ation Mobile Communications Ecosystem Gxa provides transfer of (QoS) policy information from PCRF to the Trusted Non-3GPP accesses. Gxc provides transfer of (QoS) policy information from PCRF to the Serving Gateway. SGi is a reference point between the PDN GW and the packet data network. Rx transfer information between PCRF and operator's internal IP services. STa connects the trusted non-3GPP IP access with the 3GPP AAA Server/Proxy and transports access authentication, authorization, mobility parameters and charging-related information in a secure manner. SWa connects the Untrusted non-3GPP IP access with the 3GPP AAA Server/Proxy and transports access authentication, authorization and charging-related information in a secure manner. SWd connects the 3GPP AAA Proxy, possibly via intermediate networks, to the 3GPP AAA Server. SWm reference point is located between 3GPP AAA Server/Proxy and ePDG and is used for AAA signaling (transport of mobility parameters, tunnel authentication and authorization data). SWn is the reference point between the Untrusted Non-3GPP IP access and the ePDG. Traffic on this interface for a UE-initiated tunnel has to be forced towards ePDG. SWu is the reference point between the UE and the ePDG and supports handling of IPSec tunnels. The functionality of SWu includes UE-initiated tunnel establishment, user data packet transmission within the IPSec tunnel and tear down of the tunnel and support for fast update of IPSec tunnels during handover between two untrusted non-3GPP IP accesses. SWx is located between 3GPP AAA Server and HSS and is used for transport of authentication, subscription and PDN connection related data. 11.5.1 MM Process At a high level MM process includes three stages, namely network discovery, network entry, and seamless mobility (handover). These three stages are applicable within the context of EPS to WiMAX transfers and also in the vice versa scenario. 11.5.1.1 Network Discovery and Selection Network-assisted discovery is commonly used in cellular networks today wh