In TR 23.761
, the MUSIM device considers sending a paging cause part of the [Uu] paging message. The [Uu] paging message contains the identity of UE plus a Paging Cause, i.e., indicating the type of traffic that triggered the paging, e.g., MT Voice. 3G already used to have this paging cause as paging traffic type (Conversational, Streaming, Interactive, Background). In EPS, the paging traffic type was removed. MUSIM system applies to EPS and 5GS. Based on the paging cause, UE makes educated decisions on whether to respond to the other system's paging. The interim conclusion in TR 23.761
is to have only one 'paging cause' value for the voice service. However, UE needs to discriminate the case where the absence of Paging Cause in the Uu Paging message is due to a non-voice MT service from the case where the absence of Paging Cause in the Uu Paging message is due to a legacy RAN node (i.e., regardless whether the MT service is voice or not).
No security threats adressed in the present document.
No Security requirements adressed in the present document.