Question: In the context of cell re-selection in a UTRA FDD/E-UTRA FDD network, what marks the end of the cell re-selection delay?
Option 1: Completion of the RRC CONNECTION REQUEST message transmission on Cell 2's dedicated channel.
Option 2: Receipt of the first response from Cell 2 after sending the RRC CONNECTION REQUEST.
Option 3: Successful handover to Cell 2 with all ongoing calls maintained.
Option 4: The moment the UE starts sending preambles on the PRACH for the RRC CONNECTION REQUEST message to perform a Tracking Area Update procedure on Cell 2.
Explanation: This option correctly identifies the end of the cell re-selection delay as per the given context. It is specifically the point when the UE initiates communication with Cell 2 by sending preambles for an RRC CONNECTION REQUEST, which is a crucial step in the Tracking Area Update procedure after cell re-selection. The other options either refer to later stages in the connection establishment (Options 1 and 2) or a different procedure altogether (Option 3).