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