Question: In a telecom network, which of the following functionalities is exclusively the responsibility of the Home Environment, according to 3GPP service principles?
Option 1: Radio Access and Transport
Option 2: Mobility Management including Roaming
Option 3: Quality of Service (QoS) Negotiation
Option 4: User Authentication and SIM/USIM Issue
Explanation: According to the service principles outlined in 3GPP, the Home Environment is solely responsible for functionalities closely related to user identity and subscription management. Among the provided options, only "User Authentication and SIM/USIM Issue" aligns with these responsibilities, as they are directly tied to verifying user identities and managing subscriber identity modules/cards, respectively. The other options either fall under the Serving Network’s purview (Option 1) or are shared responsibilities that can be managed by either the Home Environment, the Serving Network, or a combination of both (Options 2 and 3).