Section: 4.20 5GS session 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 and 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 10.3.1 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 10.3.1 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. If the use of extended NAS timer is indicated by the AMF (see 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8] and 3GPP TS 23.502[ Procedures for the 5G System (5GS) ]  [9]), the SMF shall calculate the value of the applicable NAS timer indicated in table 10.3.2 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. 4.21 Authentication and Key Management for Applications (AKMA) The UE may support AKMA. The purpose of AKMA is to provide authentication and key management to applications based on 3GPP credentials used for 5GS access as specified in 3GPP TS 33.535[ Authentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS) ]  [24A], which allows the UE to securely exchange data with an AKMA application function. Upon receiving a request from the upper layers to obtain AKMA Anchor Key (KAKMA) and AKMA Key Identifier (A-KID), the UE supporting AKMA shall derive the KAKMA and the AKMA Temporary Identifier (A-TID) from the valid KAUSF if available as specified in 3GPP TS 33.535[ Authentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS) ]  [24A], shall further derive the A-KID from the A-TID as specified in 3GPP TS 33.535[ Authentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS) ]  [24A] and shall provide KAKMA and A-KID to the upper layers. The UE supporting AKMA shall notify the upper layers whenever there is a change of the KAUSF upon reception of an EAP-success message in subclauses 5.4.1.2.2.8, 5.4.1.2.3.1 and 5.4.1.2.3A.1 or upon reception of SECURITY MODE COMMAND message in subclauses 5.4.2.3. During an ongoing primary authentication and key agreement procedure (see subclause 5.4.1), if the UE receives a request from upper layers to obtain KAKMA and A-KID, the UE shall derive the KAKMA and A-TID after the completion of the ongoing primary authentication and key agreement procedure, shall further derive the A-KID from the A-TID as specified in 3GPP TS 33.535[ Authentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS) ]  [24A] and shall provide KAKMA and A-KID to the upper layers. NOTE 1: The upper layers derive the AKMA Application Key (KAF) from KAKMA as specified in 3GPP TS 33.535[ Authentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS) ]  [24A]. NOTE 2: The knowledge of whether a certain application needs to use AKMA or not is application specific and is out of the scope of 3GPP. NOTE 3: The exact method of securing the data exchange at the upper layers using KAF is application specific and is out of the scope of 3GPP. NOTE 4: The upper layers request the UE NAS layer to provide KAKMA and A-KID before the upper layers initiate communication with an AKMA application function. NOTE 5: Upon receiving a request from the upper layers to obtain KAKMA and A-KID, if there is no KAUSF available, the UE NAS layer cannot derive the KAKMA and A-KID and provides an indication to the upper layers that KAKMA and A-KID cannot be generated. 4.22 Uncrewed aerial vehicle identification, authentication, and authorization