Patent Description:
Furthermore, the present invention relates to a user equipment for being operated with a radio access network of a mobile communication network, wherein the user equipment is enabled to be simultaneously connected to different mobile communication networks that have, or use, different pieces of network identifier information, wherein such different mobile communication networks comprise a first mobile communication network and, at least, a second mobile communication network, wherein the user equipment is enabled to be registered, using a first connection, to the first mobile communication network, and wherein the user equipment is furthermore enabled to be also registered, using a second connection, to at least the second mobile communication network.

Additionally, the present invention relates to a system or a mobile communication network for operating a user equipment with a radio access network of a mobile communication network, wherein the user equipment is enabled to be simultaneously connected to different mobile communication networks that have, or use, different pieces of network identifier information.

Furthermore, the present invention relates to a program and to a computer-readable medium for operating a user equipment with a radio access network of a mobile communication network according to the inventive method.

In currently deployed mobile communication networks, it is possible that a user equipment is independently connecting to different mobile communication networks, as well as to a single network using simultaneously different access technologies, e.g., simultaneously via or using a 3GPP access and non-3GPP access. It is, however, not possible to efficiently realize integrated connectivity via two different networks simultaneously, also called dual steering, or multiple networks. Document <CIT> as an example describes an apparatus, a method and a system for steering a device to networks supporting specific network slices.

Possible use cases include, e.g., that the user equipment is simultaneously connecting to a non-terrestrial network (e.g. a satellite-based network) and a terrestrial public land mobile network. Typically such networks have (or use) a different network identifier, such as a public land mobile network identifier information (PLMN IDs) or combination of PLMN ID and network identifier (NID). Furthermore, the user equipment should be enabled to simultaneously connect to such different mobile communication networks using a single set of credentials. , the user equipment might be simultaneously in its home mobile communication network (or home PLMN) and, simultaneously, roaming in another mobile communication network.

However, regarding the following situations or scenarios, such dual steering might be failing:.

Hence, even though in principle a dual steering functionality is able to be realized, there is a considerable number of technical problems and/or situations or scenarios possible where such dual steering (or multiple steering) and/or network connectivity is not able to be effectively deployed.

An object of the present invention is to provide a technically simple, effective and cost-effective solution for operating a user equipment with a radio access network of a mobile communication network such that the user equipment - in case the preconditions are met - is not only theoretically enabled but actually enabled to be simultaneously connected to different mobile communication networks that have, or use, different pieces of network identifier information, and wherein furthermore unnecessary attempts to realize or set up dual (or multiple) steering are able to be avoided in cases where such preconditions are not met. A further object of the present invention is to provide a corresponding user equipment, system or mobile communication network, and a corresponding program and computer-readable medium.

The object of the present invention is achieved by a method for operating a user equipment with a radio access network of a mobile communication network according to the features of claim <NUM>.

Especially by means of the user equipment transmitting the capability indication information, and by the user equipment receiving the multiple registration information, it is advantageously possible, according to the present invention, that involved entities are aware of the capabilities and/or limitations (regarding dual steering or multiple steering) of the respective other party, entity or network such as to be able to use, actually and in practice, dual steering (or multiple steering) where this is applicable, especially technically feasible as well as permitted - and, as a consequence, also to be able to efficiently initiate such dual or multiple steering functionality where it is possible -, and to avoid wasting network resources, energy and user equipment resources in trying to initiate dual steering or multiple steering in situations where the respective conditions or requirements are not fulfilled. Hence, according to the present invention, it is advantageously possible to provide a solution how dual steering and multiple steering is able to be applied in practice in an efficient manner (and, especially, attempt to apply such functionality only in cases where, really, the prerequisites are met), and nevertheless provide a backwards-compatible solution, such that a mobile communication network can support both newer user equipments supporting this capability as well as legacy user equipments (e.g. Release <NUM> and below) that typically do not support this capability. Hence, according to the present invention, it is advantageously possible to add such new functionality of dual steering and/or multiple steering to a mobile communication network in a backwards-compatible manner, i.e. without the consequence that legacy user equipments are impaired.

According to the present invention it is supposed that a user equipment is operated with a radio access network of a mobile communication network. It is furthermore supposed that the user equipment is enabled to be simultaneously connected to different mobile communication networks that have, or use, different pieces of network identifier information. In the context of the present invention, such different mobile communication networks are called a first mobile communication network and, at least, a second mobile communication network. The (considered) user equipment being connected, simultaneously, to two different of such mobile communication networks relates to the so-called dual steering functionality, whereas the (considered) user equipment being connected, simultaneously, to three (or even more) different of such mobile communication networks relates to the so-called multiple steering functionality. All realistically conceivable solutions are addressed according to the present invention, i.e. the use of two mobile communication networks, three mobile communication networks, four mobile communication networks, five mobile communication networks, etc. Hence, according to the present invention, the (considered) user equipment is enabled to be registered, using a first connection, to the first mobile communication network, and it is further enabled to be also registered, using a second connection, to at least the second mobile communication network. Of course, using a third connection, the (considered) user equipment might also be registered to a third mobile communication network. However, the use of such ordinal number (first, second, third mobile communication network, or, first, second, third connection) does not imply a priority or an order of precedence or whether one network is of different relative importance than the other, but merely a means to differentiate and to distinguish the different mobile communication networks or connections: For example, using a 'second connection' (with a second mobile communication network) a user equipment might exchange more data or more important or more critical data or be provided, correspondingly, with more important or more high-volume communication services instead of using a 'first connection' and a first mobile communication network. However, temporally speaking, from a user equipment not being connected at all to the user equipment having both the first and the second connection established, there will typically be one of the connections established first and the other one later. According to the present invention, in order to be able to actually apply and use dual or multiple steering functionality in practice, it is proposed that the involved entities are mutually informed about the capabilities of the other entity, respectively, especially by means of the user equipment, in a first step, transmitting the capability indication information (the capability indication information comprising at least the piece of information of whether the user equipment supports, or is enabled, to establish both the first connection and the second connection, i.e. supports dual steering functionality) towards, typically, a network node of either the first or the second mobile communication network, and, in a second step, the user equipment receiving the multiple registration information (the multiple registration information comprising at least the piece of information of whether the user equipment is allowed to establish both the first connection and the second connection), likewise typically from a network node of either the first or the second mobile communication network (especially from the one mobile communication network whose network node did receive the capability indication information.

Hence, according to the present invention, it is proposed to introduce a user equipment capability indication and network steering in order to include a dual/multiple steering indication from the user equipment to the mobile communication network (to which the user equipment is connected); typically, the respective mobile communication network decides which multiple access combinations are allowed regarding the requesting user equipment, especially based on the (capability) indication (information) the user equipment did send, the mobile communication network's capability, the subscriber information (e.g. whether the subscriber is allowed, and if yes, how, to dual/multiple connectivity), the existing inter-network agreements and/or available connectivity, as well as the regulatory requirements (e.g. location). As a result thereof, the mobile communication network sends (using the multiple registration information) the allowed combinations to the user equipment (i.e. the combination restrictions), and the user equipment applies the combination restrictions when using multiple network connectivity. It is furthermore proposed according to the present invention that such information or indication is forwarded between networks (especially in the roaming case).

In conventionally known telecommunications networks or mobile communication networks, use cases and scenarios for multiple connectivity of user equipments are already known, e.g. in the following scenarios:.

According to the present invention, it is advantageously possible and preferred that, in a third step subsequent to the second step, the user equipment is simultaneously connected to the first and second mobile communication network using the first and second connection and using a set of credentials,.

It is thereby advantageously possible to realize and implement the inventive method in a comparatively simple and efficient manner.

According to the present invention, it is advantageously furthermore possible and preferred that the set of credentials used by the user equipment refers to a single set of credentials to connect to both the first mobile communication network and the second mobile communication network, wherein the single set of credentials refers to the first mobile communication network, or to the second mobile communication network or even to a third mobile communication network. Furthermore, it is advantageously furthermore possible and preferred that, as opposed to current multi-SIM functionality, when more than one set of credentials is used, a network can steer the multiple connectivity of user equipments, as opposed to having independent network connections.

It is possible that the user equipment transmits the capability indication information, especially as part of a registration request message, according to one or a plurality of the following possibilities:.

wherein the user equipment receives the multiple registration information, especially as part of a registration accept message and/or as part of a UE configuration update, UCU, message and/or as part of a parameter update, UPU, message and/or as part of an access network discovery and selection policy, ANDSP, message and/or as a steering of roaming, SoR, message, according to one or a plurality of the following possibilities:.

According to the present invention, it is furthermore advantageously possible and preferred that the user equipment transmits the capability indication information as part of at least one out of the following:.

Furthermore, according to the present invention the capability indication information comprises information regarding the first mobile communication network when connecting to the second network, especially regarding the radio access network of the first network and/or information informing the second network that it is already connected to the first network.

Furthermore, it is advantageously possible and preferred according to the present invention that the capability indication information comprises - besides the piece of information of whether the user equipment supports, or is enabled, to establish both the first connection and the second connection - at least one out of the following:.

wherein especially, the capability indication information refers to a pre-defined table of types of capabilities, each of such types of capabilities being defined as comprising capability aspects regarding different capability dimensions.

Furthermore, it is advantageously possible and preferred according to the present invention that the multiple registration information comprises - besides the piece of information of whether the user equipment is allowed to establish both the first connection and the second connection - at least one out of the following:.

Furthermore, it is advantageously possible and preferred according to the present invention that, in a fourth step subsequent to the second step, the user equipment receives a further multiple registration information, wherein the user equipment replaces the multiple registration information received in the second step with the further multiple registration information.

Furthermore, it is advantageously possible and preferred according to the present invention that - as part of a mobile communication network, especially a core network thereof, comprising network functions or services - network function capability indication information is.

wherein the network function capability indication information is especially part of a profile information of the respective network function or service.

Furthermore, it is advantageously possible and preferred according to the present invention that - in case of a roaming situation of the user equipment, which includes as well a roaming-like situation in which a roaming architecture is used (e.g. the use of the roaming architecture to interconnect between a PLMN and an SNPN), where user equipment is connected to a visited mobile communication network - the capability indication information, transmitted by the user equipment, is received, besides by the home mobile communication network of the user equipment, also by the visited mobile communication network of the user equipment, and, if applicable, also by one or a plurality of intermediate mobile communication networks that are connecting the visited mobile communication network and the home mobile communication network of the user equipment.

Furthermore, the present invention relates to a user equipment for being operated with a radio access network of a mobile communication network according to the features of claim <NUM>.

Furthermore, the present invention relates to a system or mobile communication network for operating a user equipment with a radio access network of a mobile communication network according to the features of claim <NUM>.

Additionally, the present invention relates to a program comprising a computer readable program code which, when executed on a computer and/or on a user equipment and/or on a network node of a mobile communication network, or in part on a user equipment and/or in part on network node of a mobile communication network, causes the computer and/or the user equipment and/or the network node of the mobile communication network to perform the inventive method.

Still additionally, the present invention relates to a computer-readable medium comprising instructions which when executed on a computer and/or on a user equipment and/or on a network node of a mobile communication network, or in part on a user equipment and/or in part on network node of a mobile communication network, causes the computer and/or the user equipment and/or the network node of the mobile communication network to perform the inventive method.

The present invention will be described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto but only by the claims.

In <FIG>, a user equipment <NUM> is schematically shown in a radio environment such as to be able to be potentially connected to different mobile communication networks - exemplarily shown, in <FIG>, as a terrestrial mobile communication network <NUM> and a non-terrestrial mobile communication network <NUM> - called, in the context of the present invention, a first mobile communication network <NUM> and a second mobile communication network <NUM>. The first mobile communication network <NUM> comprises an access network <NUM> or a radio access network <NUM>, and a core network <NUM>. The telecommunications network <NUM> or also mobile communication network <NUM> is typically realized as a cellular network or cellular mobile communication network <NUM>. The mobile communication network <NUM>, especially the core network <NUM>, typically comprises a number of network functions or services that are not specifically indicated by means of a reference sign. The (radio) access network <NUM> comprises a plurality of radio cells <NUM>, <NUM>, i.e. geographical areas served, respectively, by base station entities. In the exemplary situation or scenario shown in <FIG>, a first base station entity <NUM> generates or is associated with or spans the first (terrestrial) radio cell <NUM>, and a second base station entity <NUM> generates or is associated with or spans the second (terrestrial) radio cell <NUM> (the first and second (terrestrial) radio cells <NUM>, <NUM> being represented, in <FIG>, by means of dashed circles around the first and second base station entities <NUM>, <NUM>, respectively). The base station entities <NUM>, <NUM> typically realize gNB functionality or next-generation gNB functionality. The mobile communication network <NUM> is typically connected to a plurality of user equipments (or, rather, the user equipments are connected to the telecommunications network <NUM>). <FIG> schematically only shows one user equipment <NUM>, i.e. the situation of that user equipment <NUM> is represented in the communication network <NUM>, whose (above mentioned) radio access network <NUM> is realized as a terrestrial radio access network <NUM>, i.e. the radio access network <NUM> realizes the terrestrial radio access network (part) of the mobile communication network <NUM> (that is able to provide the user equipment <NUM> with radio access network functionality).

<FIG> additionally shows a second mobile communication network <NUM> in the form of a non-terrestrial network, i.e. comprising a non-terrestrial radio access network <NUM> which is preferably realized, according to the present invention, by means of (or as) a satellite radio access network or satellite non-terrestrial radio access network. The second mobile communication network <NUM> furthermore comprises a (second) core network <NUM>. The second mobile communication network <NUM> (exemplarily shown as a non-terrestrial mobile communication network) likewise comprises base station entities that are schematically and exemplarily represented, in <FIG>, as a first satellite <NUM>' and a second satellite <NUM>', wherein the first satellite <NUM>' provides radio coverage in a first satellite (or non-terrestrial) radio cell <NUM>' and the second satellite <NUM>' provides radio coverage in a second satellite (or non-terrestrial) radio cell <NUM>' (the first and second satellite (non-terrestrial) radio cells <NUM>', <NUM>' being represented, in <FIG>, by means of dotted circles around the first and second satellites <NUM>', <NUM>', respectively).

In any case, the user equipment <NUM> is able to be provided with radio access network functionality and network connectivity by both the first mobile communication network <NUM> and by means of the second mobile communication network <NUM>.

Hence, the user equipment <NUM> is schematically shown in a radio environment comprising a plurality of radio cells of a plurality of mobile communication networks <NUM>, <NUM>. Of course, in addition to the first and second mobile communication networks <NUM>, <NUM>, an additional third mobile communication network, or still further mobile communication networks, might be available to the user equipment <NUM>.

In such a situation of a user equipment <NUM>, in conventionally known mobile communication networks, there already exists the possibility that such a user equipment <NUM> is connecting to such different mobile communication networks <NUM>, <NUM> simultaneously via or using a 3GPP access - also called dual steering or multiple steering; such mobile communication networks <NUM>, <NUM> typically have (or use) different pieces of network identifier, such as a public land mobile network identifier information (PLMN IDs) or combination of PLMN ID and network identifier (NID). Furthermore, the user equipment <NUM> should preferably be enabled to simultaneously connect to such different mobile communication networks <NUM>, <NUM> using a single set of credentials.

However, despite such dual (or multiple) steering functionality being possible, in principle, a considerable number of possible hindrances or technical problems and/or situations or scenarios exist where such dual steering (or multiple steering) and/or network connectivity is either not able to be used at all, or, at least, not able to be used efficiently.

Such situations include cases where some user equipments support connectivity to multiple networks (or dual steering) - and some user equipments do not; e.g., due to different modem support and/or capability to maintain more than one registration simultaneously. Furthermore, within a user equipment that supports dual steering, there might be support for some dual steering scenarios but not for others; e.g. support for dual steering in a satellite/terrestrial scenario could exist but not for a satellite/satellite scenario (for example due to hardware limitations); or, support for a dual steering PLMN/PLMN scenario could exist but not for a PLMN/SNPN (standalone non-public network) scenario (for example due to a lack of standalone non-public network support). Furthermore, support for dual steering / multiple steering might differ as to the number of simultaneous registrations: e.g. one user equipment supports two mobile communication networks, and another user equipment supports three mobile communication networks. Furthermore, the subscriber identity module (SIM card) or universal integrated circuit card may support only certain combinations of networks or scenarios of dual steering but not others, e.g. due to not being able to support multiple state machines for a single set of keys. Furthermore, even in case a user equipment, in principle, supports dual steering, there might be obstacles to its applications, relating to the subscriber not being allowed to realize certain combinations, or relating to the home network not supporting dual steering functionality, or, in case of roaming, relating to the visited or the home network not supporting dual steering functionality (e.g., for either home or visited network because of regulatory requirements).

Hence, even though, in principle, a dual steering functionality is able to be realized in conventionally known mobile communication networks, there is nevertheless a considerable number of technical problems and/or situations or scenarios possible where such dual steering (or multiple steering) and/or corresponding network connectivity is not able to be effectively deployed, especially due to limitations (to the application of dual or multiple steering) that are somewhat hidden to entities that would be involved in such functionality.

According to the present invention, it is suggested to provide useful information - to the entities communicating with each other (or cooperating) in order to realize such dual/multiple steering functionality - or, rather, to exchange such information between such entities. Especially, the present invention aims at providing the mobile communication network <NUM>, <NUM> (to which the considered user equipment <NUM> is connected or registered) information regarding the capability of the considered user equipment <NUM> to connect to multiple networks. Additionally, the mobile communication network <NUM>, <NUM> shall be provided with useful information from other sources regarding its own capability to support dual or multiple connectivity. Additionally, an answer, or response, of the mobile communication network <NUM>, <NUM> and towards the considered user equipment <NUM> is proposed to be defined, as well as the behavior of the user equipment <NUM>.

Hence, according to the present invention, it is supposed that the user equipment <NUM> is enabled to be simultaneously connected to different mobile communication networks <NUM>, <NUM> (such mobile communication networks <NUM>, <NUM> having, or using, different pieces of network identifier information, PLMN IDs). In order to use the user equipment <NUM> with either one, or both, of the first and/or second mobile communication networks <NUM>, <NUM>, the user equipment <NUM> transmits a capability indication information and receives a multiple registration information, especially in this order; however, according to further variants or embodiments of the present invention, this order might also be reversed (i.e. that the user equipment <NUM> receives the multiple registration information first and transmits the capability indication information later).

The capability indication information comprises at least the piece of information of whether the user equipment <NUM> supports, or is enabled, for dual/multiple steering (i.e. able to establish both the first connection and the second connection), whereas the multiple registration information comprises at least the piece of information of whether the user equipment <NUM> is allowed to use dual/multiple steering (i.e. establish both the first connection and the second connection).

Typically, and as a result of the user equipment <NUM> transmitting the capability indication information and receiving the multiple registration information, in a subsequent third step, the dual or multiple steering is actually realized or implemented by means of the user equipment <NUM> being simultaneously connected to both the first and the second mobile communication networks <NUM>, <NUM> using the first and second connection, and especially using a set of credentials (especially one single set of credentials).

This is schematically shown in <FIG> which illustrates a communication diagram of the user equipment <NUM> transmitting the capability indication information relating to its capabilities (to conduct dual/multiple steering, or simultaneously connect to different mobile communication networks <NUM>, <NUM>), and the user equipment receiving (from either the respective core network - in the exemplary representation of <FIG>, the first mobile communication network <NUM> and its core network <NUM> is exemplarily illustrated - or from the respective radio access network - again, in the exemplary representation of <FIG>, the first mobile communication network <NUM> and its radio access network <NUM>, or, rather, a base station entity <NUM> as part of its radio access network <NUM> is exemplarily illustrated) the multiple registration information (relating to whether the user equipment <NUM> is allowed to establish certain connections).

In a first processing step <NUM>, the considered user equipment <NUM> is aware of its ('own', i.e. hardware-related or device-related or subscriber identity module card-related) capabilities (and, especially, its limitations regarding such capabilities) concerning dual/multiple steering functionality. Hence, the (dual/multiple steering) capability is known to the user equipment <NUM>, e.g. the user equipment's <NUM> capability could be limited by the hardware capabilities of the user equipment <NUM> (and said information is part of the user equipment's <NUM> characteristics, e.g. set by the user equipment <NUM> vendor) or by the SIM card's capabilities (which the user equipment <NUM>, e.g., (previously) queried and which is, thus, known to it) or the user equipment's <NUM> capability is stored in a configuration parameter in the user equipment <NUM> and/or the SIM card, typically configured by the (home network) operator (again which the user equipment <NUM>, e.g., (previously) queried and which is, thus. known to it).

In a second processing step <NUM>, the user equipment <NUM> transmits the capability indication information to an entity or network node of the radio access network <NUM> and/or to an entity or network node of the core network <NUM>; in the exemplary embodiment shown in <FIG>, such capability indication information is transmitted, by the user equipment <NUM>, as part of a registration request (message). Hence, in this exemplary embodiment, the user equipment <NUM> performs a registration request and includes the capability indication (information); especially, there are two preferred placements of the capability indication (information) considered (as it is important to indicate the support on both the radio level (between UE and RAN, i.e. access stratum, AS, communication) and on the non-access stratum, NAS, level (between UE and CN)): the user equipment radio capability handling (the user equipment radio capability information especially contains information on radio access technologies that the user equipment supports, e.g. power class, frequency bands, etc.) and the user equipment mobility management core network capability handling (the user equipment mobility management core network capability is split into the S1 user equipment network capability (mostly for E-UTRAN access related core network parameters) and the user equipment <NUM> mobility management core network capability (mostly to include other user equipment capabilities related to <NUM> core network or interworking with EPS) and contains non radio-related capabilities, e.g. the non-access stratum security algorithms, etc.).

In a third processing step <NUM>, the user equipment <NUM> is registered, i.e. the user equipment registration procedure is performed, mainly by the respective or concerned network functions or services of the core network, especially the access and mobility management function, AMF, the authentication server function, AUSF, and/or the unified data management function, UDM. Hence, the core network <NUM> performs the user equipment registration as required and additionally evaluates the support of simultaneous registration to multiple networks for the specific UE.

In a fourth processing step <NUM>, the user equipment <NUM> receives the multiple registration information from an entity or network node of the radio access network <NUM> and/or from an entity or network node of the core network <NUM>; in the exemplary embodiment shown in <FIG>, such multiple registration information is transmitted, by the mobile communication network <NUM>, as part of a registration accept (message). Thus, the core network <NUM> responds in the registration accept (message) including the dual/multiple registration information, which includes whether and/or in what combinations multiple simultaneous registrations are allowed.

Hence, especially, the capability indication (information) is transmitted as part of registration procedure, and the capability indication information comprises the indication whether, and if yes, in what form, the user equipment <NUM> supports simultaneous registrations to multiple networks - such simultaneous registrations to multiple network typically being conducted with (or using) a single set of credentials as using multiple subscriber identity modules for registration to independently register to multiple networks would substantially correspond to existing multi-SIM functionality.

After receiving the multiple registration information, the user equipment <NUM> is able to simultaneously connected to the first and second mobile communication network <NUM>, <NUM> using the first and second connection, thereby realizing, or executing, the third step of the inventive method according to the present invention.

In <FIG>, what is exemplarily represented is a communication (as part of a registration procedure) between the user equipment <NUM> and the first mobile communication network <NUM> (i.e. its radio access network <NUM> and/or its core network <NUM>) in order for the user equipment <NUM> to transmit the capability indication information and to receive the multiple registration information; however, as has already been stated and as the use of ordinal numbers regarding different mobile communication networks is merely a means to differentiate or distinguish these networks, the communication of the user equipment <NUM> could also have been with the 'second' mobile communication network <NUM> instead of the first. In either case, the content of the capability indication information and/or of the multiple registration information might be shared between the respective networks; alternatively or cumulatively, upon the user equipment <NUM> having transmitted the capability indication information and received the multiple registration information from one of the networks, a corresponding communication - i.e. the transmission of a (further) capability indication information and the reception of a (further) multiple registration information; e.g. also as part of a registration procedure, e.g. as part of the third step according to (the method of) the present invention - might also be performed with the other one of the mobile communication networks involved. It is further revealed, as not part of the invention, that the user equipment <NUM> transmits the capability indication information, especially as part of a registration request message, according to one or a plurality of the following possibilities:.

and/or the user equipment <NUM> receives the multiple registration information, especially as part of a registration accept message and/or as part of a UE configuration update, UCU, message and/or as part of a parameter update, UPU, message and/or as part of an access network discovery and selection policy, ANDSP, message and/or as a steering of roaming, SoR, message, according to one or a plurality of the following possibilities:.

According to the present invention, the (further) capability indication information - transmitted to the second mobile communication network <NUM> - comprises information regarding the first mobile communication network when connecting to the second mobile communication network <NUM>, especially regarding the radio access network of the first mobile communication network <NUM> and/or information informing the second mobile communication network <NUM> that the user equipment <NUM> is already connected to the first mobile communication network <NUM>.

Preferably according to the present invention, either prior to the third step or subsequent to the third step (of the inventive method) - and especially repeatedly - the conditions for using the first and second connection are evaluated (either by the user equipment <NUM>, or by the first and/or second mobile communication network <NUM>, <NUM>, or by both the user equipment <NUM> and the first and/or second mobile communication network <NUM>, <NUM>); i.e. in case of a change (e.g. of the location of the user equipment <NUM>) that influences whether the conditions to respect are met, the dual or multiple steering functionality might be altered (e.g. another mobile communication network involved), or stopped (i.e. the user equipment <NUM> would have only one connection, either the first connection or the second connection).

Furthermore, it is advantageously possible and preferred according to the present invention that, in a fourth step subsequent to the second step, the user equipment <NUM> receives a further multiple registration information, wherein the user equipment <NUM> replaces the multiple registration information received in the second step with (or by) the further multiple registration information; thus, the further multiple registration information might be regarded as an updated version of the multiple registration information previously received by the user equipment <NUM>.

According to the present invention, the information content of the capability indication information, or considered in dual/multiple registration capability indication, especially corresponds to at least one out of the following:.

Especially, according to the present invention is advantageously possible that instead of having to explicitly include each parameter, the user equipment <NUM> may use of a pre-defined table of capabilities, such that signaling can be optimized and the scope simplified, e.g. "capability-type-<NUM>" being equivalent to a specific combination of parameters.

Hence, the capability indication information comprises - besides the piece of information of whether the user equipment <NUM> supports, or is enabled, to establish both the first connection and the second connection - at least one out of the following:.

According to the present invention, the information content of the multiple registration information, or considered in the dual/multiple registration information, especially corresponds to at least one out of the following:.

In order to fulfill regulatory requirements, the network may need to constrain connectivity to multiple networks to certain locations (e.g. countries) and/or times. To realize such requirements, it is proposed, according to the present invention,.

Hence, the multiple registration information comprises - besides the piece of information of whether the user equipment <NUM> is allowed to establish both the first connection and the second connection - at least one out of the following:.

As has been mentioned, either prior to the third step or subsequent to the third step (of the inventive method) - and especially repeatedly - the conditions for using the first and second connection are evaluated. Possible and preferred implementations regarding such updating or evaluation of conditions are schematically shown in <FIG>, which illustrate examples of communication diagrams of the user equipment <NUM> transmitting the capability indication information to the mobile communication network <NUM>, and the user equipment <NUM> receiving the multiple registration information as well as how the resulting dual or multiple connection of the user equipment <NUM> is able to be applied:
Both <FIG> schematically show the second processing step <NUM> (i.e. the user equipment <NUM> transmitting the capability indication information to an entity or network node of the radio access network <NUM> and/or to an entity or network node of the core network <NUM> of the mobile communication network <NUM>, especially as part of a registration request message) and the fourth processing steps <NUM> (i.e. the user equipment <NUM> receiving the multiple registration information from an entity or network node of the radio access network <NUM> and/or from an entity or network node of the core network <NUM> of the mobile communication network <NUM>, especially as part of a registration accept message) as represented in <FIG>. In the exemplary embodiment represented in <FIG>, in a fifth processing step <NUM> (subsequent to the fourth processing step <NUM>), it is the user equipment <NUM> that evaluates the conditions (regarding dual/multiple steering) as received by means of the multiple registration information from the mobile communication network <NUM> (UE-based conditional evaluation of dual/multiple registration information), and, subsequently and in a sixth processing step <NUM>, applies these conditions regarding the dual or multiple steering functionality, i.e. it is simultaneously connected to the first and second mobile communication networks <NUM>, <NUM>, and thereby realizes, or executes, the third step of the inventive method according to the present invention.

In contrast thereto, in the exemplary embodiment represented in <FIG>, in a seventh processing step <NUM> (subsequent to the fourth processing step <NUM>), it is the mobile communication network <NUM> that evaluates the conditions (regarding dual/multiple steering) in accordance to both the capability indication information and the multiple registration information (network-based conditional update of dual/multiple registration information), and, subsequently and in an eighth processing step <NUM>, transmits - if applicable and necessary due to a change, e.g. of the location of the user equipment <NUM> - a configuration update information or configuration update message to the user equipment <NUM>, the configuration update information or configuration update message comprising the multiple registration information; thereafter, in a ninth processing step <NUM>, the user equipment <NUM> again applies the dual or multiple steering functionality, i.e. it is simultaneously connected to the first and second mobile communication networks <NUM>, <NUM>, according to the conditions or the configuration update information or message received, and thereby realizes, or executes, the third step of the inventive method according to the present invention.

According to the present invention, the embodiments or variants referred to in <FIG> are also able to be mixed or realized in parallel (or combined), i.e. the evaluation of the conditions to be observed regarding dual/multiple steering might also be conducted by both the user equipment <NUM> (e.g. regarding a part of such conditions) and the mobile communication network <NUM> (e.g. regarding another part of such conditions).

Furthermore according to the present invention, alternative ways to send the dual/multiple registration information are possible and preferred; hence, especially the following forms in which the dual/multiple registration information is conveyed to the user equipment <NUM> - either as part of a registration procedure or because of a network-triggered update of said information - are proposed:.

Regarding the realization or deployment of dual/multiple steering functionality, there might be constraints for supporting dual/multiple connectivity by the network/network components:
In order to produce the dual/multiple registration information, the mobile communication network <NUM> should consider not only the (capability indication) information provided by the user equipment <NUM>, but also its own capabilities. While a user equipment <NUM> may be capable of supporting simultaneous registration in multiple networks, from the network side, the following limitations may exist:.

As such, in order for the mobile communication network <NUM> (e.g. the AMF) to evaluate whether all necessary NFs are capable, considers that network functions include, in their NF profile (the network repository function, NRF, supports the functionality to support service discovery of NRF services and their endpoint addresses by the NRF bootstrapping service; the network function profile of a NF instance maintained in an NRF includes the information related to the network function that registered this profile), a dual/multiple registration capability indication, equivalent to the dual/multiple registration capability indication (information) of the user equipment <NUM>.

According to the present invention, it is preferred that at least the UDM, AUSF in the (H-)PLMN (in general terms, the "home network"; for standalone non-public networks, the term "credential holder (CH)" is used) would need to support dual/multiple registration capability, whereas functionality fulfilling the CH functionality (e.g., UDM or Authentication, Authorization and Accounting, AAA, system), PCF would also need it for most cases.

Hence, in this manner, the mobile communication network <NUM> is able to evaluate whether the capability (of deploying the dual/multiple steering functionality) can be offered to the (requesting) user equipment <NUM>, and - if support is heterogeneous (e.g. several CHF instances are present, and some of them are supporting the feature, and some others not) - only instances supporting the feature are selected to serve the given (or requesting) user equipment <NUM>.

Similarly, this information can be included in the subscriber data, such given network support, dual/multiple registration information can be steered with a per-subscriber granularity.

Hence preferably according to the present invention, within (or as part of) a mobile communication network, especially a core network thereof comprising network functions or services, a network function capability indication information is.

Additionally, it is preferred to take other conditions into consideration, such as:.

The case of a roaming scenario is schematically shown in <FIG>, which schematically illustrates a communication diagram of the user equipment <NUM> transmitting the capability indication information, and the user equipment <NUM> receiving the multiple registration information relating to a roaming situation of the user equipment <NUM>, involving a visited network <NUM> the user equipment <NUM> is connected to, and the home network <NUM> of the user equipment <NUM>: In such a roaming case, i.e. generally when a subscriber of a mobile communication network (i.e. the home network), e.g. the first mobile communication network <NUM>, is being served by a visited mobile communication network, e.g. mobile communication network <NUM>, the home network <NUM> is still responsible regarding authentication and authorization (the visited network <NUM> does not have the subscriber information or the cryptographic keys linked to this subscriber). Additionally, it might be the case, that such two networks are not directly connected but are connected via one or more intermediaries (e.g. IPX and/or roaming hub), hereinafter called intermediary network <NUM>.

To support roaming, the present invention and especially the inventive method proposes that the dual/multiple registration capability (information) - transmitted by the user equipment <NUM> - is propagated such that it is known to the visited mobile communication network <NUM>, the home mobile communication network <NUM> and/or the intermediary network <NUM>, such that the following cases are avoided:.

<FIG> shows all of the information flow directions:.

Claim 1:
Method for operating a user equipment (<NUM>) with a radio access network of a mobile communication network, wherein the user equipment (<NUM>) is enabled to be simultaneously connected to different mobile communication networks that have, or use, different pieces of network identifier information,
wherein such different mobile communication networks comprise a first mobile communication network (<NUM>) and, at least, a second mobile communication network (<NUM>), wherein the user equipment (<NUM>) is enabled to be registered, using a first connection, to the first mobile communication network (<NUM>), and wherein the user equipment (<NUM>) is furthermore enabled to be also registered, using a second connection, to at least the second mobile communication network (<NUM>), wherein, in order to use the user equipment (<NUM>) with either one, or both, of the first and/or second mobile communication networks (<NUM>, <NUM>), the method comprises the following steps:
-- in a first step, the user equipment (<NUM>) transmits a capability indication information, the capability indication information comprising at least a piece of information of whether the user equipment (<NUM>) supports, or is enabled, to establish both the first connection and the second connection, wherein the capability indication information comprises information regarding the first mobile communication network when connecting to the second network,
-- in a second step, the user equipment (<NUM>) receives a multiple registration information, the multiple registration information comprising at least a piece of information of whether the user equipment (<NUM>) is allowed to establish both the first connection and the second connection.