Transcript RNO Wind

RNO Wind
Part II
Confidential
1
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
Part II - Content
Retainability
Drop cause relevance
Compress Mode
CM Time
IRATHO
Adjg Optimization
Failure analisys
Confidential
2
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
Retainability
Confidential
3
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
Retainability
Drop call (from 3G RNC side) can occur when UE is leaving the 3G layer (during intersystem HO) or in 3g layer.
It is not easy to find clear relationship between drop call in 3g layer and active set size or
SHO success rate.
Considering WCELs with high permanence in “one cell in active state” (greater than 90%
weighted value) no more than 50% suffer drop call value greater than 1% and increasing
to higher value statistical data does not confirm the cause – effect relationship.
Same behaviour is revealed for SHO success rate KPI.
At the same way is not possible to find direct relationships between intersystem mobility
failure procedure and high value of drop call.
The reason for that has to be seek in the masking effect of the counters involved either
SHO or Active Set Size or in the IRATHO success rate KPIs
Drop call analisys have to be performed with a second level analisys taking into count
that an averall improvement should come from ADJS and ADJG optimization
Confidential
4
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
RAB & RRC Active Failures
RAB and RRC active failure reasons:
•
•
•
•
•
•
RNC Internal
BTS
UE (for user perspective)
Radio Interface
Iur
Iu
UE
RNC
CORE
RAB Assignment Request (setup)
Radio Bearer Setup
Radio BearerSetupComplete
RAB and RRC normal release:
RAB Assignment Response
•
•
•
•
RAB active complete
Pre-emption
SRNC Relocation
Unspecific error in CN (RAS05.1)
Confidential
5
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
RAB Assignment Request (release)
Iu Release Command
RAB Assignment Response
Iu Release Request
RAB & RRC Active Failures
By a RNO point of view the drop due to lack of radio resources are the most important.
Iu, Iur and RNC failure causes are neglected because the dimensioning should assure about it and out
of RNO scope
Fail due to congestion has to be intended as caused by shortage of resources or not appropriate air
interface.
In the following two KPIs to evaluate the drop cause that can be optimized:
RRC Drop Rat io
RRC_CONN_ACT _FAIL_RADIO 
100
RRC_CONN_ACT _FAIL_BTS
RRC_CONN_ACT _COMP RRC_CONN_ACT _REL_P _E
MP 
%
RRC_CONN_ACT _REL_SRNC  RRC_CONN_ACT _REL_UNSP EC_CN
RRC_CONN_IN_REF_CELL RRC_CONN_OUT _REF_CELL 
RRC_CONN_ACT _FAIL_IU RRC_CONN_ACT _FAIL_RADIO 
RRC_CONN_ACT _FAIL_BTS  RRC_CONN_ACT _FAIL_IU
R
RRC_CONN_ACT _FAIL_CIP H  RRC_CONN_ACT _FAIL_I_
CHK 
RRC_CONN_ACT _FAIL_RNC  RRC_CONN_ACT _FAIL_UE
RAB Drop Ratio,AMR Voice
RRAB_ACT _FAIL_CS_VOICE_RADIO
100
RAB_ACT _FAIL_CS_VOICE_BT S
RAB_ACT _COMP_CS_VOICE  RAB_ACT _REL_CS_VOICE_P_EMP
RAB_ACT _REL_CS_VOICE_SRNC  RAB_ACT _REL_CS_V_UNSPE_ER_CN
RAB_CS_VOICE_IN_REF_CELL - RAB_CS_VOICE_OUT _REF_CELL 
RAB_ACT _FAIL_CS_VOICE_UE RAB_ACT _FAIL_CS_VOICE_IU
RAB_ACT _FAIL_CS_VOICE_RADIO RAB_ACT _FAIL_CS_VOICE_BT S
RAB_ACT _FAIL_CS_VOICE_IUR RAB_ACT _FAIL_CS_VOICE_I_CHK
RAB_ACT _FAIL_CS_VOICE_RNC
Confidential
6
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
%
RAB & RRC Active Failures
The retainability KPI does not take into account RRC-connections that move successfully through
the cell, they only count drop ratio of RRCs that were released in the cell. In this way the drop KPI
shows a bit too high values.
Generic Drop Call KPI does not take into count the following scenario:
Successful RRC Setup ->
RRC_CONN_ACC_COMP is
updated
RRC Drop here causes
RRC_CONN_ACT_FAIL_xx to be
incremented and not
RRC_CONN_ACT_COMP is
incremented
To overcome this problem, new counters are implemented in RAS05.1 that are updated when the
reference cell changes
M1001C443 RRC_CONN_OUT_REF_CELL - The number of RRC Connections that have left
from the old reference cell
M1001C466 RRC_CONN_IN_REF_CELL - The number of RRC connections that enter a new
reference cell
In this context term “reference cell change” means the cell that e.g. M1006 RRC counters are
updated and that is used as stop_bts when pmi_ticket
In Cell-FACH state the reference cell is the cell in which the UE is listening to the FACH channel
Confidential
7
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
RAB & RRC Active Failures
Separating the numerator it is possible to
have two separate KPIs for radio and BTS.
This allows to differentiate the action
required:
Start
DC due to congestion
Radio
Yes
Radio?
coverage plot , dominance must be verified
RNP data anlisys
Load analisys
indication from UL/DL Load KPI (see PartI)
BTS
Yes
BTS?
CE upgrade
HW check
End
Confidential
8
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
HW & CE resource must be checked using
KPI for CE and codes
Compress Mode
Confidential
9
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
Compressed Mode Selection
CM is used to create idle periods (gaps) in the transmission during which ncell measurements on
another
system can be made
Measurement gap
Power / Data
Rate
Compressed
Mode
Normal fra\\me
Normal frame
Normal frame
Gaps can be created using single or double frame approach (Nokia supports both)
Because same data amount is sent in a shorter time => affects WCDMA coverage
Fast Power control information might be lost during the gap => higher Eb/No => affects WCDMA capacity
Compressed frames may be lost if power control is not set correctly => affects WCDMA quality
CM methods are Spreading Factor Halving and Higher Layer Scheduling
Confidential
10
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
Compressed Mode Selection
Selection of the compressed mode method is performed in the following way:
SF/2 used for both UL and DL
AMR, RT PS or
CS data service
Transmission Gap Pattern:
Single frame: 7 slot gap,
variable # of normal frames
Higher layer scheduling is
Used for both UL and DL
NRT PS data service
Transmission Gap Pattern:
Selection between HLS ½ and
HLS ¾
Single frame: 7 slot gap,
# of normal frames
Confidential
11
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
Double frame: 7 slot gap,
# of normal frames
CM Time
The following counters are available for the CM procedure monitoring
M1002C437 ALLO DURA FOR COM MODE UL USING SF/2 METHOD IN SRNC /
M1002C433 ALLO FOR COM MODE UL USING SF/2 METHOD IN SRNC
M1002C438 ALLO DURA FOR COM MODE DL USING SF/2 METHOD IN SRNC /
M1002C434 ALLO FOR COM MODE DL USING SF/2 METHOD IN SRNC
M1002C440 ALLO DURA FOR COM MODE DL USING HLS METHOD IN SRNC /
M1002C436 ALLO FOR COM MODE DL USING HLS METHOD IN SRNC
M1002C439 ALLO DURA FOR COM MODE UL USING HLS METHOD IN SRNC /
M1002C435 ALLO FOR COM MODE UL USING HLS METHOD IN SRNC
Dividing the duration by the respective allocation is possible to have an estimation of
the CM Time
The approaching of the limit GSMMeasRepInterval * GSMMaxMeasPeriod
can be considered as an indication for the tunig of the related parameters
Time for cell search and for CM can be tuned as well
Confidential
12
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
CM Time
After HO triggering condition is fulfilled a RRC message ”Measurement Control” is sent to UE
containing details of the measurement that the UE must execute.
RRC: ”Measurement control ” message (GSM RSSI measurements)
RNC
UE
The neighbour cell search is regulated by the GSMNcellSearchPeriod period parameter. ISHO is
not allowed until the are enough measurement reports given by this parameter (O means that only 1
measurement result is enough for decision making)
Duration of the cell search period is calculated by:
GSMRepInterval * GSMNcellSearchPeriod
Confidential
13
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
CM Time
Upon reception of the measurements reported by the UE, RNC applies a sliding averaging window to
theRXLEV measurements. The averaged levels are used as input to the IS-HO decision algorithm.
GSMMeasAveWindow
UE
GsmMeasRepInter
val
RRC: ”Measurement report”
RRC: ”Measurement report”
is the interval between
measurement reports, which
are sent to BTS
Confidential
14
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
RNC
is Measurement Averaging
Window size, sliding window
is used
The first measurement report
has info from the best GSM cell:
BCCH freq & RSSI, no filtering
used in UE
RXLEV measurements are reported through
”Measurement report” messages
CM Time
In case of an unsuccessful IS-HO attempt, the network will deactivate compressed mode for a time
period given by GSMMinMeasInterval
WBTS
RNC
NBAP: Compressed Mode Command
GSMMinMeasInterval
This is Minimum Measurement
Interval, wait time when the
following CM starts.
NBAP: Compressed Mode Command
If the RNC is not able to execute an inter-system Handover, it shall stop the inter-system
measurements after the UE has sent the predefined number of measurement reports to the RNC,
given by GSMMaxMeasPeriod
The Maximum allowed duration of the inter-system measurement is calculated:
GSMMeasRepInterval * GSMMaxMeasPeriod
Confidential
15
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
[ es:0.5*20 =10s,]
CM Time
The CM time should
never approach the max
limit stated by
Start
CM Time
approach max?
CM Time
approach min?
Yes
System stable
The best cndition is to
perform the IS with the
minimum time
Yes
Verify
# No Cell Found
Yes
High # No
Cell Found?
CM tuning
© Nokia Siemens Networks
GSMRepInterval *
GSMNcellSearchPeriod
without failure.
Yes
New ADJG
availale?
1E/1F tuning
Confidential
16
GSMMeasRepInterval *
GSMMaxMeasPeriod
RNO / Wind 17/10/2007 - NMI
Add ADJG
In the other cases ADJG
optimzation or tunig of
parameters are required
IRATHO
Confidential
17
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
IRATHO
As M1013 described in PartI, M1015 return statistic for intesystem HO. The filtering criteria
can be replicated with the exception of ping-pong
Filtering criteria:
Major
- High number of failures for a defined out-going adjg (failure ADJG)
- high number of fail for a defined source (failure WCEL)
Minor
- very low number of attempt with failure (low used adjg)
- zero number of attempt for declared adjs– stabilized value (no adjg)
- high number of attempts for an out-going adjs (unbalanced ADJG)
out-going condition is sufficient
- high number of attempts for a defined source (unbalanced WCEL)
Same procedures can be applied to the case considering that the event related are 1E and 1F
Confidential
18
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
1E/1F Events for CPICH Ec/No and RSCP
HHoEcNo(RSCP)Thres
hold
e.g. P-CPICH Ec/No
HHoEcNo(RSCP)Cancel
Cell 1
Defines the threshold of Ec/No(RSCP)
that must be exceeded by a measurement
of an active set cell to be canceled the
event 1F related
Cell 2
determines the absolute CPICH
Ec/No threshold which is used by the
UE to trigger the reporting event 1F.
When the measured CPICH Ec/No of
all active set cells has become worse
than or equal to the threshold in
question, the RNC starts interfrequency or inter-RAT (GSM)
measurements in compressed mode
for the purpose of hard handover.
Cell 3
1F
1E
time
HHoEcNo(RSCP)CancelTime
determines the time period during which the CPICH
RSCP of the active set cell must stay better than the
threshold HHoRscpCancel before the UE can trigger the
reporting event 1E.
Confidential
19
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
HHoEcNo(RSCP)TimeHysteresis
determines the time period during which the CPICH Ec/No of the active
set cell must stay worse than the threshold HHoEcNoThreshold before
the UE can trigger the reporting event 1F.
IRATHO – Triggering reason
1. Low measured absolute
CPICH Ec/No, event 1E/1F
2 . Low measured absolute
CPICH RSCP, events 1E/1F
FMCG: GSMcauseCPICHEcNo
FMCG: GSMcauseCPICHrscp
Triggering reason gives
3. UE Tx power approaches
its maximum allowed
power, event 6A/6D
an indication
4. DL DPCH approaches its
maximum allowed power
FMCG: GSMcauseTxPwrDL
FMCG: GSMcauseTxPwrUL
5. Quality deterioration report
from UL outer loop PC
6 . Others
- Load and Service based HO
- IMSI based HO
- Emergency ISHO
FMCG: GSMcauseUplinkQuality
GSMcauseX
These parameters indicates whether a handover to GSM caused by low measured absolute CPICH Ec/No of the serving cell is
enabled (1)
Confidential
20
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
IRATHO – Triggering reason
It’s important to know which is the most frequent triggering reason:
It’s possible to diffentiate between quality and coverage reasons and understand the
network limiting factors:
1.
CPICH coverage
2.
Pilot pollution
3.
UL/DL Service coverage
In actual case is possible to dsciminate between low CPICH coverage triggered by high# RSCP
attempts or probable pilot pollution triggered by high # Ec/No attempts
A KPI that gives reason for that is
xxx _ Cause _ perc 
IS _ HHO _ W _ CMOD _ xxx _(N ) RT
 IS _ HHO _ W _ CMOD _ xxx _(N ) RT
Allcauses
Confidential
21
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
IRATHO – Triggering reason
Enabling all the causes a screaning on the network is returned individuating the limiting factor
and the required action.
Start
Yes
High # Ec/No?
DL interference/ Pollution
should be evaluated
DL Qual limiting
DL
Yes
High # RSCP?
CPICH power analisys/ new
site required
DL level limiting
Yes
High # UE
New site required or new
UL level limiting
Parametrization for IRATHO
Tx pwr?
UL
Yes
High # UL Qual?
UL qual limiting
Load analisys and UL
interference evaluation
Service limiting
New planning for service is
required
End
Yes
High # DL
DPCH?
Confidential
22
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
This condition
should be the
dominannt one
without
associated
failure
IRATHO - Failure
UE
Node B
CN
RNC
RRC: Measurement Control
ISHO triggering
(5 reasons are
possible)
RRC: Measurement Report
Failure can happen
at different point:
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
NBAP: Radio Link Reconfiguration Commit
RRC: Physical Channel Reconfiguration
Initial
Compressed
Mode
Configuration
NBAP: Compressed Mode Command
RRC: Measurement Control
RRC: Measurement Report
GSM RSSI
Measurement
RANAP: SRNS Context Request
RANAP: SRNS Context Response
RANAP: SRNS Data Forward Command
RANAP: IU Release Command
RANAP: IU Release Complete
Confidential
RNO / Wind 17/10/2007 - NMI
- Measuring GSM
cell
After decision
RRC: Cell Change Order from UTRAN
© Nokia Siemens Networks
- Before CM
- During CM
RRC: Physical Channel Reconfiguration Complete
23
Before decision
- Drop
Utran and ue have to
treated as particular
case
CM not possible
UE
RNC
BTS
AC is responsible for checkiing if CM is possiblle
RRC: Measurement Control
RRC: Measurement Report (3,4,5)
If CM fails one of the following mus be checked:
Admission Control
check for CM
Not enough resources – AC reject CM.
Evaluate interference
Expand capacity
(see PartI)
The following KPI gives an indication of the number of CM
procedure not started
NBAP: Radio Link Reconfiguration Prepare
NBAP: Radio Link Reconfiguration Ready
NBAP: Radio Link Reconfiguration Commit
RRC: Physical Channel Reconfiguration
RRC: Physical Channel Reconfiguration Complete
RX Level measurement phase for
all ISHO neighbours
NBAP: Compressed Mode Command
RRC: Measurement Control
RRC: Measurement Report
NBAP: Compressed Mode Command
BSIC verification phase for target cell
RRC: Measurement Control
IS_COM_MOD_ST A_NOT _P
OS
IS_COM_MOD_ST A_NOT _P
OS   IS_HHO_W_CMODj
RRC: Measurement Report
j
Considering that M1010C2 (INTER SYST COM MOD STA NOT POS FOR RT) is updated if it is
not possible to start inter-system compressed mode measurement due to radio resource
congestion, BTS- or UE-related reasons to have a better insight on radio congestion it could be
better to use, e.g. for UL the M1002C361 REQ FOR COM MODE UL REJECT TO INT SYST HHO
IN SRNC and the M1002C357 REQ FOR COM MODE UL TO INT SYST HHO IN SRNC and use the
following :
M1002C361/M1002C357
Confidential
24
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
NO Cell Found
… measurement
fail
No Cell Found
Counters
NO Cell Found means:
there is no suitable gsm target cell in terms of RX Level
OR
Compressed
Mode start
the target gsm is suitable but its BSIC verification fails
AND
the maximum number of measurement reported are received
AND
HHO Attempt
Counters
… measurement not
fail
maximum measurement interval is not expired
The following KPI gives an indication of the number of GSM cell not found
ISHO_ Meas _ Fail _ Rate 
 IS _ HHO _ NO _ CELL _ xxx _(N ) RT
 IS _ HHO _ W _ CMOD _ xxx _(N ) RT
Allcauses
Allcauses
Missing ADJG could be the reason or a dedicated parameter tuning for the 1F event.
The KPI can be madified taling care of the WO_CMOD events
Confidential
25
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
NO Cell Found
Start
High #
End
NO Cell?
Yes
Yes
GSMCause=Ec/
Nol?
New site
Good GSM coverage
in the far field?
Verify
ADJG
ADJG
Addition?
Coverage anlisys
Yes
Good GSM coverage
in the near field?
Yes
Reduce
End
“thershold”
Confidential
26
required
Pollution evaluation
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
Reduce “Cancel”
Increase “Time hysteresis”
DROP & UNSUCCESS IRATHO
Optimization for unsuccess is not possible
because the reason are:
UTRAN Failure
Counter
- physical channel failure (the UE is not able to
establish the phy.
- Protocol error
UE Failure
Counter
- Inter-Rat protocol error
- Unspecified
Drop are related to drop call occurred
during the procedure
HHO Attempt
Counters
ISHO Unsuccess
Counters
ISHO_ Drop _ Rate 
 CON _ DRPS _ IS _ HHO _ xxx _(N ) RT
 IS _ HHO _ ATT _ xxx _(N ) RT
Allcauses
Allcauses
ISHO Success
Counters
RRC Drop
Counters
Confidential
27
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI
In this case the optimization is required and
pass through the evaluate of GSM and 3G plot
coverage. Optimize If necessary number of
ADJG or NWP parameters otherwise tune
RNW parameters.
Thresholds can be relaxed to favourite an
early exit from 3G layer
3G –> 2G Unbalancing
This topic present the inherent problem due to the fact that the 2G layer is not involved in
the analisys.
Few consideration can be performed under some assumption:
The following KPIs used over a cluster for CS voice service gives the percentage of the CM
started over all the RAB, giving an idea of the attempted mobility procedure requested for a
cluster where the 3G coverage should be assured
Perc _ Voice _ Call _ ISHO 
 IS _ HHO _ ATT _ xxx _ RT
Allcauses
RAB _ ACC _ COMP _ CS _ VOICE
Better to use completes: failures, normal & SRNC reloc on denominator and use the KPI inside the
3G cluster or difining a polygon where 3G service is required
Once Correlated with voice drop due to radio link failure and rrc drop during ISHO, the KPI can
help operator in understand the ISHO strategy. Similar KPI is possible for PS
Threshold to shrink the HO area or inhibit the procedure has to be setted
Confidential
28
© Nokia Siemens Networks
RNO / Wind 17/10/2007 - NMI