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 THEINVENTION 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 rail industries require higher throughput for some of their scenarios so that they can be reliably served by NTN. Current NTN network / cell capacity is in the range of a few Mbits in LEO (Low Earth Orbit) with VSAT (very small aperture terminal). It is considered to increase the throughput concept on VLOS (Very Low Orbit Satellite). 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 communication includes: transmitting, by a first satellite, a setup request from a user equipment (UE) to a terrestrial core network element; configuring, by the first satellite, a sequence of second satellites of a 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 based on a setup configuration received from the terrestrial core network element, 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 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. The iterative updating includes 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 ​​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 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 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 camping of the UE 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 a 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 comprises 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 an adjacent second satellite in the sequence before a 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: - A 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 less than the first radius; -Core network elements located on the ground Equipped with The first satellite, in response to the setup request from the UE, sending a setup request to a ground-based core network element; configuring a sequence of second satellites of 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 based on a setup configuration received from the ground-based core network element, 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 a 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 by 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 figures. Dimensions of features shown in the figures have been selected for convenience and clarity of presentation and are not necessarily drawn to scale. The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to its construction 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 figures. The embodiments are illustrated, without limitation, in the drawings in which like reference numerals indicate corresponding, similar, or similar elements. [Brief description 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] FIG. 1 illustrates a system for communication according to some embodiments of the present invention. [Figure 3B] FIG. 1 illustrates a system for communication according to some embodiments of the present invention. [Figure 3C] FIG. 2 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. [Diagram 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 may be used with some embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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] An embodiment of the present invention uses a number of different satellites in a number of different orbits. Very Low Earth Orbit (VLEO) satellites, also referred to herein as Very Low Earth Orbit (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 at an altitude of 35,786 km above the Earth's equator and have an orbital period equal to the Earth's rotation period, and therefore appear to an observer on the ground as a stationary, fixed location.

[0025] For example, LEO satellites and / or GEO satellites orbit at a greater distance from the center of the Earth than VLEO / VLOS satellites, and therefore, 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] An example of the visibility period of a single LEO satellite orbiting at 600 km is shown in Figure 1. As can be seen, an 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 a user equipment (UE) such as a mobile phone on the planet's surface may allow data throughput in the 100 Mbit region, compared to the 0.1-1.5 Mbit throughput of user equipment communicating with a LEO satellite (depending on the antenna and scenario). However, a drawback of VLEO satellites is the increased speed due to their lower altitude, and therefore VLEO satellites do not remain in 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 high-speed train users and remain in range for only 2-5 minutes every 12 hours. So far, 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 the Earth, resulting in frequent and unavoidable handovers for both stationary and moving UEs. This can lead to large signaling overhead, impact power consumption, and exacerbate other potential challenges related to mobility, such as service interruptions due to signaling delays. ...From the above analysis, it can be concluded that the HO frequency in LEO NTNs may be similar to that experienced by terrestrial UEs on high-speed trains, but this represents a worst-case scenario and is not indicative of a typical terrestrial network. Frequent HO is not expected to occur in GEO due to the large cell size, which limits the impact of UE speed. Furthermore, in LEO scenarios, UE speed is assumed to be a negligible factor in HO frequency, considering the relative speed of the satellite, which is primarily an issue for LEO 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 (e.g., have a coverage area (not shown) that includes) the terrestrially located core network element 202 and can transmit and receive signals to and from the core network element 202. For example, satellite 230_3 can transmit and receive signals 220_3 to and from the core network element 202, satellite 230_4 can transmit and receive signals 220_4 to and from the core network element 202, and satellite 230_5 can transmit and receive signals 220_5 to and from the 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 time point for VLOS satellites 230_-1, 230_0, 230_1, 230_2, 230_3, 230_4, and 230_5 as they move over the Earth's surface 200 (in the figure, the satellite movement direction is shown as moving from left to right). Satellite 230_-2 was not "seen" (e.g., to an observer / user equipment proximate the location shown) at the time illustrated in FIG. 2A, and thus is "coming in" from the left, representing the periodic visibility of the satellite.

[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) such that at the time shown in Figure 2B it no longer includes user equipment 201. Satellite 230_-1 has moved such 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 transmit signals 220_2 to and receive signals 220_2 from core network element 202. Satellite 230_5 has moved out of range of core network element 202 and can no longer transmit signals to or receive signals from 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 satellites moving faster (which also increases Doppler), handover and connection stability become more problematic. For example, as shown between Figures 2A and 2B, satellite 230_0 needed to handover a 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 needed, which occurs more frequently due to the increased orbital speed due to being 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 aircraft 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, a multi-orbit constellation including interactions with existing LEO or GEO satellites is proposed by an embodiment of the present invention, which can increase capacity and throughput using a novel 3D (e.g., multi-orbit) network architecture and can be inherently part of the 6G system.

[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] The embodiment of the present invention solves the problem by placing the 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 as high a throughput. Thus, the embodiment of the present invention further includes a constellation of VLOS orbit satellites (e.g., 3D network) to provide connectivity organized by higher orbit satellites covering an area instantaneously. 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 is the next satellite to service and which satellite is needed in the connection for the backlink to Earth, and can therefore provide the respective information to said satellites. The low orbit satellites effectively only operate as data pumps, and the high orbit satellites handle the connection control and configuration, so that the low orbit satellites can only be used when the UE is operating in a connected mode (including discontinuous transmission "DTX" and on hold situations). 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 done to a limited level if there are more than SSBs (synchronization signal blocks) or CD-SSBs (cell defining SSBs). For example, low-earth orbit satellites can only provide SSB-CD so that the satellites can be identified with clear usage via ISLs (inter-satellite links) during satellite chain initialization (e.g. configuration from the first satellite).

[0045] Thus, because LEO satellites (or even satellites in higher orbits such as GEO satellites) move infrequently 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, NTN 4V2X from 5GAA: 5G Automotive Association) and can provide a robust architecture to maintain connectivity for use cases such as remote piloting, drone control, etc.

[0047] 3A and 3B show a system for communication according to some embodiments of the present invention. The system for communication includes a user equipment 301, a ground-based core network element 302, such as an Access and Mobility Management Function (AMF), a first satellite 303, and a number 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 being 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 the planet (e.g., Earth) above which the first satellite orbits. The radius R1 may be measured from the surface 300 of the planet (e.g., assuming a uniform surface). FIG. 3C illustrates 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 respective 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 shown 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 radii 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 the 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, to provide greater potential coverage, satellites from multiple MNOs can be (e.g., subject to an agreement) enlisted.

[0051] As shown in FIG. 3A, the first satellite 303 communicates (e.g., can send and receive signals) with each of the UE 301 and the core network element 302. For example, the first satellite 303 can send and receive signal 350 with the user equipment 301 and can send and receive 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 a setup request to the core network element 302 located on the ground. The UE performs access to the satellite 303 when said satellite performs all the necessary routines and emissions (SIB signaling) for it to be an anchor cell, i.e., the UE can camp on it and perform all authentication requests via the core network through said satellite. The VLOS satellite, also referred to here 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 said satellite). Since the second satellite 330_n may not be suitable for P-RACH setup, the first satellite 303 can also handle the initial UE P-RACH (physical random access channel) process, 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 multiple 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 can configure (e.g., by signals 360, not all of which are shown) second satellites 330_0, 330_1, 330_2, and 330_3 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 with signal 365 by the first satellite 303) 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 335 of the second satellite is adapted to provide a first user data connection between the UE 301 and the core network element 302. For example, a secondary user data plane within the meaning of 3GPP is created between the UE 301 and the core network element 302 via several satellite hops (e.g., a chain of connections) between the second satellites in the sequence 335. In case of a connection failure between the UE 301 and the serving satellite, the UE 301 can indicate to the first satellite 303 (e.g., via SRB1) that the secondary cell (e.g., the second satellite 330_0) is gone. The first satellite 303 can then compile a new sequence for the UE 301 and indicate to the 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 terrestrially located core network element 302 includes communication over 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 over ISLs (e.g., communication between 330_0 and 330_1, communication between 330_1 and 330_2, etc.) to provide a 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 over 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 the sequence 335, may be a non-anchor cell for the UE 301. A non-anchor cell according to 3GPP is a cell that does not provide the necessary system information (SIB) and is therefore not suitable for camping or initial access to be performed by the UE towards the core network, since it is only used in conjunction with a dedicated mode, i.e., included when the UE has an active data session. In some embodiments, the first satellite 303 is an anchor cell for the UE 301. For example, the 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 system information and paging are transmitted. Although the concept of anchor cell and non-anchor cell has existed in the past, particularly for NB-IoT carriers, in the context of the present invention, these terms apply to cells in general, e.g., 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, thereby avoiding 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 provide only PSS blocks (packet switched streaming) for connection maintenance, identification and measurement of balling indication. No general SIBs for neighboring cells / frequencies or service configuration may be provided. This information may be provided by the first satellite (e.g. LEO / GEO) and depending on UE requests and control considerations, the serving and so-called "drift" second drift satellites are configured to handle the user plane by the control network via the first satellite.

[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 a terrestrially located core network element to be included in the sequence if there is no second satellite currently in the sequence having a coverage area that includes a terrestrially located core network element.

[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 a serving satellite serving UE 301. As the satellites move over the Earth's surface 300, the situation in FIG. 3B (and as described for 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 be a new serving satellite serving UE 301. The first satellite 303 may do this prior to (e.g., during a predetermined time prior to) a serving satellite change; for example, the first satellite 303 may prepare (e.g., by configuration 362) satellite 330_-1 to take over as the serving satellite. Satellite 303_0 may have its status changed to removed serving satellite (e.g., by reconfiguration from the first satellite 303), and satellite 330_-1 would be considered part of the sequence 335 of the second satellite. Satellite 330_0 may remain in the sequence 335 as an intermediate satellite. Such a sequence update reflects a 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 away to have a coverage area that no longer includes the core network element 302 (e.g., no longer within range), and satellite 303_2 has moved far enough away to now have a coverage area that includes the core network element 302. Satellite 330_2 may be configured by the first satellite 303 to communicate (e.g., via signal 312) with the core network element 302. Alternatively, since satellite 330_2 was already included in the sequence 335, no further configuration by the first satellite 303 may be required. Satellite 303_4, if included, may be removed from the 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 for 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. The first satellite 303 may 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 when the satellite 330_-1 moves out of range of the UE 301.

[0063] As an example, the 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 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 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 may 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 and receive data to and from the UE 301 via such additional user data connection in the event that 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 invention, the serving satellite may be adapted to perform an inter-satellite Hybrid Automatic Repeat Request "HARQ" process. For example, the inter-satellite HARQ process may involve the transmission by the serving satellite of user data and information related to generating a HARQ redundancy version to a second adjacent satellite in the sequence before the serving satellite's coverage area does not include the UE. HARQ redundancy versions are a known feature of 3GPP where each transmission is self-decodable but also decodable in case of a reception error in the combination. Thus, some embodiments of the invention relate to a HARQ process performed between two satellites when handovers may occur very frequently, avoiding having to restart the HARQ process of the ongoing transmission from scratch at each handover. If the new serving satellite is aware of the ongoing HARQ process and the redundancy versions received or generated, it can maintain and complete the HARQ process in conjunction with the data received from the previous serving satellite.

[0070] As shown in Figures 3A and 3B, while the satellite 330_0 still has a coverage area 310_0 including the UE 301, before the satellite 330_0 moves so that the coverage area 310_0 no longer includes the UE 301, the serving satellite 330_0 can transmit data 342 related to the generation of the HARQ redundancy version to the satellite 330_-1. The serving satellite 330_0 can transmit such data 342 to the satellite 330_-1 since it is a neighboring satellite due to the satellite 330_-1 becoming the new serving satellite. Thus, the serving satellite can not only provide data to the user plane, but also transfer part of the user data to the next serving satellite in case of an error (e.g., retransmission for the user) depending on the remaining coverage time to complete the provision.

[0071] Although the latency is reduced to 10 ms, handovers and serving satellite changes are very frequent, i.e., less than a minute or even double-digit seconds for service, and seamless provision of data and HARQ processes across base stations / satellites is required. The HARQ process may include several retransmissions of different redundancy versions and therefore take some double-digit milliseconds. As a result, the number of uncompleted HARQ processes due to subsequent handovers may grow. Thus, resuming each interrupted process may cause delays, and therefore the inter-satellite HARQ process according to the embodiment of the present invention may have advantages. For such processes, the provision of relevant information about the data and HARQ process may enable increased throughput and more efficient data sessions.

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

[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 the core network element 302.

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

[0075] One embodiment of the present invention relates to a satellite adapted to act as a first satellite as described herein, such as first satellite 303. It will be appreciated that multiple satellites adapted to act as first satellites may be deployed to cover 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] Figure 4 illustrates an exemplary schematic diagram of a connection request setup according to some embodiments of the present invention. In Figure 4, a first satellite is a GEO / LEO satellite and a number of second satellites are VLOS satellites. Ground 402 represents a core network element located on the ground. Time can be considered to progress "downwards" in Figure 4.

[0078] 4, a UE 401 sends a setup request (step 451) to a GEO / LEO satellite 403. In addition to the UE capabilities (such as the frequency band to be used), the setup request may also include UE authentication data and thus drive 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] The GEO / LEO satellite 403 configures the serving VLOS of the VLOS satellite 430 (step 454) and configures the drift VLOS (e.g., updates the serving VLOS, if necessary) (step 455). For example, as shown in FIG 3A, the first satellite 303 may configure the second satellite 330_0 as the serving satellite and configure the second satellite 330_-1 as the drift satellite that will take over as the serving satellite from the second satellite 330_0 at a future point in time.

[0081] The VLOS satellites 430 establish inter-satellite links (ISLs) between themselves (step 456). For example, as shown in Figure 3A, the inter-satellite link 340 enables the second satellite in the sequence 335 to form a connection from the user equipment to the core network element 302. The configured VLOS satellite 430 sends a setup request to the 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 flow chart of a method 500 for communication according to some embodiments of the present invention. The method 500 may be implemented by a system such as that shown in FIGs. 3A and 3B.

[0084] The method 500 includes transmitting a setup request from a user equipment "UE" by a first satellite to a terrestrial core network element (step 510). For example, a UE (such as UE 301) may transmit a setup request to a first satellite (such as the first satellite 303, which may be a high-orbit satellite such as a LEO or GEO satellite), such as to set up an SRB1. 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 terrestrial core network element (such as the terrestrial core network element 303).

[0085] The method 500 includes configuring, by the 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 satellite 330_n illustrated in FIG. 3A-3C. Each satellite 330_n of the plurality of second satellites has a second orbit, each second orbit being 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 with the first satellite is based on a setup configuration received from a terrestrial core network element. Configuring the sequence of second satellites of the plurality of second satellites is according to a coverage area of ​​the sequence of second satellites and a 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 a coverage area (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 includes UE 301 and core network element 302 and enables 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 of FIG. 3A having an individual coverage area 310_0 that includes UE 301, and second satellite 330_-1 is the serving satellite of 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_0-330_3 as shown in Figure 3A and satellites 330_-1-330_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 to reach the ground station.

[0090] The method 500 may include providing a user data connection between the UE and a terrestrial core network element by the second sequence of satellites (step 530). For example, the second sequence of satellites may provide a user data connection having a function of 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, for example, via an inter-satellite link 340, the second satellite 330_1 communicating with the second satellite 330_2, for example, via an inter-satellite link 340, the second satellite 330_2 communicating with the second satellite 330_3, for example, 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 iteratively updating (step 540) the sequence of the second satellite based on the changing coverage area of ​​the sequence of the second satellite by the first satellite. The updating includes configuring the second satellite included in the sequence to become a new serving satellite when the coverage area of ​​the existing serving satellite no longer includes the UE. For example, as shown in Figures 3A and 3B, the sequence of the second satellite 335 is updated to take into account the changing coverage area of ​​the second satellite 330_0, which is the serving satellite of Figure 3A. The sequence 335 of 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 take over as the serving satellite by the first satellite 303 in a higher orbit, and thus in FIG. 3B, the 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 the core network element 302.

[0092] The updating may further include 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. For example, at the "tail" of the sequence, when 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 as 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 a serving satellite but is next in the sequence due to "drifting" its respective coverage area into the area of ​​coverage of a UE or core network element.

[0093] In the example shown in Figures 3A and 3B, the satellite movement direction is from left to right, so satellite 330_1 was already in the sequence 335 shown in Figure 3A and the sequence 335 shown in Figure 3B. However, if the satellite movement direction shown in Figures 3A and 3B were reversed (Figure 3A is at a later time than Figure 3B), it will be appreciated that the first satellite 303 would need to update the sequence 335 such that satellite 330_4 is added to the sequence 335 as satellite 330_3 moves out of range of the core network element 302 and as satellite 330_4 moves into range of the 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 location of the UE relative to the coverage areas 310_-1 and 310_0 of satellites 330_-1 and 330_0, respectively.

[0094] Figure 6 illustrates 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 the second satellite 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, a memory 120, a storage 130, an input device 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, for example, scheduling the execution of programs. The memory 120 may be or include, for example, a random access memory (RAM), a read only memory (ROM), a flash memory, a 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 a 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] The executable code 125 may be any application, program, process, task, or script. The executable code 125 may be executed by the controller 105, possibly under the control of the operating system 115. For example, the executable code 125 may be or execute one or more applications that implement the methods disclosed herein, such as the method 500 shown in FIG. 5. In some embodiments, multiple computing devices 100 or components of devices 100 may be used. One or more processors 105 may be configured to perform embodiments of the 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] The input devices 135 may be or include a mouse, a keyboard, a touch screen or pad, or any suitable input device or combination of devices. The input devices 135 may include a receiver, such as an antenna receiver. The output devices 140 may include one or more displays, speakers, and / or any other suitable output device or combination of output devices. The output devices 140 may include a transmitter, such as an antenna transmitter. Any applicable input / output (I / O) devices may be connected to the 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 in the input devices 135 and / or the output devices 140.

[0099] An embodiment of the invention may include one or more articles (e.g., memory 120 or storage 130), such as a computer or processor non-transitory readable medium, or a computer or processor non-transitory storage medium, such as a memory, disk drive, or USB flash memory, that encode, contain, or store instructions, such as computer-executable instructions, that when executed by 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 and low orbit satellites provides control and user plane separation that balances high data throughput and connection stability. The high orbit satellites provide core functions and orchestrate the low orbit satellites to provide the user data plane between the user equipment and the core network elements. The low orbit satellites effectively only operate as data pumps, while the high orbit satellites handle connection control and configuration, so that the low orbit satellites can only be used when the UE is operating in connected mode. Thus, the low 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 will be apparent from the foregoing description, throughout this specification, descriptions utilizing terms such as "processing," "calculating," "computing," "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 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, contain, 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 appreciated that embodiments of the present invention may solve one or more of the objectives and / or problems described in the background, and that embodiments of the present invention need not satisfy all of the above objectives and / or problems to fall within the scope of the present invention. While certain features of the present invention have been specifically illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It should therefore 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] Although 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, although 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. Although 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 the features of another embodiment or group of embodiments.

[0107] References in this specification to "some embodiments," "one embodiment," "one embodiment," or "other embodiments" mean that a particular feature, structure, or characteristic described in connection with the 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 are 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," "consisting," and grammatical variations thereof do not exclude the addition of one or more components, features, steps, or integers or groups thereof, and that these terms should be interpreted as specifying the components, 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 specification refers to "a" or "an" element, it should be understood that such a reference is not to be construed as referring to only one of the element.

[0113] When the specification states that a component, feature, structure, or characteristic "may include," "can 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 description, e.g., flow need not move through each box or state shown, or in the exact same order as shown and described.

Claims

1. 1. A method for communication, comprising: sending a setup request from a user equipment (301) to a ground-based core network element (302) by a first satellite (303); configuring, by the first satellite, a sequence (335) of a plurality 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, the sequence of second satellites including 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 included in the sequence as a new serving satellite if a 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 including 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 less than the first radius.

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

3. 2. The method of any preceding claim, 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 any preceding claim, comprising maintaining a further user data connection with the UE by the first satellite, and transmitting data via the further user data connection if the first user data connection is lost.

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

6. 10. A method according to any preceding claim, comprising preventing camping of the UE on the second sequence of satellites.

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

8. 2. 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. 10. A method according to any preceding claim, comprising performing, by the first satellite, non-access stratum signalling (NAS) with the UE.

10. 10. The method of any of the preceding claims, wherein providing the first user data connection between the UE and the ground-based 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. 2. A method according to any preceding claim, comprising monitoring, by the UE, the first satellite when the UE is in an idle mode.

13. 10. The method of any preceding claim, wherein at least two of the second plurality of 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 core network element (302); Equipped with The first satellite, in response to a setup request from the UE, sending the setup request to the terrestrial core network element; configuring 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 based on a setup configuration received from the terrestrial core network element, the sequence of second satellites including 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 is 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 a 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 according to any one of claims 1 to 13.

16. A satellite adapted to perform the role of the second satellite in the method according to any one of claims 1 to 13.

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