Method for sending short message, short message terminal and medium

Abstract

A method for sending a short message, a short message terminal and a medium relate to the technical field of satellite navigation, and the method comprises the following steps: when the short message terminal cannot receive a short message downlink signal broadcasted by a satellite end or the quality of the received short message downlink signal is lower than a preset quality threshold value, sending a short message to the satellite end; calculating visual satellites of the short message terminal at the current position to obtain a to-be-selected satellite set; obtaining all accessible satellites of the global short message system, which are determined in advance according to the prior information, and obtaining an accessible satellite set; the prior information represents whether each satellite with the short message access capability allows the short message terminal to access or not; determining an intersection of the visual satellite set and the accessible satellite set; determining an uplink access satellite from the intersection, and assembling an inbound message frame based on a synchronization head of the uplink access satellite; and sending the inbound message frame. The function of non-downlink signal blind sending of the short message is realized, and the function of the short message system is enriched.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation technology, and in particular to a method, a short message terminal and a medium for sending a short message. Background Art

[0002] The short message function is a two-way message communication function unique to the Beidou satellite navigation system, which can support users to communicate short messages through Beidou satellites and realize two-way data transmission. When users are in remote mountainous areas, oceans, deserts and other areas without mobile communication signal coverage, through the short message function, users can send message communication information and location report information to other Beidou users or command centers, and can also receive replies from other users or command centers. This can not only be used for daily communication and emergency rescue, but also for special application fields such as material airdrop, spacecraft wreckage search, aircraft track report, and missile landing position feedback.

[0003] According to the service coverage area, the short message system can be divided into Regional Short Message Communication (RSMC) and Global Short Message Communication Service (GSMC). The regional short message system can provide short message services for my country and surrounding areas, while the global short message communication can provide short message services for users worldwide.

[0004] In practice, the user's terminal device may be unable to receive the downlink signal from the satellite or the quality of the received downlink signal may be poor due to various factors, resulting in the terminal device being unable to obtain the parameter information of the uplink accessible satellite. In response to this situation, the regional short message system has designed a short message blind transmission mechanism without downlink signal. As long as the terminal device is located in the service coverage area of ​​the regional short message system, it can send short messages that can be successfully received by the satellite without downlink signal. For the global short message system, the blind transmission mechanism without downlink signal is not yet supported. Summary of the invention

[0005] Embodiments of the present application provide a method for sending a short message, a short message terminal, and a medium.

[0006] In a first aspect, an embodiment of the present application provides a method for sending short messages, which is applied to a short message terminal in a Beidou satellite navigation system, and the method includes: when the short message terminal cannot receive the short message downlink signal broadcast by the satellite or the quality of the received short message downlink signal is lower than a preset quality threshold, calculating the visible satellites of the short message terminal at the current position to obtain a set of satellites to be selected; obtaining all accessible satellites of the global short message system determined in advance based on prior information to obtain an accessible satellite set; the prior information indicates whether the satellite with short message access capability allows the short message terminal to access; determining the intersection of the visible satellite set and the accessible satellite set; determining the uplink access satellite from the intersection, and assembling an inbound message frame based on the synchronization header of the uplink access satellite; and sending the inbound message frame.

[0007] In the second aspect, an embodiment of the present application provides a short message terminal, which is applied to the Beidou satellite navigation system. When the short message terminal cannot receive the short message downlink signal broadcast by the satellite or the quality of the received short message downlink signal is lower than a preset quality threshold, the short message terminal sends an inbound message frame based on the method for sending short messages in the above embodiment.

[0008] In a third aspect, an embodiment of the present application provides a non-volatile computer storage medium, which stores a computer program. When the computer program is executed by a processor, the method for sending a short message in the above embodiment is implemented.

[0009] The method for sending short messages in the embodiment of the present application, when the short message terminal cannot receive the short message downlink signal broadcast by the satellite end or the quality of the received short message downlink signal is lower than the preset quality threshold, calculates the visible satellites of the short message terminal at the current position and all the accessible satellites of the short message system determined in advance based on prior information, and then determines the currently visible and accessible satellites based on the intersection of the visible satellite set and the accessible satellite set; then determines the uplink access satellite from the intersection, assembles the inbound telegram frame based on the synchronization header of the uplink access satellite and sends it. For global short message terminals or regional short message terminals located at the border of the service area, short messages that can be received by the satellite end can be sent in the absence of downlink signals or poor reception of downlink signals, realizing the blind sending function of short messages without downlink signals and enriching the functions of the short message system.

[0010] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0012] Figure 1 A schematic diagram of the architecture of an embodiment of the BeiDou satellite navigation system of the present application; Figure 2 A flowchart of an embodiment of a method for sending a short message of the present application; Figure 3 A flowchart of another embodiment of the method for sending a short message of the present application; Figure 4 A schematic diagram of a process of determining an uplink access satellite in one embodiment of a method for sending a short message of the present application; Figure 5 A schematic diagram of a process for obtaining prior information in an embodiment of a method for sending a short message of the present application; Figure 6 A flowchart of another embodiment of the method for sending a short message of the present application is shown. DETAILED DESCRIPTION

[0013] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0014] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0015] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0016] Figure 1 The schematic diagram of the architecture of the Beidou navigation system of the present application is shown as follows: Figure 1 As shown, the Beidou navigation system may include multiple satellites, including MEO (Medium Earth Orbit) satellites and IGSO (Inclined Geosynchronous Orbit) satellites, and different satellites may communicate with each other through intersatellite links. Satellites may broadcast a variety of downlink frequency signals to terminal devices, including global short message downlink signals including B2b frequency and other non-global short message downlink signals. Terminal devices may transmit uplink signals to accessible satellites, which are then forwarded to other satellites via intersatellite links, and finally reach other terminal devices or ground central stations. Terminal devices may be, for example, cars, aircraft, or smart phones equipped with global short message terminals or regional short message terminals. For regional short message terminals, in some specific cases, the uplink of the global short message terminal may be used as a global short message transmitting device.

[0017] Usually, the satellites that provide uplink access services for global short message terminals are MEO satellites. The characteristics of MEO satellites are that the satellite identification, elevation information, carrier-to-noise ratio, number and other parameter information of the visible satellites of the terminal equipment change with the rise and fall of the satellites. Moreover, among the 24 MEO satellites of BeiDou-3, only 14 have GSMC uplink access capabilities. In addition, after the MEO satellites accessible in GSMC receive the uplink signal sent by the GSMC terminal (i.e., the global short message terminal), they need to process it and then forward it. When the GSMC terminal cannot effectively receive the short message downlink signal, it will not be able to obtain the satellite number, elevation angle, carrier-to-noise ratio and other parameter information of the accessible MEO satellite, and it will not be able to generate a valid message frame synchronization header. In this case, even if the GSMC terminal sends a message frame, it is difficult for the satellite end to successfully receive it.

[0018] In order to realize the blind transmission function of short message terminal without downlink signal, the present application proposes a method for sending short message, which can be used for short message terminal in Beidou navigation system, such as Figure 2 As shown, the method may include the following steps.

[0019] Step 210: When the short message terminal cannot receive the short message downlink signal broadcast by the satellite or the quality of the received short message downlink signal is lower than a preset quality threshold, the visible satellites of the short message terminal at the current position are calculated to obtain a set of satellites to be selected.

[0020] In this embodiment, the short message downlink signal refers to the B2b frequency signal broadcast by the satellite providing GSMC service. The no downlink signal state means that the short message downlink signal broadcast by the satellite terminal cannot be received or the quality of the received short message downlink signal is lower than the preset quality threshold. It should be noted that when the short message terminal is in the no downlink signal state, other downlink signals other than the short message downlink signal can still be captured.

[0021] The quality of the short message downlink signal is lower than the preset quality threshold, which means that the short message terminal cannot determine whether the MEO satellite is uplink accessible and whether it is the best access satellite based on the short message downlink signal. For example, the global short message terminal cannot accurately identify all the information of the satellite based on the short message downlink signal: the satellite identification (i.e., the satellite's unique number), elevation angle, carrier-to-noise ratio of the frequency point corresponding to the short message downlink signal, etc.

[0022] In this embodiment, when the short message terminal is in a state of no downlink signal, the visible satellite at the current position can be identified according to other downlink signals captured by the short message terminal, a set of satellites to be selected can be obtained, and the identifier, elevation angle and other parameter information of the visible satellite at the current position can be determined. For example, the other downlink signal can be a RNSS (Radio Navigation Satellite Service) frequency signal broadcast by the MEO satellite.

[0023] Here, the short message terminal can identify it based on other downlink signals it has captured, or other Beidou RNSS terminals can calculate the identification and parameter information of the satellite broadcasting the downlink signal based on the received RNSS frequency signal, and then inject the calculated satellite identification and parameter information into the short message terminal as a visible satellite for the short message terminal.

[0024] In some optional implementations of this embodiment, the visible satellites at the current position of the short message terminal can also be estimated through simulation. For example, STK (Systems Tool Kit) or other commercial simulation software can be used to take the current position (i.e., the location of the short message terminal) as the observation point, and the visible satellites at the current position can be estimated through constellation simulation, and the parameter information of the visible satellites can be determined.

[0025] In this embodiment, constellation simulation can be used to estimate the visible satellites at the current position of the short message terminal in the absence of a downlink signal. This is particularly suitable for some specific scenarios. For example, when the short message terminal can neither receive a short message downlink signal nor capture other downlink signals, this method can be used to estimate the visible satellites at the current position.

[0026] Step 220: Acquire all accessible satellites of the global short message system determined in advance based on prior information to obtain an accessible satellite set.

[0027] The prior information represents whether each satellite with short message access capability allows short message terminals to access.

[0028] As an example, the prior information may include the identifiers of all MEO satellites and information on whether each MEO satellite is accessible, which can be monitored when the short message terminal is in a normal receiving state. The short message terminal can determine all accessible MEO satellites in advance based on the prior information as an accessible satellite set, and then pre-store the accessible satellite set in a local flash memory or other device. When the short message terminal is in a state without a downlink signal, the accessible satellite set can be obtained from the local flash memory or other device.

[0029] Step 230: Determine the intersection of the set of satellites to be selected and the set of accessible satellites.

[0030] In this embodiment, the satellites in the intersection of the candidate satellite set and the accessible satellite set represent satellites that are currently visible to the short message terminal and uplink accessible (ie, MEO satellites with uplink access capability).

[0031] Step 240: Determine the uplink access satellite from the intersection, and assemble the inbound message frame based on the synchronization header of the uplink access satellite.

[0032] As an example, a satellite may be randomly selected from the intersection as an uplink access satellite, or one or more satellites with higher parameters (eg, elevation angle, carrier-to-noise ratio) may be selected from the intersection as uplink access satellites.

[0033] In this embodiment, step 210, step 220, step 230 and the step of determining the uplink access satellite from the intersection can be executed by the short message terminal itself, or by other devices, and then the identification and parameter information of the determined uplink access satellite are sent to the short message terminal, and the short message terminal assembles an inbound message frame based on the synchronization header of the uplink access satellite.

[0034] Step 250: Send an inbound message frame.

[0035] In this embodiment, the synchronization header of the incoming message frame corresponds to the uplink access satellite, which can ensure that the short message terminal is successfully received by the uplink access satellite after sending the message frame, thereby realizing the blind sending mechanism of the short message terminal in the state of no downlink signal.

[0036] The method for sending short messages in this embodiment, when the short message terminal cannot receive the short message downlink signal broadcast by the satellite end or the quality of the received short message downlink signal is lower than the preset quality threshold, determines the visible satellites of the short message terminal at the current position and all the satellites that the short message terminal can access determined in advance based on prior information, and then determines the currently visible and accessible satellites based on the intersection of the visible satellite set and the accessible satellite set; then determines the uplink access satellite from the intersection, assembles the inbound message frame based on the synchronization header of the uplink access satellite and sends it. This allows the short message terminal to send short messages that can be received by the satellite end when there is no downlink signal or the downlink signal is poorly received, realizes the blind sending function of the short message without downlink signal, and enriches the function of the short message system.

[0037] Figure 3 A flow chart of an embodiment of a method for sending a short message of the present application is shown as follows: Figure 3 As shown, the process may include the following steps.

[0038] Step 310: When the short message terminal cannot receive the short message downlink signal sent by the satellite or the quality of the received short message downlink signal is lower than a preset quality threshold, the visible satellites of the short message terminal at the current position are calculated to obtain a set of satellites to be selected.

[0039] Step 320: Determine parameter information of visible satellites.

[0040] The parameter information of the visible satellite includes the elevation angle information of the visible satellite and the carrier-to-noise ratio of the frequency point corresponding to the short message downlink signal.

[0041] In this embodiment, the frequency corresponding to the short message downlink signal is the B2b frequency.

[0042] As an example, constellation simulation can be used to identify visible satellites and their parameter information.

[0043] Step 330: Acquire all the accessible satellites of the global short message system determined in advance based on prior information to obtain an accessible satellite set.

[0044] Step 340: Determine the intersection of the visible satellite set and the accessible satellite set.

[0045] Step 350: Determine the uplink access satellite based on the parameter information of each satellite in the intersection.

[0046] As an example, the satellite with the highest weighted sum of one or more parameters in the intersection may be used as the uplink access satellite.

[0047] Step 360: Assemble the inbound message frame based on the synchronization header of the uplink access satellite.

[0048] Step 370: Send an inbound message frame.

[0049] In this embodiment, an uplink access satellite can be selected based on the satellite parameter information, which helps to select a more reliable visible satellite as the uplink access satellite and helps to improve the success rate of receiving the inbound message frame.

[0050] In some embodiments, the above step 350 can also be performed by Figure 4 The process shown determines the uplink access satellite, such as Figure 4 As shown, the process may include the following steps.

[0051] Step 410: Based on the parameter information of each satellite in the intersection, determine the satellite with the highest carrier-to-noise ratio as a candidate access satellite.

[0052] In this embodiment, the carrier-to-noise ratio refers to the carrier-to-noise ratio of the satellite at the frequency point corresponding to the short message downlink signal (ie, the B2b frequency point), which can represent the signal quality of the short message downlink signal.

[0053] Step 420: When the number of candidate access satellites is 1, the candidate access satellite is used as an uplink access satellite.

[0054] Step 430: When the number of candidate access satellites is greater than 1, the candidate access satellite with the largest elevation angle is used as the uplink access satellite.

[0055] As an example, the satellites can be sorted according to the carrier-to-noise ratio of each satellite in the intersection, and one or more candidate access satellites with the highest carrier-to-noise ratio can be determined. If there is only one candidate access satellite, it is determined as the uplink access satellite; if there are multiple candidate access satellites, the multiple candidate access satellites can be sorted according to the elevation angle, and the candidate access satellite with the largest elevation angle can be determined as the uplink access satellite.

[0056] exist Figure 4In the illustrated embodiment, a satellite with a higher carrier-to-noise ratio may be preferentially selected as an uplink access satellite. When there are multiple candidate access satellites with the highest and same carrier-to-noise ratio, the candidate access satellite with the largest elevation angle is first selected as the uplink access satellite, and then the satellite with better downlink signal quality is selected as the uplink access satellite of the short message terminal, thereby improving the success rate of receiving inbound message frames.

[0057] Next reference Figure 5 , Figure 5 FIG. 1 shows a flow chart of obtaining prior information in an embodiment of a method for sending a short message of the present application. Figure 5 As shown, the process may include the following steps.

[0058] Step 510: Under preset conditions, the short message terminal is used to perform reception monitoring of the short message downlink signal sent by each satellite for a preset time period to obtain an observation value of each satellite at a frequency point corresponding to the short message downlink signal.

[0059] In this embodiment, the preset condition indicates that the short message terminal can normally receive the B2b frequency signal broadcast by each MEO satellite. The preset duration is usually not less than one week.

[0060] Step 520: Perform message parsing and positioning based on the observation amount of each satellite at the frequency point corresponding to the short message downlink signal to test whether each satellite allows the short message terminal to access and obtain the test result.

[0061] As an example, when the short message terminal is in a normal receiving state, the short message downlink signals broadcast by 24 MEO satellites can be received and monitored to obtain the B2b frequency point observation quantity of each MEO satellite. Then, according to the B2b frequency point observation quantity of each MEO satellite, the message is parsed and the positioning is solved to monitor whether the MEO satellite is accessible uplink, until all 24 MEO satellites are monitored and the monitoring results of 24 MEO satellites are obtained.

[0062] Step 530: Generate prior information based on the monitoring results.

[0063] The prior information includes the identifier of each satellite and the identifier of whether each satellite is accessible.

[0064] In this embodiment, after the monitoring is completed, each satellite can be marked as accessible according to the monitoring result to obtain prior information. After that, it is only necessary to filter out the identifiers of the satellites that can be accessed according to the identifiers of whether they can be accessed, and then the set of satellites to be selected can be obtained.

[0065] Step 540: Update the prior information according to a preset period.

[0066] In practice, as the BeiDou navigation system operates, the identification and access status of MEO satellites may change. To ensure the accuracy of the prior information, the prior information may be updated periodically. For example, the preset period may be one month.

[0067] In this embodiment, prior information can be generated based on the monitoring results of each satellite during normal operation of the short message terminal and updated regularly to ensure the accuracy of the prior information, thereby ensuring that the short message terminal can accurately determine the accessible satellite based on the prior information.

[0068] Figure 6 A flow chart of an embodiment of a method for sending a short message of the present application is shown as follows: Figure 6 As shown, the process may include the following steps.

[0069] Step 600: When the short message terminal cannot receive the short message downlink signal broadcast by the satellite or the quality of the received short message downlink signal is lower than a preset quality threshold, the identifier of the satellite broadcasting the non-short message downlink signal is determined according to the non-short message downlink signal captured by the short message terminal at the current position, as a visible satellite, to obtain a set of satellites to be selected.

[0070] In this embodiment, the non-short message downlink signal refers to other downlink signals other than the B2b frequency signal broadcast by the satellite, for example, it can be a downlink signal broadcast by a MEO satellite or other GNSS satellite at the B1I frequency, B1C frequency, B2a frequency or B3Q frequency.

[0071] Step 610: Determine the carrier-to-noise ratio and the observed value of the satellite that broadcasts the non-short message downlink signal at the frequency point corresponding to the non-short message downlink signal according to the non-short message downlink signal.

[0072] Step 620: The carrier-to-noise ratio of the frequency point corresponding to the non-short message downlink signal is used as the carrier-to-noise ratio of the frequency point corresponding to the short message downlink signal of the satellite that broadcasts the non-short message downlink signal.

[0073] As an example, the short message terminal can obtain the carrier-to-noise ratio of a certain MEO satellite at the B1I frequency point through step 620, and can use the carrier-to-noise ratio of the MEO satellite at the B1I frequency point as the carrier-to-noise ratio of the MEO satellite at the B2b frequency point. In this way, it can be ensured that the non-short message downlink signal captured by the short message terminal and the short message downlink signal that may be received subsequently come from the same MEO satellite, so that the carrier-to-noise ratio of the non-short message downlink signal and the short message downlink signal that may be received subsequently have the same reference value, and it can be ensured that the elevation angle information of the MEO satellite can be replaced.

[0074] Step 630: Perform positioning calculation based on the observed value to determine the elevation angle information of the satellite that broadcasts the non-short message downlink signal.

[0075] Step 640: Determine parameter information of visible satellites.

[0076] The parameter information of the visible satellite includes the elevation angle information of the satellite and the carrier-to-noise ratio of the frequency point corresponding to the short message downlink signal.

[0077] In this embodiment, through steps 610 to 640, visible satellites and their parameter information can be determined according to the non-short message downlink signal captured by the short message terminal.

[0078] Step 650: Acquire all the accessible satellites of the global short message system determined in advance based on prior information to obtain an accessible satellite set.

[0079] Step 660: Determine the intersection of the visible satellite set and the accessible satellite set.

[0080] Step 670: Determine the uplink access satellite based on the parameter information of each satellite in the intersection.

[0081] As an example, one can use Figure 4 The process shown determines the uplink access satellite.

[0082] Step 680: Assemble the inbound message frame based on the synchronization header of the uplink access satellite.

[0083] Step 690: Send an inbound message frame.

[0084] Figure 6 In the embodiment shown, when the short message terminal is in a state of no downlink signal, the visible satellite and its parameter information can be determined more accurately based on the non-short message downlink signal captured by the short message terminal, and then the uplink access satellite can be determined in combination with the accessible satellite set, and the corresponding inbound message frame can be generated, which helps to further improve the success rate of receiving the inbound message frame.

[0085] An embodiment of the present application also provides a short message terminal, which is applied to the Beidou satellite navigation system. When the short message terminal cannot receive the short message downlink signal broadcast by the satellite or the quality of the received short message downlink signal is lower than a preset quality threshold, the short message terminal sends an inbound message frame based on the method for sending short messages in any of the above embodiments.

[0086] In this embodiment, the short message terminal may be a global short message terminal, or may also be a regional short message terminal located at the border of a service area or beyond the service area.

[0087] Among them, the short message terminal is a global short message terminal, which can realize blind sending of global short messages without downlink signals; when the short message terminal is a regional short message terminal located at the boundary of the service area or beyond the service area, the regional short message function is likely to fail, and the uplink hardware link in the global short message terminal can be borrowed to realize blind sending of global short messages without downlink signals as a global short message transmitting device.

[0088] An embodiment of the present application further provides a non-transitory computer storage medium, which stores a computer program. In some embodiments, when the computer program is executed by a processor, the method for sending a short message in any of the above embodiments is implemented.

[0089] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or transient medium). As is known to those skilled in the art, the term "computer storage medium" includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A method for sending a short message, applied to a short message terminal in a Beidou satellite navigation system, characterized in that: include: When the short message terminal cannot receive the short message downlink signal broadcast by the satellite terminal or the quality of the received short message downlink signal is lower than a preset quality threshold, calculating the visible satellites of the short message terminal at the current position to obtain a set of satellites to be selected; Acquire all accessible satellites of the global short message system determined in advance according to prior information to obtain an accessible satellite set; the prior information indicates whether the satellite with short message access capability allows the short message terminal to access; Determine an intersection of the set of satellites to be selected and the set of accessible satellites; Determine an uplink access satellite from the intersection, and assemble an inbound message frame based on a synchronization header of the uplink access satellite; The inbound message frame is sent.

2. The method according to claim 1, characterized in that Determining an uplink access satellite from the intersection includes: determining parameter information of each satellite in the intersection, the parameter information including elevation angle information and a carrier-to-noise ratio of a frequency point corresponding to a short message downlink signal; and, The uplink access satellite is determined based on the parameter information of each satellite in the intersection.

3. The method according to claim 2, characterized in that Determining the uplink access satellite based on the parameter information of each satellite in the intersection includes: Based on the parameter information of each satellite in the intersection, the satellite with the highest carrier-to-noise ratio is selected as a candidate access satellite; When the number of the candidate access satellites is 1, using the candidate access satellite as the uplink access satellite; When the number of the candidate access satellites is greater than 1, the candidate access satellite with the largest elevation angle is used as the uplink access satellite.

4. The method according to claim 1, characterized in that: The prior information is determined in the following way: Under preset conditions, using the short message terminal to perform reception monitoring of the short message downlink signal broadcast by each satellite for a preset time length, so as to obtain an observation amount of each satellite at a frequency point corresponding to the short message downlink signal; Based on the observation amount of each satellite at the frequency point corresponding to the short message downlink signal, the telegram parsing and positioning calculation are performed to monitor whether each satellite allows the short message terminal to access, and obtain a monitoring result; Based on the monitoring test result, the prior information is generated; the prior information includes an identifier of each satellite and an identifier corresponding to each satellite indicating whether it is accessible; as well as, The prior information is updated according to a preset period.

5. The method according to claim 1, characterized in that Calculating visible satellites of the short message terminal at the current position, comprising: The current position is used as an observation point, the visible satellites are estimated through constellation simulation, and parameter information of the visible satellites is determined.

6. The method according to claim 1, characterized in that Calculating visible satellites of the short message terminal at the current position, comprising: According to the non-short message downlink signal captured by the short message terminal at the current position, the identifier of the satellite that broadcasts the non-short message downlink signal is determined as the visible satellite.

7. The method according to claim 6, characterized in that After determining the identifier of the satellite that broadcasts the non-short message downlink signal, the method includes: Determine, according to the non-short message downlink signal, a carrier-to-noise ratio and an observation amount of a satellite that broadcasts the non-short message downlink signal at a frequency point corresponding to the non-short message downlink signal; Using the carrier-to-noise ratio of the frequency point corresponding to the non-short message downlink signal as the carrier-to-noise ratio of the frequency point corresponding to the short message downlink signal of the satellite that broadcasts the non-short message downlink signal; Performing positioning calculation based on the observed quantity to determine the elevation angle information of the satellite that broadcasts the non-short message downlink signal; Determine parameter information of the visible satellite, wherein the parameter information of the visible satellite includes elevation angle information of the satellite and a carrier-to-noise ratio of a frequency point corresponding to the short message downlink signal.

8. A short message terminal, applied to Beidou satellite navigation system, characterized in that: When the short message terminal cannot receive the short message downlink signal broadcast by the satellite or the quality of the received short message downlink signal is lower than a preset quality threshold, the short message terminal sends an inbound message frame based on the method for sending short messages described in one of claims 1 to 7.

9. The short message terminal according to claim 8, characterized in that: The short message terminal is a global short message terminal, or a regional short message terminal located at the border of a service area or beyond the service area.

10. A non-transitory computer storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for sending a short message according to any one of claims 1 to 7 is implemented.

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