Question: In a scenario where a User Equipment (UE) camps on a 7.68 Mcps TDD cell and then reselects to an FDD cell, what event marks the end of the cell re-selection delay?
Option 1: The moment the UE starts sending preambles on the Physical Random Access Channel (PRACH) for a CONNECTION REQUEST message.
Option 2: When the UE completes the Location Registration on the new FDD cell.
Option 3: Immediately after the UE decides to reselect based on changed cell quality levels.
Option 4: When the UE stops transmitting on the original TDD cell.
Explanation: The cell re-selection delay is defined by the time it takes for a change in cell quality levels to trigger the UE to not only decide to reselect a better-ranked cell but also to take action towards establishing a new connection. This action is specifically marked by the UE starting to send preambles on the PRACH as part of initiating a CONNECTION REQUEST message for Location Registration on the newly selected FDD cell, making Option 1 the correct endpoint of this delay.