Section: 4.19 5GS mobility management in WB-N1 mode for IoT
Content: In WB-N1 mode, a UE operating in category CE can operate in either CE mode A or CE mode B (see 3GPP TS 36.306[ Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio access capabilities ]  [25D]). If a UE that supports CE mode B and operates in WB-N1 mode, the UE's usage setting is not set to "voice centric" (see 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8]), and: a) the use of enhanced coverage is not restricted by the network; or b) CE mode B is not restricted by the network (see 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8]); the UE shall apply the value of the applicable NAS timer indicated in table 10.2.1 for WB-N1/CE mode. A UE that supports CE mode B and operates in WB-N1 mode shall not apply the value of the applicable NAS timer indicated in table 10.2.1 for WB-N1/CE mode before receiving an indication from the network that the use of enhanced coverage is not restricted, or CE mode B is not restricted, as described in this subclause. The NAS timer value obtained is used as described in the appropriate procedure subclause of this specification. The NAS timer value shall be calculated at start of a NAS procedure, and shall not be re-calculated until the NAS procedure is completed, restarted or aborted. The support of CE mode B by a UE is indicated to the AMF by lower layers and shall be stored by the AMF. When an AMF that supports WB-N1 mode performs NAS signalling with a UE, which supports CE mode B and operates in WB-N1 mode, the UE's usage setting is not set to "voice centric" (see 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8]) and the AMF determines that: a) the use of enhanced coverage is not restricted for the UE; or b) CE mode B is not restricted for the UE (see 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8]); the AMF shall calculate the value of the applicable NAS timer indicated in table 10.2.2 for WB-N1/CE mode. The NAS timer value obtained is used as described in the appropriate procedure subclause of this specification. The NAS timer value shall be calculated at start of a NAS procedure and shall not be re-calculated until the NAS procedure is completed, restarted or aborted.