WO2010112759A1

WO2010112759A1 - Method of updating an application session in progress for a user terminal of a telecommunications network

Info

Publication number: WO2010112759A1
Application number: PCT/FR2010/050590
Authority: WO
Inventors: Sandrine Lataste
Original assignee: France Telecom
Priority date: 2009-03-31
Filing date: 2010-03-30
Publication date: 2010-10-07

Abstract

The invention relates to a method of updating an application session in progress for a user terminal of a telecommunications network comprising an application system able to manage said session, said user terminal accessing the telecommunications network by way of an access network, said method comprising a step (E1) of receiving a notification of change related to access of said user terminal from an access gateway to the telecommunications network. According to the invention, the method comprises, on receipt of said notification, a step of triggering (E4) an action for updating the application session in the application system.

Description

Method for updating a current application session for a user terminal of a telecommunications network Field of the invention

The field of the invention is that of telecommunications, and more particularly telecommunications networks comprising an application system conforming to the IMS (IP Multimedia Subsystem) architecture as defined by the 3GPP (Third Generation Partnership Project).

The present invention relates to the management and, in particular, the updating of an application session involving a user terminal of the telecommunications network, when this user terminal, in a situation of mobility, changes its type or technology. access to the telecommunications network.

The 3GPP standard defines in its release 8, an advanced network architecture called SAE (Service Architecture Evolution, in English) or EPS (Evolved Packet System, in English) including a core EPC network (Evolved Packet Core, in English). . This new architecture provides, in particular in the specifications 3GPP TS 23.401 and 23.402, that a user terminal can access the telecommunications network of the operator via 3GPP or non-3GPP type access.

It also provides for the user terminal to change access technology within the same access network or access type, while maintaining access to the service via the same access gateway (gateway or gateway). GW, in English) to the telecommunications network, the network access gateway being informed of this change by a different message depending on the mobility performed by the user terminal. For example, it is a "Create Bearer Request" GTP message with a "Attach Type" parameter set to "Handover" for mobility to 3GPP access where the EPS network uses the GPRS (GPRS) Tuning Protocol. in English). It may also be a Proxy Binding Update (Proxy Mobile Internet Protocol) (PMIP) message for mobility to 3GPP or non-3GPP access in which the EPS network uses the PMIPvβ protocol. For example, the user terminal changes access technology without changing the type of access, when it passes from a UMTS Terrestrial Radio Access Network (UTRAN) technology to E-UTRAN (Evolved). UTRAN) in a type of 3G mobile access. All handover procedures contain a step of reporting information to the application domain when a PCC (Policy Control & Charging) architecture is put in place.

The standard stipulates, in document TS 23.203, that events are reported from the access gateway to a PCRF entity (Policy and Charging RuIe Function) in charge of policing QoS and / or billing. an application session.

When a Policy Control & Charging (PCC) architecture is used, the standard provides for events to be escalated from the GW gateway to a Policy and Charging RuIe Function (PCRF) entity that is responsible for managing the billing of the current application session. Some events are reported systematically, this is the case of the modification of resources that is reported to the PCRF with the procedure "PCEF-initiated IP-CAN Session Modification". Other events, including changes related to user terminal access to the network, are only reported to the PCRF if it has previously subscribed to an event notification mechanism.

The PCC architecture, as defined in document TS 23.203, notably comprises the PCRF function that has just been mentioned, as well as an application function (AF). The application function, AF is defined as an element of the application system offering dynamic quality of service (QoS) control and / or billing based on information from the media plan. It can be implemented by an application entity that serves as a point of entry to the terminal in the packet network, such as a P-CSCF entity (Proxy CaII Session Control Function, in English) when the application subsystem is IMS type. It will be noted that the AF application function as described in the 3GPP standard can also be implemented by a server application (AS or Application Server, in English) responsible for implementing the execution of an application service requested by the user terminal, in the case of an IMS architecture.

In a detailed manner, the 3GPP TS 29.212 specification provides that the access gateway informs the PCRF entity in case of occurrence of particular events such as the change of access type "IP-CAN_CHANGE" or the change of technology of 'RAT_CHANGE' access, using a Diameter command message

CCR (Credit Control Request, in English).

If the access type is changed ("IP-CAN-CHANGE" event), the Diameter CCR command message contains the parameter "IP-CAN-Type" and / or the additional parameter "RAT-Type" when is applicable. Indeed, this last parameter only makes sense for 3GPP, 3GPP2 or EPS mobile access.

In case of access technology change (event "RAT_CHANGE"), the query Diameter CCR contains only the parameter "RAT-Type". This user terminal access change information can be transmitted from the access gateway GW to the PCRF entity during the restoration of the IP-CAN session, in particular during the activation of the transmission link in the media plan, and during an IP-CAN session modification in the event of a change of access type notified by the access gateway to the PCRF entity. The TS 29.214 standard provides that I ¹ AF subscribes to the PCRF entity, using an AAR type Diameter (Authorization, Accounting Request) message, to the notification of events relating to the allocation. "Bearer Level Events", among which is a change of access of the user terminal. When such an event occurs, the PCRF entity contacts the AF via a RAR (Re-Auth-Request) type Diameter message including the new value (s) of the "IP-CAN Type" parameter (s), and "RAT- Type "related to user terminal access, where applicable.

According to TS 29.214, the subscription is valid until the end of the user's IMS registration. The AF replaces the values of the parameters relating to the access of the user terminal ("IP-CAN Type" and / or "RAT-Type") that he had stored locally during IMS registration by the new values received in the event notification.

Disadvantages of the Prior Art When registering a user terminal in the IMS, I ¹ AF (P-CSCF) receives a SIP REGISTER request from that terminal which may contain an indication of access type in the "P-Access-Network-Info" (PANI) header as defined in TS 24.229. Moreover, because of its subscription prior to the event notification relating to the access of the user terminal to the network to the PCRF entity, I ¹ AF (P-CSCF) is notified of this change for the terminal of the user, via the media plane via the packet network access gateway of the telecommunications network, in the form of a message comprising the new IP-CAN-Type access type values and RAT access technology -Type, if applicable. The TS 24.229 standard additionally provides, optionally, that I ¹ AF (P-CSCF) adds a PANI header with the values of these parameters and an indication that these values are certified ("network-provided") in the request for registration of the user, before transmitting it to the other application entities of the network.

In case of a change related to the access of the user terminal during the application session, the user terminal does not necessarily issue a signaling request to the network. Indeed, it emits a signaling request only if it wishes, on the occasion of change of access, to request a modification of the application session, such as for example a modification relating to the bandwidth or the codec used. As a result, the values of these parameters relating to the access of the user terminal to the network remain unchanged in the application system, while they are up to date in the media plane. It is understood that this situation induces an inconsistency between the application session and the session at the media level. Such inconsistency can have adverse consequences on the processing of the current session for this user, for example as regards the billing of his calls. Indeed, it can cause a conflict between the transport level tickets that are set updated in the transport plan and IMS level tickets that are not updated, which can lead to the development of an erroneous bill for the user.

DISCLOSURE OF THE INVENTION The invention makes it possible to solve the disadvantages of the prior art by using a method for updating an application session in progress for a user terminal of a telecommunications network. comprising an application system adapted to manage said session, said user terminal accessing the telecommunications network via an access network, said method comprising a step of receiving a change notification related to the access said user terminal from a network access gateway.

According to the invention, said method, implemented by an application entity of the application system, comprises, on receiving said notification, a step of triggering an update action of the application session in the application system.

Thus, the invention makes it possible to systematically take into account the information relating to the access of a user terminal to the telecommunications network, transmitted by the media plan to the application system in charge of managing the resources and the implementation of the services offered to the user. In particular, it allows this information to be taken into account for the management of the application session or sessions in progress for the user. According to the invention, the information obtained is reliable and reliable because it is derived from the media plan. This information is conveyed via the telecommunications network access gateway responsible for routing the media flows of the user terminal, then via the PCCF entity PCC architecture, to the application entity in charge of implement the method according to the invention.

According to one aspect of the invention, the update action of the application session comprises at least sending an action command message to at least one other entity of the application system. Such a control message is advantageously a message of signaling according to the SIP protocol.

In the case of an application system architecture of the IMS type, the updating method according to the invention is advantageously implemented in an entity of type AF. As mentioned above, it may be the P-CSCF or the application server (Application Server or AS) in charge of the execution of the service requested by the user.

An advantage of the P-CSCF entity is that it is the first entity of the application system seen by the user terminal, so it is most likely to relay the information received from the transport plan throughout the application system. An advantage of I ¹ AS is that it has all the information relating to the execution of the service or services requested by the user and that it can interact with other application servers for the realization of these services. It can thus adapt other characteristics of the session, such as the codings used for the encoding and the decoding of the media flows or the required bandwidth to the new values of the parameters related to the access of the user.

In particular, the standard makes it possible to require the AS to add a certified PANI header in a signaling request for the current session, while this operation remains optional for the P-CSCF. An advantage is that the AS can possibly interact with other application servers based on the value of the PANI which can thus become a service trigger parameter defined in the profile of the IMS subscriber.

Another advantage is that it allows the operator to control the consideration of the change related to the access for the execution of the service, in particular as regards billing.

According to another aspect of the invention, prior to sending the command message, the step of triggering an update action comprises:

- activation of a timer;

at the end of said delay, the verification that no update message of the application session including said indication of change related to the access has been received from the user terminal.

Thus, the action of updating the session is actually implemented only if necessary. Indeed, when the user terminal informs the application system of a change related to its access to the network by way of a signaling request, this change information is systematically taken into account by the application entities placed on the signaling path and no further action is necessary.

An advantage of this embodiment of the invention is to allow the user terminal time to perform itself the update of its application session. In fact, the terminal can update its application session in accordance with the IETF SIP standard defined in RFC 3261. To do this, it sends a request of the type SIP rec INVITE or UPDATE including the parameters of the current session that it wishes. edit. It can for example, add / delete one or more media or change source / destination IP address. However, the 3GPP standard does not require the terminal to perform a session update (SIP re-INVITE or UPDATE) nor a session transfer (SIP INVITE with a session transfer indication) following a change of type. in accordance with 3GPPTS 23.237.

Alternatively, prior to the activation of the timer, the method according to the invention comprises a step of notifying the user terminal comprising said indication of change related to the access. This is for example a message type SIP NOTIFY or SIP MESSAGE or any other message, for example a message type SMS or type OMA-DM (device management defined in standardization OMA, Open Mobile Alliance) for the prompting to update its application session itself (SIP re-INVITE or UPDATE) or to perform a session transfer (SIP INVITE with a session transfer indication).

According to another variant, the timer could be placed at the level of the PCRF entity instead of I ¹ AF, the notification of change related to the access of the user having then returned to the AF after expiration of the timer, if the PCRF has not received from the AF an indication of application session update from the terminal. In the case of the management of the continuity of service by an application server of the SCC AS type, this notification can be advantageously made with an OMA-DM type message imposing the session transfer to the new access detected following the handover since an interface of this type is already supported between the terminal and the SCC AS for the transfer of the operator's policy on session transfer.

According to this embodiment of the invention, if the terminal has not sent a signaling request to the network following its access change, the sending of the update control message is triggered.

According to another aspect of the invention, the control message is a log off message. The absence of signaling from the terminal is then considered as an error case to be remedied. A SIP BYE type of signaling message is sent to the user terminal on the one hand and on the other hand to the called terminal via the other application entities to terminate the application session.

According to another aspect of the invention, the control message is a session update message including the change indication related to the access of said user terminal. Such a message may advantageously be a SIP UPDATE or SIP re-INVITE message in which the values of the "access-class" and / or "access-type" fields of Pen-head SIP PANI carrying the updated values of the access technology and / or access type actually used by the user terminal. Alternatively, it may be a session transfer message (SIP INVITE indicating a session transfer). This update message is sent to the user terminal on the one hand and on the other hand to the called terminal via the application entities placed on the signaling path of the call and includes the values of the parameters to be updated. An AF can operate in two main modes: the proxy mode, in which it relays a signaling request. This is the only possible mode for the P-CSCF entity; - the BackTo Back User Agent (B2BUA) mode, in which it acts as a cutoff point between the calling terminal and the called terminal, creating a half-call between the caller and him and a half-call between him and the called. Note that, according to this embodiment of the invention, I ¹ AF responsible for implementing the process of updating the session must necessarily, to be able to intervene in the application session, act in B2BUA mode. Indeed, only this mode allows him to issue his own request to update the application session.

According to the 3GPP standard, the AF function can act in this mode if it is implemented by an application server AS. Advantageously, the update action of the application session is performed by an application server dedicated to the session transfer processing, for example the SCC AS ("Service Centralization and Continuity Application Server" in English) in charge continuity of service in the event of user mobility.

Advantageously, according to the invention, the "access-class" field is extended to non-3GPP type accesses, for example type I-WLAN or xDSL to specify the access technology used.

Advantageously, the method comprises, prior to issuing the update message, a data consultation step representative of the new access of the user terminal and a step of adapting session parameters according to the data consulted. These may be, for example, characteristic parameters of the new transmission link between the user terminal and the network, such as the codec to be used to encode the media data or the necessity of involving a transcoding function. According to another aspect of the invention, the update message is a request for updating billing tickets intended for an entity in charge of billing. This is advantageously a SIP Accounting Request type message. Upon receipt of this message, the billing entity will update the billing tickets to correspond to the billing rules provided by the operator for the access actually used by the user terminal. As a variant, the update message is a billing ticket closing request for the old access followed by another update message consisting of the opening of a billing ticket for the new access, destined for a new billing ticket. entity in charge of billing. According to another aspect of the invention, the update message is an event notification message relating to a change related to the access of said user terminal, intended for application entities having previously subscribed to said notification.

A first advantage is that, upon receipt of this message, the application entities may in particular issue an update message of update type IMS tickets with the entity in charge of billing. As a variant, they will issue an IMS ticket closure message for the old access and then an IMS ticket opening message for the new access.

A second advantage is to inform all the application entities involved in the current session to encourage them to update the session at their level. In particular, the event notification message relating to access encourages them to update their respective billing tickets and thus makes it possible to avoid inconsistencies between the billing tickets issued by the different application entities in charge of the management. the current application session.

Alternatively, the entity in charge of billing may close the billing tickets used for the old access and issue new ones corresponding to the new access.

The invention also relates to a device for adapting an application session in progress for a user terminal of a telecommunications network comprising an application system capable of managing said session, said device comprising a step of receiving a notification. a change relating to the access of said user terminal from a network access gateway, said device being characterized in that it comprises, on receipt of said notification, means for triggering a update action of the application session in the application system.

The invention also relates to an entity for managing an application session between a user terminal and a telecommunications network, characterized in that it comprises a device for adapting the session in progress according to the invention. In a particular embodiment, the various steps of the method of adaptation of an application session in progress according to the invention are determined by instructions of computer programs.

Accordingly, the invention also relates to a computer program on an information carrier, this program being capable of being implemented in a routing device, receiving or transmission or more generally in a computer, this program comprising instructions adapted to the implementation of the steps of a process for updating an application session as described above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.

The invention also relates to a computer-readable information medium, comprising instructions of a computer program as mentioned above. The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard. On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can be downloaded in particular on an Internet type network. Alternatively, the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

List of Figures

Other advantages and characteristics of the invention will emerge more clearly on reading the following description of a particular embodiment of the invention, given as a simple illustrative and nonlimiting example, and the appended drawings, among which: FIG. 1 schematically shows a telecommunications network comprising an application system capable of managing the application sessions of a user terminal according to the invention; FIG. 2 schematically shows the steps of the method for updating an application session in progress according to the invention; FIG. 3 schematically shows the structure of a device for updating an application session according to the invention; and FIG. 4 schematically shows a diagram of the signaling flows exchanged in the application system in a first example of implementation of the invention; FIG. 5 schematically shows a diagram of the signaling flows exchanged in the application system in a second exemplary implementation of the invention; and FIG. 6 schematically shows a diagram of the signaling flows exchanged in the application system in a third exemplary implementation of the invention.

DESCRIPTION OF A PARTICULAR EMBODIMENT OF THE INVENTION The general principle of the invention is based on systematic consideration a notification of a change related to the access of a user terminal of a telecommunications network, issued by the media plane, in the management of the application sessions in which the user terminal is involved.

FIG. 1 shows an example of a telecommunications network of the invention. The telecommunications network 1 comprises access networks AN1, AN2, AN3, at least one packet core network 2 and an application system 10, based for example on an IMS type architecture and able to implement and manage application sessions. for the execution of services.

An UE1 (User Equipment) terminal of a user who has subscribed to a subscription with the network operator 1 is considered to access at least one service deployed on this network. It is assumed that the user terminal UE1 has in particular subscribed to a mobility service which allows it to access the network via several access networks AN1, AN2 and to change the access network during the service. an application session, without interruption of it. These access networks can also be of fixed type, for example according to the ADSL (Asynchronous Digital Subscriber One) technology or of the mobile type. Among the mobile networks, 3GPP-type mobile access networks will be distinguished in the following, using technologies such as, for example, UTRAN, e-UTRAN, GERAN and non-3GPP mobile access networks such as WiFi access networks. as defined by IEEE 802.11 or WIMAX.

When it is based on an IMS-type architecture, the application system 10 notably comprises the following application entities:

the P-CSCF entities (Proxy-Call State Control Function), which are the first points of contact or entry points in the IMS domain of the network 1 for the user terminals such as the terminal UE1;

the S-CSCF entities (Serving CaII State Control Function), which control the application sessions of an UE1 terminal during the entire period when the latter is registered in the IMS domain; the S-CSCFs have an interface with a Home Subscriber Server (HSS), including the IMS subscriber database; at least one application server (Application Server) in charge of executing the services requested by the user terminals. An application server is usually dedicated to implementing a particular service. For example, the SCC AS application server ("Service Centralization and Continuity Application Server") is responsible for service continuity in the event of user mobility; and

a PCRF (Policy and Charging Rules Function) entity in charge of controlling the quality of service and billing of the services used by the user terminal. Such an entity is part of a PCC architecture (Policy Control & Charging) specified by the 3GPP standard.

Advantageously, the protocol used to control IP Multimedia sessions is the Session Initiation Protocol (SIP). This protocol is used by the terminal equipments 10, the CSCF entities and the application servers connected to the S-CSCFs. To establish a session in the IMS domain, a terminal device uses the SIP protocol.

When he wishes to use an application service of the telecommunications network 1, the user terminal UE1 first connects to an access network 20.

Then the UE1 terminal registers in the IMS domain after discovery of an access point, its P-CSCF. It accesses I ¹ IMS via a gateway GW 1 connected to the P-CSCF.

Once the UE1 terminal is registered in the IMS domain, it can initiate a media session with another user or with a server.

To do this, the terminal equipment sends an INVITE message defined for the SIP protocol to the P-CSCF, this message being transmitted to the S-CSCF to then reach the destination network.

In this INVITE message, the terminal equipment describes the characteristics of the session, including the type of media (video, audio), the supported codec (s), the quality of service characteristics required for the session. application, including the debit information, ... that he wishes to use for a given service. When establishing the call on the IMS network, the P-CSCF entity in charge of managing the session of the user terminal UE1 sends a request to a PCRF resource control entity to communicate information about the session. This information is used by the PCRF to later make a QOS QoS and billing decision when activating resources for the session. The P-CSCF entity behaves from this point of view as an Application Function (AF), also called "Applicative Entity".

Upon receipt of this request, the PCRF identifies the transmission links impacted by the application session and defines a set of Policy Control and / or Charging Rules (PCC).

The resource control entity uses the service information received in the request to calculate the maximum quality of service (QoS Max) allowed for each of the media streams of the session.

The 3GPP standard specifies that the endpoint in the transport plan, ie the GW1 gateway behind which the terminal accesses the IMS network (the GGSN entity, Gateway GPRS Support Node in a UMTS network, the PDG entity, Packet Data Gateway in an I-WLAN) selects, during resource activation, the PCRF contacted by the AF application entity at the time of establishment of the session to obtain the PCC rules for the media streams. The gateway behaves from this point of view as an Implementation Function of the Policy and Charging Enforcement Function (PCEF).

In connection with FIG. 1, it is now assumed that the user terminal UE1 has a current application session S1 using the network 1. By way of example, it has established a VoIP communication with a user terminal UE2. which accesses the network 1 via an access network AN3. For simplicity, the application entities such as, for example, the P-CSCFs, S-CSCFs and ASs in charge of managing the called user terminal U2 are not represented in FIG.

During the communication, it is assumed that the user terminal UE1 moves and changes access network. For example, it passes the access network AN1 mobile type UTRAN or more generally 3GPP mobile AN2 network type I-WLAN or more generally not 3GPP.

It has been seen that the 3GPP standard specifies a procedure for raising information relating to the access of the user terminal UE1 by the access gateway GW1 to the application subsystem 10 via the control entity PCRF. Specifically, this access information is received by an application entity AF, which may be the P-CSCF which has previously subscribed to a user-related event notification mechanism as specified in TS 29.214 .

It should be noted in this regard that according to the current standard, the access gateway GW1, which remains the same regardless of the access network used by the user terminal, is not required to trace the change information. only when it is associated with a change in access type. In other words, when the user terminal changes mobile access technology, for example from UTRAN access technology to E-UTRAN technology, no notification is issued by the access gateway to I ¹ AF. As a result, the AF does not have at the application level complete information relating to the access of the user terminal.

According to the invention, the access gateway more generally relates to any information relating to a change of access of the user terminal, whether it concerns the type of access or the access technology used.

The invention relates in particular to a method of updating the current application session, which will now be presented in relation with FIG. 2. It is assumed that an event notification AE relating to the access of the terminal of user UE1 is received in a step E1. Upon receipt of this notification AE, an update control action of the current application session S1 is triggered in a step E4.

Advantageously, the update method according to the invention comprises a prior step E2 for activating a timer. At the end of this delay, a verification step E3 is implemented. It consists in verifying that no update message of the application session comprising said indication of change related to the access has been received from the user terminal UE1.

If the verification step E3 highlights the absence of receipt of an update message from the user by the application system 10 of the network 1, then the step E4 of triggering a data protection action. session update command S1 is implemented.

It is understood that when it could be verified that a session update message of the type re-l NVITE or UPDATE was sent by the user terminal following a change related to its access to the network 1, by example to request an adaptation of parameters related to the current session (coded, bandwidth, for example) to the new access, it is not necessary to trigger an adaptation action of the session by the application system. Indeed, such a re-INVITE message comprises in this case an indication of access type or updated access technology.

It is admitted here that such an indication is carried in a "P-Access-Network-Info" (PANI) header as defined in document TS 24.229 which provides that the terminal inserts this header if available and leaves the possibility for the P-CSCF to add one and insert the values sent from the access gateway and a "network-provided" indication. In reality, this point is questionable since the addition of the PANI by the P-CSCF is not mandatory because of its role of SIP proxy, this argues for an implementation of the invention in I ¹ AS rather than in the P-CSCF.

According to one embodiment of the invention, the method for updating an application session is implemented in an update device 110, 310 of an application session, which will now be described in connection with the FIG. 3. It comprises the material elements conventionally found in a conventional computer or a specialized router, namely a processor 11, a RAM type RAM 12, a ROM type ROM 13 and telecommunications means 14. with the network 1.

According to the invention, the device 110, 310 comprises a memory 15 which constitutes a recording medium according to the invention. This medium stores the computer program according to the invention. This program includes instructions for performing the steps of the method of updating an application session according to the invention which has just been described with reference to FIG.

Advantageously, the device for updating an application session according to the invention is implemented in an application entity of the AF type of the application system 10 of the network 1. It is recalled that the application function AF can also be implemented by an application entity of the P-CSCF type only by an application server such as the application server AS in charge of executing the service requested by the user terminal UE1. In this second case, the invention imposes the implementation of an additional interface between the PCRF and I ¹ AS in accordance with the PCC architecture, advantageously of the Rx type for message exchanges according to a DIAMETER type protocol.

An example embodiment of a first embodiment of the invention will now be described with reference to FIG. 4. The situation described above relates to FIG. 1, according to which the user terminal UE1 has changed access type by passing from the AN1 access network to the AN2 access network.

It is assumed that in a prior step the application entity AF has subscribed to the PCRF entity 400 to the event notification mechanism linked to an access change of the user terminal UE1. Such a subscription consists in the delivery of a Diameter AAR request issued from the AF to the PCRF for the terminal in question and sending a Diameter AAA response associated with the PCRF.

It is recalled that this mechanism of subscription / notification of the FA to the

PCRF is specified at 3GPP and made mandatory in document 29.214, during user registration in I ¹ IMS when the AF function is implemented by a P-CSCF type entity 110. According to the invention, this mechanism is extended in case the AF function is implemented by the AS 310 application server.

It is also assumed that the other application entities of the application system

10 in charge of the management of the current session have previously subscribed to the AF 110, 310 to an event notification mechanism (SIP Event Package) in the application plan. Such a mechanism is specified by I ¹ IETF in RFC 3265. It allows an application entity in charge of an application session involving the EU1 terminal, ask to be informed systematically by a type of SIP NOTIFY signaling message an event relating to a user of the application system 10. According to the invention, a new type of event, which could for example be designated by "Access Change Event", is advantageously defined for the application of the notification mechanism. of changes related to user terminal access to the network.

The terminal is now considered to change access network or access technology. The following steps are then implemented:

Step 1: The network access gateway GW1 (IP can bearer signaling) receives a message indicating a modification of the access resources including a handover, for example a GTP "Update Bearer Request" message. a request "Attach Request" issued by the terminal, both containing a parameter "Attach Type" to the value "Handover";

Step 2: upon receipt of this message, the gateway GW1 notifies the PCRF control entity 400 of the PCC architecture, of a change linked to the access of the terminal UE1 via a Diameter CCR type message (Credit Control Request). In the example of FIG. 1, this is a new value of a parameter representative of the type of access used by the terminal UE1, for example of the IP CAN type parameter. It will be noted that this could be a new value of a parameter relating to the access technology used by the terminal UE1, for example E-UTRAN instead of UTRAN. Step 3: The PCRF entity stores in memory the information related to the change of access of the terminal UE1 provided by the transport plane. Step 4: The PCRF entity establishes a binding (in English) between a media session identifier corresponding to the information received and stored with the current application sessions managed by the application subsystem 10. It can thus identify the AF 110, 310 concerned by the information received. Step 5: The PCRF entity sends a DIAMETER RAR message (Re-Auth-Request) to the identified I ¹ AF, such a message including information concerning a change related to the UE1 user terminal access.

Step 6: II receives a DIAMETER RAA response (Re-Auth-Answer) from I ¹ AF 110, 310.

Step 7: Upon receipt of the DIAMETER RAR message from the PCRF, I ¹ AF 110, 310 forward this message as a CCA DIAMETER CCA (Credit Control Answer) message to the GW.

Step 8: L ¹ AF stores (8a) the received information and detects (8b) that it relates to a change related to the access of the user terminal UE1.

Step 9: The AF entity issues an adaptation command of the current session to a Charging Data Function (CDF) entity in charge of billing.

Advantageously, such an update command can take the form of a message of the type Accounting Request comprising the new values of the parameter or parameters related to the access.

Step 10: Upon receipt of this message, the CDF billing entity updates the billing tickets for the application session for the AF.

Step 11: The CDF billing entity acknowledges receipt of the Accounting Request message.

Step 12: The AF entity 110, 310 notifies the change related to the access of the UE user terminal 10 of the application entities of the application subsystem 10 which have previously subscribed to it. It sends them to do this a SIP NOTIFY type message including the change information related to the access of the user terminal. Note that in case the AF function is implemented by the P-

CSCF 110, the application server AS 310 in charge of the execution of the service can then be part of the application entities notified by I ¹ AF P-CSCF 110.

Step 13: The AF entity 110, 310 receives back acknowledgments from the application entities concerned. Step 14: The IMS application entities detect the change related to the notified access in the SIP NOTIFY message.

Step 15: They each issue a request to update their respective billing tickets with the CDF in the form of an Accounting Request type message including the new values of the parameter or parameters related to the access.

Step 16: The CDF entity takes their requests into account, updates the corresponding billing tickets, and acknowledges receipt of the Accounting Request messages.

In this embodiment of the invention, it is therefore mandatory for the operator to trigger the update of the billing tickets of the IMS domain by the application entities concerned, with the new parameter values related to the access of the user. User terminal UE1 at I ¹ AF on notification of a change related to the access received via the PCC architecture. These entities then automatically trigger the update of their IMS billing ticket in case of a change in the value of a parameter linked to the access of type "IP-CAN Type" and / or "RAT-Type".

According to one variant, the application entities concerned do not request an update of their billing tickets, but a closure of their old tickets followed by the opening of new tickets.

According to this embodiment of the invention, the other IMS entities (none, all or only part depending on the operator's choice) must subscribe to the change event related to the access of the user terminal to I ¹ AF. For this purpose, a new event is advantageously created. According to one variant, an existing event is extended.

An example of setting of a second embodiment of the invention will now be described in relation to FIG. 5. It is placed in the situation described above in relation to FIG. 1, according to which the terminal user UE1 has changed access type from the AN1 access network to the AN2 access network.

Steps 1 to 8 of the diagram of Figure 6 are identical to those of Figure 5 and will not be described again. Steps 9 and 10: I ¹ AF 110, 310 triggers an update of the application session S1 by sending at least one SIP UPDATE or RE-INVLTE session update message including the one or more news. values of the parameters representative of the access of the user terminal UE1. Advantageously, they are transported in the PANI header of this message. Alternatively, an SIP INVITE message dedicated to session transfer could be used. Such a message is specified in TS 23.237 regarding the management of continuity of service in I ¹ IMS ,.

It will be noted, with reference to FIG. 5, that two signaling messages are sent, a message for the "call Ieg1" to the user terminal UE1 and a message for the "call Ieg2" to the application entities situated further upstream. on the signaling path in the application subsystem 10. It is considered here that the signaling path between the user terminal UE1 and the application subsystem

10 can be divided into two branches (legacies in English), each of which is subject to specific treatment. This corresponds to a particular action mode of the AF entity, known as the B2B Back-Back User Agent (UA) mode, in which I ¹ AF acts as a cutoff point between the two by creating a half-call between the caller and the FA and a half-call between the FA and the called party.

In the PCC architecture, the P-CSCF entity 110 is an example of AF, as mentioned in 3GPP TS 23.203. It should be noted, however, that according to the 3GPP standard, the role of B2BUA is not recommended for P-CSCF 110 which is identified as a SIP proxy in the current standard. Indeed, to make it operate in B2BUA mode would require to undergo significant structural changes.

On the other hand, an AS application server can act in B2BUA mode in the IMS application subsystem 10, as described in the document TS 24.229. In particular, the SCC AS application server, in charge of managing the continuity of service in I ¹ IMS already intervenes in B2BUA to manage the mobility of the user.

Steps 11, 12: the application entities of the two branches call Ieg1 and call leg 2 acknowledge receipt of the update message of the session.

Step 13: The application entities of the second leg 2 branch having received the update message trigger sending an update request Accounting

Requesting their billing ticket from the CDR entity.

Step 14: The CDR entity takes into account the received billing update requests.

Step 15: The CDR entity acknowledges receipt of billing update requests.

Step 16 (respectively step 19): the AF entity requests the updating of its billing ticket corresponding to the first branch leg 1 respectively leg 2 with the entity CDR. Step 17 (respectively step 20): the CDR entity takes into account the billing update request received for leg 1 respectively leg 2.

Step 18 (respectively step 21): the CDR entity acknowledges receipt of billing update request for leg 1 respectively leg 2.

This solution has the advantage of being fully managed by the operator in a field as crucial as the billing of the user. It induces few modifications compared to the standard in the case where the adaptation of the application session according to the invention is carried out by the application server SCC AS 310. In fact, in this case, the only modification of structure concerns the addition of the Rx type interface between the PCRF entity 400 and the SCC AS 310.

It also allows the operator to modify the parameters of the application session to adapt it to the new type of access, renegotiating the session (new bandwidth, new coding, etc.).

The update of the application session can be triggered by I ¹ AF directly or after prior consultation of internal or external databases and / or Application servers to better qualify the requirements for the new session. Such a consultation may in particular make it possible to identify a transcoding function to be applied.

L ¹ AF, which also locally manages the change of "IP-CAN Type" / "RAT-Type", imperatively inserts these values in the SIP PANI header in the request that it sends and forwarded via conventional routing. in I ¹ IMS. The use of PANI is therefore made mandatory instead of optional as is the case in the current version of the 3GPP standard. The modification of the PANI according to the invention may consist in updating already existing parameters in its current format, namely "access-type""access-class" which will be filled respectively with the values of "RAT-Type" and

"IP-CAN Type" locally managed by I ¹ AF.

According to one variant, the modification of the PANI consists in integrating two new parameters "IP-CAN Type" and "RAT-Type" including the values reported by the media layer. In the same way, the other entities of I ¹ IMS must include, in the IMS billing tickets, the information received in the PANI header of the request.

SIP.

An example embodiment of a third embodiment of the invention will now be described with reference to FIG. 6. The situation described above is related to FIG. 1, according to which the user terminal UE1 has changed access type by passing from the AN1 access network to the AN2 access network.

Steps 1 to 8 of the diagram of Figure 6 are identical to those of Figure 5 and will not be described again. As previously, it is considered in this third example that the signaling path between the user terminal UE1 and the application system 10 can be divided into two branches Ieg1 and Ieg2, which are each the subject of a specific treatment and that I ¹ AF is in B2BUA mode.

Step 9: The AF 310 starts a time delay of predetermined duration. Step 10: The timer is complete. Step 11: L ¹ AF verifies that it has not received any application session update messages for the UE1 user terminal

Steps 12, 13: if no update message from the user has been found, I ¹ AF considers that this is an error case and terminates the current session in sending SIP BYE update messages on each branch of the signaling path.

Steps 14, 15: The entities involved in each branch acknowledge receipt of the SIP BYE message.

Steps 16 to 24: the application entities concerned each send a closing message of the billing tickets to the CDR entity that closes the tickets and issue a response message to each of the application entities.

According to a variant, after the expiry of the time delay, the AF implements the adaptation solutions of the application session according to the first and second embodiments of the invention, presented in relation to FIGS. 4 and 5. In this solution, the network leaves the terminal the opportunity to request itself to update or transfer its application session with the new access.

It should be noted that, to encourage it, the AF can also notify the terminal of the change related to its own access to the network.

Of course, other embodiments, including a combination of the various embodiments presented as an exemplary embodiment, can be envisaged.

Claims

A method for updating a current application session (S1) for a user terminal (UE1) of a telecommunications network (1) comprising an application system (10) able to manage said session, said terminal user accessing the telecommunications network via an access network (AN1, AN2), said method comprising a step (E1) of receiving a change notification related to said terminal access; user from a gateway (GW1) for access to the telecommunications network, said method being characterized in that it comprises, on receiving said notification, a triggering step (E4) of an adaptation action of the application session in the application system.

2. A method of updating an application session in progress according to claim 1, characterized in that the update action of the application session comprises at least sending a control command message. day to at least one entity of the application system.

3. A method of updating a current application session according to claim 2, characterized in that prior to sending the command message, the method comprises the following steps:

- activation (E2) of a timer; at the end of said delay, the check (E3) that no update message of the application session including said indication of change related to the access has been received for the user terminal; and in that the triggering step is carried out in case of positive verification.

4. A method of updating a current application session according to claim 3, characterized in that, prior to the activation of the timer, the method comprises a step of notifying the user terminal comprising said indication of change. linked to access.

5. A method of updating a current application session according to claim 3, characterized in that the control message is a session termination message (SIP BYE).

6. A method of updating an application session in progress according to claim 2 or 3, characterized in that the control message is an update message (SIP re-INVITE or SIP UPDATE) of the application session comprising the indication of change related to the access of said user terminal.

7. A method of updating a current application session according to one of claims 2 or 3, characterized in that the update message is a request for update (Accounting Request) billing ticket for to an entity in charge of billing (CDF 500).

8. A method of updating a current application session according to claim 6, characterized in that the update message is an event notification message (SIP NOTIFY) relating a change related to the access of said user terminal, intended for application entities (200, 300, 500) having previously subscribed to said notification.

9. Device (DMJ) for updating a current application session (S1) for a user terminal (UE1) of a telecommunications network (1) comprising an application system (10) able to manage said session said device comprising means for receiving a notification of change of an access type of said user terminal from a network access gateway, said device being characterized in that it comprises, on receiving said notification, means for triggering an update action of the application session in the application system.

10. Management entity (AF 110, 310) of an application session between a user terminal (UE1) and a telecommunications network (1), characterized in that it comprises a device (DMJ) for updating of the current session according to claim 9.

11. Computer program product downloadable from a communication network and / or stored on a computer readable medium and / or executable by a microprocessor, characterized in that it comprises program code instructions for the execution of the method for updating an application session according to claim 1.