2015/06 153 p.
Release 8 EPS introduced a multi access 3GPP system where different heterogeneous access systems are connected to a common core network. However, in Release 8 EPS, the subscriber cannot communicate using multiple accesses simultaneously. The subscriber can establish a single PDN connection or multiple simultaneous PDN connections in Release 8 EPS, but all the traffic exchanged by the subscriber, regardless of the PDN connection it belongs to, is routed through the same access system. Similarly, Release 8 introduced mobility enhancements to the I-WLAN architecture to support session continuity for any application between 3GPP and I-WLAN accesses, but this will not be further developed in Rel-13.
Devices with multiple wireless interfaces (e.g. 3GPP , WLAN, etc.) are becoming commonly available and the set of applications running in the mobile devices is diversifying with some applications suited to run over 3GPP access systems and other applications well suited to run over some other - complementary - access systems (e.g. ftp transfer via WiFi in parallel to VoIP over LTE).
The scope of this document is to study the scenarios, requirements and solutions for UEs with multiple interfaces which will simultaneously connect to 3GPP access and one, and only one, non-3GPP WLAN access.