5.3.18 Restriction on use of enhanced coverage

In order to deal with use of extensive resources from the network, the operator may prevent specific subscribers from using enhanced coverage (see 3GPP TS 23.501 [8]). When in NB-N1 mode, the UE shall indicate support for restriction on use of enhanced coverage. When in WB-N1 mode, the UE supporting either CE mode A or CE mode B shall indicate support for restriction on use of enhanced coverage. The UE supporting restriction on use of enhanced coverage indicates its support for restriction on use of enhanced coverage in the REGISTRATION REQUEST message. If the UE supports restriction on use of enhanced coverage, the AMF indicates in the REGISTRATION ACCEPT message (see clause 5.5.1.2 and clause 5.5.1.3) that:

• when in WB-N1 mode, whether CE mode B is restricted for the UE, or both CE mode A and CE mode B are restricted for the UE, or both CE mode A and CE mode B are not restricted for the UE; or
• when in NB-N1 mode, whether the use of enhanced coverage is restricted or not for the UE.

If:

• the use of enhanced coverage is restricted;
• the use of CE mode B is restricted; or
• the use of CE mode A and CE mode B is restricted,

the UE shall not use enhanced coverage in the registered PLMN and in any PLMN which is in the list of equivalent PLMNs.

If the UE supports CE mode B and the network determines that

• the use of enhanced coverage is not restricted for the UE; or
• CE mode B is not restricted for the UE,

the applicable NAS timer values shall be calculated by the network as described in clause 4.19 and clause 4.20.

For a UE that supports restriction on use of enhanced coverage or CE mode B, if:

• the AMF determines to enforce a change in restriction on the use of enhanced coverage or a change in the restriction on the use of CE mode B as described in 3GPP TS 23.501 [8]; and
• the UE is in 5GMM-CONNECTED mode and there is no ongoing registration procedure,

the AMF shall initiate the generic UE configuration update procedure to indicate registration requested and release of the N1 NAS signalling connection not requested as described in clause 5.4.4. After the successful completion of the registration procedure for mobility registration update including change of the restriction on the use of enhanced coverage, for any SMF with which the UE has an established PDU session, the AMF updates the SMF with the indication on the use of extended NAS timer setting as described in 3GPP TS 23.501 [8] and 3GPP TS 23.502 [9].