Do you know why you receive SMS messages even you aren't actively using your phones? This is due to the Network Triggered Service Request. In LTE network, this type of request is made when the network has downlink traffic to deliver to a UE in Idle mode. Here's how it works roughly:
· Missed Delivery: The network (SGW) sends data to the UE, but the UE is unavailable to receive it (e.g., screen off).
· Notification: The base station (eNB) detects the failed delivery and informs the network core (MME) through a Downlink Data Notification message.
· Paging: The MME initiates paging by sending a message to the eNB, instructing it to signal the UE to wake up and check for service requests.
· UE Response: Upon receiving the paging signal, the UE responds with a Service Request message, indicating it's ready to receive data.
· Data Retransmission: The network (SGW) re-sends the original data to the UE now that it's awake and responsive.
You can read detailed technical explanation from 3GPP.
Also don't hesitate to review our related posts on:
· The procedure of UE-Triggered Service Request
· The procedure of paging
