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.
The clause 7.1 refer to the study for the support of IP flow mobility for s2c completed in Rel-10 and the results have been transferred in TS 23.261
. This clause will not be modified nor maintained during Rel-13 work. Solutions which was studied includes the possibility of dynamically routeing to specific accesses individual flows generated by the same or different applications belonging to the same PDN connection. The study of solutions to support routing of different PDN connections through different access systems is also in the scope of this TR. This study item also investigates the mechanisms for provisioning the UE with operator's policies for multi access PDN connectivity and flow mobility.
The scope of Rel-13 work is to identify the requirements and solutions for UEs with multiple interfaces which are simultaneously connected to 3GPP access and a WLAN access using a network-based mobility protocol, PMIP and GTP based S2a and S2b access to EPS.
The solutions studied from Rel-13 consider the following aspects:
The support of a PDN Connection active over multiple accesses simultaneously.
The association of one or multiple IP flows belonging to a PDN connection to an access system.
The movement of one or multiple IP flows belonging to a PDN connection between different access systems.
The triggers for IP flow mobility in the UE and the network.
UE-initiated and network-initiated NBIFOM.
The impact and the relationship to 3GPP related policies (e.g. PCC, ANDSF, ISRP, ISMP, RAN policy with no ANDSF etc.), if any, to support NBIFOM.
This work item doesn't include the scenario where the same IP flow is routed via different access system simultaneously.
Scenarios and solutions described in this document are applicable independently of whether IMS or non-IMS applications are used.