Question: What is the primary purpose of the "Permanent NAS UE Identity" element in UTRAN, as utilized by the Radio Network Controller (RNC)?
Option 1: To establish a new RRC connection for incoming voice calls.
Option 2: To authenticate User Equipment (UE) for data transmission over the Iu interface.
Option 3: To differentiate between multiple User Equipments (UEs) connected to the same Cell ID.
Option 4: To identify and associate existing signalling connections (e.g., RRC or Iu signalling) of the same UE.
Explanation: The correct answer, Option 4, highlights the element's role in identifying a UE across different signalling connections within the UTRAN, enabling the RNC to manage multiple connections of the same UE efficiently. This is crucial for seamless network operation and resource allocation. The other options, while related to UTRAN operations, do not accurately describe the primary purpose of the "Permanent NAS UE Identity" element as specified. **IMSI (International Mobile Subscriber Identity)**, mentioned in the context, serves this identification purpose.