Question: What is the implication for a User Equipment (UE) when an Integrity Service Alert is issued with a 'Do Not Use' (DNU) flag set to false in NG-RAN?
Option 1: The UE must discard all previously received assistance data for integrity computation.
Option 2: The UE is prohibited from using the corresponding assistance data for any positioning method.
Option 3: The UE may utilize the corresponding assistance data for computing integrity, but only until the specified epoch time expires.
Option 4: The UE will automatically switch to a different positioning technique that doesn't require assistance data.
Explanation: When an Integrity Service Alert is issued with the DNU flag set to false, it indicates that the provided assistance data is suitable for integrity computation at the time of the alert. However, since the DNU flags are defined to be applicable only to the specified epoch time, the UE's permission to use this data for integrity purposes is time-limited, expiring at the end of the specified epoch. This requires the UE to be aware of and adhere to these temporal constraints when utilizing the assistance data for integrity calculations.