Mobility in IMS based Home Node B

A method for handing over an IP multimedia Subsystem, IMS, anchored session of a mobile device from a Home Node B of a mobile telecommunications network to another session control node of said mobile telecommunications network, the mobile device being circuit switched attached to said Home Node B, an interworking function unit enabling a connection between a circuit switched leg of the session to the Home Node B and a packet switched leg of the session between the Home Node B and the IMS, wherein said circuit switched leg is identified using a transaction identifier, the method comprising:

• receiving, by the interworking function unit, a handover request message, said handover request message including said transaction identifier;
• and
• forwarding, by the interworking function unit, the received handover request message to a Service Centralization and Continuity Application Server of the IMS.

An interworking function unit configured to hand over an IP multimedia Subsystem, IMS, anchored session of a mobile device from a Home Node B of a mobile telecommunications network to another session control node of said mobile telecommunications network, the mobile device being circuit switched attached to said Home Node B, the interworking function unit comprising an interface configured to receive a handover request message including a transaction identifier, and further configured to enable a connection between a circuit switched leg of the session to the Home Node B and a packet switched leg of the session between the Home Node B and the IMS, wherein said circuit switched leg is identified using said transaction identifier.

A method for handing over an IP multimedia Subsystem, IMS, anchored session of a mobile device from a Home Node B of a mobile telecommunications network to another session control node of said mobile telecommunications network, the mobile device being circuit switched attached to said Home Node B, an interworking function unit enabling a connection between the circuit switched leg of the session to the Home Node B and a packet switched leg of the session between the Home Node B and the IP Multimedia Subsystem, wherein a transaction identifier identifies said circuit switched leg, the method comprising:

• transmitting, by said Home Node B or a Home node B gateway to the interworking function unit, a handover request message, said handover request message including said transaction identifier;
• and
• transmitting a handover command to the mobile device.