INTER-SYSTEM MOBILITY IN INTEGRATED WIRELESS NETWORKS
A system is disclosed for providing inter-system mobility in integrated LTE and WiFi systems. A control plane interface, referred to as the S1a-C interface, is defined between a trusted WLAN access network (TWAN) and a mobility management entity (MME) comprised in an LTE wireless access network. A user plane interface, referred to as the S1a-U interface, is defined between the TWAN and a server gateway (SGW) in the LTE wireless access network. The MME operates as a common control plane entity for both LTE and TWAN access, while the SGW operates as a user plane gateway for both LTE and TWAN. The integrated MME and SGW allow for user equipment (UE) to access the capabilities of a packet data network (PDN) through either the LTE access network or TWAN.
1 . A user equipment (UE) comprising a processor, a memory, and computer-executable instructions stored in the memory which, when executed by the processor, cause the UE to:
establish, with a trusted wireless local area network (TWAN), a session on a first packet data network (PDN) connection, the first PDN connection being between the UE and the TWAN;
discover a cellular network;
determine, based on a policy, to transfer the session from the TWAN to the cellular network;
send, over a first interface and to the cellular network, a handover request, the handover request pertaining to establishing a second (PDN) connection, the second PDN connection being between the UE and the cellular network, the handover request comprising a handover indication, an attach type, and an access point name (APN);
receive, from the cellular network over the first interface, a handover response, the handover response comprising an internet protocol (IP) address or a prefix assigned for the second PDN connection;
receive, over a second interface and from the TWAN, a release message, the release message instructing the UE to release the first PDN connection; and
send, over the second interface and to the TWAN, an acknowledgement, the acknowledgement pertaining to the release of the first PDN connection.
2 . The UE of claim 1 , wherein the IP address or prefix assigned for the second PDN connection matches an IP address or prefix assigned for the first PDN connection.
3 . The UE of claim 1 , wherein the instructions further cause the UE to establish a radio bearer over the cellular network.
4 . The UE of claim 3 , wherein the instructions further cause the UE to send and receive data via the radio bearer.
5 . The UE of claim 1 , wherein the policy is an access network discovery and selection function (ANDSF) policy.
6 . The UE of claim 1 , wherein the UE receives in the response a charging ID that was assigned to the PDN connection through the TWAN.