This use case is intended to illustrate that the new Priority Service + eMLPP functionality fulfils the Priority Service requirements.
Use case 1:
Two Service Users (Priority Service subscribers), each with an assigned Priority Service priority level in the range of Priority Service1 - Priority Service5, belong to two different new networks (A and D) supporting both Priority Service and eMLPP or Priority Service only.
The Service User roam to two different new networks (the Priority Service subscriber in network A roams to network B and the Priority Service subscriber in network D roams to network C) supporting both Priority Service and eMLPP.
The Service User who roamed from network A to network B sets up a Priority Service priority call towards the Service User who roamed from network D to network C.
The call is routed via an intermediate non-3GPP network.
In this use case, the call receives Priority Service treatment (priority access to traffic channels) on the terminating side in (C) according to the Priority Service level Priority Service1 - Priority Service5 as assigned to the Service User calling from (B). Since the end-to-end Priority Service is based on the Priority Service subscription of the calling party, this use case also applies to a called party without Priority Service subscription.
Priority Service calls should not be pre-empted by eMLPP calls.