In order to reduce the number of procedures in this specification certain editorial practices have been adopted. Though there are many independent factors, such as variants of S5/S8/S2b and attachment cases, these are in essence quite similar. So, rather than presenting the permutations of these factors separately and thereby needlessly repeating normative text, conventions have been adopted to combine this information in single procedures.
The S5 and S8 reference points in the EPC architecture have been defined to have both a GTP and PMIP variant. The GTP variant is documented in TS 23.401, while the PMIP variant is documented in this specification. Every effort has been made to eliminate duplication of normative text common to both specifications. Many figures in this specification refer to procedures in TS 23.401 to achieve this end. Common procedures between TS 23.401 and TS 23.402 (this specification), are represented in this specification in figures by text in shaded box(es) that reference the appropriate figure and steps in TS 23.401. The details of the common steps are only captured in TS 23.401.
The S2b reference point in the EPC architecture has also been defined to have both a GTP and PMIP variant. Both variants are documented in this specification. Every effort has been made to eliminate duplication of normative text common to both variants. Figures for the GTP variant of S2b refer to figures defined for the PMIP variant of S2b to achieve this end. Common procedures for both variants are represented in figures for GTP based S2b by text in shaded box(es) that reference the appropriate figure and steps defined for PMIP based S2b. The details of the common steps are only captured for the PMIP variant of S2b.
Attachment cases (as discussed in clauses 6.2.1 and 7.2.1) have been combined in a single figure. The different attachment cases can be accommodated by including optional items in the flows, for instance, a vPCRF that is only employed during when a roaming case or LBO is specified.
Multiple APN interactions may occur for many of the procedures defined in this specification. These interactions complicate the flows by introducing certain operations that may occur multiple times. Rather than produce unique flows for this purpose, we indicate where this possibility may occur in text.
This document specifies the stage 2 service description for providing IP connectivity using non-3GPP accesses to the Evolved 3GPP Packet Switched domain. In addition, for E-UTRAN and non-3GPP accesses, the specification describes the Evolved 3GPP PS Domain where the protocols between its Core Network elements are IETF-based.
ITU-T Recommendation I.130  describes a three-stage method for characterisation of telecommunication services, and ITU-T Recommendation Q.65  defines stage 2 of the method.
The specification covers both roaming and non-roaming scenarios and covers all aspects, including mobility between 3GPP and non 3GPP accesses, policy control and charging, and authentication, related to the usage of non-3GPP accesses.
TS 23.401 covers architecture aspects common to the Evolved 3GPP Packet Switched domain.
The procedures defined in the present document for WLAN access selection and PLMN selection replace the corresponding I-WLAN procedures specified in TS 23.234.
Interworking with 5GS is only supported for untrusted non-3GPP access using GTP-based S2b. Enhancements to support interworking with 5GS are captured in TS 23.501 and TS 23.502.
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
For a specific reference, subsequent revisions do not apply.
For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
IEEE Std 802.11-2012: "IEEE Standard for Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications".
For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
SectorID or Sector Address Identifier:
A UE that is capable of routing different IP flows to the same PDN connection through different access networks (see TS 23.261).
Inter-APN routing capable UE:
A UE that is capable of routing IP flows across multiple simultaneously active IP interfaces, each one associated with a specific APN. These interfaces may be linked to different access networks or to the same access network.
A radio access network that connects to 5GC, as defined in TS 23.501.
Non-seamless WLAN offload capable UE:
A UE that is capable of non-seamless WLAN offload as defined in clause 4.1.5.
MAPCON capable UE:
A UE that is capable of routing different simultaneously active PDN connections through different access networks.
Transparent Single-Connection mode:
A communication mode between a UE and a trusted WLAN (TWAN) where the TWAN may set up non-seamless WLAN offload or an S2a tunnel without explicit request from the UE.
A communication mode that is capable to support only a single connection at a time between a UE and a trusted WLAN (TWAN) . This connection can be used either for Non-Seamless WLAN Offload (as defined in clause 4.1.5) or for PDN connectivity. The use of the Single-Connection mode and the associated parameters of the connection (e.g. for NSWO, for PDN connectivity, APN, etc.) can be negotiated during authentication over TWAN.
A communication mode that is capable to support a single or multiple connections at a time between a UE and a trusted WLAN. One connection can be used for Non-Seamless WLAN Offload (as defined in clause 4.1.5) and one or more simultaneous connections can be used for PDN connectivity. The use of the Multi-Connection mode can be negotiated during authentication over TWAN and the requested PDN connection can be setup with the WLCP protocol for PDN connectivity.
For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
5G Core Network
Access Network Discovery and Selection Function
Common Pilot Channel
Delegated Mobile Network Prefix
Extensible Authentication Protocol
Evolved Packet Core
Evolved Packet Data Gateway
Evolved Packet System
Foreign Agent Care-of-Address
Fully Qualified Domain Name
High Rate Packet Data
HRPD Serving Gateway
IP Flow Mobility
Internet Key Exchange version 2
IP Mobility management Selection
Local Mobility Anchor
LTE-WLAN Radio Level Aggregation
LTE-WLAN Radio Level Integration with IPsec Tunnel