Patent Application
20080004006
The present invention can be better understood with reference to
Networks 101 and 103 are responsible for call and session control provided by the IMS in a subscriber's home network. Networks 101 and 103 manage SIP sessions, provides features and services, coordinates with other network elements for session control, and allocates media resources.
IMS networks 101 and 103 each include a plurality of functions and components, which may be installed on separate servers or can alternately share the same server. This allows for flexible packaging for various customer needs. IMS network 101 comprises S-CSCF (Serving-CSCF) 111, I-CSCF (Interrogating-CSCF) 121, P-CSCF (Proxy-CSCF) 131, and applications 141 and 151. Roaming IMS network 103 comprises S-CSCF 113, I-CSCF 123, P-CSCF 133, and applications 143 and 153.
S-CSCF 111 manages SIP sessions and coordinates with other network elements for call/session control. S-CSCF 111 performs SIP registration, session control, service control, call monitoring, and security. SIP registration comprises processing SIP REGISTER requests and maintaining subscriber data and state information for the duration of the registration session. Session control comprises performing call/session setup, modification, and termination. Service control comprises interaction with Application Services platforms for the support of features and services. Call monitoring comprises call monitoring and recording for accounting and other related services. Security comprises providing security for the session.
SIP user clients communicate to the various application servers via S-CSCF 111. S-CSCF 107 provides the messaging filtering, message forwarding, and transaction and session control functions for the sessions initiated by SIP signaling. S-CSCF 111 also allows the various SIP-based application servers to communicate with each other. S-CSCF 111 also preferably provides SIP proxy functions for forwarding SIP messages to the proper application server and allowing application servers to subscribe to SIP dialogs between SIP clients and servers.
Because S-CSCF 111 supports standard SIP messages, the user clients and SIP application servers can span a wide variety of telephony and non-telephony services. For example, S-CSCF 111 can provide the message filtering and forwarding for SIP-based services such as Instant Messaging (IM), Push-To-Talk, and multimedia services.
I-CSCF 121 is the contact point within network 101 for all connections destined to a subscriber connected to network 101 or a roaming subscriber currently located within the service areas supported by network 101. Network 101 may include multiple I-CSCFs. I-CSCF 121 assigns an S-CSCF to a user performing SIP registration. I-CSCF 121 also obtains from HSS 105 the address of S-CSCF 111 and uses the address to route a SIP request or response received from a network towards S-CSCF 111.
P-CSCF 131 is preferably the first contact for a SIP mobile unit to gain access to network 101 from the access packet network domain. P-CSCF 131 provides the necessary SIP routing capability between SIP mobiles and network 101. P-CSCF 131 also coordinates with the access network to authorize the resources and Quality-of-Service (QoS). For services that are offered by the home IMS network, P-CSCF 131 relays the SIP signaling to the IMS server in the home network.
HSS 105 is the master subscriber database for system 100 and includes registration status and subscription data for users. The data within HSS 105 is used by the different network core functional entities in IMS 100 when processing subscribers. HSS 105 includes user data that can be downloaded to S-CSCF 111 and S-CSCF 113. HSS 105 stores temporary data with the location of S-CSCF 111 where the user is currently registered.
Client 107 is a subscriber device that is preferably capable of placing and receiving calls within system 100, either by utilizing home network 101 or, when roaming, by utilizing roaming network 103.
Elements in roaming network 103 perform similar functions to similarly-names elements in home network 101.
In accordance with an exemplary embodiment, IMS client 107 has home network 101 as its home network. IMS client 107 registers (201) with roaming P-CSCF 133 by sending a registration message. In a typical network, P-CSCF 133 is unaware of the home system of IMS client 107. In an exemplary embodiment, the registration message includes the IP address of client 107, the address of P-CSCF 133, and optional SIP x-header fields.
P-CSCF 133 passes (203) registration information to I-CSCF 123. P-CSCF also passes (205) registration information to I-CSCF 121. I-CSCF 121 looks up (207) client 107, preferably utilizing Diameter, in HSS 105.
HSS 105 passes (209) the information relating to client 107 to I-CSCF 121. The information includes the address of S-CSCF 111. I-CSCF 121 forwards (211) registration information to S-CSCF 111.
Upon receiving an indication that client 107 is located in roaming system 103, S-CSCF 111 preferably sends (213) a message to application 141. S-CSCF 111 preferably extracts the contact information of IMS client 107 from the registration message. In an exemplary embodiment, this information replaces the address of S-CSCF 111. In an exemplary embodiment, S-CSCF 111 can send the message to multiple applications.
The message includes an indication that client 107 has registered with roaming network 103. The message preferably provides an enhanced application notification to application 141. The enhanced application notification preferably includes SIP headers, the IP address of client 107, and P-CSCF 133 of the newly registered network.
Application 141 includes data related to the current location of roaming client 107. In an exemplary embodiment, the address of client 107 is the address of P-CSCF 133. In a further exemplary embodiment, the address of client 107 is the IP address of client 107. In a further exemplary embodiment, the address of client 107 is the PDSN Home IP address of client 107.
Additionally, application 141 has capability to notify other applications that register for notification of incoming client registrations. Application 141 preferably determines if client 107 is roaming by checking either the incoming IP address of the client or domain of the P-CSCF.
Application 141 in home network 101 can notify other applications in home network 101. In accordance with an exemplary embodiment, other applications at home network 101 register with application 101 if they want to be updated with the registration status of roaming clients. Messages sent to other applications can include the IP address of the roaming client, the P-CSCF of the roaming network, or SIP xhdr fields. This allows application 141 to route directly to client 107 utilizing the IP address of client 107 or the address of P-CSCF 133 without passing through the S-CSCF 111. This reduces delays for applications in either home network 101 or roaming network 103 when communicating with the client 107.
In accordance with an exemplary embodiment, when client 107 deregisters from network 103 application 141 is notified of the deregistration utilizing the standard IMS protocol. Application 141 then preferably notifies other applications, such as application 151, application 153, and application 143.
While this invention has been described in terms of certain examples thereof, it is not intended that it be limited to the above description, but rather only to the extent set forth in the claims that follow.
