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8/10/2019 C08 WCDMA RNO Drop Call Analysis
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Drop-call Analysis
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Analysis procedure
Neighbor list analysis
Coverage analysis
Handover analysis
Signaling analysis
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analysis procedure
Drive test tools: Qualcomm test UE/Moto A835 test UE
Agilent scanner 6455c
Agilent 6474A software
Post processing tools:
ACTIX Analyzer V2.0
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analysis procedure
Drop call event definition:
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analysis procedure
Drop call analysis procedure
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analysis procedure
1. To get the information about:
the place of the drop call,
in the edge of the 3G coverage or not
which 3G cells related
the distance between related 3G cells and the
drop call point
which 3G cell the call dropped on.
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analysis procedure
2.To analyze Neighbor list:
to find out any cell not defined in the neighbor list.
the best serving 3G cell before the call dropped
the best serving 3G/2G cell after the call dropped the existing neighbor list of the best serving 3G cell
intra-freq HO neighbor list
inter-freq HO neighbor list
inter-RAT HO neighbor list
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analysis procedure
3. To analyze the coverage:
the pilot coverage
CPICH transmission power
Coverage limited
System interference
Poor uplink coverage
Poor downlink coverage pilot pollution
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analysis procedure
3. To analyze the coverage:
the service coverage
Service related Maximum downlink transmission
power
SIR before the call dropped
Max uplink transmission power allowed for UE
Actual uplink transmission power before the call
dropped
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analysis procedure
4. To analyze the handover:
the signal change
Source cell
Target cell
insufficient handover area
Too late to add new cell
Too early to delete old cell ping-pang handover
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analysis procedure
5. To analyze the signaling:
for confused drop call
signaling in UE side in conjunction with
signaling in network side
Different interface: Iu, Iub, Iur, Uu
Different layer: NAS, RRC
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Analysis procedure
Neighbor list analysis
Coverage analysis
Handover analysis
Signaling analysis
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Neighbor list analysis
There maybe missing neighbor if the best
serving cell is not the same one before and after
the call dropped.
Before the call dropped, the best serving cellmaybe not the signal strongest cell
Before the call dropped, the best serving cell
should be picked out by the latest measurement
control message and corresponding 1d event
measurement report.
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Neighbor list analysis
Compare the scanner data with UE data
prior to the drop, the CPICH Ec/Io (and
CPICH RSCP) degrades for UE ONLY while
scanner shows no degradation
prior to the drop, the best server for the UE is
not the same as that of the scanner
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Neighbor list analysis
Dropcall position
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Neighbor list analysis
Active set and monitor set information
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Neighbor list analysis
Radio parameters information
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Neighbor list analysis
CPICH EcIo Compare between scanner and UE
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Neighbor list analysis
CPICH RSCP compare between scanner and UE
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Neighbor list analysis
SC compare between scanner and UE
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Neighbor list analysis
The measurement control message from
cell SC358
Conclusion: cell SC364 should be definedin the neighbor list of cell SC358 to avoid
the dropcall in this place
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Analysis procedure
Neighbor list analysis
Coverage analysis Handover analysis
Signaling analysis
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Coverage analysis
System Interference:
Both scanner and UE, the signal strongest cell
CPICH_EcNo_in_ActiveSet < -15 dB
And, CPICH_RSCP_in_ActiveSet > -80 dBm Poor Uplink Coverage:
Both scanner and UE
CPICH_EcNo_in_ActiveSet > -15 dB
And, CPICH_RSCP_in_ActiveSet > -95 dBm
And, UeTransmittedPower > 15 dBm
C
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Coverage analysis
Poor Downlink Coverage: Both scanner and UE , the signal strongest cell
CPICH_EcNo_in_ActiveSet < -15 dB
And, CPICH_RSCP_in_ActiveSet < -95 dBm
And, UeTransmittedPower < -15 dBm.
Coverage Limited Both scanner and UE , the signal strongest cell
CPICH_EcNo_in_ActiveSet < -15 dB And, CPICH_RSCP_in_ActiveSet < -95 dBm
And, UeTransmittedPower > 10 dBm.
C l i
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Coverage analysis
Pilot pollution:
4 or more pilots with their Ec/No above -15 dB
are in the active or monitored set
C l i
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Coverage analysis
To analyze the coverage, need to
Analyze the pilot coverage in conjunction with
the service coverage
Analyze the uplink coverage in conjunctionwith the downlink coverage
Analyze the scanner data in conjunction with
the UE dataAnalyze the CPICH RSCP in conjunction with
CPICH Ec/Io, SC
C l i
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Coverage analysis
Dropcall position
C l i
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Coverage analysis
Active set and monitor set information
C l i
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Coverage analysis
Radio parameters information
C l i
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Coverage analysis
CPICH Ec/Io
C l i
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Coverage analysis
CPICH RSCP
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Analysis procedure
Neighbor list analysis
Coverage analysis Handover analysis
Signaling analysis
H d l i
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Handover analysis
Handover type:
Intra-freq HO
Inter-freq HO
Inter-RAT HO
insufficient handover area
ping-pang handover
H d l i
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Handover analysis
Signal strength change
Handover analysis
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Drop calls and scrambling code plot
Scanner Best Server
Scrambling Code plot
It shows that drop call 1 occurred at an area of frequent
change of best server as shown by the scanner
scrambling code plot
Handover analysis
Handover analysis
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Drop Call Number 1 (with Ec/Io
from scanner & UE at time of
drop)
Drop Call 1 (UE vs.
scanner best server)
Handover analysis
Handover analysis
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compare Ec/Io from both scanner and UE at thetime of the drop: the UE Ec/Io to drop to < -21 dB while the scanner
remained above -11 dB.
Comparing the best servers from the UE and thescanner at the time of drop: for the scanner and UE SC008 is the best server prior
to the drop. However, about 30 seconds before the
drop, the scanner selected SC018 as the best serverwhile the UE continued to have only SC009 in itsactive set resulting in the drop call. Immediately afterthe drop, the UE camps on SC018.
Handover analysis
Handover analysis
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Drop Call Number 1 (Active & monitored sets at time of drop)
Handover analysis
Handover analysis
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Examining the UE Active and Monitored set: does not show SC018 to be measured by the UE
prior to the drop. This scenario resembles a missingneighbour problem, although in this case the two cellsin question are neighboured.
It seems that the best servers changes fromSC009 to SC011 and then to SC018 were toofast for this UE to perform soft handoff on time.
Although, other UEs may have succeeded in
performing soft handoff in such conditions, it isimportant to improve the cell dominance in theaffected area.
Handover analysis
Handover analysis
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RSCP coverage from SC018 at the location of the
drop, SC018 shouldnot be the best
server...
the cells is extending
into a large area. E.g.
around the location ofdrop call, SC018
RSCP is > -75dBm
Cell SC018 clearly
requires some down
tilting to control itsinterference into the
area of Drop 1
Handover analysis
Handover analysis
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Drop Call 1 Summary:
The drop call appears to be associated with
unnecessary change of best servers caused
by excessive dominance of SC018. Toimprove the dominance in the affected area,
SC018 should be considered for downtilting
Handover analysis
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Analysis procedure
Neighbor list analysis
Coverage analysis Handover analysis
Signaling analysis
Signaling analysis
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Signaling analysis
CS Normal release procedure
Signaling analysis
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Signaling analysis
1.UE sends message RRC_UL_DIR_TRANSF to RNCIE nas message is 0325means disconnectmessage of call control sublayer in NAS layer
2.RNC sends message RANAP_DIRECT_TRANSFER
to CNIE nas message is 0325means disconnectmessage of call control sublayer in NAS layer
3. CN sends message RANAP_DIRECT_TRANSFERto RNCIE nas PDU is 832dmeans releasemessage of call control sublayer in NAS layer
4.RNC sends message RRC_DL_DIRECT_TRANSF toUEIE nas PDU is 832dmeans release messageof call control sublayer in NAS layer
Signaling analysis
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Signaling analysis
5.UE sends message RRC_UL_DIR_TRANSF to RNCIE nas PDU is 032ameans release completemessage of call control sublayer in NAS layer
6. RNC sends message RANAP_DIRECT_TRANSFER
to CNmeans release complete message of callcontrol sublayer in NAS layer
7.CN sends messageRANAP_IU_RELEASE_COMMAND to RNCstartrelease Iu interface resource
8. RNC sends messageRANAP_IU_RELEASE_COMPLETE to CN
Signaling analysis
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Signaling analysis
9.RNC sends messageRRC_RRC_CONN_REL to UEstart releaseRRC connection
10. UE sends message
RRC_RRC_CONN_REL_CMP to RNC 11.RNC sends message NBAP_RL_DEL_REQ
to Node Bstart release Iub interface resource
12. Node B sends message
NBAP_RL_DEL_RSP to RNCend the wholerelease procedure
Signaling analysis
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Signaling analysis
PS normal release procedure
Signaling analysis
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Signaling analysis
1.UE sends message RRC_UL_DIR_TRANSF to RNCIE nasmessage is 0a46, indicates message deactivate PDP contextrequest in session management sublayer.
2.RNC sends message RANAP_DIRECT_TRANSFER to CNIEnas pdu is 0a46, indicates message deactivate PDP contextrequest in session management sublayer
3. CN sends message RANAP_DIRECT_TRANSFER to RNC, IEnas pdu is 8a47, indicates message deactivate PDP contextaccept in session management sublayer.
4. CN send message RANAP_RAB_ASSIGNMENT_REQ to RNC,IE RAB list including RAB ID to point out which RAB need to bereleased.
Signaling analysis
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Signaling analysis
5. RNC sends messageRRC_DL_DIRECT_TRANSF to UE, IE nasmessage is 8a47, indicates messagedeactivate PDP context accept in session
management sublayer. 6. RNC send messageNBAP_RL_RECFG_PREP to NODEB
7. NODEB send messageNBAP_RL_RECFG_READY to RNC
8. RNC send message RRC_RB_REL to UE,start to release RB
Signaling analysis
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Signaling analysis
9. NODEB sends messageNBAP_RL_RECFG_COMMIT to RNC
10. UE sends message RRC_RB_REL_CMP to RNC, indicates the traffic RB release
completed 11. RNC sends message
RANAP_RAB_ASSIGNMENT_RESP to CN,indicates the RAB release completed
12. CN send messageRANAP_IU_RELEASE_COMMAND to RNC,start to release Iu resource: RANAP layerresource and ALCAP layer resource
Signaling analysis
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Signaling analysis
13. RNC send messageRANAP_IU_RELEASE_COMPLETE to RNC
14.RNC send message RRC_RRC_CONN_REL to UE,start to release RRC connection
15. UE send message RRC_RRC_CONN_REL_CMPto RNC
16.RNC send message NBAP_RL_DEL_REQ toNODEB, start to release Iub resource: NBAP layerresource, ALCAP layer, and PHY layer
17. NODEB send message NBAP_RL_DEL_RSP toRNC, the whole release procedure completed
Signaling analysis
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Signaling analysis
compare with the CS release procedure:
PS Step1~3 is corresponding to CS step 1~6,
to release NAS
step411 are special for PS
PS step1217 is the same as the CS step7
12
Signaling analysis
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If RSCP & Ec/Io degrades before drop for BOTHscanner and UE then check for coverage problems
If prior to the drop, the Ec/Io (and RSCP) degrades forUE ONLY while scanner shows no degradation, thenthe following checks should be made:
Is the best server for the UE is the same as that of the
scanner? (If not, its possible that the UE failed to perform softhandoff)
Does UE camp on new cell immediately after drop?
If the UE camps on a new cell after the drop, was that cellneighboured to the previous cell? (if not, consider adding thisneighbour)
Was the UE measuring this neighbour?
Were there too many and too quick changes of best servermaking it difficult for UE to perform measurements and SHOin time. (if this is the case: improve cell dominance throughantenna optimisation)
Signaling analysis
Signaling analysis
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Does the UE Tx power increase to max prior todropping call while Ec/Io level remains good? If the Tx power increase is gradual and UE is far from
site the failure is due to uplink coverage limitation
If the increase is sudden and UE may be not be toofar from site - Check uplink load from SIB7 followingdrop callis it unusually high?
If uplink load is reported to be high, confirm from networkstats that the high load is due to genuine trafficotherwise
check for a possible site fault If uplink load is not high, problem could be due to possible
power control failure.
Signaling analysis
Signaling analysis
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If the above steps do not reveal the causes of the dropcalls then analysis of the messages should be carriedout to determine the sequence of events prior to the dropcall.
If the drop call does not appear to be RF related and theRF conditions at the location of the drop appear to begood then no further work is needed as part of the RFOptimisation.
However, exact location of the drop should be marked
for later comparisons with future drive surveys (if un-explained drops keep occurring at the same location,more detailed investigation will be required to establishthe exact causes).
Signaling analysis
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