Method and Apparatus for Providing Circuit Switched Domain Services Over a Packet Switched Network

A method of establishing a mobile terminated call to a mobile station operating in a Long Term Evolution, LTE, radio access network, said method comprising the steps of:

• establishing an interface between the mobile station and a Packet Mobile Switching Center, PMSC, over a packet switched network utilizing U8 Circuit Switched Resources, U8-CSR, protocol signaling;
• sending by the PMSC, a U8-CSR PAGING REQUEST message to the mobile station notifying the mobile station of an incoming call;
• sending a Diameter AA-Request message from the PMSC to a Policy and Charging Rules Function, PCRF, requesting packet switched domain resources for the call;
• receiving in the PMSC, an AA-Answer message from the PCRF including terminating user plane addresses for a User Datagram Protocol, UDP, port and a network endpoint to be utilized for an uplink user plane Real Time Protocol, RTP, stream from the mobile station;
• establishing by the PMSC, a voice bearer channel between the mobile station and the network endpoint for transporting uplink and downlink user plane RTP streams;
• alerting and connecting the mobile station by the PMSC;
• and
• facilitating by the PMSC, bidirectional voice traffic between the mobile station and the network endpoint.

A Packet Mobile Switching Center, PMSC, for establishing calls to and from a mobile station operating in a Long Term Evolution, LTE, radio access network, said PMSC comprising:

• U8 Circuit Switched Resources, U8-CSR, protocol signaling means for establishing an interface with the mobile station over a packet switched network;
• Diameter AA protocol signaling means for obtaining packet switched domain resources for the call from a Policy and Charging Rules Function, PCRF;
• means for establishing a voice bearer channel between the mobile station and a network endpoint for transporting uplink and downlink user plane Real Time Protocol, RTP, streams;
• and
• means for facilitating bidirectional voice traffic between the mobile station and the network endpoint.