Patent ID: 8879539

Claim:
A method of data transfer between a first user terminal, arranged for supporting connections in a first Circuit Switched (CS) network and for simultaneously supporting Internet protocol Multi media System (IMS) signaling and CS signaling, and a second user terminal, arranged for supporting sessions and IMS signaling in an IMS, wherein said first CS network comprises a first Internet Protocol (IP) access converter arranged for supporting data transfer in said first CS network and in an IP network, said method comprising the steps of: receiving from a media gateway a third IP address at the IP access converter; delivering by said first IP access converter to a mobile switching center, to be delivered to said first user terminal using CS signaling in said first CS network, a second IP address to be used for data transfer by said second user terminal, the second IP address to be provided from said first user terminal to said second user terminal using end-to-end IMS signaling; receiving by said first IP access converter from said mobile switching center using CS signaling in said first CS network, a first IP address of the second user terminal, the first IP address of the second user terminal being provided from the second user terminal to the first user terminal using end-to-end IMS signaling and being provided to the mobile switching center from the first user terminal using CS signaling; and providing data transfer: between said first IP access converter and said mobile switching center by a CS connection in said first CS network; and between said first IP access converter and the media gateway using the third IP address; between said IP access converter and said second user terminal using real-time protocol, RTP; and performing: a) initiating a call using end-to-end IMS signaling between said first and second user terminals; b1) initiating by said first user terminal a first CS connection in said first CS network towards said first IP access converter using CS signaling; b2) allocating by said first IP access converter in relation to said first CS connection said second IP address to be used for data transfer by said second user terminal: b3) establishing, by said first IP access converter, said first CS connection and providing said second IP address to said first user terminal using CS signaling; c) providing said second IP address by said first user terminal to said second user terminal using end-to-end IMS signaling; d) determining by said second user terminal said first IP address to be used for data transfer by said first user terminal; e) providing said first IP address by said second user terminal to said first user terminal using end-to-end IMS signaling; and f) providing said first IP address by said first user terminal to said first IP access converter in said first CS network using CS signaling.