The present application claims the benefit of priority to Korean Patent Application No. 10-2023-0098891 filed on Jul. 28, 2023, in the Korean Intellectual Property Office. The aforementioned application is hereby incorporated by reference in its entirety.
The present invention relates to a method, a recording medium, and an apparatus for determining satellite orbital positions and a path for a Low Earth Orbit (LEO) satellite network.
In communications between two base stations spaced very far apart from each other, such as intercontinental communications, wired communications through submarine cables have insufficient resources for meeting future communication demands, and interest in the techniques for improving communication efficiency and performance by arranging low earth orbit satellites between base stations to assist communications between two base stations spaced far apart from each other is growing recently to solve this problem.
As the low earth orbit satellites are located at the altitudes relatively close to the Earth and have a low delay time, there are advantages of enabling fast real-time communication, excellent responsiveness, high data transmission rate, multiple routing, and relatively low launch costs as they are located on low earth orbits.
Meanwhile, it is very important for a low earth orbit satellite network to optimally set the orbits of the satellites taking into account relative positions, orbital altitudes, cycles, and the like of the satellites with respect to the Earth to cover various areas of the Earth as much as possible, and set an optimal path to assist communications between base stations.
Therefore, research on a method of optimizing satellite orbital positions and a path for a low earth orbit satellite network is needed.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method, a recording medium, and an apparatus for optimizing satellite orbital positions and a path for a low earth orbit satellite network.
To accomplish the above object, according to one aspect of the present invention, there is provided a method of determining satellite orbital positions and routing for a Low Earth Orbit (LEO) satellite network located on a first orbit on a transmitting base station side and a second orbit on a receiving base station side, the method comprising the steps of: calculating a communication throughput in each of a link between the transmitting base station and a satellite deployed on the first orbit, a link between satellites deployed on the first and second orbits, and a link between a satellite deployed on the second orbit and the receiving base station, and calculating a communication throughput in an entire link between the transmitting base station and the receiving base station on the basis of the calculated communication throughput in each link; determining satellite orbital position variables and routing variables for maximizing the communication throughput in the entire link; and determining deployment of satellites on the first and second orbits on the basis of the determined satellite orbit position variables and routing variables.
To accomplish the above object, according to another aspect of the present invention, there is provided an apparatus for determining satellite orbital positions and routing for a Low Earth Orbit (LEO) satellite network located on a first orbit on a transmitting base station side and a second orbit on a receiving base station side, the apparatus comprising: a communication throughput calculation unit for calculating a communication throughput in each of a link between the transmitting base station and a satellite deployed on the first orbit, a link between satellites deployed on the first and second orbits, and a link between a satellite deployed on the second orbit and the receiving base station, and calculating a communication throughput in an entire link between the transmitting base station and the receiving base station on the basis of the calculated communication throughput in each link; a variable determination unit for determining satellite orbital position variables and routing variables for maximizing the communication throughput in the entire link; and a satellite deployment determination for determining deployment of satellites on the first and second orbits on the basis of the determined satellite orbit position variables and routing variables.
The detailed description of the present invention is described below with reference to the accompanying drawings, which shows, as an example, specific embodiments in which the present invention may be embodied. These embodiments are described in detail as sufficient as to embody the present invention by those skilled in the art. It should be understood that although the various embodiments of the present invention are different from one another, they are not necessarily mutually exclusive. For example, specific shapes, structures and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the present invention in relation to an embodiment. In addition, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Accordingly, the detailed description described below is not intended to be taken in a limiting sense, and the scope of the present invention is limited, if properly described, only by the appended claims, together with all the scopes equivalent to those claimed in the claims. In the drawings, similar reference numerals refer to identical or similar functions across several aspects.
Components according to the present invention are components defined not by physical classification but by functional classification, and may be defined by the functions performed by each component. Each component may be implemented as hardware or program codes and processing units (or processors) that perform respective functions, and functions of two or more components may be implemented to be included in one component. Therefore, the names given to the components in the following embodiments are not to physically distinguish each component, but to imply a representative function performed by each component, and it should be noted that the technical spirit of the present invention is not limited by the names of the components.
Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.
Referring to
Satellites corresponding to reference numerals 120 and 130 among the satellites 120, 130, 140, and 150 are located on orbit I close to the source BS 110, and satellites corresponding to reference numerals 140 and 150 are located on orbit J close to the destination BS 160.
Coordinate information indicating a position in the plane coordinate system for each of the source BS 110, destination BS 160, and satellites 120, 130, 140, and 150 may be expressed as described below.
Coordinate information of the source BS 110 may be expressed as (xs, ys, Hs), and coordinate information of the destination BS 160 may be expressed as (xD, yD, HD), and here, H represents the altitude in the plane coordinate system, S is an index indicating the source BS, and D is an index indicating the destination BS.
Coordinate information of the satellite located on orbit I and corresponding to reference numeral 120 is (xI, yI,k[n], HI), and coordinate information of the satellite corresponding to reference number 130 is (xI, yI,k+1[n], HI), and here, k is an index indicating the number of satellites, and n is an index indicating a time slot.
Coordinate information of the satellite located on orbit J and corresponding to reference number 140 may be expressed as (xJ, yJ,k[n], HJ), and coordinate information of the satellite corresponding to reference number 150 may be expressed as (xJ, yJ,k+1 [n], HJ).
The source BS 110 may transmit signals to any one of the satellites located on orbit I, and the destination BS 160 may receive the transmission signals of the source BS 110 from any one of the satellites located on orbit J.
In this case, routing that determines satellites that will be connected to the source BS 110 and the destination BS 160 and determining the orbital positions of these satellites are very important in enhancing communication efficiency and performance. Accordingly, an embodiment of the present invention proposes a separate apparatus 200 for optimizing the satellite orbital positions and routing of the illustrated low earth orbit satellite network 100. The apparatus 200 may enhance the communication efficiency and performance of the low earth orbit satellite network 100 by optimizing the satellite orbital positions and routing, and may be implemented, for example, as a server, a desktop personal computer (PC), a laptop PC, a smart phone, a tablet personal computer (PC), a smart watch, or the like.
Referring to
The communication throughput calculation unit 204 calculates a communication throughput in each of a link between the transmitting BS (source BS) and a satellite deployed on a first orbit (orbit I) close to the transmitting BS, a link between a satellite deployed on a second orbit (orbit J) close to the receiving BS (destination BS) and the receiving BS, and a link between the satellites deployed on the first and second orbits, and calculates a communication throughput in the entire link between the transmitting BS and the receiving BS on the basis of the communication throughput in each link.
The variable determination unit 206 determines satellite orbital position variables and routing variables so that the calculated communication throughput in the entire link may be maximized. That is, the variable determination unit 206 determines optimal routing variables having the maximum value of the communication throughput in the entire link for each time slot, and determines optimal satellite orbital position variables having the maximum value of the communication throughput in the entire link to which the determined optimal routing variables are applied.
The satellite deployment determination unit 208 determines deployment of satellites on the first and second orbits on the basis of the determined satellite orbital position variables and routing variables.
Referring to
Assuming a LOS channel situation as described above in
Here, W denotes the bandwidth of a channel, d[n] denotes the distance from one node (e.g., a BS/satellite) to another node (e.g., another BS/satellite) in an n-th time slot, and γ0 denotes the reference signal to noise ratio (SNR) at a distance of 1 meter.
As a plurality of satellites is located on an orbit and a plurality of links may be created therefrom, the source BS 110 and the destination BS 160 should determine a link through routing, and a routing variable is required to determine a link. The conditions for the routing variable are as shown in Equation 2.
Here, aS
Rij[n] denotes the communication throughput in the link between the satellite 120 and the satellite 140, and RjD[n] denotes the communication throughput in the link between the satellite 140 and the destination BS 160.
At this point, the satellites 120 and 140 transmit signals in a Decode and Forward (DF) relay method. In this case, the communication throughput in the entire link between the source BS 110 and the destination BS 160 in the n-th time slot may be calculated using Equation 4.
Here, aSi[n] denotes the connection relation between the source BS 110 and the satellite 120, ajD[n] denotes the connection relation between the satellite 140 and the destination BS 160, RSi[n] denotes the communication throughput in the link between the source BS 110 and the satellite 120, Rij[n] denotes the communication throughput in the link between the satellite 120 and the satellite 140, and RjD[n] denotes the communication throughput in the link between the satellite 140 and the destination BS 160.
Since satellites have periodicity and are unable to move once deployed on an orbit due to the nature of the satellites, the communication throughput over a sufficiently long period of time should be maximized. Since that the present invention ultimately seeks to obtain is routing that shows satellite orbital positions and a communication path that can maximize the communication throughput, the communication throughput in the entire link between the source BS 110 and the destination BS 160 during the entire time slot may be expressed as shown in Equation 5.
That is, the communication throughput in the entire link between the source BS 110 and the destination BS 160 may be calculated as the sum of the communication throughputs between the source BS 110 and the destination BS 160 during all N time slots in a time frame.
The overall problem including the communication throughput calculation equation and constraints of the entire link of Equation 5 may be expressed as shown in Equation 6.
Here, x1 and xJ denote satellite orbital position variables that indicate the positions of satellites on orbits I and J, respectively, ASI denotes a routing variable that shows the connection relation between the source BS and a satellite located on orbit I, and AJD denotes a routing variable that shows the connection relation between a satellite located on orbit J and the destination BS.
Meanwhile, since it is a very difficult problem to simultaneously obtain the maximum value for all variables, i.e., for the satellite orbital position variable and the routing variable in Equation 6, in an embodiment of the present invention, the optimization problem of the satellite orbital position variables x1 and xJ and the optimization problem of the routing variables aSI[n] and aJD[n] are separately progressed step by step as shown in Equation 7 and Equation 8.
That is, a routing variable having the maximum value of the communication throughput in the entire link is determined for each time slot through Equation 7, and satellite orbital position variables having the maximum value of the communication throughput in the entire link to which the determined routing variables are applied is determined through Equation 8. In Equation 8, function g is obtained through Equation 7.
The objective function of Equation 8 is a non-convex function, and the problem of the non-convex function can be solved through a Successive Convex Approximation (SCA) technique. The function g may be expressed as shown in Equation 9.
Here, since g1,n, g2,n, and g3,n represent RSi[n], Rij[n], and RjD[n], each having a determined routing variable, and RSD[n]=min(RSi[n],Rij[n],RjD[n]), it can be expressed as gn(xI,xJ)=min(g1,n,g2,n,g3,n)
At this point, since the function g is a non-convex function for the satellite orbital position variable, this problem can be solved using a surrogate function. The surrogate function uses a Taylor function as shown in Equations 10 to 12.
Here, h1,n, h2,n, and h3,n are surrogate functions of g1,n, h2,n, and g3,n, respectively, and k denotes the k-th iteration of the SCA technique.
The entire function may be expressed as shown in Equation 13 and Equation 14.
Since the maximum value of the entire function shown in Equation 13 and Equation 14 should be obtained, the solution is obtained through partial differentiation as shown in Equation 15 and Equation 16.
Here, {circumflex over (x)}I(k) and {circumflex over (x)}J(k) are coordinates of the optimal point of function h, and may be expressed as shown in Equation 17 and Equation 18.
When F2−DE=0 in Equation 18, a problem that the denominator becomes 0 occurs, so that in this case, initial values {circumflex over (x)}I(0) and {circumflex over (x)}J(0) are newly defined, and the same process is repeated. According to the SCA technique, each iteration is progressed as shown in Equation 19.
Referring to
At step 404, the optimizer calculates a communication throughput in all links between the transmitting BS and the receiving BS on the basis of the communication throughput in each link calculated at step 402.
At step 406, the optimizer determines satellite orbital position variables and routing variables so that the communication throughput in the entire link calculated at step 404 is maximized. That is, for each time slot, the optimizer determines optimal routing variables having the maximum communication throughput in the entire link, and determines optimal satellite orbital position variables having the maximum communication throughput in the entire link to which the determined optimal routing variables are applied.
At step 408, the optimizer determines deployment of satellites on the first and second orbits on the basis of the satellite orbital position variables and the routing variables determined at step 406. In at least one embodiment, the optimizer controls deployment of satellites on the first and second orbits on the basis of the satellite orbital position variables and the routing variables determined at step 406. For example, the optimizer sends, through a communication circuitry of the optimizer, instructions to corresponding satellites on the first and second orbits, or to the satellites' respective controlling systems, to control the satellites to be deployed in accordance with the determined satellite orbital position variables. In at least one embodiment, the optimizer controls communication between the transmitting BS and the receiving BS to occur over satellites deployed in accordance with the determined satellite orbital position variables and the determined routing variables. The described operations are examples. Other operations within the scopes of various embodiments.
Referring to
As can be confirmed through
The method of determining satellite orbital positions and routing of the present invention as described above may be implemented in the form of program instructions that can be executed through various computer components and recorded in a non-transitory computer-readable recording medium. The computer-readable recording medium may store program instructions, data files, data structures, and the like alone or in combination.
The program instructions recorded in the computer-readable recording medium may be specially designed and configured for the present invention or may be known to and used by those skilled in the field of computer software.
Examples of the non-transitory computer-readable recording medium include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like.
Examples of the program instructions include high-level language codes that can be executed by a computer using an interpreter or the like, as well as machine language codes such as those produced by a compiler. The hardware devices described above may be configured to operate as one or more software modules to perform the processes according to the present invention, and vice versa.
Although various embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and of course, various modified embodiments are possible by those skilled in the art without departing from the gist of the present invention claimed in the claims, and these modified embodiments should not be individually understood from the technical spirit or prospect of the present invention.
According to one aspect of the present invention described above, as a method, a recording medium, and an apparatus for optimizing satellite orbital positions and a path for a low earth orbit satellite network are provided, the communication throughput maximizing problem can be solved, and it may contribute to improving communication quality.
Number | Date | Country | Kind |
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10-2023-0098891 | Jul 2023 | KR | national |