Service Request — UE triggered

UE Wakes Up for Uplink Data

When an idle or inactive UE has uplink data to send, it initiates a Service Request procedure to restore the connection. The UE establishes an RRC connection with the nearest gNB and sends the Service Request NAS message. The AMF verifies the NAS security context, then coordinates with the SMF to reactivate the user plane by updating the PFCP rules at the UPF and establishing the GTP-U tunnel between the gNB and UPF. This is the reverse of paging — UE-initiated rather than network-initiated.