A satellite selection method and storage medium for Beidou global short message service

Abstract

A satellite selection method and storage medium for Beidou global short message service, the satellite selection method comprising: receiving B2b signals of multiple Beidou satellites to obtain corresponding telegrams of each satellite; determining a set of satellites that can receive short message signals according to the corresponding telegrams of each satellite; comparing and sorting the B2b signal strengths of all satellites in the set; determining the visible relationship of all satellites in the set according to the current position; determining the data sending time; and selecting the satellite that is ultimately used to send the short message according to the B2b signal strength sorting, visible relationship, and data sending time of all satellites in the set. The storage medium stores computer program instructions, which, when loaded and run by a processor, cause the processor to execute the satellite selection method.

Description

Technical Field

[0001] The invention relates to a satellite selection method and a storage medium for Beidou global short message service, and belongs to the technical field of satellite communications. Background Art

[0002] my country's Beidou-3 satellite navigation system officially started providing services on July 31, 2021. In addition to providing navigation services, the Beidou satellite navigation system also provides short message communication services. The Beidou global short message communication system consists of user terminals, satellites, and ground central stations. The user terminal needs to select one of the visible Beidou satellites as the access satellite and send a short message inbound signal through the L band. After the satellite successfully receives the user's inbound signal, it forwards it to the satellite visible to the ground station through the intersatellite link and sends it to the ground station. The ground central station sends an outbound signal to the visible satellite, and the visible satellite forwards the outbound signal to the satellite visible to the user terminal through the intersatellite link, which is then sent to the user terminal via the B2b signal.

[0003] Generally speaking, users will be covered by multiple satellites. Therefore, the user terminal needs to select the satellite to access by itself to ensure the success rate of message reception and service time. Summary of the invention

[0004] The technical problem to be solved by the present invention is: when a Beidou global short message terminal is visible to multiple Beidou satellites, the terminal selects the satellite to access, thereby ensuring the success rate of message reception.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A satellite selection method for Beidou global short message service, comprising:

[0007] Receive multiple Beidou satellite B2b signals and obtain the corresponding message of each satellite;

[0008] According to the corresponding message of each satellite, determine the set of satellites that can receive short message signals;

[0009] Compare and sort the B2b signal strengths of all satellites in the set;

[0010] According to the current position, determine the visible relationship of all satellites in the set;

[0011] Determine the time when data is sent;

[0012] The satellite that is ultimately used to send the short message is selected based on the B2b signal strength ranking, visibility relationship, and data transmission time of all satellites in the set.

[0013] Preferably, it is determined whether a certain satellite has a short message function and is in a receivable state according to an inbound identifier of a corresponding message of the certain satellite.

[0014] Preferably, the position of the satellite is obtained through the satellite ephemeris in the message, and the visibility relationship is calculated based on the current position and the satellite position.

[0015] Preferably, the visible relationship includes a relative position relationship and a visible time.

[0016] Preferably, the method for selecting the satellite that is ultimately used to send the short message is:

[0017] Select satellites whose visible time is greater than the data transmission time;

[0018] If the visible time of multiple satellites is greater than the data transmission time, the satellite with the strongest B2b signal strength is selected.

[0019] Preferably, the user receiver calculates the coordinates of the corresponding satellite in the Beidou coordinate system based on the ephemeris parameters in the received satellite message.

[0020] Preferably, the user receiver evaluates the B2b signal strength of all satellites by a carrier-to-noise ratio calculation method.

[0021] Preferably, the user receiver calculates the observation elevation angle of the satellite and further determines the visible time.

[0022] Preferably, the user receiver determines the set of satellites that can receive short message signals according to the identifier in the B2b message; the access capability indication field in the message corresponds to two broadcasting states including:

[0023] Status 1: 00: This satellite has no access capability;

[0024] Status 2:01, this satellite has access capability.

[0025] A computer-readable storage medium stores computer program instructions, which, when loaded and executed by a processor, enable the processor to execute the satellite selection method for the Beidou global short message service.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention solves the problem of utilizing the integrated communication and navigation characteristics of the Beidou global short message communication system, realizing the optimization of uplink access satellites according to the downlink signal strength of the navigation satellite and the terminal positioning information, judging the quality of the satellite-to-ground link according to the downlink signal strength, and receiving the satellite ephemeris to calculate the relative position relationship and visible time between the satellite and the terminal; this method can simultaneously ensure the quality of short message transmission and reception and information transmission;

[0028] (2) Beidou satellites use B2b signals to broadcast Beidou global short message outbound information. Short message communication terminals receive short message outbound signals by receiving B2b frequency signals. The B2b center frequency is close to the Beidou short message inbound signal center frequency, so the signal propagation characteristics are similar. The signal strength of the B2b signal can accurately reflect the propagation conditions of the inbound signal transmitted by the terminal to the satellite. The present invention selects the satellite with the largest B2b signal strength as the access satellite, thereby ensuring good propagation conditions.

[0029] (3) After receiving the B2b signal, the Beidou global short message terminal demodulates and obtains the ephemeris information in the B2b signal, calculates the position of the satellite, and then calculates the distance between the terminal and the satellite, the observation elevation angle, and predicts the satellite position, and then calculates the visible time between the satellite and the terminal; the present invention selects the satellite with the longest visible time as the access satellite to ensure a longer communication time and thus transmit more data;

[0030] (4) The present invention makes full use of the design features of the Beidou satellite navigation system, occupies less resources and has good performance. It supports the joint design of the global short message terminal and the navigation terminal, realizes the reuse of radio frequency channels and antennas, and reduces the terminal size, weight and power consumption. It fully considers the typical scenarios of global short message communication, takes the content that the terminal needs to send and the corresponding communication duration as one of the constraints, and can provide users with a good communication experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of the steps of the present invention.

[0032] Figure 2 This is the B2b message format.

[0033] Figure 3 This is the satellite ephemeris format in the B2b message. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0035] A method for selecting satellites for Beidou global short message service, such as Figure 1 As shown, including:

[0036] Step 1: The user terminal receives navigation signals from multiple BeiDou satellites B2b and obtains the corresponding satellite messages;

[0037] Step 2: The user terminal determines the set of satellites that can receive short message signals according to the "access capability indication" in the message;

[0038] Step 3: The user terminal compares the B2b signal strength of each satellite in the set of satellites that can receive short message signals;

[0039] Step 4: The user terminal calculates the position of the corresponding satellite through different satellite ephemeris, and calculates the visibility relationship based on its own position and the satellite position, including the relative position relationship and visibility time;

[0040] Step 5: The user receiver calculates the data transmission time according to the amount of data it needs to send and the information transmission rate, and selects a satellite whose visibility time is longer than the data transmission time. If there are multiple satellites, the satellite with the strongest B2b signal strength is selected.

[0041] More specific:

[0042] Step 1: The user receiver receives multiple Beidou MEO satellite B2b signals and obtains the corresponding satellite message. The B2b message format is as follows: Figure 2 shown.

[0043] The format of the satellite ephemeris in the B2b message is as follows Figure 3 As shown in the figure, the satellite ephemeris consists of 18 quasi-Kepler orbit parameters and 1 satellite orbit type parameter. The ephemeris parameter definitions are shown in the table below. The user receiver can calculate the coordinates of the corresponding satellite (actually the satellite antenna phase center) in the Beidou coordinate system based on the received ephemeris parameters.

[0044] Step 2: The user receiver determines the set of satellites that can receive short message signals based on the identifier in the B2b message; the "Access Capability Indicator (2 bits)" field in the message corresponds to two broadcast states:

[0045] Status 1: 00: This satellite has no access capability;

[0046] State 2: 01, the satellite has access capability;

[0047] State 2 indicates that the satellite can receive the incoming short message signal of the user terminal. The set S is composed of N satellites that can receive the uplink signal of a user terminal.

[0048] Step 3: The user terminal compares and sorts the signal strength of each satellite B2b in the satellite set S that can receive short message signals. The user receiver evaluates the signal strength using the following download-to-noise ratio calculation method.

[0049] The B2b signal uses QPSK modulation, and the signal is divided into I and Q branches. The navigation signal is coherently integrated to calculate the broadband power P with a bandwidth of 1 / T. WB (k)

[0050]

[0051] Where T is the integration time of the user terminal, l represents the number of milliseconds, the maximum value is L, M is the number of samples within 1 millisecond, I(n) and Q(n) are the first and second samples of the corresponding I and Q branches respectively. n Calculate the narrowband power P with a bandwidth of 1 / MT NB (k)

[0052]

[0053] The corresponding broadband power P WB (k) for narrowband power P NB (k) is normalized to obtain the ratio value P NW (k), average the PNW(k) at K moments to get the mean value

[0054]

[0055] Then the carrier-to-noise ratio A is The carrier-to-noise ratio corresponding to the s-th satellite in the set S is calculated as A(s).

[0056] Step 4: The user receiver calculates the time for data transmission based on the amount of data it needs to send and the information transmission rate. If the amount of data to be transmitted is Bbit, since the uplink transmission rate of short message information is 400bit / s, the uplink transmission time needs K=B / 400 seconds.

[0057] Step 5: The user receiver obtains the satellite position through the satellite ephemeris, and calculates the visibility relationship based on its own position and the satellite position, including the observation elevation angle, visible arc and visible time;

[0058] The contents and definitions of navigation ephemeris parameters are shown in Table 1 below.

[0059] Table 1

[0060]

[0061]

[0062] Step 6: The user receiver can calculate the coordinates of the k-th time tk satellite in the Beidou coordinate system based on the received ephemeris parameters (X k , Y k , Z k ), 1≤k≤K, K is the maximum value and can be adjusted by the user terminal. The satellite position calculation method is shown in Table 2.

[0063] Table 2

[0064]

[0065]

[0066] Step 7: Since the user terminal can receive B2b signals, it can obtain its own position X0, Y0, Z0 through positioning and solution through B2b signals.

[0067] Step 8: Calculate the observation elevation angle from the user to the satellite, where λ is the longitude of the user terminal. is the latitude of the user terminal, Δe k , Δn k and Δu k is the intermediate variable, θ k is the observed elevation angle at the kth second;

[0068]

[0069]

[0070] Step 9: Count the theta values ​​greater than 5 k The number is recorded as the visible time T s , obtain the visible time T between the terminal and each satellite in the set S s .

[0071] Step 10: Select a satellite whose visible time is longer than the data transmission time, that is, select a satellite s such that T s ≥K. If there are multiple satellites such that T s ≥K, then select the satellite with the strongest B2b signal strength among these satellites.

[0072] A computer-readable storage medium stores computer program instructions, which, when loaded and executed by a processor, enable the processor to execute the satellite selection method for the Beidou global short message service.

[0073] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0074] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A satellite selection method for Beidou global short message service, characterized in that: include: Receive multiple Beidou satellite B2b signals and obtain the corresponding message of each satellite; According to the corresponding message of each satellite, determine the set of satellites that can receive short message signals; Compare and sort the B2b signal strengths of all satellites in the set; According to the current position, determine the visible relationship of all satellites in the set; Determine the time when data is sent; The satellite that is ultimately used to send the short message is selected based on the B2b signal strength ranking, visibility relationship, and data transmission time of all satellites in the set.

2. The star selection method according to claim 1, characterized in that: According to the inbound identification of the corresponding message of a certain satellite, it is determined whether the satellite has the short message function and is in a receivable state.

3. The star selection method according to claim 1, characterized in that: The satellite position is obtained through the satellite ephemeris in the message, and the visibility relationship is calculated based on the current position and the satellite position.

4. The star selection method according to claim 1, characterized in that: The visible relationship includes a relative position relationship and a visible time.

5. The star selection method according to claim 4, characterized in that: The method for selecting the satellite to be used to send the short message is: Select satellites whose visible time is greater than the data transmission time; If the visible time of multiple satellites is greater than the data transmission time, the satellite with the strongest B2b signal strength is selected.

6. The star selection method according to any one of claims 1 to 5, characterized in that: The user receiver calculates the coordinates of the corresponding satellite in the Beidou coordinate system based on the ephemeris parameters in the received satellite message.

7. The star selection method according to any one of claims 1 to 5, characterized in that: The user receiver evaluates the B2b signal strength of all satellites through the carrier-to-noise ratio calculation method.

8. The star selection method according to claim 4, characterized in that: The user receiver calculates the observation elevation angle of the satellite and further determines the visible time.

9. The star selection method according to any one of claims 1 to 5, characterized in that: The user receiver determines the set of satellites that can receive short message signals according to the identifier in the B2b message; the access capability indication field in the message corresponds to two broadcast states including: State 1: The satellite has no access capability; Status 2: This satellite has access capability.

10. A computer-readable storage medium having computer program instructions stored thereon, wherein when the computer program instructions are loaded and executed by a processor, the processor is caused to execute the method according to any one of claims 1 to 5.

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