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Content for  TS 38.473  Word version:  16.3.1

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8.4  RRC Message Transfer proceduresWord‑p. 58

8.4.1  Initial UL RRC Message Transfer

8.4.1.1  General

The purpose of the Initial UL RRC Message Transfer procedure is to transfer the initial RRC message to the gNB-CU. The procedure uses non-UE-associated signaling.

8.4.1.2  Successful operation

Reproduction of 3GPP TS 38.473, Figure 8.4.1.2-1: Initial UL RRC Message Transfer procedure.
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The establishment of the UE-associated logical F1-connection shall be initiated as part of the procedure.
If the DU to CU RRC Container IE is not included in the INITIAL UL RRC MESSAGE TRANSFER, the gNB-CU should reject the UE under the assumption that the gNB-DU is not able to serve such UE. If the gNB-DU is able to serve the UE, the gNB-DU shall include the DU to CU RRC Container IE and the gNB-CU shall configure the UE as specified in TS 38.331. The gNB-DU shall not include the ReconfigurationWithSync field in the CellGroupConfig IE as defined in TS 38.331 of the DU to CU RRC Container IE.
If the SUL Access Indication IE is included in the INITIAL UL RRC MESSAGE TRANSFER, the gNB-CU shall consider that the UE has performed access on SUL carrier.
If the RRC-Container-RRCSetupComplete IE is included in the INITIAL UL RRC MESSAGE TRANSFER, the gNB-CU shall take it into account as specified in TS 38.401.
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8.4.1.3  Abnormal Conditions

Not applicable.

8.4.2  DL RRC Message Transfer

8.4.2.1  General

The purpose of the DL RRC Message Transfer procedure is to transfer an RRC message The procedure uses UE-associated signalling.

8.4.2.2  Successful operationWord‑p. 59
Reproduction of 3GPP TS 38.473, Figure 8.4.2.2-1: DL RRC Message Transfer procedure
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If a UE-associated logical F1-connection exists, the DL RRC MESSAGE TRANSFER message shall contain the gNB-DU UE F1AP ID IE, which should be used by gNB-DU to lookup the stored UE context.If no UE-associated logical F1-connection exists, the UE-associated logical F1-connection shall be established at reception of the DL RRC MESSAGE TRANSFER message.
If the Index to RAT/Frequency Selection Priority IE is included in the DL RRC MESSAGE TRANSFER, the gNB-DU may use it for RRM purposes. If the Additional RRM Policy Index IE is included in the DL RRC MESSAGE TRANSFER, the gNB-DU may use it for RRM purposes.
The DL RRC MESSAGE TRANSFER message shall include, if available, the old gNB-DU UE F1AP ID IE so that the gNB-DU can retrieve the existing UE context in RRC connection reestablishment procedure, as defined in TS 38.401.
The DL RRC MESSAGE TRANSFER message shall include, if SRB duplication is activated, the Execute Duplication IE, so that the gNB-DU can perform CA based duplication for the SRB.
If the gNB-DU identifies the UE-associated logical F1-connection by the gNB-DU UE F1AP ID IE in the DL RRC MESSAGE TRANSFER message and the old gNB-DU UE F1AP ID IE is included, it shall release the old gNB-DU UE F1AP ID and the related configurations associated with the old gNB-DU UE F1AP ID.
If the UE Context not retrievable IE set to "true" is included in the DL RRC MESSAGE TRANSFER, the DL RRC MESSAGE TRANSFER may contain the Redirected RRC message IE and use it as specified in TS 38.401.
If the UE Context not retrievable IE set to "true" is included in the DL RRC MESSAGE TRANSFER, the DL RRC MESSAGE TRANSFER may contain the PLMN Assistance Info for Network Sharing IE, if available at the gNB-CU and may use it as specified in TS 38.401.
If the DL RRC MESSAGE TRANSFER message contains the New gNB-CU UE F1AP ID IE, the gNB-DU shall, if supported, replace the value received in the gNB-CU UE F1AP ID IE by the value of the New gNB-CU UE F1AP ID and use it for further signalling.
Interactions with UE Context Release Request procedure:
If the UE Context not retrievable IE set to "true" is included in the DL RRC MESSAGE TRANSFER, the gNB-DU may trigger the UE Context Release Request procedure, as specified in TS 38.401.
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8.4.2.3  Abnormal Conditions

Not applicable.

8.4.3  UL RRC Message Transfer

8.4.3.1  General

The purpose of the UL RRC Message Transfer procedure is to transfer an RRC message as an UL PDCP-PDU to the gNB-CU. The procedure uses UE-associated signalling.

8.4.3.2  Successful operationWord‑p. 60
Reproduction of 3GPP TS 38.473, Figure 8.4.3.2-1: UL RRC Message Transfer procedure
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When the gNB-DU has received from the radio interface an RRC message to which a UE-associated logical F1-connection for the UE exists, the gNB-DU shall send the UL RRC MESSAGE TRANSFER message to the gNB-CU including the RRC message as a RRC-Container IE.
If the Selected PLMN ID IE is contained in the UL RRC MESSAGE TRANSFER message, the gNB-CU may use it as specified in TS 38.401.
If the UL RRC MESSAGE TRANSFER message contains the New gNB-DU UE F1AP ID IE, the gNB-CU shall, if supported, replace the value received in the gNB-DU UE F1AP ID IE by the value of the New gNB-DU UE F1AP ID and use it for further signalling.
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8.4.3.3  Abnormal Conditions

Not applicable.

8.4.4  RRC Delivery Report

8.4.4.1  General

The purpose of the RRC Delivery Report procedure is to transfer to the gNB-CU information about successful delivery of DL PDCP-PDUs including RRC messages. The procedure uses UE-associated signalling.

8.4.4.2  Successful operation

Reproduction of 3GPP TS 38.473, Figure 8.4.4.2-1: RRC Delivery Report procedure.
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When the gNB-DU has successfully delivered an RRC message to the UE for which the gNB-CU has requested a delivery report, the gNB-DU shall send the RRC DELIVERY REPORT message to the gNB-CU containng the RRC Delivery Status IE and the SRB ID IE.

8.4.4.3  Abnormal ConditionsWord‑p. 61
Not applicable.


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