Question: In a 5G system, when a User Equipment (UE) is in CONNECTED mode on a Visited Public Land Mobile Network (VPLMN) and engaged in a priority service, what can the Home Public Land Mobile Network (HPLMN) control regarding the UE's mode transition?
Option 1: The HPLMN can immediately force the UE to enter IDLE mode regardless of the ongoing communication type.
Option 2: The HPLMN can control the timing of when the UE enters IDLE mode and initiates higher priority PLMN selection, based on the type of ongoing communication.
Option 3: The HPLMN has no control over the UE's mode transition in this scenario, as it is governed by VPLMN policies.
Option 4: The HPLMN can only suggest a mode transition to the UE, which then decides based on its current activity.
Explanation: This option correctly reflects the requirement that the 5G system must support a mechanism for the HPLMN to control the timing of when a UE (in automatic mode and CONNECTED on a VPLMN) enters IDLE mode and initiates higher priority PLMN selection, taking into account the type of ongoing communication. This ensures that critical services are not interrupted unnecessarily.