WCDMA GSM Mobility
Slide 1
Nokia Networks
NokiaEDU
WCDMA GSM Mobility
RN3706 – 16A
Multi-Layer Optimization [WCDMA16]
RN37062EN16GLA0
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WCDMA GSM Mobility
Slide 2
Copyright and confidentiality
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WCDMA GSM Mobility
Slide 4
Module Objectives
At the end of the module you will be able to:
• Perform the parameter and performance audit for existing WCDMA-GSM load
balancing features
• Perform the parameter and performance audit for existing ISHO features
• Summarize common practice for WCDMA-GSM interworking and propose optimization
activities
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WCDMA GSM Mobility
Slide 5
Content
WCDMA-GSM Mobility
- WCDMA-GSM Mobility
- WCDMA-GSM ISHO Introduction
- Parameter Verification & Recommendations
- ISHO Performance Analysis
- GSM-WCDMA Mobility
- Main Process & Parameters
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WCDMA GSM Mobility
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Content
WCDMA-GSM Mobility
- WCDMA-GSM Mobility
- WCDMA-GSM ISHO Introduction
- Parameter Verification & Recommendations
- ISHO Performance Analysis
- GSM-WCDMA Mobility
- Main Process & Parameters
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WCDMA GSM Mobility
Slide 7
WCDMA-GSM ISHO Introduction
WCDMA - GSM interworking mobility - Introduction
WCDMA GSM ISHO features
“basic” GSM ISHO features
GSM system can be also target for Load and
Service based HO. SLHO parameter check
including GSM part (activation) is included
WCDMA Layering chapter.
Besides Inter-System HO features, RAN147
RRC Connection setup redirection can used to
move UE to GSM in case of congestion in
WCDMA cell. (target cell for next attempt can
be GSM or other WCDMA frequency)
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Feature ID
Feature Name
RAN1.5009
WCDMA-GSM ISHO
RAN1275
ISHO Cancellation
RAN1758
Multiple BSIC Verification
RAN3218
Enhanced Cell Change from HSPA to
2G (WCDMA16 feature)
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WCDMA GSM Mobility
Slide 8
WCDMA-GSM ISHO Introduction
WCDMA - GSM interworking Mobility - Introduction
Initiate Compress Mode, Configure
GSM Measurements
• Handovers from WCDMA to GSM are performed mainly
due to coverage reasons, however ISHO from 3G to 2G
can also trigger based on:
• Load and Service based HO
UE Reports GSM RSSI Measurements
GSM cell meet
HO condition
• IMSI based HO
• Emergency ISHO
Is BSIC verification
required for PS
Call?
• BTS Power saving mode
Initiate Compress Mode, Configure
GSM Measurements
UE Reports GSM BSIC measurements
Initiate Handover
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WCDMA GSM Mobility
Slide 9
Content
WCDMA-GSM Mobility
- WCDMA-GSM Mobility
- WCDMA-GSM ISHO Introduction
- Parameter Verification & Recommendations
- ISHO Performance Analysis
- GSM-WCDMA Mobility
- Main Process & Parameters
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WCDMA GSM Mobility
Slide 10
Parameter Verification & Recommendations
HSPA CM support
for ISHO is
WCDMA16 feature
ISHO Configuration
RNFC
ISHOCancellation
RNC
WCEL
RNMOBI
GSM ISHO/ISHO Cancellation
parameters.
Blue = GSM ISHO parameters
White = ISHO Cancellation
parameters
GsmHandoverAMR
GsmHandoverCS
GsmHandoverNrtPS
GsmHandoverRtPS
EnableULQualDetRep
ULQualDetRepThreshold
MaxNumISHOClPerAS
HOPG
AdjgPriorityCoverage
AdjgRxLevMinHO
AdjgTempOffset1
HOPGId
FMCS
HHoEcNoThreshold
HHoEcNoCancel
HHoEcNoCancelTime
HHoEcNoTimeHysteresis
HHoRscpThreshold
HHoRscpCancel
HHoRscpCancelTime
HHoRscpFilterCoefficient
HHoRscpTimeHysteresis
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WBTS
BTSSupportForHSPACM
FMCG
FMCGId
GSMcauseCPICHEcNo
GSMcauseCPICHrscp
GSMcauseTxPwrDL
GSMcauseTxPwrUL
GSMcauseUplinkQuality
DLDPCHTxPwrClOffset
ISHOClcauseCPICHEcNo
ISHOClcauseCPICHrscp
ISHOClcauseTxPwrDL
ISHOClcauseTxPwrUL
GsmDLTxPwrThrAMR
GsmDLTxPwrThrCS
GsmDLTxPwrThrNrtPS
GsmDLTxPwrThrRtPS
GsmMaxMeasPeriod
GsmMeasAveWindow
GsmMeasRepInterval
GsmMinHoInterval
GsmMinMeasInterval
GsmNcellSearchPeriod
GsmUETxPwrFilterCoeff
GsmUETxPwrThrAMR
GsmUETxPwrThrCS
GsmUETxPwrThrNrtPS
GsmUETxPwrThrRtPS
GsmUETxPwrTimeHyst
NrtFmcgIdentifier
RtFmcgIdentifier
HSDPAFmcgIdentifier
RTWithHSDPAFmcgIdentifier
HHoMaxAllowedBitrateUL
HHoMaxAllowedBitrateDL
ADJG
ADJGId
ADJGType
AdjgBCC
AdjgBCCH
AdjgBandIndicator
AdjgCI
AdjgLAC
AdjgMCC
AdjgMNC
AdjgMNCLength
AdjgNCC
AdjgTxPwrMaxTCH
NrtHopgIdentifier
RtHopgIdentifier
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WCDMA GSM Mobility
Slide 11
Parameter Verification & Recommendations
ISHO Configuration
CPICH RSCP (Event 1F/1E)
Thresholds:
HHoRscpThreshold
HHoRscpCancel
L3 filter: HHoRscpFilterCoefficient
Timers:
HHoRscpTimeHysteresis
HHoRscpCancelTime
UE Tx Power (Event 6A/6D)
Threshold:
GsmUETxPwrThrXX
L3 filter: GsmUETxPwrFilterCoeff
Hysteresis margin:
GsmUETxPwrTimeHyst
Data rate threshold
HHOMAxAllowedBitrateUL
CPICH Ec/Io (Event 1F/1E)
Thresholds:
HHoEcNoThreshold
HHoEcNoCancel
L3 filter:
EcNofilterCoefficient
Timers:
HHoEcNoTimeHysteresis
HHoEcNoCancelTime
DL DPCH power
Threshold:
GsmDLTxPwrThrXX
Data rate threshold
HHOMAxAllowedBitrateDL
2. GSM measurement reporting
UL Quality
Threshold:
GSMcauseUplinkQuality
Timer
ULQualDetRepThreshold
Data rate threshold
HHOMAxAllowedBitrateUL
GsmMeasRepInterval
GsmNcellSearchPeriod
GsmMinMeasInterval
GsmMaxMeasPeriod
(XX=AMR,CS,NrtPS,RtPS)
3. Decision Algorithm
AdjgTxPwrMaxTCH
AdjgRxLevMinHO (n)
GsmMeasAveWindow
1. Triggering
2. GSM measuring
3. Decision
Handover Execution
2G-to-3G back prevention
GsmMinHoInterval
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WCDMA GSM Mobility
Slide 12
Parameter Verification & Recommendations
ISHO Parameters - Recommendations
ISHO configuration depends on network configuration, design and strategy, some
example values for RSCP and EcNo thresholds below.
 Use Different FMCS sets for RT, NRT and HSDPA
Parameter
HHoEcNoThreshold
HHoEcNoCancel
HHoRSCPThreshold
HHoRSCPCancel
HHoEcNoThreshold
HHoEcNoCancel
HHoRSCPThreshold
HHoRSCPCancel
Object
FSMC NRT
& FMCS
HSDPA
FMCS RT
Default
Rec Value
Comments
-12 dB
-9 dB
-105 dBm
-16..-18 dB
-12..-14 dB
-115 dBm
Lower values for NRT services to increase the coverage areas, valid for
HSDPA also. Due the signaling delays at inter-system change caused
by LU and RAU, and due the low bit rate available in GPRS network
without EDGE, it is beneficial to leave UMTS as late as possible (or not
at all?)
-102 dBm -110 dBm
-12 dB
-14..-16 dB Lower value for RT to have more coverage. Absolute ISHO number
-9 dB
-10..-12 dB (and ISHO)
-105 dBm -108..-110 dBm
-102 dBm -105..-108 dBm
It is recommended to activate ISHO cancellation when ISHO is enabled.
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WCDMA GSM Mobility
Slide 13
Parameter Verification & Recommendations
GSM ISHO – Active features
ISHO/ISHO Cancellation
Scope:
RNMOBI parameters GsmHanoverAMR; GSMHanoverCS;
GSMHandoverNrtPS and GSMHandoverRtPS can be used to
activate GSM ISHO per service
ISHOCancellation (RNFC) parameter enables/disables the use
of ISHO Cancellation feature in the RNFC
In case of AMR or CS, different range
 No; ISHO is not allowed for CS voice services. ISHO is also
prohibited if a CS voice service is a part of multiservice.
 Yes; ISHO is allowed for CS voice services. In case of multiservice, a
handover to GSM must be allowed for all CS and PS services which
participate in the multiservice before the handover is possible.
 Priority; ISHO is allowed for CS voice services. The handover is also
allowed if a CS voice service is a part of multiservice.
Object
Network
Value
GsmHandoverAMR
RNMOBI
1
No (0), Yes (1),
Priority (2)
GsmHandoverCS
RNMOBI
0
No (0), Yes (1),
Priority (2)
GsmHandoverNrtPS
RNMOBI
1
No (0), Yes (1)
GsmHandoverRtPS
RNMOBI
0
No (0), Yes (1)
Parameter
Observation:
GSM handover is enabled for AMR and PS NRT services.
ISHO cancellation is disabled in the network
Range
Recommendation:
Activate ISHO cancellation
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Parameter
Object
Network Value
ISHOCancellation
RNFC
Disabled (0)
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WCDMA GSM Mobility
Slide 14
Parameter Verification & Recommendations
FMCG identifiers & Activated ISHO/ISHO cancellation causes
Triggers and thresholds
Scope:
FMCG Identifiers
ISHO triggering/cancellation causes are in FMCG Object.
However thresholds to trigger/cancel ISHO are in FMCS. Use
different FSMC settings for RT & NRT.
1200
1000
394
800
Observation:
600
200
10673
399
400
# WCEL
Most of the 900 cells are using FMCG 40,41,45 and 46
Most of the 2100 cells are using FMCG 50,51, 55 and 56
RT -In both bands all ISHO causes enabled (FMCG 40, 50, 91)
NRT – all ISHO causes disabled for FMCG 41 and 51 (few 900
sites are using 46 with RSCP and ISHO enabled)
HSDPA – RSCP and EcNo causes enabled for FMCG 45 and 55
RT with HSDPA - RSCP and EcNo causes enabled for FMCG 46
and 56
ISHO cancellation is not enabled for any causes.
10698
10648
324
0
9
45
46
40
41
45
46
40
46
398
3000
12
55
56
50
55
HSDPA
56
RTwith HSDPA
91
RT
51
NRT
ISHO triggering causes per FMCG
ISHO cancellation causes per FMCG
Recommendation:
Perform CM checks and parameter audit to make sure that this
configuration match the planned network design and strategy.
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WCDMA GSM Mobility
Slide 15
Parameter Verification & Recommendations
IFHO/ISHO Thresholds
FMCS Identifiers
FMCS configuration
Scope:
1200
IFHO thresholds are in FSMS object – same thresholds used
for IFHO and ISHO to GSM.
1000
393
800
10698
600
397
400
# WCEL
200
Observation:
0
10648
292
1 13 1
9 2
45 46
45
399
6
Rest are used by small amount of cells
3000
1
85 46
1 3
45 45
2
45 55
44 46
55 45
84 46
45
44 44
84 54
43 46
54 44
83 46
84
43
83
53 93
46
43 83
46
46
56
46
46
46
46
56
42
46
46
99
52
42
40
50
80
Most of the 2100 sites are using FMCS 50, 52, 53,54, 55 And
56
Most of the 900 sites are using FMCS 42, 43, 44, 45 and 46.
10673
21
1
55
2
45
46
54
44
46
53
HSDPA
43
46
HSPA
DC HSDPA
56
46
RTwith HSPA
56
46
RTwith HSDPA
52
42
NRT
97
RT
IFHO/ISHO thresholds per FSMC
Recommendation:
Confirm that this configuration match with planned network
design.
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WCDMA GSM Mobility
Slide 16
Parameter Verification & Recommendations
GSM ISHO Measurements
1.
GSMMeasRepInterval determines the measurement reporting interval for periodical ISHO measurements.
2.
GsmNcellSearchPeriod determines the number of periodical ISHO measurement reports, starting from the first
report after the measurement setup during which HO to GSM is NOT possible.
3.
GsmMaxMeasPeriod defines the maximum allowed duration of the measurement by means of the maximum
number of periodical ISHO measurement reports during the measurements. If the RNC is not able to execute the
HO to GSM, it shall stop the GSM measurements after the UE has send the predefined number of measurement
reports to RNC.
4.
GsmMinMeasInterval determines the minimum interval between an unsuccessful ISHO measurement or HO
procedure, and the following GSM measurement procedure related to the same RRC connection. Repetitive GSM
measurement are disabled when the value of the parameter is 0. GsmMinHOInterval determines the minimum
interval between a successful ISHO from GSM to UTRAN and the following ISHO attempt back to GSM related to the
same RRC connection
1
4
4
2
3
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WCDMA GSM Mobility
Slide 17
Parameter Verification & Recommendations
GSM ISHO Measurements
Measurement timers
Scope:
Maximum allowed duration of the ISHO measurement is
calculated: GSMMeasRepInterval * GSMMaxMeasPeriod . If
GSM measurement s are too long, call will drop. If too short,
cell not found.
GSMNcellSearchPeriod: ISHO is not allowed until there are
enough measurement reports given by this parameter. 0
means that only 1 measurement result is enough for decision
making.
Observation:
Similar timer configuration is used by all FMCG objects.
Default values are applied.
Recommendation:
FMCG GsmMaxMeasP GSMMeasRepInterval
eriod
GsmNcellSearchPeriod
40
12
2
0
41
12
2
0
45
12
2
0
46
12
2
0
50
12
2
0
51
12
2
0
55
12
2
0
56
12
2
0
91
12
2
0
In environment where 2G BCCH reuse is high it is
recommended to set GsmMaxMeasPeriod to at least 12 (20 is
a default in RU50).
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WCDMA GSM Mobility
Slide 18
Parameter Verification & Recommendations
GSM ISHO Measurements
Measurement timers
Scope:
GsmMinMeasInterval (FMCG) defines wait time when the
following CM starts. In case of an unsuccessful ISHO attempt,
the network will deactivate CM (related to same RRC
connection) for a time period given by this parameter.
GsmMinHoInterval (FMCG) determines the minimum interval
between a successful ISHO from GSM to UTRAN and the
following ISHO attempt back to GSM related to the same RRC
connection. By default value is 0 (a return handover back to
GSM is disabled)
Observation:
Default value for both parameters used.
FMCG
GsmMinMeasInterval
GsmMinHOInterval
40
2
10
41
2
10
45
2
10
46
2
10
50
2
10
51
2
10
55
2
10
56
2
10
91
2
10
Recommendation:
To avoid ISHO ping-pong consider setting larger value for
GSMMinHOInterval. GSMMinMeasInterval normally set to default.
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WCDMA GSM Mobility
Slide 19
Parameter Verification & Recommendations
GSM ISHO Decision Criteria
ADJG configuration
HopgIdentifiers
Scope:
20000
15000
# Adjg
AdjgRxLevMinHO (HOPG) determines the minimum required
GSM RSSI level which the averaged RSSI value of the GSM
neighbor cell must exceed before the coverage (or quality)
reason handover to GSM is possible. Use value >= -95 dBm.
This parameter has direct impact for the cell found ratio
counters. If several GSM cells fulfil the equation above, cells
are ranked based on AdjgPriorityCoverage.
10000
18027
5000
0
Observation:
1528
1
18027 ADJG neigbours referenced to HOPG id 1 for RT and HOPG
id 3 for NRT. 1528 defined ADJG are not referenced to any HOPG
Recommendation:
Ensure that this is wanted configuration.
3
(blank)
RTHopgIdentifier
(blank)
NrtHopgIdentifier
HOPG
AdjgRxLevMinHO*
AdjgPriorityCoverage
1
15 (-95dB)
0
3
15 (-95dB
0
*internal_value = gui_value + 110
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WCDMA GSM Mobility
Slide 20
Parameter Verification & Recommendations
BSIC Verification
In the case of CS service, the RNC shall always request the BSIC identification of the target cell
before the execution of the ISHO so that:
 UE can synchronize to the GSM cell before HO execution and
 Verify the identification if two or more neighboring GSM cell have the same BCCH Frequency.
In the case of PS service, the RNC shall not verify the BSIC of the target cell before the execution of
the ISHO cell change to GSM/GPRS unless two or more neighboring GSM cells have same BCCH
frequency.
 It is possible to set the BSIC verification procedure mandatory for PS data services with Parameter 007:0238
RN30_MAINT_015 BSIC verification in case of PS NRT calls
 This typically improve NRT ISHO success rate but may also decrease cell found ratio
BSIC identification can be extended by RAN1758 Multiple BSIC Identification feature.
The RNC initiates BSIC identification to the UE for max three GSM carriers simultaneously.
If the ISHO attempt to the best neighbor cell fails, a new attempt to the other cell can be started without new
inter-system measurements in compressed mode.
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WCDMA GSM Mobility
Slide 21
Parameter Verification & Recommendations
Example: Force Decode BSIC feature for NRT
ISHO success rate improved a lot  ISHO cell found ratio decrease
Parameter 007:0238 RN30_MAINT_015
ISHO NRT - Cell Found vs. Success Rate
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
ISHO NRT - Cell Found Ratio (574d )
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ISHO NRT - Success Rate (301c)
16.03.2009
15.03.2009
14.03.2009
13.03.2009
12.03.2009
11.03.2009
10.03.2009
09.03.2009
08.03.2009
07.03.2009
06.03.2009
05.03.2009
04.03.2009
03.03.2009
02.03.2009
01.03.2009
0%
Cell Found x Success Rate
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WCDMA GSM Mobility
Slide 22
Parameter Verification & Recommendations
RAN1758 Multiple BSIC identification
Without
MBSIC Verification
With
MBSIC Verification
• UE completes BSIC verification for the best GSM cell
RSSI
Measurement
RSSI
Measurement
• Handover can fail during BSIC verification or after HO
command
BSIC Verification
for
best cell
BSIC Verification
for
best cell
• Retry is performed after a penalty time with new CM
measurements
Handover
Command
Handover
Command
Handover Fails
Handover Fails
RSSI
Measurement
Handover
Command
BSIC Verification
for
best cell
Handover Success
Without MBSIC Verification
With MBSIC Verification
• UE completes BSIC verification up to 3 of the best cells
• If HO fails after HO Command, the UE is instructed to
handover on the next best BSIC verified cell
• Removes requirement for multiple RSSI measurement and
BSIC verification cycles (reduced compressed mode)
• Improves inter-system handover success rate as
handovers can be completed more rapidly
Handover
Command
Handover Success
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WCDMA GSM Mobility
Slide 23
Parameter Verification & Recommendations
Multiple BSIC Identification
Scope:
Multiple BSIC identification can be enabled with parameter
MultipleBSICIdent(RNMOBI). The MaxBSICIdentTime (FMCG)
parameter limits the maximum time for BSIC identification
measurements per cell. If during this time no handover
succeeded the handover attempt to GSM is finished. The
MaxBSICIdentTime parameter must be configured with a
value of greater than 0 otherwise not active.
Parameter
Object
MultipleBSICIdent
RNMOBI
FMCG
40
41
45
46
50
51
55
56
91
Observation:
Multiple BSICIdent is disabled in RNMOBI, however
MaxBSICIdentTime is different between some objects.
Recommendation:
Network Value
Disabled (0)
MaxBSICIdentTime*
60
0
0
0
60
0
0
0
60
*internal_value = gui_value * 10
Check if this is actually wanted configuration!
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WCDMA GSM Mobility
Slide 24
Content
WCDMA-GSM Mobility
- WCDMA-GSM Mobility
- WCDMA-GSM ISHO Introduction
- Parameter Verification & Recommendations
- ISHO Performance Analysis
- GSM-WCDMA Mobility
- Main Process & Parameters
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WCDMA GSM Mobility
Slide 25
ISHO Performance Analysis
ISHO analysis flow chart - RT
RNC_300h
<X%
Top N Cells
No
No Action needed
Yes
CM start not
possible
Yes
Check AC rejections
No
Low ISHO
Measurement
success
No
Reference Clock
Missing ADJG or bad neighbor
planning
Low ISHO
Success
No
Missing or wrong 2G parameter in
2G MSC or SGSN (BCCH, LAC,
CellID)
2G Ncell Congestion
Wrong 2G Ncell parameter (BSIC)
or BSIC collision
Missing neighbor list after reselection after cell change
order occurred
Non optimimun CM
parameter set
Too low ISHO triggering
threshold or Strict ADJG min
threshold (ADJGRxLeveMinHO)
Half Rate in 2G Ncell (?)
Poor GSM Coverage
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WCDMA GSM Mobility
Slide 26
ISHO Performance Analysis
ISHO Performance – Monitoring
Using ISHO counters/KPI, we can:
1. Compare actual ISHO behavior to wanted ISHO strategy
• ISHO triggering causes/performance separately for RT/NRT
• Network performance and individual cell level performance
2. Monitor ISHO performance
• ISHO analysis can be started with System Program in PLMN level -> RNC level (per 3G
frequency layer)-> Cell level and look at ISHO success rates.
• ISHO performance can be studied in more detail for the worst cells.
• Note for worst cell analysis: There should be enough attempts to have reliable results (min 50
attempts per cell daily)
GSM PM data can be used to monitor CS and PS performance from 2G perspective
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PM – performance management
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WCDMA GSM Mobility
Slide 27
ISHO Performance Analysis
ISHO performance – Detailed Monitoring
Detailed ISHO performance can be studied in more detail on network level and for the worst cells.
• RSRAN023 ISHO performance
 Success rate, cell found ratio, drop rate, drop reasons, ISHO cancellation reasons
• RSRAN018 ISHO reasons
 List reasons that trigger the ISHO procedure
• RSRAN019 ISHO per cause
 Provides performance information about the ISHO procedure, details per handover triggering reason.
• RSRAN045 ISHO Adjacencies
 Provides information about the ISHO procedure performance on adjacency level. Can be used to tune and
modify neighbor definitions. Should be compared with actual existing definitions
• Additionally load and service based HO performance can be monitored in detail by using
RSRAN048, RSRAN049, RSRAN050
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WCDMA GSM Mobility
Slide 28
ISHO Performance Analysis
ISHO Performance – HSPA & Compress Mode
Every time UE enters the compress mode to perform GSM inter-system measurement
there is channel type switch from HSPA/HSDPA to DCH.
Compressed mode measurement have impact for HSPA performance and throughput.
Repeated Channel type switches cause extra signaling to network
 With proper network design number of CM/ISHO attempts can be minimized. (By
properly configuring HO triggering reasons and thresholds)
 WCDMA16 RAN3218 Enhanced Cell Change from HSPA to 2G feature introduce
CM measurement for HSPA when moving from WCDMA to GSM. Without this
feature, the PS call is first reconfigured from HSPA/HSDPA to DCH.
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WCDMA GSM Mobility
Slide 29
ISHO Performance Analysis
ISHO Performance – High level monitoring
Scope:
20
18
100.0
16
14
80.0
12
60.0
10
6
4
2
05.26.2014
05.25.2014
Low ISHO success rate can be due to the non optimal neighbor
planning and GSM network quality. Failed ISHO does not necessarily
lead to a drop, UE can return and stay in 3G for example in the
cases that 2G quality is bad.
RNC_30fe ISHO Success Rate NRT (%)
GSM ISHO Performance KPIs Summary – 14 days
05.24.2014
05.23.2014
05.22.2014
05.21.2014
05.20.2014
05.19.2014
05.18.2014
05.17.2014
05.16.2014
05.15.2014
RNC_299e ISHO Attempts NRT (#)
RNC_300h ISHO Success Rate RT (%)
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RNC_298f ISHO Attempts RT (#)
NRT ISHO success rate KPI shows some degradations, further
investigations are needed.
05.13.2014
0
-> RT ISHO success rate KPI shows average 99% and it is in good
level.
-> NRT ISHO success rate KPI shows some degradations, further
investigations are needed.
11.22.2013
0.0
Recommendation:
#
8
40.0
20.0
Observation:
29
120.0
%
RNC_300h – ISHO success rate for RT services (and
RNC_301f for NRT services). ISHO success rate for NRT and
RT differs in nature, therefore the ISHO KPI is split in RT and
NRT parts. ISHO Success rate for NRT can be significantly
lower than for RT. If NRT ISHOs are deactivated or in very low
level, there is no need to monitor NRT performance.
x1000
ISHO analysis can be started with System Program in
PLMN level -> RNC level-> Cell level and look at ISHO
success rates
ISHO Success Rate
Value
RNC_298f ISHO Attempts RT (#)
RNC_299e ISHO Attempts NRT (#)
RNC_300h ISHO Success Rate RT (%)
RNC_301f ISHO Success Rate NRT (%)
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WCDMA GSM Mobility
Slide 30
ISHO Performance Analysis
ISHO Performance – triggering reasons
Using RSRAN019 is it possible to monitor ISHO procedure details per handover trigger reason.
•
5 triggering reasons, separately for RT and NRT:
 CPICH EcNo, CPICH RSCP, DL DPCH PW, UE TX PWR and UL DCH Quality
•
For each ISHO trigger (5) there are Attempts, Success, SR, Unsuccessful and drops
ISHO performance can be studied in more detail for the worst cells
NOTE: There should be enough attempts to have reliable results (min 50 attempts per cell daily)
RAN Internal Measurements
DL DPCH power
30
Configured UE measurements
UL Quality deterioration
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UE Tx Power
CPICH RSCP
CPICH EcNo
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WCDMA GSM Mobility
Slide 31
ISHO Performance Analysis
ISHO Performance – Attempts per triggering reasons, RT
First step when investigating 3G – 2G
ISHO behavior is to compare actual
behavior to wanted ISHO strategy.
This comparison should be done in two
level:
 Network and individual cell level.
 RT ISHO based on RSCP is typically
dominant.
 RS report 204 can be used to evaluate
2G performance from CS call
perspective.
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WCDMA GSM Mobility
Slide 32
ISHO Performance Analysis
ISHO Performance – Attempts per triggering reasons, NRT
 Using NRT ISHO toward 2G, we need to
remember that 2G data network
performance is not always acceptable to 3G
capable mobile user.
 RS report 226 can be used to evaluate EDGE
( PS ) performance in 2G
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WCDMA GSM Mobility
Slide 33
ISHO Performance Analysis
ISHO Performance - Cancellations
ISHO cancellations, RT
 ISHO cancellation reasons can be
monitored with RSRAN023
16,000
 Cancellations mainly due the EcNo
and RSCP
12,000
 Few also due the active set update
(1A and 1C)
14,000
10,000
Cancel, AS Upt Cell Replace M1010C208
Cancel, AS Upt Cell Add M1010C207
8,000
Cancel, DL DPCH Pwr M1010C206
6,000
Cancel, UE Tx Pwr M1010C205
Cancel, CPICH RSCP M1010C204
4,000
Cancel, CPICH EcNo M1010C203
2,000
0
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WCDMA GSM Mobility
Slide 34
ISHO Performance Analysis
ISHO Performance – Cell found ratio
ISHO performance can be studied in more detail for
worst cells (separately for RT and NRT)
 Cell found ratio for RT shows how easily target
cell is found (BSIC decoding need to be done in
target GSM cell)
 BSIC decoding is not needed for NRT –> cell found
ratio better
 Force decode BSIC -> better ISHO success rate
for NRT
ISHO success rate worse for NRT but
also less attempts
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WCDMA GSM Mobility
Slide 35
ISHO Performance Analysis
ISHO Performance – Unsuccessful ISHO per triggering reasons, RT
Unsuccessful ISHO related to (5) triggering reasons
can be monitored with RSRAN019
• Network and individual cell level.
Counters are updated when the source RNC
receives an RRC: HANDOVER FROM UTRAN FAILURE
message from the UE, and the failure cause is not
"configuration unacceptable“
Reasons for failure:
• Physical channel failure (the UE is not able to establish
(in the target RAT ) the physical channel indicated in the
handover command)
• Protocol error
• Inter-Rat protocol error
• Unspecified
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WCDMA GSM Mobility
Slide 36
ISHO Performance Analysis
ISHO performance - ISHO Drops, RT
ISHO drops per triggering (5) reasons are in
RSRAN019
CPICH EcNo and RSCP are dominant drop
causes for RT in this example
# of drops per day (very few)
All ISHO drops are in RSRAN023, including drops
related to:
• Load and service based HO
• Emergency ISHO
• IMSI based HO
Updated when the radio connection is lost during ISHO
procedure and the radio links are deleted.
Note that if RRC connection re-establishment is enabled, this
failure situation does not always mean the drop of RRC
connection but only a loss of Cell_DCH state radio connection.
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WCDMA GSM Mobility
Slide 37
ISHO Performance Analysis
ISHO Performance - How to detect missing neighbors
M1015 AutodefISHO measurements provide cell to cell ISHO statistics which can be used for neighbor
performance optimization. (RSRAN045 ISHO Adjacencies, cell pair level statistics)
 Detect sites with high ISHO share but not defined as neighbors, check also SR per adjacency
PLMN
Name
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
PLMN
37
Source RNC Source WBTS
Name
Name
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
RNC
BTS
Source WCEL Source WCEL Source WCEL Source
Name
adjacencies [#] LCR ID
WCEL ID
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
W14085
19
0
14085
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Target
Segment
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
xxx
Target BTS Target LAC Target
Name
ID
CELL ID
G5105
13010
5105
G39693
13010
39693
G63947
13010
63947
G6320
13010
6320
G63326
13010
63326
G62485
13010
62485
G40245
13010
40245
G1495
13010
1495
G62484
13010
62484
G35801
13010
35801
G62487
13010
62487
G40242
13010
40242
G6071
13010
6071
G62486
13010
62486
G62519
13010
62519
G39696
13010
39696
G1960
13010
1960
G2008
13010
2008
G5325
13010
5325
G63328
13010
63328
G62488
13010
62488
G6609
13010
6609
G63121
13010
63121
G62483
13010
62483
Neighbor
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
SR per
Avg GSM Avg BSIC
Att Share adjacency RSSI
verif time
14 2,85 100,00
21
4 141,33
12 2,44 100,00
24
3 002,92
5 1,02
80,00
17
3 216,67
3 0,61 100,00
19
3 927,35
3 0,61 100,00
17
3 356,00
2 0,41 100,00
17
3 295,52
1 0,20 100,00
18
3 512,31
1 0,20 100,00
17
4 337,78
5 1,02 100,00
15
3 725,48
298 60,69 100,00
24
3 083,61
1 0,20 100,00
10
4 004,00
15 3,05 100,00
19
3 291,27
7 1,43 100,00
15
3 757,08
0 0,00
0,00
16
1 0,20 100,00
12
3 883,00
0 0,00
0,00
10
0 0,00
0,00
10
2 893,33
56 11,41 98,21
21
3 542,72
42 8,55 100,00
19
3 472,54
6 1,22 100,00
14
3 355,09
0 0,00
0,00
3
0 0,00
0,00
15
3 0,61 100,00
11
3 797,93
11 2,24 100,00
16
3 285,82
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WCDMA GSM Mobility
Slide 38
Content
WCDMA-GSM Mobility
- WCDMA-GSM Mobility
- WCDMA-GSM ISHO Introduction
- Parameter Verification & Recommendations
- ISHO Performance Analysis
- GSM-WCDMA Mobility
- Main Process & Parameters
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Slide 39
Content
WCDMA-GSM Mobility
- WCDMA-GSM Mobility
- WCDMA-GSM ISHO Introduction
- Parameter Verification & Recommendations
- ISHO Performance Analysis
- GSM-WCDMA Mobility
- Main Process & Parameters
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WCDMA GSM Mobility
Slide 40
GSM-WCDMA Mobility - Main Process & Parameters
Issues related to 2G -> 3G HO
Most (but not all) of the operators have adapted basic layering strategy that 3G capable UE should stay
in 3G as 2G network seldom able provide proper throughput to average 3G capable mobile user.
 2G network is already in maintenance mode, and most of network expansions and improvement
programs are targeted to UMTS layer. 2G network can be seen as “safety layer” in case UMTS for any
reason becomes not available.
 Additionally, the fact that 2G network is older leads to situation that in most cases 2G is better from
network coverage point of view. Therefore activating 2G to 3G ISHO can not be strongly
recommended. Normally when 3G capable UE comes to 2G, then in most cases, it comes via 3G to 2G
ISHO. It is then questionable if it make sense to push UE back to where it just came from.
 Some operators decide to deactivate 2G to 3G ISHO at all, and UE will move back to 3G after the call
completion via IDLE mode when 3G coverage gets strong enough.
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WCDMA GSM Mobility
Slide 41
GSM-WCDMA Mobility - Main Process & Parameters
Issues related to 2G -> 3G HO
Most common reason to activate 2G => 3G ISHO is “ to push traffic to 3G “ but…
• Majority of 2G to 3G ISHO’s happen, only if same user had 3G to 2G ISHO earlier, during the call
• Both ISHO’s are potential drops in single call.
• Benefit of 2G => 3G ISHO as traffic balancing tool is questionable as it frequently may lead to ping-pong, unwanted
extra-signaling generated by ISHO signaling and LAU/RAU procedures.
drop
3G
3G => 2G ISHO
ISHO is potential drop
candidate.
2G => 3G ISHO
2G
drop
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WCDMA GSM Mobility
Slide 42
GSM-WCDMA Mobility - Main Process & Parameters
GSM -> WCDMA HO Process and Parameters
Load threshold = 80% (default)
Load reporting interval= 20 s (default)
Handover Triggering Threshold set in BSC
Inter-RAT measurements starts in case the RXLEV of
the serving cell is above or below the given threshold
Qsearch_C, (threshold for Multi-RAT MS)
Handover decision is done in case of load of the
serving cell > load_Threshold and CPICH Ec/No (MET) >
Min Ec/No threshold
MS selects the target UTRAN cell based
on measurement results
Min EcNo Threshold (MET) = -15 dB
FDD_MULTIRAP_REP = 2
Number of WCDMA RAN cell averaging window size [1-32], def=6
Number of WCDMA RAN zero results [0-32], def=5
All adjacent WCDMA RAN cells averaged ([yes,no], def=NO): (No means only the best
three cells in the last sample).
• Reporting period increased by five seconds for each additional WCDMA RAN
frequencies in the neighbor list
•
•
•
•
•
•
•
•
•
Handover command is send to MSC
42
Qsearch_C = never (7 =default)
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Minimum interval between unsuccessful ISHO attempts: 3 s
A Penalty time applies which does not allow to initiate a handover
BACK to WCDMA during 30 s.
In WCDMA, the parameter GsmMinHoInterval (default=10 s) determines the
minimum interval between a successful inter-RAT handover from GSM to
UTRAN and the following inter-RAT handover attempt back to GSM related to
the same RRC connection.
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WCDMA GSM Mobility
Slide 43
GSM-WCDMA Mobility - Main Process & Parameters
GSM -> WCDMA HO Process and Parameters
Parameter name
MML name
Object
range
default
Rec.
min traffic load for speech call
LTSC
HOC
0 – 100%
80%
Strategy based
minimum CPICH Ec/Io level
MET
HOC
-24 – 0,5
-15
To be tuned with 3G
parameters to avoid ping pong
( see next page )
min interval between unsucc
ISHO attempt
UMIU
HOC
0 – 255 s
3s
Strategy based
threshold for multi-RAT MS
QRSC
HOC
0 -15
7
7
FDD Reporting Threshold 2
FRT2
HOC
-115 - -53
-105
Tune based on trial.
MET tuning implies a compromise between blocked calls (GSM) and dropped calls(3G).
• MET should be higher than CPICH EcNo threshold for ISHO 3G->GSM , in order to avoid ping-pong and
dropped calls.
 At least 3dB difference between MET and CPICH EcNo threshold is suggested.
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WCDMA GSM Mobility
Slide 44
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