5.4.4.2a UE Radio Capability Match Request

If the AMF requires more information on the UE radio capabilities support to be able to set the IMS voice over PS Session Supported Indication (see clause 5.16.3), then the AMF may send a UE Radio Capability Match Request message to the NG-RAN. This procedure is typically used during the Registration Procedure or when AMF has not received the Voice Support Match Indicator (as part of the 5GMM Context).

NOTE: During the Registration Procedure, if the AMF does not already have the UEs radio capabilities and if the RAT where the UE is requires the establishment of AN security context prior to retrieval of radio capabilities, the AMF needs to initiate "Initial Context Setup" procedure as defined in TS 38.413 [34] to provide the 5G-AN with security context, before sending a UE Radio Capability Match Request message.