3GPP TSG-RAN WG2 Meeting#AH1801
`
` R2-1800453
`
`R2-18xxxxx
` (Re-submission of R2-1708108)
`
`Vancouver, Canada, 22 - 26 Jan 2018
`Agenda item:
`10.4.1.6.5
`Source:
`ZTE
`Title:
`Upper layer actions for the Random Access problem
`Document for: Discussion and Decision
`
`1 Introduction
`There has been some discussion on the on-demand SI procedure, and the following agreement has been made:
`
`Agreement RAN2 adhoc#2:
`1 Msg1 for SI request re-transmission is continued until reaching max preamble transmissions. Thereafter, a
`Random Access problem to upper layers is indicated. (Depending on the NR RACH procedure design)
`FFS: Upper layer actions when MAC reports Random Access problem. To be discussed in CP session.
`
`In this contribution, we focus on the Upper layer actions when MAC reports Random Access problem.
`
`2 Discussions
`In this section, we first describe the possible solutions according to the email discussion in #98 meeting and then
`introduce 3 different scenarios according to the neighbor cell layout, at last we will compare the performance of each
`solution for 3 different scenarios.
`
`2.1 Alternatives and Scenarios
`In the LTE R12, a new abnormal case processing scheme was introduced. With this scheme, if the UE received the
`Random access problem for a consecutive connEstFailCount times on the same cell, the UE will use
`connEstFailOffset for the parameter Qoffsettemp for the concerned cell when performing cell selection and re-
`selection for a period as indicated by connEstFailOffsetValidity. When performing cell selection, if no suitable or
`acceptable cell can be found, it is up to UE implementation whether to stop using connEstFailOffset for the parameter
`Qoffsettemp during connEstFailOffsetValidity for the concerned cell. Besides, in the last meeting there are also some
`other alternatives, and combine the alternatives provided in [1], we can get the following 3 alternatives:
`
`Alternative 1: UE shall treat the cell as barred
`
`Alternative 2: UE retry the SI request on the current cell upon a certain timer expiry
`
`Ex.1022
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` Note: In [1], the alternative 2 is that treat the cell as barred for the essential SI and retry SI
` request for the non-essential SI, we think it could be seen as a combination of Alternative 1
` and 2. For simplicity, we modify the alternative 2 as above.
`
` Alternative 3: Increase cell selection or reduce re-selection threshold for a period as that scheme introduced
`
` in LTE R12.
`
`For the sake of discussion, according to the neighbor cell layout we divide all the scenarios into 3 types as follow:
`
`
`
`
`
`
`
`Scenario A: No suitable neighbor cell;
`
`Scenario B: There is suitable neighbor cell with worse RSRP/RSRQ;
`
`Scenario C: There is suitable neighbor cell which can provide similar RSRP/RSRQ.
`
`In the next section we will focus on performance comparison of each solution for 3 different scenarios.
`
`2.2 Comparison
`
`Table 1 Performance Comparison
`
`Scenario/Solution
`
`Option1: Barred directly
`
`Option 2: Retry
`
`Option3: Increase threshold
`
`Scenario A :
`
`No suitable neighbor
`cell
`
`Scenario B:
`
`Worse Rsrp/Rsrq
`
`Scenario C:
`
`Similar Rsrp/Rsrq
`
`
`
`Enter no service state
`
`
`Stay on the current
`cell and retry
`
`Stay on the current cell and
`retry
`
`UE will camp on the
`neighbor cell
`
`Stay on the current
`cell and retry
`
`UE will re-select to the
`neighbor cell at last
`
`UE will camp on the
`neighbor cell
`
`Stay on the current
`cell and retry
`
`UE will re-select to the
`neighbor cell
`
`From theTable1, we can see that for option 1, the UE may enter no service state when there is no suitable neighbor
`cell. For the option 2, the use can’t re-select to the neighbor cell even when the neighbor cell can provide similar
`RSRP/RSRQ, which will result in unnecessary power consumption.
`
`Observation 1: If the UE treat the cell as barred when MAC reports Random Access problem, the UE may
`enter no service state when there is no suitable neighbor cell.
`
`Observation 2: Re-sending SI Request on the current cell will result in unnecessary power consumption when
`the neighbor cell can provide similar RSRP/RSRQ.
`
`Proposal: If the UE received the Random access problem for consecutive times on the same cell, the UE will
`adopt Qoffsettemp for the concerned cell when performing cell selection and re-selection for a period.
`
`3 Conclusion
`Based on all the analysis above, we give our observations and proposal as:
`
`Ex.1022
`APPLE INC. / Page 2 of 3
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`

`

`Observation 1: If the UE treat the cell as barred when MAC reports Random Access problem, the UE may
`enter no service state when there is no suitable neighbor cell.
`
`Observation 2: Re-sending SI Request on the current cell will result in unnecessary power consumption when
`the neighbor cell can provide similar RSRP/RSRQ.
`
`Proposal: If the UE received the Random access problem for consecutive times on the same cell, the UE will
`adopt Qoffsettemp for the concerned cell when performing cell selection and re-selection for a period.
`
`4. References
`[1] R2-1707090 Summary of [98#34][NR] On demand SI (Lenovo) Lenovo, Motorola Mobility report
`Rel-15 NR_newRAT-Core
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`Ex.1022
`APPLE INC. / Page 3 of 3
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