Question: What is the purpose of a guard period created by a Narrowband Internet of Things (NB-IoT) User Equipment (UE) in Time Division Duplexing (TDD) operation for frame structure type 2?
Option 1: To allow the UE to receive the first part of the first Orthogonal Frequency Division Multiplexing (OFDM) symbol of a downlink subframe immediately following an uplink subframe.
Option 2: To enable the UE to transmit the first part of the first OFDM symbol of an uplink subframe immediately following a downlink subframe.
Option 3: To permit the UE to operate in Frequency Division Duplexing (FDD) mode.
Option 4: To prevent the UE from receiving the first part of the first OFDM symbol of a downlink subframe immediately following an uplink subframe, for 15-kHz subcarrier spacing on an NB-IoT carrier.
Explanation: The guard period is created by the UE to avoid interference between uplink and downlink transmissions in TDD operation. By not receiving the first part of the first OFDM symbol of a downlink subframe immediately following an uplink subframe, the UE ensures that there is a sufficient gap between the two transmissions, thereby preventing interference and ensuring reliable communication.