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Content for  TS 38.423  Word version:  16.3.0

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8.4.4  ResetWord‑p. 73

8.4.4.1  General

The purpose of the Reset procedure is to align the resources in the NG-RAN node1 and the NG-RAN node2 in the event of an abnormal failure. The procedure either resets the Xn interface or selected UE contexts. This procedure doesn't affect the application level configuration data exchanged during, e.g., the Xn Setup procedure.
The procedure uses non UE-associated signalling.

8.4.4.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.4.2-1: Reset, successful operation
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The procedure is initiated with the RESET REQUEST message sent from the NG-RAN node1 to the NG-RAN node2. Upon receipt of this message,
  • if the RESET REQUEST message indicates full reset the NG-RAN node2 shall abort any other ongoing procedures over Xn between the NG-RAN node1 and the NG-RAN node2. The NG-RAN node2 shall delete all the context information related to the NG-RAN node1, except the application level configuration data exchanged during the Xn Setup or the NG-RAN node Configuration Update procedures and release the corresponding resources. After completion of release of the resources, the NG-RAN node2 shall respond with the RESET RESPONSE message.
  • if the RESET REQUEST message indicates partial reset, the NG-RAN node2 shall abort any other ongoing procedures only for the indicated UE associated signalling connections identified either by the NG-RAN node1 UE XnAP ID IE or the NG-RAN node1 UE XnAP ID IE or both, for which the NG-RAN node2 shall delete all the context information related to the NG-RAN node1 and release the corresponding resources. After completion of release of the resources, the NG-RAN node2 shall respond with the RESET RESPONSE message indicating the UE contexts admitted to be released. The NG-RAN node2 receiving the request for partial reset does not need to wait for the release or reconfiguration of radio resources to be completed before returning the RESET RESPONSE message. The NG-RAN node2 receiving the request for partial reset shall include in the RESET RESPONSE message, for each UE association to be released, the same list of UE-associated logical Xn-connections over Xn. The list shall be in the same order as received in the RESET REQUEST message and shall include also unknown UE-associated logical Xn-connections.
If case of network sharing with multiple cell ID broadcast with shared Xn-C signalling transport, as specified in TS 38.300, the RESET REQUEST message and the RESET RESPONSE message shall include the Interface Instance Indication IE to identify the corresponding interface instance.
Interactions with other procedures:
If the RESET REQUEST message indicates full reset, the NG-RAN node2 shall abort any other ongoing procedure (except for a Reset procedures).
If the RESET REQUEST message indicates partial reset, the NG-RAN node2 shall abort any other ongoing procedure (except for a Reset procedures) on the same Xn interface related to a UE associated signalling connection indicated in the RESET REQUEST message.
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8.4.4.3  Unsuccessful OperationWord‑p. 74
Void.

8.4.4.4  Abnormal Conditions

If the RESET REQUEST message is received, any other ongoing procedure (except another Reset procedure) on the same Xn interface shall be aborted.
If the Reset procedure is ongoing and the responding node receives the RESET REQUEST message from the peer entity on the same Xn interface, it shall respond with the RESET RESPONSE message as specified in 8.4.4.2.
If the initiating node does not receive the RESET RESPONSE message, the initiating node may reinitiate the Reset procedure towards the same NG-RAN node, provided that the content of the new RESET REQUEST message is identical to the content of the previously unacknowledged RESET REQUEST message.
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8.4.5  Error Indication

8.4.5.1  General

The Error Indication procedure is initiated by an NG-RAN node to report detected errors in one incoming message, provided they cannot be reported by an appropriate failure message.
If the error situation arises due to reception of a message utilising UE associated signalling, then the Error Indication procedure uses UE-associated signalling. Otherwise the procedure uses non UE-associated signalling.

8.4.5.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.5.2-1: Error Indication, successful operation.
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When the conditions defined in clause 10 are fulfilled, the Error Indication procedure is initiated by the ERROR INDICATION message sent from the node detecting the error situation.
The ERROR INDICATION message shall contain at least either the Cause IE or the Criticality Diagnostics IE.
In case the Error Indication procedure is triggered by UE associated signalling, in the course of handover signalling and signalling for dual connectivity, the Old NG-RAN node UE XnAP ID IE and the New NG-RAN node UE XnAP ID IE shall be included in the ERROR INDICATION message. If any of the Old NG-RAN node UE XnAP ID IE and the New NG-RAN node UE XnAP ID IE is not correct, the cause shall be set to an appropriate value.
If case of network sharing with multiple cell ID broadcast with shared Xn-C signalling transport, as specified in TS 38.300, the ERROR INDICATION message shall include the Interface Instance Indication IE to identify the corresponding interface instance.
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8.4.5.3  Unsuccessful Operation

Not applicable.

8.4.5.4  Abnormal ConditionsWord‑p. 75
Void.

8.4.6  Xn Removal

8.4.6.1  General

The purpose of the Xn Removal procedure is to remove the signaling connection between two NG-RAN nodes in a controlled manner. If successful, this procedure erases any existing application level configuration data in the two nodes.
The procedure uses non UE-associated signaling.
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8.4.6.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.6.2-1: Xn Removal, successful operation
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An NG-RAN node1 initiates the procedure by sending the XN REMOVAL REQUEST message to a candidate NG-RAN node2. Upon reception of the XN REMOVAL REQUEST message the candidate NG-RAN node2 shall reply with the XN REMOVAL RESPONSE message. After receiving the XN REMOVAL RESPONSE message, the initiating NG-RAN node1 shall initiate removal of the TNL association towards NG-RAN node2 and may remove all resources associated with that signaling connection. The candidate NG-RAN node2 may then remove all resources associated with that signaling connection.
If the Xn Removal Threshold IE is included in the XN REMOVAL REQUEST message, the candidate NG-RAN node2 shall, if supported, accept to remove the signalling connection with NG-RAN node1 if the Xn Benefit Value of the signalling connection determined at the candidate NG-RAN node2 is lower than the value of the Xn Removal Threshold IE.
If case of network sharing with multiple cell ID broadcast with shared Xn-C signalling transport, as specified in TS 38.300, the XN REMOVAL REQUEST message and the XN REMOVAL RESPONSE message shall include the Interface Instance Indication IE to identify the corresponding interface instance.
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8.4.6.3  Unsuccessful OperationWord‑p. 76
Reproduction of 3GPP TS 38.423, Figure 8.4.6.3-1: Xn Removal, unsuccessful operation
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If the candidate NG-RAN node2 cannot accept to remove the signaling connection with NG-RAN node1 it shall respond with an XN REMOVAL FAILURE message with an appropriate cause value.
If case of network sharing with multiple cell ID broadcast with shared Xn-C signalling transport, as specified in TS 38.300, the XN REMOVAL REQUEST message and the XN REMOVAL FAILURE message shall include the Interface Instance Indication IE to identify the corresponding interface instance.
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8.4.6.4  Abnormal Conditions

Void.

8.4.7  Failure Indication |R16|

8.4.7.1  General

The purpose of the Failure Indication procedure is to transfer information regarding RRC re-establishment attempts, or received RLF Reports, between NG-RAN nodes. The signalling takes place from the NG-RAN node at which a re-establishment attempt is made, or an RLF Report is received, to an NG-RAN node to which the UE concerned may have previously been attached prior to the connection failure. This may aid the detection of radio link failure, handover failure cases.
The procedure uses non UE-associated signalling.
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8.4.7.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.7.2-1: Failure Indication, successful operation
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NG-RAN node2 initiates the procedure by sending the FAILURE INDICATION message to NG-RAN node1, following a re-establishment attempt or an RLF Report reception from a UE at NG-RAN node2, when NG-RAN node2 considers that the UE may have previously suffered a connection failure at a cell controlled by NG-RAN node1.
If the UE RLF Report Container IE is included in the FAILURE INDICATION message, NG-RAN node1 shall use it to derive failure case information.

8.4.7.3  Unsuccessful OperationWord‑p. 77
Not applicable.

8.4.7.4  Abnormal Conditions

Void.

8.4.8  Handover Report |R16|

8.4.8.1  General

The purpose of the Handover Report procedure is to transfer mobility related information between NG-RAN nodes.
The procedure uses non UE-associated signalling.

8.4.8.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.8.2-1: Handover Report, successful operation
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NG-RAN node1 initiates the procedure by sending the HANDOVER REPORT message to NG-RAN node2. When receiving the message NG-RAN node2 shall assume that a mobility-related problem was detected.
If the Handover Report Type IE is set to "HO too early" or "HO to wrong cell", then NG-RAN node1 indicates to NG-RAN node2 that, following a successful handover from a cell of NG-RAN node2 to a cell of NG-RAN node1, a radio link failure occurred and the UE attempted RRC Re-establishment or re-connected either at the original cell of NG-RAN node2 (Handover Too Early), or at another cell (Handover to Wrong Cell). The detection of Handover Too Early and Handover to Wrong Cell events is made according to TS 38.300.
The HANDOVER REPORT message may include:
  • the Mobility Information IE, if the Mobility Information IE was sent for this handover from NG-RAN node2;
  • the Source cell C-RNTI IE.
If received, NG-RAN node2 uses the above information according to TS 38.300.
If the Handover Report Type IE is set to "Inter-system ping-pong", then NG-RAN node2 shall deduce that a completed handover from a cell of NG-RAN node2 to a cell in another system might have resulted in an inter-system ping-pong and the UE was successfully handed over to a cell of NG-RAN node1 (indicated with Target cell CGI IE).
Interaction with the Failure Indication procedure:
If NG-RAN node1 receives a UE RLF Report from an NG-RAN node via the FAILURE INDICATION message, as described in TS 38.300, NG-RAN node1 may also include it in the UE RLF Report Container IE included in the HANDOVER REPORT message.
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8.4.8.3  Unsuccessful Operation

Not applicable.

8.4.8.4  Abnormal ConditionsWord‑p. 78
Void.

8.4.9  Mobility Settings Change |R16|

8.4.9.1  General

This procedure enables an NG-RAN node to negotiate the handover trigger settings with a peer NG-RAN node controlling neighbouring cells.
The procedure uses non UE-associated signalling.

8.4.9.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.9.2-1: Mobility Settings Change, successful operation
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NG-RAN node1 initiates the procedure by sending the MOBILITY CHANGE REQUEST message to NG-RAN node2.
Upon receipt, NG-RAN node2 shall evaluate if the proposed NG-RAN node2 handover trigger modification may be accepted. If NG-RAN node2 is able to successfully complete the request it shall reply with MOBILITY CHANGE ACKNOWLEDGE message.

8.4.9.3  Unsuccessful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.9.3-1: Mobility Settings Change, unsuccessful operation
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If the requested parameter modification is refused by NG-RAN node2, or if NG-RAN node2 is not able to complete the procedure, NG-RAN node2 shall send the MOBILITY CHANGE FAILURE message with the Cause IE set to an appropriate value. NG-RAN node2 may include the Mobility Parameters Modification Range IE in the MOBILITY CHANGE FAILURE message, for example in cases when the proposed change is out of the permitted range.

8.4.9.4  Abnormal Conditions

Void.

8.4.10  Resource Status Reporting Initiation |R16|Word‑p. 79

8.4.10.1  General

This procedure is used by an NG-RAN node to request the reporting of load measurements to another NG-RAN node.
The procedure uses non UE-associated signalling.

8.4.10.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.10.2-1: Resource Status Reporting Initiation, successful operation
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NG-RAN node1 initiates the procedure by sending the RESOURCE STATUS REQUEST message to NG-RAN node2 to start a measurement, stop a measurement or add cells to report for a measurement. Upon receipt, NG-RAN node2:
  • shall initiate the requested measurement according to the parameters given in the request in case the Registration Request IE set to "start"; or
  • shall stop all cells measurements and terminate the reporting in case the Registration Request IE is set to "stop"; or
  • shall add cells indicated in the Cell To Report List IE to the measurements initiated before for the given measurement IDs, in case the Registration Request IE is set to "add". If measurements are already initiated for a cell indicated in the Cell To Report List IE, this information shall be ignored.
If the Registration Request IE is set to "start" in the RESOURCE STATUS REQUEST message and the Report Characteristics IE indicates cell specific measurements, the Cell To Report List IE shall be included.
If Registration Request IE is set to "add" in the RESOURCE STATUS REQUEST message, the Cell To Report List IE shall be included.
If NG-RAN node2 is capable to provide all requested resource status information, it shall initiate the measurement as requested by NG-RAN node1 and respond with the RESOURCE STATUS RESPONSE message.
Interaction with other procedures
When starting a measurement, the Report Characteristics IE in the RESOURCE STATUS REQUEST indicates the type of objects NG-RAN node2 shall perform measurements on. For each cell, NG-RAN node2 shall include in the RESOURCE STATUS UPDATE message:
  • the Radio Resource Status IE, if the first bit, "PRB Periodic" of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to "1". If NG-RAN node2 is a gNB and if the cell for which Radio Resource Status IE is requested to be reported supports more than one SSB, the Radio Resource Status IE for such cell shall include the SSB Area Radio Resource Status Item IE for all SSB areas supported by the cell. If the SSB To Report List IE is included for a cell, the Radio Resource Status IE for such cell shall include the requested SSB Area Radio Resource Status List IE;
  • the TNL Capacity Indicator IE, if the second bit, "TNL Capacity Ind Periodic" of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to "1". The received TNL Capacity Indicator IE represents the lowest TNL capacity available for the cell.
  • the Composite Available Capacity Group IE, if the third bit, "Composite Available Capacity Periodic" of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to "1". If the Cell Capacity Class Value IE is included within the Composite Available Capacity Group IE, this IE is used to assign weights to the available capacity indicated in the Capacity Value IE. If NG-RAN node2 is a gNB and if the cell for which Composite Available Capacity Group IE is requested to be reported supports more than one SSB, the Composite Available Capacity Group IE for such cell shall include the SSB Area Capacity Value List for all SSB areas supported by the cell, providing the SSB area capacity with respect to the Cell Capacity Class Value. If the SSB To Report List IE is included for a cell, the Composite Available Capacity Group IE for such cell shall include the requested SSB Area Capacity Value List IE.
    If the cell for which Composite Available Capacity Group IE is requested to be reported supports more than one slice, and if the Slice To Report List IE is included for a cell, the Slice Available Capacity IE for such cell shall include the requested Slice Available Capacity Value Downlink IE and Slice Available Capacity Value Uplink IE, providing the slice capacity with respect to the Cell Capacity Class Value.
    - the Number of Active UEs IE, if the fourth bit, "Number of Active UEs" of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to "1";
  • the RRC Connections IE, if the fifth bit, "RRC Connections" of the Report Characteristics IE included in the RESOURCE STATUS REQUEST message is set to "1".
If the Reporting Periodicity IE in the RESOURCE STATUS REQUEST is present, this indicates the periodicity for the reporting of periodic measurements. the NG-RAN node2 shall report only once, unless otherwise requested within the Reporting Periodicity IE.
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8.4.10.3  Unsuccessful OperationWord‑p. 80
Reproduction of 3GPP TS 38.423, Figure 8.4.10.3-1: Resource Status Reporting Initiation, unsuccessful operation
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If any of the requested measurements cannot be initiated, NG-RAN node2 shall send the RESOURCE STATUS FAILURE message with an appropriate cause value.

8.4.10.4  Abnormal Conditions

For the same Measurement ID, if the initiating NG-RAN node1 does not receive either the RESOURCE STATUS RESPONSE message or the RESOURCE STATUS FAILURE message, the NG-RAN node1 may reinitiate the Resource Status Reporting Initiation procedure towards the same NG-RAN node, provided that the content of the new RESOURCE STATUS REQUEST message is identical to the content of the previously unacknowledged RESOURCE STATUS REQUEST message.
If the Report Characteristics IE bitmap is set to "0" (all bits are set to "0") in the RESOURCE STATUS REQUEST message then NG-RAN node2 shall initiate a RESOURCE STATUS FAILURE message with an appropriate cause value.
If the NG-RAN node2 receives a RESOURCE STATUS REQUEST message which includes the Registration Request IE set to "start" and the NG-RAN node1Measurement ID IE corresponding to an existing on-going load measurement reporting, then NG-RAN node2 shall initiate a RESOURCE STATUS FAILURE message with an appropriate cause value.
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8.4.11  Resource Status Reporting |R16|Word‑p. 81

8.4.11.1  General

This procedure is initiated by an NG-RAN node to report the result of measurements admitted by the NG-RAN node following a successful Resource Status Reporting Initiation procedure.
The procedure uses non UE-associated signalling.

8.4.11.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.11.2-1: Resource Status Reporting, successful operation
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NG-RAN node2 shall report the results of the admitted measurements in RESOURCE STATUS UPDATE message. The admitted measurements are the measurements that were successfully initiated during the preceding Resource Status Reporting Initiation procedure.

8.4.11.3  Unsuccessful Operation

Not applicable.

8.4.11.4  Abnormal Conditions

Void

8.4.12  Access And Mobility Indication |R16|

8.4.12.1  General

The purpose of the Access and Mobility Indication procedure is to transfer Access and Mobility related information between NG-RAN nodes.

8.4.12.2  Successful Operation

Reproduction of 3GPP TS 38.423, Figure 8.4.12.2-1: Access And Mobility Indication. Successful operation
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NG-RAN node1 initiates the procedure by sending the ACCESS AND MOBILITY INDICATION message sent to NG-RAN node2.

8.4.12.3  Abnormal ConditionsWord‑p. 82
Not applicable.


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