Question: Which interface(s) are used for transferring NB-IoT RRC messages between network nodes in the context of Evolved Universal Terrestrial Radio Access (E-UTRA)?
Option 1: X2-interface and S1-interface
Option 2: Only the S1-interface for all network nodes
Option 3: Solely the X2-interface, with S1-interface for specific cases
Option 4: Neither X2 nor S1; a dedicated NB-IoT interface is utilized
Explanation: Both the X2-interface (for direct eNB communication) and the S1-interface (connecting eNB to the Evolved Packet Core, EPC) are used for transferring NB-IoT RRC messages, facilitating efficient cross-node communication within E-UTRA and seamless NB-IoT service integration.