Service Request — Network triggered

Network Wakes Up UE for Downlink

When downlink data arrives at the UPF for a UE in IDLE state, the network must first page the UE and then process its Service Request to restore the user plane. The UPF buffers the incoming data while the paging chain executes. The UPF notifies the SMF about the pending data, the SMF triggers paging via the AMF, the AMF pages all gNBs in the UE's TAI list, and the UE wakes up at its paging occasion to receive the notification.