Method, apparatus and computer program for a communication network

Abstract

There is provided a method performed by a user equipment, wherein the method comprises: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state. The method further comprises: based on the paging message, initiating an establishment of a connection to the first satellite.

Description

METHOD, APPARATUS AND COMPUTER PROGRAM FOR A COMMUNICATION NETWORKTECHNICAL FIELD

[0001] Various examples of this disclosure relate to methods, apparatuses, and computer programs. In particular, certain methods, apparatuses, and computer programs relate to a communication network.BACKGROUND

[0002] A communication network can be seen as a facility that enables communications between two or more communication devices or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network. A communication device may be provided with a service by an application server.

[0003] Such communication networks operate in accordance with standards such as those promulgated by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute). Examples of standards include the so-called 5G (5th Generation) standards promulgated by 3GPP.SUMMARY

[0004] Some examples of this disclosure will be described with respect to certain aspects. These aspects are not intended to indicate key or essential features of the embodiments of this disclosure, nor are they intended to be used to limit the scope thereof. Other features, aspects, and elements will be readily apparent to a person skilled in the art in view of this disclosure. For example, it should be appreciated that further aspects may be provided by the combination of any two or more of the various aspects described below.

[0005] According to a first aspect, there is provided a method performed by a user equipment, UE, the method comprising: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0006] According to a second aspect, there is provided a user equipment comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to perform at least: receiving a paging message comprising an indication that satellite access is requested for an internet protocolmultimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0007] According to a third aspect, there is provided a user equipment comprising: means for causing the user equipment to perform at least: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0008] According to a fourth aspect, there is provided a user equipment comprising: circuitry configured to perform: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0009] According to a fifth aspect, there is provided a program (e.g., computer program) comprising instructions, which when executed by a user equipment, cause the user equipment to perform at least: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0010] The following are applicable to each (e.g., one or more, including all) of the above first to fifth aspects.

[0011] In some examples, the IMS session is an IMS protocol data unit session.

[0012] In some examples, the user equipment is further caused to perform: transmitting, to a base station, a first indication that the user equipment supports internet protocol multimedia subsystem, IMS, over satellite.

[0013] In some examples, the user equipment is further caused to perform: transmitting, to the base station, a second indication that UE-to-satellite-to-UE, UE-Sat-UE, is preferred for IMS.

[0014] In some examples, at least one of: the first indication, or the second indication, are included in subscription data for the user equipment.

[0015] In some examples, the identity of the first satellite is comprised in a list in the paging message.

[0016] In some examples, the user equipment is further caused to perform: based on connecting to the first satellite, initiating a connection with an originating UE for the IMS session via a UE-Sat-UE connection.

[0017] In some examples, the initiating of the establishment of the connection to the first satellite comprises re-establishing a deactivated IMS session of the UE that was deactivated based on the UE moving to the idle state.

[0018] In some examples, the initiating of the connection with the originating UE is based on the indication that satellite access is requested for the IMS session.

[0019] In some examples, the user equipment is further caused to perform: based on the initiating of the establishment of the connection to the first satellite, transitioning from the idle state to a connected state.

[0020] According to a sixth aspect, there is provided a method performed by a first network entity, wherein the method comprises: receiving, from a second network entity, an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; based on the indication, determining an identity of a first satellite, wherein the first satellite is related to a location associated with the user equipment; and initiating a transmission of a paging message to the user equipment, wherein the paging message comprises the indication that satellite access is requested for the IMS session and the identity of the first satellite.

[0021] According to a seventh aspect, there is provided a first network entity comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the first network entity to perform at least: receiving, from a second network entity, an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; based on the indication, determining an identity of a first satellite, wherein the first satellite is related to a location associated with the user equipment; and initiating a transmission of a paging message to the user equipment, wherein the paging message comprises the indication that satellite access is requested for the IMS session and the identity of the first satellite.

[0022] According to an eighth aspect, there is provided a first network entity comprising: means for causing the first network entity to perform at least: receiving, from a second network entity, an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; based on the indication, determining an identity of a first satellite, wherein the first satellite is related to a location associated with the user equipment; and initiating a transmission of a paging message to the user equipment, wherein the paging message comprises the indication that satellite access is requested for the IMS session and the identity of the first satellite.

[0023] According to a ninth aspect, there is provided a first network entity comprising: circuitry configured to perform at least: receiving, from a second network entity, an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; based on the indication, determining an identity of a first satellite, whereinthe first satellite is related to a location associated with the user equipment; and initiating a transmission of a paging message to the user equipment, wherein the paging message comprises the indication that satellite access is requested for the IMS session and the identity of the first satellite.

[0024] According to a tenth aspect, there is provided a program (e.g., computer program) comprising instructions, which when executed by a first network entity, cause the first network entity to perform at least: receiving, from a second network entity, an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; based on the indication, determining an identity of a first satellite, wherein the first satellite is related to a location associated with the user equipment; and initiating a transmission of a paging message to the user equipment, wherein the paging message comprises the indication that satellite access is requested for the IMS session and the identity of the first satellite.

[0025] The following are applicable to each (e.g., one or more, including all) of the above sixth to tenth aspects.

[0026] In some examples, the determining of the identity of the first satellite comprises: obtaining information about the location associated with the user equipment; and determining the identity of the first satellite based on the information, wherein the first satellite provides a cell for the location associated with the user equipment.

[0027] In some examples, the location associated with the user equipment comprises an indication of a cell or tracking area for the user equipment before the user equipment went into idle mode.

[0028] In some examples, the first network entity is an access and mobility management function, AMF.

[0029] In some examples, the second network entity is one of: a policy control function, PCF, a unified data repository, UDM, or a home subscriber server, HSS,

[0030] According to an eleventh aspect, there is provided a method performed by a second network entity, the method comprising: receiving an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; obtaining information that indicates that the user equipment is an idle state; and providing, to a second network entity, the indication that satellite access is requested for the IMS session, for the user equipment.

[0031] According to an twelfth aspect, there is provided a second network entity comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the second network entity to perform at least: receiving an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; obtaining information that indicates that the userequipment is an idle state; and providing, to a second network entity, the indication that satellite access is requested for the IMS session, for the user equipment.

[0032] According to an thirteenth aspect, there is provided a second network entity comprising: means for causing the second network entity to perform at least: receiving an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; obtaining information that indicates that the user equipment is an idle state; and providing, to a second network entity, the indication that satellite access is requested for the IMS session, for the user equipment.

[0033] According to an fourteenth aspect, there is provided a second network entity comprising: circuitry configured to perform at least: receiving an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; obtaining information that indicates that the user equipment is an idle state; and providing, to a second network entity, the indication that satellite access is requested for the IMS session, for the user equipment.

[0034] According to an fifteenth aspect, there is provided a program (e.g., computer program) comprising instructions, which when executed by a second network entity, cause the second network entity to perform at least: receiving an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment; obtaining information that indicates that the user equipment is an idle state; and providing, to a second network entity, the indication that satellite access is requested for the IMS session, for the user equipment.

[0035] The following are applicable to each (e.g., one or more, including all) of the above eleventh to fifteenth aspects.

[0036] In some examples, the indication that satellite access is requested for the IMS session, for the user equipment is provided to the second network entity via a session management function, SMF.

[0037] In some examples, the providing of the indication is based on the information that indicates that the user equipment is an idle state

[0038] In some examples, the second network entity is caused to perform: obtaining information that the user equipment supports IMS over satellite access; and based on the information that the user equipment supports IMS over satellite access, providing, to the first network entity, an indication of the support for IMS over satellite access for the user equipment and a request for information about a radio access technology for the user equipment.

[0039] In some examples, the second network entity is caused to perform: receiving, from a session management function, an indication that the user equipment has connected to a satellite with an identity of a first satellite; and based on the indication, providing, to a callsession control function, a notification that the user equipment has connected to a satellite with the identity of the first satellite.

[0040] In some examples, the first network entity is an access and mobility management function, AMF.

[0041] In some examples, the second network entity is one of: a policy control function, PCF, a unified data repository, UDM, or a home subscriber server, HSS,

[0042] According to a sixteenth aspect, there is provided a method performed by a user equipment, UE, the method comprising: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and information that indicates identities of a plurality of satellites, wherein the user equipment is in an idle state; selecting a first satellite from the plurality of satellites based on the paging message and information about a location of the user equipment; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0043] According to a seventeenth aspect, there is provided a user equipment comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to perform at least: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and information that indicates identities of a plurality of satellites, wherein the user equipment is in an idle state; selecting a first satellite from the plurality of satellites based on the paging message and information about a location of the user equipment; and based on the paging message, initiating an establishmentof a connection to the first satellite.

[0044] According to an eighteenth aspect, there is provided a user equipment comprising: means for causing the user equipment to perform at least: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and information that indicates identities of a plurality of satellites, wherein the user equipment is in an idle state; selecting a first satellite from the plurality of satellites based on the paging message and information about a location of the user equipment; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0045] According to a nineteenth aspect, there is provided a user equipment comprising: circuitry configured to perform: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and information that indicates identities of a plurality of satellites, wherein the user equipment is in an idle state; selecting a first satellite from the plurality of satellites based on the paging message and information about a location of the user equipment; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0046] According to a twentieth aspect, there is provided a program (e.g., computer program) comprising instructions, which when executed by a user equipment, cause the user equipment to perform at least: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and information that indicates identities of a plurality of satellites, wherein the user equipment is in an idle state; selecting a first satellite from the plurality of satellites based on the paging message and information about a location of the user equipment; and based on the paging message, initiating an establishment of a connection to the first satellite.

[0047] The following are applicable to each (e.g., one or more, including all) of the above sixteenth to twentieth aspects.

[0048] In some examples, the IMS session is an IMS protocol data unit session.

[0049] In some examples, the user equipment is further caused to perform: transmitting, to a base station, a first indication that the UE supports internet protocol multimedia subsystem, IMS, over satellite.

[0050] In some examples, the user equipment is further caused to perform: transmitting, to the base station, a second indication that UE-to-satellite-to-UE, UE-Sat-UE, is preferred for IMS.

[0051] In some examples, at least one of: the first indication, or the second indication, are included in subscription data for the UE.

[0052] In some examples, respective ones of the plurality of identities of satellites are associated with a tracking area in the paging message, wherein the selecting comprises: selecting the first satellite based on the paging message and a tracking area of the UE, wherein the information about the location of the UE comprises the tracking area of the UE.

[0053] In some examples, the user equipment is further caused to perform: obtaining the information about the location of the user equipment based on a global positioning system of the UE, or received signalling from the network.

[0054] In some examples, the user equipment is further caused to perform: based on connecting to the first satellite, initiating a connection with an originating UE for the IMS session via a UE-Sat-UE connection.

[0055] In some examples, the initiating of the connection with the originating UE is based on the indication that satellite access is requested for the IMS session.

[0056] In some examples, the initiating of the establishment of the connection to the first satellite further comprises: transitioning from the idle state to a connected state.

[0057] A computer product stored on a medium may cause an apparatus to perform the methods as described herein.

[0058] A non-transitory computer readable medium comprising program instructions, that, when executed by an apparatus, cause the apparatus to perform the methods as described herein.

[0059] An electronic device may comprise apparatus as described herein.

[0060] Various other aspects and further embodiments are also described in the following detailed description and in the attached claims.

[0061] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. The embodiments that do not fall under the scope of the claims are to be interpreted as examples useful for understanding the disclosure.

[0062] List of Abbreviations:AF: Application FunctionAGW: Access gatewayAMF: Access and Mobility Management FunctionAN: Access NetworkBS: Base StationCM: Connection managementCN: Core NetworkCSCF: Call session control functionDL: DownlinkeNB: eNodeBgNB: gNodeBHSS: Home subscriber serverIP: Internet protocolIMS: IP multimedia subsystemLTE: Long Term EvolutionNEF: Network Exposure FunctionNG-RAN: Next Generation Radio Access NetworkNF: Network FunctionNR: New RadioNRF: Network Repository FunctionNTN: Non-terrestrial networkNW: NetworkPCF Policy Control FunctionP-CSCF: Proxy CSCFPLMN: Public Land Mobile NetworkRAN: Radio Access NetworkRF: Radio FrequencyRRC: Radio resource controlS-CSCF: Serving CSCFSMF: Session Management FunctionTN: Terrestrial networkUE: User EquipmentUDR: Unified Data RepositoryUDM: Unified Data ManagementUL: UplinkUPF: User Plane Function3GPP: 3rdGeneration Partnership Project5G: 5thGeneration5GC: 5G Core network5G-AN: 5G Radio Access Network5GS: 5G SystemBRIEF DESCRIPTION OF DRAWINGS

[0063] Some examples will now be described, by way of illustrative and non-limiting example only, with reference to the accompanying drawings in which:

[0064] FIG. 1 shows an example of a schematic representation of a 5G communication system;

[0065] FIG. 2 shows an example of a schematic representation of an apparatus for the 5G communication system of FIG. 1;

[0066] FIG. 3 shows an example of a schematic representation of a communication device;

[0067] FIG. 4 shows an example of a schematic representation of media and control signalling for an IMS user plane through terrestrial and non-terrestrial network elements;

[0068] FIG. 5 shows an example of a schematic representation of a communication system with access gateway resource allocation in satellites;

[0069] FIG. 6 shows an example of a signalling and operations diagram for a session establishment procedure with activation of optimized media routing;

[0070] FIG. 7 shows an example of a signalling and operations diagram for the establishment of an IMS session with a UE-to-satellite-to-UE connection;

[0071] FIG. 8 shows an example of another signalling and operations diagram for the establishment of an IMS session with a UE-to-satellite-to-UE connection;

[0072] FIG. 9 shows an example signalling and operations diagram for a user equipment to register satellite capabilities with a core network;

[0073] FIG. 10 shows an example method flow diagram performed by an apparatus;

[0074] FIG. 11 shows another example method flow diagram performed by an apparatus;

[0075] FIG. 12 shows another example method flow diagram performed by an apparatus;

[0076] FIG. 13 shows another example method flow diagram performed by an apparatus; and

[0077] FIG. 14 shows an example of a schematic representation of an apparatus.DETAILED DESCRIPTION

[0078] Terrestrial networks (TN) and non-terrestrial networks (NTN) represent two different approaches to communication infrastructure. TNs rely on ground-based infrastructure, such as base stations, core network infrastructure, and physical cables to deliver communication services. TNs are known fortheir high-speed data transfer, low latency, and reliability due to shorter signal travel distances and stable environmental conditions. TNs are cost-effective to deploy in urban and suburban areas with existing infrastructure. However, their coverage is limited to areas where physical infrastructure is present, making them less effective in remote or challenging terrains, like mountains or oceans. Examples of TNs include cellular networks and wired broadband services.

[0079] Non-terrestrial networks (NTNs) operate above the Earth's surface using platforms, such as satellites in low Earth orbit (LEO), medium Earth orbit (MEO), geostationary orbit (GEO), high-altitude platforms (HAPS), drones, and unmanned aerial vehicles (UAVs). NTNs may provide a global coverage, especially in underserved or remote regions where TNs are impractical. NTNs can be integral to applications like global internet access, disaster response, environmental monitoring, and military communications. They also can complement TNs in some 5G systems by enhancing network resilience and extending connectivity to areas like aircraft, ships, and isolated communities. However, NTNs face specific challenges, such as higher latency (especially with GEO satellites) and higher deployment costs compared to terrestrial systems.

[0080] TNs and NTNs can together form hybrid systems that combine both approaches to improve global coverage. This integration may be increasingly advantageous for future communication networks, and is expected to become more prevalent as cellular systems move into 6G.

[0081] The internet protocol (IP) multimedia subsystem (IMS) is a standardised architectural framework for delivering IP multimedia services. Various voice over IP technologies are available on smartphones; IMS provides a standard protocol across vendors. IMS often uses internet engineering task force (IETF) protocols, such as the session initiation protocol (SIP).IMS is intended to aid the access of multimedia and voice applications from wireless and wireline terminals, to create a form of fixed-mobile convergence. This is done by having a horizontal control layer that isolates the access network from the service layer. From a logical architecture perspective, services need not have their own control functions, as the control layer is a common horizontal layer.

[0082] Examples of global standards based on IMS include MMTel, which is the basis for Voice over LTE (VoLTE), Wi-Fi Calling (VoWIFI), and Video over LTE (ViLTE).

[0083] IMS sessions may be provided via a TN, a NTN, or a mixture of both TN / NTN.

[0084] FIG. 4 shows a schematic representation of media and control signalling for an IMS user plane through terrestrial and non-terrestrial network elements. There are shown three user equipments, labelled IIE-A 401 , IIE-B 403, and IIE-C 405. IIE-A 401 is an originating UE (e.g., initiating an IMS call), while IIE-B 403 and IIE-C 405 are terminating UEs (e.g., receiving an IMS call from IIE-A 401). There is also shown an IMS network domain 407. The IMS network domain 407 is associated with a terrestrial network (TN) (ground network). UE-A401 is connected to a first satellite 409. IIE-C 405 is connected to a second satellite 411. The first 409 and second satellites 411 are part of a non-terrestrial network (NTN).

[0085] As depicted in FIG. 4, UE-A401 initiates an IMS call with IIE-B 403, which is connected to a TN (not a satellite). IMS signalling (e.g., session initiation protocol (SIP) signalling) related to the IMS call is transmitted from IIE-A 401 to the first satellite 409, then to the IMS network domain 407, then to IIE-B 403. This is shown with a dashed arrow 413. The same signalling path is used for IMS media for the IMS call, which is shown with a dotted line 415. FIG. 4 also depicts an IMS call to IIE-C 405 which is connected to the second satellite 411. IMS media for the IMS call is transmitted from UE-A401 to the first satellite 409, then onto the second satellite 411, then to IIE-C 407. This is shown with a solid line 417. However, IMS signalling related to the IMS call does not follow the same path as the IMS media. Instead, the IMS signalling still travels through the IMS network domain 407 (in the TN), even though both UE-A401 and UE-C 405 are connected to NTNs. This is shown with the dashed arrow 413. Due to this, there is additional latency for the IMS signalling, as the signalling is transmitted between both the TN and NTN. Stated differently, a feeder link is used to route IMS media towards the ground IMS network, which adds latency due to the use of the feeder link (additional path delays). A feeder link refers to a radio link connecting a satellite gateway (on the ground) to the satellite. For example, in FIG. 4, the satellite gateway may be comprised in the IMS network domain 407. In other examples, the satellite gateway may instead be referred to as a ‘ground station’ or ‘earth station’, such that these terms may be used interchangeably.

[0086] FIG. 5 shows a schematic representation of a communication system with access gateway (AGW) resource allocation in satellites. A first UE 501 is connected to core network entities 503 of a TN, wherein the core network entities 503 are connected to IMS entities 505.The first UE 501 is also connected to a first satellite 507, wherein the first satellite 507 is associated with a radio access network (RAN) 509, an intermediate user plane function (I-UPF) 511, and an IMS access gateway (IMS-AGW) 513. The IMS-AGW513 is connected to the IMS entities 505 on the ground.

[0087] A second UE 515 is connected to core network entities 517 of a TN, wherein the core network entities 511 are connected to IMS entities 519. The second UE 515 is also connected to a second satellite 521, wherein the second satellite 521 is associated with a RAN 523, an l-UPF 525, and an (IMS) AGW (in the non-terrestrial network, NT) 527. The AGW 527 is connected to the IMS entities 519 on the ground.

[0088] Control plane signalling (e.g., for an IMS call) is provided from the first UE 501 to the second UE 515 via the ground entities (i.e. , via the core network entities 503, 517 and the IMS entities 505, 519). User plane signalling is provided from the first UE 501 to the second UE 515 via the first satellite 507 and the second satellite 521.

[0089] In the UE-Sat-UE communications shown in FIG. 5, an operator is to deploy an l-UPF and an AGW on-board each satellite (e.g., 507, 521) and use satellite resources to route IMS media.

[0090] The bandwidth of feeder links (i.e., the link from the ground to the satellite) may not be consistent as the bandwidth is shared and limited. Guaranteeing quality of service (QoS) over this link is not in control of the operator (e.g., and is out of scope of 3GPP). This means that utilising feeder links as part of user plane signalling a less preferable way of providing IMS voice / video calls when any of the associated users / devices is under satellite coverage. Operators may want to monetise the feature of utilising satellite coverage by providing ‘premium’ customers with optimisations for UE-Sat-UE media routing.

[0091] Procedures for media routing with the involvement of satellites are covered in 3GPP TS 23.228 (inAE.5).

[0092] FIG. 6 shows a signalling and operations diagram for a session establishment procedure with activation of optimized media routing (see Figure AE.5.1-1 of 3GPP TS 23.228).

[0093] At 6.1 (i.e., FIG. 6, at 1), a UE-A transmits an session initiation protocol (SIP) invite to a proxy call session control function for UE-A (referred to as P-CSCF A), containing an initial session description protocol (SDP) offer, to P-CSCF A. The access information in the SIP INVITE request indicates that the UE is accessing from NR satellites access.

[0094] At 6.2, the P-CSCF A and a 5GC communication to retrieve access network information for UE-A.

[0095] The signalling and operations that follow assume that, after receiving the SIP INVITE request indicating NR satellite access, UE A is in the non-roaming scenario and the P-CSCF A supports UE-Satellite-UE communication.

[0096] At 6.3, the P-CSCF A allocates an IMS access gateway (AGW) on the ground (referred to as IMS AGWA or A.

[0097] At 6.3a, the P-CSCF A provides an allocation request to the IMS AGWA.

[0098] At 6.3b, the IMS AGWA provides a response to the P-CSCF A to allocate transport resources.

[0099] At 6.4, the P-CSCF A updates the SIP invite request by inserting the identification of the satellite serving IIE-A and updates the SDP offer with the I MS-AGW transport addresses allocated in 6.3. The P-CSCF A transmits, via an IMS core to a P-CSCF B, the invite with the identifier of the satellite serving IIE-A, and the SDP offer.

[0100] At 6.5, the P-CSCF B retrieves access network (AN) information. After receiving the SIP invite request, which contains a satellite identification indicating that UE A is using regenerative satellite access, if UE B is not in roaming, P-CSCF B retrieves the AN information of a UE-B from a PCF network. If the UE-B is also using the regenerative satellite access, the serving satellite identification is contained in the AN information.

[0101] At 6.6, based on UE B not roaming, and the two satellites identified by the two satellite identifications received in 6.4 and 6.5 are the same or connected with ISL(s), P-CSCF B determines to activate the UE-Satellite-communication. If UE-Satellite-UE communications is not activated, P-CSCF B selects an IMS-AGW B' on the ground for UE B; otherwise, P-CSCF B selects an IMS-AGW B on satellite for UE B.

[0102] At 6.6a and 6.6b, based on the decision in 6.6, P-CSCF B interacts with IMS-AGW B on satellite or IMS-AGW B' on the ground to allocate transport resources.

[0103] 6.7 to 6.20 are performed based on the activating of UE-Satellite-UE communication. Otherwise, SIP message routing procedures with IMS-AGW on the ground should be performed after P-CSCF B selects a ground IMS-AGW B' for usage.

[0104] At 6.7, P-CSCF B forwards the updated SIP INVITE request to UE B.

[0105] At 6.8, UE-B generates an 18X response with an SDP answer.

[0106] At 6.9, UE-B returns a 18X response with an SDP answer to the P-CSCF B.

[0107] At 6.9a to 6.9b, after receiving the SDP Answer, P-CSCF B interacts with the IMS-AGW B to allocate transport resources.

[0108] At 6.10, P-CSCF B instructs the PCF to authorize the resources necessary to establish a QoS flow for media via Npcf_PolicyAuthorization_Update service operation. The P-CSCF B should send following parameters via the request: a flow description information that contains the IP address of the IMS-AGW B, a data network access identifier (DNAI) associated with the IMS-AGW B on satellite and corresponding N6 traffic routing information.

[0109] At 6.11, P-CSCF B updates the 18X response to carry the identifier of the satellite serving UE B to indicate that UE-Satellite-UE communication is activated. Then, P-CSCF B returns the updated 18X response to the originating side via IMS core.

[0110] At 6.12, based on the identification of the satellite serving UE B in 6.11, P-CSCF A determines to perform UE-satellite-UE communication and select an IMS-AGW A on the satellite.

[0111] At 6.12a to 6.12c, P-CSCF A interacts with IMS-AGWAon satellite to allocate transport resources for both IMS access and core network sides. P-CSCF A also releases the IMS-AGW A' on the ground.

[0112] At 6.13, P-CSCF A instructs the PCF to authorize the resources necessary to establish a QoS flow for media via Npcf_PolicyAuthorization_Update service operation. P-CSCF B should send the following parameters via the request: a flow description information that contains the IP address of the IMS-AGW A, a DNAI associated with the IMS-AGW A on satellite and corresponding N6 traffic routing information.

[0113] At 6.14, P-CSCF A updates the SDP answer in the 18X response with the IMS-AGW transport addresses allocated in 6.12, and forwards the updated 18X response to UE A.

[0114] At 6.15, UE A acknowledges the response and sends the response confirmation to P-CSCFA.

[0115] At 6.16 to 6.17, P-CSCF A forwards the response confirmation to P-CSCF B. The response confirmation includes the SDP offer modified / generated by P-CSCF A, which contains the IMS-AGW transport address obtained in 6.12. Upon receiving the SDP offer, P-CSCF B updates the allocated IMS-AGW on the satellite for UE B with the transport address in the SDP offer.

[0116] At 6.18, P-CSCF B sends the response confirmation to UE B.

[0117] At 6.19, the procedure continues to set up the call (between UE-Aand UE-B).

[0118] In this manner, as described above alongside FIG. 6, based on the originating P-CSCF (P-CSCF A) receiving the initial invite request from the originating UE (UE-A) using regenerative NR satellite access, it selects the IMS-AGW on the ground and triggers media negotiation by sending SDP offer to the terminating side indicating that satellite access is used on the originating side. If the terminating P-CSCF activates UE-satellite-UE communication, the originating P-CSCF re-selects an IMS-AGW on the satellite. In this manner, the procedure for optimized media routing for connecting a UE-Sat-UE call, assumes that the terminating UE (UE-B) is in a connected state / mode (e.g., connection management (CM) connected state). However, it may be that a UE is currently in a mode / state other than ‘connected’.

[0119] One or more of the problems identified above are addressed in one or more of the examples described below.

[0120] In some examples, there is a method performed by a UE. The method comprises: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite,wherein the user equipment is in an idle state. The method further comprises: based on the paging message, initiating an establishment of a connection to the first satellite.

[0121] In some examples, there is a method performed by a UE. The method comprises: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and information that indicates identities

[0122] of a plurality of satellites, wherein the user equipment is in an idle state. The method further comprises: selecting a first satellite from the plurality of satellites based on the paging message and information about a location of the user equipment. The method further comprises: based on the paging message, initiating an establishment of a connection to the first satellite.

[0123] These examples will be described in more detail below, alongside FIGS. 7 to 14.

[0124] Before explaining the examples above in greater detail, an example communication device (as shown in FIG. 3) that is capable of participating in an IMS session via satellite will be described. The communication device is part of a communication system (as shown in FIG.1). The communication device is able to communicate with one or more of the entities of the communication system (as shown in FIG. 1) via an apparatus (as shown in FIG. 2), which may be part of / comprised in a base station.

[0125] Certain general aspects of the communication system and the communication device are briefly explained with reference to FIGS. 1 to 3 to assist in understanding the technology underlying the described examples.

[0126] FIG. 1 shows an example of a schematic representation of a 5G communication system 100. The wireless communication system 100 comprises one or more communication devices 102 such as user equipments (UEs), or terminals. The wireless communication system 100 comprises a 5G system (5GS). The 5GS comprises a 5G radio access network (5G-RAN) 106, a 5G core network (5GC) 104 comprising one or more network functions (NF), one or more application functions (AFs) 108, and one or more data networks (DNs) 110.

[0127] The 5G-RAN 106 may comprise one or more gNodeB (gNB) distributed unit (DU) functions connected to one or more gNodeB (gNB) centralized unit (CU) functions.

[0128] The 5GC 104 comprises an access and mobility management function (AMF) 112, a session management function (SMF) 114, an authentication server function (AUSF) 116, a user data management (UDM) 118, a user plane function (UPF) 120, a network exposure function (NEF) 122 and / or other NFs. Some of the examples as shown below may be applicable to 3GPP 5G standards. However, some examples may also be applicable to 5G-advanced, 4G, 3G, and / or other 3GPP standards (such as 6G and beyond).

[0129] In a wireless communication system 100, such as that shown in FIG. 1, communication devices 102, such as, terminals, user apparatuses, user equipments (UE), and / or machine-type communication devices are provided with wireless access via at least one base station or similar wireless transmitting and / or receiving node or point. The communication device 102 is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other devices. The communication device 102 may access a carrier provided by a base station or access point, and transmit and / or receive communications on the carrier.

[0130] FIG. 2 illustrates an example of an apparatus 200. The apparatus 200 may be for the 5G communication system of FIG. 1. In some examples, apparatus 200 may be for a 5G-advanced communication system, 4G communication system, 3G communication system, and / or other 3GPP communication system(s) (such as a 6G communication system and beyond). The apparatus 200 may be for controlling a function of one or more entities , such as the network entities of the 5G-RAN and / or the network functions of the 5GC as illustrated on FIG. 1. In some examples, apparatus 200 may be for controlling a function of one or more entities, such as one or more network entities and / or one or more network functions of a 5G-advanced communication system, 4G communication system, 3G communication system, and / or other 3GPP communication system(s) (such as a 6G communication system and beyond).

[0131] The apparatus 200 comprises at least one random access memory (RAM) 211a, at least one read only memory (ROM) 211b, at least one processor 212, 213 and an input / output interface 214. The at least one processor 212, 213 is coupled to the RAM 211a and the ROM 211b. The at least one processor 212, 213 may be configured to execute an appropriate software code 215. The software code 215 may, for example, allow, enable, and / or facilitate performance of one or more steps to perform one or more of the aspects and / or examples described in this disclosure. The software code 215 may be stored in the ROM 211b. The apparatus 200 may be interconnected with another apparatus 200 controlling another entity / function of the 5G-AN or the 5GC.

[0132] In some examples, apparatus 200 may be configured to provide one or more functions of the 5G-AN and / or the 5GC. For example, apparatus 200 may be configured to perform at least some functionality of a particular entity of the 5G-AN or the 5GC. For example, apparatus 200 may be configured to operate as a particular entity of the 5G-AN or the 5GC. In alternative examples, apparatus 200 may be configured to perform at least some functionality of two or more entities of the 5G-AN and / or the 5GC. For example, apparatus 200 may be configured to operate as two or more entities of the 5G-AN and / or the 5GC.

[0133] In some examples, apparatus 200 may be configured to provide one or more access network or core network functions of a 5G-advanced communication system, 4G communication system, 3G communication system, or other 3GPP communication system(such as a 6G communication system and beyond). For example, apparatus 200 may be configured to perform at least some functionality of a particular access network or core network entity of a 5G-advanced communication system, 4G communication system, 3G communication system, or other 3GPP communication system (such as a 6G communication system and beyond). For example, apparatus 200 may be configured to operate as a particular access network entity or core network entity of a 5G-advanced communication system, 4G communication system, 3G communication system, or other 3GPP communication system (such as a 6G communication system and beyond). In alternative examples, apparatus 200 may be configured to perform at least some functionality of two or more access network entities and / or core network entities of a 5G-advanced communication system, 4G communication system, 3G communication system, or other 3GPP communication system (such as a 6G communication system and beyond). For example, apparatus 200 may be configured to operate as two or more access network entities and / or core network entities of a 5G-advanced communication system, 4G communication system, 3G communication system, or other 3GPP communication system (such as a 6G communication system and beyond).

[0134] The apparatus 200 may comprise one or more circuits, or circuitry (not shown), which may be configured to perform one or more of the aspects and / or examples described in this disclosure.

[0135] FIG. 3 illustrates an example of a communication device 300. The communication device 300 may be similar to the communication device 102 illustrated in FIG. 1. The communication device 300 may be provided by any device capable of sending and receiving radio signals. Non-limiting and illustrative examples of a communication device 300 include a user equipment, a terminal, a mobile station (MS) or mobile device, such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), a personal data assistant (PDA) or a tablet provided with wireless communication capabilities, a machine-type communications (MTC) device, a Cellular Internet of things (CloT) device, or a terrestrial / maritime / aerial vehicle such as a car, a truck, a boat, an air plane, or a drone, or any combinations of these (or the like). The communication device 300 may provide, for example, communication of data for carrying communications. The communications may be one or more of voice, electronic mail (email), text message, multimedia, data, machine data and so on.

[0136] The communication device 300 may receive signals over an air or radio interface 307 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In FIG. 3, a transceiver apparatus is designated schematically by block 306. The transceiver apparatus 306 may be provided, for example, by means of a radiopart and associated antenna arrangement. The antenna arrangement may be arranged internally and / or externally to the mobile device.

[0137] The communication device 300 may be provided with at least one processor 301, at least one memory ROM 302a, at least one RAM 302b and other possible components 303 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The at least one processor 301 is coupled to the RAM 302b and the ROM 302a. The at least one processor 301 may be configured to execute appropriate software code 308. The software code 308 may, for example, allow, enable, and / or facilitate performance of one or more of the aspects and / or examples described in this disclosure. The software code 308 may be stored in the ROM 302a. The communication device 300 may comprise one or more circuits, or circuitry (not shown) which may be configured to perform one or more of the aspects and / or examples described in this disclosure.

[0138] The processor, storage and other relevant control apparatus may be provided on an appropriate circuit board and / or in chipsets. This feature is denoted by reference 304. The communication device may optionally have an interface (e.g., a user interface, such as keypad) 305, touch sensitive screen or pad, combinations thereof or the like. Optionally one or more of a display, a speaker and a microphone may be provided depending on the type of the device.

[0139] FIG. 7 shows an example of a signalling and operations diagram for the establishment of an IMS session with a UE-to-satellite-to-UE connection.

[0140] The following signalling and operations of S701 to S713 may replace steps 6.5 and 6.6 of FIG. 6. In this manner, as described below, a session establishment procedure may be provided that is able to address a scenario where a UE is in an idle state and a request for an IMS session / call is received.

[0141] At S701, a P-CSCF receives an invite (or request for an IMS session) from a IIE-A. The invite may be referred to as a session initiation protocol (SIP) invite. A SIP invite (or ‘SIPINVITE’) is a message from a calling party (e.g., IIE-A) towards a called party (e.g., a IIE-B) for initiating a SIP session (e.g., a voice call). IIE-A is considered to be an originating UE (i.e. , the UE initiating the IMS session). The invite comprises an indication of UE-B (as the called party / terminating UE). The invite comprises an identity / identification (ID) of a satellite. The ID of the satellite is an indication of the satellite that UE-A is connected to.

[0142] ‘UE-A may be referred to as a first UE and ‘UE-B’ may be referred to as a second UE, or vice-versa.

[0143] At S702, the P-CSCF provides, to a PCF, a request for at least one of: an access network information (ANI), or a CM state of a UE-B. UE-B is considered to a be terminating UE (i.e., the UE that is receiving the request UE-A). The P-CSCF also provides an indicationthat satellite access is requested for an IMS session (herein referred to as ‘UE-Sat-UE ind’). The request of S702 may be a ‘Npcf_PolicyAuthorization Request’, or any other suitable message.

[0144] At S703, the PCF provides the UE-Sat-UE indication to an SMF. The message of S703 may be a ‘Npcf_SMPolicyControl_UpdateNotify’ message, or any other suitable message. The PCF requests the ANI, and the state (e.g., CM state) of UE-B. The SMF provides the requested ANI, and an indication that UE-B is in idle state. In this manner, the PCF obtains information that indicates that UE-B is in idle state.

[0145] At S704, the PCF provides, to the P-CSCF, the ANI (that was requested in S702), and / or the UE-B CM state (that was requested in S702). The message of S704 may be a ‘Npcf_PolicyAuthorization response’ message, or any other suitable message.

[0146] The CM state of UE-B is idle (i.e. , an idle state, or idle mode). A UE in idle state has no active non-access stratum (NAS) signalling connection established with a core network (e.g., AMF).

[0147] At S705, the SMF provides, to an AMF, the UE-Sat-UE indication. The message of S705 may be a ‘Namf_N1N2MessageTransfer request’ message, or any other suitable message.

[0148] At S706, the AMF provides, to the SMF, a response to the message of S705.

[0149] At S707, based on the UE-Sat-UE indication, the AMF determines one or more identities of satellites (‘satellite IDs’) related to location information for UE-B (e.g.,, information about a (previous) location of UE-B).

[0150] The location information for UE-B may comprise information about a last known location of UE-B (e.g., before the UE went into idle mode). The location information may indicate, for example, a cell that UE-B was last connected to (or previously connected to), a last known TA of UE-B, a TA that UE-B was previously connected to, a longitude and latitude, etc. The AMF may also determine one or more satellite IDs associated with an area related to the location information (of UE-B). For example, the area related to the location information may be an area that neighbours the location information of the UE-B. For example, an area within a threshold distance of a location indicated by the location information, one or more cells within a threshold distance of a location indicated by the location information, one or tracking areas that are within a threshold distance of a location indication by the location information, or cell(s) that overlap and / or neighbour a cell indicated by the location information. In some examples, the location information for UE-B will indicate a cell that UE-B was last connected to. The AMF will determine a satellite ID, or satellite IDs, for satellite(s) that provide cell coverage at the cell indicated by the location information for UE-B. In some examples, the AMF will further determine a satellite ID, or satellite IDs, for satellite(s) that provide cellcoverage that neighbours and / or overlaps the cell indicated by the location information for UE-B.

[0151] For example, if ‘TAT or ‘Cell IDT was the last known TA or cell for IIE-B before IIE-B moved to CM Idle state, then theAMF determines a satellite ID in the coverage area including TA1 and / or Cell ID1. The AMF may also determine TAs or cells that neighboring TA1 and / or cell ID1 (in case of IIE-B idle mode mobility).

[0152] Based on the determining (of S707), the AMF may determine a list, wherein the list comprises at least one satellite ID (i.e. , an ID of a satellite). For example, the list may comprise identities for a plurality of (different) satellites. For example, the list comprises: ‘satellite IDT, ‘satellite ID3’, ‘satellite IDT. Each satellite may have a single (or unique) ID associated with that respective satellite. In other examples, the list comprising the at least one satellite ID may instead be one of: information comprising the at least one satellite ID, a group comprising the at least one satellite ID, a set comprising the at least one satellite ID, or the like.

[0153] At S708, the AMF provides, to a RAN (e.g., network entity, or base station), a paging (message) comprising the UE-Sat-UE indication, and an indication of at least one satellite ID (e.g., comprised in the list).

[0154] At S709, the RAN transmits, to IIE-B, a paging message comprising the UE-Sat-UE indication, and the indication of the at least one satellite ID.

[0155] At S710, based on the paging message, the UE initiates an establishment of a connection to a first satellite. The first satellite is identified in paging message (e.g., identified in the list).

[0156] In some examples, the identity of the first satellite is comprised in the list in the paging message, wherein the list comprises a plurality of satellites IDs. UE-B selects the first satellite based on the list and a location of UE-B. Information about the location of UE-B is accessible to UE-B (e.g., based on GPS, network positioning, etc.). The location of UE-B may be considered to be a ‘current’ location of UE-B (i.e., where the UE is currently located). For example, the information about the location of UE-B may indicate a tracking area (e.g., TA3) and / or a cell (e.g., cell ID2)

[0157] In some examples, the list further comprises information about at least one tracking area (TA) associated with each satellite ID (in the list). For example, the list identifies: ‘satellite IDT with ‘TAT, ‘satellite ID2’ with ‘TAT, and ‘satellite IDS’ with ‘TA3’. In another example, the list identifies: ‘satellite IDT with ‘TA1, TA2’, ‘satellite ID2’ with ‘TAT, and ‘satellite ID3’ with ‘TA1, TA3’. Based on the location of UE-B (e.g., a TA of UE-B), the UE determines a suitable satellite ID to connect to, based on the list.

[0158] Based on initiating the establishment of the connection to the first satellite, UE-B transitions from idle to connected mode / state.

[0159] At S711, once connected to the first satellite, the UE initiates a connection with IIE-A for the IMS (protocol data unit, PDU) session via a UE-Sat-UE connection. Stated differently, the UE triggers a service request procedure to activate the IMS (PDU) session (e.g., that was established earlier and deactivated based on the UE moving to CM Idle state). For example, the service request procedure may follow TS 23.502, 4.2.3.2.

[0160] At S712, the SMF provides, to the PCF, an indication that UE-B is connected via satellite. The indication may comprise an ID of the first satellite. The message of S712 may be a ‘Npcf_SMPolicyControl_Update request’ message, or any other suitable message.

[0161] At S713, the PCF provides, to the P-CSCF, the indication that UE-B is connected via satellite. The message of S713 may be a ‘Npcf_PolictAuthorization notify’ message, or any other suitable message. The P-CSCF may then provide an allocation request based on the indication that is received.

[0162] It should be understood that, in other examples, one or more of the steps in FIG. 7 may not be performed, or may be performed in a different order.

[0163] In some examples, the UE B (of FIG. 7) indicates a preference for UE-Sat-UE call in its subscription data. The UE-Sat-UE call may be offered to the UE as a special service by an operator.

[0164] As discussed above for FIG. 7 (e.g., at S701 to S704), based on the P-CSCF for UE B receiving the ‘INVITE’ (with Satellite ID serving UE A, SDP offer), P-CSCF queries PCF for the ANI of UE B and additionally provides the UE-Sat-UE indication. The P-CSCF also determines whether the UE is in CM idle or CM connected state with implicit subscription for notification when the UE B is connected (after paging and service request procedure).

[0165] The PCF queries (e.g., S703) the SMF to receive the ANI about UE B and also indicates the UE-Sat-UE call for UE B. The PCF configures the policy control request triggers (PCRT) to indicate if the UE B is idle and when it moves to connected state. The PCRT is used to request policy and charging control (e.g., the PCF configures conditions (PCRTs) at the SMF, and when these conditions are met, the SMF informs the PCF). In some examples, it is assumed that UE B is in idle state (i.e. PDU session for the IMS session is deactivated). The SMF responds (e.g., S704) to PCF with the ANI and also indicates that the UE B is in CM Idle state and is proceeding to do paging for UE B.

[0166] In some examples, based on a last known UE location (of UE B), the AMF lists the different satellite IDs that may be available in that location area (e.g., a list of different satellite IDs in different TAs) at this time. The AMF also adds the indication of UE-Sat-UE in the paging message sent to the NG-RAN. For example, see S707 to S708 of FIG. 7. The RAN then pages (e.g., S709) to the area indicated by the AMF and also includes the list of satellite IDs sent by the AMF. Based on UE-B receiving (e.g., S710) the paging message (via the paging channel),and based on the UE-Sat-UE indication and the list, the UE B tries to search and connect with the satellite indicated based on a location of UE B.

[0167] After UE B has connected to the satellite, the UE may trigger (e.g., S711) a service request procedure with the indication to connect to the IMS call (i.e. for UE-Sat-UE call to UE A). Once the PDU session for the IMS call is activated, the SMF triggers an SM Policy modification procedure due to the PORT set by the PCF (to update based on UE B moving to connected state). The SMF indicates the satellite ID through which the UE B is connected and activated the IMS PDU session. The PCF notifies the P-CSCF about the availability of the UE B via satellite ID with an indication. Accordingly, the P-CSCF selects an AGW (either TN or NTN) and sends a re-invite (‘REINVITE’) via the established PDU session. The re-invite is related to the (SIP) invite discussed above. A re-invite may have the same call identity (‘Call-ID’) and the same identity of the originating device (‘From tag’) as the invite that the re-invite is modifying. A ‘re-invite’ (compared to the ‘invite’) may change other headers as well as the message body. The same ‘Call-ID’ and the same ‘From Tag’ indicate to the SIP stack that the re-invite is not a new invite.

[0168] After the signalling and operations of FIG. 7, of S701 to S713, the procedure may continue to 6.6a of FIG. 6 in order to complete the UE-Sat-UE call.

[0169] FIG. 8 shows an example of another signalling and operations diagram for the establishment of an IMS session with a UE-to-satellite-to-UE connection.

[0170] At S800a, UE-B transmits an indication (‘a first indication’) of support for IMS over satellite to a RAN. The first indication may be provided during UE registration. The support (or capability) of UE-B for IMS over satellite is for the packet core. The support for IMS over satellite for UE-B indicates that UE-B is able to receive ‘new’ paging, wherein the paging comprises at least one identity of a satellite. This is described in more detail below.

[0171] The UE-B may also transmit, to the RAN, an indication (‘a second indication’) that UE-Sat-UE is preferred for IMS. The first indication and / or second indication are provided from the RAN to an AMR

[0172] At S800b, the AMF subscribes to notifications of satellite preferred access for UE-B from a home subscriber server or unified data repository. The subscription is based on the first and / or second indication. Stated differently, UE indicates a preference for UE-Sat-UE call in subscription data of UE-B. The AMF then subscribed to be notified of a satellite preferred access event from the UDM.

[0173] In some examples, the subscription request may be a ‘Nudm_UECM_Registration’ operation, or any other suitable operation.

[0174] The HSS / UDM provides a response, to the AMF, to the request to subscribe. For example, an acknowledgement that the AMF is now subscribed to be notified of a satellite preferred access event.

[0175] At S800c, an IMS application server (AS) receives an invite (or request for an IMS session) from a IIE-A for IIE-B. IIE-A is considered to be an originating UE (i.e., the UE initiating the IMS session), while IIE-B is the terminating UE. The invite comprises an identity / identification (ID) of a satellite.

[0176] The invite may comprise the ID of the satellite that is serving UE-A and an SDP offer.

[0177] ‘UE-A may be referred to as a first UE and ‘UE-B’ may be referred to as a second UE, or vice-versa.

[0178] At S801, the IMS AS provides an indication of a preference for IMS over satellite to the HSS / UDM. The indication may be a flag that may be set to ‘true’ or ‘false’ (e.g., a T, or ‘0’). The indication may be provided in a user data request.

[0179] In some examples, the IMSAS invokes aT-ADS (termi native-access domain selection) query to the HSS / UDM and sets the flag to true to indicate the preference for establishing the IMS call over satellite access from the originating side (i.e., from UE-A).

[0180] At S802, the HSS / UDM determines that UE-B supports IMS over satellite. The HSS / UDM may determine the support based on the subscription data of UE-B.

[0181] In this example, the HSS / UDM determines that UE-B does support IMS over satellite access by checking the UE-B subscription data and the received indication(s) from the AMF at S800b. As UE-B does support IMS over satellite access, the HSS / UDM determines to request the AMF to provide domain selection information.

[0182] At S803, the HSS / UDM provides a request, to the AMF, to provide information for selection of IMS (e.g., IMS voice) over satellite access. In response, the AMF indicates the support of IMS over satellite access with a time stamp (or information related to time) and information of a current radio access technology (RAT) type. The time stamp may indicate a time of a last radio contact with the UE-B.

[0183] In some examples, the request and response of S803 is a ‘Namf_MT_ProvideDomainSelectionlnfo’ request or response message. In other examples, any other suitable type of message is used.

[0184] At S804, the HSS / UDM determines that the UE-B is not connected to a satellite. Stated differently, the HSS / UDM determines (or obtains information that indicates) that UE-B is in an idle state (e.g., CM idle state). The HSS / UDM may determine that UE-B is not connected to a satellite based on the information about the current RAT.

[0185] At S805, the HSS / UDM informs the IMSAS that IMS over satellite is supported for UE-B. This may be considered to be a response to the preference for IMS over satellite indicated in the message of S801.

[0186] At S806, the HSS / UDM provides, to the AMF, an indication that satellite access is requested for an IMS session (herein referred to as an ‘UE-Sat-UE’ indication). In this manner, the UDM notifies the AMF about a preference for IMS over satellite for the IMS sessionrequested by IIE-A (i.e., in S801). The HSS / UDM notifies the AMF as the AMF previously subscribed to notifications in S800b.

[0187] The message of S806 may be a ‘Nudm_UECM’ message, or any other suitable type of message.

[0188] At S807, based on the UE-Sat-UE indication, the AMF determines one or more identities of satellites (‘satellite IDs’) associated with location information for IIE-B (i.e., information about a (previous) location of IIE-B).

[0189] The location information may comprise information about a last known location of UE-B (e.g., before the UE went into idle mode). The location information may indicate, for example, a cell that IIE-B was last connected to, last known TA of IIE-B, a longitude and latitude, etc. TheAMF may also determine one or more satellite IDs associated with an area related to the location information (of IIE-B). For example, the area related to the location information may be an area that neighbours the location information of the IIE-B. For example, an area within a threshold distance of a location indicated by the location information, one or more cells within a threshold distance of a location indicated by the location information, one or tracking areas that are within a threshold distance of a location indication by the location information, or cell(s) that overlap and / or neighbour a cell indicated by the location information. In some examples, the location information for IIE-B will indicate a cell that IIE-B was last connected to. TheAMF will determine a satellite ID, or satellite IDs, for satellite(s) that provide cell coverage at the cell indicated by the location information for IIE-B. In some examples, the AMF will further determine a satellite ID, or satellite IDs, for satellite(s) that provide cell coverage that neighbours and / or overlaps the cell indicated by the location information for IIE-B.

[0190] For example, if ‘TAT or ‘Cell IDT was the last known TA or cell for IIE-B before IIE-B moved to CM Idle state, then theAMF determines a satellite ID in the coverage area including TA1 and / or Cell ID1. The AMF may also determine TAs or cells that neighboring TA1 and / or cell ID1 (in case of IIE-B idle mode mobility).

[0191] Based on the determining (of S807), the AMF may determine a list, wherein the list comprises at least one satellite ID (i.e., an ID of a satellite). In other examples, the list comprising the at least one satellite ID may instead be one of: information comprising the at least one satellite ID, a group comprising the at least one satellite ID, a set comprising the at least one satellite ID, or the like.

[0192] At S808, the AMF provides, to a RAN (e.g., network entity, or base station), a paging (message) comprising: the UE-Sat-UE indication, and an indication of at least one satellite ID (e.g., comprised in the list).

[0193] At S809, the RAN transmits, to UE-B, a paging message comprising: the UE-Sat-UE indication, and the indication of at least one satellite ID (e.g., comprised in list).

[0194] At S810, based on the paging message, the UE initiates an establishment of a connection to a first satellite. The first satellite is identified in the list.

[0195] In some examples, the identity of the first satellite is comprised in the list in the paging message, wherein the list comprises a plurality of satellites IDs. IIE-B selects the first satellite based on the list and a location of IIE-B. Information about the location of IIE-B is accessible to IIE-B (e.g., based on GPS, network positioning, etc.). The location of IIE-B may be considered to be a ‘current’ location of IIE-B (i.e., where the UE is currently located). For example, the information about the location of UE-B may indicate a tracking area (e.g., TA3) and / or a cell (e.g., cell ID2)

[0196] In some examples, the list further comprises information about at least one tracking area (TA) associated with each satellite ID (in the list). For example, the list identifies: ‘satellite IDT with ‘TAT, ‘satellite ID2’ with ‘TAT, and ‘satellite IDS’ with ‘TA3’. In another example, the list identifies: ‘satellite IDT with ‘TA1, TA2’, ‘satellite ID2’ with ‘TAT, and ‘satellite ID3’ with ‘TA1, TA3’. Based on the location of UE-B (e.g., a TA of UE-B), the UE determines a suitable satellite ID to connect to, based on the list.

[0197] In some examples, the list comprises a single satellite ID, e.g., the ID of the first satellite. In such an example, the UE refrains from performing a selection.

[0198] Based on (e.g., when) initiating the establishment of the connected to the first satellite, UE-B transitions from idle to connected mode / state.

[0199] At S811, once connected to the first satellite, the UE initiates a connection with UE-A for the IMS (protocol data unit, PDU) session via a UE-Sat-UE connection. Stated differently, the UE triggers a service request procedure to activate the IMS (PDU) session. For example, the service request procedure may follow TS 23.502, 4.2.3.2.

[0200] It should be understood that, in other examples, one or more of the signalling and operations in FIG. 8 may not be performed, or may be performed in a different order.

[0201] It should be understood that the signalling and operations of S800a to S800b in FIG. 8 are equally applicable to FIG. 7. S800a to S800b may take place before S701 in FIG. 7, in some examples.

[0202] FIG. 9 shows an example of a signalling and operations diagram for a user equipment to register satellite capabilities with a core network.

[0203] At S900, a user has subscribed for UE-Sat-UE communications, at an HSS. For example, preferences or configurations for a user indicates that the user can utilize UE-Sat-UE communications. A user account may allow a user to switch UE-Sat-UE communications ‘on’ or ‘off’.

[0204] At S901, a UE provides, to a P-CSCF, a request to register (or re-register) a capability of the UE for satellite redirection. The capability of the UE for satellite re-direction is related toIMS during IMS registration. The capability of the UE for satellite re-direction is used by IMS elements to trigger redirection.

[0205] At S902, the P-CSCF provides, to a serving CSCF (S-CSCF), a request to register the capability of satellite redirection for the UE.

[0206] At S903, the S-CSCF provides, to the HSS, a server assignment request (SAR) (alternatively referred to as a ‘Cx-pull’). ‘Cx’ is the name of the interface between an HSS and S-CSCF.

[0207] At S904, the HSS provides, to the S-CSCF, a response to the SAR of S903, wherein the response comprises an indication of satellite redirection. The response may alternatively be referred to as a ‘Cx-pull-Response’.

[0208] Furthermore, communications between the S-CSCF and an IMS AS for service control of third party registration with the IMS AS is performed.

[0209] At S905, the S-CSCF provides, to the P-CSCF, a response to the request of S902. The response indicates that the capability of the satellite redirection has been successfully registered.

[0210] At S906, the P-CSCF provides, to the UE, an indication that the capability of the satellite redirection has been successfully registered.

[0211] At S907, the P-CSCF provides, to the S-CSCF, a request to subscribe to events related to satellite redirection. The request may indicate a proxy ANI and information for a contact address.

[0212] At S908, based on the user being subscribed and has indicated for satellite redirection, then the S-CSCF provides, to the P-CSCF, an event notification.

[0213] At S909, based on the event notification, the P-CSCF determines that the UE is capable of satellite redirection.

[0214] The signalling and operations of FIG. 9 is given as an example only. In other examples, any suitable way of registering the capabilities of the UE may be utilized.

[0215] It should be understood that in some examples, one or more of the steps of FIG. 9 may not be performed, or may be performed in a different order.

[0216] One or more of the examples described above have the advantage that a terminating UE is able to receive an IMS session over satellite when the terminating UE is in an idle state. The termination UE is then able to connect to satellite access to complete a UE-Sat-UE call to optimize media routing. One or more of the examples allow the network (e.g., one or more network entities) to indicate to a UE to connect, via satellite, to an IMS session while the UE is in an idle state.

[0217] FIG. 10 shows an example method flow performed by an apparatus. In some examples, the apparatus may comprise a user equipment, be implemented as a user equipment, or may be comprised within a user equipment. The apparatus may comprise oneor more means for causing the apparatus to perform the operations of FIG. 10. The apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the operations of FIG.10. The apparatus may comprise circuitry configured to perform the operations of FIG. 10.

[0218] AtS1001, the method comprises: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state.

[0219] At S1013, the method comprises: based on the paging message, initiating an establishment of a connection to the first satellite.

[0220] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 10 and are performed by the apparatus. In some examples, one or more of the operations of FIG. 10 detailed above may not be performed, or may be performed in a different order.

[0221] FIG. 11 shows an example method flow performed by an apparatus. In some examples, the apparatus may comprise a network function (or network entity), be implemented as a network function (or network entity), or may be comprised within a network function (or network entity). For example, the network function (or network entity) may be an AMF. The apparatus may comprise one or more means for causing the apparatus to perform the operations of FIG.11. The apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the operations of FIG. 11. The apparatus may comprise circuitry configured to perform the operations of FIG. 11.

[0222] At S1101 , the method comprises: receiving, from a second network entity, an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment.

[0223] At S1103, the method comprises: based on the indication, determining an identity of a first satellite, wherein the first satellite is related to a location associated with the user equipment.

[0224] At S1105, the method comprises: initiating a transmission of a paging message to the user equipment, wherein the paging message comprises the indication that satellite access is requested for the IMS session and the identity of the first satellite.

[0225] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 11 and are performed by the apparatus. In some examples, one or more of the operations of FIG. 11 detailed above may not be performed, or may be performed in a different order.

[0226] FIG. 12 shows an example method flow performed by an apparatus. In some examples, the apparatus may comprise a network function (or network entity), be implementedas a network function (or network entity), or may be comprised within a network function (or network entity). For example, the network function (or network entity) may be one of: a PCF, a UDM, or HSS. The apparatus may comprise one or more means for causing the apparatus to perform the operations of FIG. 12. The apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the operations of FIG. 12. The apparatus may comprise circuitry configured to perform the operations of FIG. 12.

[0227] At S1201, the method comprises: receiving an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, fora user equipment.

[0228] At S1203, the method comprises: obtaining information that indicates that the user equipment is an idle state.

[0229] At S1205, the method comprises: providing, to a second network entity, the indication that satellite access is requested for the IMS session, for the user equipment.

[0230] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 12 and are performed by the apparatus. In some examples, one or more of the operations of FIG. 12 detailed above may not be performed, or may be performed in a different order.

[0231] FIG. 13 shows an example method flow performed by an apparatus. In some examples, the apparatus may comprise a user equipment, be implemented as a user equipment, or may be comprised within a user equipment. The apparatus may comprise one or more means for causing the apparatus to perform the operations of FIG. 13. The apparatus may comprise at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform the operations of FIG.13. The apparatus may comprise circuitry configured to perform the operations of FIG. 13.

[0232] AtS1301, the method comprises: receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and information that indicates identities

[0233] of a plurality of satellites, wherein the user equipment is in an idle state.

[0234] At S1303, the method comprises: selecting a first satellite from the plurality of satellites based on the paging message and information about a location of the user equipment.

[0235] At S1305, the method comprises: based on the paging message, initiating an establishment of a connection to the first satellite.

[0236] It should be understood that, in some examples, one or more additional method steps are included in the method flow of FIG. 13 and are performed by the apparatus. In some examples, one or more of the operations of FIG. 13 detailed above may not be performed, or may be performed in a different order.

[0237] FIG. 14 shows an example of a schematic representation of an apparatus. FIG. 14 shows, by way of example, a block diagram of an apparatus 10. The apparatus 10 comprises, for example, at least one processor 12 and at least one memory 14 storing instructions 15 that, when executed by the at least one processor, cause the apparatus 10 at least to perform the method or methods as disclosed herein, and any of the embodiments thereof. In an example, the at least one memory and the instructions (e.g. program code, software), are configured, with the at least one processor, to cause the apparatus 10 to perform the method or methods as disclosed herein, and any of the embodiments thereof.

[0238] A processor 12 may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this disclosure, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in analog, digital and / or quantum circuitry, and (b) combinations of hardware circuit(s) and software, such as, as applicable: (i) a combination of analog, digital and / or quantum hardware circuit(s) with software / firmware and (ii) any or all portions of hardware processor(s) (including digital and / or quantum processor(s)) with software, and memory(ies) that work together to cause an apparatus, such as a user equipment, computing device, or server to perform various functions) and (c) any or all portions of hardware circuit(s), such as a microprocessor(s), processor(s) and / or quantum processor(s), that require software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this disclosure, the term “circuitry” also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term “circuitry” also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0239] The memory 14 may be implemented using any suitable data storage technology. The memory may comprise a database for storing data. The memory 14 may be at least in part external to apparatus 10 but accessible to apparatus 10.

[0240] The instructions 15 may be comprised in a computer readable medium or a non-transitory computer readable medium. A term “non-transitory,” as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. random access memory, RAM, vs. read only memory, ROM).

[0241] For example, the apparatus 10 is implemented as a terminal device, such as the UE of FIG. 7, FIG. 8 or FIG. 9. As another example, the apparatus is comprised in such a terminal device, e.g. as a chipset configured to control the terminal device. As another example, theapparatus comprises a terminal device, such as the UE of FIG. 7, FIG. 8 or FIG. 9. In any event, the apparatus 10 may be caused or configured to perform at least the method of FIG.10 or FIG. 13 and / or any one or more of the examples described in this disclosure.

[0242] As another example, the apparatus 10 is implemented as a network entity, e.g. the network entity of FIG. 7, FIG. 8, or FIG. 9. In another embodiment, the apparatus is comprised in such a network entity, e.g. as a chipset configured to control the network entity. As another example, the apparatus comprises a network entity. In any event, the apparatus 10 may be caused or configured to perform at least the method of any of FIGS. 11 to 13 and / or any one or more of the examples described in this disclosure.

[0243] The apparatus 10 comprises a radio interface 16. The radio interface 16 may provide the apparatus 10 with communication capabilities. The radio interface 16 may comprise a receiver configured to receive information in accordance with at least one cellular or non-cellular standard. The radio interface 16 may comprise a transmitter configured to transmit information in accordance with at least one cellular or non-cellular standard. The receiver may comprise more than one receiver. The transmitter may comprise more than one transmitter. The radio interface 16 may comprise a transceiver configured to receive and transmit information in accordance with at least one cellular or non-cellular standard. The transceiver may comprise more than one transceiver.

[0244] The apparatus 10 may comprise an interface (e.g., user interface) 18 comprising, for example, at least one of a keypad, a microphone, a touch display, a display, or a speaker etc. The 18 may be used to control the apparatus by the user. The interface 18 may be external to the apparatus 10. For example, the apparatus 10 may be connected to another device, such as a computer, either via wireless or wired connection, and the apparatus 10 is controlled by the user via the computer.

[0245] In some examples, at least some of the processes described herein may be carried out by an apparatus comprising means for carrying out at least some of the described processes. Means for performing method steps as disclosed herein may include software and / or hardware components of the apparatus 10. For example, the at least one processor 12, the memory 14, and the program (e.g. computer program) code form means for carrying out the method or methods as disclosed herein, and any of the embodiments thereof. As used herein the term “means” is to be construed in singular form, i.e. referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore, terminology “means for [performing A, B, C]”, is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology “means for performing A, means for performing B, means for performing C” is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or wherethere are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. It is noted that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present disclosure.

[0246] The examples may thus vary within the scope of the attached claims. In general, some embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although embodiments are not limited thereto. While various examples may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it will be apparent to those skilled in the relevant art(s) that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting and illustrative examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0247] The examples may be implemented by computer software stored in a memory and executable by at least one data processor of the involved entities or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that any procedures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD.

[0248] The term “non-transitory”, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. RAM vs ROM).

[0249] As used herein, “at least one of the following:” and “at least one of: ” and similar wording, where the list of two or more elements are joined by “and”, or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0250] The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs),application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

[0251] As used herein, the terms “means for”, “means for performing operations including”, “means configured to perform operations including”, or “means configured to perform” (or similar) may be any means that are suitable for performing the feature(s). The “means” may be configured to perform one or more of the functions and / or method steps previously described. For example, the “means” may include one or more of: at least one processor, at least one memory, transceiver circuitry, antenna circuitry, etc. It should be understood that these are provided as non-limiting examples.

[0252] Alternatively, or additionally some examples may be implemented using circuitry. The circuitry may be configured to perform one or more of the functions and / or method steps previously described. That circuitry may be provided in the base station and / or in the communications device.

[0253] This definition of circuitry applies to uses of the term “means” in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example an integrated device. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0254] The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of some examples of this disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant art(s) in view of this disclosure, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings will still fall within the scope as defined in the appended claims.

Claims

Claims:

1. A method performed by a user equipment, UE, the method comprising:receiving a paging message comprising an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, and an identity of a first satellite, wherein the user equipment is in an idle state; andbased on the paging message, initiating an establishment of a connection to the first satellite.

2. The method according to claim 1, wherein the method further comprises:transmitting, to a base station, a first indication that the user equipment supports internet protocol multimedia subsystem, IMS, over satellite.

3. The method according to claim 1 or claim 2, wherein the method further comprises:transmitting, to the base station, a second indication that UE-to-satellite-to-UE, UE- Sat-LIE, is preferred for IMS.

4. The method according to claim 2 or claim 3, wherein at least one of: the first indication, or the second indication, are included in subscription data for the user equipment.

5. The method according to any of claims 1 to 4, wherein the identity of the first satellite is comprised in a list in the paging message.

6. The method according to any of claims 1 to 5, the method further comprises:based on connecting to the first satellite, initiating a connection with an originating UE for the IMS session via a UE-Sat-UE connection.

7. The method according to any of claims 1 to 6, wherein the initiating of the establishment of the connection to the first satellite comprises re-establishing a deactivated IMS session of the UE that was deactivated based on the UE moving to the idle state.

8. The method according to claim 7, wherein the initiating of the connection with the originating UE is based on the indication that satellite access is requested for the IMS session.

9. The method according to any of claims 1 to 8, wherein the method further comprises: based on the initiating of the establishment of the connection to the first satellite, transitioning from the idle state to a connected state.3310. A method performed by a first network entity, wherein the method comprises: receiving, from a second network entity, an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment;based on the indication, determining an identity of a first satellite, wherein the first satellite is related to a location associated with the user equipment; andinitiating a transmission of a paging message to the user equipment, wherein the paging message comprises the indication that satellite access is requested for the IMS session and the identity of the first satellite.

11. The method according to claim 10, wherein the determining of the identity of the first satellite comprises:obtaining information about the location associated with the user equipment; and determining the identity of the first satellite based on the information, wherein the first satellite provides a cell for the location associated with the user equipment.

12. The method according to claim 10 or claim 11, wherein the location associated with the user equipment comprises an indication of a cell or tracking area for the user equipment before the user equipment went into idle mode.

13. A method performed by a second network entity, the method comprising:receiving an indication that satellite access is requested for an internet protocol multimedia subsystem, IMS, session, for a user equipment;obtaining information that indicates that the user equipment is an idle state; providing, to a second network entity, the indication that satellite access is requested for the IMS session, for the user equipment.

14. The method according to claim 13, wherein the providing of the indication is based on the information that indicates that the user equipment is an idle state.

15. The method according to claim 13 or claim 14, wherein the method further comprises:obtaining information that the user equipment supports IMS over satellite access; and based on the information that the user equipment supports IMS over satellite access, providing, to the first network entity, an indication of the support for IMS over satellite access for the user equipment and a request for information about a radio access technology for the user equipment.

16. The method according to claim 13, wherein the method further comprises: receiving, from a session management function, an indication that the user equipment has connected to a satellite with an identity of a first satellite; andbased on the indication, providing, to a call session control function, a notification that the user equipment has connected to a satellite with the identity of the first satellite.

17. The method according to any of claims 10 to 16, wherein the first network entity is an access and mobility management function, AMF.

18. The method according to any of claims 10 to 17, wherein the second network entity is one of: a policy control function, PCF, a unified data repository, UDM, or a home subscriber server, HSS.

19. A user equipment comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to perform the method of any of claims 1 to 9.

20. A user equipment comprising: means for causing the user equipment to perform the method of any of claims 1 to 9.

Images