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5GS – UE‑Triggered Service Request – 02 of 36
Signalling flow for TS 23.502 UE-Triggered Service Request: UE to (R)AN - NAS Service request


Step 1, verbatim
UE to (R)AN: AN message (AN parameters, MM NAS Service Request (List Of PDU Sessions To Be Activated, List Of Allowed PDU Sessions, security parameters, PDU Session status)).
The List Of PDU Sessions To Be Activated is provided by UE when the UE wants to re-activate the PDU Session(s). The List Of Allowed PDU Sessions is provided by the UE when the Service Request is a response of a Paging or a NAS Notification for the PDU Session associated with non-3GPP access, and identifies the PDU Sessions that can be transferred to 3GPP access.
Editor's note: The required AN parameters are FFS.
In case of NG-RAN:
The AN parameters include Selected PLMN ID and Establishment cause. The Establishment cause provides the reason for requesting the establishment of an RRC connection.
The UE sends NAS Service Request message towards the AMF encapsulated in an RRC message to the RAN. The RRC message(s) that can be used to carry the 5G‑GUTI and this NAS message are described in TS 38.331 [12] and TS 36.331 [16].
If the Service Request is triggered for user data, the UE identifies, using the List Of PDU Sessions To Be Activated, the PDU Session(s) for which the UP connections are to be activated in NAS Service Request message. If the Service Request is triggered for signalling only, the UE doesn't identify any PDU Sessions To Be Activated. If this procedure is triggered for paging response, and the UE has at the same time some user data to be transferred, the UE identifies the PDU Session(s) whose UP connections are to be activated in MM NAS Service Request message, by the List Of PDU Sessions To Be Activated. Otherwise the UE does not identify any PDU Session(s) in the Service Request message for paging response.
If the Service Request over 3GPP access is triggered in response to the paging indicating non-3GPP access, the NAS Service Request message shall identify the list of PDU Sessions associated with the non-3GPP access that can be re-activated over 3GPP in the List Of Allowed PDU Sessions, as described in clause 4.2.3.3 (step 6) of this specification and in clause 5.6.8 of TS 23.501 [2].
The PDU Session status indicates the PDU Sessions available in the UE.
The UE shall not trigger a Service Request procedure for a PDU Session corresponding to a LADN when the UE is outside the area of availability of the LADN. And the UE shall not identify such PDU Session(s) in the List Of PDU Sessions To Be Activated, if the Service Request is triggered for other reasons.
For UE in CM-CONNECTED state, only the List Of PDU Sessions To Be Activated and List Of Allowed PDU Sessions need to be included in the MM NAS Service Request.