Question: In UTRAN Iu interface RANAP signalling, what is the primary purpose of the Correlation ID Information Element (IE) in relation to user plane transport between RNC and L-GW?
Option 1: To establish a new Radio Access Bearer (RAB) for voice services
Option 2: To manage handover procedures between different RNCs
Option 3: To authenticate User Equipment (UE) before granting access
Option 4: To specify the GTP Tunnel Endpoint Identifier or GRE key for user plane transport
Explanation: The correct answer is Option 4 because, according to the context of RANAP signalling over the Iu interface in UTRAN, the Correlation ID IE is specifically utilized to convey either the GTP (GPRS Tunneling Protocol) Tunnel Endpoint Identifier or the GRE (Generic Routing Encapsulation) key. This information is crucial for correctly routing and managing user plane data between the Radio Network Controller (RNC) and the Logical Gateway (L-GW), ensuring seamless communication as outlined in standards related to Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access for GPRS enhancements.