CN109474326A - Beam switching method and device - Google Patents
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- CN109474326A CN109474326A CN201811372600.5A CN201811372600A CN109474326A CN 109474326 A CN109474326 A CN 109474326A CN 201811372600 A CN201811372600 A CN 201811372600A CN 109474326 A CN109474326 A CN 109474326A
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Abstract
The present invention provides a kind of beam switching method and devices, it is related to the technical field of satellite communication, this method comprises: determining the second relative positional relationship of the first relative positional relationship, communication terminal and the satellite of multiple wave beams and satellite respectively when communication terminal is located in the overlay area of multiple wave beams；According to the first relative positional relationship and the second relative positional relationship, the relative positional relationship vector between communication terminal and multiple wave beams is calculated separately；Determine tangential velocity vector of the communication terminal relative to satellite；The angle between tangential velocity vector and relative positional relationship vector is calculated separately, and selects the corresponding wave beam access of the smallest angle.The present invention can select suitable wave beam to access by the relative motion situation of consideration satellite and communication terminal, to increase wave beam residence time, reduce switching times.
Description
Technical Field
The present invention relates to the field of satellite communications technologies, and in particular, to a beam switching method and apparatus.
Background
For geostationary satellites, the coverage of their fixed multi-beam antenna on the satellite is also fixed, similar to terrestrial cellular communication systems, since they are always stationary relative to the ground. The beam switching can be performed with reference to terrestrial technology for the mobile communication terminal. The fixed multi-beam antenna is applied to a non-stationary orbit satellite communication system, and because the non-stationary orbit satellite moves relative to the ground and the attitude changes along with time, the coverage wave position of the multi-beam antenna on the ground can move and rotate along with the non-stationary orbit satellite. Particularly for low orbit satellites, the ground communication terminal frequently switches beams due to the fast movement speed of the low orbit satellites. For a fixed multi-beam satellite system, the ground communication terminal is often located in multiple coverage areas with multiple selectable beams during beam switching. In general, the ground communication terminal selects a beam closer to the center of the beam to access, and a situation of accessing a certain beam for a short time may occur, so that the number of times of beam switching is increased. In order to improve the performance of a satellite communication system, increase the residence time of a communication terminal in a single beam and reduce the times of beam switching, the method has important research significance, and at present, a better scheme is not proposed.
Disclosure of Invention
In view of the above, the present invention provides a method and an apparatus for beam switching to increase the residence time of a communication terminal in a single beam and reduce the number of times of beam switching.
In a first aspect, an embodiment of the present invention provides a beam switching method, where the method includes: when the communication terminal is located in the coverage range of the plurality of beams, respectively determining a first relative position relationship between the plurality of beams and the satellite and a second relative position relationship between the communication terminal and the satellite; respectively calculating relative position relation vectors between the communication terminal and the plurality of beams according to the first relative position relation and the second relative position relation; determining a tangential velocity vector of the communication terminal relative to the satellite; and respectively calculating the included angle between the tangential velocity vector and the relative position relation vector, and selecting the beam corresponding to the minimum included angle for access.
With reference to the first aspect, an embodiment of the present invention provides a first possible implementation manner of the first aspect, where the step of determining a first relative positional relationship between a plurality of beams and a satellite and a second relative positional relationship between a communication terminal and the satellite respectively includes: establishing a satellite coordinate system; the satellite coordinate system takes the mass center of the satellite as an origin, the Z axis points to the geocentric, the X axis is the speed direction of the satellite, and the Y axis direction is determined according to the Z axis and the X axis direction; respectively determining a first relative position relation between the plurality of beams and the satellite and a second relative position relation between the communication terminal and the satellite according to the pitch angle and the azimuth angle; the pitch angle is the complementary angle of the included angle between the beam or the communication terminal and the Z axis, and the azimuth angle is the included angle between the projection of the beam or the communication terminal on the plane where the X axis and the Y axis are located and the X axis.
With reference to the first aspect, an embodiment of the present invention provides a second possible implementation manner of the first aspect, where the step of calculating a relative position relationship vector between the communication terminal and each of the plurality of beams according to the first relative position relationship and the second relative position relationship includes:
respectively calculating relative position relation vectors between the communication terminal and the plurality of beams according to the following formula:
wherein,is a vector of relative positional relationships between the communication terminal and the beam i, EliElevation angle, Az, being the beam centre of the beamiIn azimuth of the beam center of the beam, El (t)k) Is at tkThe pitch angle of the communication terminal at the moment, Az (t)k) Is at tkThe azimuth of the communication terminal at the moment.
With reference to the first aspect, an embodiment of the present invention provides a third possible implementation manner of the first aspect, where the step of determining a tangential velocity vector of the communication terminal with respect to the satellite includes: calculating the relative movement speed of the communication terminal relative to the satellite according to the satellite and the current time speed of the communication terminal; and taking the tangential component of the relative motion speed on a connecting line of the communication terminal and the satellite as a tangential speed vector of the communication terminal relative to the satellite.
With reference to the first aspect, an embodiment of the present invention provides a fourth possible implementation manner of the first aspect, where the step of determining a tangential velocity vector of the communication terminal with respect to the satellite includes: and calculating the tangential velocity vector of the communication terminal relative to the satellite according to the relative position relation between the communication terminal and the satellite at a plurality of time points before the current time.
With reference to the first aspect, an embodiment of the present invention provides a fifth possible implementation manner of the first aspect, where the steps of calculating an included angle between the tangential velocity vector and the relative position relationship vector, and selecting a beam corresponding to a minimum included angle to access include: the included angle is calculated according to the following formula:wherein,is the angle between the tangential velocity vector and the relative positional relationship vector,is a relative positional relationship vector between the communication terminal and the beam i,is at tkA tangential velocity vector of the time communication terminal relative to the satellite; and selecting the beam corresponding to the minimum included angle for access.
With reference to the first aspect, an embodiment of the present invention provides a sixth possible implementation manner of the first aspect, where before the steps of determining a first relative positional relationship between a plurality of beams and a satellite and determining a second relative positional relationship between a communication terminal and the satellite when the communication terminal is located in a coverage area of the plurality of beams, the method further includes: acquiring a first relative position relation and a second relative position relation at the current moment; calculating the angular distance between the communication terminal and the wave beam center of the wave beam according to the first relative position relation and the second relative position relation; the angular distance is used for describing the relative position relation between the communication terminal and the beam center of the beam; judging whether the communication terminal is in the coverage range of the accessed wave beam at the last moment according to the angular distance, the shape of the wave beam and the field angle: if yes, the beam is still accessed without beam switching; and if not, determining the beam switching method according to the number of the beams covering the communication terminal.
With reference to the first aspect and the sixth possible implementation manner of the first aspect, an embodiment of the present invention provides a seventh possible implementation manner of the first aspect, where the first relative position relationship and the second relative position relationship are based oni(tk) The step of calculating the angular distance between the communication terminal and the beam center of the beam by the second relative positional relationship includes: the angular separation is calculated according to the following formula:
wherein d isi(tk) Is at tkThe angular distance of the communication terminal from the beam i.
In a second aspect, an embodiment of the present invention further provides a beam switching apparatus, including: the position relation module is used for respectively determining a first relative position relation between the plurality of beams and the satellite and a second relative position relation between the communication terminal and the satellite when the communication terminal is positioned in the coverage range of the plurality of beams; the relative position relation vector module is used for respectively calculating relative position relation vectors between the communication terminal and the plurality of beams according to the first relative position relation and the second relative position relation; the tangential velocity vector module is used for determining a tangential velocity vector of the communication terminal relative to the satellite; and the switching module is respectively used for calculating the included angle between the tangential velocity vector and the relative position relation vector and selecting the beam corresponding to the minimum included angle for access.
With reference to the second aspect, an embodiment of the present invention provides a first possible implementation manner of the second aspect, where the apparatus further includes a determining module, configured to: acquiring a first relative position relation and a second relative position relation at the current moment; calculating the angular distance between the communication terminal and the wave beam according to the first relative position relation and the second relative position relation; the angular distance is used for describing the relative position relation between the communication terminal and the wave beam; judging whether the communication terminal is in the coverage range of the accessed wave beam at the last moment according to the angular distance, the shape of the wave beam and the field angle: if yes, the beam is still accessed without beam switching; and if not, determining the beam switching method according to the number of the beams covering the communication terminal.
The embodiment of the invention has the following beneficial effects: the embodiment of the invention provides a beam switching method and a device, when a communication terminal enters a plurality of ranges covered by a plurality of beams, a relative position relation vector between the communication terminal and each beam is obtained by respectively calculating a first relative position relation between each beam covering the communication terminal and a satellite and a second relative position relation between the communication terminal and the satellite, and finally, the beam corresponding to the minimum included angle is selected for access by calculating a tangential velocity vector and an included angle between the tangential velocity vector and each relative position relation vector. The invention can select proper wave beam to access by considering the relative motion condition of the satellite and the communication terminal, thereby increasing the wave beam residence time and reducing the switching times.
Additional features and advantages of the disclosure will be set forth in the description which follows, or in part may be learned by the practice of the above-described techniques of the disclosure, or may be learned by practice of the disclosure.
In order to make the aforementioned objects, features and advantages of the present disclosure more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart of a beam switching method according to an embodiment of the present invention;
fig. 2 is a schematic diagram illustrating a beam center position of a beam switching method according to an embodiment of the present invention;
fig. 3 is a schematic diagram of beam switching in the beam switching method according to the embodiment of the present invention;
fig. 4 is a flow chart of a beam switching strategy of the beam switching method according to an embodiment of the present invention, in which the parallelism between the movement direction of the communication terminal and the beam center pointing direction is taken into consideration;
FIG. 5 is a schematic diagram of an example of beam switching of an earth station according to the beam switching method provided in the embodiment of the present invention;
fig. 6 is a schematic block diagram of a beam switching apparatus according to an embodiment of the present invention.
Icon:
1-satellite coverage area; 2-point under the star; 3-beam center projection; 4-mapping track of communication terminal relative satellite motion; 5-the movement trajectory of the earth station with respect to the satellite; 9-partial beam enlargement; 61-position relationship module; 62-relative position relation vector module; 63-tangential velocity vector module; 64-switching module.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any creative effort, shall fall within the protection scope of the present invention.
Currently, with the increasing maturity of wireless communication systems, spectrum resources are increasingly strained. The problem of limited spectrum resources is particularly prominent in the development of satellite communication technology. How to reasonably and efficiently allocate resources, improve the capacity of a satellite communication system and improve the utilization rate of frequency spectrum on the premise of limited frequency spectrum resources becomes a problem to be solved urgently. Satellite multi-beam communication technology arose.
The traditional satellite single-beam antenna technology has the characteristics of single beam and large field angle coverage, the system is simple, and the problems of low signal power specific density, low signal-to-noise ratio, low frequency spectrum utilization rate and the like exist. Unlike satellite single beam antenna technology, satellite multi-beam antennas are composed of several high-gain narrow beams, which together form high-gain coverage over a large range. Wherein a single narrow beam can be shaped according to actual requirements. The satellite multi-beam antenna has the characteristics of space isolation and frequency reuse among beams, and can effectively improve the system communication capacity and increase the available bandwidth and the spectrum utilization efficiency.
Based on this, the method and the device for switching beams provided by the embodiments of the present invention can select a beam with the highest parallelism between the motion direction of the ground communication terminal and the beam center pointing direction, considering the relative motion relationship between the satellite and the communication terminal when there are multiple choices for the ground communication terminal during beam switching in a satellite system using fixed multi-beams. The strategy can remarkably increase the residence time of the communication terminal in a single beam and reduce the beam switching times.
For the convenience of understanding the present embodiment, a detailed description will be first given of a beam switching method disclosed in the present embodiment.
Example 1
An embodiment 1 of the present invention provides a beam switching method, which is described in a flow chart of the beam switching method shown in fig. 1, and the method includes the following steps:
the beam switching method designed by the embodiment of the invention mainly considers the relative motion relationship between the satellite and the communication terminal, and can be applied to a non-stationary orbit satellite system adopting a fixed multi-beam antenna and a fixed multi-beam geostationary satellite communication system for providing service for the communication terminal moving at a high speed. The strategy has no special requirements on the shape and the beam arrangement of the satellite beam and is suitable for various beam arrangement conditions.
Step S102, when the communication terminal is located in the coverage area of the plurality of beams, a first relative position relation between the plurality of beams and the satellite and a second relative position relation between the communication terminal and the satellite are respectively determined.
The communication terminal may be a satellite user terminal or an earth station. In order to avoid the problem of frequent switching back and forth of a beam, which may occur when a communication terminal crosses the beam overlapping area, the communication terminal is specified to access the beam all the time in the coverage area of the current beam until leaving the coverage area of the beam and then switch to other beams. Taking beam # i as an example, assume that the current time tkAnd the communication terminal accesses the beam # i, if the communication terminal is still in the coverage range of the beam at the next moment, the communication terminal still accesses the beam # i, otherwise, the communication terminal needs to be switched to other beams. When the communication terminal is switched to a beam, if only one beam covers the communication terminal, the communication terminal is switched to the only accessible beam, and when the communication terminal is located in the coverage range of a plurality of beams, the first relative position relation and the second relative position relation need to be calculated.
The first relative positional relationship is used to describe the relative positional relationship between the beam and the satellite, and for the case where a plurality of beams together form a coverage for the communication terminal, the first relative positional relationship between each beam and the satellite may be calculated separately, and the second relative positional relationship is used to describe the relative positional relationship between the communication terminal and the satellite.
Since the communication terminal is moving relative to the satellite and its position also changes with time, in order to better describe the position relationship between the beam and the communication terminal, in step S102, the step of determining a first relative position relationship between the plurality of beams and the satellite and a second relative position relationship between the communication terminal and the satellite respectively includes:
(1) establishing a satellite coordinate system; the satellite coordinate system takes the center of mass of the satellite as an origin, the Z axis points to the earth center, the X axis is the speed direction of the satellite, and the Y axis direction is determined according to the directions of the Z axis and the X axis.
And aiming at a fixed multi-beam satellite system, establishing a description mechanism of a corresponding beam center and a communication terminal position under a satellite body coordinate system. Referring to the beam center position description diagram shown in fig. 2, a satellite is established with the center of mass of the satellite as the originA satellite coordinate system, wherein the Z axis points to the earth center, and the projection point O' of the Z axis on the satellite coverage area 1 is a subsatellite point 2, PiFor the beam center projection 3, the X-axis is the satellite velocity direction, and the Y-axis direction is obtained by combining the Z-axis and X-axis directions by the "right-hand rule".
(2) Respectively determining a first relative position relation between the plurality of beams and the satellite and a second relative position relation between the communication terminal and the satellite according to the pitch angle and the azimuth angle; the pitch angle is the complementary angle of the included angle between the beam or the communication terminal and the Z axis, and the azimuth angle is the included angle between the projection of the beam or the communication terminal on the plane where the X axis and the Y axis are located and the X axis.
The pointing direction of the beam center of the satellite on-satellite beam # i can be represented by the pitch and azimuth angles: elevation angle EliThe complementary angle (the value range is 0-90 degrees) of the included angle between the central axis of the wave beam and the positive direction of the Z axis, and the azimuth angle AziThen the projection of the beam central axis on the XOY plane is at an angle (in the range of 0-360) to the positive X-axis direction.
The pitch angle El of the beam central axis of the beam # i on the satellite in the satellite coordinate system is knowniAnd azimuth AziThe relative position relationship between the beam central axis and the satellite is also determined, i.e., the first relative position relationship is determined. Similarly, the relative position relationship between the communication terminal and the satellite can also be described by using the same description mechanism, i.e. the second relative position relationship is also determined. Since the communication terminal is moving relative to the satellite, its position also changes with time. At tkThe position direction of the communication terminal relative to the satellite may be the pitch angle El (t) of the "satellite-communication terminal" line of sight direction in the satellite coordinate system at the timek) And azimuth Az (t)k) To describe. See the beam switching diagram shown in fig. 3, P0、P1、P2The beam centers of beams #0, #1, and #2, respectively, have been previously accessed by the communication terminal to beam # 0. At tkAt the moment, the communication terminal is locatedAt this time, the communication terminal is out of the coverage area of the beam #0 and is located in the coverage overlapping area of the beams #1 and # 2. Using the description mechanism of step 1, using pitch angle-azimuth angle [ El1,Az1]、[El2,Az2]、[El(tk),Az(tk)]Respectively representing the central axes of the beam beams #1 and #2 and the relative position relationship between the communication terminal and the satellite at the current moment, namely obtaining a first relative position relationship and a second relative position relationship.
Step S104, respectively calculating relative position relation vectors between the communication terminal and the plurality of beams according to the first relative position relation and the second relative position relation.
The step of calculating a relative positional relationship vector between the communication terminal and the plurality of beams, respectively, based on the first relative positional relationship and the second relative positional relationship, includes:
respectively calculating relative position relation vectors between the communication terminal and the plurality of beams according to the following formula:
wherein,is a vector of relative positional relationships between the communication terminal and the beam i, EliElevation angle of beam center, Az, of beam iiAzimuth of the beam center of beam i, El (t)k) Is at tkThe pitch angle of the communication terminal at the moment, Az (t)k) Is at tkThe azimuth of the communication terminal at the moment.
For example: calculating a characterization tkVector of relative position relationship between time communication terminal and central axes of beams #1 and #2
Step S106, determining the tangential velocity vector of the communication terminal relative to the satellite.
Determining that the communication terminal is at tkTangential velocity vector of time of day relative to satelliteDifferent calculation methods can be employed:
the step of determining the tangential velocity vector of the communication terminal with respect to the satellite may comprise: calculating the relative movement speed of the communication terminal relative to the satellite according to the current time speeds of the satellite and the communication terminal; and taking the tangential component of the relative motion speed on a connecting line of the communication terminal and the satellite as a tangential speed vector of the communication terminal relative to the satellite.
The step of determining the tangential velocity vector of the communication terminal with respect to the satellite may also comprise: and calculating the tangential velocity vector of the communication terminal relative to the satellite according to the relative position relation between the communication terminal and the satellite at a plurality of time points before the current time.
For example, at t may be based on the communication terminalkAnd carrying out differential processing on the relative position relationship between the communication terminal and the satellite at a plurality of time points before the time to obtain the tangential velocity vector.
And step S108, respectively calculating included angles between the tangential velocity vectors and the relative position relation vectors, and selecting the beam corresponding to the minimum included angle for access.
The beam switching diagram shown in fig. 3, see mapped trajectory 4 of the communication terminal with respect to the satellite motion,for communication terminals at tkThe direction of motion of the relative satellite at the time;is at tkThe beam #1 at the moment points to the beam center of the communication terminal;is at tkThe beam #2 at the time point points to the beam center of the communication terminal;the included angle between the movement direction of the communication terminal and the center pointing direction of the wave beam #1 is formed;the included angle between the moving direction of the communication terminal and the center pointing direction of the wave beam #2 is shown.
In obtaining a vectorAnd tangential velocity vector with respect to satelliteAnd then, respectively carrying out vector dot product operation, and selecting the beam with the highest parallelism between the motion direction of the communication terminal and the beam center pointing direction for accessing. The corresponding vector included angle represents the parallelism between the movement direction of the communication terminal and the pointing direction of the center of each wave beam, and the smaller the included angle is, the higher the parallelism is. The beam with the highest parallelism of the movement direction of the communication terminal and the beam center direction is the beam corresponding to the smallest included angle.
Respectively calculating included angles between the tangential velocity vectors and the relative position relation vectors, and selecting the wave beam corresponding to the minimum included angle to access, wherein the step comprises the following steps of:
the included angle is calculated according to the following formula:wherein,is the angle between the tangential velocity vector and the relative position relationship vector,is a relative positional relationship vector between the communication terminal and the beam i,is at tkA tangential velocity vector of the time of day communication terminal relative to the satellite; and selecting the beam corresponding to the minimum included angle for access.
The included angle between the relative position relation vector between the communication terminal and the beams #1 and #2 and the tangential velocity vector of the communication terminal relative to the satellite are respectively calculated, and the following calculation results: referring to the schematic diagram of beam switching shown in FIG. 3, at an included angleAndand selecting the minimum beam and selecting the beam corresponding to the minimum included angle to access.
The embodiment of the invention provides a wave beam switching method, when a communication terminal enters a region covered by a plurality of wave beams, a relative position relation vector between the communication terminal and each wave beam is obtained by respectively calculating a first relative position relation between each wave beam covering the communication terminal and a satellite and a second relative position relation between the communication terminal and the satellite, and finally, the wave beam corresponding to the minimum included angle is selected to be accessed by calculating a tangential velocity vector and an included angle between the tangential velocity vector and each relative position relation vector. The invention can select proper wave beam to access by considering the relative motion condition of the satellite and the communication terminal, thereby increasing the wave beam residence time and reducing the switching times.
In order to determine the time when the beam switching starts, before the steps of determining a first relative positional relationship between the plurality of beams and the satellite and determining a second relative positional relationship between the communication terminal and the satellite when the communication terminal is located within the coverage area of the plurality of beams, the method further comprises:
(1) and acquiring a first relative position relation and a second relative position relation at the current moment.
(2) Calculating the angular distance between the communication terminal and the beam center of the beam according to the first relative position relation and the second relative position relation; the angular separation is used to describe the relative positional relationship between the communication terminal and the beam center of the beam.
Knowing the beam center pointing direction of the beam # i and the position pointing direction of the communication terminal with respect to the satellite, the angular distance d can be calculatedi(tk) To describe the communication terminal at tkThe relative position of the time instant to the beam # i.
The method comprises the following steps: the angular separation is calculated according to the following formula:
wherein d isi(tk) Is at tkThe angular distance of the communication terminal from the beam # i.
(3) Judging whether the communication terminal is in the coverage range of the accessed wave beam at the last moment according to the angular distance, the shape of the wave beam and the field angle: if yes, the beam is still accessed without beam switching; and if not, determining the beam switching method according to the number of the beams covering the communication terminal.
If the beam is a circular spot beam, assume the beam # i has an opening angle θ, if di(tk)<Theta then considers the communication terminal at tkAt time instant in beam # iOtherwise, beam # i is at tkThe communication terminal cannot be covered at all times. And if the beam projection is a non-circular shaped beam, judging whether the beam can cover the communication terminal according to the direction of the communication terminal relative to the beam center at the current moment and the beam range of the beam in the corresponding direction.
The method for determining the beam switching according to the number of the beams covering the communication terminal may be: if the number of the wave beams covering the communication terminal is unique, the communication terminal is switched to the unique accessible wave beams; if the communication terminal is located in the coverage range of two or more wave beams, namely when various choices exist, the relative motion relation between the satellite and the communication terminal is considered, and the wave beam with the highest parallelism between the motion direction of the communication terminal and the center pointing of the wave beam is selected to be accessed.
Referring to a beam switching strategy flow chart of fig. 4, which considers parallelism of a movement direction of a communication terminal and a beam center pointing direction, the present invention proposes a beam switching strategy considering a relative movement relationship between a satellite and a communication terminal, and selects a beam having the highest parallelism of the movement direction of the communication terminal and the beam center pointing direction, considering relative movement between the satellite and the communication terminal, in a case where a plurality of types of beam selections exist when the communication terminal switches beams in a fixed multi-beam satellite system. Compared with the existing beam switching strategy, the method considers the relative motion condition of the satellite and the communication terminal, can effectively avoid the condition that the communication terminal accesses a certain beam momentarily, obviously increases the residence time of the communication terminal in a single beam, and reduces the beam switching times.
Example 2
An embodiment 2 of the present invention provides a beam switching method, which is described in an example schematic diagram of beam switching of an earth station shown in fig. 5, and the method includes the following specific implementation steps:
the constellation orbit parameters of the non-stationary orbit satellite communication system are as follows: the number of the satellites is 8, the long half axis is 26561.78km, the orbit period is 1/2 sidereal days, the inclination angle is 53.13 degrees, the eccentricity is 0, the ascension interval of the ascending point is 45 degrees, and the angle difference between the horizontal point and the near point is 90 degrees; 642 earth stations are uniformly distributed in the world by using an equal area division method, the minimum working elevation angle of the earth stations is 10 degrees, each earth station is accessed by selecting one wave beam in one satellite with the best elevation angle all the time, and each satellite is provided with 121 circular fixed point wave beams.
Selecting the time of one orbit period as the total simulation duration, adopting the strategy of the invention, and completing the corresponding simulation according to the following steps (taking an earth station as an example):
(1) obtaining the azimuth angle of the center of each beam relative to the satellite according to the arrangement of 121 fixed beams
-sequence of pitch angles [ Eli,Azi]And i is 1,2, …,121 (fixed beam, pointing invariant over time), the communications terminal describes the relative positional relationship of the center of each beam and the satellite.
(2) For tkAt any moment, the azimuth angle [ El (t) of the earth station under the satellite body coordinate can be calculated according to the position coordinates of the earth station and the accessed satellite under the earth fixed connection coordinate systemk),Az(tk)]And thus is used to describe the relative positional relationship of the earth station and the satellite.
(3) And calculating the angular distance from the earth station to the central axis of each beam by using the relative position relationship, and comparing the angular distance with the beam opening angle so as to judge the coverage range of the earth station in which beams are covered.
(4) If the earth station is at tk-1The earth station still accesses the wave beam at the current moment in the coverage range of the wave beam accessed at the moment, namely the earth station does not generate wave beam switching; if the earth station is not at tk-1Within the coverage of the beam accessed at the moment, i.e. the earth station needs to switch the beam, then:
① if the earth station is only within the coverage of one beam at the current time, the earth station switches directly to that beam;
② if the earth station is in the coverage of two or more wave beams at present, that is, there are many choices (if there are M choices), the relative motion relation between satellite and earth station is considered, the wave beam access with the highest parallelism between the motion direction of communication terminal and the wave beam center is chosenFinally, the tangential velocity component is dividedAnd performing vector dot product operation with the M vectors obtained before, and selecting the beam with the highest parallelism between the motion direction of the communication terminal and the beam center pointing direction for accessing, namely accessing the beam with the smallest corresponding vector included angle.
(5) And k ← k +1, and repeating the step (2) until the simulation is finished.
In addition, the strategy of selecting the beam closest to the beam center for access is used as comparison, the time length is used as the simulation of one orbit period, the shortest beam residence time of each earth station when different schemes are adopted is counted, and the performances of the two schemes are compared.
The beam switching situation of a single earth station is first analyzed. Referring to the schematic diagram of the example of the earth station beam switching shown in fig. 5, the analyzed earth station is set at 90 ° E,74.1413 ° S, and at the moment 1:04:51 in the simulation process, referring to the movement locus 5 of the earth station relative to the satellite, the earth station leaves the beam #14 of the 6 th satellite, and the beam needs to be switched, and there are two options. As shown in fig. 5, referring to the partial beam enlargement schematic part 9, with the contrast scheme, since the earth station is closer to the beam center of the beam #5 when it leaves the edge of the beam #14, the earth station will access the beam #5 for a short time, until it leaves its coverage range and then accesses the beam #15, that is, the sequence of accessing the beam is 14 → 5 → 15, and 2 times of beam switching occur; when the scheme provided by the invention is adopted, the relative satellite motion direction of the earth station is higher in parallelism with the beam center pointing direction of the beam #15, so that the earth station is switched to the beam #15 until the earth station leaves the beam coverage range, namely the sequence of accessing the beam is 14 → 15, and 1-time beam switching is carried out totally.
The statistical result of the residence time of the shortest wave beam of the global earth station is analyzed, so that the residence time of the shortest wave beam of each earth station is integrally improved by adopting the scheme of the invention compared with the situation of adopting the comparison scheme; the minimum value of the shortest residence time of all the earth stations is 36s when the contrast scheme is adopted, and the minimum value of the shortest residence time of all the earth stations is 73s when the scheme provided by the invention is adopted, so that the improvement is nearly 1 time.
Through the analysis, the beam switching strategy considering the relative motion relationship between the satellite and the communication terminal, which is provided by the invention, can effectively avoid the situation that the communication terminal accesses a certain beam momentarily, obviously increase the residence time of the communication terminal in a single beam and further reduce the beam switching times.
Example 3
Embodiment 3 of the present invention provides a beam switching apparatus, which, referring to a schematic block diagram of a beam switching apparatus shown in fig. 6, includes the following modules:
a position relation module 61, configured to determine a first relative position relation between the plurality of beams and the satellite and a second relative position relation between the communication terminal and the satellite when the communication terminal is located within the coverage area of the plurality of beams, respectively; a relative position relation vector module 62, configured to calculate, according to the first relative position relation and the second relative position relation, a relative position relation vector between the communication terminal and the plurality of beams, respectively; a tangential velocity vector module 63 for determining a tangential velocity vector of the communication terminal relative to the satellite; and the switching module 64 is used for calculating an included angle between the tangential velocity vector and the relative position relation vector respectively, and selecting a beam corresponding to the minimum included angle for access.
The apparatus further comprises a determining module configured to: acquiring a first relative position relation and a second relative position relation at the current moment; calculating the angular distance between the communication terminal and the wave beam according to the first relative position relation and the second relative position relation; the angular distance is used for describing the relative position relation between the communication terminal and the wave beam; judging whether the communication terminal is in the coverage range of the accessed wave beam at the last moment according to the angular distance, the shape of the wave beam and the field angle: if yes, the beam is still accessed without beam switching; and if not, determining the beam switching method according to the number of the beams covering the communication terminal.
The beam switching apparatus provided in the embodiment of the present invention has the same implementation principle and technical effect as those of the beam switching method embodiment, and for brief description, reference may be made to the corresponding contents in the beam switching method embodiment for the part where the embodiment of the beam switching apparatus is not mentioned.
Finally, it should be noted that: the above-mentioned embodiments are merely specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: those skilled in the art can still make modifications or changes to the technical solutions described in the foregoing embodiments or make equivalent substitutions for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A method of beam switching, comprising:
when a communication terminal is located in the coverage range of a plurality of beams, respectively determining a first relative position relationship between the plurality of beams and a satellite and a second relative position relationship between the communication terminal and the satellite;
respectively calculating relative position relation vectors between the communication terminal and the plurality of beams according to the first relative position relation and the second relative position relation;
determining a tangential velocity vector of the communication terminal relative to the satellite;
and respectively calculating included angles between the tangential velocity vectors and the relative position relation vectors, and selecting the beam corresponding to the minimum included angle for access.
2. The beam switching method according to claim 1, wherein the step of determining a first relative positional relationship between the plurality of beams and a satellite and a second relative positional relationship between the communication terminal and the satellite, respectively, comprises:
establishing a satellite coordinate system; the satellite coordinate system takes the center of mass of the satellite as an origin, the Z axis points to the geocentric, the X axis is the speed direction of the satellite, and the Y axis direction is determined according to the Z axis and the X axis direction;
determining a first relative position relation between the plurality of beams and the satellite and a second relative position relation between the communication terminal and the satellite according to the pitch angle and the azimuth angle; the pitch angle is a complementary angle of an included angle between the beam or the communication terminal and the Z axis, and the azimuth angle is an included angle between a projection of the beam or the communication terminal on a plane where the X axis and the Y axis are located and the X axis.
3. The beam switching method according to claim 1, wherein the step of calculating a relative positional relationship vector between the communication terminal and the plurality of beams based on the first relative positional relationship and the second relative positional relationship, respectively, comprises:
calculating relative positional relationship vectors between the communication terminal and the plurality of beams, respectively, according to the following formula:
wherein,for relative position between communication terminal and beam iRelation vector, EliIs the pitch angle of the beam center, Az, of the beamiIs the azimuth angle of the beam center of the beam, El (t)k) Is at tkThe pitch angle of the communication terminal at the moment, Az (t)k) Is at tkThe azimuth of the communication terminal at the moment.
4. The beam switching method of claim 1 wherein said step of determining a tangential velocity vector of said communication terminal with respect to said satellite comprises:
calculating the relative movement speed of the communication terminal relative to the satellite according to the satellite and the current time speed of the communication terminal;
and taking the tangential component of the relative motion speed on a connecting line of the communication terminal and the satellite as the tangential velocity vector of the communication terminal relative to the satellite.
5. The beam switching method of claim 1 wherein said step of determining a tangential velocity vector of said communication terminal with respect to said satellite comprises:
and calculating the tangential velocity vector of the communication terminal relative to the satellite according to the relative position relation between the communication terminal and the satellite at a plurality of time points before the current time.
6. The method according to claim 1, wherein the step of calculating the included angle between the tangential velocity vector and the relative position relationship vector, and selecting the minimum beam corresponding to the included angle to access comprises:
calculating the included angle according to the following formula:
wherein,is the angle between the tangential velocity vector and the relative positional relationship vector,is a relative positional relationship vector between the communication terminal and the beam i,is at tkA tangential velocity vector of the time of day communications terminal relative to the satellite;
and selecting the beam corresponding to the minimum included angle for access.
7. The method of claim 1, wherein the steps of determining a first relative positional relationship between a plurality of beams and a satellite and determining a second relative positional relationship between the communication terminal and the satellite when the communication terminal is located within the coverage area of the plurality of beams, respectively, are preceded by the step of:
acquiring the first relative position relation and the second relative position relation at the current moment;
calculating the angular distance between the communication terminal and the beam center of the beam according to the first relative position relation and the second relative position relation; the angular distance is used for describing a relative position relation between the communication terminal and the beam center of the beam;
judging whether the communication terminal is in the coverage range of the wave beam accessed at the last moment according to the angular distance and the shape and the field angle of the wave beam:
if yes, the beam is still accessed without beam switching;
and if not, determining the beam switching method according to the number of the beams covering the communication terminal.
8. The beam switching method according to claim 7, wherein the step of calculating the angular distance between the communication terminal and the beam center of the beam according to the first relative positional relationship and the second relative positional relationship comprises:
the angular separation is calculated according to the following formula:
wherein d isi(tk) Is at tkThe angular distance of the communication terminal from the beam i.
9. A beam switching apparatus, comprising:
the position relation module is used for respectively determining a first relative position relation between a plurality of beams and a satellite and a second relative position relation between the communication terminal and the satellite when the communication terminal is positioned in the coverage range of the beams;
a relative position relation vector module, configured to calculate, according to the first relative position relation and the second relative position relation, a relative position relation vector between the communication terminal and the plurality of beams, respectively;
a tangential velocity vector module for determining a tangential velocity vector of the communication terminal relative to the satellite;
and the switching module is respectively used for calculating an included angle between the tangential velocity vector and the relative position relation vector and selecting the beam corresponding to the smallest included angle for access.
10. The beam switching apparatus of claim 9, further comprising a determining module configured to:
acquiring the first relative position relation and the second relative position relation at the current moment;
calculating the angular distance between the communication terminal and the wave beam according to the first relative position relation and the second relative position relation; the angular distance is used for describing the relative position relation between the communication terminal and the wave beam;
judging whether the communication terminal is in the coverage range of the wave beam accessed at the last moment according to the angular distance and the shape and the field angle of the wave beam:
if yes, the beam is still accessed without beam switching;
and if not, determining the beam switching method according to the number of the beams covering the communication terminal.
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