System, apparatus and method for providing services

A method for providing services, comprising:

• registering a UE in a Circuit Switched, CS, network;
• registering the UE in an IP Multimedia Sub-system, IMS, network, wherein registering the UE in the IMS network comprises registering CS access capability of the UE in the IMS network;
• and
• establishing a call branch at the CS network side between the UE and the IMS network for an IMS session,

A method for UE accessing an IP Multimedia Sub-system, IMS, network via a Circuit Switched, CS, network, comprising:

• registering in a CS network;
• sending an Unstructured Supplementary Service Data, USSD, Request to an IMS network;
• registering CS access capability of the UE in the IMS network;
• and
• establishing a call branch at the CS network side with the IMS network for an IMS session.

An apparatus for providing services, comprising:

• a call processing module at a UE side, a registration module at the UE side and a communication module at the UE side, being connected to each other, any of which is used for saving the address of a Circuit Switched Adapter, CSA;
• wherein,
• the registration module is adapted to register CS access capability of the apparatus in an IP Multimedia Sub-system, IMS, network;
• the call processing module is adapted to generate call establishment information, and establish a call branch at the CS network side between the UE and the CSA;
• and
• the communication module is adapted to transmit the call establishment information to the CSA.

An apparatus for providing services, comprising:

• a call processing module at a Circuit Switched Adapter, CSA, side, a registration module at the CSA side and a communication module at the CSA side, which are connected to each other, wherein
• the registration module is adapted to register CS access capability of the UE in an IMS network;
• the call processing module is adapted to generate call establishment information, and establish a call branch at the CS network side between the UE and an IP Multimedia Sub-system, IMS, network;
• and
• the communication module is adapted to transmit the call establishment information to the CSA.