5.31.20 Category M UEs differentiation

This functionality is used by the network to identify traffic to/from Category M UEs, e.g. for charging differentiation.

A Category M UE using E-UTRA shall provide a Category M indication to the NG-RAN during RRC Connection Establishment procedure as defined in TS 36.331 [51].

When the UE has provided a Category M indication to the NG-RAN during RRC Connection Establishment, the NG-RAN shall provide an LTE-M Indication to the AMF in the Initial UE Message (see clause 4.2.2.2.1 of TS 23.502 [3] and TS 38.413 [34]).

When the AMF receives an LTE-M Indication from NG-RAN in an Initial UE Message or from an MME during EPS to 5GS handover, the AMF shall store the LTE-M Indication in the UE context, consider that the RAT type is LTE-M and signal it accordingly to the SMSF during registration procedure for SMS over NAS, to the SMF during PDU Session Establishment or PDU Session Modification procedure. The PCF can also receive the RAT Type as LTE-M, when applicable from the AMF using the PCRT on Access Type change specified in clause 6.1.2.5 of TS 23.503 [45] during AM Policy Association Establishment or AM Policy Association Modification procedure and from the SMF using the PCRT on Access Type change specified in clause 6.1.3.5 of TS 23.503 [45] during SM Policy Association Establishment or SM Policy Association Modification procedure.

The NFs generating CDRs shall include the LTE-M RAT type in their CDRs.

Upon AMF change or inter-system mobility from 5GS to EPS, the source AMF shall provide the "LTE-M Indication" to the target AMF or MME as part of the UE context.

During EPS to 5GS Mobility Registration Procedure, the AMF shall disregard any "LTE-M Indication" received from the MME in the UE context (see TS 23.401 [26]) and take into account the "LTE-M Indication" received from NG-RAN, as specified above.