CN114614884A - Method for continuously covering beam on non-stationary orbit satellite constellation satellite to ground - Google Patents

Method for continuously covering beam on non-stationary orbit satellite constellation satellite to ground Download PDF

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CN114614884A
CN114614884A CN202210267934.6A CN202210267934A CN114614884A CN 114614884 A CN114614884 A CN 114614884A CN 202210267934 A CN202210267934 A CN 202210267934A CN 114614884 A CN114614884 A CN 114614884A
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satellite
coverage
covering
block
earth
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CN114614884B (en
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孙杰
胡建平
李婷
刘田
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CETC 10 Research Institute
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851—Systems using a satellite or space-based relay
    • H04B7/18519—Operations control, administration or maintenance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/195—Non-synchronous stations
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a method for continuously covering beams on a constellation satellite of a non-stationary orbit to the ground, which comprises the following steps: dividing the whole earth surface into a plurality of covering blocks, wherein each covering block is covered by one wave beam of one satellite in a constellation; each satellite in the constellation controls the beam on the satellite to cover the ground according to the earth coverage table and by combining with the ephemeris of the satellite, and when each satellite moves in the visible range corresponding to the coverage block to be covered, the beam direction on the satellite is calculated, and the beam on the satellite is controlled to always point to the area; when the previous satellite in the constellation moves out of the visible range of a certain covering block, the next satellite continues to cover the covering block; the multiple satellites realize continuous coverage of a certain area in time in a mode that the coverage time of two front satellites and the coverage time of two rear satellites are connected end to end; the satellites which are positioned on the same orbit and cover the covering blocks belonging to different covering groups are arranged in a crossed way, so that the satellites sequentially cover the ground areas which are connected geographically, and the surface of the earth is continuously covered spatially according to the above mode.

Description

Method for continuously covering beams on non-stationary orbit satellite constellation satellite to ground
Technical Field
The invention belongs to the technical field of satellite communication, and particularly relates to a beam-to-ground continuous covering method on a constellation satellite of a non-stationary orbit satellite.
Background
During operation, the satellites need to know their precise orbital positions, which information is called ephemeris. The satellite is typically periodically filled by a ground control center.
The angle between the line connecting the satellite and the ground target and the horizon is called the elevation angle of the ground target to the satellite. Since a non-stationary orbiting satellite orbits the earth, a terrestrial target can only communicate wirelessly with the satellite over a limited range of elevation angles, referred to as the visible range of the satellite. The time corresponding to each circle of the visual range is called the visual time.
Satellites generally exchange information with ground-based objects through radio signals, and a radio signal covering a continuous area is called a beam. This area is called the coverage block for this beam of this satellite. The range of the signal strength in the area above a certain threshold is the coverage area of this beam of the satellite. If the satellite has multiple beams, there may be multiple coverage blocks at the same time.
Due to the relative motion to the ground, the geographic position of the satellite beam-to-ground coverage block of the non-stationary orbit satellite changes from moment to moment. When a certain area on the earth surface needs to be continuously covered, a constellation needs to be formed by a plurality of satellites, and the beams of each satellite sequentially cover the area.
The existing non-stationary orbit satellite beam-to-ground coverage is generally realized by adopting a method of beam pointing on a fixed satellite. The method is simple and feasible, but because the satellite movement can cause short ground coverage time of a single satellite, the ground target needs to be frequently switched among beams of a plurality of satellites, the signal transmission quality is possibly reduced, and the switching signaling cost is increased. The existing non-stationary orbit satellite systems such as ORBCOMM, Starlink and the like adopt the method, and the ground target of the Starlink needs to be switched for 3 minutes on average.
Secondly, the initiators of the beam switching process of the existing satellite system are all ground targets, and the most common method is that the ground targets automatically detect the satellite signal intensity and then select a certain satellite according to a certain strategy. This leads to an increase in the complexity of the terrestrial target on the one hand and a different handover strategy selected by different vendors on the other hand, which may lead to a mismatch with the handover strategy on the satellite, resulting in a handover failure.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for continuously covering a beam on a constellation of a non-stationary orbit satellite with respect to the ground, which reduces the switching frequency of the beam when the constellation of the non-stationary orbit satellite continuously covers the ground, effectively reduces the signaling overhead during switching, changes the main body of the switching process from a ground target to the satellite and reduces the participation of the ground target in the switching process.
The purpose of the invention is realized by the following technical scheme:
a method for continuously covering a beam on a constellation of non-stationary orbit satellites on the ground, comprising the following steps:
dividing the whole earth surface into a plurality of covering blocks, wherein each covering block is covered by a satellite beam in a constellation, and the geographical position information of all the covering blocks is represented in a form of a globe covering table and is preset or injected to a satellite;
each satellite in the constellation controls the beam on the satellite to cover the ground according to the earth coverage table and by combining with the ephemeris of the satellite, and when each satellite moves in the visible range corresponding to the coverage block to be covered, the beam direction on the satellite is calculated and is controlled to always point to the area;
when the previous satellite in the constellation moves out of the visible range of a certain covering block, the next satellite continues to cover the covering block; the next satellite controls the satellite beam to always point to the region in the visible range of the region, and a plurality of satellites realize continuous coverage of the region in time in a mode that the coverage time of the front satellite and the rear satellite is end-to-end connected;
the satellites which are positioned on the same orbit and cover the covering blocks belonging to different covering groups are arranged in a crossed way, and sequentially cover the ground areas which are connected geographically, and the surface areas of the earth are continuously covered in space according to the mode.
According to a preferred embodiment, each overlay block corresponds to two numbers: an overlay group number and an overlay block number;
wherein, the coverage group number represents the set of radio parameters used by the corresponding coverage block, and at least includes: frequency, bandwidth, transmit power threshold, receive sensitivity threshold, the same set of radio parameters being used by the terrestrial target and the covering satellite on the coverage block having the same coverage group number;
the covering block number represents the sequence number of the corresponding covering block in the covering group;
and, the corresponding relation between the covering group number and the radio parameter set is preset in the satellite and the ground target in advance.
According to a preferred embodiment, the earth coverage table contains at least the following information: the geographical coordinate positions of all the covering blocks, the covering group numbers of all the covering blocks, the covering block numbers of all the covering blocks, which covering blocks the satellite needs to cover, the size of the covering blocks the satellite needs to cover and the covering time starting and ending points of the covering blocks the satellite needs to cover.
According to a preferred embodiment, the coverage time is: under the condition that the elevation angle of the satellite at any place in the coverage block is greater than or equal to the lowest elevation threshold, the visible time of the satellite is obtained; wherein the lowest elevation threshold is preset to be 5 to 15 degrees.
According to a preferred embodiment, the maximum time t covered by a satellite for a covering block1Comprises the following steps:
Figure BDA0003553137920000041
wherein r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block, β is the initial value of the beam width of the beam on the satellite in the satellite orbit direction, and w is the satellite earth-surrounding operating angular velocity.
According to a preferred embodiment, at the covering time t1The satellite controls and changes the beam direction on the satellite according to the geographical coordinate position of the covering block in the earth covering table and the self ephemeris information, so that the satellite can change the beam direction on the satelliteThe beam is always directed to the covering block; the initial value of the satellite beam width is set according to the size of a covering block in an earth covering table, and then the satellite beam width is adjusted according to ephemeris in the covering time, so that the earth covering range is kept unchanged all the time.
According to a preferred embodiment, the satellites are located on the same orbit in the constellation, and the included angle between the front and rear satellites covering the same covering block and the connecting line of the geocentric is less than or equal to:
Figure BDA0003553137920000042
wherein r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block to the satellite, and β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction.
According to a preferred embodiment, two geographically connected covering blocks belong to different covering groups, satellites which are located in the same orbit and cover the covering blocks belonging to different covering groups are arranged in a crossed manner and sequentially cover the geographically connected covering blocks belonging to different covering groups;
and, lie in same orbital, cover two satellites that belong to different cover groups and two cover pieces that link to each other geographically, and the contained angle less than or equal to with the geocentric:
Figure BDA0003553137920000043
Figure BDA0003553137920000051
wherein r is the earth radius, h is the satellite orbit height, α 1 is the lowest elevation threshold of the satellite in the previous satellite coverage group, β 1 is the initial value of the beam width of the beam on the previous satellite along the satellite orbit direction, α 2 is the lowest elevation threshold of the satellite in the next satellite coverage group, and β 2 is the initial value of the beam width of the beam on the next satellite along the satellite orbit direction.
According to a preferred embodiment, the satellite broadcasts and transmits coverage broadcast messages to a certain coverage block periodically according to the earth coverage table when the coverage of the coverage block is started and during the coverage time of the coverage block, wherein the coverage broadcast messages at least comprise: the number of the coverage group to which the coverage block belongs, the number of the coverage block and the satellite number of the satellite; letting the ground target know the radio parameter set of the coverage block through the coverage group number includes: frequency, bandwidth, transmission power threshold, reception sensitivity threshold; the number of the covering block is known to the ground target through the covering block number, and the ground target is known to which satellite the ground target is communicating with through the satellite number.
According to a preferred embodiment, the satellite broadcasts and transmits a satellite switching message to the corresponding coverage block before the coverage time in the earth coverage table expires, the satellite switching message at least comprising: the satellite number of the satellite and the switching wave beam time of the satellite; after receiving the satellite switching message, the ground target suspends sending information to the satellite until receiving the coverage broadcast message; the value of the switching beam time of the satellite in the satellite switching message is at least 2 times of the maximum propagation delay of the coverage block after the actual sending time of the satellite switching message; if the ground target does not receive the coverage broadcast message after receiving the satellite switching message and switching the time delay threshold, the ground target loses the satellite signal and needs to search the satellite signal again for access.
The aforementioned main aspects of the invention and their respective further alternatives can be freely combined to form a plurality of aspects, all of which are aspects that can be adopted and claimed by the present invention. The skilled person in the art can understand that there are many combinations, which are all the technical solutions to be protected by the present invention, according to the prior art and the common general knowledge after understanding the scheme of the present invention, and the technical solutions are not exhaustive herein.
The invention has the beneficial effects that: the method reduces the frequency of the wave beam switching; the signaling overhead during beam switching is reduced; the problems of transmission quality reduction and transmission interruption caused by beam switching are reduced; the switching main body is changed from a ground target to a satellite, so that the complexity of realizing switching of the ground target is reduced, and the switching success rate is improved.
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Fig. 1 is a schematic diagram of coverage of areas of coverage blocks 1 and 2 belonging to a coverage group 1 by a satellite with a certain satellite number a in the embodiment of the present invention;
FIG. 2 is a schematic diagram of the positions of the same satellite beginning and ending coverage of the same coverage block in an embodiment of the present invention;
fig. 3 is a schematic diagram of two satellites implementing continuous coverage on the coverage block 1 according to the embodiment of the present invention;
FIG. 4 is a schematic diagram of beam switching between two satellites according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of coverage group settings for geographically connected regions in an embodiment of the present invention;
fig. 6 is a schematic diagram illustrating an angle between two satellites belonging to different coverage groups on the same orbit and a ground center connection line according to the embodiment.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that, in order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments.
The invention discloses a method for continuously covering beams on a constellation of a non-stationary orbit satellite to the ground, which comprises the following steps: time-to-ground continuous coverage and space-to-ground continuous coverage.
Firstly, the whole earth surface is divided into a plurality of covering blocks, each covering block is covered by a satellite beam in a constellation, and the geographical position information of all the covering blocks is represented in the form of a ground sphere covering table and is preset or injected to a satellite.
Further, each overlay block corresponds to two numbers: an overlay group number and an overlay block number.
Wherein, the coverage group number represents the radio parameter set used by the corresponding coverage block, and at least comprises: frequency, bandwidth, transmit power threshold, receive sensitivity threshold, terrestrial targets on coverage blocks with the same coverage group number and the covering satellite use the same set of radio parameters. The overlay block number represents the sequential number of the corresponding overlay block within the overlay group. And, the corresponding relation between the covering group number and the radio parameter set is preset in the satellite and the ground target in advance.
Further, the earth coverage table contains at least the following information: the geographical coordinate positions of all the covering blocks, the covering group numbers of all the covering blocks, the covering block numbers of all the covering blocks, which covering blocks the satellite needs to cover, the size of the covering blocks the satellite needs to cover and the covering time starting and ending points of the covering blocks the satellite needs to cover.
The earth coverage table is known to the satellite through presetting or upper notes, and the satellite can only execute according to the earth coverage table and can not modify the earth coverage table.
The geographical coordinate position information of the covering block is generally the coordinate of the central point of the covering block, and longitude and latitude coordinates, geodetic coordinates and the like can be used. The size information of the coverage block can be in the form of the geographic radius of the coverage block or the initial value of the beam width on the satellite.
The covering time is as follows: and under the condition that the elevation angle of the satellite at any place in the coverage block is greater than or equal to the lowest elevation threshold, the visible time of the satellite is obtained. Wherein the lowest elevation threshold is preset to be 5 to 15 degrees.
Maximum coverage time t of a satellite for a coverage block1Comprises the following steps:
Figure BDA0003553137920000081
wherein r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block, β is the initial value of the beam width of the beam on the satellite in the satellite orbit direction, and w is the satellite earth-surrounding operating angular velocity.
And then, each satellite in the constellation controls the beam on the satellite to cover the ground according to the earth coverage table and by combining with the ephemeris, and when each satellite moves in the visible range corresponding to the coverage block to be covered, the beam direction on the satellite is calculated, and the beam on the satellite is controlled to always point to the area.
When the previous satellite in the constellation moves out of the visible range of a certain covering block, the next satellite continues to cover the covering block; the next satellite controls the satellite beam to always point to the region in the visible range of the region, and a plurality of satellites realize continuous coverage of the region in time in an end-to-end mode according to the coverage time of the front satellite and the rear satellite.
Specifically, at the covering time t1The satellite controls and changes the direction of the beam on the satellite according to the geographical coordinate position of the covering block in the earth covering table and the ephemeris information of the satellite, so that the beam on the satellite always points to the covering block; the initial value of the satellite beam width is set according to the size of a covering block in an earth covering table, and then the satellite beam width is adjusted according to ephemeris in the covering time, so that the earth covering range is kept unchanged all the time.
The constellation is positioned on the same orbit, and the included angle between the front and back satellites covering the same covering block and the connecting line of the geocentric is less than or equal to:
Figure BDA0003553137920000082
wherein r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block to the satellite, and β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction. Thereby ensuring that the front and the back satellites are connected end to end in the covering time for the same covering block.
And finally, the satellites which are positioned on the same orbit and cover the covering blocks belonging to different covering groups are arranged in a crossed manner, the covering blocks sequentially cover the ground areas which are connected geographically, and the space of the surface area of the earth is continuously covered according to the above mode.
In particular, two geographically connected covering blocks belong to different covering groups, using different frequency parameters. The satellites which are positioned on the same track and cover the covering blocks belonging to different covering groups are distributed in a crossed way and sequentially cover the covering blocks which are connected geographically and belong to different covering groups.
And, lie in same orbital, cover two satellites that belong to different cover groups and two cover pieces that link to each other geographically, and the contained angle less than or equal to with the geocenter:
Figure BDA0003553137920000091
wherein r is the earth radius, h is the satellite orbit height, α 1 is the lowest elevation threshold of the satellite in the previous satellite coverage group, β 1 is the initial value of the beam width of the beam on the previous satellite along the satellite orbit direction, α 2 is the lowest elevation threshold of the satellite in the next satellite coverage group, and β 2 is the initial value of the beam width of the beam on the next satellite along the satellite orbit direction. Thereby ensuring continuous coverage of the satellite constellation over the earth's surface space.
Preferably, the satellite broadcasts and transmits coverage broadcast messages to a certain coverage block periodically according to the earth coverage table when the coverage of the coverage block is started and during the coverage time of the coverage block, wherein the coverage broadcast messages at least comprise: the number of the coverage group to which the coverage block belongs, the number of the coverage block and the satellite number of the satellite; letting the ground target know the radio parameter set of the coverage block through the coverage group number includes: frequency, bandwidth, transmission power threshold, reception sensitivity threshold; the number of the covering block is known to the ground target through the covering block number, and the ground target is known to which satellite the ground target is communicating with through the satellite number.
Further, the satellite number is unique within the entire constellation of non-stationary orbiting satellites, determined by presets.
Preferably, the satellite broadcasts and transmits a satellite switching message to the corresponding coverage block before the coverage time in the earth coverage table expires, wherein the satellite switching message at least comprises: the satellite number of the satellite and the switching beam time of the satellite. The ground target, upon receiving the satellite handoff message, suspends transmitting information to the satellite until receiving the coverage broadcast message.
And the value of the switching beam time of the satellite in the satellite switching message is at least 2 times of the maximum propagation delay of the coverage block after the actual sending time of the satellite switching message.
The maximum propagation delay of the covering block, namely the maximum radio propagation delay from a satellite to any place in the covering block, is set as r to be the earth radius, h is the satellite orbit height, alpha is the minimum elevation angle threshold of the covering block to the satellite, c is the light speed, and the maximum propagation delay of the covering block is equal to
Figure BDA0003553137920000101
If the ground target does not receive the coverage broadcast message after receiving the satellite switching message and switching the time delay threshold, the ground target loses the satellite signal and needs to search the satellite signal again for access.
The switching delay threshold should be greater than or equal to 2 times the maximum propagation delay of the coverage block minus 1 time the minimum propagation delay of the coverage block, and is
Figure BDA0003553137920000102
The coverage block maximum propagation delay and the coverage block minimum propagation delay are respectively the maximum and minimum radio propagation delay from the satellite to any place in the coverage block.
Thus, the frequency of beam switching is reduced by the method of the invention; the signaling overhead during beam switching is reduced; the problems of transmission quality reduction and transmission interruption caused by beam switching are reduced; the switching main body is changed from a ground target to a satellite, so that the complexity of realizing switching of the ground target is reduced, and the switching success rate is improved.
Example (b):
all areas of the earth's surface that need to be covered are pre-divided into a plurality of covering blocks, the geographic location of each area, etc. are predetermined. The information of the geographic coordinate positions of all the covering blocks, the covering group numbers and the covering block numbers of the covering blocks needing to be covered by the satellite, the sizes of the covering blocks needing to be covered by the satellite, the covering time starting and stopping points of the covering blocks needing to be covered by the satellite and the like are manufactured into an earth covering table and known to the satellite in a preset or upper-noted mode.
One expression form of the earth coverage table is shown in table 1, and specific values in the table are only illustrated, and so on. In the table, the geographic coordinates of the coverage blocks use longitude and latitude coordinates, the numbers of the coverage groups and the coverage blocks use numbers, whether the satellite needs coverage is represented by an English letter Y or N, the size of the coverage blocks is represented by the width of a beam on the satellite, and the start time and the end time of the coverage are represented by a format of year, month, day, hour, minute and second.
The ground target in this embodiment refers to a ground or low-altitude stationary or slowly-moving target communicating with a satellite, and includes a handheld terminal, a vehicle-mounted terminal, an airborne terminal, a ship-mounted terminal, a ground station, and the like.
TABLE 1
Figure BDA0003553137920000111
As shown in fig. 1, a satellite with a satellite number a covers areas of coverage blocks 1 and 2 belonging to coverage group 1. The triangular area under the satellite in the figure represents the satellite beam. The satellite with the satellite number A respectively starts and ends to cover the coverage block number 1 according to the 'coverage time start' and the 'coverage time end' in the earth coverage table, and the elevation angle of the coverage block 1 at the farthest position from the satellite along the satellite orbit direction is exactly equal to the lowest elevation threshold at the two moments.
During the coverage time of the coverage block 1, the satellite a always points to the coverage block 1 according to the self-ephemeris control beam pointing. After the "end of coverage time" in the earth coverage table, the satellite adjusts the beam pointing to the area with coverage group number 1 and coverage block number 2, i.e. the dotted line portion in the figure, according to the earth coverage table. The elevation angle of the covering block 2 that is farthest from the satellite in the satellite orbit direction is also equal to the lowest elevation threshold.
The coverage time is calculated as shown in fig. 2, in the figure, the satellite is the position where the same satellite starts and finishes covering the same coverage block, the solid line triangular area under the satellite is the satellite beam, the dotted line is the satellite orbit, and the dotted line is the connecting line between the satellite and the geocenter. In the figure, points a and B are the elevation angles of the farthest points in the coverage area when the satellite starts and ends coverage, respectively, and are the lowest elevation threshold when the coverage area is circular. In the figure, points C and D are the points under the satellite when the satellite starts and finishes covering, and the time when the satellite passes through the included angle between the points C and D and the earth center is the satellite covering time.
Let r be the earth radius, h be the satellite orbit height, α be the lowest elevation threshold of the covering block to the satellite, β be the initial value of the beam width of the beam on the satellite, n be the angle from the satellite down point to the target point, θ 1 be the angle from the point C to the point a relative to the earth center, and θ 2 be the angle from the point C to the point B relative to the earth center. Theta 1 and theta 2 are respectively equal to the included angles from the point D to the point B and from the point D to the point A relative to the geocentric. The included angle between the C point and the D point relative to the geocentric can be calculated as follows:
Figure BDA0003553137920000121
Figure BDA0003553137920000122
then when the angular velocity of the satellite moving around the earth is w, the coverage time is at most
Figure BDA0003553137920000123
Figure BDA0003553137920000124
Since the shape of the beam on the satellite is generally circular or elliptical, the shape of each covering block is circular or elliptical. When the covering block is circular, the elevation angle at the position farthest away from the satellite along the satellite orbit direction is equal to the lowest elevation threshold. When the covering block is in an ellipse shape, if the covering block is in the ellipse long side along the satellite orbit direction, the elevation angle at the farthest position away from the satellite is also equal to the lowest elevation threshold; if the orbit direction of the satellite is an ellipse short side, the elevation angle at the farthest position from the satellite is larger than the lowest elevation threshold so as to ensure that the elevation angle at any position in the whole coverage block is larger than or equal to the lowest elevation threshold.
As shown in fig. 3. When the satellite with the satellite number a adjusts the beam pointing direction to the coverage block 2, the satellite with the satellite number B points the beam to the coverage block 1 to ensure continuous coverage of the coverage block 1 in time. The satellite with the satellite number A and the satellite with the satellite number B use the same radio parameter sets such as frequency, bandwidth, transmitting power threshold, receiving sensitivity threshold and the like for the coverage block 1 according to the earth coverage table, so that the ground target does not need to change the radio parameters of the ground target in the satellite switching process, and the influence of satellite beam switching on the ground target is reduced to the maximum extent.
The same cover group should satisfy certain requirement and just can realize the end to end of coverage time's contained angle relation of two satellites and geocentric line around being located on same track, specifically do: the latter satellite appears just at the position where the former satellite starts to cover when the former satellite finishes covering. The included angle between the two satellites meeting the condition and the center of the earth connecting line is less than or equal to the included angle between the point C, the point D and the center of the earth connecting line in FIG. 2, which is
Figure BDA0003553137920000131
In the process of switching between two satellites, the former satellite sends satellite switching information to ground broadcast, and the latter satellite sends covering broadcast information. The satellite switching message at least comprises: the satellite number of the satellite and the time for switching the wave beam of the satellite. The overlay broadcast message includes at least: the number of the coverage group to which the coverage block belongs, the number of the coverage block, and the satellite number of the satellite. After receiving the satellite switching message, the ground target suspends data transmission according to the satellite switching time point, and resumes data transmission after receiving the coverage broadcast message, thereby ensuring that the ground target does not lose packets in the satellite switching process. The information interaction process related to the handover process is shown in fig. 4. In fig. 4, satellite i represents a satellite covering a terrestrial target before handover, and satellite i +1 represents a satellite covering a terrestrial target after handover.
Two geographically connected covering blocks must belong to different covering groups, different frequency parameters are adopted to realize frequency division multiplexing, and different satellites are used to realize continuous covering in space. As shown in fig. 5, the 4 geographically connected areas belong to 3 coverage groups, respectively, wherein the first three coverage blocks belong to different coverage groups, and the 4 th coverage block multiplexes coverage group number 1.
The coverage blocks belonging to the coverage group nos. 1, 2, 3 and the coverage block No. 1 are respectively covered by the satellite A, B, C located in the same orbit. When the satellite a finishes covering the area where the coverage group number 1 covers the block number 1, and after the coverage group number 1 covers the area of the block number 2, the coverage group number 1 covers the block number 1 and the next satellite is covered by the process as described in fig. 3. Thus, satellites located in the same orbit and covering coverage blocks belonging to different coverage groups must be crossed and covered in turn by geographically connected coverage blocks.
Note that emphasis is here on "geographically connected coverage blocks", the same coverage group number could also be used if two coverage blocks are geographically adjacent but not connected, but spaced apart.
In practice, in one case, the frequency of the satellite over-ground beam is fixed. Thus, only a few satellites with the same on-satellite beam cover block are covered by the same coverage group number cover block, and other satellites with the same on-satellite beam using another frequency are covered by another coverage group number cover block. These satellites with beams on different frequencies are crossed at different positions on the same orbit and cover in turn geographically connected covering blocks belonging to different covering groups.
When the included angle between two satellites belonging to different coverage groups and the center of the earth which are positioned on the same orbit is smaller than a certain threshold value, the earth coverage blocks of the two satellites can be connected end to end in space, so that continuous coverage in space is realized, and non-overlapping coverage is realized to the maximum extent. Let θAIs the angle between the farthest covering point of the previous satellite to the substellar point and the earth center, thetaBFor the closest coverage point of the latter satelliteThe angle between the point under the star and the geocentric. Let r be the earth radius, h be the satellite orbit height, α 1 be the minimum elevation threshold of the satellite of the previous satellite coverage group, β 1 be the initial value of the beam width of the satellite on-board the satellite, α 2 be the minimum elevation threshold of the satellite of the next satellite coverage group, β 2 be the initial value of the beam width of the satellite on-board the satellite. The threshold value of the included angle between two satellites belonging to different coverage groups on the same orbit and the geocentric connection line is θ shown in fig. 6A-θBCan be obtained by calculation
Figure BDA0003553137920000141
Figure BDA0003553137920000142
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. A method for continuously covering beams on a satellite of a non-stationary orbit satellite constellation to the ground, which is characterized in that the method for continuously covering the beams on the satellite to the ground comprises the following steps:
dividing the whole earth surface into a plurality of covering blocks, wherein each covering block is covered by a satellite beam of a satellite in a constellation, and the geographic position information of all the covering blocks is represented in the form of a terrestrial globe covering table and is preset or injected to the satellite;
each satellite in the constellation controls the beam on the satellite to cover the ground according to the earth coverage table and by combining with the ephemeris of the satellite, and when each satellite moves in the visible range corresponding to the coverage block to be covered, the beam direction on the satellite is calculated, and the beam on the satellite is controlled to always point to the area;
when the previous satellite in the constellation moves out of the visible range of a certain covering block, the next satellite continues to cover the covering block; the next satellite controls the satellite beam to always point to the region in the visible range of the region, and a plurality of satellites realize continuous coverage of the region in time in a mode that the coverage time of the front satellite and the rear satellite is end-to-end connected;
the satellites which are positioned on the same orbit and cover the covering blocks belonging to different covering groups are arranged in a crossed way, and sequentially cover the ground areas which are connected geographically, and the surface areas of the earth are continuously covered in space according to the mode.
2. The method of claim 1, wherein each coverage block corresponds to two numbers: an overlay group number and an overlay block number;
wherein, the coverage group number represents the radio parameter set used by the corresponding coverage block, and at least comprises: frequency, bandwidth, transmit power threshold, receive sensitivity threshold, the same set of radio parameters being used by the terrestrial target and the covering satellite on the coverage block having the same coverage group number;
the covering block number represents the sequence number of the corresponding covering block in the covering group;
and, the corresponding relation between the covering group number and the radio parameter set is preset in the satellite and the ground target in advance.
3. The method of claim 1, wherein the earth coverage table comprises at least the following information: the geographical coordinate positions of all the covering blocks, the covering group numbers of all the covering blocks, the covering block numbers of all the covering blocks, which covering blocks the satellite needs to cover, the size of the covering blocks the satellite needs to cover and the covering time starting and ending points of the covering blocks the satellite needs to cover.
4. The method of claim 3, wherein the coverage time is: under the condition that the elevation angle of the satellite at any place in the coverage block is greater than or equal to the lowest elevation threshold, the visible time of the satellite is obtained; wherein the lowest elevation threshold is preset to be 5 to 15 degrees.
5. The method of claim 4, wherein the maximum coverage time t of a satellite for a coverage block is the longest1Comprises the following steps:
Figure FDA0003553137910000021
wherein r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block, β is the initial value of the beam width of the beam on the satellite in the satellite orbit direction, and w is the satellite earth-surrounding operating angular velocity.
6. The method of claim 3, wherein the beam-to-ground continuous coverage is at a coverage time t1In the interior of said container body,
the satellite controls and changes the direction of the beam on the satellite according to the geographical coordinate position of the covering block in the earth covering table and the ephemeris information of the satellite, so that the beam on the satellite always points to the covering block;
the initial value of the satellite beam width is set according to the size of a covering block in an earth covering table, and then the satellite beam width is adjusted according to ephemeris in the covering time, so that the earth covering range is kept unchanged all the time.
7. The method according to claim 1, wherein the constellation of non-stationary orbit satellites is located on the same orbit, and the angle between the connection line of the front and rear satellites covering the same covering block and the geocentric is smaller than or equal to:
Figure FDA0003553137910000031
wherein r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block to the satellite, and β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction.
8. The method according to claim 1, wherein two geographically connected coverage blocks belong to different coverage groups, and satellites covering coverage blocks belonging to different coverage groups located in the same orbit are alternately arranged to sequentially cover geographically connected coverage blocks belonging to different coverage groups;
and, lie in same orbital, cover two satellites that belong to different cover groups and two cover pieces that link to each other geographically, and the contained angle less than or equal to with the geocentric:
Figure FDA0003553137910000032
wherein r is the earth radius, h is the satellite orbit height, α 1 is the lowest elevation threshold of the satellite in the previous satellite coverage group, β 1 is the initial value of the beam width of the beam on the previous satellite along the satellite orbit direction, α 2 is the lowest elevation threshold of the satellite in the next satellite coverage group, and β 2 is the initial value of the beam width of the beam on the next satellite along the satellite orbit direction.
9. The method of claim 1, wherein the method of beam-to-ground continuous coverage on a constellation of non-stationary orbiting satellites,
when a satellite starts to cover a certain coverage block and within the coverage time of the coverage block, periodically broadcasting and sending a coverage broadcast message to the coverage block according to an earth coverage table, wherein the coverage broadcast message at least comprises: the number of the coverage group to which the coverage block belongs, the number of the coverage block and the satellite number of the satellite;
letting the ground target know the radio parameter set of the coverage block through the coverage group number includes: frequency, bandwidth, transmission power threshold, reception sensitivity threshold; the number of the covering block is known to the ground target through the covering block number, and the ground target is known to which satellite the ground target is communicating with through the satellite number.
10. The method of claim 9, wherein the method of beam-to-ground continuous coverage on a constellation of non-stationary orbiting satellites,
before the coverage time in the earth coverage table is cut off, the satellite broadcasts and sends a satellite switching message to a corresponding coverage block, wherein the satellite switching message at least comprises the following components: the satellite number of the satellite and the switching wave beam time of the satellite;
after receiving the satellite switching message, the ground target suspends sending information to the satellite until receiving the coverage broadcast message;
the value of the switching beam time of the satellite in the satellite switching message is at least 2 times of the maximum propagation delay of the coverage block after the actual sending time of the satellite switching message;
and if the ground target does not receive the coverage broadcast message after receiving the satellite switching message and switching the time delay threshold, losing the satellite signal, and searching the satellite signal again for access.
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