Beidou short message communication method applied to GNSS satellite common view

Abstract

The application discloses a Beidou short message communication method applied to GNSS satellite common viewing, when data fitting collection of the Nth group of satellite common viewing data is finished, core data of the Nth group of satellite common viewing data is extracted for compression, Beidou short message communication is completed before data fitting collection of the N+1th group of satellite common viewing data, transmission of the compressed core data of the Nth group of satellite common viewing data is completed, and N is a positive integer; before data fitting collection of the N+1th group of satellite common viewing data, transmission of the compressed core data of the Nth group of satellite common viewing data is completed for 2-3 times; the application completes communication transmission in the interval between the generation of two groups of common viewing data, can avoid interference of Beidou short message communication on GNSS receiving signals, and improves common viewing data comparison accuracy.

Description

Technical Field

[0001] This invention relates to the field of time and frequency transmission technology in satellite navigation, specifically to a BeiDou short message communication method applied in GNSS satellite common-view communication. Background Technology

[0002] Time is one of the most fundamental physical quantities internationally, playing a vital role in everyday life, scientific research, aerospace, national economy, and defense. Standard time and frequency standards are the "heart" of various electronic devices, ensuring their accurate and reliable operation. With the rapid development of informatization, intelligentization, and the Internet of Things, and to meet national science and technology development plans and needs, many fields are placing great emphasis on research and the development of related service capabilities in the field of time and frequency. Over the past 20 years, the improvement in time and frequency accuracy has shown an exponential trend, increasing by an order of magnitude approximately every 5 to 10 years.

[0003] In fields such as power, communications, finance, public security, transportation, and the internet, precise time and frequency synchronization are crucial. Currently, high-precision long-distance time and frequency transmission technologies mainly include GNSS satellite common-view time and frequency transmission, satellite two-way time and frequency transmission, and fiber optic time and frequency transmission. The most mature and widely used technology currently is the GNSS navigation satellite common-view comparison method for long-distance time and frequency transmission. Using satellite common-view allows for real-time time and frequency comparison and remote tracing, requiring the establishment of a data transmission link between two satellite common-view devices. Currently, wired networks or 4G / 5G wireless networks are generally used for data transmission, which is not suitable for high-security fields such as national defense, power, and communications.

[0004] The BeiDou Navigation Satellite System (BDS) is a global satellite navigation system independently developed by China. It is the third mature satellite navigation system after GPS and GLONASS, possessing navigation, positioning, and timing functions, as well as short message transmission capabilities. With the completion of the BeiDou-3 system in 2020 providing global services, the BDS will be widely applied in various fields. This invention utilizes BeiDou's short message communication function for data transmission in GNSS common-view time-frequency transmission, providing a new method for fields with high security requirements such as national defense, power, and communications. However, the transmission frequency of BeiDou short message communication (L-band uplink frequency) is relatively close to the GNSS receiving frequency (L-band, 1.2GHz~1.6GHz). When the antennas are close together, it affects the reception of GNSS satellites, resulting in discontinuous and jittery GNSS common-view data (CGGTTS standard format). Furthermore, the large data volume of GNSS common-view data (CGGTTS standard format) makes timely and efficient transmission impossible. Therefore, BeiDou short message communication suffers from signal interference, resulting in low communication success rate and poor common-view accuracy, and it cannot transmit GNSS satellite common-view data in a timely and efficient manner. Summary of the Invention

[0005] The purpose of this invention is to provide a BeiDou short message communication method for GNSS satellite common-view communication, aiming to improve the problems of low communication success rate and poor common-view accuracy caused by signal interference in the existing BeiDou short message transmission of satellite common-view data, as well as the inability to transmit GNSS satellite common-view data in a timely and efficient manner.

[0006] To achieve the above objectives, this invention provides a BeiDou short message communication method applied to GNSS satellite common-view data. When the data fitting and acquisition of the Nth group of satellite common-view data is completed, the core data of the Nth group of satellite common-view data is extracted and compressed, and BeiDou short message communication is completed before the data fitting and acquisition of the N+1th group of satellite common-view data, thus completing the transmission of the core data of the compressed Nth group of satellite common-view data, where N is a positive integer.

[0007] Furthermore, before acquiring the data fitting data of the N+1th group of satellite common-view data, the core data of the Nth group of satellite common-view data, which has been compressed, is transmitted 2-3 times.

[0008] Furthermore, after extracting and compressing the core data of the Nth group of satellite common-view data, the core data of the compressed Nth group of satellite common-view data is transmitted for the first time after a delay of X1 minutes. After the first transmission is completed, the core data of the compressed Nth group of satellite common-view data is transmitted for the second time after a delay of X2 minutes. X1+X2≤2 minutes, and X1 is not zero and X2 is not less than 1 minute.

[0009] Furthermore, after extracting and compressing the core data of the Nth group of satellite common-view data, the core data of the compressed Nth group of satellite common-view data is transmitted for the first time after a delay of Y1 minutes. After the first transmission is completed, the core data of the compressed Nth group of satellite common-view data is transmitted for the second time after a delay of Y2 minutes. Finally, the core data of the compressed Nth group of satellite common-view data is transmitted for the third time after a delay of Y3 minutes. Y1+Y2+Y2≤2 minutes10 seconds, and Y1 is not zero, while Y2 and Y3 are both not less than 1 minute.

[0010] Furthermore, after extracting and compressing the core data of the Nth group of satellite common-view data, the core data of the compressed Nth group of satellite common-view data is transmitted for the first time after a 10-second delay. After the first transmission is completed, the core data of the compressed Nth group of satellite common-view data is transmitted for the second time after a 1-minute delay. Finally, the core data of the compressed Nth group of satellite common-view data is transmitted for the third time after a 1-minute delay.

[0011] Furthermore, after extracting the core data from the Nth group of satellite common-view data and compressing it, the compressed data packet is less than 76 bytes.

[0012] Furthermore, the core data of the satellite common-view data includes the satellite number, the start tracking time, and the time deviation between the local clock and the satellite system after correcting for satellite clock bias.

[0013] Furthermore, the compressed data includes shared data from four satellite systems: GPS, GLONASS, BeiDou, and Galileo.

[0014] Furthermore, the compressed data may also include clock bias data calculated using single-frequency pseudorange or clock bias data calculated using dual-frequency combined pseudorange.

[0015] Furthermore, when the number of valid satellites exceeds 18, satellites with higher elevation angles are given priority.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. This invention completes communication transmission within the gap between the generation of two sets of common-view data, which can avoid interference of BeiDou short message communication on GNSS received signals and improve the accuracy of common-view data comparison.

[0018] 2. Extract core data from standard format common-view data and re-encode it to achieve data compression. Compress each set of effective satellite clock difference data into 76 bytes and complete 3 cyclic transmissions within 3 minutes. This not only reduces the amount of data to be transmitted, facilitating timely and efficient transmission, but also improves the success rate of BeiDou short message transmission of common-view data, achieving more reliable data communication.

[0019] 3. Compared with traditional methods of transmitting satellite co-view data using wired networks or 4G networks, BeiDou short message communication is more secure and can be applied in fields with higher security requirements, such as national defense, power, and communications. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention;

[0021] Figure 2 This is a flowchart illustrating Embodiment 2 of the present invention;

[0022] Figure 3 This is a data transmission encoding table for GNSS common-view data. Detailed Implementation

[0023] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] To make the features and advantages of the present invention clearer, the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0025] Example 1

[0026] A BeiDou short message communication method applied in GNSS satellite co-viewing, such as Figure 1As shown, when the data fitting and acquisition of the previous set of satellite common-view data ends, the core data of the previous set of satellite common-view data is extracted and compressed. The core data of the satellite common-view data is the main data used for time-frequency comparison between the two common-view devices, including satellite number, starting tracking time, and the time deviation between the local clock and the satellite system after correcting the satellite clock bias. This core data needs to be packaged and compressed. The packaged and compressed data includes common-view data from four satellite systems: GPS, GLONASS, BeiDou, and Galileo. It may also include clock bias data calculated by single-frequency pseudorange or clock bias data calculated by dual-frequency combined pseudorange, which can be flexibly selected by the user according to the actual equipment used. After the core data of the previous set of satellite common-view data is packaged and compressed, the compressed core data of the previous set of satellite common-view data is transmitted for the first time after a 30-second delay. After the first transmission is completed, the compressed core data of the previous set of satellite common-view data is transmitted for the second time after a 1 minute and 20 second delay. Therefore, in this embodiment, from the extraction and packaging of the core data of the previous set of satellite common-view data to the data fitting and acquisition of the current set of satellite common-view data, a total of two transmissions of the compressed core data of the previous set of satellite common-view data are completed.

[0027] Example 2

[0028] A BeiDou short message communication method applied in GNSS satellite co-viewing, such as Figure 2 As shown, after the data fitting and acquisition of the previous set of satellite common-view data is completed, the core data of the previous set of satellite common-view data is extracted and compressed. The core data of the satellite common-view data is the main data used for time and frequency comparison between the two common-view devices, including satellite number, starting tracking time, and the time deviation between the local clock and the satellite system after correcting the satellite clock bias. This core data needs to be packaged and compressed. The packaged and compressed data includes common-view data from four satellite systems: GPS, GLONASS, BeiDou, and Galileo. It may also include clock bias data calculated by single-frequency pseudorange or dual-frequency combined pseudorange, which can be flexibly selected by the user according to the actual equipment used. After the core data of the previous set of satellite common-view data is packaged and compressed, there is a 10-second delay before the first transmission of the compressed core data of the previous set of satellite common-view data. After the first transmission, there is another 1-minute delay before the second transmission of the compressed core data of the previous set of satellite common-view data. After the second transmission, there is another 1-minute delay before the second transmission of the compressed core data of the previous set of satellite common-view data. Finally, there is a 1-minute delay before the third transmission of the compressed core data of the previous set of satellite common-view data. Therefore, in this embodiment, from the extraction and compression of the core data of the previous set of satellite common-view data to the data fitting and acquisition of the current set of satellite common-view data, a total of 2 transmissions of the compressed core data of the previous set of satellite common-view data are completed.

[0029] The working principle of this invention: The CGGTTS data format is a standard data format for GNSS code-based time and frequency transmission, developed by the GNSS Time and Frequency Standards Working Group of the International Time and Frequency Consultative Committee. The standard CGGTTS format for GNSS common-view data includes satellite number, start tracking time, elevation angle, azimuth angle, local clock time deviation from the satellite system (uncorrected satellite clock bias), local clock time deviation from the satellite system (corrected satellite clock bias), tropospheric delay, ionospheric delay, etc. GNSS satellite common-view requires the exchange of common-view data between two receivers to achieve time and frequency comparison and transmission. The core data mainly used by the two common-view devices for time and frequency comparison are the satellite number, start tracking time, and local clock time deviation from the satellite system (corrected satellite clock bias). This data needs to be packaged and compressed. The packaged and compressed data includes common-view data from the four satellite systems GPS, GLONASS, BeiDou, and Galileo, as well as clock bias data calculated using single-frequency pseudorange or dual-frequency combined pseudorange, which can be flexibly selected by the user according to the actual equipment used. The data transmission encoding table is as follows. Figure 3 As shown in the table, Data Area 1 and Data Area 2 generally use a combination of GPS and BeiDou dual-frequency pseudorange GPS L1P&L2P and BeiDou B1I&B2I for transmission, which can meet most of the current requirements for time and frequency transmission for common-view satellites. Each Data Area 1 and Data Area 2 can transmit clock bias data from a maximum of 18 valid satellites. If the number of valid satellites exceeds 18, they can be sorted by elevation angle, with priority given to satellites with higher elevation angles. The data in "Clock Bias Information of Data Area 1" and "Clock Bias Information of Data Area 2" are all signed integers, while the remaining data are unsigned integers, except for those defined as character types. The CGGTTS standard data format specifies that from the start tracking time of each set of common-view data, the first 2 minutes are satellite tracking time and are invalid data; the next 13 minutes are data acquisition time and are valid data; and the last minute is satellite tracking time and is also invalid data. To avoid interference between the high-power L-band uplink signal of BeiDou short message communication and the L-band receiving signal of GNSS during signal transmission, we choose to complete the BeiDou short message communication within a total of 3 minutes, specifically within the last minute of the previous set of common-view data and the first 2 minutes of the current set of common-view data. This avoids interference between the transmitted signal and the received signal during BeiDou short message communication. Currently, the commonly used BeiDou-2 short message communication operates at a frequency of 1 packet / minute and a rate of 76 bytes / packet, while BeiDou-3 short message communication has an increased rate. Typically, the success rate of a single BeiDou short message communication is around 95%. To achieve real-time, efficient, and reliable transmission of common-view data, this invention can complete up to 3 communication cycles within 3 minutes, with each communication transmitting a data packet compressed to within 76 bytes. The success rate of a single communication can reach 95%, and the probability of three consecutive unsuccessful communication attempts is as low as approximately 0.0125%.

[0030] In summary, compared with existing BeiDou short message transmission of satellite common-view data, this invention completes communication transmission within the interval between the generation of two sets of common-view data, avoiding interference of BeiDou short message communication with GNSS received signals and improving the accuracy of common-view data comparison. Core data is extracted from standard-format common-view data and re-encoded to achieve data compression, compressing each set of effective satellite clock difference data into 76 bytes and completing three cyclic transmissions within 3 minutes. This not only reduces the amount of data to be transmitted, facilitating timely and efficient transmission, but also improves the success rate of BeiDou short message transmission of common-view data, achieving more reliable data communication. Compared with traditional methods of transmitting satellite common-view data using wired networks or 4G networks, BeiDou short message communication is more secure and can be applied in fields with higher security requirements, such as national defense, power, and communications.

[0031] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A BeiDou short message communication method applied in GNSS satellite co-view, characterized in that, When the data fitting and acquisition of the Nth group of satellite common-view data is completed, the core data of the Nth group of satellite common-view data is extracted and compressed. Before the data fitting and acquisition of the N+1th group of satellite common-view data, the BeiDou short message communication is completed to complete the transmission of the core data of the compressed Nth group of satellite common-view data, where N is a positive integer.

2. The BeiDou short message communication method applied in GNSS satellite co-view as described in claim 1, characterized in that, Before acquiring and fitting data for the N+1th group of satellite common-view data, complete the transmission of the core data of the Nth group of satellite common-view data that has been compressed 2 to 3 times.

3. The BeiDou short message communication method applied in GNSS satellite co-view as described in claim 2, characterized in that, After extracting and compressing the core data of the Nth group of satellite common-view data, the core data of the compressed Nth group of satellite common-view data is transmitted for the first time after a delay of X1 minutes. After the first transmission is completed, the core data of the compressed Nth group of satellite common-view data is transmitted for the second time after a delay of X2 minutes. X1+X2≤2 minutes, and X1 is not zero and X2 is not less than 1 minute.

4. The BeiDou short message communication method applied in GNSS satellite co-view as described in claim 2, characterized in that, After extracting and compressing the core data of the Nth group of satellite common-view data, the core data of the compressed Nth group of satellite common-view data is transmitted for the first time after a delay of Y1 minutes. After the first transmission, the core data of the compressed Nth group of satellite common-view data is transmitted for the second time after a delay of Y2 minutes. Finally, the core data of the compressed Nth group of satellite common-view data is transmitted for the third time after a delay of Y3 minutes. Y1+Y2+Y3≤2 minutes10 seconds, and Y1 is not zero, while Y2 and Y3 are both not less than 1 minute.

5. The BeiDou short message communication method applied in GNSS satellite co-view as described in claim 4, characterized in that, After extracting and compressing the core data of the Nth group of satellite common-view data, the core data of the compressed Nth group of satellite common-view data is transmitted for the first time after a 10-second delay. After the first transmission is completed, the core data of the compressed Nth group of satellite common-view data is transmitted for the second time after a 1-minute delay. Finally, the core data of the compressed Nth group of satellite common-view data is transmitted for the third time after a 1-minute delay.

6. The BeiDou short message communication method applied in GNSS satellite co-view as described in claim 1, characterized in that, After extracting the core data from the Nth group of satellite common-view data and compressing it, the size of the compressed data packet is less than 76 bytes.

7. A BeiDou short message communication method applied in GNSS satellite co-viewing according to any one of claims 1-6, characterized in that, The core data of the satellite common-view data includes the satellite number, the start tracking time, and the time deviation between the local clock and the satellite system after correcting for satellite clock bias.

8. A BeiDou short message communication method applied in GNSS satellite co-view as described in claim 7, characterized in that, The compressed data includes shared data from four satellite systems: GPS, GLONASS, BeiDou, and Galileo.

9. A BeiDou short message communication method applied in GNSS satellite co-view as described in claim 8, characterized in that, The compressed data also includes clock bias data calculated using single-frequency pseudorange or clock bias data calculated using dual-frequency combined pseudorange.

10. A BeiDou short message communication method applied in GNSS satellite co-view as described in claim 7, characterized in that, When the number of valid satellites exceeds 18, select the satellite with the higher elevation angle.

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