Hybrid IMS-GSM system and method for establishing an outgoing GSM call as an enterprise call

摘要

The application relates to systems based upon Voice-over-IP and Session Initiation Protocol-based signaling systems that utilize the existing enterprise IP infrastructure. Mobile communication devices are being enhanced to provide SIP-based communications (including VoIP) over WLAN access as well as cellular networks, thereby allowing these devices to provide mobile telephony communications capability when within the enterprise as well as when away from the enterprise. However, these networks cannot currently commercially support carrier-class VoIP telephony services. In addition, enterprise calls shall be integrated with the IMS network architecture. This is achieved by the present invention in that instead of a VoIP call, a circuit-switched call is established. In particular, a network node (404) is operable, responsive to receiving (408) a SIP INVITE request from an enterprise user (118) to initiate origination of an outgoing cellular call to a called party (120), for establishing (418) a first call leg to the enterprise user (118) by sending a circuit-switched call that identifies an enterprise address of the enterprise user (118) as a calling line identity. The network node (404) includes functionality for establishing (430) a second call leg to the called party (120). The first and second call legs are then patched to establish an end-to-end communications path between the enterprise user (118) and the called party (120), wherein the enterprise address instead of the non-enterprise address is presented to the called party (120) as a calling line identity with respect to the outgoing cellular call from the enterprise user (118).