Content for TS 37.340 Word version: 18.2.0

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10.16 Support of inter-system handover involving EN-DC or MR-DC with 5GC 10.16.1 General 10.16.2 Inter-system handover from EPS to 5GS with the Secondary Node used as target 10.16.3 Inter-system handover from 5GS to EPS with the Source Node used as target Secondary Node
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10.16 Support of inter-system handover involving EN-DC or MR-DC with 5GC |R16| p. 103

10.16.1 General p. 103

Inter-system handover is specified in TS 23.501 and TS 23.502. Data forwarding for inter-system handover is specified in TS 38.300, and clause 8.4.

Inter-system Inter-Master node handover with/without SN change is not supported in this version of the protocol (e.g. no transition from EN-DC to NGEN-DC or NR-DC).

Inter-system HO from NR to E-UTRA with EN-DC configuration is supported in this version of the specification. N26 based inter-system HO will be executed between source RAN and gNB.

Inter-system HO from E-UTRA connected to 5GC to E-UTRA with EN-DC configuration is not supported. Inter-system HO from E-UTRA with EPC to MR-DC with 5GC is not supported.

Inter-system handover with source gNB and the target en-gNB or the source en-gNB and the target gNB being realised within the same network entity is supported in this version of the specification as described in clause 10.16.2 and clause 10.16.3.

10.16.2 Inter-system handover from EPS to 5GS with the Secondary Node used as target p. 103

Inter-system handover from EPS to 5GS with the Secondary Node used as target refers to a deployment scenario where the source en-gNB and the target gNB are realised within the same network entity.

Copy of original 3GPP image for 3GPP TS 37.340, Fig. 10.16.2-1: Inter-system handover from EPS to 5GS with the Secondary Node used as target

Figure 10.16.2-1: Inter-system handover from EPS to 5GS with the Secondary Node used as target
(⇒ copy of original 3GPP image)

Step 1: The (source) eNB, performing EN-DC with the (source) en-gNB triggers handover preparation including the SgNB UE X2AP ID within the Source NG-RAN to Target NG-RAN Transparent Container.
Step 2: The target gNB infers from the received SgNB UE X2AP ID in the Handover Request message that direct data forwarding can be performed in a node-internal way.
Step 3: DL UP data is forwarded in a node-internal way for the SN terminated bearers.
Step 4: After the end marker has arrived from the SGW, the (target) gNB processes UP data from the UPF.

10.16.3 Inter-system handover from 5GS to EPS with the Source Node used as target Secondary Node p. 104

Inter-system handover from 5GS to EPS with the Source Node used as target Secondary Node refers to a deployment scenario where the source gNB and the target en-gNB are realised within the same network entity.

Copy of original 3GPP image for 3GPP TS 37.340, Fig. 10.16.3-1: Inter-system handover from 5GS to EPS with the Source Node used as target Secondary Node

Figure 10.16.3-1: Inter-system handover from 5GS to EPS with the Source Node used as target Secondary Node
(⇒ copy of original 3GPP image)

Step 1.

The (source) gNB triggers handover preparation phase including in the Source eNB to Target eNB Transparent Container the Source NG-RAN node ID and the RAN UE NGAP ID.

Step 2.

The target eNB receives the Source NG-RAN node ID and the RAN UE NGAP ID in the Source eNB to Target eNB Transparent Container.

Step 3.-4.

The X2AP SgNB Addition procedure is performed towards the (target) en-gNB indicated in the Source NG-RAN node ID received in step 2. The eNB includes the RAN UE NGAP ID received in step 2 in the X2 SgNB Addition Request message.

Step 5.-8.

Handover proceeds.

Step 9.

DL UP data is forwarded in a node-internal way for the SN terminated bearers.