A method for determining the co-frequency interference of satellite constellations to geostationary orbit satellites

Abstract

The present invention discloses a method for determining the same-frequency interference of a satellite constellation on a geostationary orbit satellite, and relates to a method for determining the same-frequency interference of a satellite constellation. It mainly aims at the problem of how to quantify the same-frequency interference between satellite communication systems, discloses the process of the method for determining the interference of a satellite constellation on a geostationary orbit satellite with the interference-to-noise ratio as the judgment standard, and understands three C / N thresholds in detail. The evaluation is based on I / N, and the satellite constellation system resource utilization rate is higher than that of only using the EPFD limit value; the present invention mainly aims at the problem of how to quantify the same-frequency interference between satellite communication systems, and provides an interference determination method for the interference coordination between a non-geostationary orbit satellite constellation and a geostationary orbit satellite through the determination of the interference-to-noise ratio and the equivalent power flux density. The use of the interference determination method is more in line with the actual link situation of the geostationary orbit satellite, can effectively improve the coordination efficiency, avoid waste of resources, and provide more link margins for the constellation system.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to a method for determining the co-frequency interference of a satellite constellation on a geostationary orbit satellite. Background Art

[0002] For non-geostationary satellite constellations, due to the characteristics of their orbits, satellites will repeatedly cross the equator at a certain angle. If no measures are taken, co-linear interference will continue to occur in the scenario where non-geostationary satellites (NGSO) and geostationary satellites (GSO) coexist.

[0003] In response to the possible interference problems between NGSO and GSO systems, the ITU currently provides a method that uses the equivalent power flux-density (EPFD) limit as the interference judgment standard. The EPFD limit was proposed by the World Radio Conference in 1997, and after several revisions, it was determined by the World Radio Conference in 2000. According to the history of the formulation of the EPFD limit, the EPFD limit meets the protection standard for the GSO links provided by all satellite operators at that time. However, the existing GSO communication technology has made great progress. The GSO link 20 years ago may not be suitable for the current GSO system. At the same time, when the current constellation operator coordinates with the GSO operator, it is aimed at one or several GSO systems. Still using the EPFD limit will put forward more stringent requirements on the constellation system, resulting in a waste of frequency and orbit resources. Therefore, this method proposes a satellite constellation interference judgment method for GSO based on the interference-to-noise ratio as the judgment standard, which is more in line with the actual link situation of GSO, can effectively improve the coordination efficiency, and provide more link margins for the constellation system. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of co-channel interference between satellite communication systems and propose a method for determining the co-channel interference of a satellite constellation to a geostationary orbit satellite using the interference-to-noise ratio as a criterion.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for determining co-frequency interference of a satellite constellation to a geostationary orbit satellite comprises the following steps:

[0007] S1: Determine the geostationary satellite system (C / N) cs 、(C / N) bitsync 、(C / N) t, GSO system unavailability P, number of NGSO systems n, percentage of long-term total interference to total noise X;

[0008] S2: Calculate I / N th Limit curve, the calculation formula is as follows:

[0009]

[0010] In the formula,

[0011]

[0012]

[0013] I long-term / N=10log[X / (100n)]

[0014] in,

[0015] I bit-sync / N is the loss of synchronization limit;

[0016] I BER / N is the short-term interference limit;

[0017] I log-term / N is the long-term interference limit;

[0018] The interference to the geostationary satellite link in clear sky Threshold, in dB;

[0019] is the desynchronization threshold of the interfered geostationary orbit satellite link, in dB;

[0020] is the demodulation threshold of the interfered geostationary satellite link, in dB;

[0021] n represents the number of low-orbit constellation systems;

[0022] P is lower than The allowable time percentage of the threshold, i.e., system unavailability, in %;

[0023] y is the percentage of long-term interference time;

[0024] X is the percentage of long-term interference in the total noise;

[0025] N is the noise power of the interfered geostationary satellite system, in dBW;

[0026] S3: Calculate the cumulative probability distribution curve of I / N complementarity between the NGSO system and the GSO system ground station;

[0027] S4: Extract the EPFD limit curve of this frequency band. EPFD is used to calculate the sum of all power flux densities received by the receiving antennas of geostationary orbit satellites and their earth stations within the reference bandwidth and from different directions at different incidences. The EPFD calculation formula is as follows:

[0028]

[0029] in,

[0030] EPFD is equivalent power flux density, in dB / (W / m 2 );

[0031] N a is the number of low-orbit satellites visible from the Earth's surface or from the receiver of a geostationary satellite system considered in geostationary orbit;

[0032] i is the i-th low-orbit satellite;

[0033] P i is the power at the input port of the low-orbit satellite transmitting antenna within the reference bandwidth, in dBW;

[0034] G t (θ i ) is the transmitting antenna gain of the ith low-orbit satellite in the direction of the receiving end of the geostationary satellite system, in dBi;

[0035] d i is the distance between the low-orbit satellite and the receiving end of the geostationary satellite system, in meters;

[0036] is the receiving antenna gain of the geostationary satellite system receiving end in the direction of the i-th low-orbit satellite, in dBi;

[0037] G r，max is the maximum gain of the receiving antenna of the geostationary satellite system, in dBi;

[0038] S5: Calculate the cumulative probability distribution curve of EPFD complementarity between the NGSO system and the GSO system ground station;

[0039] S6: Comparison of the I / N complementarity cumulative probability distribution curve with the I / N th The spacing between limit curves and EPFD complementary cumulative probability distribution curve and the spacing between EPFD limit curves.

[0040] Preferably, in step S2, n is 3.5, y is 10%, and X is 6%.

[0041] Preferably, in step S6, if the I / N complementary cumulative probability distribution curve is equal to I / Nth If the spacing between the limit curves is greater than the spacing between the EPFD complementary cumulative probability distribution curve and the EPFD limit curve, I / N th As the protection standard of NGSO system for GSO system.

[0042] Preferably, in step S6, if the I / N complementary cumulative probability distribution curve is equal to I / N th If the spacing between the limit curves is less than or equal to the spacing between the EPFD complementary cumulative probability distribution curve and the EPFD limit curve, the EPFD limit is used as the protection standard for the NGSO system to the GSO system.

[0043] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0044] This application mainly aims at the problem of how to quantify the co-frequency interference between satellite communication systems. By judging the interference-to-noise ratio and equivalent power flux density, it provides an interference discrimination method for the interference coordination between non-geostationary orbit satellite constellations and geostationary orbit satellites. The use of this interference discrimination method is more in line with the actual link situation of geostationary orbit satellites, which can effectively improve the coordination efficiency, avoid resource waste, and provide more link margin for the constellation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A limit curve diagram of a single-entry interference-to-noise ratio of a low-orbit constellation system provided in an embodiment of the present invention is shown;

[0046] Figure 2 A schematic diagram of EPFD calculation according to an embodiment of the present invention is shown;

[0047] Figure 3 A flow chart of a method for determining interference of a satellite constellation to a geostationary orbit satellite using an interference-to-noise ratio as a determination criterion provided in an embodiment of the present invention is shown;

[0048] Figure 4 The interference results of a constellation of 108 inclined orbit satellites provided according to an embodiment of the present invention are shown (the ground station antenna aperture is 1 meter);

[0049] Figure 5 The interference results of a constellation of 54 polar-orbit satellites provided according to an embodiment of the present invention are shown (the ground station antenna aperture is 1 meter). DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] See also Figure 1-5 , the present invention provides a technical solution:

[0052] A method for determining co-frequency interference of a satellite constellation to a geostationary orbit satellite comprises the following steps:

[0053] S1: Determine the geostationary satellite system (C / N) cs 、(C / N) bitsync 、(C / N) t , GSO system unavailability P, number of NGSO systems n, percentage of long-term total interference to total noise X;

[0054] S2: Calculate I / N th Limit curve, the calculation formula is as follows:

[0055]

[0056] In the formula,

[0057]

[0058]

[0059] I long-term / N=10long[X / (100n)]

[0060] in,

[0061] I bit-sync / N is the loss of synchronization limit;

[0062] I BER / N is the short-term interference limit;

[0063] I long-term / N is the long-term interference limit;

[0064] The interference to the geostationary satellite link in clear sky Threshold, in dB;

[0065] is the desynchronization threshold of the interfered geostationary orbit satellite link, in dB;

[0066] is the demodulation threshold of the interfered geostationary satellite link, in dB;

[0067] n represents the number of low-orbit constellation systems;

[0068] P is lower than The allowable time percentage of the threshold, i.e., system unavailability, in %;

[0069] y is the percentage of long-term interference time;

[0070] X is the percentage of long-term interference in the total noise;

[0071] N is the noise power of the interfered geostationary satellite system, in dBW;

[0072] S3: Calculate the cumulative probability distribution curve of I / N complementarity between the NGSO system and the GSO system ground station;

[0073] S4: Extract the EPFD limit curve of this frequency band. EPFD is used to calculate the sum of all power flux densities received by the receiving antennas of geostationary orbit satellites and their earth stations within the reference bandwidth and from different directions at different incidences. The EPFD calculation formula is as follows:

[0074]

[0075] in,

[0076] EPFD is equivalent power flux density, in dB / (W / m 2 );

[0077] N a is the number of low-orbit satellites visible from the Earth's surface or from the receiver of a geostationary satellite system considered in geostationary orbit;

[0078] i is the i-th low-orbit satellite;

[0079] P i is the power at the input port of the low-orbit satellite transmitting antenna within the reference bandwidth, in dBW;

[0080] G t (θ i ) is the transmitting antenna gain of the ith low-orbit satellite in the direction of the receiving end of the geostationary satellite system, in dBi;

[0081] d i is the distance between the low-orbit satellite and the receiving end of the geostationary satellite system, in meters;

[0082] is the receiving antenna gain of the geostationary satellite system receiving end in the direction of the i-th low-orbit satellite, in dBi;

[0083] G r，max is the maximum gain of the receiving antenna of the geostationary satellite system, in dBi;

[0084] S5: Calculate the cumulative probability distribution curve of EPFD complementarity between the NGSO system and the GSO system ground station;

[0085] S6: Comparison of the I / N complementarity cumulative probability distribution curve with the I / N th The spacing between limit curves and EPFD complementary cumulative probability distribution curve and the spacing between EPFD limit curves.

[0086] Specifically, Figure 1 , Figure 2 and Figure 3 As shown, in step S2, n is 3.5, y is 10%, and X is 6%. In step S6, if the I / N complementary cumulative probability distribution curve is equal to I / N th If the spacing between the limit curves is greater than the spacing between the EPFD complementary cumulative probability distribution curve and the EPFD limit curve, I / N th As the protection standard of the NGSO system for the GSO system, if the I / N complementary cumulative probability distribution curve is equal to the I / N th If the spacing between the limit curves is less than or equal to the spacing between the EPFD complementary cumulative probability distribution curve and the EPFD limit curve, the EPFD limit is used as the protection standard for the NGSO system to the GSO system.

[0087] The interference determination method of the present invention for different non-geostationary orbit configuration constellations such as polar orbit satellite constellations and inclined orbit satellite constellations is as follows:

[0088] For the inclined orbit constellation, the Walker constellation (N, P, F) parameters are selected as (108, 12, 9), that is, the total number of constellation satellites N is 108, the number of orbital planes P is 12, and the phase factor F is 9. The orbit height h is 1100 km above sea level and the inclination is 50°.

[0089] For polar orbit satellites, the Walker constellation (N, P, F) parameters are selected as (54, 6, 9), that is, the total number of constellation satellites N is 54, the number of orbital planes P is 6, and the phase factor F is 9. The orbit height h is 1100 km above sea level and the inclination is 86°.

[0090] Assume that the earth station of the LEO constellation system is co-located with the earth station of the GEO satellite system, and all LEO satellites are directly pointing at the earth station of the GEO satellite system to interfere (worst case). The interference signal transmitting antenna gain takes the maximum gain, and the receiving antenna gain of the earth station of the GEO satellite system is calculated according to the specific off-axis angle. The interference source of the earth station of the GEO satellite system comes from all visible LEO satellites above the minimum elevation angle (10°).

[0091] TABLE 1 Typical C / N thresholds for geostationary orbit Ka-band downlinks

[0092] <![CDATA[(C / N) cs Threshold]]> <![CDATA[(C / N) t Threshold]]> <![CDATA[(C / N) bitsync Threshold]]> 18.7dB 10.1dB -7dB

[0093] Specifically, Figure 4 and Figure 5 As shown in the figure, the interference situation of 108 inclined orbit satellite constellations (satellite transmission power -26.7609dBW, antenna maximum gain 28.8991dBi) and 54 polar orbit satellite constellations (satellite transmission power -26.7609dBW, antenna maximum gain 28.8991dBi) to the geostationary orbit (113.893 degrees east longitude) Ka-band downlink as shown in Table 1 is calculated according to different interference evaluation indicators. The isolation angle is Isolation angle 6° means when When , the satellites in the satellite constellation system do not transmit power, that is, the power is 0. CCDF is the complementary cumulative distribution function, which represents the sum of the probabilities of occurrence of all values ​​greater than the horizontal axis. It can be seen that as the isolation angle increases, the interference signal gradually decreases until it meets or approaches the EPFD limit. When the actual protection threshold requirement of the geostationary orbit link is low, lower than the protection threshold of the typical link selected when the EPFD limit was originally determined, there will be a situation where the interference signal does not meet the EPFD limit but meets the I / N limit.

[0094] Specifically, Figure 3 As shown, based on the satellite constellation interference determination method flow with the geostationary satellite based on the interference-to-noise ratio as the judgment standard provided by the present invention, the three C / N thresholds are understood in detail, and the evaluation is based on I / N. Compared with only using the EPFD limit, the satellite constellation system resource utilization rate is higher; the present invention mainly focuses on the problem of how to quantify the co-frequency interference between satellite communication systems, and provides an interference determination method for the interference coordination between non-geostationary satellite constellations and geostationary satellites through the determination of the interference-to-noise ratio and the equivalent power flux density. The use of this interference determination method is more in line with the actual link situation of geostationary satellites, can effectively improve the coordination efficiency, avoid resource waste, and provide more link margins for the constellation system.

[0095] The above description of the embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the co-frequency interference of a satellite constellation to a geostationary orbit satellite, characterized in that: The following steps are involved: S1: Determine the geostationary satellite system (C / N) cs 、(C / N) bitsync 、(C / N) t , GSO system unavailability P, number of NGSO systems n, X is the percentage of long-term interference in the total noise; S2: Calculate I / N th Limit curve, the calculation formula is as follows: In the formula, I long-term / N=10log[X / (100n)] in, I bit-sync / N is the loss of synchronization limit; I BER / N is the short-term interference limit; I long-term / N is the long-term interference limit; The interference to the geostationary satellite link in clear sky Threshold, in dB; is the desynchronization threshold of the interfered geostationary orbit satellite link, in dB; is the demodulation threshold of the interfered geostationary satellite link, in dB; n represents the number of low-orbit constellation systems; P is lower than The permissible time percentage of the threshold, i.e., system unavailability, in %; y is the percentage of long-term interference time; X is the percentage of long-term interference in the total noise; C is the effective signal power received by the system, in dBW; I is the interference signal power received by the system, in dBW; t is the time percentage; N is the noise power of the interfered geostationary satellite system, in dBW; S3: Calculate the cumulative probability distribution curve of I / N complementarity between the NGSO system and the GSO system ground station; S4: Extract the EPFD limit curve of the frequency band used by the communication link. EPFD is used to calculate the sum of all power flux densities received by the receiving antennas of geostationary orbit satellites and their earth stations within the reference bandwidth and from different directions at different incidences. The EPFD calculation formula is as follows: in, EPFD is equivalent power flux density, in dB / (W / m 2 ); N a is the number of low-orbit satellites visible from the Earth's surface or from the receiver of a geostationary satellite system considered in geostationary orbit; i is the i-th low-orbit satellite; P i is the power at the input port of the low-orbit satellite transmitting antenna within the reference bandwidth, in dBW; G t (θ i ) is the transmitting antenna gain of the ith low-orbit satellite in the direction of the receiving end of the geostationary satellite system, in dBi; d i is the distance between the low-orbit satellite and the receiving end of the geostationary satellite system, in meters; is the receiving antenna gain of the geostationary satellite system receiving end in the direction of the i-th low-orbit satellite, in dBi; G r，max is the maximum gain of the receiving antenna of the geostationary satellite system, in dBi; S5: Calculate the cumulative probability distribution curve of EPFD complementarity between the NGSO system and the GSO system ground station; S6: Comparison of the I / N complementarity cumulative probability distribution curve with the I / N th The spacing between the limit curve and the EPFD complementary cumulative probability distribution curve and the spacing between the EPFD limit curve; In step S6, if the I / N complementary cumulative probability distribution curve is equal to I / N th If the spacing between the limit curves is greater than the spacing between the EPFD complementary cumulative probability distribution curve and the EPFD limit curve, I / N th As the protection standard of NGSO system to GSO system; In step S6, if the I / N complementary cumulative probability distribution curve is equal to I / N th If the spacing between the limit curves is less than or equal to the spacing between the EPFD complementary cumulative probability distribution curve and the EPFD limit curve, the EPFD limit is used as the protection standard for the NGSO system to the GSO system.

2. The method for determining the co-frequency interference of a satellite constellation to a geostationary orbit satellite according to claim 1, characterized in that: In step S2, n is set to 3.5, y is set to 10%, and X is set to 6%.

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