Question: In the context of cell re-selection in a telecommunications network, what event marks the end of the cell re-selection delay for a User Equipment (UE) transitioning to Cell 2 (E-UTRA)?
Option 1: Completion of the Tracking Area Update procedure on Cell 2
Option 2: Receipt of the first response from Cell 2 on the Physical Downlink Shared Channel (PDSCH)
Option 3: Moment when the UE starts sending preambles on the Physical Random Access Channel (PRACH) for an RRC CONNECTION REQUEST message to perform a Tracking Area Update procedure
Option 4: End of the T2 time period without initiating any communication with Cell 2
Explanation: The correct answer is Option 3 because, according to the definition provided, the cell re-selection delay ends when the UE begins sending preambles on the PRACH for the purpose of sending an RRC CONNECTION REQUEST message. This action initiates the Tracking Area Update procedure on Cell 2 (E-UTRA), marking the transition’s key milestone from the perspective of cell re-selection timing. This highlights the importance of PRACH access in establishing communication with a new cell during handover scenarios, impacting network efficiency and user experience.