Question: When a UE receives a mobile terminating call with a category of alerting not defined in the SIM/USIM, how should the UE behave according to specifications?
Option 1: The UE shall ignore the call and not alert the user.
Option 2: The UE shall use an alert associated with the last received category.
Option 3: The UE shall prompt the user to define a new association for the unknown category.
Option 4: The UE shall act as if it was not supporting the feature, using a default alert for that type of mobile terminating traffic.
Explanation: When a UE receives a call with an undefined alerting category in the SIM/USIM, it should use default settings defined in the ME for that type of mobile terminated traffic, implying the use of a default alert as if the feature was not supported, to still notify the user.