RU2417544C2 - Methods and devices for transmitting signal connection information relating to signal connection between terminal and proxy call session control function (p-cscf) in internet protocol multimedia subsystem (ims) - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: disclosed is a method of transmitting information on the state of a signal connection in IMS. When on P-CSCF it has been determined that the state of the signal connection has changed to a new state, for example, the signal connection between P-CSCF and the terminal has been lost, a SIP request is sent from the P-CSCF to a serving call session control of unction (S-CSCF) module indicating the new state. The SIP request can be a REGISTER request. Alternatively, the terminal registration event packet is extended in order to include the state of the connection. The change in the connection can then be sent in a PUBLISH request. In the next alternative version, a new SIP event packet is supported by P-CSCF, and the S-CSCF subscribes that event packet and notifies using the P-CSCF when the state of the connection changes.

EFFECT: indication that a communication line previously used to transmit protocol signals for initialising a session between a user and a proxy call session control function module has been lost.

20 cl, 6 dwg

Description

FIELD OF THE INVENTION

The invention relates to a signaling link state for IP Multimedia Subsystem (IMS) users. In particular, but not necessarily, it refers to the P-CSCF, providing an indication that the communication link previously used to transmit SIP signals between the user and the P-CSCF has been lost.

State of the art

IP Multimedia (IPMM) is an example of a service that provides a dynamic combination of voice, image, message, data, etc. in the same session. By increasing the number of basic applications and the environment that can be combined, the number of services offered to the user will increase, and the experience of interpersonal communication will become richer. This will lead to a new generation of personalized communications services with rich multimedia capabilities, such as multimedia peer-to-peer communications, IPTV, etc.

These services can be based on the IP Multimedia Subsystem (IMS) architecture, which is the technology defined by the Third Generation Collaboration Project (3GPP) to provide IP Multimedia Services over Mobile Networks (3GPP TS 22.228, TS 23.228, TS 24.229, TS 29.228, TS 29.229, TS 29.328 and TS 29.329 version 5-7).

IMS uses the Session Initialization Protocol (SIP) to establish and manage calls or sessions between user terminals (or user terminals and application servers). The Session Description Protocol (SDP) carried by SIP signals is used to describe and negotiate the components of a session environment. Other multimedia applications that can be used for media transfer and control include the Real-time Transport Protocol and the Real-time Transport Control Protocol (RTP / RTCP), Session Message Relay Protocol (MSRP), and Hypertext Translation Protocol (HTTP).

FIG. 1 illustrates schematically how IMS integrates into a mobile network architecture in the case of 3GPP PS network access.

Session / Call Management functions (CSCF _s ) operate as SIP intermediaries with IMS. The 3GPP architecture defines three types of CSCF: Mediation CSCF (P-CSCF), which is the first point of contact within the IMS for the SIP terminal; Service CSCF (S-CSCF), which provides services to the user to which the user is subscribed; and Requesting CSCF (I-CSCF), whose role is to indicate the correct S-CSCF and transmit to it the S-CSCF request received from the SIP terminal through the P-CSCF.

If the user wants to access the services provided by the IP Multimedia Subsystem (IMS) network, then the user should usually register his own home network (this can happen when the user device is turned on). The IMS / SIP client in the user equipment initiates the registration process by sending a SIP REGISTER message to the Session / Call Control Service Function (S-CSCF) assigned to the user in the home network. When receiving a REGISTER message, a home network user may allow or deny access to the IMS network. A user device or User Equipment (UE) is connected through an access network, and the first contact point for a user in the IMS is a P-CSCF. As part of the registration process, the S-CSCF stores the contact address of the P-CSCF together with the address of the UE.

Signaling between the terminal and the P-CSCF is performed using an access network. It is possible that the communication line for transmitting information signals in the access network is lost. This can happen, for example, when the signal “directly through the air” is lost (for example, when the user passes through the tunnel) or when the user moves in the area of the congested cell. Continuous operation is performed on the 3GPP R7 to ensure that the P-CSCF receives an indication that the signal line has been lost, for example, via the R _x interface. However, there are no proposals that would be made regarding what the P-CSCF will do with this indication, other than simply forming the P-CSCF deregistration command. In other words, the P-CSCF would send the S-CSCF a SIP REGISTER request to unregister the terminal. This is not representative or universal enough to indicate the status of the signaling connection of the terminal. The IMS does not currently contain a mechanism for transmitting an indication of signal line loss.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there is provided a method for transmitting signaling state information in an IP Multimedia Subsystem, the signaling state information identifying the state of the signaling connection between the terminal and the intermediary node in a telecommunication network, the method comprising:

determining on the intermediary node that the state of the signaling connection has changed to a new state; and

sending a SIP request from the IMS intermediary node to the IP node of the Multimedia Subsystem, while the SIP request indicates a new state.

A SIP request indicating a new connection state may be a REGISTER request, in which case a new header parameter indicating a terminal connection status is included in the request.

In general, the terminal will be registered on the IMS host when it initially connects to the network. In one implementation, the initial state of the signaling connection may be registered by the proxy and IMS node during this initial registration. The new connection state (as determined by changing the connection state) can then be forwarded to the IMS host using a PUBLISH request.

In another embodiment, the proxy maintains a contact information document containing a signaling connection state. The IMS host can then sign a contact information document. The intermediary node can send a NOTIFY IMS request to the node indicating the initial state of the signaling connection when the IMS node first signs the contact information document. Further, a NOTIFY request can then be sent to the IMS host when the state of the connection changes.

The mediation node is preferably a Mediation Call / Session Management Function. An IMS host may be a Call / Session Management Service Function.

The signaling connectivity state can be defined as “connected”, “disconnected”, “unclear” or “unknown”, although it will be understood that any suitable state may be used. In one embodiment, the step of determining at the proxy node that the state of the signaling connection has changed to a new state comprises determining that the connection between the terminal and the proxy is lost.

The IMS node may unregister the terminal in response to a notification that the signaling connection between the terminal and the intermediary node has been lost. Alternatively, the IMS node may take into account the state of the signaling connection between the terminal and the intermediary node when directing traffic to registered user terminals.

In accordance with another aspect of the present invention, there is provided a method of registering a terminal on an IMS IP Multimedia Subsystem node, comprising storing registration information on an IMS node, the registration information including a signaling state between the terminal and the intermediary node.

In accordance with yet another aspect of the present invention, there is provided a method of registering a terminal on an IMS IP Multimedia Subsystem node, comprising sending a SIP REGISTER request to an IMS node, wherein the SIP REGISTER request includes a connection status parameter indicating a signaling connection status between the terminal and the intermediary node .

In accordance with another aspect of the present invention, there is provided a method of registering a terminal on an IMS IP Multimedia Subsystem node, comprising including a connection status parameter that indicates a signaling connection state between the terminal and the intermediary node in the SIP registration event packet.

In accordance with another further aspect of the present invention, there is provided a method of operating an intermediary node in an IP Multimedia Subsystem, comprising creating a SIP contact event information packet that monitors the state of the signaling connection between the terminal and the intermediary node.

In accordance with another aspect of the present invention, there is provided a method of operating an IP Multimedia Subsystem node, comprising signing a SIP contact event information packet at a proxy node, the SIP contact event information packet including indicating a signaling state between the intermediary node and the terminal.

In accordance with another aspect of the present invention, there is provided a Session / Call Mediation Function for use in an IP Multimedia Subsystem, comprising:

input means for receiving information indicating the current state of the signal connection of the terminal trying to access the IP Multimedia Subsystem; and

output means for providing the current state of the signal connection to the IP node of the Multimedia Subsystem.

In accordance with another further aspect of the present invention, there is provided a Session / Call Mediation Function for use in an IP Multimedia Subsystem designed to create a contact event information packet that monitors the signaling state between the Session / Call Mediation Function and a terminal.

In accordance with another aspect of the present invention, there is provided a system for transmitting signaling state information in an IP Multimedia Subsystem, wherein signaling state information indicates a signaling state between a terminal and an intermediary node in a telecommunication network, the system comprising:

input means at the intermediary node for determining that the state of the signaling connection has changed to a new state;

output means at the intermediary node for sending a SIP request indicating the new state; and

An IMS IP Multimedia Subsystem host designed to receive a SIP request and take appropriate action.

Brief Description of the Drawings

FIG. 1 illustrates schematically the architecture of the IP Multimedia Subsystem in a third generation mobile communication system;

FIG. 2 is a schematic view of a signal path between a SIP UE and an S-CSCF;

FIG. 3 illustrates a signal sequence to ensure that the S-CSCF is informed of the loss of a unidirectional signal channel;

FIG. 4 illustrates an alternative signal sequence to ensure that the S-CSCF is informed of the loss of a bearer signal;

FIG. 5 illustrates a signal sequence for delivering S-CSCF connection information; and

FIG. 6 illustrates a signal sequence for notifying the S-CSCF of the loss of a bearer signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As described above, much work has already been done to ensure that the P-CSCF receives information on the R _x interface that the terminal (UE) has been disconnected. The examples below provide mechanisms to ensure that this information is sent to the S-CSCF.

FIG. 2 is a schematic representation of a signaling path 1 between a UE 2 and an S-CSCF 3 through a P-CSCF 4. A communication link 5 is provided by an access network (not shown) of the UE. The P-CSCF includes a monitoring mechanism 6 that determines if signal path 1 from the UE is lost.

FIG. 3 illustrates a signal sequence between the P-CSCF and the S-CSCF, which allows connection data of the UE to be recorded by the S-CSCF. In this example, this is achieved by introducing a new contact header parameter indicating the connection status of the UE. Suitable values for status information may include: “connected,” “disconnected,” “obscure,” and “unknown.” An “unclear” state can be used when there is a suspicion that a connection failure has occurred.

The signal sequence is as follows:

Step 1: The UE registers its contact with the S-CSCF in a known manner. The UE and the P-CSCF sign a registration event packet to receive notifications of registration information supported by the S-CSCF.

Step 2: The P-CSCF determines the loss of a signaling link between it and the UE. This can be achieved, for example, using the P-CSCF, accepting such an indication on the R _x interface. The P-CSCF sends a REGISTER S-CSCF request. The REGISTER request includes the contact address of the UE, together with the new contact header parameter. The new parameter contains details of the contact state of the connection. In this example, the state is “eroded”. The P-CSCF inserts its SIP URI address into the From header.

Step 3: when the S-CSCF receives the REGISTER request, it determines that the request was created by a trustworthy entity. One way to achieve this is to compare the P-CSCF address received in the request with the P-CSCF address previously stored in the registration procedure in Step 1. Once the S-CSCF confirms that the P-CSCF is authorized, then the S-CSCF returns 200 OK answer. This confirms that the contact disconnected state contained in the REGISTER request has been recorded.

Stage 4: having the received information that the registered contact is disconnected, the S-CSCF may choose to unregister the contact or may choose to save this information for future use when it receives traffic that should be directed to the user's contact (s).

In other words, the state of the signaling connection of the UE is recorded in the S-CSCF in a similar manner for the location when the user first makes contact, although it will be understood that the P-CSCF registers the state of the signaling connection, although when the user first makes contact, he presents a UE that registers its location.

An alternative signal sequence for acquiring connection information for an S-CSCF is shown in FIG. 4. This alternative extends the definition of the Registration Event Packet (RFC 3680) by adding optional signaling contact status information to the contact information element of the registration information document. The connection status of the UE is included in the initial registration in the S-CSCF, in addition to location and identification. This can be achieved using the S-CSCF, assuming that the initial state of the signal connection is still “connected” (and if it is known that) the initial registration takes place in the entire signal channel. Alternatively, the P-CSCF may provide an initial signaling connection to the S-CSCF using a SIP PUBLISH request. If the P-CSCF determines that the connection status has changed, then this information is sent to the S-CSCF using a PUBLISH request. The S-CSCF updates its registration information in response to the information included in the PUBLISH request. As before, suitable values for status information may include: “connected,” “disconnected,” “obscure,” and “unknown.” An “unclear” state can be used when there is a suspicion that a connection failure has occurred.

The signal sequence is as follows:

Step 1: The UE registers its contact with the S-CSCF in a known manner. The S-CSCF examines the state of the signaling connection during this initial registration.

Step 2: The P-CSCF determines the loss of a signaling link between it and the UE. As before, this can be achieved, for example, using the P-CSCF, which accepts such an indication on the R _x interface.

The P-CSCF sends a PUBLISH S-CSCF request. The PUBLISH request includes a document containing information about the new contact connection status. In this example, the state is “disconnected”. The P-CSCF inserts its SIP URI address into the From header.

Stage 3: when the S-CSCF receives the PUBLISH request, it determines that the request was created by a trustworthy object. One way to achieve this is to compare the P-CSCF address received in the request with the P-CSCF address previously stored in the registration procedure in Step 1. Once the S-CSCF confirms that the P-CSCF is authorized, then the S-CSCF returns 200 OK answer. This confirms that the contact disconnected state contained in the REGISTER request has been recorded.

Step 4: having the received information that the registered contact is disconnected, the S-CSCF may choose to unregister the UE or it may choose to save this information for future use when it receives traffic that should be directed to the user’s contact (s).

This mechanism is general because it allows objects other than the S-CSCF to obtain contact connection information by subscribing to the registration information supported by the S-CSCF, which now includes this information.

In a further alternative, a new SIP event packet is defined that allows the P-CSCF to deliver connection contact information. The SIP event notification structure (PFC 3265) is used. In this alternative, the P-CSCF maintains contact connection status information in the SIP Event Package with the new Status Information Document. This allows other entities, such as the S-CSCF, to sign this information and receive status change notifications.

The sequence of the initial installation is shown in figure 5 and is presented below:

Step 1: The UE registers its contact with the S-CSCF. During the registration process, the P-CSCF and S-CSCF store each other's address. They also store initial contact information and initial contact status between the UE and the P-CSCF. The UE and the P-CSCF sign the registration event packet to receive registration information notifications supported by the S-CSCF. They are procedures of the current 3GPP standard. Additionally, the P-CSCF creates a Contact Information Document with contact connection status information and can provide the S-CSCF SIP URI with the address of the created document as part of the registration procedure. The P-CSCF has supported this document for as long as it maintains contact registration status.

Step 2: if a contact has been registered, the S-CSCF signs the connection status of the contact. This is achieved by sending a SIP SUBSCRIBE request to the P-CSCF requesting the Contact Information Document of the registered contact.

Stage 3: when the P-CSCF receives the SUBSCRIBE request, it determines that the request was created by a trustworthy object. One way to achieve this is to compare the S-CSCF address received in the request with the S-CSCF address previously stored in the registration procedure in Step 1. The P-CSCF saves the S-CSCF address as a subscriber to Contact Information. With an authorized S-CSCF as a trusted subscriber, the P-CSCF responds 200 OK to the SUBSCRIBE request.

Step 4: The P-CSCF then sends a SIP NOTIFY request to the new subscriber (S-CSCF) with the current Contact Information Document, in this example indicating that the contact is connected.

Step 5: when the S-CSCF receives a NOTIFY request, it saves Contact Information for future use and responds with 200 OK.

It should be noted that the P-CSCF provides the SIP URI of the Contact Information Document during registration.

If the signal line is lost, then this is determined, as before, using the P-CSCF (for example, by receiving instructions on the R _x interface). The signal sequence for transmitting this information is illustrated in FIG. 5 and is executed as follows:

Step 6: if the P-CSCF determines the loss of a signaling link between it and the UE, then the P-CSCF sends a SIP NOTIFY S-CSCF request. A NOTIFY request includes a modified Contact Information Document with new contact connection status information. In this example, he indicates that the contact is now disconnected.

Step 7: if the S-CSCF receives a NOTIFY request, it updates the contact connection status information and sends a 200 OK response.

Step 8: having the received information that the registered contact is disconnected, the S-CSCF may choose to cancel the registration or it may save this information for future use when it receives traffic that should be directed to the user's contact (s). If the contact is de-registered, then the S-CSCF subscription to the connection status event ends.

This mechanism also allows entities other than the S-CSCF to obtain connection information for a contact by signing contact information supported by the P-CSCF.

It will be understood that deviations from the above described embodiments may still fall outside the scope of the invention. For example, all implementations describe the above situation where a clear indication of signal loss is received by the P-CSCF over the R _x interface. However, other mechanisms may be provided by which the P-CSCF notifies of a loss of signaling connection. For example, a lack of response from the UE may be used after a certain period of time. Alternatively, a Network Control Message Protocol (ICMP) message can be received from the IP transport network. Other mechanisms may also be used.

It will also be understood that all of the above implementations are considered mainly in connection with the loss of signaling connection between the UE and the P-CSCF. It is noted in each case that the S-CSCF may update the connection status for future use. If the connection is reestablished, the system in accordance with the present invention can be used to forward this S-CSCF information so that it can update its status again. The invention is not limited to the connection loss report between the UE and the P-CSCF: it relates to a communication status report.

Moreover, all examples describe the transmission of signaling state information from the P-CSCF to the S-CSCF. It will be understood that the invention can be used to transmit this information from the P-CSCF to other nodes of the IMS center. To take appropriate action.

Claims (20)

1. The method of transmitting information about the status of the signaling connection in the multimedia subsystem of the Internet Protocol (IP) (IMS), moreover, the information on the status of the signaling connection identifies the state of the signaling connection between the terminal and the intermediary function of the session / call control (P-CSCF) in a telecommunication network wherein the method comprises: determining in the P-CSCF module that the state of the signaling connection has changed to a new state; and sending a Session Initiation Protocol (SIP) request from the P-CSCF module to the Session / Call Control Service Function Module (S-CSCF) of the IP multimedia subsystem, wherein the SIP request indicates a new state. 2. The method of claim 1, wherein the SIP request indicating the new connection status is a REGISTER request. 3. The method of claim 2, wherein the REGISTER request includes a header parameter indicating a terminal connection status. 4. The method of claim 1, wherein the SIP request indicating the new connection status is a PUBLISH request. 5. The method according to claim 4, in which the terminal is registered in the S-CSCF module, and in which the initial state of the signal connection is registered by the P-CSCF module and the S-CSCF module when the terminal is registered in the S-CSCF module. 6. The method according to claim 1, in which the P-CSCF module supports a contact information document containing a signaling state, and in which the S-CSCF module subscribes to a contact information document. 7. The method according to claim 6, in which, when the S-CSCF module subscribes to a contact information document, the P-CSCF module sends a SIP NOTIFY request to the S-CSCF module indicating the initial state of the signaling connection. 8. The method according to claim 6 or 7, in which the SIP request indicating the new connection status is a NOTIFY request. 9. The method according to claim 1, in which the state of the signal connection can be established as one of the following list: connected, disconnected, unclear and unknown. 10. The method according to claim 1, wherein the step of determining in the P-CSCF module that the signal connection state has changed to a new state, comprises determining that the signal connection between the terminal and the P-CSCF module has been lost. 11. The method of claim 10, wherein the S-CSCF module deregisters the terminal in response to a notification that the signal connection between the terminal and the P-CSCF module has been lost. 12. The method according to claim 1, in which the S-CSCF module takes into account the state of the signal connection between the terminal and the P-CSCF module when the graph is sent to the terminal. 13. A method of registering a terminal in a session / call control service function (S-CSCF) module of an IP multimedia subsystem, comprising storing registration information in an S-CSCF module, the registration information including a signaling state between the terminal and the mediation control function module Session / Call (P-CSCF). 14. A method of registering a terminal in a Session / Call Control (S-CSCF) service module of an IP multimedia subsystem, comprising sending a SIP REGISTER request to the S-CSCF module, the SIP REGISTER request including a connection status parameter indicating a signaling connection between the terminal and a Session / Call Control Intermediary Function Module (P-CSCF). 15. The method of registering the terminal in the module of the session / call control service function (S-CSCF) of the IP multimedia subsystem, comprising the inclusion of a connection status parameter that indicates the signaling connection between the terminal and the session / call mediation function module (P-CSCF), SIP event packet registration. 16. The method of operation of the intermediary function of the session / call control (P-CSCF) in the IP multimedia subsystem, comprising creating an event packet with information about the SIP contact, which monitors the state of the signal connection between the P-CSCF module and the terminal. 17. The method of operation of the IP node of the multimedia subsystem, comprising subscribing to an event packet with SIP contact information in a Session / Call Control (P-CSCF) mediation function module, wherein the SIP contact information event packet includes an indication of signaling connection status between P-CSCF module and terminal. 18. Session / call control intermediary function module (P-CSCF) for use in an IP multimedia subsystem, comprising: input means for receiving information identifying a current state of a signal connection of a terminal trying to access an IP multimedia subsystem; and output means for transmitting the current state of the signaling connection to the IP node of the multimedia subsystem. 19. Session / Call Control Intermediary Function Module (P-CSCF) for use in an IP multimedia subsystem designed to create an event packet with SIP contact information that monitors the signaling state between the P-CSCF module and the terminal. 20. A system for transmitting signaling state information in an IP multimedia subsystem, the signaling state information identifying the state of the signaling connection between the terminal and the Session / Call Control (P-CSCF) mediation module in a telecommunication network, the system comprising: input means in the P-CSCF module to determine that the state of the signaling connection has changed to a new state; output means in the P-CSCF module for sending a SIP request indicating a new state; and an IP multimedia subsystem Session / Call Control (S-CSCF) service module for receiving a SIP request and taking an appropriate action.

Images