Question: What is the primary purpose of the 'HS-DSCH FDD Secondary Serving Information To Modify Unsynchronised' IE in UTRAN's Iub interface NBAP signalling?
Option 1: To initialize a new Radio Link Setup for a User Equipment (UE) handover.
Option 2: To release existing radio resources for an idle UE.
Option 3: To modify Secondary Serving HS-DSCH information during an Unsynchronised Radio Link Reconfiguration procedure in a Node B Communication Context.
Option 4: To report UE measurement reports to the RNC for load balancing.
Explanation: This option correctly identifies the purpose of the 'HS-DSCH FDD Secondary Serving Information To Modify Unsynchronised' IE, which is to modify existing Secondary Serving HS-DSCH configurations without requiring synchronization, specifically within the context of a Node B's communication setup undergoing radio link reconfiguration. This aligns with efficient management of high-speed downlink shared channel (HS-DSCH) resources in UTRAN networks.