8.2.6 Non-3GPP IP Access to 3GPP Access Handover with PMIPv6 on S2a/b for Chained PMIP-based S8

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

The steps involved in the handover from a trusted or non-trusted non-3GPP IP access to a 3GPP access connected to EPC are depicted below for roaming cases with chained S2a/b and PMIP-based S8. It is assumed that while the UE is served by the non-3GPP IP access, a PMIPv6 tunnel is established between the non-3GPP access network and the Serving GW and another one between the Serving GW and the PDN GW.

Figure 8.2.6-1: Handover from Trusted or Untrusted Non-3GPP IP Access to 3GPP Access with chained S2a/b and PMIP-based S8

In case of handover to E-UTRAN, the following applies for connectivity to multiple PDNs:

– If the UE is connected to both 3GPP access and non-3GPP access before the handover of PDN connections to 3GPP access is triggered, the procedure as per Figure 8.2.1.2-1 before step 18 shall be skipped and the UE shall only perform step 18 of Figure 8.2.1.2-1 for each PDN connection that is being transferred from non-3GPP access.

– If the UE is connected only to non-3GPP access before the handover of PDN connections to 3GPP access is triggered, the procedure as per Figure 8.2.1.2-1 before step 18 shall be performed. In step 3 of Figure 8.2.1.2-1 the UE shall provide an APN corresponding to one of the PDN connections that are being transferred from non-3GPP access. The UE shall then repeat step 18 of Figure 8.2.1.2-1 for each of the remaining PDN connections that are being transferred from 3GPP access.

In case of handover to UTRAN/GERAN, the following applies for connectivity to multiple PDNs:

– If the UE is connected to both 3GPP access and non-3GPP access before the handover of PDN connections to 3GPP access is triggered, steps 2 to 6 of Figure 8.2.1.4-1 shall be skipped.

– If the UE is connected only to non-3GPP access before the handover of PDN connections to 3GPP access is triggered, steps 2 to 6 of Figure 8.2.1.4-1 shall be performed.

– The UE shall repeat steps 7 to 16 of Figure 8.2.1.4-1 for each PDN connection that is being transferred from non-3GPP access.

For connectivity to multiple PDNs step 3 of Figure 8.2.6-1 shall be repeated for each PDN connection that is being transferred from non-3GPP access.

NOTE: The procedure applies both for the case where a new Serving GW is selected during attach on 3GPP access or for the case where the Serving GW is not changed.

1) The UE uses a trusted or untrusted non-3GPP access system. PDN connectivity is achieved through concatenated PMIPv6 tunnels between the trusted non-3GPP access or ePDG and the Serving GW, and between the Serving GW and the PDN GW.

2) The handover procedure from trusted or untrusted non-3GPP IP access with PMIPv6 on S2a/S2b to 3GPP access with PMIP-based S5/S8 is performed as described in steps 2‑18 of clause 8.2.1.2 (for E‑UTRAN) and steps 2‑16 of clause 8.2.1.4 (for UTRAN/GERAN).

3) In case a new Serving GW has been selected during the attach on 3GPP access, the PDN GW triggers the bearer release in the non-3GPP access as defined in clause 6.12.3. Otherwise, the Serving GW triggers resource release in the non-3GPP access as defined in steps 2‑5 of clause 6.12.3.