Question: When is the Negotiated DRX parameter in NB-S1 mode Information Element (IE) included by the network?
Option 1: Always, regardless of the User Equipment's (UE) Tracking Area Update Request message.
Option 2: Only when the UE has not included the DRX parameter in NB-S1 mode IE in the Tracking Area Update Request message.
Option 3: When the UE has included the DRX parameter in NB-S1 mode IE in the Tracking Area Update Request message.
Option 4: Never, as it is not a mandatory IE.
Explanation: The network includes the Negotiated DRX parameter in NB-S1 mode IE in response to the UE's Tracking Area Update Request message that contains the DRX parameter in NB-S1 mode IE. This ensures that both the network and the UE have agreed upon the DRX parameters, enabling efficient power saving mechanisms in the Evolved Packet System (EPS).