C08 WCDMA RNO Drop Call Analysis

8/10/2019 C08 WCDMA RNO Drop Call Analysis

1/56

0 2014/12/1 Huawei Profile

Drop-call Analysis


2/56


Analysis procedure

Neighbor list analysis

Coverage analysis

Handover analysis

Signaling analysis


3/56


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


4/56


analysis procedure

Drop call event definition:


5/56


analysis procedure

Drop call analysis procedure


6/56


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.


7/566 2014/12/1 Huawei Profile

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



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



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



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



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



Analysis procedure


Coverage analysis

Handover analysis

Signaling 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.




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




Dropcall position




Active set and monitor set information




Radio parameters information




CPICH EcIo Compare between scanner and UE




CPICH RSCP compare between scanner and UE




SC compare between scanner and UE


21/56



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


22/56


Analysis procedure


Coverage analysis Handover analysis

Signaling analysis


23/56


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


24/56


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


25/56


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


26/56


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


27/56


Coverage analysis

Dropcall position

C l i


28/56


Coverage analysis

Active set and monitor set information

C l i


29/56


Coverage analysis

Radio parameters information

C l i


30/56


Coverage analysis

CPICH Ec/Io

C l i


31/56


Coverage analysis

CPICH RSCP


32/56


Analysis procedure



Signaling analysis

H d l i


33/56


Handover analysis

Handover type:

Intra-freq HO

Inter-freq HO

Inter-RAT HO

insufficient handover area

ping-pang handover

H d l i


34/56


Handover analysis

Signal strength change

Handover analysis


35/56


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


36/56


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


37/56


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


38/56


Drop Call Number 1 (Active & monitored sets at time of drop)

Handover analysis

Handover analysis


39/56


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


40/56


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


41/56


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


42/56


Analysis procedure



Signaling analysis

Signaling analysis


43/56


Signaling analysis

CS Normal release procedure

Signaling analysis


44/56


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


45/56


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


46/56


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


47/56


Signaling analysis

PS normal release procedure

Signaling analysis


48/56


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


49/56


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


50/56


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


51/56


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


52/56


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


53/56


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


54/56


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


55/56


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


56/56

C08 WCDMA RNO Drop Call Analysis

Documents

Transcript of C08 WCDMA RNO Drop Call Analysis