ANDSF or Access Network Discovery and Selection Function provides a way to allow mobile users to connect to Evolved Packet Core using non- 3GPP access radio technologies like WLAN, WiMAX, CDMA 2000 etc. The whole concept started in 3GPP release 8 where only WLAN case was considered. But in 3GPP release 10 a lot of improvements were done in this area and different use cases were added when UE can simultaneously connect to 3GPP access (GERAN, UTRAN, EUTRAN) and non-3GPP access technologies.
Simultaneous multi-access connectivity can be provided in several flavors:
- APCON – Multi-Access PDN Connectivity: The ability to have one APN (one PDN connection) on a cellular access and another APN on a non-3GPP access.
- IFOM – IP Flow Mobility: The ability on a per IP flow basis to choose on which access each flow should be supported and to move them seamlessly between accesses.
- Non-seamless Offload: The ability on a per IP flow basis to choose on which access each flow should be supported, but assuming the flows over the non-3GPP access will not go through the 3GPP Enhanced Packet Core (hence without support for session continuity).
The Wi-Fi Alliance has created a new standards activity, Hotspot2.0. Among the agreed requirements, HS2.0 will improve the ability of Wi-Fi devices to discover and securely connect to public Wi-Fi hotspots and thereby enable easier roaming between public Wi-Fi networks. The Hotspot2.0 work builds on the recently ratified IEEE 802.11u specification, which provides query mechanisms to enable devices to discover information about the roaming partners available and hence the type of credentials which may be used with the access point. It also incorporates the long ratified IEEE 802.11i based WPA2 Enterprise security specification which enables secure authentication and encryption for Wi-Fi data using a variety of user credentials including (U)SIM, digital certificates and username/passwords.
The combination of ANDSF and Hotspot2.0 is a particularly powerful enabler for a pain-free user experience across Wi-Fi and cellular networks.
This is a very good white paper on how this whole inter-networking between 3GPP access and other radio technologies can be achieved.