Initial Tuning and Optimization
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Transcript of Initial Tuning and Optimization
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UMTS Initial Tuning
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UMTS Initial Tuning
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Are there any differences between 2G and 3G?
2G Initial Tuning 3G RAN-Tuning
New Operators Mature Operators, but not in 3G...
Mature System and UE NEW and sophisticated Systems features and Ue
Coverage focused Coverage & Capacity focus already in the initial network
Stable processes Modified/Enhanced processes
Stable tools New tools
Medium requirements on Project Management High requirements on Project Management
Over shooting sites are causing interference Overshooting and Neighbor sites are causing interference
Neighbor relations are basic Optimized Neighbor relations are key
Co-sited with GSM and Dual band antennas
Inter-working with GSM
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Typical Tuning Process Flow
Preparation
PreparationRootAnalysis
Analysis
Change
Proposals
ReportingChange
Verification
Implementation& Verification
PostProcessing
Measurement
Data
Collection
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Initial tuning overview
Main RF System performance indicators:
BLER (connection quality)
Access Failures
Dropped Calls Pilot Channel Ec/Io
Mobile Transmitted and Received Power
Forward/Reverse Link BLER
Call Processing Information
Service Measurements
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Initial tuning overview
Network tunning parameters
Neighbour list
Antenna height, tilt and orientation
Network parameters:
-Output power
- Cell Selection & Reselection
- Handover
- Power Control
- Other
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Test Equipment
Pilot Scanner
Scan pilots measuring Ec/Io and RSCP
Independent of system parameters (soft-HO, etc)
UEs: Mobile phones and PC Cards
GPS
Mobile Monitor software installed in Laptop
Mobile, GPS and Scanner connected to laptop
Collects all data measured and processed by Mobile:
- RSCP and Ec/Io of cells in Active Set+Neighbour Set
-Mobile Tx and Rx power
- L2 and L3 messaging
- Call processing
- BLER
-Service Measurements
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USB2USB1
Com 1
scanner
Short call Long Call
USB1
CS64
GPS
Drive Test Equipments for Voice, CS64 & PS call
Drive test tools configuration
USB2
PS
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Data Analysis
Post processing data analysis software Generate plots, table, show L3 messaging
TEMS (Ericsson), X-Cal (Couei), etc
GIS Software
To display graphical results from coverage surveys overlaidon street maps
MAPINFO, ARCVIEW, etc
RF Planning tool
Planning and evaluation of modifications
TEMS CPU, Asset, Atoll, etc
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Initial tuning procedure
1. Spectrum clearance Check external interference
2. Sector Tests
Basic call processing functionality checking
3. Unloaded Cluster optimization
Group of 15-20 NodeBs (3 rings)
Clusters should overlapp
Detection of main problems and basic adjustment
4. Complete system-wide optimization
Optimization under loaded conditions (OCNS) Adjustement of Inter-cluster areas
Fine tuning to reach KPI objectives
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Initial tuning Steps
First step: check UMTS Spectrum Possible sources of external interference:
Microwave data transmissions
Wideband noise from machinery
Monitor Uplink and Downlink interference in the UMTS band
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Initial tuning Steps
Second Step: Site testing Test of basic call processing functions: origination, termination of
Call, Videocall, PDP context, Data transmissions
Test of softer handover
Check correct power settings
Check correct PSCs of cells
Check antenna orientation and footprint
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Initial tuning Steps
Unloaded Cluster optimization Collect basic site parameters: coordinates, antenna height,
orientations and tilts, PSC.
Check design with RF planning tool
Visit sites Verify SC plan (1 cell cant have 2 neighbours with same PSC)
Check Cell parameters (LAC, power settings, HO, etc..)
Neighbour list definition
Define extensive drive test
Check O&M alarms before drive test
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Initial tuning Steps
Unloaded Cluster optimization First Pass Optimization
Neighbour list correction
Detect low coverage areas
Detect areas with Pilot Polution
Plot and check coverage of each cell
Aerial modifications: antenna height, azimuth, tilt.
Useful plots:
- UE Rx and Tx power
- Dominant PSC, RSCP and Ec/Io
- BLER
- Scanner Top1 PSC, RSCP, Ec/Io
- Call Events (Drop, Fail, etc)
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Initial tuning Steps
Unloaded Cluster optimization Second Pass Optimization
Same as 1st pass:
- Neighbour list correction
-Detect low coverage areas
- Detect areas with Pilot Polution
- Check coverage of each sector
- Aerial modifications: antenna height, azimuth, tilt.
Adjustment of power settings (CPICH power)
Adjustment of HO parameters:
- Soft-HO: addition, deletion, max active set size
- Hard HO GSMUMTS parameters
Exhaustive Call Events analysis
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Initial tuning Steps
Complete system-wide optimization Neighbour list correction in inter-cluster areas
Load simulation in downlink and uplink
Under loaded conditions additional tuning is required
acceptable areas without load may suffer from interference
under load
Fine tuning (aerial modifications, parameters)
Exhaustive Call Event Analysis for KPI calculation
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What can be achieved with a scanner?
The basic measurements of scanner is CPICH_RSCP (received signal code power)
CPICH_Ec/No (received energy per chip divided by the
power density in the band)
RSSI (received signal strength indicator)
What can you detect with scanner?
Crossed feeder issues (DL)
Coverage verification
Interference problems (cell overlap, pilot pollution)
Missing neighbours
Detect overshooters
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COVERAGE VERIFICATION - Primary Common Pilot
Channel (Example)
Verify P-CPICH detection to minimize coverage holes
P-CPICH RSCP
P-CPICH Ec/No
Verify coverage predictions
Use threshold events and/or coverage maps to detect coverage holes.
Use Best Server Indication to identify interferer
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Best Server Signal Strength (RSCP)
Green is good
Yellow can
generate problems
Brown is bad
RSCP in dBm
A
B
D
CProblems occur
in areas with
bad coverage
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Pilot Ec/No measurements (Example)
Green is good
Yellow can
generate problems
Brown is bad
Ec/No in dB
A
B
D
CProblem areas
-9 to 0
-12 to10
-30 to -13
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Finding interference (Example)
By correlating low Ec/No
with high RSCP, areas
with high interference
can be detected
-100
-90
-80
-70
-60
-50
-40
-30
-25 -20 -15 -10 -5 0 5
Ec/Io [dB]
RSCP[dBm]
High interference
nenenee
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B3031
B4009
A4
A3
A4155
A329
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est Stationest Stationest Stationest Stationest Stationest Stationest Stationest Stationest Station
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1408
1685
23400 23
23405
25003
6734
6741
RSCP [dBm]
-50 to -41,6 (100)-60 to -50 (357)-70 to -60 (598)-80 to -70 (376)-90 to -80 (70)
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2nd priority
RN aspects
Initial Tuning experiences
Parameter consistency
Consistent network
configuration
O&M aspects (CM)
Securing coverage
Identifying interference
Tuning neighbor relations
Detecting crossed
feeders
Measurement principles
LA/RA planning
Power settings Correct code plan
Feature tuning
1st priority
3rd priority
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0%
2%
4%
6%
8%
10%
12%14%
16%
18%
20%
-16 -14 -12 -10 -8 -6 -4
Pilot Ec/No
%binsatgivenE
c/No
0%
10%
20%
30%
40%
50%
60%70%
80%
90%
100%
Cumulativedistribution
Drive test to verify p ilot RSCP and Ec/No
Securing CoverageChecking UL and DL service coverage
Verify RSCP Verify Ec/No
1st priority
Actu al DL service coverage based on Ec/No measurments
RAB
Required
Ec/No
unloaded
Required
Ec/No
With load
Required Ec
unloaded
Required Ec
With load
AMR 12.2 -16 -12 -114 -111
P64/64 -14 -10 -110 -107
P64/128 -12 -8 -110 -107
P64/384 -9 -5 -110 -107
Values depend o n
CPICH sett ing and
antenna conf igurat ion
384 kbps: 80%128 kbp s: 95%
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Identifying interference
In case of low RSCP:
Up tilt/re-direct antenna
Build new site
A pilot power increase will only help
marginally
In case of low Ec/No (and high
RSCP) down-tilt/redirect antenna
if necessary turn off interfering sector
Reducing pilot power is not a
preferred solution
1st priority
Potentially, high interference can be due to co-code
problems
Make sure to utilize all 512 codes
10090807060504030
25 20 15 10 5 0Ec/N0[dB]
RSCP
dBm
Interference limited Both design criteria
Coverage limitedCoverage and interference
RSCP req
outdoor
Minimum
quality
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Tuning neighbour definitionsConsequences of missing/too many neighbour definitions
Good neighbour definitions are
essential
A missing neighbour relation
can make call drop
Common reasons for poor non-working neighbours
Neighbour has not been
defined=> missing neighbour
The neighbour list has been
truncated
best server
cell not in active set
Pilot Ec/No UE released
releaseConnOffset [12 dB]
1st priority
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Tuning neighbour definitionsEffect of truncation
Active set (AS)
max 32 cells
Monitored set is the union of the
Ncell list of the cells in AS.
Note: Duplicated Ncell entities are
removed
Cell A
Cell B
Cell C
Cell A1
Cell B1
Cell C1
Cell A10
Cell B10
Cell X
Cell Y
Cell Z
Monitored set
Unmonitored set not measured by all UE
Neighbours are truncated
Avoiding truncation is important to keep drop rate low
A healthy network has not more than 15-20 relations per cell
1st priority
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Crossed feeder detectionCommon scenarios
DL
UL
Reference case
DL
UL
No coverage, loss of UL diversity
Low signal level, poor Ec/NoDropped calls
Handover fails
Call set up problems
High UL power
Swapped TX&RX
By monitoring Code, signal level, quality
and UE performance (handover, setup success,
power) crossed feeder can be detected.
RX2
TX/RX1
DL
UL
Swapped TX (or Swapped RX)
Loss of UL diversity High UL power
2nd priority
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Feature tuningThings to start with
HSDPAPurposeTo ensure high user bitrate and high HS
utilisation
ParametershsHysteresis1d
hsTimetoTrigger1d
hsdschInactivityTimer
other HS parameters
Packet dataPurpose
To secure a good trade off between
available resources and PS performance
Parameters
downswitchtimer (channel switching)
SF8 (number of 384 users per cell)
BLER target
IRATPurpose
To secure a well working mobility/prioritization
between WCDMA and GSM network
Parameters
UsedFreqThres2dEcno
UsedFreqThres2dRscpgsmThresh3a
hoType
idle mode and GSM parameters
3rd priority
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Trouble shooting: Call Events Analysis
1. Classify the reason of dropped and failed callsbetween
a) Radio related cases
b) Network related cases
c) other related cases
2. Drops and Fails due to Radio related cases to befixed:
Missing Neighbours
Pilot polution
Low coverage (if this can be improved)
3. Network issues are transmitted to the UTRANequipment supplier for system investigation
4. Other issues types are being classified andinvestigated (TMA problems, Test equipmentmalfunction, etc)
RF P f T l L3 ll i
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RF Performance Tools : L3 call processing
messaging
[ 2004 Apr 14 03:09:55.445 ] DL DCCH
log_chan_type : 3
rb_id : 3
length : 6
value DL-DCCH-Message ::=
message downlinkDirectTransfer : r3 : downlinkDirectTransfer-r3
rrc-TransactionIdentifier 1,
cn-DomainIdentity cs-domain,
nas-Message '052265'H
mobility management messages
===> mobility management messages
===> Connection management messages:CM SERVICE REJECT
Reject cause value : Message not
compatible with the protocol state
D C ll R
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Drop Call Reasons
Example
Drop calls reasons Type of drop
Missing neighbour Radio Issue
Good RSCP, high Ec/IoPilot polution Radio IssueGood RF but high BLER, release cause
unspecified
Network issue
Test equipment malfunction Other issue
Out of cluster Other issue
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Call Events Analysis : Drops and Fails
Correct classification is not always obvious: for a correctAnalysis a variety of RF parameters need to be takeninto account:
CPICH RSCP and Ec/Io of detected cells measuredby UE and Scanner
BLER DL (Drive Test Equipment) BLER UL (Traces)
UE Tx power
L3 messaging
UL Interference (Uplink measurements)
Etc
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Summary RAN Tuning
Ensure that there is coverage
All sites are in place correctly installed with correct power settings
Make sure to minimize missing neighbours
Use techniques such as NCS, counters, drive tests
Keep a consistent radio network
To ensure that same performance in all parts of the network
Selected feature tuning when there is significant amount of traffic
Current recommended settings has proven to give good performance equalto GSM
Eliminate over shooters Well defined cell coverage
Smooth transition to GSM
RND have impact on RAN tuning
Efficient RAN tuning => Shorter TTM
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For more details