Calculation Method for the Probability of Uplink Interference of Low-Earth-Orbit Satellites by Ground Stations

Abstract

The present invention proposes a method for calculating the probability of a low-earth orbit satellite being interfered by a ground station during uplink, including: performing interference scenario modeling based on the positions and antenna models of the ground station and the satellite, the satellite operating orbit altitude, the minimum elevation angle of the ground station antenna, and the sidelobe width; calculating the spatial interference probability and the temporal interference probability of the satellite being interfered by the ground station according to the interference scenario and satellite parameters, and substituting the temporal interference probability and the spatial interference probability into an interference probability calculation model to calculate the combined interference probability of the satellite being interfered by the ground station; when the combined 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 combined interference probability to obtain the result of the link signal-to-interference-plus-noise ratio. The present invention analyzes the probability of the satellite being interfered within a certain period of time from two dimensions of time domain and spatial domain, and can calculate the dry ratio result in combination with the probability value when the combined interference probability is not zero, effectively reducing the complexity of interference calculation.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite communication, and particularly relates to a method for calculating the probability of uplink interference of a low-earth orbit satellite by a ground station. Background Art

[0002] In recent years, with the growth of the demand for broadband Internet access and the reduction of the cost of deploying satellites, the world has witnessed a new wave of building low-earth orbit (LEO) satellite constellations, which also means a surge in the demand for frequency resources. However, frequency resources are limited. The Radio Regulations stipulate that these resources should be used fairly, reasonably and effectively. Each competent authority should comply with the principle of "first come, first served, coordinated sharing" when applying to the International Telecommunication Union for satellite frequency and orbital resources according to the rules. Before the design and launch deployment of a satellite system, it is necessary to declare frequencies and orbits according to the relevant regulations of the ITU and frequency allocation rules, and conduct necessary frequency and orbit coordination with existing systems to ensure the coexistence and sharing among systems. Due to the large number of satellites in the low-earth orbit satellite constellation system and the global coverage of the low-earth orbit constellation, there are multiple interfering satellites within the visible range of users or gateway stations, resulting in relatively serious lumped interference, and at the same time, the probability of collinear extreme interference will also increase.

[0003] In addition, compared with the GEO (Geosynchronous Earth Orbit) system, the LEO constellation system has the characteristics of a large number of satellites, continuously changing positions and beam directions of satellites, and ground stations often accessing multiple satellites. At the same time, the rapid development of terrestrial wireless communication has led to a sharp increase in the computational complexity when calculating the interference of low-Earth orbit satellite constellations, resulting in a relatively large system computational load. Different from the relatively static interference scenario of the GEO system, the relative positions of low-Earth orbit satellites and ground stations are changing, leading to the time-varying nature of the spatial geometric relationships between satellites and between satellites and ground stations, increasing the complexity of interference calculation. Regarding the interference analysis between low-Earth orbit constellations, many studies have been conducted. Recommendation ITU-R S.1257 gives 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 regarding spatial probability can be designed. Based on the characteristic that the position of a single satellite in an orbit with any inclination follows a certain probability density distribution law, Recommendation ITU-R S.1529 proposes a calculation and analysis method. This method does not require long calculations, and the obtained results correspond to an infinite number of simulated days, ensuring the accuracy of statistics. The Radio-communication Study Groups propose a method for calculating the interference power between two low-Earth orbit constellation systems based on spatial probability, in order to evaluate the interference situation of one constellation on another. Constellation snapshots are also generated by placing reference satellites at different positions in a certain area to obtain all possible satellite distributions. The probability of constellation snapshots is characterized by the satellite appearance probability of the reference satellites, and the interference power generated by different snapshots is calculated, and then the probability distribution is obtained to evaluate the interference of the NGSO satellite system on 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. This algorithm divides the longitude and latitude grid using a double-precision resolution algorithm with coarse and fine grids, and then samples each spatial grid, and then conducts 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-Earth orbit satellite by combining the time-domain interference probability and the space-domain interference probability starting from the time domain and the space domain to obtain the joint interference probability, and then operating the joint interference probability and the interference power to obtain the carrier-to-interference-plus-noise ratio (CINR) interference index. As the analysis time accumulates, the CINR gradually stabilizes at a value, and this result can be approximately used to replace the CINR result during this period. It can reduce the complexity of interference calculation and effectively improve the analysis efficiency, thereby realizing the efficient calculation of the uplink interference index.

[0005] To achieve the above objectives, the present invention provides a method for calculating the probability of a low-earth orbit satellite being interfered by a ground station in the uplink, including:

[0006] Step 1, perform interference scenario modeling according to the positions and antenna models of the ground station and the satellite, the satellite operating orbit altitude h, the minimum elevation angle of the ground station antenna and the sidelobe width ;

[0007] Step 2, calculate the spatial interference probability of the satellite being interfered by the ground station according to the interference scenario and satellite parameters ;

[0008] Step 3, calculate the temporal interference probability of the satellite being interfered by the ground station according to the interference scenario and satellite parameters , substitute the temporal interference probability and the spatial interference probability into the interference probability calculation model to calculate the combined interference probability r of the satellite being interfered by the ground station;

[0009] Step 4, when the combined interference probability is not zero, calculate the interference power received by the satellite according to the link parameters , multiply the interference power by the combined interference probability and compare it with the noise power N to obtain the result of the link signal-to-interference-plus-noise ratio .

[0010] As a further improvement of the present invention, in Step 1, the interference scenario modeling specifically includes:

[0011] The interference scenario of the satellite being interfered by the ground station in the uplink is set as: the minimum elevation angle of the ground station antenna is , the same antenna model is used at the transmitting end of the ground station and the receiving end of the satellite, the satellite operating orbit altitude , only the sidelobe of the antenna models of the ground station and the satellite is considered, and the satellite passes over the ground station multiple times during the specified time .

[0012] As a further improvement of the present invention, the antenna model adopted by the transceiver antennas is:

[0013] ,

[0014] where, is the aperture of the antenna, is the signal wavelength, is a type of first-order Bessel function, is the angle deviating from the main lobe axis of the antenna, in degrees.

[0015] As a further improvement of the present invention, in step 2, calculate the airspace interference probability , specifically:

[0016] 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 at the satellite operating orbit altitude the visible area and the area swept by the satellite in the visible airspace :

[0017] ,

[0018] ,

[0019] wherein, , represents the distance from the satellite to the earth's center, is the radius of the earth;

[0020] The spatial dimension probability of the satellite being interfered by the ground station uplink, that is, the airspace interference probability is:

[0021] ,

[0022] When there are satellites, calculate the probability of interference in the spatial dimension of each satellite , and finally obtain the overall spatial interference probability ,

[0023] .

[0024] As a further improvement of the present invention, in step 3, when the airspace interference probability is not zero, calculate the time-domain interference probability , specifically:

[0025] Step 31, assume that the satellite passes over the ground station multiple times within the specified time , calculate the satellite running speed according to the visible range, and then combine the running distance to obtain the time for the satellite to orbit the earth once, and obtain the number of times the satellite passes over the ground station within the time T, that is, the overflight times;

[0026] Calculate the satellite running speed as:

[0027] ,

[0028] where is the gravitational constant, is the mass of the Earth, is the radius of the Earth. The method for calculating the time for a satellite to orbit the Earth once is as follows:

[0029] ,

[0030] Determine the number of overpasses within the time of , that is, the revisit period is:

[0031] ;

[0032] Step 32, according to the satellite operating orbit altitude , the minimum elevation angle of the ground station antenna and the sidelobe width , calculate the visible range area of the ground station antenna and the area of the actually communicable range:

[0033] ,

[0034] ,

[0035] Remove the probability that none of the revisits fall into the sidelobe communication range, and obtain the probability that the satellite is interfered within the time of , that is, obtain the time-domain interference probability which is:

[0036] ,

[0037] When there are satellites, it is necessary to calculate the probability of interference for each satellite in the time dimension , and finally obtain the overall spatial interference probability ,

[0038] ;

[0039] Step 33, The combined interference probability r of the satellite receiving from the ground station within the time of

[0040] is:

[0041] where , are weight constants, depending on the degree of attention to time-domain and spatial-domain interference, and the range is (0,1].

[0042] As a further improvement of the present invention, in step 4, calculate the interference power , specifically:

[0043] Step 41, in the scenario of the satellite being interfered by the uplink of the ground station in the model, calculate the interference power received by the receiving end at a certain moment:

[0044] ,

[0045] wherein, is the interference signal power received by the satellite at this moment, is the transmitting power of the ground station, is the signal wavelength, is the antenna gain of the interference signal transmitting antenna from -180° to 180° off its main axis, is the antenna gain of the receiving end antenna of the system under interference from -180° to 180° off its main axis, represents the link distance;

[0046] Step 42, multiply the calculated interference power of the satellite receiving end by the joint interference probability and compare it with the noise power N to obtain the signal-to-interference-plus-noise ratio of the satellite receiving the interference signal:

[0047] ,

[0048] wherein , is the noise power, is the Boltzmann constant, is the equivalent noise temperature, is the satellite operating bandwidth.

[0049] Advantages of the present invention: Starting from the time domain and the spatial domain, calculate the time domain interference probability and the spatial domain interference probability respectively, and then combine the time domain interference probability and the spatial domain interference probability to obtain the joint interference probability, so as to calculate the interference index by operating the joint interference probability and the interference power, which can reduce the complexity of interference calculation, effectively improve the analysis efficiency, and thus realize the calculation of the uplink interference power. Brief Description of the Drawings

[0050] Figure 1 is the implementation flow block diagram of the method of the embodiment of the present invention.

[0051] Figure 2 is the schematic diagram of the area passed by the visible airspace of the satellite for calculating the spatial probability of the present invention.

[0052] Figure 3It is the result of the dry signal-to-noise ratio calculated by the method of the embodiment of the present invention under different analysis durations. Detailed implementation manners

[0053] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] Here, it should be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, and other details less related to the present invention are omitted.

[0055] In addition, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0056] The method for calculating the probability of the low-orbit satellite being interfered by the ground station in the uplink of the present invention includes the following steps:

[0057] Step 1, perform interference scenario modeling according to the positions of the ground station and the satellite, the antenna model, the satellite operating orbit height h, the minimum elevation angle of the ground station antenna and the side lobe width and other parameters.

[0058] Step 2, calculate the spatial domain interference probability of the satellite being interfered by the ground station according to the interference scenario and satellite parameters ;

[0059] Step 3, calculate the time domain interference probability of the satellite being interfered by the ground station according to the interference scenario and satellite parameters , substitute the time domain interference probability and the spatial domain interference probability into the interference probability calculation model to calculate the combined interference probability r of the satellite being interfered by the ground station;

[0060] Step 4, when the combined interference probability is not zero, calculate the interference power received by the satellite according to the link parameters , multiply the interference power by the combined interference probability and compare it with the noise power N to obtain the result of the link dry signal-to-noise ratio .

[0061] Combined with Figures 1 - 3 describe the present invention in detail.

[0062] Step 1, interference scenario modeling.

[0063] Specifically, the interference scenario received by the satellite from the ground station is set as follows: the minimum elevation angle of the ground station antenna is , the same antenna model is used for the transmitting end of the ground station and the receiving end of the satellite, and the orbital altitude of the satellite is , and only the side lobes of the antenna models of the ground station and the satellite are considered. Since the main lobe interference probability is too low, the side lobe interference is mainly considered, and the size of the side lobe can be adjusted. Preferably, the satellite passes over the ground station multiple times during the specified time . Combining Figure 1 , the satellite parameters input and read in the interference scenario mainly include the satellite's longitude, latitude, and altitude position information, the equivalent noise temperature on the satellite, 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 point, etc.; the ground station parameters input and read mainly include the ground station's longitude, latitude, and altitude position information, as well as the antenna model, the transmitting power of the ground station antenna, the minimum elevation angle of the antenna, and the side lobe width, etc.

[0064] Among them, the antenna model adopted by the transmitting and receiving antennas is:

[0065] ,

[0066] Among them, is the aperture of the antenna, is the signal wavelength, is a type of first-order Bessel function, is the angle deviating from the main lobe axis of the antenna, in degrees.

[0067] Step 2, calculation of the spatial domain interference probability Calculation.

[0068] Specifically, according to the minimum elevation angle of the ground station antenna, the orbital inclination of the satellite, and the side lobe width , calculate the visible area of the minimum elevation angle of the ground station antenna at the orbital altitude of the satellite and the area swept by the satellite in the visible airspace:

[0069] ,

[0070] ,

[0071] Among them, , represents the distance from the satellite to the center of the earth, is the radius of the earth, is generally 6371 km. When considering Under the condition of sidelobes, the spatial dimension probability of the satellite being interfered by the ground station, that is, the airspace interference probability is as follows:

[0072] .

[0073] In this embodiment, the spatial dimension probability in the case of multiple satellites is considered. When there are X satellites, the probability of each satellite being interfered in the spatial dimension is calculated separately , and finally the overall spatial interference probability is obtained ,

[0074] .

[0075] where i = 1, 2, 3... X.

[0076] Step 3, time domain interference probability Calculation.

[0077] Specifically, when the airspace interference probability is not zero, continue to calculate the time domain interference probability on this basis .

[0078] Step 31, in this embodiment, the satellite passes over the ground station multiple times within the specified time . Calculate the satellite running speed according to the visible range , and then combine the running distance to obtain the time for the satellite to orbit the earth once , so as to obtain the number of times the satellite passes over the ground station within the time T, that is, the overflight times

[0079] Calculate the satellite running speed as follows:

[0080] ,

[0081] where is the gravitational constant, is generally , is the mass of the earth, is , is the radius of the earth.

[0082] The calculation method of the time for the satellite to orbit the earth once is as follows:

[0083] .

[0084] In this embodiment, the satellite passes over the earth's head once when orbiting the earth once. Therefore, directly divide the total time T by the time for the satellite to orbit the earth once To obtain the number of orbits of detouring, that is, the number of overpasses.

[0085] Therefore, it can be judged that within the time, the number of overpasses of the satellite, that is, the revisit period is:

[0086] .

[0087] Step 32, combined with the revisit period , through the satellite operating orbit altitude h, the minimum elevation angle of the ground station antenna and the sidelobe width , calculate the visible range area of the ground station antenna and the area of the actually communicable range:

[0088] ,

[0089] .

[0090] In this embodiment, the airspace interference probability is obtained by dividing the strip-shaped area where the satellite crosses the visible airspace of the ground station by the circular visible airspace area. The area of the time-domain interference probability is obtained by dividing the two circular visible airspace areas of the ground station. The visible range area is calculated only considering the minimum elevation angle α of the ground station antenna. The area of the actually communicable range is the area after considering the sidelobe . Refer to Figure 2 as shown.

[0091] Among them, removing the probability that none of the revisits fall into the sidelobe communication range, the probability that the satellite is interfered within the time is obtained, that is, the time-domain interference probability is:

[0092] .

[0093] Consider the probability situation in the time dimension with multiple satellites. When there are satellites, it is necessary to calculate the probability of each satellite being interfered in the time dimension respectively, and finally obtain the overall space interference probability ,

[0094] .

[0095] Among them, j = 1, 2, 3... X.

[0096] Step 33, calculate The joint interference probability r that the satellite receives from the ground station within the time is:

[0097] ,

[0098] where a and b are weight constants, depending on the attention degree to time-domain and space-domain interferences, and the range is (0, 1].

[0099] Step 4, interference power Calculate.

[0100] Specifically, in Step 41, when the joint interference probability is not zero, in the scenario of the satellite being uplink interfered by the ground station in the established model, calculate the interference power of the interference source signal received by the receiving end at a certain moment:

[0101] ,

[0102] where, is the interference power of the interference source signal received by the satellite at this moment, is the transmitting power of the ground station, is the signal wavelength, is the antenna gain of the interference signal transmitting antenna at a certain angle deviating from its main axis, is the antenna gain of the receiving end antenna of the interfered system at a certain angle deviating from its main axis, represents the link distance. In this embodiment, preferably taking an omnidirectional antenna as an example, the range of a certain angle deviating from the main axis is -180° to 180°.

[0103] Step 42, multiply the calculated interference power of the satellite receiving end by the joint interference probability and compare it with the noise power N to obtain the signal-to-interference-plus-noise ratio of the satellite receiving the interference signal:

[0104] ,

[0105] where , is the noise power, is the Boltzmann constant, generally , is the equivalent noise temperature, with the unit of , is the satellite operating bandwidth, with the unit of GHz.

[0106] In this embodiment, when considering a single satellite, the satellite altitudes are set to 500 km and 400 km respectively, the operating frequency band is 14.5 GHz, the receiving antenna aperture is 0.5 m, the antenna efficiency is 50%, the transmitting power of the ground station is 4.03 W, the equivalent noise temperature is set to 550 K, and the operating bandwidth is 64 MHz; the minimum elevation angle of the ground station antenna is set to 40°, the sidelobe width is 10°, the satellite orbit inclination is 30°, the degree of concern about the spatial interference probability is 0.5, and the degree of concern about the temporal interference probability is also set to 0.5. The simulation time is set to 24 h. The curves of the carrier-to-interference-plus-noise ratio of the interference signals received by satellites at different altitudes varying with the cumulative time calculated by this method are as Figure 3 shown.

[0107] As Figure 3 can be seen, with the accumulation of time, the carrier-to-interference-plus-noise ratios calculated for the satellite at an altitude of 500 km and the satellite at an altitude of 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 computational complexity.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions 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 and compare with the noise power N to get the link interference-to-noise ratio Result; 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 , ； 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].

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 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 ground station transmission power, is the signal wavelength, is the antenna gain of the interference signal transmitting antenna at a deviation of -180°~180° from its main axis, is the antenna gain of the receiving antenna of the interfered system at a distance of -180°~180° from its main axis, Indicates the link distance; Step 42: calculate the satellite receiving end interference power and the joint interference probability Multiply and compare with the noise power N to get the interference-to-noise ratio of the satellite received interference signal : ， in , is the noise power, is the Boltzmann constant, is the equivalent noise temperature, The satellite operating bandwidth.

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