WO2018006985A1

WO2018006985A1 - System, devices, and methods for interworking between a legacy 3gpp mobile telecommunications network (4g) and a next generation network (5g)

Info

Publication number: WO2018006985A1
Application number: PCT/EP2016/066372
Authority: WO
Inventors: Filipe LEITAO; Andreas Kunz; Genadi Velev; Toshiyuki Tamura
Original assignee: Nec Corporation
Priority date: 2016-07-08
Filing date: 2016-07-08
Publication date: 2018-01-11

Abstract

A system is disclosed comprising: a first type of communication network that comprises a radio access network and a first core network; and second type of communication network comprising second core network. The first type of communication network and the second type of communication network each operate in accordance with a different respective set of communication standards. An MME of the first core network is configured to determine whether a communication device that is located in a cell of the radio access network is capable of using (or entitled to use) a service that is provided via the second type of communication network. The MME is configured to transmit a message, towards the second core network, to initiate interworking between the first core network and the second core network for the provision of the service.

Description

SYSTEM, DEVICES, AND METHODS FOR INTERWORKING BETWEEN A

LEGACY 3GPP MOBILE TELECOMMUNICATIONS NETWORK (4G) AND A

NEXT GENERATION NETWORK (5G)

The present invention relates to a communication system. The invention has particular but not exclusive relevance to wireless communication systems and devices thereof operating according to the 3rd Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof. The invention has particular although not exclusive relevance to relaying mobility management signalling for interworking between current 3GPP core networks and so-called 'Next Generation' core networks.

The latest developments of the 3GPP standards are referred to as the Long Term Evolution (LTE) of Evolved Packet Core (EPC) network and Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), also commonly referred as '4G'. Under the 3GPP standards, a NodeB (or an eNB in LTE) is the base station via which communication devices connect to a core network and communicate to other communication devices or remote servers. For simplicity, the present application will use the term base station to refer to any such base stations. The core network (i.e. the EPC in case of LTE) hosts functionality for subscriber management, mobility management, charging, security, and call/session management (amongst others), and provides connection for communication devices to external networks, such as the Internet.

Communication devices might be, for example, mobile communication devices such as mobile telephones, smartphones, user equipment, personal digital assistants, laptop/tablet computers, web browsers, e-book readers and/or the like. Such mobile (or even generally stationary) devices are typically operated by a user (although it is also possible to connect so-called 'Internet of Things' devices and similar machine- type communication devices to the network). For simplicity, the present application refers to mobile devices in the description but it will be appreciated that the technology described can be implemented on any communication devices (mobile and/or generally stationary) that can connect to a communications network for sending/receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

The term '5G' refers to an evolving communication technology that is expected to support a variety of applications and services. Various details of 5G networks are described in, for example, the 'NGMN 5G White Paper' V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which document is available from https://www.ngmn.org/5g-white-paper.html. 3GPP intends to support 5G by way of the so-called '3GPP NextGen' radio access network (RAN) and the 3GPP NextGen core network (described in 3GPP technical report (TR) 23.799 VO.5.0).

Typically, after deployment of a new network, there is an interworking and migration period during which subscribers are gradually switching over to the new network. Therefore, it will be appreciated that following the deployment of a 5G / NextGen network by a network operator (LTE operator), there may be an interworking and migration period during which both a 5G access network (supported by a 3GPP NextGen core network) and an LTE radio access network (i.e. E-UTRAN, supported by an associated EPC network) are simultaneously deployed and maintained by the network operator. This aspect is also noted in 3GPP TR 23.799 VO.5.0 as "Key Issue 18: Interworking and Migration", in the context of Study on Architecture for Next Generation System (5G core).

During such an interworking/migration period the operator needs to maintain service delivery and management for all the deployed networks (i.e. both old and new). However, at some point some services might be delivered exclusively on the new core network (in this case, a 5G core network), meaning that LTE devices (served by the EPC) would not have access to these services (or they would have access only to a limited number/functionality of services). It will also be appreciated that the NextGen core may use different authentication mechanisms to the ones used by EPC, in which case LTE-only UEs cannot be authenticated by the NextGen core network (although such LTE-only UEs may still be authenticated in the EPC before they are allowed to access NextGen based services).

It is assumed that typical/current LTE UEs have no access to new radio access technologies (RATs), such as 5G RATs, due to the different physical layers used in LTE and in 5G. Therefore, it is suggested that mobility interworking options could focus on: i) interworking between LTE RAT nodes (e.g. LTE eNBs), and the NextGen core network; and/or ii) interworking between LTE EPC core and NextGen core networks, leveraging on the mobility management solutions. Due to the impact of the first option on existing LTE RAT layer nodes (eNBs), the inventors propose interworking according to the second option (i.e. interworking between core networks).

Interworking between LTE and NextGen networks is also important in order to support service continuity between an LTE network and a new 5G/NextGen network (e.g. for those UEs that are both LTE and 5G RAT capable). In this situation, the new 5G/NextGen core network needs to be aware of subscriber information associated with the UE before mobility event (whilst the UE is attached to the LTE access network) for inter RAT handover from LTE to 5G RAT, in order to be prepared for handover procedures involving the NextGen network. Accordingly, preferred embodiments of the present invention aim to provide methods and apparatus which address or at least partially deal with the above issues.

Although for efficiency of understanding for those of skill in the art, the invention will be described in detail in the context of a 3GPP system (interworking between LTE and 5G portions of the network), the principles of the invention can be applied to other systems having different type of core networks.

In one aspect of the invention, there is provided a core network apparatus for a first type of communication network, the core network apparatus comprising: a controller configured to determine whether a communication device is capable of using a service that is configured for provision via a second type of communication network; and a transceiver configured to transmit a message, towards a second core network of the second type of communication network, to initiate interworking between a first core network in the first type of communication network and the second core network in the second type of communication network for the provision of the service.

In one aspect of the invention, there is provided a core network apparatus for communicating with a first type of communication network, the core network apparatus included in a second type of communication network, the core network apparatus comprising: a transceiver configured to receive a message, from a first core network in the first type of communication network, to initiate interworking between the first core network and a second core network in the second type of communication network for the provision, for a communication device, of a service that is configured for provision via the second type of communication network.

In one aspect of the invention, there is provided a method performed by a core network apparatus of a first type of communication network, the method comprising: determining whether a communication device is capable of using a service that is configured for provision via a second type of communication network; and transmitting a message, towards a second core network of the second type of communication network, to initiate interworking between a first core network in the first type of communication network and the second core network in the second type of communication network for the provision of the service.

In one aspect of the invention, there is provided a method performed by a core network apparatus communicating with a first type of communication network, the core network apparatus forming part of a second type of communication network, the method comprising: receiving a message, from a first core network, to initiate interworking between the first core network in the first type of communication network and the second core network in the second type of communication network for the provision, for a communication device, of a service that is configured for provision via the second type of communication network.

Aspects of the invention extend to corresponding systems, methods, and computer program products such as computer readable storage media having instructions stored thereon which are operable to program a programmable processor to carry out a method as described in the aspects and possibilities set out above or recited in the claims and/or to program a suitably adapted computer to provide the apparatus recited in any of the claims.

Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of (or in combination with) any other disclosed and/or illustrated features. In particular but without limitation the features of any of the claims dependent from a particular independent claim may be introduced into that independent claim in any combination or individually.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 illustrates schematically a cellular telecommunication system to which embodiments of the invention may be applied;

Figure 2 is a block diagram of a mobile device forming part of the system shown in Figure 1 ;

Figure 3 is a block diagram of a base station forming part of the system shown in Figure 1 ;

Figure 4 is a block diagram of a mobility management entity forming part of the system shown in Figure 1 ; Figure 5 is a block diagram of a generic NextGen management entity forming part of the system shown in Figure 1 ;

Figure 6 illustrates schematically a cellular telecommunication system to which an exemplary embodiment may be applied;

Figure 7 is a timing diagram illustrating an exemplary way in which an embodiment of the invention can be implemented in the system of Figure 6;

Figure 8 is a timing diagram illustrating another exemplary way in which an embodiment of the invention can be implemented in the system of Figure 6;

Figure 9 illustrates schematically a cellular telecommunication system to which another exemplary embodiment may be applied;

Figure 10 is a timing diagram illustrating an exemplary way in which an embodiment of the invention can be implemented in the system of Figure 9; and

Figure 1 1 illustrates schematically another cellular telecommunication system to which exemplary embodiments of the invention may be applied. Overview

Figure 1 schematically illustrates a telecommunications network 1 in which user equipment 3 (mobile telephones and/or other mobile devices) can communicate with each other via base stations 5 (e.g. an LTE base station or 'eNB') using an appropriate radio access technology (RAT). In this example, the mobile device 3 may be configured as an LTE UE 3A which supports at least an LTE radio access technology. However, the mobile device 3 may also be configured as a 5G/NextGen UE 3B (if it supports one or more 5G radio access technologies) and/or an eLTE UE 3C (if it supports one or more 'enhanced' LTE radio access technologies). In this case, the mobile device 3 may be configured to communicate via a 5G radio access network 6 (denoted '5G RAT' in Figure 1 ) using an appropriate 5G radio access technology.

As those skilled in the art will appreciate, whilst one mobile device 3 (with three possible UE configurations) and one base station 5 are shown in Figure 1 for illustration purposes, the system, when implemented, will typically include other base stations and mobile devices. Each base station 5 operates one or more associated cells. Mobile devices 3 connect to an appropriate cell (depending on their location and possibly on other factors, e.g. signal conditions, subscription data, capability, and/or the like) by establishing a radio resource control (RRC) connection with the base station 5 operating that cell. When the mobile device 3 is configured as an LTE UE, it communicates with the base station 5 over the so-called 'Uu' air interface (via an LTE cell).

The base station 5 is connected to an core (EPC) network 7 via an S1 interface and neighbouring base stations are connected to each other via an X2 interface (not shown in Figure 1 ). The telecommunications network 1 also includes a NextGen core network 8 and a NextGen RAN (not shown in Figure 1 ).

The EPC network 7 includes, amongst others, a mobility management entity (MME) 9 and a home subscriber server (HSS) 10. The HSS 10 is a database that contains user-related and subscriber-related information. It also provides support functions (e.g. to the MME 9) in mobility management, call and session setup, user authentication, and access authorisation. The MME 9 and the HSS 10 are connected via the so-called 'S6a' interface. Although omitted from Figure 1 for simplicity, the core network 7 typically also includes one or more serving gateways (SGWs) and packet data network gateways (PGWs) for providing a connection between the base station 5 and other networks (such as the Internet) and/or servers hosted outside the core network.

The NextGen core network 8 includes, amongst others, a control plane manager entity 15 (and may also include an appropriate user plane manager entity or a generic control/user plane manager). The MME 9 and the NextGen control plane manager entity 15 are connected via an appropriate interface, for example, an 'S10' interface (or '5G-S10' interface).

The MME 9 is the network node responsible for keeping track of the locations of mobile devices 3 within the communications network 1 , and for assisting the serving base station 5 in configuring the communication bearers used by mobile devices in the base station's cell. The mobile device 3 and the MME 9 communicate with each other using so-called non-access stratum (NAS) signalling, which is relayed between the mobile device 3 and the MME 9 by the base station 5 serving the mobile device 3.

In this system, the MME 9 is also responsible for interworking between the EPC 7 and the NextGen core network 8 (e.g. for LTE UEs) and for mobility involving the NextGen network (e.g. mobility between LTE and 5G RANs and/or mobility between LTE base stations for UEs accessing services provided by the NextGen core network 8). The NextGen control plane manager 15 is an entity responsible for managing general signalling within/involving the NextGen core network 8, including signalling related to mobility management.

In this system, advantageously, the network operator is able to offer NextGen specific services (which are delivered via the NextGen core network 8) to LTE-only subscribers (i.e. LTE UE 3A). This may be beneficial, for example, in scenarios in which the network operator wants/needs to offer some specific 5G services to LTE UEs. One such scenario is when the operator uses the (4G) LTE access (via base station 5) but offers specific network slicing capabilities via its NextGen core network 8 towards specific 3rd party service providers. In another scenario, for example during migration to 5G, the operator may be shutting down some of its EPC network functions (e.g. Packet Gateway; Policy Control, Charging function) and consequently LTE UEs 3A need to be (at least partly) supported by the NextGen core network 8.

The nodes of this system are therefore configured to realise interworking between LTE and 5G for the purposes of providing access to the NextGen core network 8 for LTE UEs (such as the mobile device 3A). Specifically, after the EPC domain 7 has authenticated the mobile device 3A (for example, when the mobile device 3A attaches itself to the EPC 7 via the base station 5), the MME 9 sets up the appropriate (LTE) data plane connection(s) for the mobile device 3A. Beneficially, the MME 9 also sets up appropriate (e.g. S10) signalling associations between the MME 9 (acting as pre- 5G mobility manager) and the NextGen control plane manager 15 (acting as a NextGen mobility manager). The MME 9 and the NextGen control plane manager 15 are therefore able to exchange signalling information with each other, including UE identification, context information, and control plane data support information.

In more detail, when the MME 9 proceeds to download, from the HSS 10, a user profile associated with the (LTE) mobile device 3A (which may be triggered by an attach request and/or similar NAS request), the MME 9 also obtains an indication whether or not that particular UE (or subscriber) is entitled to use 5G services and/or its associated user data is to be offloaded to the 5G core network 8. For example, the MME 9 may obtain an indication (from the user profile associated with the mobile device 3A) that this particular UE is entitled to use 5G services, but its authentication is still to be performed in the EPC domain 7 (e.g. because mobile device 3A supports LTE only). If the LTE/EPC attachment procedure is successful, the MME 9 sends a message to the NextGen control plane manager 15 indicating that the mobile device 3A has performed a successful attach to the EPC 7. Within this message, the MME 9 may also include: information identifying the mobile device 3A (e.g. an associated International Mobile Subscriber Identity (IMSI) and/or Mobile Station International Subscriber Directory Number (MSISDN)), and optionally information identifying the 5G services that the mobile device 3A is a subscriber to (in the case when the NextGen control plane manager 15 cannot resolve this information by itself, e.g. based on the mobile device identifier). Using the information provided by the MME 9 (and/or the HSS 10), the NextGen control plane manager 15 is able to initiate context awareness (by pre-loading mobility management information and/or the like) and resource reservation procedures in order to handle upcoming LTE UE traffic via the NextGen core network 8. Therefore, the MME 9 can start relaying signalling information associated with the (LTE) mobile device 3A to the NextGen control plane manager 15.

Beneficially, therefore, it is possible to implement / provide services via the NextGen / 5G core network for LTE compatible (or LTE-only) mobile devices that do not necessarily support any 5G radio interface and/or that can only be authenticated in the EPC domain. Mobile Device

Figure 2 is a block diagram illustrating the main components of the mobile device 3 shown in Figure 1 (e.g. a mobile telephone or other user equipment). As shown, the mobile device 3 has a transceiver circuit 31 that is operable to transmit signals to and to receive signals from a base station 5 via one or more antenna 33. The mobile device 3 has a controller 37 to control the operation of the mobile device 3. The controller 37 is associated with a memory 39 and is coupled to the transceiver circuit 31. Although not necessarily required for its operation, the mobile device 3 might of course have all the usual functionality of a conventional mobile telephone 3 (such as a user interface 35) and this may be provided by any one or any combination of hardware, software and firmware, as appropriate. Software may be pre-installed in the memory 39 and/or may be downloaded via the telecommunications network or from a removable data storage device (RMD), for example. The controller 37 is configured to control overall operation of the mobile device 3 by, in this example, program instructions or software instructions stored within memory 39. As shown, these software instructions include, among other things, an operating system 41 , a communications control module 43, and at least one radio access technology module (such as an LTE module 3A, a 5G module 3B, and/or an LTE module 3C) to access compatible radio access networks.

The communications control module 43 is operable to control the communication between the mobile device 3 and its serving base station 5 (and other communication devices connected to the serving base station 5, such as further mobile devices and/or network nodes).

If present, the LTE module 3A is responsible for communicating with base stations 5 operating in accordance with current LTE standards (e.g. 3G/4G base stations) and other nodes/devices connected to such base stations. If present, the 5G module 3B is responsible for communicating with base stations 5 operating in accordance with NextGen (5G) standards (e.g. base stations / access points of a NextGen RAN) and other nodes/devices connected to such NextGen base stations. If present, the eLTE module 3C is responsible for communicating with base stations 5 operating in accordance with eLTE standards and other nodes/devices connected to such eLTE base stations. Base Station

Figure 3 is a block diagram illustrating the main components of a base station 5 shown in Figure 1 (in this example, an LTE base station or 'eNB'). As shown, the base station 5 has a transceiver circuit 51 for transmitting signals to and for receiving signals from the communication devices (such as mobile devices 3 / user equipment) via one or more antenna 53, an MME interface 55 (e.g. an S1 interface) for transmitting signals to and for receiving signals from the MME 9 (in the EPC 7), and an SGW interface 56 (e.g. an S1 -U interface) for transmitting signals to and for receiving signals from a serving gateway 1 1.

The base station 5 has a controller 57 to control the operation of the base station 5. The controller 57 is associated with a memory 59. Although not necessarily shown in Figure 3, the base station 5 will of course have all the usual functionality of a cellular telephone network base station and this may be provided by any one or any combination of hardware, software and firmware, as appropriate. Software may be pre-installed in the memory 59 and/or may be downloaded via the communications network 1 or from a removable data storage device (RMD), for example. The controller 57 is configured to control the overall operation of the base station 5 by, in this example, program instructions or software instructions stored within memory 59. As shown, these software instructions include, among other things, an operating system 61 , a communications control module 63, and an LTE module 65.

In operation, the transceiver circuit 51 broadcasts information that indicates an ability to connect to the NextGen core network from the LTE access network. This broadcast information is used by mobile devices 3 to decide which core network, either EPC or NextGen Core, the mobile device 3 is going to attach to. Once the mobile devices 3 decides to attach to the NetGen Core, the mobile devices 3 sets the Decor ID, UE Usage type, Slice ID and other relevant information for both the RRC messages and NAS signalling messages in order for the base station 5 and the MME 9 to steer all signals, where appropriate, to a relevant NextGen Core. The communications control module 63 is operable to control the communication between the base station 5 and mobile devices 3 (user equipment) and other network entities that are connected to the base station 5. The communications control module 63 also controls the separate flows of downlink user traffic (via associated data radio bearers) and control data to be transmitted to communication devices associated with this base station 5 including, for example, control data for core network services and/or mobility of the mobile device 3.

The LTE module 65 is responsible for communicating with LTE compatible communication devices and network nodes (such as the nodes of the EPC 7) using one or more appropriate LTE protocols. Although not shown in Figure 3, the base station 5 may also comprise an appropriate eLTE module and/or 5G module (e.g. if the base station 5 also supports eLTE and/or 5G).

Mobility Management Entity

Figure 4 is a block diagram illustrating the main components of the mobility management entity 9 shown in Figure 1. As shown, the mobility management entity 9 has a transceiver circuit 71 for transmitting signals to and for receiving signals from the base station 5 (and/or communication devices connected to the base station 5) via a base station interface 75 (e.g. an S1 interface) and for transmitting signals to and for receiving signals from the NextGen core network 8 (and nodes thereof) via a NextGen interface 76 (e.g. an S10 interface and/or the like). The mobility management entity 9 has a controller 77 to control the operation of the mobility management entity 9. The controller 77 is associated with a memory 79. Although not necessarily shown in Figure 4, the mobility management entity 9 will of course have all the usual functionality of a cellular telephone network mobility management entity and this may be provided by any one or any combination of hardware, software and firmware, as appropriate. Software may be pre-installed in the memory 79 and/or may be downloaded via the communications network 1 or from a removable data storage device (RMD), for example. The controller 77 is configured to control the overall operation of the mobility management entity 9 by, in this example, program instructions or software instructions stored within memory 79. As shown, these software instructions include, among other things, an operating system 81 , a communications control module 83, a UE capability module 85, and an interworking module 89. The communications control module 83 is operable to control the communication between the mobility management entity 9 and the base station 5 (including mobile devices 3 connected to the base station 5) and other network entities that are connected to the mobility management entity 9 (in the EPC 7 and/or in the NextGen core network 8). The interworking module 89 is responsible for managing (generating, sending, receiving) signalling for the NextGen core network 8, including signalling related to interworking and/or mobility management.

The mobility management entity is accordingly extended to be able to process information elements (lEs) included in the Attach request message (e.g. network slice assistance information 5G capabilities), and also subscription information from the HSS related to the 5G capabilities/characteristics and network slicing information.

In addition, the MME may implement only a part of the full 4G MME functionality, for example the MME may implement the functionality needed for Authentication/Authorization, UP session setup/update with the SGW or SGW- CP/SGW-UP (in case of CUPS) and Interworking with NextGen control plane. As optimization implementation option, the MME and SGW-CP can be implemented together. NextGen management entity

Figure 5 is a block diagram illustrating the main components of a generic management entity of the NextGen core network 8 shown in Figure 1 (for example, a NextGen Control Plane Manager 15 and/or a NextGen User Plane Manager 16). As shown, the NextGen management entity 15/16 has a transceiver circuit 91 for transmitting and receiving control plane signals (e.g. to/from control-plane nodes such as the MME 9) via a control plane interface 92 and for transmitting and receiving user plane signals (e.g. to/from an SGW 1 1 ) via a user plane interface 93. The NextGen management entity 15/16 has a controller 94 to control the operation of the NextGen management entity 15/16. The controller 94 is associated with a memory 95. Functionality of the NextGen management entity 15/16 may be provided by any one or any combination of hardware, software and firmware, as appropriate. Software may be pre-installed in the memory 95 and/or may be downloaded via the communications network 1 or from a removable data storage device (RMD), for example. The controller 94 is configured to control the overall operation of the NextGen management entity 15/16 by, in this example, program instructions or software instructions stored within memory 95. As shown, these software instructions include, among other things, an operating system 96, a communications control module 97, a subscriber context module 98, and an interworking module 99. The communications control module 97 is operable to control the communication between the NextGen management entity 15/16 and other communication nodes (for example, the MME 9, the base station 5, mobile devices 3).

The interworking module 99 is responsible for managing (generating, sending, receiving) signalling between the EPC 7 and the NextGen core network 8, including signalling related to interworking and/or mobility management.

In the above description, the mobile device 3, the base station 5, the mobility management entity 9, and the NextGen management entity 15/16 are described for ease of understanding as having a number of discrete modules (such as the communications control modules and the interworking modules). Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the invention, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities. These modules may also be implemented in software, hardware, firmware or a mix of these.

A more detailed description will now be given (with reference to Figures 6 to 10) of the scenario discussed above where a mobile device is configured for 5G/NextGen services even when the mobile device supports only LTE and/or connects to the communication system via an LTE base station.

Operation - first example

Figure 6 illustrates signalling interworking for the provision of NextGen services for LTE mobile devices. The nodes shown in Figure 6 correspond to like-numbered nodes shown in Figure 1 , thus their description is omitted herein for simplicity. However, Figure 6 also shows an SGW 1 1 (in the EPC 7) and a NextGen user plane manager entity 16 (in the NextGen core network 8) for handling user plane data (drawn in dual lines and labelled 'Data'). Figure 6 also shows an external network 20 (e.g. the Internet) that the LTE UE 3A can access via the NextGen core network 8. Figure 7 is a timing diagram (message sequence chart) illustrating an example process performed by components of the system 1 when performing interworking in the system of Figure 6 (e.g. for LTE-only mobile devices).

The procedure begins in step S101 , in which the mobile device 3 (using its LTE module 3A) generates and sends, to the base station 5, an appropriate signalling message for initiating an attachment procedure with the EPC 7 (MME 9). For example, the mobile device 3 may be configured to generate (using its LTE module 3A) and send an 'Attach Request' signalling message as specified in 3GPP technical specification (TS) 23.401 V14.0.0. If the mobile device 3 is both LTE and 5G RAT capable, then the mobile device 3 indicates this capability in its signalling message to the MME 9, by appropriately setting a number of NextGen related parameters together with NAS parameters for the requested LTE access. The NextGen related parameters may include an appropriate NextGen specific temporary user identification, a NextGen service request flag, UE 5G radio capability, information identifying one or more (NextGen) core network slice instances (NSI), Multi Dimensional Descriptor (MDD), Tenant ID, Slice type, and/or the like. Such NextGen related parameters may be set either as individual NAS parameter(s) or set in an appropriately formatted NextGen NAS container parameter. The base station 5 is configured to forward the signalling message to the MME 9 (selected by the base station 5, if more than one MMEs are provided in the EPC 7) as described in 3GPP TS 23.401.

As generally shown in step S102, the EPC 7 authenticates the mobile device 3. This procedure is initiated by the MME 9 generating and sending an appropriately formatted Authentication-Information-Request (AIR) Command to the HSS 10. If the mobile device 3 is 5G capable (e.g. indicated by an appropriate NextGen Service request flag in the ATTACH message), then the MME 9 also includes the NextGen access request flag (and/or the like) in the AIR command in addition to any further parameter normally included in this command. If the HSS 10 finds the NextGen access request flag in the Authentication-Information-Request (AIR) Command from the MME 9, then the HSS 10 checks whether the mobile device 3 has a valid subscription to access to the NextGen service or not. If the HSS 10 determines that mobile device 3 has a valid subscription to access to the NextGen service, the HSS 10 generates and sends an appropriately formatted Authentication-lnformation- Answer (AIA) Command to the MME 9, including NextGen related authentication vectors, slice related authentication vectors (for all subscribed slides) in addition to the parameter normally included in the AIA Command. The AIA Command also includes information indicating that NextGen services are allowed for this mobile device (e.g. a 'NextGen service access allowed' flag and/or the like). These additional security related parameters (NextGen/slice related authentication vectors) may be used by the MME 9 when it interacts with the NextGen control plane manager 15.

In case the mobile device 3 is not allowed access to the NextGen service, the HSS 10 indicates this to the MME 9 by, for example, not setting the NextGen service access allowed flag in the Authentication-Information-Answer (AIA) Command (or by setting an appropriate 'NextGen service access not allowed' flag). In this case, the MME 9 has two options: i) either accept the mobile device's attach request but limit it to EPS services; or ii) reject the attach request (by generating and sending an appropriate response to the mobile device 3). If the attach request is rejected, then the MME 9 informs the mobile device 3 of the rejection by setting an appropriate 'NAS reject error cause', for example, a "NextGen Service request denied" cause. Then, the mobile device 3 may generate and send another attach request (limited to EPS access only).

After a successful authentication and security setup (e.g. cyphering setup) with the HSS 10 in step S102, the MME 9 proceeds to step S103, in which it downloads subscriber data (user context) associated with the mobile device 3 and completes security setup with the UE 3 in step S104. The MME 9 does so by generating and sending an appropriate Update-Location-Request (ULR) Command to the HSS 10, including a NextGen service access request flag. If the HSS 10 finds the NextGen service access request flag in the ULR Command, then the HSS 10 generates and sends an appropriate Update-Location-Answer (ULA) Command to the MME 9 with NextGen service access related parameters (in addition to any other parameters, e.g. LTE/EPC parameters). Such NextGen related parameters may include one or more mobility requirement parameter(s), subscribed slice related parameter(s), subscribed tenant related parameter(s), temporary ID(s), external ID(s), and/or the like. From the information downloaded from the HSS 10 (in step S103), the MME 9 obtains, in step S105, an indication that this particular mobile device 3 is entitled for 5G services (and/or an indication that this user's data and corresponding signalling, is to be relayed to the 5G core network 8). The MME 9 may also apply a specific selection procedure to select an appropriate Control Plane (CP) Network Function (NF) in the NextGen core network 8 (in this example, the NextGen control plane mobility management entity 15). For example, the selection of an appropriate CP NF may be based on one or more of: location of the mobile device 3; subscribed slice; subscribed tenant; UE usage type parameter, Decor ID; etc. Optionally the MME 9 may perform a DNS request including an additional (NextGen related) parameter as described above, in order to resolve a suitable NextGen CP NF for the LTE mobile device 3.

Next, as generally shown in step S106, the MME 9 selects an appropriate serving gateway (SGW) e.g. as defined in 3GPP TS 23.401 V14.0.0. In step S107, the MME 9 performs a session setup procedure with the SGW 1 1. As part of this procedure, the SGW 1 1 may establish a UE-specific context for connection towards the NextGen UP NF 16 and optionally for matching QoS parameters between NextGen core network 8 and EPC 7 for both uplink and downlink direction of data transmission between the NextGen UP NF 16 and the (LTE) base station 5.

Optionally the SGW selection procedure can be extended as follows, the MME 9 may select an appropriate UP NF in the EPC 7 (in this example, SGW or (SGW-U) 1 1 ) and configure it to connect to the UP NF 16 in the NextGen core network 8 (by carrying out a session setup procedure as shown in step S107). It will be appreciated that the UP NF selection procedure may be based on the current EPC SGW selection procedure, although in this case the MME 9 may be configured to use additional criteria for the SGW selection, e.g. capabilities of the SGW 1 1 to connect to the NextGen core network 8 (where different protocols or encapsulations may be used in the user plane than in the EPC 7). The selected SGW 1 1 may also need to perform a matching between the quality of service (QoS) parameters used in the NextGen core network 8 and in the EPC 7. It will be appreciated that the SGW 11 may be split into separate control plane (SGW-C) and user plane (SGW-U) functional entities in accordance with the Control and User Separation (CUPS) split architecture defined by 3GPP. In this case, the MME 9 may also be configured to inform the 'SGW-C entity about the control plane connection to the NextGen core network 8 (CP NF 15). At this point, the MME 9 has two options, which are indicated as option (a) and option (b) in Figure 7. It will be appreciated that the option followed may depend on operator configuration, compatibility of the NextGen CP NF with the MME 9, and/or the like.

If the MME 9 is configured to follow option (a), then the MME 9 generates (using its interworking module 89) and sends, in step S108a, an appropriately formatted interworking request to the NextGen control plane manager 15. The MME's interworking request includes: i) information identifying the mobile device 3 (e.g. by its MSISDN, IMSI, NextGen related authentication vectors, slice related authentication vectors, NextGen specific temporary user identification, assigned Serving GW address information (e.g. an SGW-C IP address and associated TEID and SGW-U IP address and TEID and/or the like)); ii) information identifying a location of the mobile device 3 (e.g. topological location, such as cell/tracking area identifier and/or other geographical location); and iii) (optionally) information identifying one or more service that the mobile device is entitled to use (part of the subscriber profile) and that are to be delivered by the NextGen core network 8. It will be appreciated that, in this case, the MME 9 is configured to generate and send a signalling message (i.e. the 'Interworking Request' or similar) that is dedicated for conveying this information to the NextGen CP NF. However, it will also be appreciated that any suitable signalling message may be used, if appropriate.

Optionally, e.g. if the NextGen control plane manager 15 is connected to the HSS 10 (in the EPC 7), the NextGen control plane manager 15 may be configured to perform authentication and authorisation of the mobile device 3 for the entitled subscriber services (step S109a) in addition to the user authentication and authorisation in the EPC 7 (in step S102). Such additional user authentication and authorisation may be needed in order to guarantee the NextGen security requirement which might be stronger than one used for the EPC 7. The NextGen control plane manager 15 may interwork with the HSS 10 (using its subscriber context module 98) in order to obtain necessary subscriber information for user authentication and authorisation and/or to perform a challenge based user authentication between the mobile device 3 and the HSS 10.

If the NextGen control plane manager 15 accepts the MME's 9 request, then the NextGen control plane manager 15 and the User Plane Network Function (UP NF) 16 proceed with appropriate procedures for UP session establishment in the NextGen core network 8, between the NextGen UP NF 16 and the selected SGW 1 1 , using the received information. Two possible options for the setup of the UP sessions include: (1 ) an option in which the CUPS feature is used and the setup of the UP sessions in the SGW-U and NextGen UP NF is performed over the control plane and (2) an option in which the GTP-C protocol is used between SGW and NextGen UP NF (S1 10a). Option (1 ) is shown in step S1 12a assuming that the SGW-C and MME are co- located. If the SGW-C and MME are not co-located, then the MME, after receiving the signalling from NextGen CP with NextGen UP NF ID, updates over S1 1 interface the SGW-C, and consequentially, the SGW-C updates the SGW-U.

It will be appreciated that this step may comprise contacting other NextGen nodes (e.g. one or more of a service manager node, a policy and charging manager node, and/or a subscriber manager node).

Although the procedures for resource reservation within the NextGen core network 8 are not described in detail herein, it will be appreciated that the NextGen control plane manager 15 (and/or other control plane functional entity) includes appropriate functionality for managing the NextGen CP NF. If the procedures described in steps S108a, S109a, and S110a (if used) are successful and if the NextGen control plane manager 15 accepts the MME's 9 request, then it replies back to the MME 9 indicating that the request was accepted (step S1 1 1 a) and an appropriate user plane connection between the SGW 1 1 and the NextGen UP NF 16 was successfully setup. Otherwise, i.e. if the procedures described in steps S108a, S109a, and S110a (if used) are not successful and/or if the NextGen control plane manager 15 does not accept the MME's 9 request, it replies back to the MME 9 indicating that the request was not accepted. In this situation, it is up to the MME 9 to decide (e.g. based on operator configuration) whether the mobile device 3 is accepted by the EPC 7 only (and allow the mobile device 3 to access the EPC 7 but not the NextGen core network 8) or the ATTACH procedure is failed. The MME 9 may be configured to inform the mobile device 3 about such a conditional failure or entire failure by generating and sending an appropriate ATTACH accept message with cause information "Only EPS accepted" or an ATTACH reject message with cause information "attach failed in the NextGen network" respectively.

If the EPC applies Control and User Plane Separation (CUPS) feature, the MME 9 forwards the NextGen UP NF information obtained from the NextGen control plane to the SGW-CP entity. The SGW-C entity performs a session update procedure towards the SGW-UP entity. For simplicity, Figure 7 does not show the explicitly the SGW-C entity, thus the shown SGW entity is SGW-UP entity in CUPS feature. The update procedure towards the SGW-UP entity is shown in step S1 12a.

If the MME 9 is configured to follow option (b), then the MME 9 (using its interworking module 89) relays, in step S108b, the NAS message (e.g. Attach Request) received from the mobile device 3 to the NextGen control plane manager 15. In other words, in this case the MME 9 is configured to forward the original NAS message towards the NextGen CP NF, but (optionally) the MME 9 may also include additional information as described above with reference to step S108a (e.g. UE context obtained from the HSS 10 and/or UE location info). In step S109b, the NextGen control plane manager 15 (by contacting the HSS 10) authorises the mobile device 3, using the information received in step S108b.

If steps S108b and S109b are successful, then the NextGen control plane manager 15 proceeds (in step S110b) with the resource reservation (session establishment) procedure involving the NextGen UP NF 16 and the SGW 11 , as described above with reference to step S1 10a, then the NextGen control plane manager 15 sends, in step S1 1 1 b, an appropriately formatted NAS signalling message (e.g. an 'Attach Complete' message) to the MME 9 (if the procedures described in steps S108b, S109b, and S1 10b are successful). Otherwise, the NextGen control plane manager 15 replies to the MME 9 indicating that the request was not accepted (e.g. by generating and sending an 'Attach Failure' message).

Although not shown in Figure 7, the NextGen CP NF may also be configured to indicate, to the MME 9 (e.g. in step S1 1 1 a or step S1 1 1 b), an address and/or other suitable ID of the NextGen UP NF allocated to the mobile device 3. Such address and/or ID may include, for example, one or more IP address(es) associated with the UP NF 16 and/or one or more tunnel identifier(s) (such as a 'GTP-U TEID') associated with the UP NF 16 (if tunnelling is applied).

Upon reception of the indication, in step S11 1 a/S11 1 b, that the interworking/NAS request was successful and that the NextGen core network 8 has reserved resources for the mobile device 3, the MME 9 starts relaying all subsequent NAS signalling for this session to the corresponding NextGen CP NF node 15.

It will be appreciated that QoS matching and/or transport (tunnelling) of data are handled by the SGW 1 1 (rather than the NextGen UP NF 16), in order to keep the NextGen UP NF 16 unaware of any access system specifics. However, in some systems, it may be possible to provide QoS matching and data transport handling (e.g. GTP or Proxy Mobile IPv6 (PMIP) tunnelling) by the NextGen UP NF 16 (and hence avoid changes to SGWs currently deployed in LTE networks).

In step S1 13, the EPC 7 proceeds with the attach procedure as per 3GPP TS 23.401 V14.0.0, and in step S114 the base station 5 sends, to the MME 9, an appropriate message (e.g. an Attach Complete message and/or the like) to conclude the procedure initiated in step S101.

As generally shown in step S1 15, at this point, the NextGen core network 8 is ready for the upcoming user plane interworking with the EPC 7, and all signalling from the mobile device 3A can be relayed to the NextGen control plane manager 15. In other words, the LTE capable mobile device 3A is successfully attached to the 5G capable NextGen core network 8.

It will be appreciated that after a successful user plane setup, service authorization to the NextGen service (e.g. a challenge based authorisation) may take place between the mobile device 3 and a radius server or an AAA server located in the external network. If the NextGen service authorisation fails, then the NextGen UP NF 16 may initiate a session disconnection procedure in order to release all resources related to the mobile device 3.

The solution above assumes that the IP address or IP prefix for the UE is assigned from the NextGen system, either from the NextGen CP NF or from the NextGen UP NF. In such a case the NextGen UP NF serves as IP anchor and the EPC's SGW serves as mobility anchor. In this case, when the UE moves within the LTE access, the MME can apply SGW relocation procedure due to UE mobility.

Whilst the procedures described above are for session establishment / initial network attachment as an example, it will be appreciated that the described signalling procedures may also be applicable to the establishment of additional data plane connection(s), known as multiple PDU sessions or PDU connections.

Operation - second example

Figure 8 is a timing diagram (message sequence chart) illustrating another example process performed by components of the system 1 when performing interworking in the system of Figure 6 (e.g. for LTE-only mobile devices).

The procedure begins in step S201 , in which the mobile device 3 (using its LTE module 3A) generates and sends, to the base station 5, an appropriate signalling message for initiating an attachment procedure with the EPC 7 (MME 9). For example, the mobile device 3 may be configured to generate (using its LTE module 3A) and send an 'Attach Request' signalling message as specified in 3GPP technical specification (TS) 23.401 V14.0.0. If the mobile device 3 is both LTE and 5G RAT capable, then the mobile device 3 indicates this capability in its signalling message to the MME 9, by appropriately setting a number of NextGen related parameters together with NAS parameters for the requested LTE access. The NextGen related parameters may include an appropriate NextGen specific temporary user identification, a NextGen service request flag, UE 5G radio capability, information identifying one or more (NextGen) core network slice instances (NSI), Multi Dimensional Descriptor (MDD), Tenant ID, Slice type, and/or the like. Such NextGen related parameters may be set either as individual NAS parameter(s) or set in an appropriately formatted NextGen NAS container parameter. The base station 5 is configured to forward the signalling message to the MME 9 (selected by the base station 5, if more than one MME are provided in the EPC 7) as described in 3GPP TS 23.401.

As generally shown in step S202, the EPC 7 authenticates the mobile device 3. This procedure is initiated by the MME 9 generating and sending an appropriately formatted Authentication-Information-Request (AIR) Command to the HSS 10. If the mobile device 3 is 5G capable (e.g. indicated by an appropriate NextGen Service request flag in the ATTACH message), then the MME 9 also includes the NextGen access request flag (and/or the like) in the AIR command in addition to any further parameter normally included in this command. If the HSS 10 finds the NextGen access request flag in the Authentication-Information-Request (AIR) Command from the MME 9, then the HSS 10 checks whether the mobile device 3 has a valid subscription to access to the NextGen service or not. If the HSS 10 determines that mobile device 3 has a valid subscription to access to the NextGen service, the HSS 10 generates and sends an appropriately formatted Authentication-Information- Answer (AIA) Command to the MME 9, including NextGen related authentication vectors, slice related authentication vectors (for all subscribed slides) in addition to the parameter normally included in the AIA Command. The AIA Command also includes information indicating that NextGen services are allowed for this mobile device (e.g. a 'NextGen service access allowed' flag and/or the like). These additional security related parameters (NextGen/slice related authentication vectors) may be used by the MME 9 when it interacts with the NextGen control plane manager 15.

After a successful authentication and security setup with the HSS 10 in step S202, the MME 9 proceeds to step S203, in which it downloads subscriber data (user context) associated with the mobile device 3 and completes security setup with the UE 3 in step S204. The MME 9 does so by generating and sending an appropriate Update- Location-Request (ULR) Command to the HSS 10, including a NextGen service access request flag. If the HSS 10 finds the NextGen service access request flag in the ULR Command, then the HSS 10 generates and sends an appropriate Update- Location-Answer (ULA) Command to the MME 9 with NextGen service access related parameters (in addition to any other parameters, e.g. LTE/EPC parameters). Such NextGen related parameters may include one or more mobility requirement parameter(s), subscribed slice related parameter(s), subscribed tenant related parameter(s), temporary ID(s), external ID(s), and/or the like.

At this point, the MME 9 has two options, which are indicated as option (a) and option (b) in Figure 8. It will be appreciated that the option followed may depend on operator configuration, compatibility of the NextGen CP NF with the MME 9, and/or the like.

If the MME 9 is configured to follow option (a), then the MME 9 generates (using its interworking module 89) and sends, in step S206a, an appropriately formatted interworking request to the NextGen control plane manager 15. The MME's interworking request includes: i) information identifying the mobile device 3 (e.g. by its MSISDN, IMSI, NextGen related authentication vectors, slice related authentication vectors, NextGen specific temporary user identification, assigned Serving GW address information (e.g. an SGW-C IP address and associated TEID and SGW-U IP address and TEID and/or the like)); ii) information identifying a location of the mobile device 3 (e.g. topological location, such as cell/tracking area identifier and/or other geographical location); and iii) (optionally) information identifying one or more service that the mobile device is entitled to use (part of the subscriber profile) and that are to be delivered by the NextGen core network 8. It will be appreciated that, in this case, the MME 9 is configured to generate and send a signalling message (i.e. the 'Interworking Request' or similar) that is dedicated for conveying this information to the NextGen CP NF. However, it will also be appreciated that any suitable signalling message may be used, if appropriate.

Optionally, e.g. if the NextGen control plane manager 15 is connected to the HSS 10 (in the EPC 7), the NextGen control plane manager 15 may be configured to perform authentication and authorisation of the mobile device 3 for the entitled subscriber services (step S207a) in addition to the user authentication and authorisation in the EPC 7 (in step S202). Such additional user authentication and authorisation may be needed in order to guarantee the NextGen security requirement which might be stronger than one used for the EPC 7. The NextGen control plane manager 15 may interwork with the HSS 10 (using its subscriber context module 98) in order to obtain necessary subscriber information for user authentication and authorisation and/or to perform a challenge based user authentication between the mobile device 3 and the HSS 10. If the NextGen control plane manager 15 accepts the MME's 9 request, then the NextGen control plane manager 15 and the User Plane Network Function (UP NF) 16 proceed with appropriate procedures for UP session establishment in the NextGen core network 8, between the NextGen UP NF 16 and the selected SGW 1 1 , using the received information.

If the procedures described in steps S206a and S207a are successful and if the NextGen control plane manager 15 accepts the MME's 9 request, then it replies back to the MME 9 indicating that the request was accepted (step S208a). Otherwise, i.e. if the procedures described in steps S206a and S207a are not successful and/or if the NextGen control plane manager 15 does not accept the MME's 9 request, it replies back to the MME 9 indicating that the request was not accepted. In this situation, it is up to the MME 9 to decide (e.g. based on operator configuration) whether the mobile device 3 is accepted by the EPC 7 only (and allow the mobile device 3 to access the EPC 7 but not the NextGen core network 8) or the ATTACH procedure is failed. The MME 9 may be configured to inform the mobile device 3 about such a conditional failure or entire failure by generating and sending an appropriate ATTACH accept message with cause information "Only EPS accepted" or an ATTACH reject message with cause information "attach failed in the NextGen network" respectively.

If the MME 9 is configured to follow option (b), then the MME 9 (using its interworking module 89) relays, in step S206b, the NAS message (e.g. Attach Request) received from the mobile device 3 to the NextGen control plane manager 15. In other words, in this case the MME 9 is configured to forward the original NAS message towards the NextGen CP NF, but (optionally) the MME 9 may also include additional information as described above with reference to step S206a (e.g. UE context obtained from the HSS 10 and/or UE location info).

In step S207b, the NextGen control plane manager 15 (by contacting the HSS 10) authorises the mobile device 3, using the information received in step S206b.

If steps S206b and S207b are successful, then the NextGen control plane manager 15 sends, in step S208b, an appropriately formatted NAS signalling message (e.g. an 'Attach Accept' message) to the MME 9. Otherwise, the NextGen control plane manager 15 replies to the MME 9 indicating that the request was not accepted (e.g. by generating and sending an 'Attach Failure' message). Although not shown in Figure 8, the NextGen CP NF may also be configured to indicate, to the MME 9 (e.g. in step S208a or step S208b), an address and/or other suitable ID of the NextGen UP NF allocated to the mobile device 3. Such address and/or ID may include, for example, one or more IP address(es) associated with the UP NF 16 and/or one or more tunnel identifier(s) (such as a 'GTP-U TEID') associated with the UP NF 16 (if tunnelling is applied).

Upon reception of the indication, in step S208a/S208b, that the interworking/NAS request was successful and that the NextGen core network 8 has reserved resources for the mobile device 3, the MME 9 starts relaying all subsequent NAS signalling for this session to the corresponding NextGen CP NF node 15.

Next, as generally shown in step S208, the MME 9 selects an appropriate serving gateway (SGW) e.g. as defined in 3GPP TS 23.401 V14.0.0. In step S209, the MME 9 performs a session setup procedure with the SGW 1 1. The selection of the SGW 11 and session setup are similar to that described with reference to steps S106 and S107 of the procedure of Figure 7.

Once the session is setup with the selected SGW 1 1 the MME 9 requests, at step S21 1 -1 , a UP session by sending an appropriately configured UP session request, with an identifier of the selected SGW 11 , to the NextGen CP NF 15. The NextGen CP NF 15 performs, at step S212, an appropriate session setup procedure with the NextGen UP NF 16 and, when the session is setup responds to the UP session request with appropriately configured UP session response at step S21 1 -2.

The procedure continues in much the same manner as that of Figure 7 and Steps S213 to S215 correspond to steps S1 13 to S115 accordingly,

Operation - third example

Figure 9 illustrates another signalling interworking scenario for the provision of NextGen services for LTE mobile devices. The nodes shown in Figure 9 correspond to like-numbered nodes shown in Figure 6, thus their description is omitted herein for simplicity. Figure 6 also shows the radio access network 6 (labelled '5G RAT') for connecting 5G-capable mobile devices 3 to the NextGen core network 8 and the external network 20 using an appropriate 5G (non-LTE) radio access technology.

Figure 10 is a timing diagram (message sequence chart) illustrating an example process performed by components of the system 1 when performing interworking for a 5G-capable mobile device 3. In this example, the EPC 7 and the NextGen core network 8 prepare for handover of the mobile device 3B between the legacy network (in this case, LTE) and 5G networks. It will be appreciated that, in this example, the mobile device 3 is both LTE and 5G capable, i.e. it includes both an LTE module 3A and a 5G module 3B.

Figure 10 depicts a high-level representation of mobility management related interworking when the mobile terminal 3 (for any reason) performs a handover the LTE access network (base station 5) to the NextGen access network 6. Such a handover may be necessary, for example, when there is inadequate LTE or 5G/eLTE coverage in a transition phase (i.e. whilst network migration is incomplete). In this example, the NextGen core network 8 is able to initiate resource reservation procedures to anticipate an eventual handover from the LTE RAT to the 5G RAT.

In more detail, the procedure begins in step S301 , in which the mobile device 3 (using its LTE module 3A) generates and sends, to the base station 5, an appropriate signalling message for initiating an attachment procedure with the EPC 7 (MME 9). It will be appreciated that step S301 corresponds to S101 described above. The base station 5 forwards the signalling message to the MME 9, and the EPC 7 authenticates the mobile device 3 (in step S302). As part of this authentication procedure, the MME 9 downloads, from the HSS 10, the user profile associated with the mobile device 3. In this example, as generally shown in step S305, the MME 9 obtains (from the user profile downloaded from the HSS 10) an indication that this particular mobile device 3 is 5G capable. The MME 9 may also apply a specific selection procedure to select an appropriate Control Plane (CP) Network Function (NF) in the NextGen core network 8 as described above with reference to step S105. Next, the MME 9 generates (using its interworking module 89) and sends, in step S307, an appropriately formatted interworking request to the NextGen control plane manager 15, the request including information identifying the mobile device 3 (e.g. by its MSISDN, IMSI, etc.) and optionally the associated subscriber context loaded from the HSS 10 (e.g. services that the mobile device 3 subscribes to). As generally shown in optional step S308, for example, if the NextGen control plane manager 15 is connected to the HSS 10 (in the EPC 7) and if the MME 9 did not send the subscriber context in step S307, the NextGen control plane manager 15 may be configured to perform authorisation of the mobile device 3 for the entitled subscriber services and obtain the subscriber context associated with the mobile device 3.

In step S309, if the NextGen control plane manager 15 accepts the MME's 9 request, then it preloads the subscriber information for use by the NextGen control plane nodes, using the received/obtained information. It will be appreciated that this step may comprise contacting other NextGen nodes (e.g. a service manager node, a policy and charging manager node, and/or a subscriber manager node).

If the procedures in steps S307, S308, and S309 are successful and if the NextGen control plane manager 15 accepts the MME's 9 request, then it replies back to the MME 9 indicating that the request was accepted (step S310). Otherwise, i.e. if the procedures described in steps S307, S308, and S309 are not successful and/or if the NextGen control plane manager 15 does not accept the MME's 9 request, it replies back to the MME 9 indicating that the request was not accepted.

Steps S313 and S314 correspond to steps S113 and S114, respectively. As generally shown in step S315, at this point, the NextGen core network 8 is ready for a potential user handover coming from the EPC 7. In other words, the LTE and 5G capable mobile devices 3 can perform a handover between the (LTE) base station 5 and the 5G access network 6, when appropriate.

It can be seen, therefore, that the above examples provide a number of advantages, including (but not limited to) the following:

- By providing an appropriate reference point (e.g. 'S10') between a pre-5G network (in this case LTE), the mobility manager (MME) and the NextGen control plane manager are able to perform interworking for handling mobility related signalling (amongst other) and/or interworking for the provision of services via the NextGen core network even for mobile devices that are not compatible with 5G standards.

- It is possible to transfer subscriber information (context), kept at the LTE/EPC network (e.g. for LTE subscribers / LTE-only UEs), to the NextGen core network (either directly from the HSS or via the MME).

- Control plane data support can be exchanged between the MME (LTE) and the NextGen control plane manager (5G). - It is possible to establish signalling association and exchange signalling between the LTE MME and the NextGen control plane manager.

- The MME is able to relay NAS signalling messages between the mobile device (or the MME) and the NextGen mobility manager (even if the mobile device itself does not support 5G communication technologies).

- It is possible to deploy and provide services nested / served by the NextGen / 5G core network to LTE-only devices that do support a 5G radio interface or other legacy mobile devices that can be authenticated in the EPC domain only.

Modifications and Alternatives

Detailed embodiments have been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above embodiments whilst still benefiting from the inventions embodied therein. By way of illustration only a number of these alternatives and modifications will now be described. In the above embodiments, the base station uses a 3GPP radio communications (radio access) technology to communicate with the mobile device. However, any other radio communications technology (i.e. WLAN, Wi-Fi, WiMAX, Bluetooth, etc.) can be used between the base station and the mobile device in accordance with the above embodiments. The above embodiments are also applicable to 'non-mobile' or generally stationary user equipment.

It will be appreciated that whilst only one option has been described with reference to Figure 10 (i.e. an option based on a dedicated 'Interworking Request') option (b) described with reference to Figure 7 may also be applied for mobility / handover purposes (i.e. appropriate NAS signalling may be used / relayed between the EPC and the NextGen core).

Figure 1 1 illustrates schematically another cellular telecommunication system to which exemplary embodiments of the invention may be applied. In this example, relaying of control plane data is realised via the control plane (MME or SGW-C) rather than the user plane (SGW-U). This example may be beneficial, for example, for cellular Internet of Things (CloT) devices and/or other communication devices (including conventional user equipment) which devices have a relatively low amount of data to send/receive and/or communicate relatively infrequently. Such small data transmission may include IP data, non-IP data, and/or SMS. It will be appreciated that during the transition period towards 5G, CloT services deployed in the LTE network may continue to transmit and receive data over the control plane in 5G service environment. In order to keep services running with minimal impacts to the deployed CloT devices (and other CloT capable LTE devices), data communication within the CloT control plane (transmitted through the LTE MME) may be relayed towards the NextGen control plane manager, responsible for mobility management within the NextGen network.

In the above description, the mobile device, the base station, the MME, and the NextGen management entity are described for ease of understanding as having a number of discrete functional components or modules. Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the invention, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities.

It can be seen, therefore, that in one example, there is provided a core network apparatus for a first type of communication network, the core network apparatus comprising: a controller configured to determine whether a communication device is capable of using a service that is configured for provision via a second type of communication network; and a transceiver configured to transmit a message, towards a second core network of the second type of communication network, to initiate interworking between a first core network in the first type of communication network and the second core network in the second type of communication network for the provision of the service.

The transceiver may be configured to receive a non-access stratum signalling message from the communication device, and the controller may be configured to perform the determination of whether the communication device is capable of using the service that is configured for provision via the second type of communication network following receipt of the non-access stratum signalling message.

The controller may be configured to perform the determination of whether the communication device is capable of using the service that may be configured for provision via the second type of communication network as part of attach procedure initiated by the non-access stratum signalling message.

The transceiver may be configured to receive, from a home subscriber server, HSS, an indication that the communication device is capable of using the service and the controller may be configured to perform the determination of whether the communication device is capable of using the service that is configured for provision via the second type of communication network based on the indication.

The transceiver may be configured to receive, from the communication device, an indication that the communication device is capable of using the service and the controller may be configured to perform the determination of whether the communication device is capable of using the service that is configured for provision via the second type of communication network based on the indication.

The transceiver may be configured to transmit the message to initiate interworking to a control plane network function associated with the second core network, and the message to initiate interworking may include at least one of: information identifying the communication device; information identifying a location of the communication device; and information identifying at least one service that the communication device is capable of using. The message to initiate interworking may comprise a non-access stratum signalling message. The message to initiate interworking may comprise an explicit interworking request.

The transceiver may be configured to receive, from a home subscriber server, HSS, a first indication relating to the second type of communication network, receive, from the communication device, a second indication relating to access for the second type of communication network, and the controller may be configured to select a core network apparatus in the second type of communication network based on at least one of the first indication and the second indication.

The first type of communication network and the second type of communication network may each operate in accordance with a different respective set of communication standards. In another example, there is provided a core network apparatus for communicating with a first type of communication network, the core network apparatus included in a second type of communication network, the core network apparatus comprising: a transceiver configured to receive a message, from a first core network in the first type of communication network, to initiate interworking between the first core network and a second core network in the second type of communication network for the provision, for a communication device, of a service that is configured for provision via the second type of communication network.

The core network apparatus may further comprise a controller configured to determine whether the communication device is capable of using the service that is configured for provision via the second type of communication network.

The transceiver may be configured to receive, from a home subscriber server, HSS, an indication that the communication device is capable of using the service and the controller may be configured to perform the determination of whether the communication device is capable of using a service that is configured for provision via the second type of communication network based on the indication.

The message to initiate interworking may include at least one of: information identifying the communication device; information identifying a location of the communication device; and information identifying at least one service that the communication device is entitled to use.

The transceiver may be configured to transmit a message to a mobility management entity associated with the first core network and the message may include information identifying a user plane controller allocated to the communication device. The information identifying a user plane controller may comprise an address.

The core network apparatus may be configured to carry out resource reservation for the communication device and/or preload a subscriber context associated with the communication device based on the received message to initiate interworking. The first type of communication network and the second type of communication network may each operate in accordance with a different respective set of communication standards.

The service may comprise at least one of: a service associated with the first core network which is provided via the second core network; a service of the second core network that the communication device capable of using whilst being attached to the first core network; and mobility/handover between a legacy access network and a 5G access network In the above embodiments, a number of software modules were described. As those skilled in the art will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied to the base station, to the mobility management entity, or to the mobile device as a signal over a computer network, or on a recording medium. Further, the functionality performed by part or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of the base station, the mobility management entity, the NextGen management entity, or the mobile device in order to update their functionalities. Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

Claims

A core network apparatus for a first type of communication network, the core network apparatus comprising: a controller configured to determine whether a communication device is capable of using a service that is configured for provision via a second type of communication network; and a transceiver configured to transmit a message, towards a second core network of the second type of communication network, to initiate interworking between a first core network in the first type of communication network and the second core network in the second type of communication network for the provision of the service.

The core network apparatus according to claim 1 , wherein the transceiver is configured to receive a non-access stratum signalling message from the communication device, and wherein the controller is configured to perform the determination of whether the communication device is capable of using the service that is configured for provision via the second type of communication network following receipt of the non-access stratum signalling message.

The core network apparatus according to claim 2, wherein the controller is configured to perform the determination of whether the communication device is capable of using the service that is configured for provision via the second type of communication network as part of attach procedure initiated by the non-access stratum signalling message.

The core network apparatus according to any of claims 1 to 3, wherein the transceiver is configured to receive, from a home subscriber server, HSS, an indication that the communication device is capable of using the service and wherein the controller is configured to perform the determination of whether the communication device is capable of using the service that is configured for provision via the second type of communication network based on the indication.

The core network apparatus according to any of claims 1 to 3, wherein the transceiver is configured to receive, from the communication device, an indication that the communication device is capable of using the service and wherein the controller is configured to perform the determination of whether the communication device is capable of using the service that is configured for provision via the second type of communication network based on the indication.

The core network apparatus according to any of claims 1 to 5, wherein the transceiver is configured to transmit the message to initiate interworking to a control plane network function associated with the second core network, and wherein the message to initiate interworking includes at least one of: information identifying the communication device; information identifying a location of the communication device; and information identifying at least one service that the communication device is capable of using.

The core network apparatus according to any of claims 1 to 6, wherein the message to initiate interworking comprises a non-access stratum signalling message.

The core network apparatus according to any of claims 1 to 6, wherein the message to initiate interworking comprises explicit interworking request.

The core network apparatus according to claim 1 , wherein

the transceiver is configured to

receive, from a home subscriber server, HSS, a first indication relating to the second type of communication network,

receive, from the communication device, a second indication relating to access for the second type of communication network, and

wherein the controller is configured to select a core network apparatus in the second type of communication network based on at least one of the first indication and the second indication.

The core network apparatus according to any of claims 1 to 9, wherein the first type of communication network and the second type of communication network each operate in accordance with a different respective set of communication standards.

1 1. A core network apparatus for communicating with a first type of communication network, the core network apparatus included in a second type of communication network, the core network apparatus comprising: a transceiver configured to receive a message, from a first core network in the first type of communication network, to initiate interworking between the first core network and a second core network in the second type of communication network for the provision, for a communication device, of a service that is configured for provision via the second type of communication network.

12. The core network apparatus according to claim 1 1 , further comprising a controller configured to determine whether the communication device is capable of using the service that is configured for provision via the second type of communication network.

13. The core network apparatus according to claim 12, wherein the transceiver is configured to receive, from a home subscriber server, HSS, an indication that the communication device is capable of using the service and the controller is configured to perform the determination of whether the communication device is capable of using a service that is configured for provision via the second type of communication network based on the indication.

14. The core network apparatus according to any of claims 1 1 to 13, wherein the message to initiate interworking includes at least one of: information identifying the communication device; information identifying a location of the communication device; and information identifying at least one service that the communication device is entitled to use.

15. The core network apparatus according to any of claims 1 1 to 14, wherein the transceiver is configured to transmit a message to a mobility management entity associated with the first core network and wherein the message includes information identifying a user plane controller allocated to the communication device.

16. The core network apparatus according to claim 15, wherein the information identifying a user plane controller comprises an address. The core network apparatus according to any of claims 1 1 to 16, configured to carry out resource reservation for the communication device and/or preload a subscriber context associated with the communication device based on the received message to initiate interworking.

The core network apparatus according to any of claims 1 1 to 17, wherein the first type of communication network and the second type of communication network each operate in accordance with a different respective set of communication standards.

The core network apparatus according to any of claims 1 1 to 18, wherein the service comprises at least one of: a service associated with the first core network which is provided via the second core network; a service of the second core network that the communication device capable of using whilst being attached to the first core network; and mobility/handover between a legacy access network and a 5G access network

A system comprising a communication device, the core network apparatus according to any of claims 1 to 10, and the core network apparatus according to any of claims 1 1 to 19.

A method performed by a core network apparatus of a first type of communication network, the method comprising: determining whether a communication device is capable of using a service that is configured for provision via a second type of communication network; and transmitting a message, towards a second core network of the second type of communication network, to initiate interworking between a first core network in the first type of communication network and the second core network in the second type of communication network for the provision of the service.

A method performed by a core network apparatus communicating with a first type of communication network, the core network apparatus forming part of a second type of communication network, the method comprising: receiving a message, from a first core network, to initiate interworking between the first core network in the first type of communication network and the second core network in the second type of communication network for the provision, for a communication device, of a service that is configured for provision via the second type of communication network.

A computer program product comprising computer implementable instructions for causing a programmable computer device to perform the method according to claim 21 or 22.