Method for calculating probability of uplink interference of ground station on low earth orbit satellite

Abstract

The invention provides a method for calculating the probability of uplink interference of a ground station on a low earth orbit satellite. The method comprises the following steps: carrying out interference scene modeling according to the positions and antenna models of the ground station and the satellite, the satellite orbit height, the lowest elevation angle of the ground station antenna and the sidelobe width; calculating the airspace interference probability and the time domain interference probability of the satellite subjected to the ground station according to the interference scene and the satellite parameters, and substituting the time domain interference probability and the airspace interference probability into an interference probability calculation model to calculate the joint interference probability of the satellite subjected to the ground station; and when the joint interference probability is not zero, calculating the interference power received by the satellite according to the link parameters, and multiplying the interference power by the joint interference probability to obtain a link interference-to-noise ratio result. According to the method, the probability that the satellite is interfered within a period of time is analyzed from the two dimensions of time domain and space domain, and when the joint interference probability is not zero, the interference ratio result can be calculated in combination with the probability value, so that the complexity of interference calculation is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite communications, and in particular relates to a method for calculating the probability of uplink interference of a low-orbit satellite with a ground station. Background Art

[0002] In recent years, with the growth of demand for broadband Internet access and the reduction of satellite deployment costs, the world has ushered in a new wave of building low-orbit (LEO) satellite constellations, which also means a surge in demand for frequency resources. However, frequency resources are limited. The Radio Regulations stipulate that these resources should be used fairly, reasonably and effectively. In accordance with the rules, the competent authorities should apply to the International Telecommunication Union for satellite frequency and orbital resources on a "first-come, first-served coordinated sharing" basis. Before the satellite system is designed and launched, it is necessary to declare the frequency and orbit in accordance with the relevant ITU regulations and frequency division rules, and conduct necessary frequency and orbit coordination with the existing system to ensure coexistence and sharing among the systems. Due to the large number of satellites in the low-orbit satellite constellation system, the low-orbit constellation covers the world, and there are multiple interfering satellites within the visible range of users or gateway stations, resulting in more serious aggregate interference, and the probability of collinear extreme interference will also increase.

[0003] In addition, compared with the GEO (Geosynchronous Earth Orbit, GEO) system, the LEO constellation system has the characteristics of a large number of satellites, the position and beam pointing of satellites are constantly changing, and ground stations often access multiple satellites. At the same time, the rapid development of ground wireless communications has led to a sharp increase in the amount of calculation when calculating the interference of low-orbit satellite constellations, and the system has a large amount of calculation. Different from the relatively static interference scenario of the GEO system, the relative position of low-orbit satellites and ground stations is changing, which leads to the time-varying spatial geometric relationship between satellites and between satellites and ground stations, increasing the complexity of interference calculation. There have been many studies on the interference analysis between low-orbit constellations. Recommendation ITU-RS.1257 provides a method that can be used to calculate the probability of constellation satellites appearing in a circular or rectangular area. Based on this method, a simulation analysis algorithm for spatial probability can be designed. Recommendation ITU-RS.1529 proposes a calculation and analysis method based on the characteristic that the position of a single satellite on an orbit at any inclination obeys a certain probability density distribution law. This method does not require lengthy calculations, and the results obtained correspond to an infinite number of simulation days, ensuring statistical accuracy. Based on Recommendations ITU-RS.1257 and ITU-RS.1529, the Radio-communication Study Groups proposed a method for calculating the interference power between two low-orbit constellation systems based on spatial probability to evaluate the interference status of one constellation on another. Constellation snapshots are generated by placing reference satellites at different locations in a certain area to obtain all possible satellite distributions. The probability of constellation snapshots is represented by the satellite appearance probability of the reference satellite, and the interference power generated by different snapshots is calculated. The probability distribution is then obtained to evaluate the interference of the NGSO satellite system to the GSO satellite system. According to the relevant recommendations and reports of the ITU, a double-precision analysis method based on spatial position probability is proposed. The algorithm divides the longitude and latitude grids using a coarse and fine grid double-precision resolution algorithm, and then samples each spatial grid for interference simulation calculation and analysis. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for calculating the probability of uplink interference of a low-orbit satellite by a ground station. Starting from the time domain and the spatial domain, the time domain interference probability and the spatial domain interference probability are combined to obtain a joint interference probability, and the joint interference probability and the interference power are calculated to obtain an interference-to-noise ratio interference index. As the analysis time accumulates, the interference-to-noise ratio gradually stabilizes at a value, and this result can be used to approximately replace the interference-to-noise ratio result during this period. The complexity of interference calculation can be reduced, and the analysis efficiency can be effectively improved, thereby realizing efficient calculation of the uplink interference index.

[0005] To achieve the above objectives, the present invention provides a method for calculating the probability of uplink interference of a low-orbit satellite by a ground station, comprising: Step 1: Based on the location and antenna model of the ground station and satellite, the satellite orbit height h, and the minimum elevation angle of the ground station antenna and sidelobe width Conduct interference scenario modeling; Step 2: Calculate the probability of satellite being interfered with by the ground station in the airspace according to the interference scenario and satellite parameters ; Step 3: Calculate the probability of satellite being interfered with by the ground station in the time domain according to the interference scenario and satellite parameters , the time domain interference probability and spatial interference probability Substitute it into the interference probability calculation model to calculate the joint interference probability r of the satellite being interfered by the ground station; Step 4: In the joint interference probability When it is not zero, the interference power received by the satellite is calculated based on the link parameters , the interference power and the joint interference probability Multiply them together to get the link interference-to-noise ratio result.

[0006] As a further improvement of the present invention, in step 1, interference scenario modeling specifically includes: The scenario where the satellite is interfered by the ground station uplink is set as follows: the minimum elevation angle of the ground station antenna is , the ground station transmitter and satellite receiver use the same antenna model, and the satellite orbit altitude , the antenna models of the ground station and the satellite only consider The satellite is at a specified time. It passed over the ground station several times.

[0007] As a further improvement of the present invention, the antenna model used by the transmitting and receiving antennas is: , in, is the diameter of the antenna, is the signal wavelength, is a first-order Bessel function, is the angle from the antenna main lobe axis in degrees.

[0008] As a further improvement of the present invention, in step 2, the spatial interference probability is calculated. , specifically: According to the minimum elevation angle of the ground station antenna , satellite orbit inclination and sidelobe width , calculate the minimum elevation angle of the ground station antenna Satellite orbit altitude The visible area and the area that the satellite passes through in the visible airspace : , , in, , represents the distance from the satellite to the center of the earth, is the radius of the Earth; The spatial dimension probability of the satellite being interfered with by the ground station uplink, that is, the spatial interference probability for: , When there is When there are 1 satellites, the probability of interference in the spatial dimension of each satellite is calculated separately. , and finally the overall spatial interference probability is obtained , .

[0009] As a further improvement of the present invention, in step 3, the spatial interference probability When it is not zero, calculate the time domain interference probability , specifically: Step 31: Set the satellite to The satellite passes over the ground station several times and the satellite's speed is calculated based on the visible range. , combined with the running distance, we can get the time it takes for the satellite to orbit the earth , we can get the number of times the satellite passes over the ground station in time T, that is, the number of times it passes over the top; Calculate the satellite's speed for: , in is the gravitational constant, is the mass of the Earth, is the radius of the earth, and the time it takes for a satellite to orbit the earth is calculated as follows: , Judgement The number of times you pass the top within a certain period of time, i.e. the revisit period for: ; Step 32: According to the satellite orbit height , minimum elevation angle of ground station antenna and sidelobe width , calculate the visible range area of ​​the ground station antenna and the area of ​​the actual communication range : , , Remove The probability of not falling into the sidelobe communication range in any of the revisits , get the satellite at The probability of being interfered within a certain period of time, that is, the probability of interference in the time domain for: , When there is When there are 1 satellite, the probability of interference in the time dimension of each satellite needs to be calculated separately. , and finally the overall spatial interference probability is obtained , ; Step 33, The probability r of the joint interference received by the satellite from the ground station within the time is: , in , is a weight constant, which depends on the degree of concern about temporal and spatial interference and ranges from (0,1].

[0010] As a further improvement of the present invention, in step 4, the interference power is calculated , specifically: Step 41, in the modeled scenario where the satellite is interfered with by the uplink of the ground station, calculate the interference power received by the receiving end at a certain moment: , in, is the interference signal power received by the satellite at that moment, is the transmitting power of the first ground station, is the signal wavelength, is the antenna gain of the interference signal transmitting antenna at a deviation from its main axis from -180° to 180°, is the antenna gain of the receiving antenna of the interfered system at a deviation from its main axis from -180° to 180°, Indicates the link distance; Step 42: calculate the satellite receiving end interference power and the joint interference probability Multiply them to get the interference-to-noise ratio of the interference signal received by the satellite : , in , is the noise power, is the Boltzmann constant, is the equivalent noise temperature, The satellite operating bandwidth.

[0011] The beneficial effects of the present invention are as follows: starting from the time domain and the spatial domain, the time domain interference probability and the spatial domain interference probability are calculated respectively, and then the time domain interference probability and the spatial domain interference probability are combined to obtain the joint interference probability, and then the joint interference probability and the interference power are calculated to obtain the interference index, which can reduce the complexity of interference calculation and effectively improve the analysis efficiency, thereby realizing the calculation of uplink interference power. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a flowchart of the implementation process of the method of the embodiment of the present invention.

[0013] Figure 2 It is a schematic diagram of the area covered by the visible airspace of the satellite in calculating the space probability of the present invention.

[0014] Figure 3 It is the result of the interference-to-noise ratio calculated by the method of the embodiment of the present invention at different analysis time lengths. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] It should be noted here that in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0017] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0018] The method for calculating the probability of uplink interference of a low-orbit satellite by a ground station of the present invention comprises the following steps: Step 1: Based on the location and antenna model of the ground station and satellite, the satellite orbit height h, and the minimum elevation angle of the ground station antenna and sidelobe width And other parameters to model interference scenarios; Step 2: Calculate the probability of satellite being interfered with by the ground station in the airspace according to the interference scenario and satellite parameters ; Step 3: Calculate the probability of satellite being interfered with by the ground station in the time domain according to the interference scenario and satellite parameters , the time domain interference probability and spatial interference probability Substitute it into the interference probability calculation model to calculate the joint interference probability r of the satellite being interfered by the ground station; Step 4: In the joint interference probability When it is not zero, the interference power received by the satellite is calculated based on the link parameters , the interference power and the joint interference probability Multiply them together to get the link interference-to-noise ratio result.

[0019] Combination Figure 1-Figure 3 The present invention is described in detail.

[0020] Step 1: interference scenario modeling.

[0021] Specifically, the scenario where the satellite is interfered with by the ground station uplink is set as follows: the minimum elevation angle of the ground station antenna is , the ground station transmitter and satellite receiver use the same antenna model, and the satellite orbit altitude , the antenna models of the ground station and the satellite only consider Since the probability of main lobe interference is too low, the interference of side lobes is mainly considered, and the size of side lobes can be adjusted. Preferably, the satellite is at a specified time. Passing over the ground station several times. Figure 1 The satellite parameters input and read in the interference scenario mainly include the satellite's latitude and longitude position information, the on-board equivalent noise temperature, the satellite's operating bandwidth, and the antenna model parameters used on the satellite, mainly including the peak maximum gain, antenna aperture, and operating frequency; the ground station parameters input and read mainly include the ground station's latitude and longitude position information and antenna model, ground station antenna transmission power, antenna minimum elevation angle, and sidelobe width.

[0022] Among them, the antenna model used by the transmitting and receiving antennas is: , in, is the diameter of the antenna, is the signal wavelength, is a first-order Bessel function, is the angle from the antenna main lobe axis in degrees.

[0023] Step 2: Spatial Interference Probability calculate.

[0024] Specifically, according to the minimum elevation angle of the ground station antenna , satellite orbit inclination and sidelobe width , calculate the minimum elevation angle of the ground station antenna Satellite orbit altitude The visible area and the area that the satellite passes through in the visible airspace : , , in, , represents the distance from the satellite to the center of the earth, is the radius of the Earth, Generally, it is 6371km. In the case of side lobes, the probability of the satellite being interfered with by the ground station in the spatial dimension is the probability of spatial interference. for: .

[0025] In this embodiment, the spatial dimension probability of multiple satellites is considered. When there are 1 satellites, the probability of interference in the spatial dimension of each satellite is calculated separately. , and finally the overall spatial interference probability is obtained , . Where i=1, 2, 3,…X.

[0026] Step 3: Time domain interference probability calculate.

[0027] Specifically, the probability of interference in the spatial domain When it is not zero, continue to calculate the time domain interference probability based on this .

[0028] Step 31, in this embodiment, the satellite is at a specified time The satellite passes over the ground station several times and the satellite's speed is calculated based on the visible range. , combined with the running distance, we can get the time it takes for the satellite to orbit the earth , thus obtaining the number of times the satellite passes over the ground station within time T, that is, the number of overpasses.

[0029] Calculate the satellite's speed for: , in is the gravitational constant, Generally , is the mass of the Earth, for , is the radius of the Earth.

[0030] The time it takes for a satellite to orbit the Earth is calculated as follows: .

[0031] In this embodiment, the satellite passes over the earth once in one orbit around the earth, so the total time T is directly divided by the time it takes for the satellite to orbit the earth once. To get the number of circles, that is, the number of times you go over the top.

[0032] Therefore, it can be judged that The number of times a satellite passes overhead within a certain period of time is called the revisit period. for: .

[0033] Step 32: Combine revisit cycles , through the satellite orbit height h, the lowest elevation angle of the ground station antenna and sidelobe width , calculate the visible range area of ​​the ground station antenna and the area of ​​the actual communication range : , .

[0034] In this embodiment, the spatial interference probability It is obtained by dividing the area of ​​the satellite's visible airspace by the strip area of ​​the ground station's visible airspace by the area of ​​the circular visible airspace. The area is obtained by comparing the two circular visible airspace areas of the ground station. It is calculated by considering only the lowest elevation angle α of the ground station antenna. The actual area that can communicate is Considering the side lobes The area after. Figure 2 shown.

[0035] Among them, remove The probability of not falling into the sidelobe communication range in any of the revisits , get the satellite at The probability of being interfered within a certain period of time, that is, the probability of interference in the time domain for: .

[0036] Consider the probability of multiple satellites in the time dimension. When there are 1 satellite, the probability of interference in the time dimension of each satellite needs to be calculated separately. , and finally the overall spatial interference probability is obtained , . Where j=1, 2, 3, …X.

[0037] Step 33, calculate The probability r of the joint interference received by the satellite from the ground station within the time is: , in , is a weight constant, which depends on the degree of concern about temporal and spatial interference and ranges from (0,1].

[0038] Step 4: Interference Power calculate.

[0039] Specifically, in step 41, the joint interference probability When it is not zero, in the scenario where the satellite is modeled to be interfered by the ground station uplink, the interference power of the interference source signal received by the receiver at a certain time is calculated. : , in, is the interference power of the interference source signal received by the satellite at that moment, is the transmitting power of the first ground station, is the signal wavelength, is the antenna gain of the interference signal transmitting antenna at a certain angle away from its main axis, is the antenna gain of the receiving antenna of the interfered system at a certain angle away from its main axis, In this embodiment, preferably, an omnidirectional antenna is taken as an example, and the certain angle range of deviation from the main axis is -180° to 180°.

[0040] Step 42: calculate the satellite receiving end interference power and the joint interference probability Multiply them to get the interference-to-noise ratio of the interference signal received by the satellite : , in , is the noise power, is the Boltzmann constant, which is generally , is the equivalent noise temperature, in units of , is the satellite operating bandwidth, in GHz.

[0041] In this embodiment, when considering a satellite, the satellite altitude is set to 500km and 400km respectively, the working frequency band is 14.5GHz, the receiving antenna aperture is 0.5m, the antenna efficiency is 50%, the ground station transmission power is 4.03W, the equivalent noise temperature is set to 550K, and the working bandwidth is 64MHz; the minimum elevation angle of the ground station antenna is set to 40°, the side lobe width is 10°, the satellite orbit inclination is 30°, the degree of concern for the probability of spatial interference is 0.5, the degree of concern for the probability of time domain interference is also set to 0.5, and the simulation time is set to 24h. The curve of the interference-to-noise ratio of the interference signal received by satellites at different altitudes as a function of the accumulated time calculated by this method is as follows: Figure 3 shown.

[0042] Depend on Figure 3 It can be seen that with the accumulation of time, the interference-to-noise ratios calculated by satellites at an altitude of 500 km and 400 km are stabilized at -5.1 dB and -4.3 dB respectively. Therefore, this result can be used to replace the interference analysis result to reduce the calculation complexity.

[0043] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for calculating the probability of uplink interference of a low-orbit satellite by a ground station, characterized in that: include: Step 1: Based on the location and antenna model of the ground station and satellite, the satellite orbit height h, and the minimum elevation angle of the ground station antenna and sidelobe width Conduct interference scenario modeling; Step 2: Calculate the probability of satellite being interfered with by the ground station in the airspace according to the interference scenario and satellite parameters ; Step 3: Calculate the probability of satellite being interfered with by the ground station in the time domain according to the interference scenario and satellite parameters , the time domain interference probability and spatial interference probability Substitute it into the interference probability calculation model to calculate the joint interference probability r of the satellite being interfered by the ground station; Step 4, in the joint interference probability When it is not zero, the interference power received by the satellite is calculated based on the link parameters , the interference power and the joint interference probability Multiply them together to get the link interference-to-noise ratio result.

2. The calculation method according to claim 1, characterized in that: In step 1, interference scenario modeling is performed, including: The scenario where the satellite is interfered by the ground station uplink is set as follows: the minimum elevation angle of the ground station antenna is , the ground station transmitter and satellite receiver use the same antenna model, and the satellite orbit altitude , the antenna models of the ground station and the satellite only consider The satellite is at a specified time. It passed over the ground station several times.

3. The calculation method according to claim 2, characterized in that: The antenna model used by the transmitting and receiving antennas is: ， in, is the diameter of the antenna, is the signal wavelength, is a first-order Bessel function, is the angle from the antenna main lobe axis in degrees.

4. The calculation method according to claim 3, characterized in that: In step 2, the probability of spatial interference is calculated , specifically: According to the minimum elevation angle of the ground station antenna , satellite orbit inclination and sidelobe width , calculate the minimum elevation angle of the ground station antenna Satellite orbit altitude The visible area and the area that the satellite passes through in the visible airspace : ， ， in, , represents the distance from the satellite to the center of the earth, is the radius of the Earth; The spatial dimension probability of the satellite being interfered with by the ground station uplink, that is, the spatial interference probability for: ， When there is When there are 1 satellites, the probability of interference in the spatial dimension of each satellite is calculated separately. , and finally the overall spatial interference probability is obtained , 。 5. The calculation method according to claim 4, characterized in that: In step 3, the probability of interference in the spatial domain When it is not zero, calculate the time domain interference probability , specifically: Step 31: Set the satellite to The satellite passes over the ground station several times and the satellite's speed is calculated based on the visible range. , combined with the running distance, we can get the time it takes for the satellite to orbit the earth , we can get the number of times the satellite passes over the ground station in time T, that is, the number of times it passes over the top; Calculate the satellite's speed for: ， in is the gravitational constant, is the mass of the Earth, is the radius of the earth, and the time it takes for a satellite to orbit the earth is calculated as follows: ， Judgement The number of times you pass the top within a certain period of time, i.e. the revisit period for: ； Step 32: According to the satellite orbit height , minimum elevation angle of ground station antenna and sidelobe width , calculate the visible range area of ​​the ground station antenna and the area of ​​the actual communication range : ， ， Remove The probability of not falling into the sidelobe communication range in any of the revisits , get the satellite at The probability of being interfered within a certain period of time, that is, the probability of interference in the time domain for: ， When there is When there are 1 satellite, the probability of interference in the time dimension of each satellite needs to be calculated separately. , and finally the overall spatial interference probability is obtained , ； Step 33, The probability r of the joint interference received by the satellite from the ground station within the time is: ， in , is a weight constant, which depends on the degree of concern about temporal and spatial interference and ranges from (0,1].

6. The calculation method according to claim 5, characterized in that: In step 4, the interference power is calculated , specifically: Step 41, in the modeled scenario where the satellite is interfered with by the ground station uplink, calculate the interference power received by the receiving end at a certain time : ， in, is the interference power of the interference source signal received by the satellite at that moment, is the transmitting power of the first ground station, is the signal wavelength, is the antenna gain of the interference signal transmitting antenna at a deviation from its main axis from -180° to 180°, is the antenna gain of the receiving antenna of the interfered system at a deviation from its main axis from -180° to 180°, Indicates the link distance; Step 42: calculate the satellite receiving end interference power and the joint interference probability Multiply them to get the interference-to-noise ratio of the interference signal received by the satellite : ， in , is the noise power, is the Boltzmann constant, is the equivalent noise temperature, The satellite operating bandwidth.

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