Content for TS 23.435 Word version: 19.3.0

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9.13 Predictive slice modification in Inter-PLMN based slice service continuity 9.13.1 General 9.13.2 Procedure 9.13.3 Information flows 9.13.4 APIs 9.13.4.1 General 9.13.4.2 SS_NSCE_Inter-PLMN_Continuity API 9.13.4.3 SS_NSCE_Inter-PLMN_slice modification notify API
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9.13 Predictive slice modification in Inter-PLMN based slice service continuity p. 91

9.13.1 General p. 91

This feature applies to the specific deployment where NSCE service provider provides its services when connected to two PLMNs and has SLA with them (i.e. deployment shown in TS 23.434 Figure 8.2.2-2). In this feature, the NSCE server initially receives an expected/predicted UE location/mobility change request outside a PLMN1 slice service area for one or more UEs within the VAL application session (e.g. such session can be a V2X session). Then, the NSCE server checks with 5GS (OAM, 5GC) whether the serving slice is available and can offer the same performance at the target PLMN. The NSCE server evaluates the need for a slice modification (e.g. a slice lifecycle related trigger change). Based on this decision/recommendation, it provides the action to the OAM of PLMN2 proactively, before UE mobility happens.

9.13.2 Procedure p. 91

In the procedure shown in Figure 9.13.2-1, a mechanism is provided to allow for slice modification when a vertical application of single or group of VAL UEs migrates (or is expected/predicted to migrate) to a different PLMN supported by the same NSCE server.

Pre-conditions:

Enterprise hosting the VAL server has SLA for slice services with NSCE service provider.
The VAL server has subscribed to the network slice capability enablement server managing slice services from PLMN1 and PLMN2.
The VAL client of VAL UE is mapped to Slice#1, and NSCE client of VAL UE has established a connection to PLMN1.
The NSCE server is connected to 5GS of PLMN1 and PLMN2.
The VAL server is subscribed to and received mobility predictions of UE location change (according to clause 6.7.2.3 of TS 23.288) from PLMN1 and/or PLMN2 in advance before the actual event. The VAL server correlated received mobility predictions and determined PLMN change.

Reproduction of 3GPP TS 23.435, Fig. 9.13.2-1: Predictive Inter-PLMN slice service continuity

Figure 9.13.2-1: Predictive Inter-PLMN slice service continuity

Step 1.

The VAL server sends to NSCE server an Inter-PLMN application service continuity requirement request due to predicted/expected UE or group UE mobility from source service area of slice1 in PLMN1 to a target service area covered by a different slice service area in slice#2/PLMN2.

Step 2.

NSCE server sends an Inter-PLMN application service continuity requirement response to the VAL server as positive or negative acknowledgement depending on its capability to provide such service serving both areas/slices in both PLMNs and available resources.

Step 3.

NSCE server determines to query the underlying 5G system on the slice availability and conditions at the target service area/slice2/PLMN2 (based on step 1 requirement). Such query may be in form of a request/response and include:

NSCE server interacting with 5GS/PLMN2 to query the UEs specific information (location, UEs connection capabilities) as well as network conditions, slice related analytics (from NWDAF as specified in TS 23.288).
NSCE server may also interact with 5GS/PLMN2 to query on the target slice availability and the up-to-date configured slice parameters e.g. slice RRM policies, modification of the NSI/NSSI resources (see clause 5.1.12 of TS 28.531) at the target service area and measurements for the slice at the target area.

Step 4.

NSCE server determines the need for a slice lifecycle change at the slice target area and translates this to a trigger action. This trigger action can be based on the outcome of step 3 and can be a requested slice modification (slice2/PLMN2) or creation/instantiation of new slice at the target area (this may happen if a group of UEs are moving to the target area and the requested slice2 is missing in the target area).

Step 5.

The NSCE server may send the trigger action as a slice modification trigger request to the slice provisioning MnS producer at OAM/PLMN2 (e.g. slice modification for network slice) to extend slice availability to the target service area based on the expected/predicted VAL UE or VAL group mobility. As response to the trigger action, the provisioning MnS producer provides a slice modification trigger response with a positive or negative result.

Step 6.

After the slice lifecycle change execution (based on the indication in step 5), the NSCE server sends a notification to the VAL server and optionally to the VAL client containing the positive or negative result from step5.

Step 7.

If big number of UEs is migrating from PLMN1 to PLMN2, there might be a need to further modify/reduce the respective slice resources of PLMN1. NSCE sends trigger request to the slice provisioning MnS producer at OAM/PLMN1 (e.g. slice modification for network slice) to decrease slice availability to the source area after the UEs have migrated.

9.13.3 Information flows p. 93

9.13.3.1 General p. 93

The following information flows are specified for predictive inter-PLMN slice service continuity:

Inter-PLMN application service continuity requirement,
Slice modification notification.

9.13.3.2 Inter-PLMN application service continuity requirement request p. 93

Table 9.13.3.2-1 and Table 9.13.3.2-2 describe information elements inter-PLMN application service continuity requirement request and response between the VAL server and the NSCE server.

Table 9.13.3.2-1: Inter-PLMN application service continuity requirement request

Information element	Status	Description
VAL server ID	M	The identifier of the VAL server.
Security credentials	M	Security credentials resulting from a successful authorization.
VAL service ID	M	The identifier of the VAL service for which the requirement request applies.
VAL UE ID list	O	The list of VAL UE IDs for which the requirement request applies.
Service Continuity Requirement	M	The service continuity requirement which can be the expected or predicted migration of the VAL application or a list of VAL UEs within the application to a target area.
Target PLMN ID	M	PLMN identifier of the target PLMN.
Slice identifier	O (see NOTE)	The slice identifier (S-NSSAI, NSI ID or ENSI) which is mapped to the VAL application, if known by the VAL server.
Target Service Area	O	The target area can be represented as the geographical coordinates / set of waypoints outside the original service area, where the VAL application/ UE(s) is expected or predicted to move.
Application QoS requirements	O	The QoS requirements / KPIs for the VAL service.
NOTE: Slice info can be available based on SLA between VAL service provider and network operator.

Table 9.13.3.2-2: Inter-PLMN application service continuity requirement response

Information element	Status	Description
Result	M	The result of the request (positive or negative acknowledgement).

9.13.3.3 Inter-PLMN slice modification notify p. 94

Table 9.13.3.3-1 describes information elements for the inter-PLMN slice modification notify message from the NSCE server to the VAL server or the VAL client (via NSCE client).

Table 9.13.3.3-1: Inter-PLMN slice modification notify

Information element	Status	Description
VAL service ID	M	The identifier of the VAL application which is impacted by the slice modification.
VAL UE ID list	O	The identifiers of the VAL UEs which are impacted by the slice modification.
Slice identifier	M	The slice identifier (S-NSSAI, NSI ID or ENSI) which is used and/or modified to extend slice availability to the target service area.
PLMN ID	M	PLMN identifier of the PLMN where modification was performed.
Target Service Area	M	The target area, can be represented as the geographical coordinates / set of waypoints outside the original service area, for which the modification applies.

9.13.4 APIs p. 94

9.13.4.1 General p. 94

Table 9.13.4.1-1 illustrates the API for inter-PLMN application service continuity exposure.

Table 9.13.4.1-1: Inter-PLMN application service continuity requirement

API Name	API Operations	Operation Semantics	Consumer(s)
SS_NSCE_InterPLMN_Continuity	Inter-PLMN_Continuity_Requirement	Request /Response	VAL server
SS_NSCE_InterPLMN_Slice_Modification_Notify	Inter-PLMN_Slice_Modification_Notify	Notify	VAL server or VAL client

9.13.4.2 SS_NSCE_Inter-PLMN_Continuity API p. 95

API operation name:

Inter-PLMN_Continuity_Requirement

Description:

The consumer requests to have inter-PLMN slice service continuity

Known Consumers:

VAL server.

Inputs:

See Table 9.13.3.2-1.

Outputs:

See Table 9.13.3.2-2.

See clause 9.13.2 for details of usage of this operation.

9.13.4.3 SS_NSCE_Inter-PLMN_slice modification notify API p. 95

API operation name:

Inter-PLMN_Slice_Modification_Notify