umts ssv event analysis case study.ppt

Case Study

SSV (UMTS) Event Analysis

QuadGen Wireless Solutions Inc., Proprietary

DROP due to poor RF conditions

•There is a short MOC drop due to poor RF conditions.

•SNJNPRU0751 doesn’t have a 3rd carrier. The coverage on 850 band is good but it cannot make an IFHO because it is band locked to 1900MHz band.

•Also, the handover type for PRSJU3143 is 2(none).


Drop due to poor rf conditions

• Drop is due to poor RF conditions.

•Call drop due to challenging terrain (see next slide).


drop due to 25 secs of missing messages

•25 seconds of missing messages.

•Call dropped due to missing neighbor.

•Neighbor Recommendation:GAATU61399 (SC383,UARFCN=412) ->GAATU61402 (SC399,UARFCN=1087).


Loss of synchronization

• There is a Loss of synchronization between the base station and the UE.

• UE is continuously trying to add PRSJU32019 (SC 337) in its active set (It is verified that it is defined as the neighbor of PRSJU32018( SC312)).


7 seconds of missing messages

•There are 7 seconds of missing messages.

•This is a known issue with CSR # 143 0999.


Due to missing neighbour

•Cells in detected neighbor list have better EcNo and RSCP than cells in AS. •Event e1a is continuously triggered to add SC391 but it is not a defined neighbor.• UE is entering a new cell(SC391) and causing UL interference to the other UE’s connected to this cell. Thus, Call is released in the downlink.•Neighbor recommendation (Intra frequency):SNJNPRU07717 (SC217)-> SNJNPRU02458 (SC391).


Due to missing neighbour

•The drop is due to poor RF conditions in UARFCN=412 (1900 band) and missing neighbor.

•Neighbor recommendation: GAATU23599 (SC=263, UARFCN=412)->GAATU23501 (SC=483, UARFCN=1087).


Due to too many servers

•EUL drop is due to too many servers with no dominant server available.

•Recommendation:Electrical uptilt of GAATU23503 by 2 degree.


Measurement control failure

•EUL drop occurs due to measurement control failure.

•In downlink, UE is asked to measure UARFCN=412, but it fails to perform it.

• As UARFCN 412 is the 4th carrier which corresponds to femto cells, but UE has the limitation of measuring only 3 frequencies.


Normal release (rrc req. for registration)

•The RRC request is for the purpose of registration.

•Normal release is being pegged as an access failure in Actix.


App drop due to winsock error

• HSDPA application drop is due to Winsock error as no route is found from server to client.

• The application drop is occurring when the UE is latched to UARFCN=437.


MOC


moc access failure

•Normal release is being pegged as an access failure by Actix.

•It took place due to a change from UMTS to GSM mode at MT end due to high qRxlevmin.

•At the MT end, location update of GSM mode was not yet completed, that’s why it couldn’t respond to any incoming MO call.

MTC Tech Mode

MTC Protocol stack browser

MOC RSCP

MOC Protocol stack browser


MTC


Mtc Access failure


•Call terminated at the end of the log file.


MTC AF # 2

Core network releases access failure as a normal event.

In paging, IMSI is paged instead of TMSI.


CS LONG


CS Long access failure


•This access failure occurs due to unavailability of resources.


Cs long call drop

•Call drop occurs on UARFCN=437.

•Poor RSCP and EcNo.

•Multiple events 1a are triggered but can not be executed.

•Swapped feeder issue between ILU22228 (SC508) and ILU22229 (SC20) (refer to next slide).


Swapped feeder (ilu2222)

• Co-located site ILU2222 has its feeder for SC20 and SC508 swapped.

RSCP plot for Sc 508 RSCP plot for Sc 20


HSDPA


HSDPA drop *

• Multiple cell update messages sent in uplink but there is no cell update confirm message in downlink.

•Timers t314 and t315 expire during Cell update (uplink) in the cell_FACH state, hence goes to idle state.


HSDPA DROP (Physical channel reconfiguration failure)

• After active set update is complete, in DL Measurement control message, it asks for “ Intra frequency measurement” ,but in physical channel reconfiguration message the RNC is giving freq. info corresponding to UARFCN=4384.•As UE is locked to 1900 band, it can not measure UARFCN=4384 resulting in physical channel reconfiguration failure.


HSDPA drop

•HSDPA drop occurred due to temporary UE issue.

•There were many RRC Connection setups in the DL in between an ongoing call.

•It was in FACH state for a long time, so RRC connection was released.


Hsdpa app. download time ERROR

• Both the application download time events are at the same location as the driver tester has stopped there.

• The get time exceeds 120 secs because of low RSCP at that location.

•As the location is on a highway if the drive tester was moving he could have easily moved to better RF coverage area.


EUL


EUL Drop

• The EUL drop is occurring in good RF conditions.

• Validation of drive is required.


EUL DROP

•Event is falsely pegged by actix as a EUL drop. Here, a new RRC connection request is detected as a drop by Actix as previous RRC connection was not released.

•RRC connection request is for an interactive call to continue the FTP file transfer session of the previous EUL call.


Eul drop

Analysis:

Temporary network issue.

There is a paging type 2 message for terminating the background call during the current ongoing call which was responded to by UE.


Eul APP. UPLOAD TIME error

App. UL Throughput

•Application upload exceeds 120 seconds due to poor uplink throughput.

• Poor uplink throughput is due to missing neighbor.

•Neighbor recommendation: GAATU23599 (SC=263, UARFCN=412)->GAATU23501 (SC=483, UARFCN=1087).


Eul irat ho fail

•IRAT HO failed due to physical channel failure.

•Missing neighbor.

•Neighbor recommendation: GAATU23662(SC 327, UARFCN=1087)-> GA6139A (ARFCN=246),

GAATU61397(SC 367, UARFCN=1087)-> GA6139A (ARFCN=246).


IRAT HO


Definition , Why use Irat ?

Definition:Inter-system handover is a Ho between GSM and WCDMA

networks and vice versa.

Why: Integrate both systems as one network and guarantee that the

services will not be disrupted when a customer moves in the coverage area. The used GSM and WCDMA radio access layers need to integrate and operate as one seamless cellular network.


Strategy - Example

GSM_preferred

GSM_preferred

GSMGSMGSMGSM GSM GSM GSMGSM GSM

UTRAN

GSMIdle modeConected mode

NoneNoneNone None None


Irat Process


Connection Monitoring

- Check if current DL and UL coverage is good.

How : Monitoring the Connection in DL and UL

DL : CPICH Ec/No and CPICH RSCP : 2d and 2f

UL : UE TX power : 6d and 6b


Compressed Mode events

2d event trigger: usedFreqThresh2dEcno+ serviceOffset2dEcno Or usedFreqThresh2dRscp+ serviceOffset2dRscp.

2f event trigger:usedFreqThresh2dEcno+ serviceOffset2dEcno+ usedFreqRelThresh2fEcno and usedFreqThresh2dRscp+serviceOffset2dRscp+usedFreqRelThresh2fRscp

6d event trigger:UE Tx Power reaches maximum during timeToTrigger6d6b event trigger:ueTxPowerThresh6b


Compressed Mode

Action2: UE exits Compressed Mode and stops measuring IRAT/IFHO neighbors

Action1: UE enters Compressed Mode and starts measuring IRAT/ IFHO neighbors


Irat Events

3a event trigger:usedFreqThresh2dEcno+ serviceOffset2dEcno+ utranRelThresh3aEcno

orusedFreqThresh2dRscp+ serviceOffset2dRscp+ utranRelThresh3aRscp

and gsmThresh3a


ParametersusedFreqThresh2dEcno-UtrancellserviceOffset2dEcno-UeRcusedFreqThresh2dRscp-UtrancellserviceOffset2dRscp-UeRcusedFreqRelThresh2fEcno-UeMeasControlusedFreqRelThresh2fRscp-UeMeasControltimeToTrigger6d-UeMeasControlueTxPowerThresh6b-UeMeasControltimeTrigg6b-UeMeasControlutranRelThresh3aEcno-UeMeasControlgsmThresh3a-UeMeasControl


Troubleshoot

Phases

- Preparation Phase

- Execution Phase

- Confirmation Phase


Troubleshoot


Troubleshoot

Failures in the Preparation PhaseOnce the RNC determines that a handover to 2G is necessary, it contacts the 2G Network via the 3G MSC and starts a timer. If the 3G MSC comes back with a negative response or if the timer expires before the 3G MSC comes back with a response, then the handover is considered unsuccessful

Failures in the Execution PhaseIf after receiving the handover command from the RNC the UE cannot make it on the 2G network, it will try come back to the 3G network and will advise the RNC that the handover was unsuccessful

Failures in the Confirmation PhaseIf the RNC does not receive confirmation from the 2G network that the handover was successful and it does not hear back from the UE, the handover is considered unsuccessful (IRAT drop)


Troubleshoot

Failures in the Preparation Phase Majority of Problems due to “Relocation Failure in Target CN/RNC or Target System”. Typically indicates incorrect data in external GSM table (i.e. 3G MSC sends a cell ID that the 2G MSC does not know about). For this failure, an audit of the UTRAN target GSM cell information is recommended.

Failures in the Execution Phase Majority of the problems may be associated “Physical Channel Failures” and these failures could be related to:• Co-BCCH/BSIC ambiguity• Missing GSM neighbor• GSM NL too long (NL selection truncates important GSM neighbors)• GSM target cell quality degradation (degrades significantly so that IRAT handover was not able to complete)


Thank You

umts ssv event analysis case study.ppt

Documents

missing neighbor

defined neighbor

neighbourthe drop

serverseul drop

poor rf conditionsthere

detected neighbor list

neighbor of prsju32018

proprietarynormal release