4.3 RLF reporting

32.4223GPPRelease 17Subscriber and equipment traceTelecommunication managementTrace control and configuration managementTS

4.3.1 Trace session activation for RLF reporting in E-UTRAN

RLF reporting is activated to the eNB as a special Trace Session where the Job Type indicates RLF reporting only. The detailed procedure is shown in figure 4.3.1.1 where one UE experiences an RLF event and the reestablishment is successful to the source eNB.

Figure 4.3.1.1 Example scenario for RLF reporting when UE reestablishment is successful at source eNB.

When the eNB receives the Trace Session activation indicating RLF reporting only, the eNB shall start a Trace Session. This Trace Session shall collect only RLF reports received from the UE. The Trace Session activation message received from the EMS shall contain the following information:

– Trace Reference

– Job Type = RLF reporting only

– TCE IP Address

Figure 4.3. 1.2 shows another example where the UE reestablishment is failed in the source eNB, but successful at a target eNB.

Figure 4.3.1.2 Example scenario for RLF reporting when the UE reestablishment is successful at target eNB when there is X2 Link between target eNB and source eNB

If the UE re-establishes the RRC connection successfully at the target eNB the RLF reports are fetched by the target eNB. When there is X2 link between target eNB and source eNB, the target eNB forwards the RLF report in the X2 RLF Indication message. The procedures to be used at eNB to forward the RLF reports towards the management system is the same as the reporting will be done by the source eNB in this case.

If the UE re-establishes the RRC connection successfully at the target eNB the RLF reports are fetched by the target eNB. When there is no X2 link between target eNB and source eNB, as shown in Figure 4.3.1.3, the RLF report can’t be forwared to source eNB. In this case the Trace Record containing the Release 10 and aboveRLF reports shall be transferred to the TCE directly by the target eNB.

Figure 4.3.1.3 Example scenario for RLF reporting when there is no X2 Link between target eNB and source eNB

If a UE detects a Radio Link Failure event, it collects certain information as described in TS 36.300[37] and TS 36.331 [32]. Once the source eNB retrieved the RLF report from the UE or received it from the target eNB via X2 as defined in TS 36.300[37], or the target eNB retrieved the RLF report from the UE when there is no X2 link between target eNB and source eNB, eNB shall save the RLF report to the Trace Record. The Trace Record containing the RLF reports can be transferred to the TCE in the same mechanism as for normal subscriber and equipment trace or for MDT.

4.3.2 Trace session deactivation for RLF reporting in E-UTRAN

When the eNB receives the indication from the EM for trace session deactivation with the Job Type "RLF reporting only", it shall deactivate the trace session for the indicated Trace Reference of RLF reporting and stop RLF reporting to the TCE.

4.3.3 Trace session activation for RLF reporting in NG-RAN

RLF reporting is activated to the gNB as a special Trace Session where the Job Type indicates RLF reporting only. The detailed procedure is shown in figure 4.3.3.1 where one UE experiences an RLF event and the reestablishment is successful to the source gNB.

Figure 4.3.3.1 Example scenario for RLF reporting when UE reestablishment is successful at source gNB.

Upon Trace Session activation indicating RLF reporting only, the gNB shall start a Trace Session. This Trace Session shall collect only RLF reports received from the UE. The Trace Session activation information shall contain the following information:

– Trace Reference

– Job Type = RLF reporting only

– TCE IP Address for file based reporting or Trace Reporting Consumer URI for streaming reporting

Figure 4.3.3.2 shows another example where the UE reestablishment is failed in the source gNB, but successful at a target gNB.

Figure 4.3.3.2 Example scenario for RLF reporting when the UE reestablishment is successful at target gNB when there is Xn Link between target gNB and source gNB

If the UE re-establishes the RRC connection successfully at the target gNB the RLF reports are fetched by the target gNB. When there is Xn link between target gNB and source gNB, the target gNB forwards the RLF report in the Xn RLF Indication message. The procedures to be used at gNB to forward the RLF reports towards the management system is the same as the reporting will be done by the source gNB in this case.

If the UE re-establishes the RRC connection successfully at the target gNB the RLF reports are fetched by the target gNB. When there is no Xn link between target gNB and source gNB, as shown in Figure 4.3.x.3, the RLF report can’t be forwared to source gNB. In this case the Trace Record containing the RLF reports shall be reported by the target gNB.

Figure 4.3.3.3 Example scenario for RLF reporting when there is no Xn Link between target gNB and source gNB

If a UE detects a Radio Link Failure event, it collects certain information as described in TS 38.300[42] and TS 38.331 [43]. Once the source gNB retrieved the RLF report from the UE or received it from the target gNB via Xn as defined in TS 38.300[42], or the target gNB retrieved the RLF report from the UE when there is no Xn link between target gNB and source gNB, gNB shall save the RLF report to the Trace Record. The Trace Record containing the RLF reports can be reported in the same mechanism as for normal subscriber and equipment trace or for MDT.

4.3.4 Trace session deactivation for RLF reporting in NG-RAN

Upon trace session deactivation with the Job Type "RLF reporting only", gNB shall deactivate the trace session for the indicated Trace Reference of RLF reporting and stop RLF reporting.