NTN based on VLOS separated radio and core / base station network control

Abstract

To provide a communication system and method that relate to control and user plane separation in a non-terrestrial network (NTN) comprising satellites of different orbits.SOLUTION: A system for communication includes: user equipment (UE) 301; a first satellite 303 having a first orbit defined by a first radius; a plurality of second satellites 330_n each having a second orbit defined by a second radius being less than the first radius; and a core network element 302 located on a surface 300 of a planet. The first satellite is adapted to configure a sequence between the core network element and a second satellite of the plurality of second satellites according to a coverage area. The sequence of the second satellites is adapted to provide a user data connection between the UE and the core network element. The first satellite is further adapted to iteratively update the sequence of the second satellites based on a changing coverage area.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates generally to monitoring non-terrestrial networks (NTNs), and more particularly to control and user plane separation in NTNs that include satellites in different orbits. [Background technology]

[0002] background Further evolution of non-terrestrial networks (NTN) in 5G and / or 6G has been announced by many companies. Several vertical industries, including automotive, drone, tracking, and railway industries, require higher throughput for some of their scenarios so that they can be reliably served by NTN. Current NTN network / cell capacities are in the range of a few Mbits on LEO (Low Earth Orbit) with VSAT (Very Small Aperture Terminal). Increasing the throughput concept on VLOS (Very Low Orbit Satellite) is being considered. Summary of the Invention [Problem to be solved by the invention]

[0003] Embodiments of the present invention aim to address anticipated challenges in VLOS satellite constellations, particularly for 3GPP and 6G evolution. [Means for solving the problem]

[0004] A brief summary of the invention According to one or more embodiments of the present invention, a method for communications includes: transmitting, by a first satellite, a setup request from a user equipment (UE) to a terrestrial-based core network element; configuring, by the first satellite, a sequence of second satellites of a plurality of second satellites based on a setup configuration received from the terrestrial-based core network element according to a coverage area of ​​the sequence of second satellites and a location of the UE and the terrestrial-based core network element relative to the coverage area, the sequence of second satellites including a serving satellite for serving the UE; providing, by the sequence of second satellites, a first user data connection between the UE and the terrestrial-based core network element; and iteratively updating, by the first satellite, the sequence of second satellites based on a changing coverage area of ​​the sequence of second satellites. and iteratively updating includes configuring one second satellite of the plurality of second satellites to be included in the sequence if the coverage area of ​​the existing serving satellite no longer includes the UE, and configuring one second satellite of the plurality of second satellites having a coverage area that includes a terrestrial-based core network element to be included in the sequence if a second satellite currently in the sequence does not have a coverage area that includes a terrestrial-based core network element, wherein the first satellite has a first orbit defined by a first radius and each satellite of the plurality of second satellites has a second orbit, each second orbit defined by a second radius, each second radius being smaller than the first radius.

[0005] According to some embodiments, the plurality of second satellites are very low earth orbit (VLEO) satellites.

[0006] According to some embodiments, the first satellite is one of a low earth orbit (LEO) satellite or a geosynchronous equatorial orbit (GEO) satellite.

[0007] According to some embodiments, the method includes maintaining a further user data connection with the UE by a first satellite, and transmitting data via the further user data connection if the first user data connection is lost.

[0008] According to some embodiments, the first user data connection has the functionality of a secondary user plane and the further user data connection has the functionality of a primary user plane.

[0009] According to some embodiments, the method further includes preventing the UE from camping on the second sequence of satellites.

[0010] According to some embodiments, the first satellite is an anchor cell for the UE. According to some embodiments, at least one second satellite of the plurality of second satellites is a non-anchor cell for the UE.

[0011] According to some embodiments, the method includes performing, by the first satellite, non-access stratum signaling (NAS) with the UE.

[0012] According to some embodiments, providing a first user data connection between the UE and a terrestrially located core network element includes communication via inter-satellite links (ISLs) between satellites included in the sequence.

[0013] According to some embodiments, the method includes performing an inter-satellite hybrid automatic repeat request (HARQ) process, the inter-satellite HARQ process including transmitting, by a serving satellite, user data and information related to generating a HARQ redundancy version to a second adjacent satellite in the sequence before the coverage area of ​​the serving satellite no longer includes the UE.

[0014] According to some embodiments, the method includes monitoring, by the UE, a first satellite when the UE is in an idle mode.

[0015] According to some embodiments, at least two of the plurality of second satellites are operated by different mobile network providers (MNOs).

[0016] According to one or more embodiments of the present invention, there is provided a system for communications, comprising: User equipment (UE); a first satellite having a first orbit defined by a first radius; a plurality of second satellites each having a second orbit, each second orbit defined by a second radius, each second radius being smaller than the first radius; Terrestrial-based core network elements and Equipped with The first satellite responds to the setup request from the UE by: sending a setup request to a terrestrial core network element; configuring, based on the setup configuration received from the ground-based core network element, a sequence of second satellites among a plurality of second satellites according to a coverage area of ​​the sequence of second satellites and a location of the UE and the ground-based core network element relative to the coverage area, where the sequence of second satellites includes a serving satellite for serving the UE; and adapted to: A system for communications is provided in which the sequence of second satellites is adapted to provide a first user data connection between a UE and a terrestrial-based core network element, and the first satellite is further adapted to iteratively update the sequence of second satellites based on the changing coverage area of ​​the sequence of second satellites by: configuring one second satellite of the plurality of second satellites to be included in the sequence as a new serving satellite if the coverage area of ​​an existing serving satellite no longer includes the UE; and configuring one second satellite of the plurality of second satellites having a coverage area that includes a terrestrial-based core network element to be included in the sequence if a second satellite currently in the sequence does not have a coverage area that includes the terrestrial-based core network element.

[0017] According to one or more embodiments, there is provided a satellite adapted to perform the role of the first satellite in the above-described method.

[0018] According to one or more embodiments, there is provided a satellite adapted to perform the role of the second satellite in the above-described method.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS Non-limiting examples of embodiments of the present disclosure are described below with reference to the accompanying drawings. Dimensions of features shown in the drawings are chosen for convenience and clarity of presentation and are not necessarily drawn to scale. The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with its objects, features, and advantages, may be understood by reference to the following detailed description in conjunction with the accompanying drawings. The embodiments are illustrated, without limitation, in the drawings in which like reference numerals indicate corresponding, similar, or similar elements. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 illustrates an example of the visibility period of a single LEO satellite orbiting at 600 km. [Figure 2A] 1 illustrates an exemplary movement of a very low earth orbit satellite. [Figure 2B] 1 illustrates an exemplary movement of a very low earth orbit satellite. [Figure 3A] 1 illustrates a system for communication according to some embodiments of the present invention. [Figure 3B] 1 illustrates a system for communication according to some embodiments of the present invention. [Figure 3C] FIG. 10 illustrates an exemplary representation of a first radius and a second radius. [Figure 4] FIG. 2 is an exemplary schematic diagram of a connection request setup according to some embodiments of the present invention. [Figure 5] 1 is a flowchart of a method for communication according to some embodiments of the present invention. [Figure 6] FIG. 1 is a block diagram of an exemplary computing device that can be used in conjunction with some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding, similar, or like features.

[0022] Detailed Description In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and / or circuits have not been described in detail so as not to obscure the present invention.

[0023] Embodiments of the present invention use multiple different satellites in multiple different orbits. Very low Earth orbit (VLEO) satellites, also referred to herein as very low Earth orbit satellites (VLOS satellites), typically orbit at altitudes of less than 400 km to 450 km, e.g., 350 km above the planet's surface. In contrast, low Earth orbit (LEO) satellites typically orbit at altitudes of 600 to 1400 km.

[0024] Another type of satellite that may be used by embodiments of the present invention is a geostationary / geosynchronous satellite that has a geosynchronous orbit (sometimes called a geosynchronous equatorial orbit) and may be referred to as a GEO satellite. GEO satellites typically orbit the Earth at an altitude of 35,786 km above the Earth's equator, have an orbital period equal to the Earth's rotation period, and therefore appear to an observer on Earth to be in a stationary, fixed position.

[0025] For example, because LEO satellites and / or GEO satellites orbit at a greater distance from the center of the Earth than VLEO / VLOS satellites, as used herein, LEO satellites and / or GEO satellites may be referred to as having a "higher" orbit (e.g., than VLEO / VLOS satellites), and VLEO / VLOS satellites may be referred to as having a "lower" orbit (e.g., than LEO and / or GEO satellites).

[0026] Figure 1 shows an example of the visibility period of a single LEO satellite orbiting at 600 km. As can be seen, the overflight of the satellite has a peak visibility period of about 4 minutes, which decreases to a minimum visibility period of about 1.5 minutes.

[0027] VLEO satellites typically have smaller cell diameters than LEO satellites, and the smaller distance between a VLEO satellite and user equipment (UE), such as a mobile phone, on the planet's surface can enable data throughput in the 100 Mbit range, compared to the 0.1 to 1.5 Mbit throughput of user equipment communicating with a LEO satellite (depending on the antenna and scenario). However, a disadvantage of VLEO satellites is the increased velocity due to their lower altitude, and therefore, VLEO satellites do not remain within line of sight (e.g., for communication with user equipment) as much as LEO satellites.

[0028] LEO satellites already play an important role in user equipment idle mode procedures (e.g., 3GPP, TR38.821, TS38.101-4, TS38.304 Rel.-17), where LEO satellites move at a constant speed relative to users on high-speed trains and remain in line of sight for only 2-5 minutes every 12 hours. To date, connection maintenance has been an identified challenge for LEO NTN-NR connectivity; see, e.g., TR38.821.

[0029] 7.3.2.1.4 Frequent and unavoidable handovers Satellites in non-GEO orbits move at high speeds relative to fixed locations on Earth, resulting in frequent and unavoidable handovers for both stationary and moving UEs. This increases signaling overhead, impacts power consumption, and can exacerbate other potential mobility-related challenges, such as service interruptions due to signaling delays. ...From the above analysis, we conclude that while HO frequencies in LEO NTNs may be similar to those experienced by terrestrial UEs on high-speed trains, this represents a worst-case scenario and is not indicative of typical terrestrial networks. Frequent HOs are not expected to occur in GEO due to large cell sizes, which limit the impact of UE speed. Furthermore, in LEO scenarios, UE speed is assumed to be a negligible factor in HO frequencies, given the relative speed of the satellite, which is primarily an issue in LEOs with moving beams.

[0030] The inventors have identified that the situation is further exacerbated due to the typically much higher speeds of VLEO satellites (compared to LEO satellites) and their smaller cell diameters, and therefore existing idle mode / architecture procedures fail given the different speeds and visibility of VLEO satellites.

[0031] For example, as seen in FIG. 2A, very low earth orbit satellites 230_-1, 230_0, 230_1, 230_2, and 230_3, 230_4, and 230_5 (which may be referred to as satellites 230_n, where n is an index, or may simply be referred to as satellites 230) orbit above the Earth's surface 200, which may be, for example, the surface of the Earth.

[0032] Satellite 230_0 has a coverage area 210_0 that includes user equipment 201, and satellite 230_0 can send signals to and receive signals from user equipment 201.

[0033] Satellites 230_3, 230_4, and 230_5 are within range of terrestrial-based core network element 202 (e.g., have a coverage area (not shown) that includes terrestrial-based core network element 202) and can transmit and receive signals to and from core network element 202. For example, satellite 230_3 can transmit and receive signals 220_3 to and from core network element 202, satellite 230_4 can transmit and receive signals 220_4 to and from core network element 202, and satellite 230_5 can transmit and receive signals 220_5 to and from core network element 202.

[0034] Satellites 230_0, 230_1, 230_2, and 230_3 form a sequence 235 of satellite hops (e.g., the satellites form a chain of connections) from user equipment 201 to ground-based core network element 202. Sequence 235 is shown as a minimum sequence because satellites 230_4 and 230_5 are also within range of core network element 202 but are not shown to be included in sequence 235.

[0035] 2B illustrates a later point in time for VLOS satellites 230_-1, 230_0, 230_1, 230_2, 230_3, 230_4, and 230_5 as they move above the Earth's surface 200 (the satellite movement direction is shown in the figure as moving from left to right). Satellite 230_-2 is "coming in" from the left, as it was not "seen" (e.g., to an observer / user equipment proximal to the location shown) at the time illustrated in FIG. 2A, representing the satellite's periodic visibility.

[0036] The coverage area 210_0 from satellite 230_0, which included user equipment 201 at the time shown in Figure 2A, has moved with satellite 230_0 (not shown in Figure 2B) so that at the time shown in Figure 2B it no longer includes user equipment 201. Satellite 230_-1 has moved so that its coverage area 210_-1 now includes user equipment 201.

[0037] Similarly, satellite 230_2 is within range of core network element 202 and can send signals 220_2 to and receive signals from core network element 202. Satellite 230_5 has moved out of range of core network element 202 and can no longer send or receive signals to core network element 202.

[0038] Here, the (minimum) sequence 235 of satellite hops connecting the user equipment 201 and the core network element 202 includes satellites 230_-1, 230_0, 230_1, and 230_2.

[0039] Thus, for any satellite network in a lower orbit with cells having smaller diameters and faster-moving satellites (which also increase Doppler), handover and connection stability become more problematic. For example, as shown between Figures 2A and 2B, satellite 230_0 needed to hand over the connection to user equipment 201 to satellite 230_-1. As the satellites orbit, subsequent handovers, for example from satellite 230_-1 to satellite 230_-2, are required, which occurs more frequently due to the increased orbital velocity of very low Earth orbit satellites compared to LEO satellites.

[0040] While handover density in LEO is comparable to high-speed train handovers, handover speeds in VLOS constellations are rather in the range of jet speeds, ignoring the motion of the UE itself.

[0041] However, as explained, more satellites flying in lower orbits have the potential to increase throughput and spectral efficiency. Therefore, to improve capacity and address the problems identified above, multi-orbit constellations including interactions with existing LEO or GEO satellites are proposed by embodiments of the present invention, which can increase capacity and throughput using novel 3D (e.g., multi-orbit) network architectures and can be inherently part of 6G systems.

[0042] Embodiments of the present invention address link maintenance, e.g., maintaining connectivity even at lower rates. The problem as illustrated in Figures 2A and 2B is further explained, and a solution according to an embodiment of the present invention is presented in Figures 3A and 3B.

[0043] Therefore, the problem that the present invention can solve can be formulated as how to balance increased data throughput using VLEO / VLOS satellites with increased handover frequency.

[0044] An embodiment of the present invention solves this problem by placing core network functions on satellites in higher orbits (e.g., GEO or LEO), which have the advantage of being stable but the disadvantage of not having very high throughput. Therefore, an embodiment of the present invention further includes a constellation of VLOS orbit satellites (e.g., a 3D network) to provide connectivity organized by the higher orbit satellites that instantaneously cover an area. The low orbit satellites provide data user plane functionality organized by the high orbit control functions, thereby achieving control and user plane separation (CUPS). For example, the high orbit satellites hold the core functions and know which satellites are next to serve and which satellites are needed for connectivity backlink to Earth, and can therefore provide the respective information to the satellites. The low orbit satellites effectively act only as data pumps, while the high orbit satellites handle connection control and configuration; therefore, the low orbit satellites can only be used when the UE is operating in a connected mode (including discontinuous transmission (DTX) and on hold states). Therefore, low-earth orbit satellites do not need to perform non-access stratum signaling (NAS) procedures such as paging while the UE is in idle mode. This also means that system information block (SIB) provisioning is limited to a limited level if more than SSB (synchronization signal block) or CD-SSB (cell-defining SSB) is present. For example, low-earth orbit satellites may only provide SSB-CD during satellite chain initialization (e.g., configuration from the first satellite) to clarify their use over the inter-satellite link (ISL).

[0045] Thus, because LEO satellites (or even satellites in higher orbits such as GEO satellites) move less frequently relative to the UE, they can form a constant serving base suitable for maintaining less time-critical core network signaling and general UE connectivity.

[0046] Embodiments of the present invention can improve existing networks used for vertical technologies such as automotive, tracking, and / or first responders (see, for example, 5GAA: 5G Automotive Association's NTN 4V2X) and can provide a robust architecture to maintain connectivity for use cases such as remote piloting, drone control, etc.

[0047] 3A and 3B illustrate a system for communication according to some embodiments of the present invention. The system for communication includes a user equipment 301, a terrestrial-based core network element 302, such as an Access and Mobility Management Function (AMF), a first satellite 303, and a plurality of second satellites..., 330_-2, 330_-1, 330_0, 330_1, 330_2, 330_3, 330_4, 330_5,.... The second satellites may be collectively referred to as 330 or 330_n (n is an index).

[0048] The first satellite 303 may be a GEO or LEO satellite and may be characterized by having a first orbit defined by a first radius R1. For example, in one embodiment, the first satellite may be a LEO satellite having a first radius, e.g., greater than 600 km. The radius R1 may be measured from the center of a planet (e.g., Earth) above which the first satellite orbits. The radius R1 may be measured from the planet's surface 300 (e.g., assuming a uniform surface). Figure 3C shows an exemplary representation of the first radius R1.

[0049] The plurality of second satellites 330_n may be VLEO / VLOS satellites, each may have a second orbit, and each second orbit is defined by a radius R2_n (n is the index of each second satellite). As shown in FIG. 3C, each second radius R2_n is smaller than the first radius R1 such that the first satellite 303 is in a "higher" orbit than each of the plurality of second satellites. The plurality of second satellites may all share a common second radius (e.g., simply denoted as R2), for example, the plurality of second satellites may orbit in the same orbital plane. FIG. 3C shows an exemplary representation of the second radius R2_n of satellite 330_-2 (having radius R2_-2) and satellite 330_4 (having radius R2_4). As shown in FIG. 3C, R2_-2 < R1 and R2_4 < R1. In some embodiments, R2_-2 may be equal to R2_4 (e.g., some or all of R2_n may be equal).

[0050] At least two of the plurality of second satellites may be operated by different mobile network operators "MNOs". For example, in order to provide a larger potential coverage, satellites from multiple MNOs can be (e.g., conditional on an agreement) recruited.

[0051] As shown in FIG. 3A, the first satellite 303 communicates (e.g., can transmit and receive signals) with each of the UE 301 and the core network element 302. For example, the first satellite 303 can transmit and receive a signal 350 with the user equipment 301 and can transmit and receive a signal 355 with the core network element 302. Also, the first satellite 303 communicates with at least a portion of the second satellites 330_n (e.g., second satellites within the range of the first satellite 303).

[0052] The first satellite 303 is adapted to perform several steps in response to a setup request received from the UE 301. For example, the UE 301 can send an SRB1 setup request to the first satellite 303 as a primary cell. In particular, the first satellite 303 sends the setup request to the terrestrial core network element 302. The UE accesses the satellite 303 when the satellite performs all the necessary routines and emissions (SIB signaling) required for the satellite to be an anchor cell, i.e., the UE can camp on it and perform all authentication requests via the core network through the satellite. The VLOS satellite, also referred to herein as the second satellite, may be a non-anchor satellite, i.e., it does not provide the necessary system information (SIB for camping and accessing the core network through the satellite). The first satellite 303 can also handle the initial UE P-RACH (physical random access channel) process since the second satellite 330_n may not be suitable for P-RACH setup, and the objective of the present invention is to localize the NAS (non-access stratum signaling) handling and core functions in a more stable high-orbit satellite (e.g., the first satellite 303).

[0053] The first satellite 303 configures a sequence of second satellites 335 of the plurality of second satellites according to the coverage areas of the sequence of second satellites and the locations of the UE 301 and the core network element 302 relative to the coverage areas based on the setup configuration received from the core network element 302. For example, the first satellite 303 may configure second satellites 330_0, 330_1, 330_2, and 330_3 (e.g., via signals 360, not all of which are shown) to form the sequence of second satellites 335. The sequence of second satellites 335 includes a serving satellite (e.g., 330_0) for serving the UE 301. The sequence 335 may optionally include a second satellite 330_4 (e.g., configured by the first satellite 303 using signal 365) because this satellite is within range of the core network element 302 and can provide a backup connection 370 to the core network element 302, although embodiments of the present invention may seek to maintain a minimum sequence 335 (e.g., including as few second satellites as possible) to conserve inter-satellite resources and extend the operational life of the satellites.

[0054] The sequence of second satellites 335 is adapted to provide a first user data connection between UE 301 and core network element 302. For example, via several satellite hops (e.g., a chain of connections) between second satellites in sequence 335, a secondary user data plane within the meaning of 3GPP is created between UE 301 and core network element 302. If a connection failure occurs between UE 301 and the serving satellite, UE 301 can indicate to first satellite 303 (e.g., via SRB1) that a secondary cell (e.g., second satellite 330_0) is gone. First satellite 303 can then compile a new sequence for UE 301 and indicate to UE 301 which of the second satellites should be used for the connection.

[0055] In some embodiments, providing a first user data connection between the UE 301 and the terrestrial-based core network element 302 includes communication via inter-satellite links "ISLs" 340 between satellites included in the sequence. For example, in FIG. 3A , satellites 330_0, 330_1, 330_2, and 330_3 may communicate via ISLs (e.g., communication between 330_0 and 330_1, communication between 330_1 and 330_2, etc.) to provide the first user data connection between the UE 301 and the core network element 302. Satellite 330_3 is shown as the last link in the sequence, communicating with the core network element 302 via signal 312.

[0056] It will be appreciated that depending on the distance between the UE 301 and the core network element 302, a greater or lesser number of intermediate second satellites in the sequence 335 may be necessary or sufficient to establish a "backlink" to the terrestrial-based core network element 302.

[0057] In some embodiments, at least one of the plurality of second satellites, e.g., the second satellite in sequence 335, may be a non-anchor cell for UE 301. A non-anchor cell according to 3GPP is a cell that does not provide the necessary system information (SIB) and is therefore only used in conjunction with dedicated mode, i.e., when the UE has an active data session, and is therefore not suitable for camping or initial access to be performed by the UE toward the core network. In some embodiments, first satellite 303 is the anchor cell for UE 301. For example, UE 301 may consider a low-orbit VLOS satellite as a secondary cell, i.e., a non-anchor cell, while the UE anchor cell is in a high orbit. The anchor cell is a cell to which the UE assumes SSB, and from which system information and paging are transmitted. While the concepts of anchor and non-anchor cells have existed previously specifically for NB-IoT carriers, in the context of the present invention, these terms apply to cells generally; for example, a VLOS satellite is a non-anchor cell. The second satellite may be provided as a non-anchor cell, thereby avoiding the UE camping on the second satellite, which avoids UE battery drain due to frequent idle mode movements and SIB reads due to the frequency of handovers between VLOS satellites as a result of their orbits.

[0058] The second satellite may only provide PSS blocks (packet switched streaming) for connection maintenance, identification, and ballistic indication measurements. General SIBs for neighboring cells / frequencies or service configuration may not be provided. This information may be provided by the first satellite (e.g., LEO / GEO), and depending on UE requirements and control considerations, the serving and so-called "drift" second satellite is configured by the control network via the first satellite to handle the user plane.

[0059] In some embodiments, the UE 301 is prevented from camping on the second sequence of satellites 335 (e.g., prevented from camping on any of the satellites included in the sequence). For example, a VLOS satellite does not provide the necessary system information, i.e., MIB master information, that allows for camping or directly indicating non-anchor / non-camping cells in its PBCH (Physical Broadcast Channel).

[0060] The first satellite 303 is further adapted to iteratively update the sequence of second satellites 335 based on the changing coverage areas of the sequence of second satellites. The first satellite 303 does this by being adapted to configure one second satellite of the plurality of second satellites to be a new serving satellite to be included in the sequence if the coverage area of ​​an existing serving satellite no longer includes the UE 301. The first satellite 303 may also configure one second satellite of the plurality of second satellites having a coverage area that includes terrestrial-based core network elements to be included in the sequence if there is no second satellite currently in the sequence that has a coverage area that includes terrestrial-based core network elements.

[0061] For example, as shown in FIG. 3A , the second satellite sequence 335 includes satellites 330_0, 330_1, 330_2, and 330_3, where satellite 330_0 is the serving satellite that serves UE 301. As the satellites move above the Earth's surface 300, the situation in FIG. 3B (and as described with respect to FIG. 2B ) occurs when the existing serving satellite 330_0 no longer has a coverage area 310_0 that includes UE 301. However, satellite 330_-1 has moved (e.g., drifted) to have a coverage area 310_-1 that includes UE 301. The first satellite 303 can configure satellite 330_-1 to become the new serving satellite that serves UE 301. The first satellite 303 can do this prior to (e.g., during a predetermined time before) a change in serving satellite; for example, the first satellite 303 can prepare satellite 330_-1 (e.g., by configuration 362) to take over as the serving satellite. Satellite 303_0 can change its status to a removed serving satellite (e.g., by reconfiguration from the first satellite 303), and satellite 330_-1 will be considered part of the second satellite's sequence 335. Satellite 330_0 can remain in sequence 335 as an intermediate satellite. Such a sequence update reflects the handover from satellite 330_0 to satellite 330_-1 as the serving satellite.

[0062] At the other "end" of the sequence, satellite 303_4 has moved far enough to have a coverage area that no longer includes core network element 302 (e.g., is no longer within range), and satellite 303_2 has moved far enough that it now has a coverage area that includes core network element 302. Satellite 330_2 may be configured by the first satellite 303 to communicate with core network element 302 (e.g., via signal 312). Alternatively, because satellite 330_2 was already included in sequence 335, no further configuration by the first satellite 303 may be required. Satellite 303_4, if included, may be removed from sequence 335 (e.g., by reconfiguration from the first satellite 303). The satellite 303_3 still has a coverage area that includes the core network element 302 and may therefore optionally remain in the sequence 335 as a backup, redundant, or fail-safe connection 370 to the core network element 202, for example, in case of a connection problem with the second satellite 330_2. For example, the satellite 330_3 may be configured / reconfigured by the first satellite 303 using the signal 365. Thus, the updated sequence 335 includes the second satellites 330_-1, 330_0, 330_1, 330_2, and optionally 330_3. When the satellite 330_-1 moves out of range of the UE 301, the first satellite 303 can prepare the second satellite 330_-2 (e.g., using the configuration 362) to be included in the sequence 335 after the next update to the sequence.

[0063] As an example, sequence 335 can be considered to be updated by a circular shift of the second satellite index, 330_-1 → 330_0, 330_0 → 330_1, ..., etc., where 330_0 represents the serving satellite (e.g., index n=0 represents the serving satellite).

[0064] 3A and 3B are shown as moving from left to right, embodiments of the present invention are equally applicable to other movements of the satellite in 3D space, such as from right to left in a 2D diagram, or into and out of the page. Additionally, although UE 301 is shown in 2D space as being to the left of core network element 302, other configurations in 3D space are possible.

[0065] In some embodiments, the first satellite 303 may configure one second satellite of a plurality of second satellites having a coverage area that includes the terrestrial-based core network element 302 to be included in the sequence. For example, in Figures 3B and 3A, if the satellites were moving from right to left (e.g., reversing the direction shown), the first satellite 303 could configure the "incoming" satellite 330_4 to be included in the sequence 335.

[0066] In some embodiments, the first satellite 303 may maintain an additional user data connection with the UE 301. The additional user data connection may be a "backup" data connection, e.g., the first satellite 303 may transmit data to or receive data from the UE 301 via such additional user data connection if the first user data connection (e.g., as provided by the second satellite sequence 335) is lost. For example, the signal 350 between the UE 301 and the first satellite 303 and the signal 355 between the first satellite 303 and the core network element 302 may represent such an additional user data plane. As discussed, the first user data connection may have the functionality of a secondary user plane, and the further user data connection (between the first satellite and the UE) may have the functionality of a primary user plane.

[0067] In some embodiments, the first satellite 330 performs non-access stratum (NAS) signaling with the UE 301.

[0068] In some embodiments, the UE 301 monitors the first satellite 303 when the UE is in idle mode.

[0069] In some embodiments of the present invention, a serving satellite may be adapted to perform an inter-satellite hybrid automatic repeat request (HARQ) process. For example, an inter-satellite HARQ process may involve a serving satellite transmitting user data and information related to generating an HARQ redundancy version to a second adjacent satellite in a sequence before the serving satellite's coverage area no longer contains the UE. HARQ redundancy versions are a known 3GPP feature in which each transmission is self-decodable but also decodable in the event of a reception error in the combination. Thus, some embodiments of the present invention relate to HARQ processes performed between two satellites when handovers may occur very frequently, avoiding having to restart the HARQ process of an ongoing transmission from scratch at each handover. If the new serving satellite is aware of the ongoing HARQ process and the received or generated redundancy versions, it can maintain and complete the HARQ process in conjunction with the data received from the previous serving satellite.

[0070] 3A and 3B , while satellite 330_0 still has coverage area 310_0 that includes UE 301, but before satellite 330_0 moves such that coverage area 310_0 no longer includes UE 301, serving satellite 330_0 can transmit data 342 related to the generation of HARQ redundancy versions to satellite 330_-1. Serving satellite 330_0 can transmit such data 342 to satellite 330_-1 because it is a neighboring satellite due to satellite 330_-1 becoming the new serving satellite. Thus, the serving satellite not only provides data to the user plane, but also, depending on the remaining coverage time, can forward a portion of the user data to the next serving satellite in the event of an error (e.g., a retransmission for the user) to complete the provision.

[0071] Although latency is reduced to 10 ms, handovers and serving satellite changes are very frequent, i.e., service times are often less than a minute or even double-digit seconds, necessitating seamless provision of data and HARQ processes across base stations / satellites. HARQ processes can involve several retransmissions of different redundancy versions, thus requiring some double-digit milliseconds. As a result, the number of incomplete HARQ processes resulting from subsequent handovers can increase. Therefore, resuming each interrupted process can cause delays, and therefore, inter-satellite HARQ processes according to embodiments of the present invention can be advantageous. For such processes, providing relevant information about data and HARQ processes can enable improved throughput and more efficient data sessions.

[0072] Due to the high density of HARQ process interruptions, some embodiments of the present invention provide a new feature within the handover process whereby all the information required to maintain and complete ongoing HARQ processes is provided during handover.

[0073] Satellites 330_3 and 330_4 may also perform HARQ processes, with satellite 330_3 sharing data 345 related to the generation of HARQ redundancy versions for communication with core network element 302.

[0074] Thus, embodiments of the present invention address fast handover speeds with such modified HARQ processes including data transfer which avoids handover interruptions and makes handover more robust by maintaining ongoing HARQ processes, and in case of a failure, the UE still maintains a smaller connection via a higher satellite for maintaining connectivity, avoiding radio link failure (RLF) altogether.

[0075] One embodiment of the present invention relates to a satellite adapted to act as a first satellite described herein, such as first satellite 303. It will be appreciated that multiple satellites adapted to act as first satellites may be deployed to provide coverage over a wide area on the Earth.

[0076] Another embodiment of the present invention relates to a satellite adapted to perform the role of a second satellite (such as one of a plurality of second satellites 330_n) described herein. Such a satellite may be part of a constellation of similar satellites.

[0077] 4 shows an exemplary schematic diagram of a connection request setup according to some embodiments of the present invention. In FIG. 4, a first satellite is a GEO / LEO satellite and multiple second satellites are VLOS satellites. Ground 402 represents a core network element located on the ground. Time can be considered to progress "downward" in FIG. 4.

[0078] 4, UE 401 sends a setup request (step 451) to GEO / LEO satellite 403. In addition to UE capabilities (such as frequency bands to be used), the setup request may also include UE authentication data, thus driving the rates or services the UE is allowed to receive.

[0079] The GEO / LEO satellite 403 transmits a setup request to the ground 402 (step 452). The ground 402 transmits a setup configuration to the GEO / LEO satellite 403 (step 453).

[0080] GEO / LEO satellite 403 configures the serving VLOS for VLOS satellite 430 (step 454) and configures the drift VLOS (e.g., updates the serving VLOS as needed) (step 455). For example, as shown in FIG. 3A , first satellite 303 may configure second satellite 330_0 as the serving satellite and configure second satellite 330_-1 as the drift satellite that will take over as the serving satellite from second satellite 330_0 at a future point in time.

[0081] The VLOS satellites 430 establish inter-satellite links (ISLs) among themselves (step 456). For example, as shown in Figure 3A, inter-satellite link 340 enables the second satellite in sequence 335 to form a connection from the user equipment to core network element 302. The configured VLOS satellite 430 sends a setup request to ground 402 using the configuration from the VLOS configuration (step 457).

[0082] The ground 402 sends an acknowledgement to the VLOS satellite 430 that the backlink has been established (step 458). The GEO / LEO satellite 403 sends a setup acknowledgement to the UE 401, including the VLOS configuration (step 459). The UE 401 sends a connection request to the serving VLOS 430 using the VLOS configuration (step 460). The serving VLOS sends a setup acknowledgement to the UE 401 (step 461). The UE 401 and ground 402 are then connected via a user data plane that does not include the GEO / LEO satellite 403 (step 462).

[0083] 5 shows a flowchart of a method 500 for communication according to some embodiments of the present invention. Method 500 can be implemented by a system such as that shown in FIGS. 3A and 3B.

[0084] Method 500 includes transmitting a setup request from a user equipment “UE” to a ground-based core network element by a first satellite (step 510). For example, a UE (such as UE 301) may transmit a setup request, such as to set up an SRB1, to a first satellite (which may be a high-orbit satellite such as a LEO or GEO satellite, such as first satellite 303). The first satellite has a first orbit defined by a first radius (e.g., R1 as shown in FIG. 3C). The first satellite may be adapted to relay the setup request to a ground-based core network element (such as ground-based core network element 303).

[0085] The method 500 includes configuring, by a first satellite, a sequence of a second satellite of a plurality of second satellites (step 520).

[0086] For example, the plurality of second satellites may be a set (e.g., a constellation) of VLEO / VLOS satellites, and the sequence of second satellites may be a subset of satellites in the set of VLEO / VLOS satellites. The plurality of second satellites may be as described for the satellite 330_n illustrated in FIGS. 3A-3C. Each satellite 330_n of the plurality of second satellites has a second orbit, each second orbit defined by a second radius (e.g., radius R2_n illustrated in FIG. 3C), each second radius being smaller than the first radius. For example, the first satellite may be a low Earth orbit (LEO) satellite or a geosynchronous equatorial orbit (GEO) satellite in a higher orbit than each of the plurality of second satellites. The plurality of second satellites may be very low Earth orbit (VLEO / VLOS) satellites in a lower orbit than the first satellite. The orbits of the second satellites may be the same or different, e.g., some second satellites may orbit in a first orbital plane and some other second satellites may orbit in a second orbital plane. At least two of the plurality of second satellites may be operated by different mobile network operators (MNOs), such that the plurality of second satellites need not all be of the same design.

[0087] The configured sequence of second satellites may be a sequence such as sequence 335 shown in FIG. 3A. In particular, the configuration by the first satellite is based on a setup configuration received from a terrestrial core network element. Configuring the sequence of second satellites among the plurality of second satellites is based on a coverage area of ​​the sequence of second satellites and the location of the UE and / or terrestrial core network element relative to the coverage area.

[0088] 3A , second satellites 330_0, 330_1, 330_2, and 330_3 have coverage areas (e.g., a total coverage area composed of individual coverage area 310_0 of satellite 330_0 combined with ISLs 340 between intermediate satellites 330_1-330_3 and connection 312 between satellite 330_3 and core network element 302) that include UE 301 and core network element 302 and enable connection of UE 301 to core network element 302. These satellites may be configured as a sequence 335 of second satellites spanning several satellite hops that connect UE 301 and core network element 302. The second satellite sequence includes serving satellites for serving the UE, for example, second satellite 330_0 is the serving satellite in FIG. 3A having an individual coverage area 310_0 that includes UE 301, and second satellite 330_-1 is the serving satellite in FIG. 3B having an individual coverage area 310_-1 that includes UE 301.

[0089] In some embodiments, the sequence of second satellites includes adjacent members of a plurality of second satellites, for example, satellites 330_0 through 330_3 as shown in Figure 3A and satellites 330_-1 through 330_2 as shown in Figure 3B. Configuring the second satellite of the sequence with the first satellite may include including or releasing, or adjusting the configuration of, additional satellites for ISL reach to the ground station.

[0090] The method 500 may include providing a user data connection between the UE and a terrestrial core network element via a second sequence of satellites (step 530). For example, the second sequence of satellites may provide a user data connection functioning as a primary user plane connection. In FIG. 3A , the user data connection / primary user plane connection includes the UE 301 transmitting and receiving signals 311 to and from the second satellite 330_0, the second satellite 330_0 communicating with the second satellite 330_1, e.g., via an inter-satellite link 340, the second satellite 330_1 communicating with the second satellite 330_2, e.g., via an inter-satellite link 340, the second satellite 330_2 communicating with the second satellite 330_3, e.g., via an inter-satellite link 340, and the second satellite 330_3 transmitting and receiving signals 312 to and from the core network element 302.

[0091] The method 500 may include repeatedly updating the sequence of second satellites by the first satellite based on the changing coverage area of ​​the sequence of second satellites (step 540). The updating may include configuring a second satellite included in the sequence to become a new serving satellite when the coverage area of ​​an existing serving satellite no longer includes the UE. For example, as shown in Figures 3A and 3B, the sequence of second satellites 335 is updated to take into account the changing coverage area of ​​the second satellite 330_0, which is the serving satellite in Figure 3A. The sequence 335 in Figure 3A includes satellites 330_0, 330_1, 330_2, and 330_3. As satellite 330_0 orbits away from UE 301, satellite 330_-1 may be configured to be taken over as the serving satellite by the first satellite 303 in a higher orbit, and thus in FIG. 3B , sequence 335 has been updated by the first satellite 303 to include satellite 330_-1 (the new serving satellite), satellites 330_0, 330_1, and 330_2. Satellite 330_3 may be removed from the updated sequence to maintain a minimum sequence (thereby conserving satellite resources and extending operational life), or may be retained to provide a backup connection to core network element 302.

[0092] The updating may further include configuring a second satellite of a plurality of second satellites having a coverage area that includes the terrestrial core network element to be included in the sequence. For example, at the "tail" of the sequence, as satellite 330_4 orbits away from the terrestrial core network element, a first satellite in a higher orbit may configure satellite 330_1 to communicate with core network element 302 because satellite 330_1 orbits toward the terrestrial core network element. The term "drift satellite" may be used to refer to a satellite that is not the serving satellite but is adjacent in the sequence due to "drifting" its respective coverage area into the area of ​​coverage of a UE or core network element.

[0093] 3A and 3B, because the satellite movement direction is from left to right, satellite 330_1 was already in sequence 335 shown in FIG. 3A and sequence 335 shown in FIG. 3B. However, if the satellite movement direction shown in FIG. 3A and 3B were reversed (FIG. 3A being at a later point in time than FIG. 3B), it will be appreciated that the first satellite 303 would need to update sequence 335 such that satellite 330_4 is added to sequence 335 as satellite 330_3 moves out of range of core network element 302 and as satellite 330_4 moves into range of core network element 302. A similar process occurs at the other end of the sequence, with satellite 330_-1 leaving as the serving satellite and satellite 330_0 taking over as the serving satellite due to the UE's location relative to satellites 330_-1 and 330_0's respective coverage areas 310_-1 and 310_0.

[0094] Figure 6 shows a block diagram of an exemplary computing device 100 that can be used with some embodiments of the present invention. For example, one or more of the first satellite 303 or second satellites 330_n described herein can include a computing device 100 according to Figure 6. The computing device 100 can include a controller or computer processor 105, which can be, for example, a central processing unit (CPU), a chip, or any suitable computing device, an operating system 115, memory 120, storage 130, input devices 135, and an output device 140, such as a computer display or monitor that displays, for example, a computer desktop system.

[0095] The operating system 115 may be or include code for performing tasks including coordinating, scheduling, arbitrating, or managing the operation of the computing device 100, e.g., scheduling program execution. The memory 120 may be or include, for example, random access memory (RAM), read-only memory (ROM), flash memory, volatile or non-volatile memory, or other suitable memory or storage unit. At least a portion of the memory 120 may include data storage housed online on the cloud. The memory 120 may be or include multiple different memory units. The memory 120 may store, for example, instructions (e.g., code 125) for performing the methods disclosed herein. The memory 120 may use a data store such as a database.

[0096] Executable code 125 may be any application, program, process, task, or script. Executable code 125 may be executed by controller 105, possibly under control of operating system 115. For example, executable code 125 may be or execute one or more applications that implement methods disclosed herein, such as method 500 shown in FIG. 5. In some embodiments, multiple computing devices 100 or components of device 100 may be used. One or more processors 105 may be configured to perform embodiments of the present invention, for example, by executing software or code.

[0097] Storage 130 may be or include, for example, a hard disk drive, a floppy disk drive, a compact disk (CD) drive, a universal serial bus (USB) device, or other suitable removable and / or fixed storage unit. Data described herein may be stored in storage 130 and loaded from storage 130 into memory 120, where it may be processed by controller 105. Storage 130 may include cloud storage. Storage 130 may include storing data in a database.

[0098] Input device(s) 135 may be or include a mouse, keyboard, touchscreen or pad, or any suitable input device or combination of devices. Input device(s) 135 may include a receiver, such as an antenna receiver. Output device(s) 140 may include one or more displays, speakers, and / or any other suitable output device or combination of output devices. Output device(s) 140 may include a transmitter, such as an antenna transmitter. Any applicable input / output (I / O) devices may be connected to computing device 100, and may include, for example, a wired or wireless network interface card (NIC), a modem, a printer, a universal serial bus (USB) device, or an external hard drive, to input device(s) 135 and / or output device(s) 140.

[0099] Embodiments of the present invention may include one or more articles (e.g., memory 120 or storage 130), e.g., computer or processor non-transitory readable media, or computer or processor non-transitory storage media, e.g., memory, disk drive, or USB flash memory, that encode, include, or store instructions, such as computer-executable instructions, that, when executed by, e.g., a processor or controller, perform the methods disclosed herein.

[0100] It is anticipated that embodiments of the present invention may have an impact on existing or future non-terrestrial network telecommunications architectures and associated standards. For example, embodiments of the present invention may be utilized in beyond 5G, 6G, and future NTN architectures. The continued development of these standards, as well as the conceptualization and implementation of future standards, may rely on the systems and / or methods of the present invention.

[0101] For example, embodiments of the present invention can extend the capabilities of 3GPP and / or 6G standards in that a sequence of high-Earth orbit satellites and low-Earth orbit satellites provides control and user plane separation that balances high data throughput and connection stability. High-Earth orbit satellites provide core functions, orchestrating low-Earth orbit satellites to provide the user data plane between user equipment and core network elements. The low-Earth orbit satellites effectively act only as data pumps, with the high-Earth orbit satellites handling connection control and configuration; therefore, the low-Earth orbit satellites may only be used when the UE is operating in connected mode. Therefore, the low-Earth orbit satellites do not need to perform non-access stratum signaling procedures such as paging while the UE is in idle mode.

[0102] Unless otherwise indicated, and as is apparent from the foregoing description, throughout this specification, descriptions utilizing terms such as "processing," "computing," "calculating," "determining," and the like will be understood to refer to operations and / or processes of a computer or computing system, or similar electronic computing device, that manipulate and / or transform data represented as physical quantities, such as electronic quantities, in the registers and / or memory of the computing system into other data that are similarly represented as physical quantities in the memory, registers, or other such information storage, transmission, or display device of the computing system.

[0103] Embodiments of the present invention may include articles such as computer or processor readable non-transitory storage media, e.g., memory, disk drive, or USB flash memory, that encode, include, or store instructions, e.g., computer-executable instructions, that, when executed by a processor or controller, cause the processor or controller to perform the methods disclosed herein.

[0104] It should be recognized that embodiments of the present invention may solve one or more of the objects and / or problems set forth in the background, and that embodiments of the present invention need not meet all of the above objects and / or problems to fall within the scope of the present invention. While certain features of the present invention have been particularly illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes in form and detail as fall within the true spirit of the invention.

[0105] In the above description, an embodiment is an example or implementation of the present invention. The appearances of "one embodiment," "one embodiment," or "some embodiments" in various places do not necessarily all refer to the same embodiment.

[0106] While various features of the present invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, while the present invention may be described herein in the context of separate embodiments for clarity, the present invention may also be implemented in a single embodiment. While the present invention has been described with respect to a limited number of embodiments, those skilled in the art should understand that one or more features from one particular embodiment or group of embodiments can be combined with features of another embodiment or group of embodiments.

[0107] References herein to "some embodiments," "one embodiment," "one embodiment," or "other embodiments" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least some embodiments of the invention, but not necessarily in all embodiments.

[0108] It is to be understood that the phraseology and terminology employed herein should not be construed as limiting, but is for the purpose of description only.

[0109] It is to be understood that the details set forth herein are not to be construed as limitations on the application of the present invention.

[0110] It is to be understood that the terms "including," "comprising," and "consisting" and grammatical variations thereof do not exclude the addition of one or more elements, features, steps, or integers or groups thereof, and that these terms should be interpreted as specifying elements, features, steps, or integers.

[0111] If the specification or claims refer to an "additional" element, it does not exclude the presence of more than one of the additional element.

[0112] When a claim or the specification refers to "a" or "an" element, it is to be understood that such a reference should not be interpreted as referring to only one of that element.

[0113] When the specification states that a component, feature, structure, or characteristic "may include," "could include," "could include," or "may include," it is understood that the particular component, feature, structure, or characteristic need not be included.

[0114] Where applicable, embodiments may be described using state diagrams, flow diagrams, or both, but the invention is not limited to those diagrams or corresponding descriptions, e.g., flow need not move through each illustrated box or state or in the exact same order as illustrated and described.

Claims

1. 1. A method for communication, comprising: sending, by a first satellite (303), a setup request to a ground-based core network element (302) in response to a registration request from a user equipment (UE) (301); configuring, by the first satellite, a sequence (335) of second satellites (330_n) according to a coverage area of ​​the sequence of second satellites and a location of the UE and the terrestrial core network element relative to the coverage area based on a setup configuration received from the terrestrial core network element responding to the setup request, wherein the sequence of second satellites includes a serving satellite for serving the UE; providing a first user data connection between the UE and the terrestrial core network element via the second sequence of satellites; iteratively updating, by the first satellite, the sequence of second satellites based on changing coverage areas of the sequence of second satellites, the updating including: configuring one second satellite of the plurality of second satellites to be a new serving satellite included in the sequence if the coverage area of ​​an existing serving satellite no longer includes the UE; and configuring one second satellite of the plurality of second satellites having a coverage area including the terrestrial core network element to be included in the sequence if a second satellite currently in the sequence does not have a coverage area that includes the terrestrial core network element; Including, the first satellite has a first orbit defined by a first radius (R1); Each satellite (330_n) of the plurality of second satellites has a second orbit, each second orbit defined by a second radius (R2_n), each second radius being smaller than the first radius.

2. The method of claim 1 , wherein the plurality of second satellites are very low earth orbit (VLEO) satellites.

3. 3. The method of claim 1 or claim 2, wherein the first satellite is one of a low earth orbit (LEO) satellite or a geosynchronous equatorial orbit (GEO) satellite.

4. 2. The method of claim 1, comprising maintaining, by the first satellite, a further user data connection with the UE, and transmitting data over the further user data connection if the first user data connection is lost.

5. 5. The method of claim 4, wherein the first user data connection has a secondary user plane function and the further user data connection has a primary user plane function.

6. The method of claim 1 , further comprising preventing the UE from camping on the second sequence of satellites.

7. The method of claim 1 , wherein the first satellite is an anchor cell for the UE.

8. The method of claim 1 , wherein at least one second satellite of the plurality of second satellites is a non-anchor cell for the UE.

9. 2. The method of claim 1, comprising performing non-access stratum signaling (NAS) with the UE by the first satellite.

10. 2. The method of claim 1, wherein providing the first user data connection between the UE and the terrestrial core network element comprises communication via inter-satellite links (ISLs) between satellites included in the sequence.

11. 11. The method of claim 10, comprising performing an inter-satellite hybrid automatic repeat request (HARQ) process, the inter-satellite HARQ process comprising transmitting, by the serving satellite, user data and information related to generating a HARQ redundancy version to an adjacent second satellite in the sequence before the coverage area of ​​the serving satellite no longer includes the UE.

12. The method of claim 1 , comprising monitoring, by the UE, the first satellite when the UE is in an idle mode.

13. The method of claim 1 , wherein at least two of the plurality of second satellites are operated by different mobile network providers (MNOs).

14. 1. A system for communications, comprising: A user equipment "UE (user equipment)" (301), a first satellite (303) having a first orbit defined by a first radius (R1); a plurality of second satellites (330_n), each having a second orbit, each second orbit defined by a second radius (R2_n), each second radius being smaller than the first radius; a terrestrial-based core network element (302); Equipped with The first satellite, in response to a registration request from the UE, sending a setup request to the terrestrial core network element; configuring, based on a setup configuration received from the terrestrial core network element, a sequence of second satellites (335) of the plurality of second satellites according to a coverage area of ​​the sequence of second satellites and a location of the UE and the terrestrial core network element relative to the coverage area, wherein the sequence of second satellites includes a serving satellite for serving the UE; and adapted to: the second sequence of satellites is adapted to provide a first user data connection between the UE and the terrestrial core network element; The first satellite and iteratively updating the sequence of second satellites based on their changing coverage areas by configuring one second satellite of the plurality of second satellites to be a new serving satellite included in the sequence if the coverage area of ​​an existing serving satellite no longer includes the UE, and configuring one second satellite of the plurality of second satellites having a coverage area that includes the terrestrial core network element to be included in the sequence if a second satellite currently in the sequence does not have a coverage area that includes the terrestrial core network element.

15. A satellite adapted to perform the role of the first satellite in the method of claim 1.

16. A satellite adapted to perform the role of the second satellite in the method of claim 1.

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