Can a UE camp on certain Frequency/RAT

There is an IE Index to RAT/Frequency Selection Priority within the NGAP: Initial Context Setup Request. This IE is used to define local configuration for RRM strategies such as camp priorities in Idle mode and control of inter-RAT/inter-frequency handover in Active mode (see TS 23.501 [9]).

The purpose of the Initial Context Setup Request procedure is to establish the necessary overall initial UE context at the NGRAN node, when required, including PDU session context, the Security Key, Mobility Restriction List, UE Radio Capability and UE Security Capabilities, etc.