4.1 Architectural requirements and assumptions

23.1393GPP3GPP system - fixed broadband access network interworkingRelease 17Stage 2TS

The interworking architecture is based on EPC reference architecture defined in TS 23.401 [2] and TS 23 402 [3] and on BBF access network defined by BBF TR-291 [30], BBF TR-058 [7], BBF TR-101 [8], BBF TR-134 [11], and BBF TR-203 [6] excluding EAP-SIM (RFC 4186 [31]) functionality.

The interworking architecture supports trusted and untrusted model for the host-based mobility (S2c) and the untrusted model for the network based mobility (S2b). The trusted/untrusted Non-3GPP access network detection is performed as defined in clause 4.1.4 of TS 23 402 [3].

The reference architecture defined in TS 23 402 Rel‑11 clause 16 for Trusted WLAN using GTP s2a is applicable to the scenario where the Fixed Broadband / BBF Access network is considered as a trusted WLAN access. For such Fixed Broadband / BBF Access interworking deployments, in this version of the specification, the interactions between the EPC and the Fixed Broadband / BBF Access network consists only in S2a, STa interfaces and are not further detailed in this document. The detailed functional split within a Fixed Broadband / BBF Access network, the support of P2P link between the UE and the TWAG and the mapping between the S2a bearer QoS information received via S2a and Fixed Broadband Access specific parameters are outside 3GPP scope.

The architecture supports a UE simultaneously connected to the EPC via more than one access network for the same PDN connection as defined in TS 23.261 [9].

The architecture supports a UE that is capable of routing simultaneously active PDN connections to different APNs through different access networks as defined in TS 23.401 [2] and TS 23 402 [3].

The architecture supports the scenario of a single network operator deploying both the 3GPP EPC and the BBF access network and the scenario of two network operators one deploying the 3GPP EPC network and one deploying only the Broadband Forum Access network. Furthermore the architecture supports the roaming scenario between two PLMN operators.

The architecture supports local breakout of traffic in the EPC network whether a roaming subscriber is accessing the EPC via a 3GPP or a non-3GPP access network according to the design principles described in clause 4.1 of TS 23.401 [2].

The support of HeNB is based on reference architecture defined in TS 23.401 [2] and TS 36.300 [13], for the support of HNB in TS 23.060 [22] and TS 25.467 [12].

The architecture supports both offline and online charging in the 3GPP domain for the EPC routed traffic by means of accounting/charging information collected in 3GPP network elements.

The architecture supports STa/SWa reference points based accounting for the 3GPP UEs when traffic is NSWO in the Fixed Broadband Access network based on the assumption that the BBF network is able to collect per user accounting data for NSWO traffic of 3GPP UEs (i.e. BNG is able to recognize the traffic of individual 3GPP UEs), and periodically report this data via the STa/SWa reference points. If both EPC routed and NSWO are simultaneously provided to a UE, accounting information sent by BBF over SWa/STa shall allow distinguishing the accounting information for EPC routed traffic from that for NSWO traffic. This shall be supported based on Fixed Broadband Access accounting capabilities

NOTE 1: As defined in BBF TR-203 [6] the Fixed Aroadband Access may sent over SWa/STa accounting information for both EPC routed and NSWO.

NOTE 2: The online charging may be supported with limitation due to support of AAA RADIUS based accounting in the BBF network. It is assumed that the BBF does not need to be aware of whether online or offline charging is performed in the 3GPP domain

For S2b, the PCRF discovery function may select different PCRFs for PDN connection(s) for the UE in the PDN GW and for the IP session for NSWO traffic for the UE in the Fixed Broadband Access.

For S2c, the PCRF discovery function selects the same PCRF for all PDN connections for a certain IMSI and may select a different PCRF for IP-CAN session establishment over S9a for NSWO traffic.

There may be multiple TDFs deployed. If a TDF is used for traffic offloaded to the Fixed Broadband Access, the TDF selected for the NSWO traffic from the UE in the Fixed Broadband Access and that for the EPC routed traffic on SGi may or may not be the same.

In this Release, the policy interworking for user charging for NSWO traffic is only supported for scenarios without NAT in the Fixed Broadband Access domain.