JP4461260B2 - Manhattan Street Network Configuration Method Using Low Orbit Satellites - Google Patents

Description

  The present invention relates to a method for configuring a Manhattan street network using a Low Earth Orbit (LEO) satellite.

Fig. 10 is a diagram showing the types of satellite constellations (arrays). The satellite orbit is viewed from the North Pole on the extension of the Earth's rotation axis. A is the π constellation. It is used in the iridium system known as a satellite communication system that covers the entire earth using a low-orbit satellite group. Specifically, in the iridium system, the orbital plane arrangement that circulates on the earth is divided into six orbital planes at 180 degrees in the longitude direction of the earth, and a plurality of satellites are arranged on the rings constituting each orbital plane. The method of moving around is adopted. Each satellite communicates at a speed of several megabits per second using radio waves. Each satellite communicates with mobile terminals on the earth. In the π constellation method of A, a seam (Seam) in which satellites in adjacent orbits move in the reverse direction every 180 degrees longitude (the satellites in each orbit go south on one side but go north on the other side of the earth). ), And communication between satellites in adjacent orbits is impossible.
B in FIG. 10 shows a 2π constellation, which is a method of dividing the earth's longitude direction of 360 degrees by the number of orbital planes. Each satellite orbit follows an orbit inclination angle, and each satellite orbits its own orbit. Yes. This 2π constellation is adopted in the global star system. In this method, inter-satellite communication with satellites traveling in the same direction on adjacent orbits is possible, and the ground surface can be uniformly covered.
Research on the next-generation low-orbit (next-generation LEO) system that employs this 2π constellation is underway, and the IEICE Transactions B, Vol. J84-B No. 6 pp 963-972 (June 2001). Among them, it is described that the following points are taken into consideration as a condition for selecting a trajectory in the next generation LEO system.
(1) The service area is the surface of the earth excluding the north and south polar regions.
(2) For the Van Allen band, the radiation tolerance of the semiconductor mounted on the satellite is 5 × 10 ⁴ and the satellite altitude is 1200 km.
(3) The satellite altitude shall be two or more visible satellites at an elevation angle of 10 degrees or more.
(4) The minimum elevation angle shall be 20 degrees or more in the range from 70 degrees south latitude to 70 degrees north latitude.
(5) The relationship between inter-satellite communications and orbits uses a combination of slopeless orbits without seams and 2π constellations to simplify the control of inter-satellite communications networks, and considers the distance between satellite communications with 2π constellations. The communication distance between satellites shall be 5000 km or less.
Considering these various conditions, the trajectory parameters proposed as the next generation LEO system of the above document are set as follows.
Total number of satellites 120 Number of orbital planes 10 Number of satellites in the same orbital plane 12 Orbital altitude of satellite 1,200Km
Orbit eccentricity 0: Circular orbit Satellite orbit period 109.4 min Orbital inclination angle of each orbital surface 55 degrees Ascension intersection difference of adjacent orbital plane 36 degrees Center angle phase difference of satellites on adjacent orbital plane 3 degrees The relative directions of the interplanetary satellites are expressed as follows: the Yaw axis direction of the satellite is directly below the elevation angle, and the Roll axis direction is the azimuth angle direction of 0 degrees. The azimuth angle is −55 to +55 degrees and the elevation angle is −11 to −19 degrees. It becomes. The variation range of the relative distance is maintained at 3,000 to 5,000 km. Therefore, a control range of about 120 degrees in the azimuth direction and 10 degrees in the elevation direction (angle at which the satellite is viewed from the ground) can be realized.
FIG. 11 shows the concept of the proposed next generation LEO system. In this system, a network using a plurality of low-orbit satellites is constructed, and it can be connected to various portable terminals (cell phones, personal computers with communication functions, video cameras with communication functions, etc.) between any points on the earth. Provide multimedia communication via satellite network. In the figure, 10a1, 10a2, 10b1, 10b2,... Represent satellites, 11a1, 11a2,..., 11b1, 11b2,..., 11ab1, 11ab2,. , 12 is a spot beam (Spot Beam) for communicating with each satellite and a terminal on the earth, and 13 is a terminal on the earth. Examples of the terminal include a mobile phone, a personal computer, a video camera, and a PDA.
In FIG. 11, a plurality of satellites 10a1 and 10a2 constitute a satellite in the orbital plane of orbit a, and satellites 10b1 to 10b3 constitute a satellite in the orbital plane of another adjacent orbital b. Orbits the earth along its orbit. Each satellite forms a bidirectional communication link by an inter-satellite optical link in the same orbital plane and an interorbital optical link with a satellite in an adjacent orbit, and 11a1, 11a2, 11a3, and 11a4 are in-orbit links in orbit a. , 11b1, 11b2, and 11b3 constitute in-orbit links of the orbit b, and 11ab1 and 11ab2 are links between the orbital surfaces. The terminal 13 on the earth communicates with a satellite included in a range of a certain elevation angle, and a satellite that can communicate with a partner terminal in another region and a satellite that relays the satellite. Bidirectional communication is performed via a communication link.
FIG. 12 shows a schematic block configuration of the proposed satellite. Optical antennas 20a to 20d for performing optical communication between satellites are provided and used for optical ISL connection. That is, two of these optical antennas are for communication with two adjacent satellites in the orbit, and the other two optical antennas are for communication with two satellites belonging to two adjacent orbits. The distance between this optical antenna and the adjacent satellite is about 3000 km to 5000 km, and for this reason, the development of precise directivity control technology and optical modulation / demodulation technology for the optical antenna is being carried out. As a specific example, an active universal joint (AUJ) type optical antenna improved from the front single plane mirror drive system has been created. In the AUJ system, the Az axis and α are used for angle control in the EI direction of the front mirror. Control the rotation axis tilted. In optical communication between satellites, transmission of about 10 Gbps is possible.
The optical modem 21 modulates the transmitted light and demodulates the received light. The cell-based switch 22 is a cell corresponding to various protocols such as ATM (Asynchronous Transfer Mode), IP (Internet Protocol), MPLS (Multiprotocol Label Switching). This is a mechanism for switching a base signal between a signal corresponding to an optical antenna of an optical ISL between satellites and a user link signal. The multiport modem 23 is a mechanism for performing mutual conversion between the signal format corresponding to the user link and the signal format of the intersatellite link, and the digital beam forming circuit 24 multi-signals the signal from the antenna radio frequency (RF) circuit 25. This is a circuit for converting to a port modem 23 and converting a signal from the multi-port modem 23 into a signal for an individual user. The antenna / high frequency circuit 25 transmits a fixed ground scanning spot beam from the antenna to a terminal at an individual point on the ground and receives a signal from the antenna that has received the high frequency signal transmitted from the terminal. FIG. 13 shows a satellite arrangement and inter-satellite communication connection configuration based on orbit parameters proposed as a next generation low orbit system. 13A shows the configuration of intra-plane communication (Intra-Plane ISL) in the same orbital plane, and B in FIG. 13 shows satellite arrangement and inter-orbit inter-satellite communication (Inter-Plane ISL). The structure of is shown.
In both figures, the black dot represents the satellite, the vertical axis represents the latitude (indicated by Latitude (deg.)), And in this example, the satellite is orbiting in the range from north latitude 60 to south latitude 60 (-60). , The horizontal axis represents longitude (displayed in Longitude (deg.)), And numbers corresponding to each longitude of 0, 60, 90,..., 330, 0 (expressed in 0 to 360 degrees instead of east longitude and west longitude) It is shown.
In the case of FIG. 13A, one satellite orbital plane is composed of 12 satellites on the orbit with a constant orbit inclination angle, and 10 such satellite orbital planes are arranged at regular intervals on the longitude. Has been. Twelve satellites on each satellite orbital plane are sequentially connected by links for two-way communication between adjacent satellites as shown by dotted lines to form a ring network. B of FIG. 13 shows a communication configuration between adjacent interorbit satellites, and each satellite has a certain phase difference with the satellites of both adjacent satellite orbital planes (the inter-orbital satellite center angle phase difference is 3 degrees: 360). Degrees / 120 (based on the total number of satellites) = 3 degrees), when satellites in adjacent orbital planes are sequentially connected, a spiral connection is formed, and all satellites (12 × 10 = 120) are routed through the earth several times. ) Is connected in a ring shape.
Communication between satellites in the same orbital plane is formed by the network shown in FIG. 13A, and communication between adjacent orbital satellites is formed by the network shown in FIG. 13B. Such communication networks are called Manhattan Street Networks. FIG. 14 shows the inter-satellite distance constituting the constellation. In the satellite constellation, it is necessary to appropriately select the phase angle parameter F of the satellite in order to avoid satellite collision, and the number of orbital planes (P = 10) and the number of in-orbit plane satellites (S = 12) When the phase difference between the orbital planes is set to 0, there is a possibility that the satellites of the orbital planes intersecting on the equator collide. FIG. 14A shows the relative distance fluctuation with other satellites in the satellite orbit. At orbital phases of 0 and 180 degrees, the satellite approaches an orbital plane whose ascending intersection longitude is 180 degrees different. Further, as shown here, other satellites are also approached at orbital phases 30, 150, 210 and 330 degrees, but this approach can be avoided by changing the orbit inclination angle.
Further, B in FIG. 14 shows the inter-satellite distance constituting the constellation. This indicates the inter-satellite distance when F = 1. In this case, 120 satellites do not approach several hundred km or less and are safe.
On the other hand, in the satellite communication system technology, it includes a large number of low-orbit satellites that have a dynamic satellite array and move on the orbital plane, and each satellite independently independently identifies the position of adjacent satellites and switches them. In addition, each satellite has a function to control the amount of communication independently without receiving control from the ground, and each satellite can be carried via a gateway to portable users, mobile users, fixed radio terminals, and users of public telephone networks that can be switched. A technique that can carry direct calls, provides direct communication between arranged satellites, and provides individual communication using a lightweight, portable telephone is disclosed in WO 93/09613. .

According to the Manhattan Street communication network using conventional orbiting satellites shown in FIGS. 13A and 13B, when communicating between users located in areas (regions) distributed north and south, as shown in FIG. Signals from terrestrial user terminals belonging to one of the areas are communicated with satellites above the area, and the satellites gradually move upward (north direction) or downward (south direction) into a helical satellite orbital plane. It is necessary to communicate with one of the other satellite orbital planes that communicates with the other user terminal belonging to the other area of the north-south area via inter-orbital plane communication. There is a problem that the control of selection becomes complicated, and there is also a problem that transmission delay is large because the transmission distance becomes long.
The present invention solves the above-mentioned problem, and can easily form a communication link between users located in areas distributed in the north and south, and can construct a Manhattan street network using a low-orbit satellite that can reduce delay time. The purpose is to provide.
The present invention uses P satellite orbits using parameters that meet the conditions for preventing the approach and collision of the number of satellite orbit planes (P), the number of satellites in the orbit (S), and the phase difference coefficient (F). The surface has the same orbit inclination angle, the angle varies according to the maximum latitude of the service area, ranges from 45 degrees to 70 degrees, the elevation angle also has numerical values to avoid approach and collision, When the satellites in each orbital plane are numbered 1, 2,... In order from the south end to the north end, the n-th satellite on the orbital plane is connected to the n− on the orbital plane adjacent to the east side. A ring connection is formed by connecting to the first satellite in order, and a ring connection is made in order for each satellite constituting each of the orbital planes. The number of ring connections that are connected in a square shape is the number of satellite orbits. The principle to be formed.
FIG. 1 is a structural example of satellite connection between satellite orbital surfaces according to the present invention. In the figure, the vertical axis represents the latitude of the earth, the horizontal axis represents the longitude of the earth, the black circle represents the satellite, the solid line connecting the black circles represents the bidirectional line connection between the satellite orbital planes, 3-1 to 3- 11 is a plurality of 8-shaped network formed by satellite connection between the satellite orbital planes according to the present invention, F-11, G-10, H-9,..., D-2, E-1 are 8 It represents the satellites that make up the letter-shaped network 3-11.
The configuration example of FIG. 1 is a case where the number of satellite orbit planes P = 11, the number of satellites in the orbit plane S = 11, and the phase difference coefficient F = 0. Each of the P (11) satellites is a low-orbit orbit type, and a ring-connected network is formed in the orbit that sequentially connects a plurality of (S = 11) satellites in the same orbital plane (first). 1), a network for connecting the satellite orbit planes as shown in FIG. 1 is formed at the same time, and FIG. 2 shows the logical structure of the line connection between the satellite orbit planes.
The line connection between the satellite orbit planes is that each satellite (S = 11) on the P (11) satellite orbits has an orbit adjacent to the right side (orbit adjacent to the east side) with respect to its position (n). Connect to the satellite at the position (n-1) one step lower, connect to the position one step lower on the satellite orbit adjacent to the right side from that satellite, make the same connections in the following order, and finally the same Returning to the original satellite, an 8-shaped ring connection network is formed (S) for the number of satellites in one orbital plane. In FIG. 1, A, B, C,..., J, K are assigned to 11 satellite orbit planes (see FIG. 2), and at a certain point in time for the satellites in each satellite orbit plane. In the same orbit, the number 1 is assigned to the satellite located at one end in the north-south direction, and the number 11 is assigned to the satellite located at the other end (see FIG. 2) 1 to 11), an 8-shaped network of satellite connections between the satellite orbital planes.
An 8-shaped network 3-11 in FIG. 1 is connected to the satellite G-10 (the 10th satellite on the satellite orbital plane G) from the satellite F-11 (the 11th satellite on the satellite orbital plane F). Satellite H-9, Satellite I-8, Satellite J-7, Satellite K-6, Satellite A-5, Satellite B-4, Satellite C-3, Satellite D-2, Satellite E-1 , And a ring connection is formed from the satellite E-1 to the satellite F-11. The other 8-shaped networks 3-1 to 3-10 are formed based on the same principle.
In this way, communication between terminals in the north and south areas can be easily configured by the 8-shaped ring connection.
Each satellite has two-way communication with adjacent satellites in the same orbit, two-way communication with satellites in adjacent orbits, and two-way communication with terminals on the ground. In addition, a switching function and a modulation / demodulation function of a signal to the satellite and a signal from the terminal to the terminal are provided.
FIG. 2 shows a logical structure of an intersatellite communication line in the configuration example of FIG. In the figure, A to K are 11 satellite orbits, and 11 satellites in each orbit are represented by numerals 1 to 11 in. In FIG. 2, only the ring connection between the satellites for the 11th satellite in the uppermost stage (north end) of the satellite orbit F is indicated by a thick line, and the inter-orbit connections for other satellites and the ring connections (vertical) in each satellite orbit. Direction) is also shown. In FIG. 2, each satellite orbit is drawn in the vertical direction. Actually, however, each satellite orbit is inclined by an orbit inclination angle as shown in FIG. 11 (conventional example). As shown in FIG. 1 above, the ring connecting the two has an 8-character shape connecting the north and south.

FIG. 1 is a diagram showing a configuration example of satellite connection between satellite orbit planes according to the present invention.
FIG. 2 is a diagram showing a logical structure of an intersatellite communication line in the configuration example of FIG.
FIG. 3 is a diagram showing an arrangement when the inter-orbital inter-satellite connection is n → n−1.
FIG. 4 is a diagram showing a connection configuration between raceways when P> S.
FIG. 5 is a diagram showing a connection configuration between raceway surfaces in the case of P <S.
FIG. 6 is a diagram showing an example of a combination of P, S, and F that forms a Manhattan street network.
FIG. 7 is a diagram showing an example of combinations of parameters that form a Manhattan street network structure without satellite approach and collision.
FIG. 8 is a diagram showing an inter-orbit-plane inter-satellite connection configuration (P = 11, S = 12, F = −1).
FIG. 9 is a diagram showing an inter-orbit-plane inter-satellite connection configuration (P = 9, S = 11, F = −2).
FIG. 10 is a diagram showing the types of satellite constellations.
FIG. 11 is a diagram showing the concept of the proposed next-generation LEO system.
FIG. 12 is a schematic block diagram of the proposed satellite.
FIG. 13 is a diagram showing a satellite arrangement and inter-satellite communication connection configuration based on orbit parameters proposed as a next generation low orbit system.
FIG. 14 is a diagram showing distances between satellites constituting the constellation.

FIG. 3 shows the arrangement when the interplanetary satellite connections are n → n−1. In the figure, P is the number of orbital planes, S is the number of satellites in the orbital plane, and F is a phase difference coefficient (an integer with 360 degrees / (P × S) as a unit). , Satellites connected between the orbital planes are arranged in the lateral direction, and the connection path between the orbital planes is as shown in FIG. In the figure, j represents the orbital plane number which is the number of 0,..., P-1, and k represents the orbital plane number which is the number of 0,. The arrangement in FIG. 3 is for the condition −P / 2 <F <P / 2.
When the connection arrangement in the oblique direction is rewritten in the horizontal direction with respect to FIG. 3, the arrangement is as shown in FIG. 4 and FIG.
FIG. 4 shows the connection configuration between the raceways when P> S. (0, S-1) to (0, 0), (1, S-2) to (1, S-1), ..., (P-1, 2S-) arranged in the vertical direction in FIG. P) to (P-1, 2S-P + 1) represent S satellites in the satellite orbital plane constituting each of the P satellite orbital planes assigned numbers 1, 2,. The whole is composed of P × S satellites. The satellite of the orbital plane P in FIG. 4 is connected to the satellite of the orbital plane 1 corresponding to the satellite number shown at the right end. On the other hand, the satellite of the orbital plane 1 is connected to the satellite of the orbital plane P corresponding to the satellite number shown at the left end.
FIG. 5 shows the connection configuration between the raceways when P <S. In this case as well, as in FIG. 4, the rightmost satellites in the figure are connected to the same numbers of the satellites arranged in the leftmost vertical direction.
In FIGS. 4 and 5, the conditions for the Manhattan Street Network structure using the parameters of P for the number of satellite orbits, S for the number of satellites in the orbital plane, and F for the phase difference coefficient are as follows. Since they are connected to the same row, paying attention to the (k + 1) row in FIG. 4 and FIG.
(0, mod (S−P + k + F, S)) = k
Therefore, under the condition of S−P + k + F <S,
Since S−P + k + F = k, S−P + F = 0.
Since it is clear that a Manhattan street structure is obtained when S = P, as shown in FIG. 2, the above formula can be applied to arbitrary P and S.
FIG. 6 shows an example of a combination of P, S, and F that forms a Manhattan Street network.
Even in the combination of FIG. 6, there are conditions for the satellites to approach and collide depending on the combination of parameters.
Conditions for approaching a satellite on another orbital plane at the point where it intersects the satellite equator are as shown in (1) and (2).
(1) When the orbital plane number P is an odd number, there is no orbital plane with an ascending intersection longitude difference of 180 degrees, so there is no satellite approach at an orbital position of 180 degrees.
(2) When the number of track planes P is an even number, there are track planes whose ascending intersection longitude is 180 degrees different.
a. When the number of in-plane satellites S is an odd number and F is an odd number, the approach condition is met.
b. When the number S of in-orbit satellites is an even number and F is an even number, the approach condition is met.
That is, in FIG. 6, when P is an even number, there is a possibility of a satellite collision in all F, so this parameter cannot be used. As a result, FIG. 7 shows an example of a combination of parameters for a Manhattan street network structure without satellite approach and collision.
As shown in FIG. 7, since the number of orbital planes P does not hold even under the condition of an even number, the number of satellite orbital planes P is odd (7, 9, 11, 13) in the Manhattan street network structure. For each number (6 to 13) of the number S of satellites, collision can be avoided by using each value shown in the figure as the value of F.
The configuration example shown in FIG. 1 corresponds to the case of P = 11, S = 11, and F = 0.
FIG. 8 shows the inter-orbit-plane inter-satellite connection configuration (P = 11, S = 12, F = −1), and the orbit inclination angle I = 57.9 degrees. FIG. 8A shows the case of connection between satellites in the same orbital plane, and 11 ring connections having an orbit inclination angle are formed. FIG. 8B shows the inter-satellite connection (n → n−1) between adjacent orbital planes, where n is the satellite number in each satellite orbital plane. Twelve character-shaped ring connections are arranged in the longitude direction. In other words, a two-way Manhattan Street Network structure is formed together with a ring connecting satellites in the same orbital plane.
FIG. 9 shows the inter-orbit-plane inter-satellite connection configuration (P = 9, S = 11, F = −2), and the orbit inclination angle 1 = 54.9 degrees. FIG. 9A shows inter-satellite connections in the same orbital plane, and ring connections in nine orbital planes are formed. B in FIG. 9 is a connection configuration between adjacent orbital planes, and has a structure in which eleven 8-shaped ring connections composed of nine satellites in the latitude direction are arranged in the longitude direction. The connection between satellites in the same orbit shown in A and the connection between satellites between adjacent orbital planes shown in B (n → n-1 connection) are shown.
Manhattan street network structure by using an 8-shaped ring connection between adjacent orbital planes according to the present invention shown in FIG. 1, FIG. 8 and FIG. 9 in combination with the ring connection in each orbital plane. Is realized. Specifically, each satellite has a bidirectional communication link formed by an optical link with an adjacent satellite in the same orbital plane and two satellites forming the above-mentioned 8-shaped ring on both adjacent adjacent orbital planes. Communication and communication connection with a terminal on the ground.

  According to the present invention, communication between the north and south areas included in the same longitude range on the earth can be formed with a short route, the control for connection can be simplified, and the transmission delay time is reduced. It is possible to efficiently provide multimedia between the north and south areas of multimedia such as voice, image, data, etc. of portable terminals.

Claims (3)

A method for configuring the Manhattan Street Network using low-orbit satellites,
A satellite orbital plane in which multiple (S) satellites orbiting the earth are sequentially arranged in a ring at regular intervals, with a predetermined orbit inclination angle that does not cause a collision between the satellites, and at a constant interval in the longitude direction Place multiple (P) pieces by placing
Each satellite in the satellite orbital plane is arranged with a phase difference (F: an integer in units of (P × S)) with respect to each satellite in the preceding adjacent satellite orbital plane,
Each satellite constitutes a ring network in which adjacent satellites composing the same satellite orbital plane are sequentially connected by an optical link that communicates in both directions, and each satellite has a satellite orbital plane adjacent to the east side. In the connection between the orbital planes, an 8-shaped ring-shaped connection is established by connecting with an optical link that bidirectionally communicates with a satellite with a satellite number (n-1) that is one less than the satellite number (n) in the own satellite orbital plane. S network is formed,
A Manhattan street network configuration method using low-orbit satellites, wherein a network in each satellite orbital plane and a network between each satellite orbital plane constitute a Manhattan street network. In the description of claim 1,
In order to avoid approaching and colliding with satellites, the number of satellite orbital planes (P) and the number of satellites in the orbital plane (S)
P = 2n + 1 (n is a natural number)
S−P + F = 0
A method for constructing a Manhattan street network using low-orbit satellites, wherein a phase difference coefficient (F) satisfying the following condition is used. In the description of claim 1,
A method for constructing a Manhattan Street Network using low-orbit satellites, wherein the orbit inclination angle is in a range of 45 degrees to 70 degrees.

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