Section: 4.7.2.2 Establishment cause for non-3GPP access
Content: When establishment of an N1 NAS signalling connection over non-3GPP access is initiated, the UE shall: a) determine one or more access identities to be associated with the establishment of the N1 NAS signalling connection as specified in subclause 4.5.2 and table 4.5.2.1; b) select the establishment cause for non-3GPP access from the determined one or more access identities and the event which triggered initiation of the N1 NAS signalling connection over non-3GPP access by checking the rules specified in table 4.7.2.2.1; and c) provide the selected establishment cause for non-3GPP access to the lower layers. While an MMTEL voice call is ongoing: - any: 1) service request procedure; or 2) registration procedure; initiated in 5GMM-IDLE mode is mapped to "MO MMTel voice call" type access attempt. While an 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 is mapped to "MO MMTel video call" type access attempt. While an 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 is mapped to "MO SMS over IP" type access attempt. If the access attempt matches more than one rule, the establishment cause for non-3GPP access of the lowest rule number shall be used. Table 4.7.2.2.1: Mapping table for determination of establishment cause for non-3GPP access