Methods and systems for improved non-terrestrial networks

Abstract

A satellite 520 equipped with a base station indicates 571, to user equipment (UE) 510 attempting to connect to the satellite, that the satellite supports both (i) direct transfer (DT) and (ii) store

Description

FIELD OF THE INVENTION

[0001] The invention relates generally to methods and systems for operating non-terrestrial satellites, in particular to operating both store and forward, and direct transfer modes of operation. BACKGROUND

[0002] It is a goal of the Third Generation partnership Project (3GPP) to enable direct 5G access via satellite. Already in Release 17, 3GPP has applied a phased approach to optimize 5G “direct access” integration for both basic legacy and advanced satellite systems.

[0003] The Release 17 solution uses a so-called “transparent” satellite system shown in Fig. 1 as system 100. A user equipment 110 communicating using 5G new radio (NR) sends data to a satellite 120, which transfers the data to a ground station 130 (e.g. by feeder link or by successive inter-satellite links). The ground station 130 is in communication with a gNB base station 140, which is connected to a 5G core network element 150.

[0004] The existing solution exhibits problems arising from the potential lack of availability of feeder links and inter-satellite resources.

[0005] Accordingly, there is a need in the art for systems and methods which address these problems. BRIEF SUMMARY OF THE INVENTION

[0006] According to one or more embodiments of the invention, there is provided a method for operating a satellite equipped with a base station, the method comprising: indicating, to a user equipment “UE” attempting to connect to the satellite, that the satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation; receiving, from the UE, a set of data comprising an indication of which mode of operation the satellite should use to transmit the set of data; and based on the mode of operation indicated by the UE, either: transmitting the set of data to one of: a second satellite; or a ground station; or storing the set of data in a data storage and transmitting the set of data to the ground station at a later point in time.

[0007] According to some embodiments, indicating that the satellite supports both direct transfer and S&F modes of operation comprises sending to the UE, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the satellite supports both direct transfer and S&F modes of operation.

[0008] According to some embodiments, the SIB comprises a system information element indicating a maximum data storage forwarding time.

[0009] According to some embodiments, the method includes indicating a momentary unavailability of one of the supported modes of operation.

[00010] According to some embodiments, indicating a momentary unavailability of the S&F mode of operation is based on a remaining data storage capacity of the satellite.

[00011] According to some embodiments, indicating a momentary unavailability of the S&F mode of operation is linked to a priority of the set of data, and wherein different indications for different data priorities are available.

[00012] According to some embodiments, indicating support for the S&F mode of operation comprises indicating one or more data priorities, wherein indicating by the UE to use S&F is subject to a subscription of the UE, and wherein for different data priorities usage of S&F for transmitting the set of data from the UE results in corresponding different costs.

[00013] According to some embodiments, indicating a momentary unavailability of the direct transfer mode of operation is based on an inter-satellite link “ISL” capacity shortage.

[00014] According to some embodiments, non-access stratum “NAS” data is always treated as direct transfer.

[00015] According to some embodiments, the NAS data comprises at least one of: authentication, identification, registration, security, or session management signalling.

[00016] According to some embodiments, the method includes selecting, by the satellite, to store the set of data and transmit the set of data to the ground station at the later point in time irrespective of the mode of operation indicated by the UE based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; or a remaining data storage capacity of the second satellite.

[00017] According to some embodiments, the method includes selecting, by the satellite, to transmit the set of data irrespective of the mode of operation indicated by the UE based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; or a remaining data storage capacity of the second satellite.

[00018] According to some embodiments, the method includes, if the remaining satellite data storage capacity reaches a first capacity value, then transmitting at least some of the data stored in the data storage to one of the second satellite or the ground station.

[00019] According to some embodiments, the method includes, once the remaining satellite data storage capacity reaches a second capacity value being less than the first capacity value, then stopping transmitting least some of the data stored in the data storage to the second satellite or the ground station.

[00020] According to one or more embodiments, there is provided a satellite equipped with a base station, the satellite configured to: indicate, to a user equipment “UE” attempting to connect to the satellite, that the satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation; receive, from the UE, a set of data comprising an indication of which mode of operation the satellite should use to transmit the set of data; and based on the mode of operation indicated by the UE, either: transmit the set of data to one of: a second satellite; or a ground station; or store the set of data in a data storage and transmit the set of data to the ground station at a later point in time.

[00021] According to some embodiments, the satellite is configured to send to the UE, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the satellite supports both direct transfer and S&F modes of operation.

[00022] According to some embodiments, the SIB comprises a system information element indicating a maximum data storage forwarding time.

[00023] According to some embodiments, the satellite is configured to indicate a momentary unavailability of one of the supported modes of operation.

[00024] According to some embodiments, the satellite is configured to indicate a momentary unavailability of the S&F mode of operation based on a remaining data storage capacity of the satellite.

[00025] According to some embodiments, the satellite is configured to indicate a momentary unavailability of the S&F mode of operation linked to a priority of the set of data, and wherein different indications for different data priorities are available.

[00026] According to some embodiments, indicating support for the S&F mode of operation comprises indicating one or more data priorities, wherein receiving an indication from the UE to use S&F is subject to a subscription of the UE, and wherein for different data priorities usage of S&F for transmitting the set of data from the UE results in corresponding different costs.

[00027] According to some embodiments, the satellite is configured to indicate a momentary unavailability of the direct transfer mode of operation based on an inter-satellite link “ISL” capacity shortage.

[00028] According to some embodiments, the satellite is configured to always transmit non-access stratum “NAS” data by direct transfer.

[00029] According to some embodiments, the NAS data comprises at least one of: authentication, identification, registration, security, or session management signalling.

[00030] According to some embodiments, the satellite is configured to select to store the set of data and transmit the set of data to the ground station at the later point in time irrespective of the mode of operation indicated by the UE based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; or a remaining data storage capacity of the second satellite.

[00031] According to some embodiments, the satellite is configured to select to directly transmit the set of data irrespective of the mode of operation indicated by the UE based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; or a remaining data storage capacity of the second satellite.

[00032] According to some embodiments, the satellite is configured to, if the remaining satellite data storage capacity reaches a first capacity value, then transmit at least some of the data stored in the data storage to one of the second satellite or the ground station.

[00033] According to some embodiments, the satellite is configured to, once the remaining satellite data storage capacity reaches a second capacity value being less than the first capacity value, then stop transmitting least some of the data stored in the data storage to the second satellite or the ground station.

[00034] According to one or more embodiments, there is provided a system comprising: a first satellite; a user equipment “UE”; a second satellite; and a ground station, wherein the UE is configured to attempt to connect to the first satellite, wherein the first satellite is configured to: indicate, to the UE, that the first satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation; receive, from the UE, a set of data comprising an indication of which mode of operation the first satellite should use to transmit the set of data; and based on the mode of operation indicated by the UE, either: transmit the set of data to one of: the second satellite; or the ground station; or store the set of data and transmit the set of data to the ground station at a later point in time.

[00035] According to some embodiments, the system is configured to carry out one or more methods disclosed herein.

[00036] According to one or more embodiments, there is provided a method for operating a user equipment “UE”, the method comprising: attempting to connect to a first satellite; receiving, from the first satellite, an indication that the first satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation; and sending, to the first satellite, a set of data comprising an indication of which mode of operation the first satellite should use to transmit the set of data.

[00037] According to some embodiments, receiving the indication that the first satellite supports both direct transfer and S&F modes of operation comprises receiving, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the first satellite supports both direct transfer and S&F modes of operation.

[00038] According to some embodiments, the SIB comprises a system information element indicating a maximum data storage forwarding time.

[00039] According to one or more embodiments, there is provided a user equipment “UE” configured to perform one or more methods disclosed herein.

[00040] According to some embodiments, the UE is configured, by virtue of a subscription, to only indicate the S&F mode of operation, but to be able to indicate the direct transfer mode of operation for any abnormal data, emergency data or exceptional data. BRIEF DESCRIPTION OF THE DRAWINGS

[00041] Non-limiting examples of embodiments of the disclosure are described below with reference to figures attached hereto. Dimensions of features shown in the figures are chosen for convenience and clarity of presentation and are not necessarily shown to scale. The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may be understood by reference to the following detailed description when read with the accompanied drawings. Embodiments are illustrated without limitation in the figures, in which like reference numerals indicate corresponding, analogous, or similar elements, and in which:

[00042] Fig. 1 shows a transparent satellite system;

[00043] Fig. 2 shows a regenerative satellite system;

[00044] Fig. 3 shows how successive use of inter-satellite link resources can result in data accumulation;

[00045] Fig. 4 shows a flowchart of a method for operating a satellite equipped with a base station, according to some embodiments of the invention;

[00046] Fig. 5A shows an example of direct transfer, according to some embodiments of the invention;

[00047] Fig. 5B shows an example of store and forward, according to some embodiments of the invention;

[00048] Fig. 6 shows a block diagram of an exemplary computing device 600 which may be used with some embodiments of the present invention;

[00049] Fig. 7 shows a block diagram of an exemplary user equipment which may be used with embodiments of the present invention;

[00050] Fig. 8 shows a block diagram of an exemplary base station which may be used with embodiments of the present invention; and

[00051] Fig. 9 shows a block diagram of an exemplary satellite which may be used with embodiments of the present invention.

[00052] 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 of the 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 or analogous elements. DETAILED DESCRIPTION

[00053] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention can 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 invention.

[00054] Fig. 2 shows a regenerative satellite system 200. Comparison should be made to Fig. 1. In system 200, a user equipment (UE) 210 communicating using 5G new radio (NR) sends data to a satellite 220, which transfers the data to a ground station 230 (e.g. by feeder link or by successive inter-satellite links). The ground station 230 is in communication with a 5G core network element 250. A difference from Fig. 1 is that the gNB base station is located in the satellite, e.g. in satellite 220. That the satellite includes a base station, such as gNB, allows the satellite to not only directly transfer data from UE 210 (e.g. to ground station 230), but also to amplify, remodulate, or demodulate the data. Furthermore, the satellite can store the data for later forwarding, for example due to changes in relative position between satellite 220 and ground station 230.

[00055] Store and forward (herein referred to as S&F) may be advantageous where the satellite has moved out of connection with a ground station since data from a UE was transmitted to the satellite. Furthermore, continuous use of inter-satellite links can result in traffic accumulation, putting a burden on the last satellite in the “chain”, as seen in Fig. 3.

[00056] Fig. 3 shows how successive use of inter-satellite link resources can result in data accumulation, which is a problem in the art. Satellite 320-1, having a coverage area / footprint 322-1 receives data 324-1 from one or more user equipments within coverage area / footprint 322-1, such as user equipment 310-3. Satellite 320-1 may directly transfer this data to satellite 320-2 via intersatellite link 326-1. Satellite 320-2 may receive data 324-2 from one or more user equipments in its own coverage area 322-2, such as from UEs 310-5 and 310-6. Satellite 320-2 may directly transfer this data to satellite 320-3 via intersatellite link (ISL) 326-2, however satellite 320-2 not only needs to transfer data 324-2 received from UEs in its own coverage area, but also the data 324-1 received from satellite 320-1 via ISL 326-1. Accordingly, the data that satellite 320-2 may transfer to satellite 320-3 via ISL 326-2 may be larger (e.g. of a greater total size in units such as MB, GB, etc.) than the data transferred via ISL 326-1.

[00057] These data size increases accumulate following successive ISLs, represented in Fig. 3 as a thickening of the arrows in the ISL. For example, ISL 326-5 between satellites 320-5 and 320-6 is thicker than ISL 326-4 between satellites 320-4 and 320-5, which is thicker than ISL 326-3 between satellites 320-3 and 320-4.

[00058] In Fig. 3, the “chain” of ISLs ends with satellite 320-7, which receives data via ISL 326-6 from satellite 320-6 (e.g. being the thickest ISL representing accumulated data from satellites 320-1, 320-2, 320-3, 320-4, 320-5 and 320-6). Satellite 320-7 also receives data 324-7 from UEs in its coverage area. Satellite 320-7 is within range of ground station 330. Accordingly, satellite 320-7 can directly transfer all of the accumulated data via feeder link 328-7 between satellite 320-7 and ground station 330.

[00059] As can be seen, the data transfer burden on satellite 320-7 is greater than the data transfer burden of satellite 320-1. The Inventors have identified that not all data needs to be directly transferred, for example some data may be delay tolerant, and could be received by satellite 320-1 and stored for later forwarding when satellite 320-1 is within range of a ground station, thereby conserving ISL resources and extending the operational lifetime of the satellites in the nonterrestrial network.

[00060] Fig. 4 shows a flowchart of a method 400 for operating a satellite equipped with a base station, according to some embodiments of the invention. The satellite could be a satellite as discussed herein with respect to Fig. 9. The satellite could be equipped with a base station such as discussed herein with respect to Fig. 8. The base station could be, for example, a gNB.

[00061] Method 400 may include a Step 420 of indicating, to a user equipment “UE” attempting to connect to the satellite, that the satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation.

[00062] The UE could be a UE as described herein with respect to Fig. 7.

[00063] The indication that the satellite supports both direct transfer and S&F modes of operation may be made via a system broadcast channel, for example by sending a broadcast message such as a system information block (SIB) to the UE.

[00064] For example, in method 400, indicating that the satellite supports both direct transfer and S&F modes of operation may include sending to the UE, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the satellite supports both direct transfer and S&F modes of operation.

[00065] The SIB may include a system information element indicating a maximum data storage forwarding time. For example, the maximum data storage forwarding time may be indicated as a duration in seconds, minutes, hours, or any other suitable measure of time. The maximum data storage forwarding time may be indicated as a clock time, such as a difference from coordinated universal time (UTC), e.g. UTC+00:00, UTC+01:00, UTC-04:00 or the like. The maximum data storage forwarding time may represent an anticipated (e.g. predicted) time before the satellite is able to forward data to a ground station. Relativistic effects due to the orbit of the satellite may be taken into account in indicating a maximum data storage forwarding time. The time may be a maximum time, for example, transfer may occur before expiry or elapse of the indicated data storage forwarding time.

[00066] Method 400 may include a Step 440 of receiving, from the UE, a set of data comprising an indication of which mode of operation the satellite should use to transmit the set of data. For example, the set of data may be communication data, such as 5G communication data, which the UE wishes to be transmitted over the network (e.g. NTN network). The UE may send as part of the data an indication of which mode of operation (e.g. direct transfer or S&F) the satellite should use to transmit the data. For example, the UE could indicate that the data should be transmitted directly, or the UE could indicate that the data should be transmitted using S&F. Different indications for different parts of the set of data may be given. For example a first part of the data could be indicated for transmission by S&F, and a second part of the data could be indicated for transmission by direct transfer. Different indications may be given for different types of data, as will be discussed further herein.

[00067] Method 400 may include a Step 460 of, based on the mode of operation indicated by the UE, either: (a) transmitting the set of data to one of: a second satellite; or a ground station; or (b) storing the set of data in a data storage and transmitting the set of data to the ground station at a later point in time.

[00068] The second satellite may be a satellite in a same NTN as the satellite receiving the indication from the UE. The second satellite may be a satellite as discussed with respect to Fig. 9 herein.

[00069] The ground station may be, may include, or may otherwise be in communication with, a network element such as a base station (e.g. gNB or eNB) or core network element (e.g. 5GC, EPC) located on Earth (e.g. as opposed to in orbit with the satellite). The satellite may communicate with the ground station via a feeder link.

[00070] The data storage may be a storage such as storage 630 described in Fig. 6.

[00071] The later point in time may be, may be based on, or may be otherwise related to, the maximum data storage forwarding time discussed herein.

[00072] According to some embodiments, the method may include indicating a momentary unavailability of one of the supported modes of operation. For example, the satellite may indicate to the UE that one of the supported modes of operation is temporarily unavailable. The indication may include an expected (e.g. predicted) downtime and / or resumption time. The downtime may be a period in minutes, hours, or any other suitable measure of time. The resumption time may be, or may be based on, a UTC time as discussed herein.

[00073] Momentary unavailability of one of the supported modes of operation may occur for several reasons. For example, indicating a momentary unavailability of the S&F mode of operation may be based on a remaining data storage capacity of the satellite. For example, circumstances may arise where the satellite runs out of data storage capacity, and thus can no longer commit to sending data by S&F. The amount of stored data may be reduced (and thus storage capacity freed up) following successful transfer of stored data to another satellite (such as the second satellite) or to a ground station. Following such an “offload” of stored data, the need for momentary unavailability of S&F may end, and the satellite may resume broadcasting an indication that S&F is supported.

[00074] During a momentary unavailability of S&F, the satellite may indicate that only direct transfer can be used. Due to the resources involved with direct transfer, this may result in higher costs (such as fees) for the user equipment.

[00075] According to some embodiments, indicating support for direct transfer is based on a priority of the data from the UE. For example, data which is delay tolerant may be classed as low-priority, and may be ineligible for direct transfer. As another example, non-access stratum (NAS) data such as data comprising or relating to at least one of authentication, identification, registration, security and / or session management signalling may be classed as high priority. High priority data may always be sent by direct transfer. High priority data may be sent as direct transfer irrespective of the UE indicating that such data should be sent by S&F, e.g. the satellite may overrule an indication from the UE.

[00076] Other data which may be classed as high priority data may include data which is not delay tolerant, such as real-time data, for example voice call data. Real-time may correspond to an event to system response on the order of milliseconds or microseconds. Humans typically expect to hold a phone conversation in real time, e.g. on the order of seconds, with minimal delays between speakers. NAS data may be considered as non-delay tolerant, e.g. as high priority data. Abnormal data, emergency data or exceptional data may be classed as high priority data, e.g. non-delay tolerant. As will be known to the skilled person, exceptional data is a technical term coming from the field of Internet of Things (loT), relating to devices with no voice to indicate their emergency call: in general any data / reporting which is beyond normal and planned / intended activity e.g. malfunction.

[00077] According to some embodiments, the ability of the UE to indicate a particular mode of operation to the satellite for sending the data is subject to a subscription of the UE. Sending of different data priorities may be associated with different costs. For example indicating to send low-priority data by direct transfer may attract a higher cost to the UE than indicating to send low-priority data by S&F. Based on the subscription of the UE, the UE may be unable to indicate certain modes of transmission for certain data priorities. Accordingly, in some embodiments, indicating support for the S&F mode of operation includes indicating one or more data priorities, wherein indicating by the UE to use S&F is subject to a subscription of the UE, and wherein for different data priorities usage of S&F for transmitting the set of data from the UE results in corresponding different costs.

[00078] In some embodiments, an indication of one or more data priorities is included in the broadcasted SIB information. There may be separate barring indications to separate data priorities. For example, the satellite may indicate momentary unavailability of S&F for a first data priority class, but indicate availability of S&F for a second data priority class different from the first data priority class. Accordingly, in some embodiments, indicating a momentary unavailability of the S&F mode of operation is linked to a priority of the set of data, wherein different indications for different data priorities are available.

[00079] In some embodiments, where S&F memory is nearly full (e.g. where the amount of data stored in the data storage is reaching a maximum capacity of the data storage) only emergency or exceptional data may be accepted and stored by the satellite, but normal or low priority data may be rejected for storage. For economic reasons “rejection” may happen prior to sending of the data (e.g. the UE does not send the data). Accordingly, the indication by the satellite, e.g. over a broadcast channel (BCH) may indicate that S&F is entirely unavailable, or may provide further differentiations in that S&F availability may be according to data priority. The satellite may indicate that emergency data is always transported even if some other data from other users would need to be deleted from storage in case of S&F.

[00080] In some embodiments, the method may include indicating (e.g. by the satellite) a momentary unavailability of the direct transfer mode of operation based on an inter-satellite link “ISL” capacity shortage. For example, if the satellite is not within range of a second satellite in order to establish an ISL, or if the satellite has already accumulated a substantial amount of data to send by ISL, the satellite may indicate that direct transfer is temporarily suspended. During such momentary unavailability of direct transfer, the satellite may indicate that only S&F can be used. Due to the resources involved with S&F, for example as relating to different data priorities, this may result in differing costs (such as fees) for the user equipment depending on the data. For example, it may cost more (e.g. in terms of a storage premium) for the satellite to store an image taken by a UE such as a smartphone (e.g. photos taken by smartphones typically being around 2MB in size) compared to storing an SMS short message service message (e.g. typically being around 140 bytes in size).

[00081] According to some embodiments, the method includes always treating non-access stratum (NAS) data as to be sent by direct transfer. NAS data may include, for example, data comprising or relating to at least one of: authentication, identification, registration, security and / or session management signalling.

[00082] Depending on different circumstances, the satellite may be unable to commit to or honour a particular mode of transmission indicated by the UE. For example the satellite may have lost connection with a nearby satellite or ground station, and is therefore unable to directly transfer data. As another example, a data storage capacity of the satellite, or second satellite, may be insufficient to support received sets of data. In these circumstances, the satellite (e.g. the base station on the satellite) may “overrule” the indication received from the UE.

[00083] In some embodiments, the method may include selecting, by the satellite, to store the set of data and transmit the set of data to the ground station at the later point in time irrespective of the mode of operation indicated by the UE based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; and / or a remaining data storage capacity of the second satellite.

[00084] Similarly, in some embodiments, the method may include selecting, by the satellite, to transmit (e.g. by direct transfer) the set of data irrespective of the mode of operation indicated by the UE based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; and / or a remaining data storage capacity of the second satellite.

[00085] In particular, in some embodiments, if the remaining satellite data storage capacity reaches a first capacity value, then the method includes transmitting at least some of the data stored in the data storage to one of the second satellite or the ground station. In this way, the satellite may “offload” some of the stored data, freeing up available data storage space. Once the remaining satellite data storage capacity reaches a second capacity value being less than the first capacity value, then the method may include stopping transmitting least some of the data stored in the data storage to the second satellite or the ground station. For example, once the data storage has fallen back below a predefined value, the satellite may stop “offloading” data, and may resume S&F operation. An indication of the availability or lack thereof of S&F, such as an indication of the availability or unavailability of S&F for certain data priority classes, may be updated or otherwise changed.

[00086] Figs. 5A and 5B show a summary of methods according to embodiments of the invention.

[00087] Fig. 5A shows an example of direct transfer, according to some embodiments of the invention. A satellite 520 indicates to a UE 510 (e.g. as part of a SIB over a BCH) an indication 561 that direct transfer (DT) and Store and Forward (S&F) modes of operation are available. The satellite may also indicate a time t, which may represent a maximum data storage forwarding time. For example t may be 3 hours. UE 510 may send to satellite 520 a set of data, {DATA}, and an indication to transmit the data using DT, shown with reference numeral 562. Satellite 520 may then directly transfer (563) the data to another satellite via ISL or to a ground station. Here, Fig. 5A shows satellite 520 as directly transferring the data to a ground station 530 (e.g. via a feeder link), it will be understood that if satellite 520 is not within range of ground station 530, satellite 520 may transfer the data via ISL to another satellite within range of ground station 530, or via a chain of satellites and ISLs to a satellite which is within range of ground station 530 (not shown).

[00088] Fig. 5B shows an example of store and forward, according to some embodiments of the invention. A satellite 520 indicates to a UE 510 (e.g. as part of a SIB over a BCH) an indication 571 that direct transfer (DT) and Store and Forward (S&F) modes of operation are available. The satellite may also indicate a time t, which may represent a maximum data storage forwarding time. For example t may be 3 hours. UE 510 may send to satellite 520 a set of data, {DATA}, such as delay tolerant data, and an indication to transmit the data using S&F, shown with reference numeral 572. Satellite 520 may then store (573) the data to in a data storage 525 on the satellite. At a later point in time, e.g. after t = 3 hours, satellite 520 may retrieve (574) the data from data storage 525 for forwarding (575) to a ground station 530 (e.g. via a feeder link). It will be understood that during time t = 3 hours satellite 520 will have moved within range of ground station 530.

[00089] According to one or more embodiments of the invention, there is provided a satellite equipped with a base station and configured to perform one or more steps of one or more methods described herein, such as method 400. The satellite may be as described with respect to Fig. 9 herein.

[00090] For example, according to some embodiments, there is provided a satellite equipped with abase station, the satellite configured to: indicate, to a user equipment “UE” attempting to connect to the satellite, that the satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation; receive, from the UE, a set of data comprising an indication of which mode of operation the satellite should use to transmit the set of data; and based on the mode of operation indicated by the UE, either: (a) transmit the set of data to one of: a second satellite; or a ground station; or (b) store the set of data in a data storage and transmit the set of data to the ground station at a later point in time.

[00091] The base station may be, for example, a g node B (gNB).

[00092] In some embodiments, the satellite is configured to send to the UE, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the satellite supports both direct transfer and S&F modes of operation, as discussed herein. The SIB may comprise a system information element indicating a maximum data storage forwarding time, as discussed herein.

[00093] According to some embodiments, the satellite is configured to indicate a momentary unavailability of one of the supported modes of operation, as discussed herein. For example, the satellite may be configured to indicate a momentary unavailability of the S&F mode of operation based on a remaining data storage capacity of the satellite.

[00094] In some embodiments, the satellite is configured to indicate a momentary unavailability of the S&F mode of operation linked to (e.g. based on) a priority of the set of data, and wherein different indications for different data priorities are available (e.g. the satellite is configured to provide different indications for different data priorities), as discussed herein. For example, the satellite may be configured to indicate one or more data priorities, wherein receiving an indication from the UE to use S&F is subject to a subscription of the UE, and wherein for different data priorities usage of S&F for transmitting the set of data from the UE results in corresponding different costs, as discussed herein.

[00095] In some embodiments, the satellite may be configured to indicate a momentary unavailability of the direct transfer mode of operation based on an inter-satellite link “ISL” capacity shortage.

[00096] The satellite may be configured to always transmit non-access stratum “NAS” data by direct transfer. NAS data may include or relate to at least one of: authentication, identification, registration, security, and / or session management signalling, as discussed herein.

[00097] According to some embodiments, the satellite may be configured to select to store the set of data and transmit the set of data to the ground station at the later point in time irrespective of the mode of operation indicated by the UE, as discussed herein, based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; and / or a remaining data storage capacity of the second satellite.

[00098] Similarly, in some embodiments, the satellite may be configured to select to directly transmit the set of data irrespective of the mode of operation indicated by the UE based on at least one of: a delay tolerance of the set of data; a security level of the set of data; an emergency level of the set of data; a location of the UE; a location of the satellite; a location of the second satellite; a location of the ground station; an accumulated size of data to be sent to the second satellite; a remaining data storage capacity of the satellite; and / or a remaining data storage capacity of the second satellite, as discussed herein.

[00099] In some embodiments, if the remaining satellite data storage capacity reaches a first capacity value, then the satellite is configured to transmit at least some of the data stored in the data storage to one of the second satellite or the ground station. As discussed herein, once the remaining satellite data storage capacity reaches a second capacity value being less than the first capacity value, then the satellite may be configured to stop transmitting least some of the data stored in the data storage to the second satellite or the ground station. [000100] According to one or more embodiments of the invention, there is provided a system for carrying out one or more steps of one or more methods of the invention described herein, such as method 400. For example, a system according to embodiments of the invention may include: a first satellite (such as described herein); a user equipment “UE”; a second satellite; and a ground station. The UE may be configured to attempt to connect to the first satellite. The first satellite may be configured to: indicate, to the UE, that the first satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation, as described herein. The first satellite may be configured to receive, from the UE, a set of data comprising an indication of which mode of operation the first satellite should use to transmit the set of data, and based on the mode of operation indicated by the UE, either: (a) transmit the set of data to one of: the second satellite; or the ground station; or (b) store the set of data (e.g. in a data storage of the first satellite) and transmit the set of data to the ground station at a later point in time. [000101] According to one or more embodiments of the invention, there is also provided a method for operating a user equipment “UE”. The method may include: attempting to connect to a first satellite; receiving, from the first satellite, an indication that the first satellite supports both: (i) direct transfer; and (ii) store and forward “S&F” modes of operation; and sending, to the first satellite, a set of data comprising an indication of which mode of operation the first satellite should use to transmit the set of data. The satellite may decode or otherwise process the indication from the UE as described herein. For example, if the UE indicates to transmit the data by direct transfer, the satellite may proceed as described in Fig. 5A. If the UE indicates to transmit the data by S&F, the satellite may proceed as described in Fig. 5B. [000102] Receiving an indication that the first satellite supports both direct transfer and S&F modes of operation may include receiving, by the UE over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the first satellite supports both direct transfer and S&F modes of operation. As described herein, the SIB may include a system information element indicating a maximum data storage forwarding time. [000103] According to one or more embodiments of the invention, a user equipment is provided, the user equipment configured to perform one or more steps of one or more methods described herein. [000104] A user equipment according to one or more embodiments of the invention may be configured, e.g. by virtue of a subscription, to only indicate the S&F mode of operation, but to be able to indicate the direct transfer mode of operation for any abnormal data, emergency data or exceptional data. The subscription may link different data priorities to different costs, as discussed herein. Indications from the satellite may be linked to different data priorities. The UE may use a maximum data storage forwarding time indicated by the satellite to determine if the data the UE wishes to send is delay tolerant to the extent that transmission only after the elapsed maximum data storage forwarding time is acceptable. It will be understood that in a “chain” of satellites which can communicate via intersatellite link, the role of a satellite and second satellite as discussed herein can be interchanged depending on, for example, the relative positions of the satellites and / or the direction of flow of information to / from the satellites. [000105] As used herein, reference to an action or step taken by a satellite may relate to said action or said step being performed by a base station on that satellite. [000106] Fig. 6 shows a block diagram of an exemplary computing device 600 which may be used with some embodiments of the present invention. [000107] As described herein, any of: a user equipment; a core network element; a satellite; and / or a base station may be, or may include elements of, a computing device 600 as shown in Fig. 6. [000108] Computing device 600 may include a controller or computer processor 605 that may be, for example, a central processing unit processor (CPU), a chip or any suitable computing device, an operating system 615, a memory 620, a storage 630, input devices 635 and output devices 640 such as a computer display or monitor displaying for example a computer desktop system. [000109] Operating system 615 may be or may include code to perform tasks involving coordination, scheduling, arbitration, or managing operation of computing device 600, for example, scheduling execution of programs. Memory 620 may be or may include, for example, a Random Access Memory (RAM), a read only memory (ROM), a Flash memory, a volatile or nonvolatile memory, or other suitable memory units or storage units. At least a portion of Memory 620 may include data storage housed online on the cloud. Memory 620 may be or may include a plurality of different memory units. Memory 620 may store for example, instructions (e.g., code 625) to carry out a method as disclosed herein, such as method 400. Memory 620 may use a datastore, such as a database. [000110] Executable code 625 may be any application, program, process, task, or script. Executable code 625 may be executed by controller 605 possibly under control of operating system 615. For example, executable code 625 may be, or may execute, one or more applications performing methods as disclosed herein, such as method 400. In some embodiments, more than one computing device 600 or components of device 600 may be used. One or more processor(s) 605 may be configured to carry out embodiments of the present invention by, for example, executing software or code. [000111] Storage 630 may be or may 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 a storage 630 and may be loaded from storage 630 into a memory 620 where it may be processed by controller 605. Storage 630 may include cloud storage. Storage 630 may include storing data in a database. [000112] Storage 630 may store, for example, an MNC, MCC, TIMSI, secret value, UE capability information, or other data where storage 630 is included in, or is part of, a user equipment. [000113] Where storage 630 is included in or as part of a satellite as described herein, storage 630 may store data received from one or more UEs, or data received from one or more other satellites. [000114] Input devices 635 may be or may include a mouse, a keyboard, a touch screen or pad or any suitable input device or combination of devices. Input devices 635 may include a receiver, such as an antenna receiver. Output devices 640 may include one or more displays, speakers and / or any other suitable output devices or combination of output devices. Output devices 640 may include a transmitter, such as an antenna transmitter. Any applicable input / output (I / O) devices may be connected to computing device 600, for example, a wired or wireless network interface card (NIC), a modem, printer, a universal serial bus (USB) device or external hard drive may be included in input devices 635 and / or output devices 640. [000115] Embodiments of the invention may include one or more article(s) (e.g., memory 620 or storage 630) such as a computer or processor non-transitory readable medium, or a computer or processor non-transitory storage medium, such as for example a memory, a disk drive, or a USB flash memory encoding, including, or storing instructions, e.g., computer-executable instructions, which, when executed by a processor or controller, carry out methods disclosed herein. [000116] Reference is now made to Fig. 7, which is a block diagram of an exemplary user equipment (UE) 700 which may be used with embodiments of the present invention. [000117] UE 700 may include a radio interface 705. Radio interface 705 may include an antenna, a transceiver and / or any other suitable component to allow communication between UE 700 and a telecommunications network. [000118] UE 700 may include a user identity module 710. User identity module 710 may store user-specific information such as the International Mobile Subscriber Identity (IMSI) and may be used for authentication and authorization on the telecommunications network. [000119] UE 700 may include a mobile equipment 715. Mobile equipment 715 may include a processor, a memory, a display, and a user interface. [000120] UE 700 may include a battery 720. Battery 720 may provide power to UE 700, allowing it to operate without being connected to an external power source. [000121] UE 700 may include an operating system 725. Operating system 725 may manage UE’s 700 resources and / or provide a platform for running applications. [000122] UE 700 may include application software 730. Application software 730 may be user-installed and system applications that run on UE 700, providing UE 700 various functionalities. [000123] UE 700 may include a user interface 735. UE 735 may include a touchscreen, buttons, display and / or any other suitable components through which users may interact with UE 700. [000124] UE 700 may include sensors 740. Sensors 740 may include accelerometers, gyroscopes, GPS, and ambient light sensors, cameras and / or any other suitable sensors known in the art. Sensors 740 may allow features such as orientation detection, location-based services, and any other suitable features known in the art. [000125] UE 700 may include connectivity module 745. Connectivity model 745 may support various connectivity options, including cellular networks (e.g., 4G / LTE, 5G), Wi-Fi, Bluetooth, and NFC (Near Field Communication), allowing UE 700 to connect to other devices and telecommunications networks. [000126] UE 700 may include security components 750. Security components 750 may be responsible for ensuring the security and privacy of user data and communications. Security components 750 may include encryption / decryption hardware and software, as well as security features to protect against malware and unauthorized access. [000127] UE 700 may include a memory 755 (e.g., RAM) for running applications. UE 700 may include a storage 760 (e.g., internal storage or removable SD cards) and storage (e.g., internal storage or removable SD cards) for storing data and applications. [000128] UE 700 may include a charging port 765 for recharging battery 720. [000129] In some embodiments, some of the components shown in Fig. 7 may be omitted. In some embodiments, UE 700 may include additional components in accordance with standards specifications (e.g., 3GPP specifications) that are not shown in Fig. 7. [000130] Reference is now made to Fig. 8, which is a block diagram of an exemplary base station (BS) 800 which may be used with embodiments of the present invention. Base station 800 may be, for example, a gNB. [000131] BS 800 may include a radio transceiver 805. Radio transceiver 805 may transmit and receive radio signals. [000132] BS 800 may include an antenna system 810. Antenna system 810 may include one or more antennas that may transmit and receive signals via the air in specific directions and patterns. For example, antenna system 810 may include advanced antenna technologies such as Multiple-Input Multiple-Output (MIMO) and beamforming that may improve network performance and coverage. [000133] BS 800 may include baseband processing unit 815. Baseband processing unit 815 may handle the baseband processing of communication signals. Baseband processing unit 815 may perform tasks such as modulation / demodulation, encoding / decoding, error correction, and channel allocation. [000134] BS 800 may include a digital signal processing unit 820. Digital signal processing unit 820 may process and manipulate digital signals within baseband processing unit 815. Digital signal processing unit 820 may perform tasks such as signal processing, beamforming, interference cancellation, and MIMO processing. [000135] BS 800 may include a backhaul connection 825. Backhaul connection 825 may provide a high-capacity backhaul connection to connect BS 800 to the core network. Backhaul connection 825 may include wired connections such as optical fibre or microwave links. [000136] BS 800 may include a power supply unit 830. Power supply unit 830 may provide electrical power to BS’s 800 components to ensure continuous operation. [000137] BS 800 may include a control and management unit 835. Control and management unit 835 may be responsible for controlling and managing the operation of BS 800. Control and management unit 835 may handle tasks such as network configuration, software updates, and fault management. [000138] BS 800 may include a cooling system 840. Cooling system 840 may include fans, heat sinks, and / or liquid cooling systems that may maintain the equipment of BS 800 within its operating temperature range. [000139] BS 800 may include a timing and synchronization unit 845. Timing and synchronization unit 845 may perform timing and synchronization for maintaining the integrity of the communication network, e.g., to ensure that all base stations in the network are synchronized with a common timing reference. [000140] BS 800 may include a security and encryption unit 850. Security and encryption unit 850 may perform tasks such as encryption of user data and authentication of UEs for protecting the network from unauthorized access and malicious attacks. [000141] BS 800 may include a fault detection and alarming unit 855. Fault detection and alarming unit 855 may monitoring equipment health and raising alarms in case of hardware or software issues are critical for maintaining network reliability and availability. [000142] In some embodiments, some of the components shown in Fig. 8 may be omitted. In some embodiments, BS 800 may include additional components in accordance with standards specifications (e.g., 3GPP specifications) that are not shown in Fig. 8. [000143] Reference is now made to Fig. 9, which is a block diagram of an exemplary satellite 900 which may be used with embodiments of the present invention. [000144] Satellite 900 may include transponders 905. Transponders 905 may receive signals from base stations and / or user equipment. Transponders 905 may transmit signals to base stations and / or user equipment. Transponders 905 may be configured for different frequency bands and services. Transponders 905 may include modulation and demodulation equipment to encode and decode the transmitted data. Satellite 900 may include antennas 910 for receiving and transmitting signals. [000145] Satellite 900 may include a command and control system 915. Command and control system 915 may maintain satellite 900’s orbital position, attitude, and health. Command and control system 915 may handle adjustments to the satellite's 900 transponders 905, power levels, and other settings. [000146] Satellite 900 may include a processing unit 920. Processing unit 920 may manage communication protocols, routing of signals, process and relay data efficiently between the uplink and downlink and other data-related functions. The processing unit 920 may be, or may include one or more elements of, a computing device as shown in Fig. 6 [000147] Satellite 900 may include a power system 925. Power system 925 may, for example, include solar panels to generate electrical power from sunlight. This power may be stored in onboard batteries and used to operate the satellite's systems, including the communication payload (e.g., transponders 905). Power system 925 may include regulators and converters to ensure a stable power supply. [000148]In some embodiments, satellite 900 may include a base station 930 (e.g., such as base station 800 described above with respect to Fig. 8). In other embodiments, satellite 900 may act as relay of radio signals wherein base station 930 may be placed on Earth (e.g., wherein base station 930 may include functionalities, units, modules and systems of base station 800 described above with respect to Fig. 8). Reference herein to actions or method steps taken by a satellite may mean or refer to said actions or steps being taken by a base station (such as base station 930) onboard the satellite. [000149] Satellite 900 may be a Low Earth Orbit (LEO) satellite, Geostationary Earth Orbit (GEO) satellite, Medium Earth Orbit (MEO) satellite, Very Low Earth Orbit (VLEO) or any other type of satellite suitable for providing communication. Satellite 900 may be part of a 3D constellation of satellites of different orbits. Satellite 900 may be part of a non-terrestrial network (NTN). [000150] In some embodiments, some of the components shown in Fig. 9 may be omitted. In some embodiments, satellite 900 may include additional components that are not shown in Fig. 9 and that may be required for supporting the communication of the satellite with base stations and / or user equipment. [000151] It is anticipated that embodiments of the invention may have an impact on existing or future non-terrestrial network telecommunications architecture and associated standards. For example, embodiments of the invention may be employed in, 5G, beyond 5G, 6G, and / or future NTN architectures. The ongoing development of these standards, and the conceptualization and implementation of future standards, may rely on systems and / or methods of the present invention. [000152] For example, embodiments of the invention may extend the capabilities of the 3 GPP, 5G, and / or 6G standards in that new indications are made in the SIB indicating parallel support (and / or momentary unavailability) of direct transfer and store and forward modes of operation. The SIB may also include a maximum data storage forwarding time as an additional system information element on which the UE may base a decision in determining an allowable delay tolerance of data to be transmitted. [000153] Unless specifically stated otherwise, as apparent from the foregoing discussion, it is appreciated that throughout the specification discussions utilizing terms such as "processing," "computing," "calculating," "determining," or the like, refer to the action and / or processes of a computer or computing system, or similar electronic computing device, that manipulates and / or transforms data represented as physical, such as electronic, quantities within the computing system's registers and / or memories into other data similarly represented as physical quantities within the computing system's memories, registers or other such information storage, transmission or display devices. [000154] It should be recognized that embodiments of the invention may solve one or more of the objectives and / or challenges described in the background, and that embodiments of the invention need not meet every one of the above objectives and / or challenges to come within the scope of the present invention. [000155] In the above description, an embodiment is an example or implementation of the inventions. The various appearances of "one embodiment,” "an embodiment" or "some embodiments" do not necessarily all refer to the same embodiments. [000156] Although various features of the 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 invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. While the invention has been described with respect to a limited number of embodiments, it should be understood by a person of ordinary skill in the art that one or more features from one particular embodiment or group of embodiments may be combined with features of another embodiment or group of embodiments. [000157] Reference in the specification to "some embodiments", "an embodiment", "one embodiment" or "other embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments, of the inventions. [000158] It is to be understood that the phraseology and terminology employed herein is not to be construed as limiting and are for descriptive purposes only. [000159] It is to be understood that the details set forth herein do not construe a limitation to an application of the invention. [000160] It is to be understood that the terms “including”, “comprising”, “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, or integers or groups thereof and that the terms are to be construed as specifying components, features, steps, or integers. [000161] If the specification or claims refer to "an additional" element, that does not preclude there being more than one of the additional elements. [000162] It is to be understood that where the claims or specification refer to "a" or "an" element, such reference is not to be construed that there is only one of that element. [000163] It is to be understood that where the specification states that a component, feature, structure, or characteristic "may", "might", "may" or "could" be included, that a particular component, feature, structure, or characteristic is not required to be included. [000164] Where applicable, although state diagrams, flow diagrams or both may be used to describe embodiments, the invention is not limited to those diagrams or to the corresponding descriptions. For example, flow need not move through each illustrated box or state, or in exactly the same order as illustrated and described.

Claims

1. A method for operating a satellite equipped with a base station, the method comprising: indicating, to a user equipment “UE” attempting to connect to the satellite, that the satellite supports both:(i) direct transfer; and(ii) store and forward “S&F”modes of operation;receiving, from the UE, a set of data comprising an indication of which mode of operation the satellite should use to transmit the set of data; andbased on the mode of operation indicated by the UE, either:transmitting the set of data to one of:a second satellite; ora ground station;orstoring the set of data in a data storage and transmitting the set of data to the ground station at a later point in time.

2. The method of claim 1, wherein indicating that the satellite supports both direct transfer and S&F modes of operation comprises sending to the UE, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the satellite supports both direct transfer and S&F modes of operation.

3. The method of claim 2, wherein the SIB comprises a system information element indicating a maximum data storage forwarding time.

4. The method according to any of claims 1-3, comprising indicating a momentary unavailability of one of the supported modes of operation.

5. The method according to claim 4, wherein indicating a momentary unavailability of the S&F mode of operation is based on a remaining data storage capacity of the satellite.

6. The method according to claim 4 or 5, wherein indicating a momentary unavailability of the S&F mode of operation is linked to a priority of the set of data, and wherein different indications for different data priorities are available.

7. The method according to any of claims 1-3, wherein indicating support for the S&F mode of operation comprises indicating one or more data priorities, wherein indicating by the UE to use S&F is subject to a subscription of the UE, and wherein for different data priorities usage of S&F for transmitting the set of data from the UE results in corresponding different costs.

8. The method according to claim 4, wherein indicating a momentary unavailability of the direct transfer mode of operation is based on an inter-satellite link “ISL” capacity shortage.

9. The Method according to claim 1, where non-access stratum “NAS” data is always treated as direct transfer.

10. Method according to claim 8 wherein the NAS data comprises at least one of: authentication, identification, registration, security, or session management signalling.

11. The method of any of claims 1-10, comprising selecting, by the satellite, to store the set of data and transmit the set of data to the ground station at the later point in time irrespective of the mode of operation indicated by the UE based on at least one of:a delay tolerance of the set of data;a security level of the set of data;an emergency level of the set of data;a location of the UE;a location of the satellite;a location of the second satellite;a location of the ground station;an accumulated size of data to be sent to the second satellite;a remaining data storage capacity of the satellite; ora remaining data storage capacity of the second satellite.

12. The method of any of claims 1-10, comprising selecting, by the satellite, to transmit the set of data irrespective of the mode of operation indicated by the UE based on at least one of:a delay tolerance of the set of data;a security level of the set of data;an emergency level of the set of data;a location of the UE;a location of the satellite;a location of the second satellite;a location of the ground station;an accumulated size of data to be sent to the second satellite;a remaining data storage capacity of the satellite; or a remaining data storage capacity of the second satellite.

13. The method according to any of claims 1-10, wherein if the remaining satellite data storage capacity reaches a first capacity value, then transmitting at least some of the data stored in the data storage to one of the second satellite or the ground station.

14. The method according to claim 13, wherein once the remaining satellite data storage capacity reaches a second capacity value being less than the first capacity value, then stopping transmitting least some of the data stored in the data storage to the second satellite or the ground station.

15. A satellite equipped with a base station, the satellite configured to:indicate, to a user equipment “UE” attempting to connect to the satellite, that the satellite supports both:(i) direct transfer; and(ii) store and forward “S&F”modes of operation;receive, from the UE, a set of data comprising an indication of which mode of operation the satellite should use to transmit the set of data; andbased on the mode of operation indicated by the UE, either:transmit the set of data to one of:a second satellite; ora ground station;orstore the set of data in a data storage and transmit the set of data to the ground station at a later point in time.

16. The satellite of claim 15, configured to send to the UE, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the satellite supports both direct transfer and S&F modes of operation.

17. The satellite of claim 16, wherein the SIB comprises a system information element indicating a maximum data storage forwarding time.

18. The satellite according to any of claims 15-17, configured to indicate a momentary unavailability of one of the supported modes of operation.

19. The satellite according to claim 18, configured to indicate a momentary unavailability of the S&F mode of operation based on a remaining data storage capacity of the satellite.

20. The satellite according to claim 18 or 19, configured to indicate a momentary unavailability of the S&F mode of operation linked to a priority of the set of data, and wherein different indications for different data priorities are available.

21. The satellite according to any of claims 15-17, wherein indicating support for the S&F mode of operation comprises indicating one or more data priorities, wherein receiving an indication from the UE to use S&F is subject to a subscription of the UE, and wherein for different data priorities usage of S&F for transmitting the set of data from the UE results in corresponding different costs.

22. The satellite according to claim 18, configured to indicate a momentary unavailability of the direct transfer mode of operation based on an inter-satellite link “ISL” capacity shortage.

23. The satellite according to claim 15, configured to always transmit non-access stratum “NAS” data by direct transfer.

24. The satellite according to claim 23, wherein the NAS data comprises at least one of: authentication, identification, registration, security, or session management signalling.

25. The satellite of any of claims 15-24, configured to select to store the set of data and transmit the set of data to the ground station at the later point in time irrespective of the mode of operation indicated by the UE based on at least one of:a delay tolerance of the set of data;a security level of the set of data;an emergency level of the set of data;a location of the UE;a location of the satellite;a location of the second satellite;a location of the ground station;an accumulated size of data to be sent to the second satellite;a remaining data storage capacity of the satellite; or a remaining data storage capacity of the second satellite.

26. The satellite of any of claims 15-24, configured to select to directly transmit the set of data irrespective of the mode of operation indicated by the UE based on at least one of:a delay tolerance of the set of data;a security level of the set of data;an emergency level of the set of data;a location of the UE;a location of the satellite;a location of the second satellite;a location of the ground station;an accumulated size of data to be sent to the second satellite;a remaining data storage capacity of the satellite; or a remaining data storage capacity of the second satellite.

27. The satellite according to any of claims 15-24, configured to, if the remaining satellite data storage capacity reaches a first capacity value, then transmit at least some of the data stored in the data storage to one of the second satellite or the ground station.

28. The satellite according to claim 27, wherein once the remaining satellite data storage capacity reaches a second capacity value being less than the first capacity value, then stopping transmitting least some of the data stored in the data storage to the second satellite or the ground station.

29. A system comprising:a first satellite;a user equipment “UE”;a second satellite; anda ground station,wherein the UE is configured to attempt to connect to the first satellite,wherein the first satellite is configured to:indicate, to the UE, that the first satellite supports both:(i) direct transfer; and(ii) store and forward “S&F”modes of operation;receive, from the UE, a set of data comprising an indication of which mode of operation the first satellite should use to transmit the set of data; andbased on the mode of operation indicated by the UE, either:transmit the set of data to one of:the second satellite; orthe ground station;orstore the set of data and transmit the set of data to the ground station at a later point in time.

30. The system of claim 29, configured to carry out the method of any of claims 1-14.

31. A method for operating a user equipment “UE”, the method comprising:attempting to connect to a first satellite;receiving, from the first satellite, an indication that the first satellite supports both:(i) direct transfer; and(ii) store and forward “S&F”modes of operation; andsending, to the first satellite, a set of data comprising an indication of which mode of operation the first satellite should use to transmit the set of data.

32. The method of claim 31, wherein receiving the indication that the first satellite supports both direct transfer and S&F modes of operation comprises receiving, over a broadcast channel, a system information block (SIB) comprising at least one system information element indicating that the first satellite supports both direct transfer and S&F modes of operation.

33. The method of claim 32, wherein the SIB comprises a system information element indicating a maximum data storage forwarding time.

34. A user equipment “UE” configured to perform the method of any of claims 17-22.

35. The user equipment of claim 34, configured, by virtue of a subscription, to only indicate the S&F mode of operation, but to be able to indicate the direct transfer mode of operation for any abnormal data, emergency data or exceptional data.

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