3.oeo000020 lte call drop diagnosis issue 1

LTE Call Drop Diagnosis

Confidential Information of Huawei. No Spreading

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� In the second scenario, if 4 seconds prior to the reception of RRC Connection Release there


were no RLC layer data transmitting call drop will not be counted. This consideration is

because of some special scenario, e.g. data adapter user may plug out the data adapter

without detaching it when service is done. In this case call drop is not counted.


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� In FTP downloading or uploading (or packet injection), if there is not manual intervention


the throughput should persist. If it suddenly dropped to bottom, call drop very much

possibly occurred.


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� L.E-RAB.AbnormRel is the statistics of total number of eRAB abnormal releases of the cell


in the eNodeB based on data transmission of different causes and users.

� L.E-RAB.NormRel is the statistics of total number of eRAB normal releases.


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� Scenario 1: as shown at point A in the left figure, when the eNodeB sends an E-RAB


RELEASE INDICATION message and the cause value is not “Normal Release”, “User

Inactivity”, “CS fallback triggered” or “Inter-RAT redirection” this counter is incremented;

� Scenario 2: as shown at point A in the right figure, when the eNodeB sends a UE CONTEXT

RELEASE REQUEST message to the MME all E-RABs of the UE will be released. If the cause

of release is not “Normal Release”, “User Inactivity”, “CS fallback triggered” or “Inter-RAT

redirection”, the counter will be incremented.


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� According to the release cause value in message E-RAB RELEASE COMMAND(E-RAB


RELEASE INDICATION) or UE CONTEXT RELEASE COMMAND(UE CONTEXT RELEASE

REQUEST), counters for various abnormal release causes count.

� When the release cause is faults at the radio network layer, L.E-

RAB.AbnormRel.Radio counts.

� When the release cause is faults at the radio transport layer, L.E-

RAB.AbnormRel.TNL counts.

� When the release cause is network congestion, L.E-RAB.AbnormRel.Cong counts,

including the abnormal releases caused by pre-emption and resource congestion.

� When the release cause is handover failure, L.E-RAB.AbnormRel.HOFailure counts.


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� ANR：Automatic Neighbor Relation



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� In corner effect, because the signal of the source cell drops rapidly, the UE does not have


enough time to complete the signaling process with the eNodeB, call drop occurs.

� In needle-tip effect, it leads to call drop that the signal of the source cell drops rapidly or

that of the target cell increases rapidly and then decreases sharply.

� In the view of signaling process, usually the UE reports neighbor cell’s A3 MRs and the

eNodeB has received it, then HO command is sent out but the UE cannot receive it. At this

time if there is UE’s context in the target cell and the reestablishment succeeds, call drop

may not occur.


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� In the view of signaling process it is found that just after a HO the UE starts reporting new


MRs and a new HO is triggered. Because there are some more reconfiguration messages

(CQP report mode, sounding, etc.) need to be delivered after the HO, in the ping-pong

area it is susceptible to call drops due to time-out of these commands.


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� In general, the selection of top cells complies the below rules:


� Top cell’s call drop rate KPI is worse than the average of the whole network.

� Rank the cells by the absolute call drops in descending order.


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� The value range of CQI is from 0 to 15, the bigger value the better coverage.


� The value range of MCS of PDSCH and PUSCH is from 0 to 31, the bigger value the better

coverage.


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� Congestion and user number related counter:


� L.Traffic.User.Avg: Average number of users in a cell

� L.Traffic.User.Max: Maximum number of users in a cell

� L.LC.ULCong.Num.Cell: Number of times uplink congestion occurs in a cell

� L.LC.DLCong.Num.Cell: Number of times downlink congestion occurs in a cell

� L.LC.ULCong.Dur.Cell: Duration of uplink congestion in a cell

� L.LC.DLCong.Dur.Cell: Duration of downlink congestion in a cell

� L.LC.User.Rel: Number of GBR service releases due to congestion in a cell


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� Outgoing handover counters between two specific cells


� L.HHO.NCell.PrepAttOut: Number of outgoing handover attempts between two

specific cells

� L.HHO.NCell.ExecAttOut: Number of outgoing handover executions between two

specific cells

� L.HHO.NCell.ExecSuccOut: Number of successful outgoing handovers between two

cells

� L.HHO.Ncell.PingPongHo: Number of ping-pong handovers between two specific

cells


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3.oeo000020 lte call drop diagnosis issue 1

Engineering

Transcript of 3.oeo000020 lte call drop diagnosis issue 1