Section: 4.5.5 Exception handling and avoiding double barring
Content: Access attempts are allowed to proceed without further access control checking in order to avoid double barring for any service request or registration procedure initiated for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclauses 5.3.1.2 and 5.3.1.4). NOTE 1: The case of NAS signalling connection recovery also includes the cases where the UE was in S1 mode when the RRC connection failure occurred. For any service request or registration procedure of this kind the UE determines an access category as specified in subclause 4.5.1 and 4.5.2 or 4.5.2A, unless a different access category is specified in the rest of the present subclause. NOTE 2: Although the access control checking is skipped, the access category is determined for the specific access attempt in order to derive an RRC establishment cause. There are several services or an MO IMS registration related signalling for which the NAS needs to be informed when the service starts and stops, - because, while the service is ongoing or the MO IMS registration related signalling is ongoing, the mapping of other access attempts to a specific access category can be affected; and - in order to avoid double barring at the start of these services or at the start of the MO IMS registration related signalling. These services are: a) emergency service; b) MMTEL voice; c) MMTEL video; d) SMSoIP; e) SMS over NAS; f) 5GC-MO-LR procedure; g) UE-requested policy provisioning procedure for V2XP, ProSeP or both; and h) CIoT user data transfer over the control plane. The UE considers an emergency service a) as started when 5GMM receives a request from upper layers to register for emergency services or to establish a PDU session with request type = "initial emergency request" or "existing emergency PDU session". It considers the emergency service as stopped when this PDU session is released. In addition, the UE considers an emergency service a) as started when the 5GMM receives a request from the upper layers to perform emergency services fallback and performs emergency services fallback as specified in subclause 4.13.4.2 of 3GPP TS 23.502[ Procedures for the 5G System (5GS) ]  [9]. In this case, the UE considers the emergency service as stopped when: - the emergency PDU session established during the emergency services fallback is released if the UE has moved to an E-UTRA cell connected to 5GCN; or - the service request procedure involved in the emergency services fallback is completed otherwise. While an emergency service a) is ongoing, any access attempt triggered by the initiation of a registration, de-registration or service request procedure or by an uplink user data packet to be sent for an emergency PDU session with suspended user-plane resources is mapped to access category 2 = emergency. Once the emergency service has successfully passed access control, then as long as the service is ongoing, the following access attempts are allowed to proceed without further access control checking in order to avoid double barring: - any service request procedure related to the PDU session associated with request type = "initial emergency request" or "existing emergency PDU session"; and - any uplink user data packet to be sent for a PDU session with suspended user-plane resources associated with request type = "initial emergency request" or "existing emergency PDU session". NOTE 3: Although the access control checking is skipped, the mapping is performed in order to derive an RRC establishment cause. For services b) to h) the 5GMM receives explicit start and stop indications from the upper layers. For the case of handover of ongoing services b) to d) from non-3GPP access, the 5GMM receives an additional explicit handover of ongoing service from non-3GPP access indication from the upper layers. The 5GMM may receive an additional explicit "call-pull-initiated" indication from the upper layers (see 3GPP TS 24.174[ Support of multi-device and multi-identity in the IP Multimedia Subsystem (IMS); Stage 3 ]  [13D]). Once the service has successfully passed access control, then as long as the service is ongoing, the following access attempts are allowed to proceed without further access control checking in order to avoid double barring: - for services b), c) and d): 1) any service request procedure related to the PDU session established for DNN = "IMS" except between receiving from the lower layers an indication that access barring is applicable for all access categories except categories 0 and 2, or access barring is applicable for all access categories except category 0, and receiving from the lower layers an indication that the barring is alleviated for the access category determined for the access attempt; 2) any uplink user data packet to be sent for a PDU session with suspended user-plane resources established for DNN = "IMS" except between receiving from the lower layers an indication that access barring is applicable for all access categories except categories 0 and 2, or access barring is applicable for all access categories except category 0, and receiving from the lower layers an indication that the barring is alleviated for the access category determined for the access attempt; and 3) any start of the MO IMS registration related signalling; - for service d), if the upper layers have indicated a DNN used for SMSoIP and the indicated DNN used for SMSoIP is different from "IMS": 1) any service request procedure related to the PDU session established for the DNN used for SMSoIP except between receiving from the lower layers an indication that access barring is applicable for all access categories except categories 0 and 2, or access barring is applicable for all access categories except category 0, and receiving from the lower layers an indication that the barring is alleviated for access category 6; and 2) any uplink user data packet to be sent for a PDU session with suspended user-plane resources established for the DNN used for SMSoIP except between receiving from the lower layers an indication that access barring is applicable for all access categories except categories 0 and 2, or access barring is applicable for all access category except category 0, and receiving from the lower layers an indication that the barring is alleviated for access category 6. For the MO IMS registration related signalling, the 5GMM receives explicit start and stop indications from the upper layers. Once the MO IMS registration related signalling has successfully passed access control, then as long as the MO IMS registration related signalling is ongoing, the following access attempts are allowed to proceed without further access control checking in order to avoid double barring: 1) any service request procedure related to the PDU session established for DNN = "IMS" and for the DNN used for SMSoIP, if the upper layers have indicated a DNN used for SMSoIP and the indicated DNN used for SMSoIP is different from "IMS", except between receiving from the lower layers an indication that access barring is applicable for all access categories except categories 0 and 2, or access barring is applicable for all access categories except category 0 and receiving from the lower layers an indication that the barring is alleviated for the access category determined for the access attempt; and 2) any uplink user data packet to be sent for a PDU session with suspended user-plane resources established for DNN = "IMS" and for the DNN used for SMSoIP except between receiving from the lower layers an indication that access barring is applicable for all access categories except categories 0 and 2, or access barring is applicable for all access categories except category 0 and receiving from the lower layers an indication that the barring is alleviated for the access category determined for the access attempt; While an MMTEL voice call is ongoing: - any service request procedure related to the PDU session established for DNN = "IMS" is mapped to access category 4; - any uplink user data packet to be sent for a PDU session with suspended user-plane resources established for DNN = "IMS" is mapped to access category 4; and - any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode or 5GMM-IDLE mode with suspend indication for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclause 5.3.1.2 and 5.3.1.4) is mapped to access category 4. While an MMTEL video call is ongoing and no MMTEL voice call is ongoing: - any service request procedure related to the PDU session established for DNN = "IMS" is mapped to access category 5; - any uplink user data packet to be sent for a PDU session with suspended user-plane resources established for DNN = "IMS" is mapped to access category 5; and - any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode or 5GMM-IDLE mode with suspend indication for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclause 5.3.1.2 and 5.3.1.4) is mapped to access category 5. While an SMSoIP is ongoing, no MMTEL video call is ongoing and no MMTEL voice call is ongoing: - any service request procedure related to the PDU session established: 1) for DNN = "IMS"; or 2) for the DNN used for SMSoIP, if the upper layers have indicated a DNN used for SMSoIP and the indicated DNN used for SMSoIP is different from "IMS"; is mapped to access category 6; and - any uplink user data packet to be sent for a PDU session with suspended user-plane resources established: 1) for DNN = "IMS"; or 2) for the DNN used for SMSoIP, if the upper layers have indicated a DNN used for SMSoIP and the indicated DNN used for SMSoIP is different from "IMS"; is mapped to access category 6; and - any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode or 5GMM-IDLE mode with suspend indication for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclause 5.3.1.2 and 5.3.1.4) is mapped to access category 6. While an SMS over NAS is ongoing, no SMSoIP is ongoing, no MMTEL video call is ongoing and no MMTEL voice call is ongoing: - any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode or 5GMM-IDLE mode with suspend indication for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclause 5.3.1.2 and 5.3.1.4) is mapped to access category 6. While an MO IMS registration related signalling is ongoing, no SMSoIP is ongoing, no MMTEL video call is ongoing and no MMTEL voice call is ongoing: - any service request procedure related to the PDU session established: 1) for DNN = "IMS"; and 2) for the DNN used for SMSoIP, if the upper layers have indicated a DNN used for SMSoIP and the indicated DNN used for SMSoIP is different from "IMS"; is mapped to access category 9; and - any uplink user data packet to be sent for a PDU session with suspended user-plane resources established: 1) for DNN = "IMS"; and 2) for the DNN used for SMSoIP, if the upper layers have indicated a DNN used for SMSoIP and the indicated DNN used for SMSoIP is different from "IMS"; is mapped to access category 9; and - if no SMS over NAS is ongoing, any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclause 5.3.1.2 and 5.3.1.4) is mapped to access category 9. While a 5GC-MO-LR procedure is ongoing, no SMS over NAS is ongoing, no SMSoIP is ongoing, no MO IMS registration related signalling is ongoing, no MMTEL video call is ongoing, and no MMTEL voice call is ongoing: - any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode or 5GMM-IDLE mode with suspend indication for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclauses 5.3.1.2 and 5.3.1.4) is mapped to access category 3. While a UE-requested policy provisioning procedure for V2XP, ProSeP or both (see 3GPP TS 24.587[ Vehicle-to-Everything (V2X) services in 5G System (5GS); Stage 3 ]  [19B] and 3GPP TS 24.554[ Proximity-services (ProSe) in 5G System (5GS) protocol aspects; Stage 3 ]  [19E]), no 5GC-MO-LR procedure is ongoing, no SMS over NAS is ongoing, no SMSoIP is ongoing, no MMTEL video call is ongoing, and no MMTEL voice call is ongoing: - any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode for the purpose of NAS signalling connection recovery or following a fallback indication from the lower layers (see subclauses 5.3.1.2 and 5.3.1.4) is mapped to access category 3. While CIoT user data transfer over the control plane is ongoing, no 5GC-MO-LR procedure is ongoing, no SMS over NAS is ongoing, no SMSoIP is ongoing, no MMTEL video call is ongoing, and no MMTEL voice call is ongoing, any service request procedure initiated in 5GMM-IDLE mode following a fallback indication from the lower layers (see subclause 5.3.1.4) is mapped to access category 7. NOTE 3: Although the access control checking is skipped, the mapping is performed in order to derive an RRC establishment cause. If an access category is determined and the access control checking is skipped, the NAS shall determine the RRC establishment cause from one or more determined access identities and the access category as specified in subclause 4.5.6, the NAS shall initiate the procedure to send the initial NAS message for the access attempt and shall provide the RRC establishment cause to lower layers. If the UE receives from the lower layers an indication that access barring is applicable for all access categories except categories 0 and 2, or access barring is applicable for all access categories except category 0: a) if an MMTEL voice call or MMTEL video call is ongoing: 1) if the UE is operating in the single-registration mode and the UE's usage setting is "voice centric", the UE may attempt to select an E-UTRA cell connected to EPC. If the UE finds a suitable E-UTRA cell connected to EPC, it then proceeds with the appropriate EMM specific procedures and, if necessary, ESM procedures to make a PDN connection providing access to IMS available; see subclause 4.8.2 and 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]; and 2) if the UE is operating in the dual-registration mode, the UE may proceed in S1 mode with the appropriate EMM specific procedures and ESM procedures to make a PDN connection providing access to IMS available; see subclause 4.8.3 and 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]; and b) if SMSoIP is ongoing or an MO IMS registration related signalling is ongoing: 1) if the UE is operating in the single-registration mode, the UE may attempt to select an E-UTRA cell connected to EPC. If the UE finds a suitable E-UTRA cell connected to EPC, it then proceeds with the appropriate EMM specific procedures and, if necessary, ESM procedures to make a PDN connection providing access to IMS available; see subclause 4.8.2 and 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]; and 2) if the UE is operating in the dual-registration mode, the UE may proceed in S1 mode with the appropriate EMM specific procedures and ESM procedures to make a PDN connection providing access to IMS available; see subclause 4.8.3 and 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15].