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Content for  TR 22.835  Word version:  18.0.0

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5.4  Use of Multi-RATs for network slicesWord‑p. 16

5.4.1  Description

5GC is connected to NG-RAN and the NG-RAN supports both E-UTRA and NR. However, for a third party who wants to utilize a network slice, the different potential and flexibility of E-UTRA and NR is not something that can easily be disregarded.
Also, the unequal possibility of radio resource slicing for NR and E-UTRA leads to a unique use case scenario.

5.4.2  Pre-conditions

Figure 5.4.2-1 shows the use case scenario where an NG-RAN is supporting both NR and E-UTRA radio resources.
(not reproduced yet)
Figure 5.4.2-1: Initial condition
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In this Figure, it is assumed that
  • Subscription:
    • UE A1 and A4 are subscribed to a service using Slice M.
    • UE A2 and A4 are subscribed to a service using Slice N.
    • UE A3 is subscribed to a service using Slice O.
  • Deployment:
    • E-UTRA is configured to serve Slice M, e.g. for general eMBB services, including a slice for IMS service.
    • NR is configured to serve Slice N and O, e.g. for URLLC or V2X. Due to demanding requirements of V2X application, V2X application providers (e.g. OEM) requests to use only NR for Slice O.
The frequencies used for E-UTRA and NR can be the same or different. For example, when DSS (Dynamic Spectrum Sharing) is used, the same frequency is used for both E-UTRA and NR, but in different time slots.
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5.4.3  Service Flows

The following is an example service flow based on the setting in the previous section:
  • After power-on, UE A1, A2, A3 and A4 start searching for cells.
  • UE A1, A2, A3 and A4 start registration in the found cells.
  • Depending on factors such as e.g., use of Dual Connectivity, priorities of network slices, different UEs may camp on different RATs. For example, the UE A1 may camp on E-UTRA.
  • Based on the various inputs, for the transport of user traffic for a network slice, the RAT and radio resources can be configured. For example, when user traffic for slice M is generated for UE A4, the network may configure E-UTRAs resource for the UE to deliver the traffic. For this UE A4, when user traffic for slice N is generated, the network may configure NR resources for the UE. When both NR and E-UTRA resource are configured, the user traffic for the network slice only flows over the allowed RATs.
  • When service policy changes, e.g. when slice M is now set to use NR instead of E-UTRA, UEs camp NR cells instead of E-UTRA cells. For a UE with ongoing active communication, handover occurs to move the UE from E-UTRA to NR.
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5.4.4  Post-conditionsWord‑p. 17
The following Figure 5.4.4-1 shows the status at the end of the service flow. For the transport of user traffic, UE A1 is served by E-UTRA, UE A2 and A3 are served by NR. UE A4 may camp on either E-UTRA or NR during Idle mode and be configured with E-UTRA, NR or both depending on the active application during Connected mode.
(not reproduced yet)
Figure 5.4.4-1: End result
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5.4.5  Existing features partly or fully covering the use case functionality

TS 22.261 contains many requirements related to user traffic management and network slices.
  • The 5G system shall allow the operator to define and update the set of services and capabilities supported in a network slice.
  • Based on operator policy, a 5G network shall provide suitable APIs to allow a trusted third-party to create, modify, and delete network slices used for the third-party.
  • Based on operator policy, the 5G network shall provide suitable APIs to allow a trusted third-party to define and update the set of services and capabilities supported in a network slice used for the third-party
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5.4.6  Potential New Requirements needed to support the use case

The following new requirements can be derived from this use case:
[PR.5.4.6-1]
5G system shall minimize signaling exchange and service interruption when there is a change in the allowed radio resources (e.g. RATs) for a network slice.

5.5  Use case on access to slices when roamingWord‑p. 18

5.5.1  Description

A UE subscribes to multiple network slices from its home operator. The home operator has agreements with various other operators to support the same slices for roaming UEs. In this case, the most preferred VPLMN in a specific area does not support all the needed slice; however, a second VPLMN does support the slice not available in the most preferred VPLMN. In this case, the home operator can provide the necessary information to allow the UE to use the second VPLMN to obtain the service available on that network slice, while otherwise being served by the most preferred VPLMN. Figure 5.5.1-1 illustrates the scenario.
(not reproduced yet)
Figure 5.5.1-1: Roaming UE with subscriptions to services on network slices available on different networks
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5.5.2  Pre-conditions

In this scenario, the UE A1 is roaming in an area covered by 2 VPLMNs, Network A and Network B. UE A1 subscribes to services that require use of slices M and N in its home network. The corresponding slices and services are available in the visited area, even though these slices are not offered by the same network in the visited area. Network A is the most preferred VPLMN in this area.

5.5.3  Service Flows

When UE A1 first enters the visited area, it registers with Network A and can uses services from slice N.
At a later time (T2), the user decides to activate a service that needs slice M. The UE, detecting that slice M is not available on Network A, looks for the network that provides the slice. The UE registers on Network B and the user is able to use the service of slice M.
When the service concludes and slice M is no longer needed (T3), the UE returns to Network A.

5.5.4  Post-conditions

The user is able to access all their subscribed services while roaming, even though the needed slices are not available on a single VPLMN.

5.5.5  Existing features partly or fully covering the use case functionality

Roaming and slice access work as usual, with the addition of being able to change VPLMNs to gain access to a slice not available on the most preferred VPLMN.

5.5.6  Potential New Requirements needed to support the use caseWord‑p. 19
[PR.5.5.6-1]
For a roaming UE activating a service/application requiring a network slice not offered by the serving network but available in the area from other network(s), the HPLMN shall be able to provide the UE with prioritization information of the VPLMNs with which the UE may register for the network slice.

5.6  Use case on simultaneous access to multiple slices on different VPLMNs

5.6.1  Description

A UE has access to multiple network slices when on the HPLMN. When the UE is roaming and the VPLMN where the UE is currently registered only provides a subset of the network slices that the UE needs to use, the UE can connect to other VPLMNs at the same time to access the other subscribed network slices.

5.6.2  Pre-conditions

  • UE is subscriber of Operator Toffee
  • When on its home network, Operator Toffee, UE has access to three network slices: (A)pricot, (B)anana and (C)herry
  • UE runs different applications that require the UE to simultaneously access Apricot, Banana and Cherry slices
  • Operator Toffee has agreements with:
    • Operator Chocolate to support Apricot and Banana slices
    • Operator Fudge to support Cherry slice
  • Operator Chocolate is the preferred roaming network
  • UE moves out of Operator Toffee's coverage area, into an area where the coverage is provided by Operator Chocolate and Operator Fudge
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5.6.3  Service Flows

  1. UE connects with Operator Chocolate, and has access to Apricot and Banana slices
  2. UE requires simultaneous access to all three slices, Apricot, Banana and Cherry, due to the different applications running on the UE. However, the VPLMN the UE is registered to, Operator Chocolate, does not provide support for Cherry slice
  3. UE is authorised by the HPLMN to additionally access the Cherry slice in the Operator Fudge network.
  4. UE performs PLMN selection and connects to Operator Fudge, while retaining the connection to Operator Chocolate
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5.6.4  Post-conditions

Roaming UE is able to access all three network slices simultaneously from Operator Chocolate and Operator Fudge.

5.6.5  Existing features partly or fully covering the use case functionality

There are related requirements in TS 22.261, clause 6.18 on "Multi-network connectivity and service delivery across operators":
The 5G system shall enable users to obtain services from more than one network simultaneously on an on-demand basis.
For a user with a single operator subscription, the use of multiple serving networks operated by different operators shall be under the control of the home operator.

5.6.6  Potential New Requirements needed to support the use caseWord‑p. 20
[PR.5.6.6-1]
The 5G system shall enable a roaming UE with a single PLMN subscription to access network slices from more than one VPLMN simultaneously, when the UE requires simultaneous access to multiple network slices and the network slices are not available in a single VPLMN.
[PR.5.6.6-2]
The HPLMN shall be able to authorise a roaming UE with a single PLMN subscription to access network slices from more than one VPLMN simultaneously.
[PR.5.6.6-3]
The HPLMN shall be able to provide a UE with permission and prioritisation information of the VPLMNs the UE is authorised to use for accessing specific network slices.
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5.7  Slice Access with Application Preference

5.7.1  Description

This use case intends to bring a use case for network slice to support important applications like gaming and online video in a more flexible and efficient way. For gaming or online video applications, the end users, who have subscription with MNOs who may provide multiple network slices to different users or services, may still have different priority or membership e.g. VIP maintained by 3rd party Service Provider (SP). And depending on the priority or membership information from 3rd party SP perspective, based on the agreement between SP and MNO, the UE have different priority for the available network slices.
Figure 5.7.1-1 shows an example scenario for this use case.
(not reproduced yet)
Figure 5.7.1-1: Example scenario for this use case
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5.7.2  Pre-conditionsWord‑p. 21
  1. MNO provisioned network slices Slice#1, Slice#2, Slice#3. As an example, Slice#1 is dedicated for online video services for SP#1. Slice#2 is dedicated for gaming for SP#2. Slice#3 is a network slice for eMBB service i.e. text or voice chat, file downloading or web surfing.
  2. UE 1 and UE 2 are registered to MNO's 5G network and they have subscription to slice#1, #2 and #3. The owner of UE 1, i.e., User A, have installed Game App x and Video App y. The owner of UE 2, i.e., User B, have installed Game App z and Video App y.
  3. User A and User B are high priority users for SP#1 and SP#2 which means when these users start to use game or video app, they can use the corresponding network slice to guarantee their QoS compared with other users with lower priority and the MNO network resource can accommodate high priority users.
  4. Due to the fact that the 3rd party SP may roll out new services/applications and the users may change their VIP membership dynamically, the 3rd party needs to negotiate the priority of a network slice for UE per application.
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5.7.3  Service Flows

  1. MNO and SP have agreements e.g. SLA and Slice#1, Slice#2 and Slice#3 are provisioned.
    1. The MNO provisioned the slices and maintains the user subscription to access these slices. The SP maintains the application related user membership information.
    2. UE 1 and UE 2 may or may not be accessing three slices simultaneously.
  2. User A's smart phone UE 1, and User B's smart phone UE 2 turns on and registered to MNO network. After registration, UE 1 and UE 2 are able to access corresponding network slices.
    1. User A can access Slice#1 for online video app x and Slice#2 for gaming, also Slice#3 for other services.
    2. User B can access Slice#1 for online video y and gaming app z, and also Slice#3 for other services.
  3. User A and User B started chat and web surfing service, it accesses network Slice#3
  4. User A started online video, UE A access to Slice#3 which can only provide a basic SLA for the online video e.g. with lower resolution1.
  5. User A's priority for slices is dynamically changed due to the SP side updates e.g. User A changes his/her VIP. membership, thus different SLA is provided to User A's online video via Slice#1..
  6. User B started game app, UE B access to Slice #3 which can only provide a basic SLA for the game service e.g. with lower resolution and low latency is not ensured.
  7. User B's priority for slices is dynamically changed due to the SP side updates e.g. User B changes his/her VIP membership, thus different SLA is provided to User A's game app via Slice#2.
  8. User A's priority for slices are changed back to original value due the SP side update e.g. VIP membership. expired, thus the online video is provided via Slice#3.
  9. User B's priority for slices are changed back to original value due to SP side update e.g. VIP membership expired, thus the game app is provided via Slice#3.
In the above service flows, the different slices may be provided by same or different frequency and the coverage may be different. If different slices are deployed in different frequency bands, access of different network slices due to application should not cause degradation of user experiences.
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5.7.4  Post-conditions

SP and MNO may monitor the QoS of online video and game applications and also support flexible charging for these users which change their priority accessed slices per application.

5.7.5  Existing features partly or fully covering the use case functionalityWord‑p. 22
In Clause 6.1.2 of TS 22.261, network slicing requirements are specified including general, management, network slice constraints and cross-network slice coordination.
In clause 6.1.2.2 of TS 22.261, there is a requirement as follows:
The 5G system shall enable the network operator to define a priority order between different network slices in case multiple network slices compete for resources on the same network.
This requirement enables priority mechanism from network resource configuration perspective.
In clause 6.1.2.2 of TS 22.261, there is another requirement as follows:
The 5G system shall allow the operator to assign a UE to a network slice, to move a UE from one network slice to another, and to remove a UE from a network slice based on subscription, UE capabilities, the access technology being used by the UE, operator's policies and services provided by the network slice.
This requirement is from operator perspective and doesn't cover the aspect whether 3rd party application can influent the priority of network slices.
The existing requirements for network slicing, e.g. which is cited in this section, is from network resource configuration perspective.
However, when UE can access multiple network slices which may be tailored for different applications, there is no support of changing the priority or the preferred network slicing for the UE based on application. And this process cannot be carried out efficiently without standard-based means for MNO and third party to communicate/negotiate the preferred network slices according to application.
For this use case, additional two requirements below are considered already supported:
  • The 5G system shall support means to dynamically change the UE priority of network slices per application with minimized interruption, according to third party's policy.
  • The 5G system shall support mechanisms to allow a 3rd party and the 5G network to negotiate the UE priority of a network slice per application.
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5.7.6  Potential New Requirements needed to support the use case


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