3GPP TSG-RAN WG2 meeting #99bis
`Prague, Czech Republic, 9th – 13th October 2017
`
`10.4.1.6.4
`Agenda item:
`ITRI
`Source:
`Discussion on the granularity of SI change notification
`Title:
`Document for: Discussion and Decision
`
`R2-1711767
`(revision of R2-1709080)
`
`1. Introduction
`
`RAN2#97 meeting reached the following agreements on minimum SI [1]:
`
`Agreements
`1: Broadcasting some kind of index/identifier in minimum SI to enable the UE to avoid re-
`acquisition of already stored SI-block(s)/SI message(s). The index/identifier and associated
`system information can be applicable in more than one cell. System information valid in one
`cell may be valid also in other cells.
`
`
`
`In RAN2#98 meeting agreements on on-demand/other SI include [2]:
`
`Agreements
`There will be at least a value tag and area ID
`-
`value tag is associated to each SIB
`-
`value tag can be valid in only one cell or when combined with an area ID to be valid in more
`than one cell.
`
`
`
`The following agreements are made during RAN1 201706AH meeting [3]:
`
`–
`
`• Following contents are carried in NR-MIB
`–
`(Part of) SFN: [7 - 10] bits
`• At least 80 ms granularity
`– FFS: indication within 80 ms
`[H-SFN: 10 bits]
`• RAN1 will ask RAN2
`– Timing information within radio frame: [0 - 7] bits
`• E.g., SS block time index: [0 - 6] bits
`• E.g., half radio frame timing: [0 - 1] bit
`– RMSI scheduling information: [x] bits
`• CORESET(s) information: [x] bits
`– Simplified information of CORESET(s) compared to CORESET(s) information
`for UE-specific configuration is considered
`– E.g., Time/frequency resource configuration of CORESET(s)
`–
`[Numerology of RMSI: [0 - 2] bits]
`[Information regarding frequency resources for PDSCH scheduling: [x] bits]
`
`•
`
`
`
`This contribution discuss on the notification of SI change.
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`2. Discussion
`NR UEs could use stored SI if the SI is valid. UE could determine the validity of stored SIBs other than SIB1 by checking
`the associated value tags in the scheduling information transmitted from gNB. Based on RAN agreement that there is no
`value tag/area relate info in MIB [4], UE needs to check the content of SIB1 to determine the validity of SIB1.
`
`Upon system information change, the change could be notified from gNB to UE (e.g., by paging message). It is possible
`for gNB to provide finer granularity such as SIB-specific or SI message-specific SI change notification. Also it is possible
`for gNB to provide the latest value tag associated with the updated SIB.
`
`
`
`The scenarios of SIB1 change and SIBs other than SIB1 change are used for discussion on whether finer granularity SI
`change notification is beneficial.
`
`Scenario 1: change of SIB1
`
`
`
`
`
`
`
`
`
`If the SI change notification is SIB-specific, UE can identify the change of SIB1 upon the notification. The UE
`
`
`
`
`acquires the latest SIB1 from gNB according to the SIB1 scheduling information carried in MIB and update the
`
`
`
`
`stored SIB1 to the latest one. The UE may check the scheduling information carried in the latest SIB1 for the validity
`
`of the other stored SIBs. If the scheduling information is different from the stored scheduling information, the UE
`
`can identify the changed SIBs and acquire the updated SIBs accordingly.
`
`If the notification is not SIB-specific, UE couldn’t identify which part of SI is changed. The UE should acquire the
`latest SIB1 from gNB and check the scheduling information for the validity of the other stored SIBs. If the value
`tag/area information associated a SIB is different from the stored one, UE then identifies the changed SIB(s) and
`acquires the latest SIBs from gNB accordingly.
`
`When it is SIB1 change, UEs need not to distinguish the notification was triggered by scheduling information change
`or triggered by the content of SIB1 change.
`
`Observation 1: UE needs to re-acquire SIB1 upon receiving SI change notification.
`Observation 1a: When the SI change notification is triggered by SIB1 change, UEs need not to distinguish the
`notification is triggered by scheduling information change or triggered by the content of SIB1
`change.
`
`Scenario 2: change of SIBs other than SIB1
`
` 
`
`
`
`In case of SIB-specific SI change notification, UE can identify the change of a specific SIB upon the notification.
`The UE may use the stored scheduling information to monitor the scheduled SI window of the concerned SIB. The
`UE may receive multiple SI change notification in a modification period and acquire the updated SIB in the next
`modification period (Figure 1).
`
`If cross modification period SI change notification is supported, UE may need value tag associated with the
`concerned SIB to determine whether or not to re-acquire the update SIB in the next modification period.
`
`Observation 2: If cross-modification-period SI change notification is supported, including value tag associated with
`the concerned SIB may help UE to determine whether or not to re-acquire the update SIB in the
`next modification period.
`
`
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`
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`
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`
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`Change notification
`
`Updated information
`
`BCCH modification period (n)
`
`BCCH modification period (n+1)
`
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`Figure 1. Change of system Information
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` If the associated value tag is included in the notification, the UE could autonomously update stored scheduling
`information to the latest value tag after successful acquired the changed SIB. However, it is a concern for UE to
`update the stored SIB1 autonomously without verifying the actual scheduling information in the latest SIB1
`provided by gNB.
`
` If the associated value tag is not included in the notification, the UE needs to acquire the latest SIB1 to update the
`value tag of the concerned SIB and to update the stored scheduling information to the latest one.
`
`If the notification is not SIB-specific, the UE should acquire the latest SIB1 from gNB and check the scheduling
`information for the validity of the other stored SIBs. If the value tag/area information associated with a SIB is
`different from the stored one, UE then identifies the changed SIB(s) and acquires the latest SIBs from gNB
`accordingly.
`
`Observation 3: UE is able to re-acquire only the SIBs which are updated.
`Observation 3a: Including value tag in the SI change notification could help UE autonomously update the latest
`value tag of the concerned SIB in the stored scheduling information. However, that UE autonomous
`could be a concern.
`Observation 3b: Upon SI change notification, UE needs to update the stored SIB1 irrespective of SIB-specific SI
`change notification or not.
`
`
`
`Based on the discussions and the observations, neither SIB/SI message-specific SI change notification nor value tag
`associated with the concerned SIB/SI message benefits UE in SIB re-acquiring. It is proposed that RAN2 not to provide
`SIB-specific SI change notification.
`Proposal 1: It is proposed that RAN2 not to provide SIB/SI message-specific SI change notification.
`Proposal 2: It is proposed that RAN2 not to include value tag in the SI change notification.
`
`
`
`3. Conclusion
`In this contribution we investigate the UE procedure of SIB re-acquirement and provide the following observations:
`
`
`Observation 1: UE needs to re-acquire SIB1 upon receiving SI change notification.
`Observation 1a: When the SI change notification is triggered by SIB1 change, UEs need not to distinguish the
`notification is triggered by scheduling information change or triggered by the content of SIB1
`change.
`Observation 2: If cross-modification-period SI change notification is supported, including value tag associated with
`the concerned SIB may help UE to determine whether or not to re-acquire the update SIB in the
`next modification period.
`Observation 3: UE is able to re-acquire only the SIBs which are updated.
`Observation 3a: Including value tag in the SI change notification could help UE autonomously update the latest
`value tag of the concerned SIB in the stored scheduling information. However, that UE autonomous
`could be a concern.
`Observation 3b: Upon SI change notification, UE needs to update the stored SIB1 irrespective of SIB-specific SI
`change notification or not.
`
`
`
`Based on the observations, our conclusions for RAN2 to discuss and agree are proposed as below:
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`Proposal 1: It is proposed that RAN2 not to provide SIB-specific SI change notification.
`Proposal 2: It is proposed that RAN2 not to include value tag in the SI change notification.
`
`
`
`References
`[1] R2-1702451, Report of 3GPP TSG RAN WG2 meeting #97.
`
`[2] R2-1707601, Report of 3GPP TSG RAN2#98 meetinng, Hangzhou, China.
`
`[3] R1-171712032, Final Report of 3GPP TSG RAN WG1 #AH_NR2 v1.0.0.
`
`[4] R2-1707602, Report of 3GPP TSG RAN WG2 NR AdHoc#2 meeting, Qingdao, China.
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