WO2009122241A1

WO2009122241A1 - A method and system for least cost routing when forking

Info

Publication number: WO2009122241A1
Application number: PCT/IB2008/053118
Authority: WO
Inventors: Santoshi Nandan Satapathy
Original assignee: Alcatel Lucent
Priority date: 2008-04-02
Filing date: 2008-04-02
Publication date: 2009-10-08

Abstract

The invention provides a method and system for call forking in a telecommunications network using an IN service and the SIP protocol based on least cost routing. When a call is initiated the server performs a call charging function to obtain the cost of the call and prioritize the order of end points depending on cost. The charging functions are maintained in the application server of the communications network. Least cost routing when using number portability.

Description

Title

A METHOD AND SYSTEM FOR LEAST COST ROUTING WHEN FORKING

Background of the Invention

The present invention relates to the field of telecommunication core networks like PSTN (Public Switched Telephone Network), PLMN (Public Land Mobile Network), IMS (IP Multimedia Subsystem) etc and more particularly to the field of call forwarding and forking in these networks. Call forking enables the terminating gateway to handle multiple requests and the originating gateway to handle multiple provisional responses for the same call. Call forking is required for the deployment of the first-and-follow subscriber type of services.

The importance of forking is increasing, as the subscriber reduces the call cost. Currently forking is done in all extended IMS Private User Identity (IMPI). In a normal forking scenario a user A calls user B having IMPU B and user B has extended the IMPU into 3 IMPIs for example IMPI 1 being a landline, IMPI 2 being a mobile and IMPI 3 being a soft phone. The call from A to IMPU B will fork all the three IMPIs. Any one of the IMPIs can be answered and the others are timed out.

The present invention provides a method and system for effective call forking when the IMPI is of different phone types like mobile, landline, soft phone etc. Summary of the Invention

In accordance with one aspect of the disclosure, the invention provides a method for cost effective call forking in a standard IMS network. In this method the forking proxy will fork or extend the call only to one IMPI either landline or mobile or soft-phone for which cost of call is less. The method is generic in nature and its used can be customized depending on the market.

hi another aspect of the disclosure the invention provides a method for cost effective call forking in a standard PSTN network.

In yet another aspect of the disclosure the invention provides a method for cost effective call forking in a PLMN network.

In another aspect the invention provides for a system for cost effective call forking in any standard telecommunications network having multiple end points wherein the system includes a call handling server and a database server.

Brief description of the drawings

Figure 1 illustrates a normal call forking in an IMS network wherein the call wherein the call registered is parallely forked to three available end points (B1, B2, B3).

Figure 2 illustrates call forking implemented with cost priorities. Figure 3 is a block diagram, illustrating the system for call forking process as implemented in an IMS network.

Figure 4 is a block diagram illustrating the various data flows in the proposed call forking system in the event when a call is made to caller A.

Figure 5 is a block diagram illustrating the various data flows in the proposed call forking system when a caller B attempts to call caller A.

Detailed Description of the Drawings

Call forking is a process that enables the terminating gateway to handle multiple requests and the originating gateway to handle multiple provisional responses for the same call. Call forking is required for the deployment of the "find me/follow me" type of services e.g in mobile applications, when SIP services need to follow a SIP user. Ih this case it allows the SIP proxy to send an INVITE message to multiple endpoints (UAS devices).

AU core telecommunication networks provide for Call Forking service and the feature enables calls to reach all the available endpoints of the terminating side. Figure 1 illustrates a call forking process in a normal IMS network. When the call is forked to a specific user B, the user will attend the call with any of its endpoints (Bl, B2, B3). In case the user has multiple endpoints like one landline, one soft phone and a mobile phone, then the call will be forked to all the end points. The call rates for the calling party depends on the endpoint opted by the called party.

The present invention relates to the field of telecommunications networks and more particularly to call handling. According to one embodiment of the invention, it provides a method for sequential call forking depending on cost for IMS networks. This cost depended forking method will allow the user to choose a particular endpoint of the destination so that call cost can be managed.

In this aspect the invention provides a method for call forking where at a given time only one of the IMPI is forked and the forking is performed in the order of the cost incurred by the calling IMPU.

In the existing scenario when a call is forked each endpoint (Bl, B2,

B3) of the forwarded destination will get the call. The call cost and charging will be done based on the type of endpoint picked up by the destination user. The described method provides a value added call forking method (Figure 2) in which the end point of forking is decided based on cost. In this method parallel forking is avoided.

A user having multiple endpoints, like landline, mobile etc is registered with a call handling server. In this aspect of the invention the call handling server is an application server with CSCF. At the time of registration the user sets the priority of its endpoints. The Home Subscriber Server (HSS), or User Profile Server Function (UPSF), is a master user database that supports the entities of IMS network that actually handle calls. It contains the subscription-related information (user profiles), performs authentication and authorization of the user, and can provide information about the user's physical location. After registration all endpoints of destination are populated with priority given according to cost factor that is as per charging profiles in the HSS database. When the endpoints were registered with Serving Call Session Control Function (S-CSCF), their charging profiles are created as per type of endpoints. The Call Session Control Function (CSCF), are used to process SIP signalling packets in the IMS network. The call server (S-CSCF) will select the appropriate endpoint and route the call there with sequential call forking. So if one endpoint is not picking up then with a little delay, call will reach another endpoint according to priority.

A user opts for Value Added Service and can make choice of destination endpoints. The call handling server has a list of destination endpoints configured according to cost-priority for each user as per changing profiles. The online charging function is used for this purpose. When a call is made it is routed to the call handling server, it selects the first priority destination endpoint and forward this to that endpoint. Once a call is established the charging routine starts. The served user has options to change the selection at any point of time.

In another embodiment the invention relates to a system for call forking in a standard communication network (Fig 3). The system comprises of a softswitch-5020 CSC and a third party node hardware, which includes a call handling server or an application server and a database server. This aspect of the invention enhances the existing call forking to allow the served user select destination endpoints according to his convenience. This also provides an extra revenue generating opportunity for the service provider. Considering that caller A has 3 endpoints being landline, mobile and soft phone, these three endpoints have 3 private identities as IMPIl, IMPI2 and IMPI3. The basic implementation of the system is illustrated in Fig 4. When caller A (1) registers with the application server (3) for call forking depending upon call cost, caller A will send a REGISTER message towards the CSCF (2). In case of an IMS network the CSCF is a combination of Proxy- CSCF, Interrogating-CSCF and Serving-CSCF. After receiving the REGISTER message from caller A, the CSCF will retrieve its user data from database server (e.g. HSS in IMS network) (4). This is done by sending an SAR (service-assignment-request) to database server. The database server in return replies with SAA (service-assignment-answer). Both the SAR and the SAA are diameter protocol messages.

When the CSCF gets the user-data containing charging profiles of each endpoint related to all endpoints of caller A, it will forward the REGISTER message along with this user-data to the application-server. The application server will receive this REGISTER message and will set the priority for each endpoint of caller A depending on the cost of charging profiles of the endpoints. To store this priority listing in database server the application server will send a SNR (service-notification-request) and the database server replies with an SNA (service-notification-answer). Then the application server will send a 200 OK (SIP successful response) for caller A to CSCF. The CSCF then forwards the same to caller A.

Similarly when caller B is calling caller A (Fig 5) by dialing its mobile number an INVITE message will be sent from caller B to the CSCF. After receiving the INVITE message, the CSCF (6) will query DNS to find terminating (called party) CSCF. Once this information is obtained an INVITE message is sent to the terminating CSCF (7). This INVITE message is forwarded to the application server. The application server (8) receives the INVITE message and query for cost priority list to the database server. To obtain the query result the application server sends a UDR (User-data- request) to database server. The database server replies to this with a UDA (User-data-answer) message. Both the UDR and the UDA are diameter protocol messages. Now application server sends INVITE to landline (assuming it having the first priority) of caller A and starts one expiry timer for say 15 seconds. If landline of caller A is not replying with in the expiry time period, another INVITE message will be send from the application server to the endpoint having second priority and similarly to the third. When any endpoint of caller A answers the call, a 200 OK (successful response message) is sent to the application server via the CSCF.

Claims

1. A method of cost effective call forking in a standard communication network having multiple endpoints comprising steps of:

- generating the call cost for each endpoint of the called number by the call handling server;

- obtaining priorities for each endpoint depending on the call cost from the database server; and - routing the call sequentially to each endpoint based on the priorities assigned using the IN service and the SIP protocol.

2. A method of cost effective call forking as claimed in claim 1 wherein a charging ftmction residing in the call handling server generates the call costs for various endpoints.

3. A method of cost effective call forking as claimed in claim 1 wherein the priority of calling endpoints is stored in the database server at the time of user registration.

4. A system for cost effective call forking in a standard communications network having multiple endpoints comprising a call handling server, a database server loaded with a charging module and a register with a list of destination endpoints configured according to cost priority and the EST service providing interaction between the said call handling server and the database server.