, and ground navigation services. GBAS can provide aircraft with more accurate and reliable navigation information, thereby improving flight safety and efficiency.

[0041] SBAS (Satellite-Based Augmentation System) is a supplementary service to the Global Navigation Satellite System (GNSS) to improve the accuracy, reliability, and availability of positioning, navigation, and timing services. SBAS achieves this by collecting correction data from GNSS satellites using ground reference stations. These reference stations transmit the data to a master control center, which calculates the satellite correction data and sends it back to the SBAS satellites in geostationary orbit. These SBAS satellites then broadcast the correction data back to Earth as augmented signals for use by GNSS receivers. This correction data helps eliminate GNSS positioning errors, thereby improving accuracy.

[0042] The Age of Differential (AOD) is a positioning accuracy metric associated with Differential Global Navigation Satellite Systems (DGNSS). DGNSS improves positioning accuracy by receiving GNSS signals from a ground reference station and calculating correction data. This correction data helps eliminate GNSS positioning errors, thereby improving accuracy. The AOD refers to the time interval between the reference station calculating the correction data and the GNSS receiver using that data for positioning. Ideally, the AOD should be as short as possible to ensure the real-time nature of the correction data. The timeliness of the correction data is crucial for maintaining high positioning accuracy because many error sources (such as atmospheric errors, satellite orbit errors, etc.) change over time. A long AOD may mean that the correction data is outdated and may no longer be applicable to the current positioning situation. This can lead to a decrease in positioning accuracy. Therefore, by monitoring and controlling the AOD, the high performance and accuracy of the DGNSS system can be ensured.

[0043] A Global Navigation Satellite System (GNSS) is a system that provides globally covered positioning, navigation, and time synchronization services using satellites in Earth orbit. GNSS allows receivers to determine their position, velocity, and time by measuring their distance from satellites. This information can be applied to various fields, such as transportation, aviation, maritime, agriculture, and earth sciences.

[0044] PPP-AR (Precise Point Positioning with Ambiguity Resolution) is a method for achieving high-precision positioning using single-frequency or dual-frequency Global Navigation Satellite System (GNSS) observation data. The core of the PPP-AR algorithm lies in resolving and eliminating ambiguities (i.e., integer ambiguities) in the GNSS observation data, thereby improving positioning accuracy and reliability. Traditional PPP methods typically use floating-point ambiguity resolution when solving for GNSS receiver coordinates, which leads to limited positioning accuracy. The PPP-AR algorithm, however, significantly improves positioning accuracy by resolving integer ambiguities and fixing them to integer values. Typically, the PPP-AR algorithm can achieve centimeter-level or sub-centimeter-level positioning accuracy.

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0046] The first embodiment of this application relates to a method for optimizing ionospheric interference in a GNSS receiver, the process of which is as follows: Figure 1 As shown, the method includes the following steps:

[0047] Step 101: The GNSS receiver performs positioning based on the differential correction data received from the ground-based augmentation system and calculates the positioning accuracy index.

[0048] Step 102: The GNSS receiver acquires local ionospheric interference intensity information. Steps 101 and 102 can be executed in parallel. Optionally, in one embodiment, the local ionospheric interference intensity information is carried in RTCM messages broadcast by the ground-based augmentation system. Private RTCM protocol messages can be used.

[0049] Step 103: Determine whether the calculated positioning accuracy index is worse than the first threshold and the local ionospheric interference intensity is higher than the second threshold. If so, proceed to step 104; otherwise, return to step 101.

[0050] Step 104: In response to the calculated positioning accuracy index being worse than the first threshold and the local ionospheric interference intensity being higher than the second threshold, the GNSS receiver switches to positioning based on differential correction data received from the network satellite-based augmentation system. Optionally, the PPP-AR algorithm is used to resolve and eliminate ambiguities in the GNSS observation data during positioning. Ambiguities in the GNSS observation data are due to errors generated during satellite signal propagation; these errors need to be eliminated to improve positioning accuracy. In addition to the PPP-AR algorithm, the LAMBDA algorithm (Least-squares AM Biguity Decorrelation Adjustment), BOOTSTRAP algorithm, etc., can also be used. Optionally, positioning accuracy indicators include, but are not limited to, differential age, whether the positioning is fixed under the ground-based augmentation system, ionospheric interference parameters, etc.

[0051] When ionospheric interference is severe (which can be detected in real time through messages distributed by the ground-based augmentation system), i.e. when the positioning accuracy is worse than the first threshold and the local ionospheric interference intensity is higher than the second threshold, this application switches to the network satellite-based augmentation system and uses differential correction data received from the network satellite-based augmentation system for positioning, which can improve the anti-ionospheric effect.

[0052] Optional, see reference Figure 2 As shown, in one embodiment, the method further includes the following steps:

[0053] In step 105, when the GNSS receiver switches to performing the first positioning based on the differential correction data received from the network satellite-based augmentation system, it still simultaneously performs the second positioning based on the differential correction data received from the ground-based augmentation system.

[0054] Step 106: Determine whether the duration for which the positioning accuracy index of the first positioning is higher than that of the second positioning exceeds the third threshold. If yes, proceed to step 107; otherwise, return to step 105.

[0055] Step 107: In response to the duration for which the positioning accuracy index of the first positioning is higher than the positioning accuracy index of the second positioning exceeds a third threshold, the GNSS receiver switches to positioning based on differential correction data received from the ground-based augmentation system.

[0056] After the ionospheric interference weakens and disappears, i.e., when the duration of the first positioning accuracy index being higher than the second positioning accuracy index exceeds a third threshold, this application automatically switches to the ground-based augmentation system and uses the differential correction data received from the ground-based augmentation system for positioning, thereby ensuring the positioning accuracy of the GNSS receiver.

[0057] Based on the GNSS receiver's operating location and the performance of the mobile cellular network, ionospheric interference is sensed in real time, and the system automatically switches between ground-based augmentation systems and network-based satellite augmentation systems to improve the positioning performance of the GNSS receiver.

[0058] Optionally, in one embodiment, the method prior to step 102 may further include the following steps:

[0059] Step 108: The server of the ground augmentation system receives the GNSS receiver location information transmitted back by the GNSS receiver and determines the grid location of the ground augmentation system where the GNSS receiver is located.

[0060] Step 109: The ground-based augmentation system receives raw satellite observation data in real time through base stations at multiple different locations. The server calculates the ionospheric interference data for each grid based on the raw satellite observation data.

[0061] Step 110: For grids with ionospheric interference intensity higher than the fourth threshold, the server notifies the GNSS receivers within the grid of the ionospheric interference intensity in real time.

[0062] Optionally, in one embodiment, the ground-based augmentation system and the network-based satellite augmentation system communicate with the GNSS receiver using a cellular mobile communication system. The cellular mobile communication system includes, but is not limited to, third-generation (3G), fourth-generation (4G), and fifth-generation (5G) mobile communication systems.

[0063] To better understand the technical solution of this application, a specific example is provided below. The details listed in this example are mainly for ease of understanding and are not intended to limit the scope of protection of this application.

[0064] In the presence of a cellular wireless network (201), the GNSS receiver receives differential correction data played by the ground-based augmentation system server via the wireless network, achieving centimeter-level positioning accuracy (202). The GNSS receiver receives RTCM differential data every second. Simultaneously, it transmits the device's location information back to the ground-based augmentation system server via the cellular wireless network.

[0065] The ground augmentation system server receives the device location information transmitted back by the GNSS receiver and determines the grid location of the ground augmentation system where the device is located.

[0066] The ground-based augmentation system receives and transmits the raw satellite observation data back in real time to complete data acquisition. By adopting precise ionospheric modeling and upgrading the anti-ionospheric algorithm, applying Gaussian models and utilizing machine learning, the system completes the assessment of ionospheric activity and calculates ionospheric interference index data for different base station locations.

[0067] For grids with severe ionospheric interference, the ground-based augmentation system server can use a private RTCM protocol message to notify the GNSS receivers within the grid of the ionospheric interference index in real time.

[0068] After receiving a severe ionospheric interference alarm, the GNSS receiver assesses the following conditions (203): whether the environment is open, the foundation is unstable, and the ionospheric interference index parameter exceeds the limit. If all these conditions are met, the GNSS receiver actively switches to the network satellite-based augmentation system (204) and uses the network satellite-based correction data to ensure that the equipment obtains a high-precision positioning result. Otherwise, it continues to use the ground-based augmentation system for positioning (206).

[0069] When ionospheric interference weakens, the GNSS device compares the positioning results obtained using network satellite-based correction data with the positioning results obtained using the RTCM correction data of the ground-based augmentation system. If the positioning results obtained using the RTCM correction data of the ground-based augmentation system are better (205), the device automatically switches to the ground-based augmentation system (206) and resumes normal operation.

[0070] In the absence of a cellular mobile communication network 201 or at the customer's request (208), the system can be switched to a satellite-based augmentation system (209).

[0071] Accordingly, embodiments of this application also provide a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the various method embodiments of this application. Computer-readable storage media include permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device. As defined herein, computer-readable storage media does not include transient media, such as modulated data signals and carrier waves.

[0072] Furthermore, embodiments of this application also provide a GNSS receiver ionospheric interference optimization system, including a memory for storing computer-executable instructions and a processor; the processor is used to implement the steps in the above-described method embodiments when executing the computer-executable instructions in the memory. The processor may be a Central Processing Unit (CPU), Graphics Processing Unit (GPU), Digital Signal Processor (DSP), Microcontroller Unit (MCU), Neural Processing Unit (NPU), Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), or other programmable logic devices. The aforementioned memory may be read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or solid-state drive, etc. The steps of the methods disclosed in the embodiments of this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules in the processor.

[0073] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0074] The numbering used in describing the steps of a method does not inherently limit the order of these steps. For example, a step with a higher number does not necessarily have to be executed after a step with a lower number; it can be executed first and then second, or even in parallel, as long as this execution order is reasonable to someone skilled in the art. Similarly, multiple steps with consecutively numbered sequences (e.g., step 101, step 102, step 103, etc.) do not restrict other steps from being executed between them; for example, there can be other steps between step 101 and step 102.

[0075] This specification includes combinations of various embodiments described herein. Individual references to embodiments are made (e.g., "one embodiment," "some embodiments," or "preferred embodiments"); however, these embodiments are not mutually exclusive unless indicated to be mutually exclusive or are readily apparent to those skilled in the art. It should be noted that the word "or" is used in a non-exclusive sense throughout this specification unless the context explicitly indicates or requires it.

[0076] All references to this specification are considered to be incorporated integrally into the disclosure of this application so that they can serve as the basis for modifications if necessary. Furthermore, it should be understood that the above descriptions are merely preferred embodiments of this specification and are not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments of this specification should be included within the scope of protection of one or more embodiments of this specification.

[0077] In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A method for optimizing ionospheric interference in a GNSS receiver, characterized in that, include: The GNSS receiver performs positioning based on differential correction data received from the ground-based augmentation system and calculates positioning accuracy indicators, including differential age. The server of the ground-based augmentation system receives the GNSS receiver location information transmitted back by the GNSS receiver and determines the grid location of the GNSS receiver in the ground-based augmentation system. The ground-based augmentation system receives raw satellite observation data in real time through base stations at multiple different locations, and the server calculates ionospheric interference data for each grid based on the raw satellite observation data. For grids with ionospheric interference intensity higher than the fourth threshold, the server notifies the GNSS receivers within the grid of the ionospheric interference intensity in real time. The GNSS receiver acquires local ionospheric interference intensity information, which is broadcast by the ground-based augmentation system and carried in the RTCM message broadcast by the ground-based augmentation system. After receiving a severe ionospheric interference alarm, the GNSS receiver equipment assesses whether the environment is open, the foundation is not stable, and the ionospheric interference index parameter exceeds the limit. If all the conditions of open environment, unstable foundation, and ionospheric interference index parameter exceeding the limit are met, in response to the dual conditions of the calculated positioning accuracy index being worse than the first threshold and the local ionospheric interference intensity being higher than the second threshold being met simultaneously, the GNSS receiver switches to performing first positioning based on differential correction data received from the network satellite-based augmentation system based on cellular mobile communication system, and uses the PPP-AR algorithm to solve and eliminate ambiguity in the GNSS observation data; Otherwise, the GNSS receiver will still use the ground-based augmentation system for positioning; When the GNSS receiver switches to perform the first positioning, it still performs the second positioning simultaneously based on the differential correction data received from the ground-based augmentation system. In response to the duration that the positioning accuracy index of the first positioning is higher than the positioning accuracy index of the second positioning for more than a third threshold, the GNSS receiver switches to perform positioning based on the differential correction data received from the ground-based augmentation system, and does not use the PPP-AR algorithm to solve and eliminate ambiguity in the GNSS observation data.

2. A GNSS receiver ionospheric interference optimization system, characterized in that, include: Memory is used to store executable instructions for a computer; as well as, A processor, coupled to the memory, is configured to implement the steps of the method as described in claim 1 when executing the computer-executable instructions.

3. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions that, when executed by a processor, implement the steps of the method as described in claim 1.

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