ES2763199T3 - Methods and devices for using a VPLMN infrastructure by an HPLMN to terminate an IMS session establishment for a roaming user - Google Patents

Abstract

Method to provide a roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a first User Equipment (UE A) is associated with a Home Public Land Mobile Network (HPLMN) and where the first User Equipment (UE A) roams in a Visited Public Land Mobile Network (VPLMN), where the Home Public Land Mobile Network (HPLMN) comprises a first Internet Protocol Multimedia Subsystem (IMS) domain, where the Network Visited Public Land Mobile Network (VPLMN) comprises a second Internet Protocol Multimedia Subsystem (IMS) domain, and where the Visited Public Land Mobile Network (VPLMN) comprises a Roaming Edge Control Function (RBCF), where a Session establishment of an Internet Protocol Multimedia Subsystem (IMS) session requires the handling of control signaling and the establishment of a user plane route, where in ca so of a session establishment request originating from the first roaming User Equipment (UE A) (mobile origin case) towards a second User Equipment (UE B), the second User Equipment (UE B) being connected to a target network, the method comprises the steps of: - transmitting the second Internet Protocol Multimedia Subsystem (IMS) domain a session establishment request control signaling to the first Internet Protocol Multimedia Subsystem (IMS) domain ), - transmitting the first Internet Protocol Multimedia Subsystem (IMS) domain the session establishment request control signaling in direct direction to the Roaming Edge Control Function (RBCF) of the second Multimedia Subsystem domain of Internet Protocol (IMS), and wherein the second Internet Protocol Multimedia Subsystem (IMS) domain is used to handle the user-plane path and control signaling asso called to terminate the session establishment, whereby since the local media connection shall be applied for the first roaming User Equipment (UE A), the Roaming Edge Control Function (RBCF) provides a binding of - the signaling received by means of a loop through the first Internet Protocol Multimedia subsystem domain (IMS) in the Home Public Land Mobile Network (HPLMN) - with the media anchored due to the local connection in the second Multimedia Subsystem domain Internet Protocol (IMS) in the Visited Public Land Mobile Network (VPLMN).

Description

DESCRIPTION

Methods and devices for using a VPLMN infrastructure by an HPLMN to terminate an IMS session establishment for a roaming user

BACKGROUND

The present invention relates to a communication system. More particularly, and not by way of limitation, the invention relates to a method of providing roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a user equipment (UE) is associated with a Domestic Public Land Mobile Network (HPLMN) and where the User Equipment (UE) roams a Visited Public Land Mobile Network (VPLMN). Additionally, the invention relates to a Visited Public Land Mobile Network (VPLMN) to provide roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session. Additionally, the invention relates to a unit that provides a Roaming Edge Control Function (RBCF) in a Visited Land Public Mobile Network (VPL ^m N).

The IP Multimedia Subsystem (IMS), as defined by the Third Generation Association Project (3GPP), unites telephony and Internet technology providing an all-IP architecture for the telecommunications industry. The IMS is based on the Session Initiation Protocol (SIP) and makes use of the protocols defined within the Special Group on Internet Engineering (IETF). The system offers a network of servers and databases that assist a user agent with the task of establishing and managing sessions.

Various 3GPP standards describe the architecture for IMS that roams mobile networks. In this way, the infrastructure is divided into entities within the Visited Public Land Mobile Network (VPLMN) such as Radio Access, the Main Packet Network, the Policy and Charging Rules Function (PCRF) of the VPLMN, the IP Multimedia Subsystem ( IMS), Intermediary Call Session Control Function (P-CSCF) and entities within the Domestic Public Land Mobile Network (HPLMN) such as (IP Multimedia Subsystem (IMS) - Domestic Subscriber Server (HSS), Function Policy and Collection Rules (PCRF) of the HPLMN, Interrogation / Service Call Session Control Function (I / S-CSCF), IP Multimedia Subsystem (IMS) Application Servers (eg application server provided by the MMTEL service for VoIP).

Regarding roaming functionality, the standards define that the user plane (RTP / RTCP VoIP traffic) can be routed to the HPLMN (home routing) or to the target network (local connection) (see 3GPP TR 23.228 Annex M) . Additionally, the standards define methods for anchoring the media within the VPLMN and apply a handover from PS to local CS for an inbound roaming user with no impact on the HPLMN service domain or the remote user (see 3GPP TR 23.856).

The establishment of a roaming user session towards the remote end (called mobile origin situation) can be processed by implying the so-called Home Routing or by implying the so-called Local Connection.

Home Routing means that the IP Multimedia Subsystem (IMS) signaling and associated user plane are routed from the VPLMN through the HPLMN IP Multimedia Subsystem (IMS) domain. The HPLMN applies conventional functionalities to end the session towards the target User Equipment (UE) (UE part B) within its own access network or external networks (interconnection). The use of Home Routing results in inefficient routing of the user plane with increased resource consumption (IP network equipment) and IP transmission delays that jeopardize quality, eg. eg, VoIP and video sessions.

Local Connection according to 3GPP TR 23.228 Annex M means that the IP Multimedia Subsystem (IMS) signaling is routed from the VPLMN via the HPLMN IP Multimedia Subsystem (IMS) domain to the remote User Equipment (UE) Part B) within their own networks or outside, while the user plan is routed directly between VPLMN IP addresses / ports and the target network. The use of Local Connection is not applicable if the called user is served by a legacy Circuit Switching (CS) network. Additionally, the use of Local Connection results in the challenge that the target network or a transit network between the VPLMN or the HPLMN on one side and the target networks on the other side receive the signaling and user plane regardless of different networks. This causes problems related to:

- correlation,

- security (as it is not evident if the input user plane is actually associated with the input signaling)

- accounting between the termination network and the other networks involved (since it is not clear whether the termination network will receive tariffs from the network that provides the signaling or from the network that provides the user plane),

- accounting between VPLMN and HPLMN (since the VPLMN, even if it is aware of the target IP address that the user plane is routing to, cannot apply the target IP address as criteria to count the target country / network (CC, NDC) as applied for CS roaming inherited),

- quality assurance between multiple networks (HPLMN, VPLMN, target network, transit networks), as well as

- local number portability (since the local numbering scheme and / or the portability status on the remote side may be unknown to the HPLMN).

Similar problems arise when an HPLMN IMS domain ends an inbound media session to a roaming user (called a mobile termination situation).

Send the HPLMN Service Call Status Control Function (S-CSCF) signaling (SIP INVITE) directly to the Call Broker Status Control Function (P-CSCF) based on the IP address of the Function Call Intermediate Status Control (P-CSCF) with user identity provided by the SIP line invitation request and the media from the HPLMN Media Gateway (MGW) to the VPLMN Media Gateway (MGW) based in the Media Gateway (MGW) IP address associated with the Call Broker State Control Function (P-CSCF) results in independent IP routing for SIP signaling and means that do not allow routing decisions within transit networks according to the SIP line invitation request, but allows IP routing to be applied only based on the IP address of the Call Broker Status Control Function (P-CSCF). This means that signaling data and media data are routed independently of each other. Transit networks may not apply routing and accounting for, eg. eg, a VoIP or Video session taking into account SIP and associated media streams, but they will provide IP only routing, which means that they can apply IP pairing only, which is different from inter-connection for media sessions.

COMPENDIUM

An object of the present invention is to provide a method and network that allow for improved roaming capability when using a User Equipment (UE) using the Internet Protocol Multimedia Subsystem (IMS) session for communication. The present invention is defined in the attached independent claims.

A method is described to provide a roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a first User Equipment (UE A) is associated to a Domestic Land Public Mobile Network (HPLMN) and in where the first User Equipment (UE A) roams a Visited Public Land Mobile Network (VPLMN), where the Domestic Public Land Mobile Network (HPLMN) comprises a first domain of Internet Protocol Multimedia Subsystem (IMS), in where the Visited Land Public Mobile Network (VPLMN) comprises a second domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Visited Land Mobile Public Network (VPLMN) comprises a Roaming Edge Control Function (RBCF), wherein in the case of a session establishment request originating from the first User Equipment (UE A) (mobile origin case) the method comprises the steps of:

- transmit the second Internet Protocol Multimedia Subsystem (IMS) domain a session establishment request to the first Internet Protocol Multimedia Subsystem (IMS) domain, and - transmit the first Internet Protocol Multimedia subsystem domain (IMS) a session establishment request to the Roaming Edge Control Function (RBCF).

The object of the present invention is achieved by a method according to claim 1.

According to the present invention, it is therefore advantageously possible to allow the HPLMN to apply the Local Connection to its roaming user using the infrastructure (i.e. the Roaming Edge Control Function (RBCF) of the VPLMN to terminate the session establishment As a result, the method advantageously allows:

- a media path optimized for VoIP sessions, Video sessions, or the like,

- a minimum number of media gateways and transcoding for user plane,

- routing based on local, national MNP / ENUM information from visited country,

- the use of Local Interconnection,

- the use of inter-operator accounting principles for equal inbound roaming for CS / GSM and PS / Internet Protocol Multimedia Subsystem (IMS),

- a seamless inter-operator accounting for roaming even in the case of Single Radio Voice Call Continuity (SRVCC) (i.e. the transfer of a Packet Switching (PS) functionality to a Circuit Switching functionality ( CS)),

- the use of inter-operator accounting principles for inter-connection equal to legacy interconnection, - full service control by the IMS domain of HPLMN.

In accordance with the present invention, it is preferred that a local media connection be made with the Roaming Edge Control Function (RBCF) by reassigning signaling control to the given media, which are anchored in VPLMN due to local connection, after signaling that has been looped through the domain HPLMN IMS.

It is further preferred according to the present invention that the Roaming Edge Control Function (RBCF) apply offline charging functionality.

In accordance with a still further embodiment of the present invention, it is preferred that the media path be routed directly via a Visited Land Mobile Mobile Network Media Gateway (VPLMN) serving the first User Equipment (UE A) and the Media Gateway from the Visited Public Land Mobile Network (VPLMN) to the second User Equipment (UE B).

The object of the present invention is achieved by a method according to claim 1.

In accordance with the present invention, additional session establishment to either remote side may be based on an association between control signaling and media being sent together to the next IMS entity, whereby this entity may be any of

- IBCF / I-BGF (interconnection of PS to another IMS network),

- MGCF / MGW (interconnection of CS to another CS network) or

- P-CSCF / A-BGF (serving a second User Equipment (UE B) connected to the given VPLMN) of the second Internet Protocol Multimedia Subsystem (IMS) domain.

Thus, it is advantageously possible that additional session establishment handling for the first roaming User Equipment (UE A) may be treated as a session establishment of a local non-roaming user of the second Protocol Protocol Multimedia Subsystem domain. Internet (IMS). In this way, it is advantageously possible that the media (voice, etc.) is not routed in an isolated way directly to the target Internet Protocol address (called the bare Internet Protocol stream without signaling) but that the RBCF node provides context between media and signaling and send correlated signaling along with media information to the next network node. The RBCF node provides management functionality with respect to additional session establishment so that, despite making a local connection, the second Internet Protocol Multimedia Subsystem (IMS) domain on the Visited Public Land Mobile Network (VPLMN) ) can:

- serve the first Visiting User Team in the same way as a user himself (non-visiting and not roaming), and

- direct the session of the first visiting User Team to the objective that has a link between signaling and the media.

In addition, a method of providing roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session is described, wherein a second User Equipment (UE B) is associated with a Domestic Domestic Land Mobile Network (HPLMN) and where the second User Equipment (UE B) roams a Visited Land Public Mobile Network (VPLMN), where the Domestic Land Public Mobile Network (HPLMN) comprises a third domain of Internet Protocol Multimedia Subsystem (IMS) , where the Visited Land Public Mobile Network (VPLMN) comprises a fourth domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Visited Land Public Mobile Network (VPLMN) comprises a Roaming Edge Control Function (RBCF ), where in case of a session establishment request that ends in the second User Equipment (UE B) (mobile termination case) the method comprises the steps of:

- transmit the Roaming Edge Control Function (RBCF) a session establishment request to the third domain of the Internet Protocol Multimedia Subsystem (IMS), and

- transmitting the first Internet Protocol Multimedia Subsystem (IMS) domain a session establishment request to the fourth Internet Protocol Multimedia Subsystem (IMS) domain.

The object of the present invention is further achieved by a method according to claim 4.

According to the present invention, it is thus advantageously possible to route a termination media session (eg, VoIP, video) from the Domestic Public Land Mobile Network (HPLMN) to the Visited Public Land Mobile Network (VPLMN) via networks aware transit services that apply routing and accounting decisions based on the SIP line invitation request. In this way, it is even possible to use legacy Circuit Switching (CS) networks as transit networks for routing the media session on the interconnection route.

It is preferred according to the present invention that the Roaming Edge Control Function (RBCF) receive a session establishment request by an Interconnection Edge Control Function (IBGF), this session establishment request being routed by at least one entity transfer.

According to the present invention, both

- the mobile origin case of a session establishment, and

- the mobile termination case of a session establishment.

To distinguish between these two cases, in the context of the present invention, reference is made to the first User Equipment for the mobile origin case and the second User Equipment for the mobile termination case. In the context of the present invention, a roaming situation is assumed, either for the first User Equipment or the second User Equipment or for both User Equipment. For both cases (of mobile origin and mobile termination) the Domestic Public Land Mobile Network (HPLMN) and the Visited Public Land Mobile Network (VPLMN) may be equipped with an Internet Protocol Multimedia Subsystem (IMS) domain. To distinguish between these two cases, in the context of the present invention, it is called as:

- the first Internet Protocol Multimedia subsystem domain (IMS) for the Domestic Domestic Land Mobile Network (HPLMN) of the first User Equipment (in the case of mobile origin),

- the second domain of the Internet Protocol Multimedia Subsystem (IMS) for the Visited Terrestrial Public Mobile Network (VPLMN) of the first User Equipment (in the case of mobile origin),

- the third domain of the Internet Protocol Multimedia Subsystem (IMS) for the Domestic Public Land Mobile Network (HPLMN) of the second User Equipment (in the case of mobile termination),

- the fourth domain of the Internet Protocol Multimedia Subsystem (IMS) for the Visited Terrestrial Public Mobile Network (VPLMN) of the second User Equipment (in the case of mobile termination).

The object of the present invention is also further achieved by a method according to claim 4. Additionally, a core network, namely a Visited Land Public Mobile Network (VPLMN) network is described to provide session related roaming functionality Internet Protocol Multimedia Subsystem (IMS), in which a first User Equipment (UE A) is associated with a domestic public land mobile network (HPLMN) and where the first user equipment (UE A) roams in the Visited Public Land Mobile Network (VPLMN), where the Domestic Public Land Mobile Network (HPLMN) comprises a first domain of the Internet Protocol Multimedia Subsystem (IMS), where the Visited Public Land Mobile Network (VPLMN) comprises a second Domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Visited Land Mobile Public Network (VPLMN) comprises a Roaming Edge Control Function (RBCF), where in case of a session establishment request that originates from the first User Equipment (UE A) (mobile origin case) the Visited Terrestrial Public Mobile Network (VPLMN) is configured to:

- transmitting a session establishment request from the second Internet Protocol Multimedia Subsystem (IMS) domain to the first Internet Protocol Multimedia Subsystem (IMS) domain, and

- the transmission of a session establishment request from the first Internet Protocol Multimedia subsystem domain (IMS) to the Roaming Edge Control Function (RBCF).

Additionally, a core network is described, specifically a Visited Public Land Mobile Network (VPLMN) to provide roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a second User Equipment (UE B) is associated with a Domestic Public Land Mobile Network (HPLMN) and where the second User Team (UE B) roams the Visited Public Land Mobile Network (VPLMN), where the Domestic Public Land Mobile Network ( HPLMN) comprises a third domain of the Internet Protocol Multimedia Subsystem (IMS), where the Visited Land Public Mobile Network (VPLMN) comprises a fourth domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Public Mobile Network Terrestrial Visited (VPLMN) comprises a Roaming Edge Control Function (RBCF), where in case of a session establishment request that ends in the second User Equipment (U E B) (case of mobile termination) the Visited Public Land Mobile Network (VPLMN) is configured to:

- transmission of a session establishment request from the Roaming Edge Control Function (RBCF) to the third domain of the Internet Protocol Multimedia Subsystem (IMS), and

- transmitting a session establishment request from the first Internet Protocol Multimedia Subsystem (IMS) domain to the fourth Internet Protocol Multimedia Subsystem (IMS) domain. The present invention also further relates to a core network, in particular a Visited Land Public Mobile Network (VPLMN) network according to claim 6.

Additionally, the present invention relates to a core network, in particular a Visited Land Public Mobile Network (VPLMN) according to claim 7.

In addition, a unit is described that provides a Roaming Edge Control Function (RBCF) in an inventive Core Network or Visited Land Public Mobile Network (VPLMN).

Additionally, a program is described that comprises a computer-readable program code for controlling a unit that provides a Roaming Edge Control Function (RBCF) in a Visited Public Land Mobile Network (VPLMN) according to the present invention.

In accordance with the present invention, roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session is provided as follows:

If a roaming user (i.e. a first User Equipment (UE A) or initiating Equipment in a mobile origin situation) establishes a media session, the VPLMN Call Broker Status Control Function (P-CSCF) , that is, the second Internet Protocol Multimedia Subsystem (IMS) domain, will forward the session establishment request (INVITE) to the HPLMN IMS domain (I / S-CSCF), that is, to the first Multimedia subsystem domain Internet Protocol (IMS). The HPLMN IMS domain will apply home services within its own application servers and decide to continue session establishment to the remote end.

The new method now allows the HPLMN to route additional session establishment to a Roaming Edge Control Function (RBCF) within the VPLMN. This is a new specific functionality within the VPLMN that provides capabilities beyond those applied by legacy Edge Gateways. These and other features, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The description is provided for purposes of example only, without limiting the scope of the invention. The reference figures cited below refer to the accompanying drawings.

In accordance with the present invention, a Domestic Public Land Mobile Network (HPLMN) can easily terminate an IMS media session from its IMS user (UE A) roaming in a strange VPLMN to the far end using the VPLMN infrastructure using thus the capabilities of a Roaming Edge Control Function (RBCF) within the VPLMN.

Preferably, the Roaming Edge Control Function (RBCF) provides access control to ensure permission to use its capabilities according to the rights assigned for a given HPLMN. Additionally, the Roaming Edge Control Function (RBCF) provides database queries for a session establishment requested by HPLMN to analyze the destination and apply local fixed number portability and / or mobile number portability as well as numbering rules. local to determine the destination network.

Additionally, the Roaming Edge Control Function (RBCF) supports termination of media session establishment to the VPLMN PS or CS access network or to other CS / PS networks through the interconnection infrastructure of the VPLMN.

It is preferred according to the present invention that the VPLMN infrastructure includes an Internet Protocol Multimedia Subsystem (IMS) domain, that is to say that it includes the Call Broker State Control Function (P-CSCF) and the associated GWs, and that Roaming Edge Control Function (RBCF) supports direct media path connectivity using the shortest path between VPLMN access gateways serving the calling party (UE A) (PDN-GW, IMS MGW (also called as A-BGF or A-SBC) and the GW of the VPLMN towards the remote party (UE B), which can be either a media gateway to the PS or CS access of the VPLMN or an interconnect media gateway to other CS or PS networks.

In accordance with the present invention, it is preferred that the inventive functionality in the VPLMn Call Broker State Control Function (P-CSCF) control what treatment is applied for originating IMS traffic from a roaming user (UE A). In this way, the Call Broker Status Control Function (P-CSCF) will verify the media description including IP addresses / ports (IMS SDP) forwarded back and forth between the calling party (UE A) and the remote side to decide on permissions for different modes of functionality of the roaming functionality, which may be characterized, e.g. ex. as follows:

- Local Connection with Roaming Edge Control Function (RBCF): the P-side SDP for media session restricted to VPLMN GW IP addresses, that is, the traffic will be terminated according to the inventive method,

- Home routing: the B-side SDP for media session restricted to HPLMN GW IP addresses, i.e. standard method will be applied to terminate such traffic,

- Local connection with direct routing: The B-side s Dp for media session can provide any target IP address, ie the standard method will be applied to terminate the traffic.

In accordance with the present invention, these roaming functionality functionality modes are dynamically negotiated between VPLMN P-CSCF (provides allowed modes) and HPLMN S-CSCF (provides required modes) within, eg. eg, IMS registration procedures, whereby VpLMN and HPLMN entities need to agree on a set of commonly allowed and required modes supported.

According to the present invention,

- the P-CSCF may forward a security token to the Domestic Public Land Mobile Network (HPLMN),

- the HPLMN retransmits the security token to the VPLMN Roaming Edge Control Function (RBCF), and

- the VPLMN RBCF verifies the token to restrict access to its capabilities for: (1) traffic originating within its own network (own P-CSCF / MGW) only and / or (2) traffic forwarded by an HPLMN that got permission to use the described method of the VPLMN.

In accordance with a preferred embodiment of the present invention, the Roaming Edge Control Function (RBCF) provides accounting information covering parameters such as:

- Service network (VPLMN),

- Served network (HPLMN),

- Part served (roaming part A subscribed to HPLMN),

- Media (Voice, video, ...),

-- Weather,

- Session duration,

- Called party (can be any sip / tel uri (including short code) of TO header),

- Destination (E.164 (<CC> <NDC>) or domain (xxx @ yyy. Cc)) to define the destination to which the media is forwarded by VPLMN)

allowing inter-operator accounting to be applied based on, eg. For example, the information to which the target network is forwarded by the user plane (according to the "Destination" parameter).

In accordance with the present invention, it is further preferred that the VPLMN P-CSCF provide the Roaming Edge Control Function (RBCF) address to the HPLMN IMS domain (eg, by a new P-RBCF header for SIP INVITE) to allow the use of RBCF from VPLMN to end the session.

As an alternative, it is further preferred that the RBCF address is preconfigured within the IMS domain of the Domestic Public Land Mobile Network (HPLMN) based on pre-shared configuration data between the VPLMN and HPLMN operator.

A further preferred embodiment of the present invention relates to the VPLMN P-CSCF and the VPLMN RBCF which provides account information that is mapped by the VPLMN billing system to support inter-operator accounting and verification of conformance to roaming between VPLMN and Domestic Domestic Land Mobile Network (HPLMN).

Additionally, it is preferred that the RBCF functionality is co-assigned with other entities, eg. eg, within an IMS P-CSCF or IMS IBGF.

In accordance with another embodiment of the present invention, the VPLMN RBCF functionality is used to serve termination calls to roaming users.

Additionally, it is preferred that the HPLMN IMS domain serving a roaming user invoke a session establishment for inbound media sessions via transit networks to the VPLMN Roaming Edge Control Function (RBCF) and provide this It provides additional information that can be used by the VPLMN Roaming Edge Control Function (RBCF) to forward the inbound media session to the VPLMN P-CSCF serving the roaming user (UE B).

Additionally, it is preferred according to the present invention that the VPLMN RBCF route the signaling for the inbound media session via the HPLMN IMS domain that forwards the signaling to the VPLMN P-CSCF where the user registers. Signaling in this way is routed through the HPLMN IMS domain which acts as a signaling anchor that can control termination services for its user. Additionally, it is preferred according to the present invention that the HPLMN IMS domain provide an HPLMN-ID and a session ID to the VPLMN Roaming Edge Control Function (RBCF) (preferably with the called party number at the establishment through any CS / PS transit network), whereby the HPLMN-ID can be used by the VPLMN RBCF to forward session establishment to the HPLMN IMS domain entities and the session ID can be used by HPLMN IMS domain entities to map inbound session set-up to Part A initial session set-up and to continue this session set-up to VPLMN P-CSCF where roaming user is registered (Part B ).

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 schematically illustrates the network architecture representing the mobile origin situation.

Figure 2 schematically illustrates a communication diagram related to the mobile origin situation.

Figure 3 schematically illustrates the network architecture representing the mobile termination situation. Figure 4 schematically illustrates a communication diagram related to the mobile termination situation.

DETAILED DESCRIPTION

The present invention will be described with respect to particular embodiments and with reference to certain drawings although the invention is not limited thereto but only by the claims. The described drawings are only schematic and are not limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustration purposes.

When an indefinite or definite article is used when referring to a singular noun, p. ex. "un", "una", "el / la", this includes a plural of that noun unless otherwise specified.

Additionally, the terms first, second, third, and the like in the description and in the claims are used to distinguish between like elements and not necessarily to describe a sequential or chronological order. It is to be understood that the terms thus used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are suitable for operation in sequences other than those described or illustrated herein.

In Figure 1, the network architecture representing the mobile origin situation is schematically shown, that is, for outgoing calls (MOC).

A Visited Terrestrial Public Mobile Network (VPLMN) access domain 11 serves the roaming user, hereinafter also referred to as User Equipment (UE A). The access domain of the Visited Public Land Mobile Network (VPLMN) comprises the S-GW, PDN-GW, a Media Gateway (MGW) A-BGF (Edge Gateway Function, that is, the Edge Gateway Function for the UE A), Call Broker Status Control Function (P-CSCF), a Visited PCRF, a Mobility Management Entity (MME), another Media Gateway (MGW) (related to the Circuit Switching domain (CS) and a SRVCC Mobile Switching Center (MSC).

The Domestic Public Land Mobile Network (HPLMN) 20 provides home services for its user (ie User Equipment (UE) A in the mobile home situation). The Domestic Public Land Mobile Network (HPLMN) comprises a domestic PCRF and an IMS domain of HPLMN or Internet Protocol Multimedia Subsystem (IMS) service domain, which comprises the Interrogation Call State Control (I-) Function CSCF), Service Call Status Control Function (S-CSCF) as well as an Internet Protocol Multimedia Subsystem Application Server (IMS) (IMS AS MMTEL).

A VPLMN Roaming Gateway domain 12 that provides access for HPLMN 20 to the use of VPLMN infrastructure for media session termination. Domain 12 Roaming Gateway of Public Land Mobile Network Visited (VPLMN) comprises Roaming Edge Control Function (RBCF) as well as ENUM / MNP function and CCF function.

A VPLMN PS / CS access domain 13 serves the remote user. The Visited Public Land Mobile Network (VPLMN) Packet Switching (PS) / Circuit Switching (CS) access domain 13 comprises a BGCF / MGCF function, an Intermediary Call State Control Function (P-CSCF ) as well as associated Media Gateways (MGW).

A VPLMN interconnect domain 14 provides interconnection to other CS / PS networks.

An arrow (in an upward direction) on Visited Terrestrial Public Mobile Network Access Network 11 (VPLMN) represents a handover of SRVCC. The upper part of the Access Network 11 of the Visited Land Mobile Mobile Network (VPLMN) corresponds to a Circuit Switching Access Network (CS) and the lower part of the VPLMN Access Network 11 corresponds to an Access Network Packet Switching (PS). The other arrows in Figure 1 correspond to the flow of session establishment messages. The broken lines correspond to the control signaling or control plane signaling and the paths through the lines correspond to the user plane or user plane route. The dashed dotted lines correspond to interfaces such as Sv, Gx, S1-MME or S9 between the network entities.

In addition to logical architecture, the inventive approach enables the integration of various logical functions within a physical entity. For example, the Roaming Edge Control Function (RBCF) may be co-assigned with other Internet Protocol Multimedia Subsystem (IMS) entities (eg P-CSCF, I / S-CSCF, IBCF or Similar).

Figure 2 schematically shows a communication diagram related to the establishment of session in the mobile home situation.

The communication diagram in Figure 2 assumes that a first User Equipment (UE A) registers in the Domestic Land Public Mobile Network (HPLMN) 20 and roams in the Visited Land Public Mobile Network (VPLMN) 10. From the first to Eighth messages 111 to 118 named in Figure 2 only refer to the mobile origin situation.

In a first stage, which involves a first message 111 "INVITE CC NDC SN", the first User Equipment (UE A) sends the session establishment message (SIP INVITE) to the Call Broker Status Control Function ( P-CSCF) of the Public Land Mobile Network Visited (VPLMN) 10. This corresponds, p. eg, to the first User Equipment (UE A) that dials any number to establish a voice call. In a second stage, which involves a second 112 "INVITE CC NDC SN" message, the session establishment message is forwarded from the Call Intermediary State Control Function (P-CSCF) of the Visited Public Land Mobile Network ( VPLMN) 10 to the Interrogation / Service Call Status Control Function (I / S-CSCF) of the Domestic Public Land Mobile Network (HPLMN) 20. In this way, the Call Intermediary Status Control Function ( P-CSCF) of the Visited Public Land Mobile Network (VPLMN) 10 may add an indication that "LBO (Local Connection) with Roaming Edge Control Function (RB-CF)" should apply. Additionally, the Call Broker Status Control Function (P-CSCF) may add an address of the Roaming Edge Control Function (RBCF). Additionally, the Call Broker Status Control Function (P-CSCF) can add a security token (to be validated later by the Roaming Edge Control Function (RBCF)). The IMS domain of the Domestic Public Land Mobile Network (HPLMN) (i.e. the Service Call Status Control Function (S-CSCF) and / or the Application Server (AS)) applies an originating service.

In a third stage and due to the origin of the call, the Domestic Public Land Mobile Network (HPLMN) Service Call Status Control Function (S-CSCF) forwards a third establishment message 113 "INVITE CC NDC SN" to the Roaming Edge Control Function (RBCF) of the VPLMN 10. It is preferred according to the present invention that in this manner, an Roaming Edge Control Function (RBCF) address (or an address provided by the P-CSCF with original INVITE setup message preconfigured or Roaming Edge Control Function (RBCF). The invitation address used in the second message 112 is replaced in the third message 113 to define the final destination that is used to route and collect the respective posting. The VPLMN RBCF applies security checks that include permission from the HPLMN to use its capabilities. Additionally, the RBCF of VPLMN applies the numerical analysis that includes database queries through p. For example, ENUM to derive the destination network, taking into account local number portability information. This is represented in Figure 2 by means of a fourth and fifth "numeric query" messages 114, 115 between the Roaming Edge Control Function (RBCF) and the ENUM / MNP function.

In a sixth step, involving a sixth message 116, the VPLMN RBCF forwards the set message "INVITE CC NDC SN" to the destination based on the result of the numerical analysis. In this way, the destination can be one of the following four cases:

- the IMS itself (from the VPLMN): the sixth message 116 is sent to the IMS domain of the VPLMN serving the called user (via I-CSCF to S-CSCF), i.e. the second User Equipment (UE B ); only this case is represented in Figure 2;

- the home network (VPLMN of) Circuit Switched (CS): the sixth message is sent by the BGCF VP ^l M ⁿ to M ^g C ^f VPLMN applying inter-operation CS network and forwards establishment to the remote party (second User Equipment (UE B));

- a previous IMS network: the sixth message is sent via IBCF from VPLMN to the IMS domain of the destination network, whereby multiple transit networks between VPLMN and the transit network can be used; - a former Circuit Switching (CS) network: the sixth message 116 is sent via BGCF to MGCF which applies interworking to CS and forwards the establishment to the destination network, whereby various transit networks can be used between the VPLMN and the transit network.

In the first case represented (destination is the IMS domain of the Visited Land Mobile Mobile Network (VPLMN) itself), by means of a seventh message 117 (in a seventh stage), the session establishment message is forwarded from the Function Interrogation Call Status Control (I-CSCF) or Service Call Status Control Function (S-CSCF) (from the Visited Public Land Mobile Network (VPLMN)) to the Intermediary Status Control Function Call (P-CSCF). In an eighth stage, involving an eighth message 118, the setup message is forwarded to the second User Equipment (UE B).

By means of a plurality of "200 OK" messages, the response from the remote side (or second User Equipment (UE B)) is sent back via RBCF from VPLMN to S-CSCF from HPLMN to P-CSCF from VPLMN to the first calling User Equipment (UE A). In this way the RBCF and P-CSCF verify the media description that includes the IP address / port to verify that the media is routed only between the access gateways of the VPLMN that serve the first part or first User Equipment. (EU A) (PDN- ^g W, IMS MGW (also called as A-BGF or A-SBC) and the VPLMN GW towards the second User Equipment (UE B), which can be a media gateway to the PS or CS access of the VPLMN itself or an interconnection media gateway to other CS or PS networks (as described above).

Session establishment continues according to the conventional IMS sequence. In this way the VPLMN RBCF and the VPLMN P-CSCF continue to verify the signaling including the media description to ensure the correct application of media routing according to the roaming agreement between VPLMN and HPLMN.

In Figure 3, the network architecture representing the mobile termination situation is schematically shown.

In the mobile termination situation, the HPLMN IMS domain establishes a media session towards a roaming user (hereinafter also referred to as the second User Equipment (UE B)) as a media session addressed by SIP signaling towards the VPLMN Roaming Edge Control (RBCF) function (telephone number or SIP Uniform Resource Identifier (URI) provided by CC NDC or VPLMN domain name). In this way, the address of the called user (or second User Equipment (UE B)) is provided by an appropriate new or existing parameter (eg, TO header or additional called party number (which would be used as a address parameter in case of a Circuit Switching (CS) interconnection This allows the use of any CS or PS interconnection network between HPLMN 20 and VPLMN 10. In case of CS interconnection, the address of the Roaming Edge Control (RBCF) function is provided by the Called Number parameter, by which the called party is indicated by any of a Called Number suffix or other parameter (eg, an additional called party) of the party ISDN User Name (ISUP) The identity of the called user (or second User Equipment (UE B)) may also be provided by indirect addressing based on a Mobile Station Roaming Number (MSRN) provided by the VPLMN to the HPLMN according to GSM procedures for termination calls.

Transit networks will have knowledge of signaling flows and associated means and can apply routing decisions and accounting decisions on SIP parameters (INVITE request line). The VPLMN Roaming Edge Control Function (RBCF) will analyze the inbound media session, modify the inbound request (eg, by establishing the called party identity within the SIP INVITE request line) and route to the P-CSCF to which the called user is registered. In accordance with the present invention, it is preferred for this routing that the VPLMN Roaming Edge Control Function (RBCF) route the session via HPLMN S-CSCF to VPLMN P-CSCF. This allows the HPLMN IMS domain better control for the termination session, since SIP signaling may have interworked with ISDN user part signaling (ISUP) with restricted signaling capabilities within inter connection.

Figure 3 represents an example for the global logical architecture for termination calls (MTC, mobile termination call). The architecture consists of:

- an HPLMN 20 comprising an IMS service domain serving the roaming user (ie the second User Equipment (UE B)) and processing the incoming call;

- an HPLMN PC / CS interconnect domain 21 that provides connectivity to / from CS / PS interconnect networks,

- one or a plurality of CS / PS interconnection networks 15,

- a VPLMN PS / CS interconnect domain 14 providing connectivity to / from CS / PS interconnect networks,

- a VPLMN roaming GW domain 12 providing access for use of the VPLMN infrastructure HPLMN for termination of media sessions towards the roaming user, and

- a VPLMN 11 PS / CS access domain serving the roaming user (ie the second User Equipment (UE B)).

An arrow (in an upward direction) on the Visited Public Land Mobile Network Access Network (VPLMN) represents a handover of SRVCC. The upper part of the Access Network 11 of the Visited Land Mobile Mobile Network (VPLMN) corresponds to a Circuit Switching Access Network (CS) and the lower part of the VPLMN Access Network 11 corresponds to an Access Network Packet Switching (PS). The other arrows in Figure 3 correspond to the flow of session establishment messages. The broken lines correspond to the control signaling or control plane signaling and the paths through the lines correspond to the user plane or user plane route. The dashed dotted lines correspond to interfaces such as Sv, Gx, S1-MME or S9 between the network entities.

In Figure 4, a communication diagram related to the mobile termination situation of session establishment is schematically shown.

The communication diagram in Figure 4 assumes that a second User Equipment (UE B) registers with the Domestic Land Public Mobile Network (HPLMN) 20 and roams the Visited Land Public Mobile Network (VPLMN) 10, i.e. the second User Equipment (UE B) registers using the VPLMN Broker Call State Control Function (P-CSCF) within its IMS domain of HPLMN. The first to thirteenth messages 131 to 143 named in Figure 4 only refer to the mobile termination situation.

In a first stage, the establishment message "INVITE B" 131 is received by the HPLMN (through a Media Gateway (MGW1)) and serves the input session for roaming user B, ie the second Team of User (UE B).

In a second stage, which involves a second and third messages 132, 133, an HPLMN Application Server (AS) is invoked to anchor the session. This means that a second session is generated from the perspective of the Service Call Status Control Function (S-CSCF) of the Domestic Public Land Mobile Network (HPLMN). The association of the two sessions is done by the Application Server (AS).

In a third stage, which involves a fourth, fifth, sixth, seventh, and eighth message 134, 135, 136, 137, 138, session establishment is performed using a plurality of messages via HPLMN's IBGF via transit GWs (Media Gateways MGW2, MGW3, MGW4, and MG ^w 5), IBGF from VPLMN to the VPLMN Roaming Edge Control Function (RBCF) with the address line <VPLMN RBCF><HPLMNID><SessionID>. Hereby the address part of <RBCF> provides <CC><NDC> to allow Transit Gateways to apply routing decisions based on the SIP layer. From the point of view of transit networks, a media session is established from the IBGF of HPLMN to the IBGF of VPLMN with an associated media path provided by the SIP SDP information. Routing and posting are based on the <RBCF> part of the INVITE request line.

The Roaming Edge Control Function (RBCF) uses the <HPLMN ID> to send a ninth signaling message 139 back to the HPLMN anchor, i.e. to the Service Call Status Control Function (S-CSCF ) of the Domestic Public Land Mobile Network (HPLMN). The IP address used to route the INVITE message is preferably derived from the <HPLMN ID>. The SIP protocol part of this IP signaling is transparent to transit networks.

The HPLMN maps, involving a tenth and eleventh message 140, 141, input INVITE B setup message 131 via <Session ID> to the current session setup (i.e. ninth message 139) and continues with session setup to the second User Equipment (UE B) by VPLMN P-CSCF (by means of a twelfth message 142 where the second User Equipment (UE B) is registered. A thirteenth message 143 corresponds to the call in the second User Equipment (EU B).

Backward messages "180 SDP-B" are used by the VPLMN Roaming Edge Control Function (RBCF) to route the media content.

Claims (7)

1. Method for providing roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a first User Equipment (UE A) is associated with a Domestic Domestic Land Mobile Network (HPLMN) and where the first User Equipment (UE A) roams in a Visited Public Land Mobile Network (VPLMN), where the Domestic Public Land Mobile Network (HPLMN) comprises a first Internet Protocol Multimedia Subsystem (IMS) domain, where the Visited Land Public Mobile Network (VPLMN) comprises a second domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Visited Land Public Mobile Network (VPLMN) comprises a Roaming Edge Control Function (RBCF), in where a session establishment of an Internet Protocol Multimedia Subsystem (IMS) session requires handling of control signaling and establishment of a user plane path, where in case of a session establishment request originating from the first roaming User Equipment (UE A) (mobile origin case) towards a second User Equipment (UE B), the second User Equipment (UE B) being connected to a target network, the method comprises the steps of: - transmitting the second Internet Protocol Multimedia Subsystem (IMS) domain a session establishment request control signaling to the first Internet Protocol Multimedia (IMS) subsystem domain, - transmitting the first Internet Protocol Multimedia subsystem domain (IMS) the session establishment request control signaling in the direct direction to the Roaming Edge Control Function (RBCF) of the second Internet Protocol Multimedia Subsystem domain Internet (IMS), and where the second Internet Protocol Multimedia Subsystem (IMS) domain is used to handle the user plane route and associated control signaling to terminate session establishment, whereby, since the local media connection shall be applied for the first roaming User Equipment (UE A), the Roaming Edge Control Function (RBCF) provides a binding of - the signaling received through a loop through the first Internet Protocol Multimedia subsystem domain (IMS) in the Domestic Public Land Mobile Network (HPLMN) - with the media anchored due to the local connection in the second domain of the Internet Protocol Multimedia Subsystem (IMS) in the Visited Terrestrial Public Mobile Network (VPLMN). 2. Method according to claim 1, wherein the Roaming Edge Control Function (RBCF) applies an offline charging functionality. 3. Method according to claim 1, wherein the Roaming Edge Control Function (RBCF) applies numerical analysis and portability functionalities to support additional session establishment. 4. Method for providing roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a second User Equipment (UE B) is associated with a Domestic Domestic Land Mobile Network (HPLMN) and where the second User Equipment (UE B) roams a Visited Land Public Mobile Network (VPLMN), where the Domestic Land Public Mobile Network (HPLMN) comprises a third domain of the Internet Protocol Multimedia Subsystem (IMS), where the Visited Land Public Mobile Network (VPLMN) comprises a fourth domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Visited Land Public Mobile Network (VPLMN) comprises a Roaming Edge Control Function (RBCF), in where a session establishment of an Internet Protocol Multimedia Subsystem (IMS) session requires handling of control signaling and establishment of a user plane route, where in the event of a session establishment request ending in the second roaming User Equipment (UE B) (mobile termination case) of a first User Equipment (UE A), the first User Equipment (UE A) being connected ) to a source network, the method comprises the steps of: - transmit the third domain of the Internet Protocol Multimedia Subsystem (IMS) a session establishment request control signaling to the Roaming Edge Control Function (RBCF) of the Visited Terrestrial Public Mobile Network (VPLMN) that allows establish the media path to the VPLMN, - transmit the Roaming Edge Control Function (RBCF) the session establishment request control signaling to the third domain of the Internet Protocol Multimedia Subsystem (IMS), and where The fourth Internet Protocol Multimedia Subsystem (IMS) domain is used to handle the user plane route and associated control signaling to terminate session establishment, whereby, since the local media connection shall be applied For the second roaming User Equipment (UE B), the Roaming Edge Control Function (RBCF) provides a binding of - the signaling received from the third domain of the Internet Protocol Multimedia Subsystem (IMS) in the Domestic Public Land Mobile Network (HPLMN) - with the media sent to the fourth Internet Protocol Multimedia Subsystem (IMS) domain, where the media of the second User Equipment (UE B) are anchored due to the local connection. The method according to claim 4, wherein the Roaming Edge Control Function (RBCF) receives a session establishment request by an Interconnection Edge Gateway Function (IBGF), this session establishment request being routed through the minus one transfer entity. 6. The Visited Terrestrial Public Mobile Network (VPLMN) to provide roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a first User Equipment (UE A) is associated with a Public Mobile Network Domestic Terrestrial Network (HPLMN) and where the first User Equipment (UE A) roams the Visited Terrestrial Public Mobile Network (VPLMN), where the Domestic Domestic Terrestrial Mobile Network (HPLMN) comprises a first domain of Protocol Multimedia Subsystem Internet (IMS), where the Visited Terrestrial Public Mobile Network (VPLMN) comprises a second domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Visited Terrestrial Public Mobile Network (VPLMN) comprises a Control Function of Roaming Edge (RBCF), where a session establishment of an Internet Protocol Multimedia Subsystem (IMS) session requires the handling of control signaling and the establishment of u na user plane route, where in case of a session establishment request originating from the first roaming User Equipment (UE A) (mobile origin case) towards a second User Equipment (UE B), being The second User Equipment (UE B) is connected to a target network, where the Visited Land Public Mobile Network (VPLMN) is configured to: - transmitting a session establishment request control signaling from the second Internet Protocol Multimedia Subsystem (IMS) domain to the first Internet Protocol Multimedia Subsystem (IMS) domain, - transmitting a session establishment request control signaling from the first Internet Protocol Multimedia subsystem domain (IMS) direct to the Roaming Edge Control Function (RBCF) of the second Multimedia Subsystem domain of Internet Protocol (IMS), and where the second Internet Protocol Multimedia Subsystem (IMS) domain is used to handle the user plane route and associated control signaling to terminate session establishment, whereby, Since the local media connection shall be applied for the first roaming User Equipment (UE A), the Roaming Edge Control Function (RBCF) provides a binding of - the signaling received through a loop through the first Internet Protocol Multimedia subsystem domain (IMS) in the Domestic Public Land Mobile Network (HPLMN) - with the media anchored due to the local connection in the second domain of the Internet Protocol Multimedia Subsystem (IMS) in the Visited Terrestrial Public Mobile Network (VPLMN). 7. The Visited Terrestrial Public Mobile Network (VPLMN) to provide roaming functionality related to an Internet Protocol Multimedia Subsystem (IMS) session, where a second User Equipment (UE B) is associated with a Public Mobile Network Domestic Terrestrial Network (HPLMN) and where the second User Equipment (UE B) roams in the Visited Land Public Mobile Network (VPLMN), where the Domestic Domestic Terrestrial Mobile Network (HPLMN) comprises a third domain of the protocol's multimedia Subsystem Internet (IMS), where the Visited Land Mobile Mobile Network (VPLMN) comprises a fourth domain of the Internet Protocol Multimedia Subsystem (IMS), and where the Visited Land Mobile Mobile Network (VPLMN) comprises a Control Function of Roaming Edge (RBCF), where a session establishment of an Internet Protocol Multimedia Subsystem (IMS) session requires the handling of control signaling and the establishment of a user plane route, where in case of a session establishment request ending in the second roaming User Equipment (UE B) (mobile termination case) of a first User Equipment (UE A), being connected the first User Equipment (UE A) to a source network, the Visited Land Public Mobile Network (VPLMN) is configured to: - the transmission of a signaling to control the session establishment request of the third domain of the Internet Protocol Multimedia Subsystem (IMS) to the Roaming Edge Control Function (RBCF) of the Visited Public Land Mobile Network (VPLMN) which allows to set the media path to the VPLMN, - the transmission of the session establishment request control signaling of the Roaming Edge Control Function (RBCF) to the third domain of the Internet Protocol Multimedia Subsystem (IMS), and wherein the fourth Internet Protocol Multimedia Subsystem (IMS) domain is used to handle the user plane path and associated control signaling to terminate session establishment, whereby, since the local media connection To be applied for the second roaming User Equipment (UE B), the Roaming Edge Control Function (RBCF) provides a binding of - the signaling received from the third domain of the Internet Protocol Multimedia Subsystem (IMS) in the Domestic Public Land Mobile Network (HPLMN) - with the means sent to the fourth domain of the Internet Protocol Multimedia Subsystem (IMS), where the means of the second User Equipment (UE B) are anchored due to the local connection.