Satellite constellation communication system and method

Abstract

A satellite constellation communication system comprising: a first layer of satellites placed in very low Earth orbit (VLEO), a second layer of satellites placed in medium Earth orbit (MEO), one or more ground stations designed (i) to receive information streams from one or more satellites of the first or second layer originating from a user terminal or (ii) to transmit information streams via one or more satellites of the first or second layer to a user terminal, and a traffic management center for said system, arranged to route said information streams primarily via one or more satellites of the first layer (VLEO), and, in the absence of a communication link with the first layer (VLEO), to reroute said information streams via one or more satellites of the second layer (MEO). See Figure 1

Description

Title of the invention: System and method for communication by satellite constellation FIELD OF THE INVENTION

[0001] The present invention relates to a communication system using a satellite constellation. It also relates to a communication method implemented in this system. The field of the invention is that of satellite constellations intended to provide global coverage for telecommunications. STATE OF THE ART

[0002] Satellite constellations have been developed over the past several years, with the aim of offering telecommunications services anywhere in the world.

[0003] We also know of initiatives involving certain combinations of satellites in geostationary Earth orbit (GEO), in medium Earth orbit (MEO), in low Earth orbit (LEO), and / or in very low Earth orbit (VLEO), typically less than 400 km, to meet high-speed telecommunications needs.

[0004] Document US 11,290,178 B2 discloses a method and system for using low Earth orbit satellites for latency reduction purposes, implementing a first channel in low Earth orbit (LEO) and a second channel in geosynchronous equatorial orbit (GEO) and including determining which channel to choose based on the type of traffic involved in a data session.

[0005] Document US 11,362,732 B2 discloses a satellite system and method for communication applications, with global coverage, using two constellations in different LEO orbits, with inter-satellite links between the satellites in each constellation, and inter-satellite links between the constellations. The first constellation is deployed in a LEO polar region with a preferred inclination of 99.5 degrees and a preferred altitude of 1000 km. The second constellation is deployed in an inclined LEO orbit with a preferred inclination of 37.4 degrees and a preferred altitude of 1250 km.

[0006] There are projects for VLEO telecommunications constellations for high-speed telecommunications services. The deployment of a VLEO constellation brings multiple advantages in terms of: - better latency times inherent to shorter propagation distances, - better flow rates inherent in more favorable link budgets, - environmental sustainability thanks to the residual density of the atmosphere allowing rapid re-entry into the atmosphere of satellites at the end of their life (reducing the risk of generating orbital debris), the absence of risks of collision with inhabited stations, and less light pollution on optical astronomy.

[0007] On the other hand, the deployment of a VLEO constellation also has disadvantages linked to the very low deployment altitude.

[0008] On the one hand, it requires, relative to constellations deployed at higher altitudes, a greater number of satellites to enable continuous coverage necessary for high-speed telecommunications services as well as to make it possible at any point to establish links between the satellites and the user terminals with elevation angles greater than certain desirable minima (eg 40 degrees) in the event of masking.

[0009] On the other hand, the coverage area (i.e. surface of the Earth visible by the satellite) of VLEO satellites being more restricted, they have less flexibility in the spatial allocation of their spectrum and power resources; consequently they are more subject to having to face peaks in demand at certain times of the day from visible user terminals.

[0010] The aim of the present invention is to overcome these limitations and resolve these drawbacks by proposing a new concept of satellite system providing a high-speed service by a constellation of high-performance and environmentally sustainable VLEO satellites, while being more efficient and resilient than current systems. Presentation of the invention

[0011] This objective is achieved with a communication system by satellite constellation, comprising: - a first layer of satellites placed in a very low Earth orbit (VLEO), - a second layer of satellites placed in a medium Earth orbit (MEO), - one or more ground stations intended (i) to receive information streams from one or more satellites of the first or second layers from a user terminal or (ii) to transmit information streams via one or more satellites of the first or second layers to a user terminal, and - a traffic management center for said system, arranged to route said information flows as a priority via one or more satellites of the first layer (VLEO), and to, in the absence of a communication link with the first layer (VLEO), reroute said information flows via one or several second-layer satellites (MEO).

[0012] With the communication system according to the invention, the combination of the MEO layer, consisting of a limited number of satellites, - typically a few dozen satellites -, with the VLEO layer, consisting of a large number of satellites, - typically several hundred to several thousand satellites, - makes it possible to provide a high-speed service offering the advantages of a constellation deployed in VLEO (better latency times, better throughputs, environmental sustainability) by solving the following technical problems, whatever the latitudes between 0 degrees and ± 90 degrees on which the VLEO layer is deployed:

[0013] (i) make it possible at any point to establish telecommunications links between satellites and user terminals with elevation angles above certain desirable minima (eg 40 degrees) while limiting the number of satellites in the VLEO layer (eg by densifying the orbital planes of the VLEO layer for elevation angles of only 25 degrees), by rerouting to the MEO layer if necessary part of the traffic whose telecommunications links cannot be established due to masking due to elevation angles (eg between 25 degrees and 40 degrees),

[0014] (ii) avoid dimensioning all the subsystems (e.g. on-board computers, inter-satellite links, solar panels, batteries) of all the satellites of the VLEO layer according to the traffic peak by rerouting to the MEO layer if necessary a part of the traffic not sensitive to latency (e.g. video streaming) during traffic peaks and risks of congestion of the VLEO satellites,

[0015] (iii) enable more quickly continuous coverage necessary to provide broadband telecommunications services despite a partial deployment of the VLEO layer orbital plans (e.g. only covering a user terminal 95% of the time) by rerouting to the MEO layer part of the traffic when the telecommunications links cannot be established at the time when the user terminal is located outside the coverage areas of the VLEO satellites,

[0016] (iv) enabling VLEO layer redundancy by rerouting some traffic to the MEO layer when telecommunications links cannot be established in the event of failure of one or more VLEO layer satellites.

[0017] Thus, in the communication system according to the invention, the traffic management center can further be arranged to reroute an information flow to a satellite of the second MEO layer, in response to the impossibility of establishing a telecommunications link due to masking due to an elevation angle of said satellite of the first VLEO layer.

[0018] It is also advantageous to provide that the traffic management center is further arranged to reroute a flow of information not sensitive to latency to a satellite of the second MEO layer, in response to the detection of a peak in traffic demand and congestion risks on the satellites of the first VLEO layer.

[0019] The traffic management center can also be arranged to reroute an information flow to a satellite of the second MEO layer, in response to an inability to establish a communication link to a visible satellite of the first VLEO layer, or to reroute an information flow to a satellite of the second layer (MEO) in response to a failure detection in the first layer of satellites (VLEO).

[0020] According to another aspect of the invention, a communication method is proposed, implemented in a communication system by satellite constellation according to the invention, comprising the following steps: - route information flows from or to one or more ground stations or user terminals, via one or more satellites within a first layer of satellites placed in a very low Earth orbit (VLEO), and - in the absence of a communication link with said first layer (VLEO), reroute said information flows via one or more satellites within a second layer of satellites placed in a medium Earth orbit (MEO).

[0021] The communication method according to the invention may further advantageously comprise a step for rerouting to the second layer (MEO) information flows which were initially to be routed to the first layer (VLEO) but whose telecommunications links cannot be established due to the elevation angles, or being insensitive to latency during traffic peaks and risks of congestion of the VLEO satellites, or not being able to be established when a user terminal is located outside the coverage areas of the VLEO satellites (e.g. in the event of partial deployment of the satellites of the VLEO layer), or in the event of failure of a satellite of the VLEO layer.

[0022] The user terminals concerned by the system and method according to the invention may be static or in motion, in particular within land vehicles (cars, trucks, trains), aircraft or boats. DESCRIPTION OF FIGURES

[0023] - [Fig.l] [Fig.l] schematically illustrates a satellite telecommunications system according to the invention; - [Fig.2] [Fig.2] schematically illustrates part of the telecom process communication according to the invention, taking into account the elevation angle of the satellites; - [Fig.3] [Fig.3] schematically illustrates another part of the te-

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[0028] communication according to the invention, dedicated to taking into account latency-sensitive traffic; - [Fig.4] [Fig.4] schematically illustrates yet another part of the process telecommunications system according to the invention, dedicated to rerouting in the event of a lack of visibility; and - [Fig.5] [Fig.5] schematically illustrates yet another part of the telecommunications method according to the invention, dedicated to rerouting in the event of failure. DETAILED DESCRIPTION We will now describe, with reference to [Fig.l], an exemplary embodiment of a satellite communication system 1 according to the invention. This communication system 1 includes: - on a VLEO orbit (for “Very Low Earth Orbit”) Ov located at an altitude of between 250 and 400 km, by way of non-limiting example 375 km, a first layer Cv of several hundred to several thousand small satellites Sv, Svl, Sv2, by way of non-limiting example 1100; - on an MEO orbit (for “Medium Earth Orbit”) Om located at an altitude of between 6000 and 15000 km, by way of non-limiting example 8100 km, a second layer Cm of a few dozen small satellites Sm, by way of non-limiting example 50, - on the surface Gr of the Earth, a set of ground stations Gsl, Gs2 and communicating with data centers (clouds) Dsl, Ds2, - a CC traffic management center intended to control the satellites of both layers of the satellite constellation. As non-limiting examples, the satellites of the first VLEO layer have a mass between 150 and 500 kg. Their aerodynamic profile must be designed to minimize the contact surface and the aerodynamic drag of the satellites. These VLEO satellites are equipped with optical inter-satellite links, an on-board computer for traffic routing and active antennas allowing the pointing of multiple communication beams. The second MEO layer satellites have a mass between 250 and 1000 kg and are equipped with active antennas allowing the pointing of multiple communication beams. UT user terminals - which can be stationary or mobile - equipped with active antennas allowing the pointing of communication beams, are configured to carry out on the one hand Civ communications with satellites of the first layer in VLEO orbit, and on the other hand Clm communications with second layer satellites in MEO orbit.

[0029] The ground stations Gsl, Gs2 are configured to transmit the communication streams (i) received from one or more satellites Sm; Sv, Svl, SV2 of the first or second layers to a user terminal UT or (ii) transmitted via one or more of these satellites from a user terminal UT.

[0030] These user terminals, which can be embedded in mobility systems such as land vehicles (cars, trucks, trains), aircraft or boats, communicate with the two satellite constellations, and communicate with an integrated 5G non-terrestrial core network (NTN: for “Non Terrestrial Network”).

[0031] The second layer of satellites Cm is configured to provide global coverage and a high level of flexibility while the first layer of satellites Cv is configured to provide high communication performance (latency, throughput) and environmental sustainability.

[0032] Optical communication links 011, 012 are provided between two satellites Svl, Sv; Sv, Sv2 which follow each other within the first VLEO layer.

[0033] We will now describe, with reference to Figures 1 to 5, examples of embodiments of specific modules of the satellite constellation telecommunications method according to the invention. Identical references in each of Figures 2 to 5 correspond to identical elements and components.

[0034] With reference to [Fig. 2], a communication flow originating either from a user terminal UTi or from a ground station GSj is routed as a priority via the VLEO layer. In the case where one of the telecommunications links cannot be established due to masking due to the elevation angles being too low, the information flow is rerouted via the second MEO layer.

[0035] With reference to [Fig. 3], a communication flow originating either from a user terminal UTi or from a ground station GSj is routed as a priority via the VLEO layer. In the case where a peak in information flow and risks of congestion of the VLEO satellites are detected, a part of the information flow not sensitive to latency is then rerouted via the second MEO layer, which makes it possible to mitigate the information flow overload on the first VLEO layer.

[0036] With reference to [Fig. 4], a communication flow originating either from a user terminal UTi or from a ground station GSj is routed as a priority via the VLEO layer. In the case where the user terminal UTi is not located in the coverage area of ​​a satellite of the VLEO layer, the information flow is rerouted via the second MEO layer.

[0037] With reference to [Fig.5], a communication flow originating either from a user terminal UTi or from a ground station GSj is routed as a priority via the VLEO layer. In In the event of failure of one or more satellites in the VLEO layer, the information flow is then rerouted via the second MEO layer.

[0038] The CC traffic management center can communicate with each of the satellites of the VLEO and MEO layers of the constellation. It can dynamically configure the routes of communication flows from GSj ground stations or UTi user terminals.

[0039] In another embodiment of the present invention, the traffic management function and routing choices between the MEO and VLEO layers is distributed among the user terminals, the satellites (MEO and VLEO) and the ground stations.

[0040] Of course, the present invention is not limited to the exemplary embodiment which has just been described and many other embodiments or implementations can be envisaged without departing from the scope of the invention.

Claims

Claims

1. Satellite constellation communication system, comprising: - a first layer of satellites placed in an Earth orbit, - a second layer of satellites placed in a medium Earth orbit (MEO), - one or more ground stations designed to (i) receive information flows from one or more satellites of the first or second layers from a user terminal or (ii) transmit information flows via one or more satellites of the first or second layers to a user terminal, and a traffic management center of said system, arranged to route said information flows as a priority via one or more satellites of the first layer, and to, in the absence of a communication link with the first layer, reroute said information flows via one or more satellites of the second layer (MEO),characterized in that the first layer of satellites is placed in a very low Earth orbit of less than 400 km (VLEO) and in that the traffic management center is further arranged to reroute a latency-insensitive information flow to a satellite of the second layer (MEO), in response to a detection of a peak in traffic demand and risks of congestion on the satellites of the first layer (VLEO).,

2. Communication system according to the preceding claim, characterized in that the traffic management center is further arranged to reroute an information flow to a satellite of the second layer (MEO), in response to a detection of an elevation angle of said satellite of the first layer (VLEO) not allowing a communication link to be established.

3. Communication system according to any one of the preceding claims, characterized in that the traffic management center is further arranged to reroute an information flow to a satellite of the second layer (MEO), in response to an inability to establish a link communication to a visible first layer (VLEO) satellite.

4. Communication system according to any one of the preceding claims, characterized in that the traffic management center is further arranged to reroute an information flow to a satellite of the second layer (MEO) in response to a detection of failure in the first layer of satellites (VLEO).

5. A method of communication by satellite constellation, implemented in the communication system according to any one of the preceding claims, comprising the following steps: - routing information flows from or to one or more ground stations or user terminals, via one or more satellites within a first layer of satellites placed in an Earth orbit, and - in the absence of a communication link with said first layer, rerouting said information flows via one or more satellites within a second layer of satellites placed in a medium Earth orbit (MEO), characterized in that the first layer is located in a very low Earth orbit of less than 400 km (VLEO) and in that it further comprises a step for rerouting a latency-insensitive information flow to a satellite of the second layer (MEO),in response to a detection of a peak in traffic demand and congestion risks on the first layer satellites (VLEO).,

6. Communication method according to the preceding claim, characterized in that it further comprises a step for rerouting an information flow to a satellite of the second layer (MEO), in response to a detection of an elevation angle of said satellite of the first layer (VLEO) not allowing a communication link to be established.

7. Communication method according to any one of the three preceding claims, characterized in that it further comprises a step for rerouting an information flow to a satellite of the second layer (MEO), in response to an impossibility of establishing a communication link to a visible satellite of the first layer (VLEO).

8. Communication method according to any one of the four preceding claims, characterized in that it further comprises a step to reroute an information flow to a second layer satellite (MEO) in response to a failure detection in the first layer of satellites (VLEO).

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