UMTS Initial Tuning
UMTS Initial Tuning Tuning
UMTS Initial Tuning Tuning
Are there any differences between between 2G and 3G? ›
2G Initial Tuning
3G RAN-Tuning
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New Operators
Mature Operators, but not in 3G...
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Mature System and UE
NEW and sophisticated Systems features and Ue
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Coverage focused
Coverage & Capacity focus already in the initial network
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Stable processes
Modified/Enhanced processes
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Stable tools
New tools
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Neighbor relations are basic
Optimized Neighbor relations are key
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Co-sited with GSM and Dual band antennas
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Inter-working with GSM
Typical Tuning Process Flow
Data Collection
Analysis
Reporting Preparation
Change Proposals
Change Verification
Post Processing
Preparation
Measurement
Root Analysis
Implementation & Verification
Initial tuning overview ›
Main RF System performance indicators: › ›
BLER (connection quality) Access Failures
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Dropped Calls
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Pilot Channel Ec/Io
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Mobile Transmitted and Received Power
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Forward/Reverse Link BLER
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Call Processing Information
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Service Measurements
Initial tuning overview ›
Network tunning parameters › › ›
Neighbour list Antenna height, tilt and orientation Network parameters:
-
Output power Cell Selection & Reselection Handover
Power Control Other
Test Equipment ›
Pilot Scanner ›
Scan pilots measuring Ec/Io and RSCP
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Independent of system parameters (soft-HO, etc)
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UEs: Mobile phones and PC Cards
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GPS
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Mobile Monitor software installed in Laptop ›
Mobile, GPS and Scanner connected to laptop
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Collects all data measured and processed by Mobile:
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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
Drive test tools configuration Drive Test Equipments for Voice, CS64 & PS call Short call
Long Call
USB1
GPS
Com 1
scanner
CS64
PS
USB2 USB1
USB2
Data Analysis ›
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Post processing data analysis software ›
Generate plots, table, show L3 messaging
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TEMS (Ericsson), X-Cal (Couei), etc…
GIS Software ›
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To display graphical results from coverage surveys overlaid on street maps MAPINFO, ARCVIEW, etc…
RF Planning tool ›
Planning and evaluation of modifications
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TEMS CPU, Asset, Atoll, etc…
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)
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Clusters should overlapp
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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
Initial tuning Steps ›
First step: check UMTS Spectrum –
–
Possible sources of external interference: ›
Microwave data transmissions
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Wideband noise from machinery
Monitor Uplink and Downlink interference in the UMTS band
Initial tuning Steps ›
Second Step: Site testing –
Test of basic call processing functions: origination, termination of Call, Videocall, PDP context, Data transmissions
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Test of softer handover
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Check correct power settings
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Check correct PSCs of cells
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Check antenna orientation and footprint
Initial tuning Steps ›
Unloaded Cluster optimization –
Collect basic site parameters: coordinates, antenna height, orientations and tilts, PSC.
–
Check design with RF planning tool
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Visit sites
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Verify SC plan (1 cell can´t have 2 neighbours with same PSC)
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Check Cell parameters (LAC, power settings, HO, etc..)
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Neighbour list definition
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Define extensive drive test
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Check O&M alarms before drive test
Initial tuning Steps ›
Unloaded Cluster optimization –
First Pass Optimization ›
Neighbour list correction
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Detect low coverage areas
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Detect areas with Pilot Polution
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Plot and check coverage of each cell
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Aerial modifications: antenna height, azimuth, tilt. Useful plots:
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UE Rx and Tx power Dominant PSC, RSCP and Ec/Io BLER Scanner Top1 PSC, RSCP, Ec/Io Call Events (Drop, Fail, etc)
Initial tuning Steps ›
Unloaded Cluster optimization –
Second Pass Optimization ›
Same as 1st pass:
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Neighbour list correction Detect low coverage areas
Detect areas with Pilot Polution Check coverage of each sector Aerial modifications: antenna height, azimuth, tilt.
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Adjustment of power settings (CPICH power)
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Adjustment of HO parameters:
- Soft-HO: addition, deletion, max active set size - Hard HO GSM UMTS parameters ›
Exhaustive Call Events analysis
Initial tuning Steps ›
Complete system-wide optimization ›
Neighbour list correction in inter-cluster areas
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Load simulation in downlink and uplink
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Under loaded conditions additional tuning is required acceptable areas without load may suffer from interference under load
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Fine tuning (aerial modifications, parameters)
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Exhaustive Call Event Analysis for KPI calculation
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
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
Best Server Signal Strength (RSCP) › Green is good › Yellow can generate problems › Brown is bad Problems occur in areas with bad coverage RSCP in dBm
A
C B
D
Pilot Ec/No measurements (Example) › Green is good › Yellow can generate problems › Brown is bad A
C
Problem areas B Ec/No in dB -9 to 0 -12 to – 10 -30 to -13
D
Finding interference (Example) a a a a a a m m m m m e e e e e s s s s s
By correlating low Ec/No with high RSCP, areas with high interference can be detected
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B4009
25003
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-30
1685 -40
A4155 -50
-60
High interference -70
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P C S R
-80
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-90
RSCP [dBm] -100 -25
-20
-15
-10
-5
0
5
6734
Ec/Io [dB]
e n e n n
-50 to -41,6 -60 to -50 -70 to -60 -80 to -70 - 90 to -80
(100) (357) (598) (376) ( 70)
A3
Initial Tuning experiences RN aspects 1st priority
Securing coverage
Identifying interference
Tuning neighbor relations
O&M aspects (CM) › Parameter consistency › Consistent network configuration
2nd priority
LA/RA planning
Power settings
Correct code plan
Detecting crossed feeders
Measurement principles
3rd priority
Feature tuning
1st priority
Securing Coverage Checking UL and DL service coverage
Drive test to verify p ilot RSCP and Ec/No
› Verify RSCP › Verify Ec/No
Required Ec/No
Required Ec/No unloaded
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
RAB
Required Ec
Required Ec
unloaded
With load
V a lu e s d e p e n d o n CPICH setting and antenna configuration
384 kb ps: 80%
128 kbp s: 95% 20% 18%
100% 90% n o 80% i t
o N16% / c E14% n 12% e v i g 10% t a 8% s n 6% i b % 4%
70% 60% 50% 40% 30% 20%
2% 0%
10% 0% -16
-14
-12
-10
-8
-6
u b i r t s i d e v i t a l u m u C
-4
Pilot Ec/No
Actu al DL service coverage based on Ec/No measurments
1st priority
Identifying interference Minimum quality
› In case of low RSCP: –
Up tilt/re-direct antenna
–
Build new site
–
–30
Both design criteria
Interference limited
–40 –50
A pilot power increase will only help marginally
–60 –70
› In case of low Ec/No (and high RSCP) – – –
down-tilt/redirect antenna
m B d P C S R
–80 –90
Coverage and interference
if necessary turn off interfering sector –25 Reducing pilot power is not a preferred solution
–20
–15
–10
Coverage limited
–5
0
–100
E c /N 0 [dB]
RSCP req outdoor Potentially, high interference can be due to co-code problems Make sure to utilize all 512 codes
Tuning neighbour definitions
1st priority
Consequences of missing/too many neighbour definitions › Good neighbour definitions are essential
› Common reasons for poor nonworking neighbours
› A missing neighbour relation can make call drop
Pilot Ec/No
UE released
best server releaseConnOffset [12 dB]
cell not in active set
–
–
Neighbour has not been defined=> “missing neighbour The neighbour list has been truncated
Tuning neighbour definitions
1st priority
Effect of truncation Monitored set
Active set (AS)
Cell A Cell B
Monitored set is the union of the Ncell list of the cells in AS. Note: Duplicated Ncell entities are removed
Cell C Cell A1 Cell B1 Cell C1
Cell A10 Cell B10
max 32 cells
Cell X Cell Y Cell Z
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
Crossed feeder detection
2nd priority
Common scenarios Reference case
DL
Swapp ed TX&RX
TX/RX1
UL
RX2
Swapp ed TX (or Swapped RX)
DL
DL UL No coverage, loss of UL diversity Low signal level, poor Ec/No Dropped calls Handover fails Call set up problems High UL power
UL Loss of UL diversity High UL power
By monitoring Code, signal level, quality and UE performance (handover, setup success, power) crossed feeder can be detected.
Feature tuning
3rd priority
Things to start with IRAT Purpose To secure a well working mobility/prioritization between WCDMA and GSM network Parameters –UsedFreqThres2dEcno –UsedFreqThres2dRscp –gsmThresh3a –hoType –idle mode and GSM parameters
HSDPA Purpose To ensure high user bitrate and high HS utilisation Parameters –hsHysteresis1d –hsTimetoTrigger1d
–hsdschInactivityTimer –other HS parameters
Packet data Purpose 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
Trouble shooting: Call Events Analysis 1. Classify the reason of dropped and failed calls between a) Radio related cases b) Network related cases c) other related cases 2. Drops and Fails due to Radio related cases to be fixed: Missing Neighbours Pilot polution Low coverage (if this can be improved) 3. Network issues are transmitted to the UTRAN equipment supplier for system investigation 4. Other issues types are being classified and investigated (TMA problems, Test equipment malfunction, etc)
RF Performance Tools : L3 call processing messaging
[ 2004 Apr 14
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
03:09:55.445 ] DL DCCH
Drop Call Reasons Example
Drop calls reasons
Type of drop
Missing neighbour
Radio Issue
Good RSCP, high Ec/IoPilot polution
Radio Issue
Good RF but high BLER, release cause unspecified
Network issue
Test equipment malfunction
Other issue
Out of cluster
Other issue
Call Events Analysis : Drops and Fails Correct classification is not always obvious: for a correct Analysis a variety of RF parameters need to be taken into account: CPICH RSCP and Ec/Io of detected cells measured by UE and Scanner BLER DL (Drive Test Equipment) BLER UL (Traces) UE Tx power L3 messaging UL Interference (Uplink measurements) Etc…
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 equal to GSM
Eliminate “over shooters” Well defined cell coverage Smooth transition to GSM RND have impact on RAN tuning Efficient RAN tuning => Shorter TTM
