Method for assisting user equipment in roaming from a first network to a second network - Patents.com

Abstract

A method is proposed for supporting roaming of a user equipment from a first network to a second network. The first network and the second network are located in respective regions separated by a boundary. The method includes processing, by the second network, an application layer of the roaming of the user equipment from the first network to the second network using the application layer information when detecting a boundary crossing by the user equipment. More specifically, the user equipment transmits a signal to at least one of the first network and the second network indicating that the user equipment belongs to a particular user equipment class supported by a consortium of networks including at least the first network and the second network, thereby updating a routing policy of the user equipment defined as belonging to the particular class. The updated routing policy is then used by the second network to process the application layer for the roaming of the user equipment, whereby the roaming is seamless for the user equipment.

Description

[Technical field]

[0001] The present disclosure relates to service continuity for telecommunication applications in border scenarios (ie, when a terminal crosses a border). [Background technology]

[0002] For example, when terminal chips are embedded in vehicles for so-called V2X applications (where "V2X" stands for "Vehicle to Everything" and aims to make various telecommunication services: data, voice, video, etc. available to the user of the vehicle), service continuity is a key requirement for the design of edge network architectures.

[0003] Service continuity from the point of view of such applications can be seen as a "handover" in GSM communications when a vehicle crosses, for example, a border between two different countries.

[0004] A communicating user equipment (hereinafter "UE"), for example in the form of a telecommunication chip, can be installed in the vehicle to implement V2X applications. The communication context of the current application involving the V2X UE is transferred from a source edge application server to a target application server located within the new country as the V2X UE moves.

[0005] The general problem of service continuity for applications is represented in Figure 1, which shows two Edge Application Servers (EAS) serving two locations (e.g., two different countries). The Source EAS (S-EAS) serves V2X UEs located at location #1, whereas the Target EAS (T-EAS) serves V2X UEs located at location #2.

[0006] When the V2X UE is moving from location #1 to location #2, the latency requirement of the S-EAS is no longer maintained and the V2X application needs to reconfigure to a closer EAS to maintain application latency. Summary of the Invention

[0007] The present disclosure improves this situation.

[0008] The present disclosure provides a method for assisting roaming of a user equipment from a first network to a second network, the first network and the second network being located within respective regions separated by a boundary; The method includes, when detecting that the user equipment crosses a boundary, the second network uses the application layer information to process an application layer of roaming of the user equipment from the first network to the second network; the user equipment transmitting a signal to at least one of the first network and the second network indicating that the user equipment belongs to a particular user equipment class supported by a consortium of networks including at least the first network and the second network, thereby updating a routing policy for the user equipment defined as belonging to the particular class; A method is proposed in which the updated routing policy is used by the second network to process the application layer for roaming of the user equipment, thereby making the roaming seamless for the user equipment.

[0009] In one embodiment, before crossing the boundary, the unified data repositories of the first and second networks are updated to register identifiers of user equipment belonging to a particular class, such that when crossing the boundary, the user equipment belonging to a particular class is detected and identified based on at least one of the unified data repositories.

[0010] In one embodiment, prior to crossing the boundary, at least one node of one of the first network and the second network is pre-defined and registered as a federation node, and the first network sends application layer information to the federation node to update the user equipment's routing policy with the federation-related information.

[0011] The federation node can then use at least one of the integrated data repositories to detect the user equipment as belonging to a particular class.

[0012] The federation node may be a multi-access edge computing node (MEC node) deployed between the first network and the second network.

[0013] Additionally, or alternatively, the federation node intervening in the roaming may be a PCF node of the second network. "PCF" stands for "Policy Control Function".

[0014] Additionally, complementarily or alternatively, the federated node intervening in the roaming may be an SMF node of the second network. "SMF" generally refers to "Session Management Function" for seamless application session roaming.

[0015] In one embodiment, Prior to roaming, when the user equipment is connected to the first network, when the first network receives a signal from the user equipment belonging to a particular class, the first network updates a routing policy of the user equipment to define the user equipment as belonging to the particular class; During roaming, the first network triggers the establishment of a federation policy control function node and triggers the establishment of a federation data repository with the second network by sending application layer information to the federation policy control function node (S2), and the federation policy control function node is delegated to update a route selection policy of the user equipment in the second network and to update the federation data repository of the second network; When the user equipment connects to the second network, the second network detects the user equipment as belonging to a particular class using the second network's updated unified data repository and handles roaming of the user equipment using the user equipment's application layer information in the second network and updated routing policies.

[0016] In this embodiment, the federation policy control function layer is implemented by delegating federation policy control function nodes.

[0017] The federation policy control function node may typically be a multi-access edge computing node belonging to the second network and may be located near the border.

[0018] The method according to the present disclosure is particularly advantageous when the first network and the second network are located in separate respective countries, in which case roaming is seamless even when crossing borders between these countries, e.g., an application session conducted by the user equipment can continue without interruption when crossing the border.

[0019] In an example embodiment, the user equipment may be mounted on a vehicle to perform V2X applications. "V2X" refers to "vehicle-to-everything" applications. Typically, several user equipment may be mounted on the same vehicle, or on several vehicles following each other, where these user equipment are then considered as a platoon of user equipment members of a federation, e.g. all treated together.

[0020] The present disclosure is also directed to a computer program comprising instructions that, when executed by a processing circuit, cause the computer program to perform the methods presented above. The present disclosure is also directed to a non-transitory computer storage medium storing such instructions.

[0021] The present disclosure is also directed to a system for assisting roaming of a user equipment from a first network to a second network, the first network and the second network being located in respective regions separated by a boundary, the system comprising a user equipment and the first network and the second network, the user equipment and the first network and the second network being configured to perform the method presented above.

[0022] In one embodiment, such a system may further comprise a federation manager computer entity that stores the integrated data repository of the first network and the second network together with identifiers of user equipment belonging to a particular class, and implements the particular methods involving the integrated data repository presented above.

[0023] In this embodiment, the federation manager computer entity may store data of at least one node of one of the first network and the second network that is considered a federation node, as presented above.

[0024] The present disclosure is also directed to user equipment for such a system.

[0025] Other features, details and advantages are set forth in the following detailed description and in the figures. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 illustrates normal management of service continuity attempts for V2X edge applications. [Diagram 2] FIG. 13 is a diagram illustrating a schematic of context allocation in a boundary scenario. [Diagram 3] FIG. 2 illustrates an example embodiment of a method for handling roaming according to the present disclosure. [Figure 4] FIG. 1 illustrates the current URSP update in a normal boundary scenario. [Diagram 5] FIG. 1 illustrates a URSP update proposed by the present disclosure using federation management. [Figure 6] A diagram showing normal communication over the same interface N24. [Figure 7] 7 shows new signaling messages exchanged over interface N24 between PCF nodes in the context of the present disclosure, for comparison with normal communication over the same interface N24 shown in FIG. 6. [Figure 8] FIG. 13 shows normal communication over the same interface N16. [Figure 9] This figure shows new signaling messages exchanged over interface N16 between SMF nodes in the context of the present disclosure, in particular for comparison with normal communication over the same interface N16 shown in FIG. [Figure 10] FIG. 1 is a diagram depicting various intervening entities in a 5G network architecture (from 3GPP™ TS 23.501). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The present disclosure proposes to establish a roaming framework that enables updating of routing policies for a user equipment (hereinafter referred to as "UE") roaming from a home public land mobile network (hereinafter referred to as "H-PLMN") to a visited public land mobile network (V-PLMN).

[0028] Updates to the UE Routing Policy (URSP) are performed in the UE's Visited Policy Control Function (PCF), thereby improving application layer reconfiguration latency and integrating application layer roaming into standard roaming procedures.

[0029] The proactive URSP update for a given UE (prior to the UE's valid border location) is based on the principle of building a federation of public land mobile networks (PLMNs) at the border between at least two countries, such that application layer processing is harmonized between the home PLMN and the visited PLMN.

[0030] Referring to FIG. 3, the following steps may then be performed. Prior to S1-roaming, the home PLMN updates the UE's URSP to define the UE as a "association member." When the S2-UE is roaming, the home PLMN triggers the establishment of a federated PCF and UDR (Unified Data Repository, as described in more detail below) with the visited PLMN by sending application layer information to the visited PCF. a) The federation PCF is established through delegation of updates to the URSP to the visited PCF and updates the UDR accordingly. b) The federation PCF layer can be implemented by delegating to a certain MEC node at the boundary which is used to update the URSP with specific federation related information. "MEC" stands for "Multi-access Edge Computing" (or previously "Mobile Edge Computing"), and MEC nodes, in turn, designate network nodes located near the border. When an S3-UE attaches to a V-PLMN, the visited UDR is used to detect the UE as a federation member, and the V-PLMN uses the application layer information and V-PLMN policies to handle the application layer of the roaming UE. The UE experiences service continuity without interruption due to boundary scenarios.

[0031] In one embodiment, it is proposed to build a federation policy layer to facilitate the update of URSPs when a UE roams from a home PLMN to a visited PLMN. This URSP update is considered as a trigger for improving application layer roaming during boundary crossing scenarios. The URSP is first executed in the home PCF (before the roaming itself) since the subscription information of the involved UE is stored in the Unified Data Management Node (UDM) and Unified Data Repository Node (UDR).

[0032] Before describing this embodiment in detail, we will first refer to FIG. 1 and explain how application layer forwarding is performed in a 5G system according to the prior art.

[0033] The following general procedure is used for application reconfiguration according to the prior art (the terminology is presented above): Arrow (1): A V2X UE moves from location #1 to location #2. Arrow (2): This event (1) is notified to the source EAS (edge ​​application server). Arrow (3): The source EAS or the application orchestrator decides to reconfigure the V2X application to the target EAS. The source EAS sends the application context to the target EAS. Arrow (4): The target EAS notifies the network and the source EAS of the completion of the application context reconfiguration (arrows (3) and (4) in FIG. 1).

[0034] In the border scenario, it is assumed that the networks connecting the source EAS and the target EAS are networks of two different Mobile Network Operators (MNOs). Each MNO's network: an access layer; a multi-access edge computing layer (MEC) formed by a core network, an edge platform and an edge orchestration and management layer; It is formed from.

[0035] As shown in event (1) of FIG. 2, which illustrates the same prior art situation, when the vehicle UE is moving from the source MNO network to the target MNO network, different information is reconfigured from the source MNO network to the target MNO network.

[0036] Now referring to Figure 2 (where CN and RAN designate the core network and radio access network), in steps (2) and (3), information regarding vehicle subscription information, vehicle session status context information, and vehicle access network context information is transmitted. After roaming, i.e., steps (2) and (3), the V2X application context is transferred between two multi-access edge servers (source MEC and target MEC).

[0037] The UE Routing Policy (URSP) is an important policy function used by the UE to determine how to route ongoing traffic. It can route established PDU sessions (Protocol Data Units), or it can be offloaded to a non-3GPP access outside the PDU session, Or it may trigger the establishment of a new PDU session.

[0038] Some key URSP rules and Application Function (AF) guidance for updating URSPs are presented below.

[0039] Each URSP rule contains a list of routing descriptors that includes one or more routing descriptors, each with a different routing descriptor priority value.

[0040] The structure of the URSP does not define how the PCF splits the URSP when it cannot be delivered to the UE in a simple message, such as a single NAS message (non-access stratum). It is expected that the UE application cannot change or override the PDU session parameters in the URSP rule. The UE application can express preferences when requesting a network connection (e.g., a certain connection capability), which can be mapped to specific PDU session parameters by the URSP rule.

[0041] If the PDU session establishment request is rejected by the network, the UE may trigger a new PDU session establishment based on the reason for the rejection and the URSP policy. When the PCF provisions the URSP rules to the UE, it may include one URSP rule with a "match all" traffic descriptor.

[0042] A URSP rule with a "match all" traffic descriptor is used to route traffic for applications that do not match any other URSP rule and is therefore evaluated as the last URSP rule, i.e., with the lowest priority. There must be only one routing descriptor in this URSP rule. A routing descriptor in this URSP rule contains at most one value for each routing component.

[0043] The Application Facility (AF) can provide guidance for determining the URSP, and in typical standard specifications the following mechanisms are used, as presented below:

[0044] The AF can provide guidance for URSP determination to the 5G system via the Network Exposure Function (NEF). The AF can belong to the operator or an external party. Since it is the PCF that determines the URSP of the UE, the PCF is in the home PLMN.

[0045] Since the UE is uniquely identified in the home PLMN by an internal identifier provided by the Unified Data Management (UDM) node, the home PCF first updates the URSP. The combined Network Exposure Function (NEF) and Unified Data Repository (UDR) are used to secure and route AF requests to the relevant UEs in the system as shown in Figure 4. Here, the reference symbol N24 designates the reference point (in other words, the interface) between the PCF node in the visited network and the PCF node in the home network, as shown, for example, on page 28 of the standard ETSI TS 123 501 V15.3.0 (2018-09) (3GPP TS 23.501 version 15.3.0 release 15). In this respect, the present disclosure can implement new signaling over the current roaming interface N24 between the home PCF node and the visited PCF node.

[0046] In boundary scenarios, i.e., when a UE roams from a home PLMN to a visited PLMN, the URSP update is usually performed in the home PCF. This may increase the reconfiguration latency at the application layer, which may complicate seamless roaming, for example in platooning scenarios involving several interconnected user equipments crossing a boundary together. Indeed, the prior art URSP update procedure is relatively slow and may cause problems in the case of SSC mode parameters of session and service continuity, or when changing the DNN of application capabilities.

[0047] We propose a solution to this problem by enabling the updating of URSPs in the visited PLMN, and in particular in the visited PCF, and developing an overall architecture related to this updating.

[0048] Here, we propose to build a federation framework at the boundary to provide reconfiguration of the URSP for a specific UE. The overall description of the federation framework is shown in Figure 5.

[0049] Before crossing the actual boundary, the core network registers with a supervisory entity, labeled "federation manager" in Figure 5. Specifically, the UDRs of the home and visited coordinated internal identification rules are stored in the federation manager for the particular UE present in the federation. The participating PCF nodes then register with the federation manager to harmonize policies for the federation members. This policy and traffic steering alignment is performed before roaming. The alignment can be defined, for example, according to a specific agreement between the respective network managers.

[0050] Then, when one of these specific UEs roams into the visited network, the UE is identified by the visited UDR as a UE roaming from the association network, and the visited PCF can update its URSP if the UE is detected as an association UE (one of the "specific" UEs mentioned above). Typically, in the example of Figure 5, detection of UE roaming (arrow (3)) is initiated. -Identification of the UE as an association UE by the UDR of the visited network, and As a result, the URSP is seamlessly updated for the UE at the UE through the visited PCF.

[0051] This UE identification can be done by transmitting application layer parameters used in the home PLMN, which are used by the visited PLMN to identify the home PLMN as a member of the federation, allowing joint application reconfiguration and UE roaming. This implementation allows for accelerated and integrated application layer roaming with core network signaling, as opposed to prior art implementations where updates in the visited network are controlled by home network policies and involve delays, with a federation architecture at the border as presented in FIG. 5.

[0052] The following concerns the new signaling introduced by the method presented above.

[0053] The N24 interface is an interface between a Visited Policy Control Function (V-PCF) and a Home Policy Control Function (H-PCF). The interface is standardized in the TS29.513 specification and is responsible for transferring the following information between PCF entities: - Policy association, updating and arbitration between a roaming UE and an Access and Mobility Function (AMF) in a visited network. This association is forwarded by the Home PCF from the Visited PCF and decisions regarding policy association are made in the H-PCF. - Authorization and provisioning of the UE with a specific QoS profile, forwarded from the visited PCF to the home PCF. The authorization decision is made by the home PCF.

[0054] A typical simplified communication over interface N24 is shown in FIG.

[0055] The method according to the present specification proposes the following changes to the signaling when a federation of networks is considered: in this case, all previous policy control decisions are made in the visited PCF and a new message is sent over interface N24 to delegate the policy control rules from the home PCF to the visited PCF. This new message may contain information about the UE to which this particular PCF processing pertains or is derived by a new identity of the roaming UE in the visited PCF, defining which UE has its home network in the federation.

[0056] The overall new timing diagram is shown in figure 7. The new signalling via interface N24 and the new processing in the different nodes shown in boxes (3) and (4) are of course comparable to the process in figure 6.

[0057] In the following, we also propose an adjustment of the Session Management Functions (SMFs) when a UE roams from a home PLMN to a visited PLMN. This adjustment is based on adding new messages over the N16 interface between the home SMF and the visited SMF. The N16 interface is standardized in the 3GPP standard TS 29.502. The information transmitted over the interface N16 is essentially related to the traffic handling of the roaming UE. Examples of this information include: -Routing information of the user plane function (UPF) of the communication network towards the edge application server; - binding rules between QoS flows associated with a particular session of a roaming UE in a visited core network; - Transfer of session management context during roaming between home and visited SMF.

[0058] A typical call flow for the prior art interface N16 is shown in FIG.

[0059] In a similar manner to the PCF coordination described above, it is also proposed that the session update decision be performed in the visited SMF and that the handling of the session context be standardized among UEs that are members of a federation network. This standardized handling of the session context may, for example, be as follows: -Use the same edge application server for all UEs that are members of a federation and pre-configure routing in the user plane function (UPF) for all UEs; - the same QoS treatment of packets belonging to UEs that are members of a federation; Typically, such QoS treatments are, for example, the priority level of a packet and / or the maximum data burst size.

[0060] The modifications to the signalling flow over interface N16 are shown in FIG. 9, where new messages and information are added in boxes (3) and (4).

[0061] For completeness, Figure 10 looks back at the 5G network architecture (from 3GPP TS 23.501) and shows the various entities involved in the description given above.

[0062] Further details regarding messages sent over interfaces N24 and N16 are provided below.

[0063] These messages of delegation between the two networks allow for the updating of the URSP and also serve to identify the UE members of the federation.

[0064] Concerning the usual operator federations in the GSMA (Open Platform Group), we propose here a lower level federation with stronger coordination of sessions and quality of service (QOS) between networks. The GSMA OPG is usually a platform that coordinates applications and does not take into account the QoS conditions of each network. The networks manage to provide the best possible service without guaranteeing QoS.

[0065] A new message over the N24 interface between the home PCF and the visited PCF delegates the policy control functions of the home PCF to the visited PCF for UEs identified as members of the federation. This policy control can be, for example: - Identification of the UEs that are members of the association, - updating the UE routing policy URSP for UEs that are members of a federation; -Allowing registration and / or access of a UE that is a member of a federation to a mobility node (AMF) in a visited PLMN; -Indication of MEC node identifiers (data network identifiers) to be considered for updating the UE routing policy; - An indication of the session QoS parameters recently set by the home PCF.

[0066] After receiving a new message over the N24 interface, the visited PCF can: -Identifying UEs that are members of a federation through: o An indication of UE association membership based on new messages received by the Home PCF, o An indication of UE association membership received from the UE's URSP when attaching to a visited PLMN; Apply policy control for the identified UE as follows: Providing authorization for the identified UE to access the visited core network node; o updating UE routing policies for UEs identified as members of the association; updating the QoS parameters of the communications of UEs identified as members of the association; o Updating the MEC node identity for UEs identified as members of the association.

[0067] Another new message sent over the N16 interface connects both the Session Management Functions (SMFs) in the Home PLMN and the Visited PLMN, and a new message is proposed that can be used to identify the association membership of a UE between the User Plane Function and the Visited Session Management Function (V-SMF).

[0068] Currently, over the N16 interface, the normal messages concern the control of sessions during roaming across boundaries. Session control messages do the following: - configuring the visited SMG as an intermediate SMF (I-SMF) for ongoing sessions while roaming; - Sending relevant session information such as session type (IP, Ethernet, etc.), as well as quality of service routing information and session continuity mode (one or multiple sessions per roaming UE); -Provides information to trigger the configuration / reconfiguration of a session in a visited PLMN network.

[0069] For example, Figure 8 shows an example where a roaming UE's session is updated in a visited network. In this case, the Visited SMF (V-SMF) sends information to the Home SMF (H-SMF) and the session update decision is made in the H-SMF. Here, it is proposed to add a new delegation message for session management over N16, where session management for ongoing sessions of UEs identified as members of a federation is delegated from the H-SMF to the V-SMF through a new message including: - Session context, e.g., session type, session 5G quality of service identifier (5QI) for the flow of the session, - an identity of the roaming UE and a mapping of the roaming UE to a corresponding session context; - Additional information such as Forwarding Action Rules (FARs) used to forward packets in the user plane function of the home PLMN. These rules can help maintain session-level continuity for sessions of UEs identified as association members.

[0070] Similar to the description of signaling over N24, session update and modification actions are delegated from the H-SMF to the V-SMF.

[0071] Here, a key difference in the level of coordination is noteworthy compared to typical current art application platforms as described in the GSMA Open Platform Group, which is currently developing requirements for coordinated deployment of applications across a consortium of operators. In the current art, the operator platform is considered an over-the-top (OTT) application layer that does not manage the actual policies and QoS of the network. In other words, the network performs best-effort coordination for roaming UEs. This disclosure instead proposes a low level of coordination where actual QoS is maintained between the H-PLMN and the V-PLMN.

[0072] Furthermore, current state of the art GSMA application platforms do not consider UE routing policy updates for application level adjustments which may cause service interruptions at the borders and frequent service reconfigurations.

Claims

1. 1. A method for assisting roaming of a user equipment from a first network to a second network, the first network and the second network being located within respective regions separated by a boundary, the method comprising: The method includes, upon detecting crossing of the boundary by the user equipment, the second network using application layer information to process an application layer of roaming of the user equipment from the first network to the second network; the user equipment transmitting a signal to at least one of the first network and the second network indicating that the user equipment belongs to a particular user equipment class supported by a consortium of networks including at least the first network and the second network, thereby updating a routing policy of the user equipment defined as belonging to the particular class; The updated routing policy is used by the second network to process the application layer for roaming of the user equipment, thereby making the roaming seamless for the user equipment.

2. 2. The method of claim 1, wherein before the boundary is crossed, integrated data repositories of the first network and the second network are updated and identifiers of the user equipment belonging to the particular class are registered, and when the boundary is crossed, the user equipment belonging to the particular class is detected and identified based on at least one of the integrated data repositories.

3. 3. The method of claim 1, wherein prior to crossing the boundary, at least one node of one of the first network and the second network is predefined and registered as a federation node, and the first network transmits the application layer information to the federation node to update a routing policy of the user equipment with federation related information.

4. The method of claim 3 when combined with claim 2, wherein the federation node detects the user equipment as belonging to the particular class using at least one of the integrated data repositories.

5. The method of claim 3 or 4, wherein the federation node is a multi-access edge computing node deployed between the first network and the second network.

6. The method of any one of claims 3 to 5, wherein the federation node is a PCF node of the second network, "PCF" referring to "Policy Control Function".

7. The method according to any one of claims 3 to 6, wherein the federated node is an SMF node of the second network, where "SMF" refers to "Session Management Function" for seamless application session roaming.

8. prior to the roaming, when the user equipment is connected to the first network, when the first network receives the signal of the user equipment belonging to the particular class, the first network updates a routing policy of the user equipment to define the user equipment as belonging to the particular class; During the roaming, the first network triggers the establishment of a federation policy control function node and triggers the establishment of a federation data repository with the second network by sending the application layer information to the federation policy control function node, the federation policy control function node being delegated to update a routing policy of the user equipment in the second network and to update a federation data repository of the second network; 8. The method according to claim 1, wherein when the user equipment connects to the second network, the second network detects the user equipment as belonging to the particular class using an updated unified data repository of the second network, and processes the roaming of the user equipment using the application layer information of the user equipment in the second network and the updated routing selection policy.

9. The method of claim 8 , wherein a federation policy control function layer is implemented by delegating the federation policy control function node.

10. The method of claim 8 or 9, wherein the federation policy control function node is a multi-access edge computing node belonging to the second network and located near the border.

11. The method of any one of claims 1 to 10, wherein the first network and the second network are located in separate respective countries.

12. The method according to any one of claims 1 to 11, wherein the user equipment is embedded in a vehicle for performing V2X applications, "V2X" referring to "Vehicle to Everything" applications.

13. A computer program comprising instructions which, when executed by a processing circuit, cause the computer program to perform the method of any one of claims 1 to 12.

14. A system for assisting roaming of a user equipment from a first network to a second network, the first network and the second network being located in respective areas separated by a boundary, the system comprising the user equipment and the first network and the second network, the user equipment and the first network and the second network being configured to perform a method according to any one of claims 1 to 12.

15. 15. The system of claim 14, further comprising a federation manager computer entity configured to store a unified data repository of the first network and the second network together with identifiers of user equipment belonging to the particular class, to implement the method of claim 2.

16. 16. The system of claim 15, wherein the federation manager computer entity stores data of at least one node of one of the first network and the second network as a federation node to implement the method of claim 3.

17. User equipment of the system according to any one of claims 14 to 16.

Images