5G Paging procedure

Reaching an Idle UE

When the network has downlink data for a UE that is in IDLE or INACTIVE state, it must page the UE to wake it up. The process starts when data arrives at the UPF for an idle subscriber. The UPF sends a data notification to the SMF, which forwards a paging trigger to the AMF via N1N2 Transfer. The AMF then sends N2 Paging messages to all gNBs in the UE's registration area (the TAI list assigned during registration). Each gNB broadcasts the paging message at the UE's specific paging occasion.