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7/29/2019 05_UMTS Networks Optimization Methodology
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Optimization Part : Concepts & Methodology ina UMTS Networks
Sophie GIOVINNAZO - 23/02/2006
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Optimization Concept & Methodology in aUMTS Networks
1. What to analyze from the data collection?
2. How to analyze with ACTIX Analyzer?
3. The Optimization Process Diagram, using ACTIX.4. Optimization Actions.
5. Conclusion.
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Optimization Concept & Methodology in aUMTS Networks
1- What to analyze from the data collection?
Measurement Campaigns :Brings information about The Network performance.
Possibility to identify and correct Network problems.
The following elements will be analyzed from all the data collected in order to
determine the overall quality of the Network performance :
- Coverage
- Quality
- Neighbor List
- Drop Calls
In this presentation we will focus only on Uu traces.
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1- What to analyze from the data collection?
Coverage
Constraints:A minimum RSCP level is required to maintain
and/or establish a call and a specific Service-> is very important to understand the coverage
limitations and expectations.
Optimization:Change Tilt, reazimuth, modify CPICH Power or
even add new site in order to change the RSCP
levels allocation.
Doing so, each individual sector should be dominantonly on his pre-defined area.
Definition:The CPICH RSCP (Received Signal Code Power) provides indication of theavailability of DL Pilot Channel, coverage, to meet services requirements.
Planning:
The most important pre-optimization action is the planning of the RSCP Power level over the
Network, per individual sector
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1- What to analyze from the data collection?
QualityDefinition:
The network radio quality indicator is the CPICH Ec/Io.
This indicator provides a clear vision of the level
of interference created by other cells over the
most likely server, in a certain area.
Constraints:If a certain CPICH Ec/Io is not meet the UE will not
be able to communicate with the BS, not being able
to establish a call and possibly dropping it if already
connected.
A bad CPICH Ec/Io will correspond to a bad UE
Ec/No which is used to evaluate and execute
HO events and Active Set updates, indispensable
to maintain a connection.
Optimization:The optimization action applied are the same as for
the coverage.
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1- What to analyze from the data collection?
Dominance
Constraints:These areas are usually associated with Low
CPICH Ec/Io, High number of HO requests andhigh probability of drop calls.
Optimization:Create a single Sector dominance, by removing
the less expected Sector by Tilting or re-
azimuthing, and improving the most likely server
RSCP in that location.
Its also possible to consider lack of Dominance
this problem is considered in the Coverage and
Quality analysis.
Definition:Problems of dominance are described as being areas where there is the presence of4 or more SC with
equivalent CPICH Ec/Io, in a 5dB window.
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1- What to analyze from the data collection?
Neighbor List (3G-3G; 3G-2G)Definition: In order to perform the mobile measure:
EcIo of the neighbor cells for SHO
EcIo or RSCP (parameter) of the neighbor cells for HHO
Constraints:The Uu not check cells that are not declared in the neighboring list even if it is the best cell.
=>Unwanted noise and the quality deteriorated.
Initial declaration:Automatic With the planning tool A9155
Manual: Mapinfo (macro) and/or with 2G counters statistic RNO (HO request)
Optimization:
Automatic: Actix query. Be careful only based on the drive test samples.Manuel: Compares both scanner and mobile maps. Mobile CPICH EcIo or RSCP and Scanner
CPICH EcIo or RSCP.( If the correct cell is not used in HO, the mobile will be degraded comparing
to scanner. )
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1- What to analyze from the data collection?
Drop Calls/ Calls setup failDefinition:
Those evens are a reaction of the UE, or of the RNC, to a certain problem.
A Drop can be due to RADIO,UTRAN or CN problem(SYSTEME)
Optimization:
All the previous slides explained the causesThe of problem lead to those events, so its
imperative to control them.
You should know the story of the call
Ask you question.
What are the events before the drop?
Coverage?
Quality?AS count?
Compress mode ?
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Optimization Concept & Methodology in aUMTS Networks
2- How to analyze with ACTIX Analyzer?
The Optimization task can be done by several ways.
You will find quickly your favorite way of work.=> We will see the main optimization principles with ACTIX.
With ACTIX you can analyzed and filtered the measurements in a way that the problems area are quickly
highlighted you save by this way a lot of time.
The following slides will describe the most important ACTIX elements to be analyzed and what each one
represents in the evaluation of the network performance.
The clearly understanding of each individual ACTIX elements and the relation between them is
indispensable, but this knowledge comes from the: UMTS training
and experience of the Optimizer.
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2- How to analyze with ACTIX Analyzer?
Coverage (1/3)
-CPICH_Scan_RSCP_Sortedby_Ec Io _0, provides the CPICH RSCP, sorted by best CPICH Ec/Iomeasured by the scanner.
This provides a clear view of the overall Coverage.
The area in bleu will have a high probability of
Drop Calls, and the solution to solve this
problem is by Increasing the CPICH RSCP by
re-azimuthing or uptilting the most probable
dominant server.
Increase CPICH Power is also a possibility,
but only after confirmed inefficiency of the
previous solutions.
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2- How to analyze with ACTIX Analyzer?
Coverage (2/3)
-CPICH_Scan_SC_Sortedby_Ec Io _0, provides the SC, sorted by best CPICH EC/Io measured bythe scanner.
This provides a clear view of which cells (SC) are
more dominant in the area, providing a very goodvision of which should be improved.
This area is mostly being served by the left back-lobe
of SC170, and 5 other cells, which proves the
weakness of the signal received.
The best solution to improve the RSCP would be by
re-azimuth SC170 in the direction of the problem
area, as he is the closest and strongest there.Other solution would be by upltiling SC171 or SC174,
but these cells would be covering a extensive
geographical area, compromising their capacity, and
possibly generating CPICH Ec/Io degradation in other
Areas (Pilot Pollution).
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2- How to analyze with ACTIX Analyzer?
Coverage (3/3)
-CPICH_Scan_RSCP_For_SC_(N), provides the CPICH RSCP signal for a specific SC, (N), measured by
the scanner.
This will display the CPICH RSCP of the SC selected, during all the measurement, and its a excellent way
of comparing the signal strength between cells and than decide which one is more suitable to be solve the
problem.
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2- How to analyze with ACTIX Analyzer?
Quality (1/3)
-CPICH_Scan_EcIo_Sorted by_EcIo_0, provides the best CPICH Ec/Io measured by the scanner and
displays a clear view of the overall Quality.
The reason of the low quality in the bigger
region is due to the fact that many signals,
as seen, are arriving in that area with similar
strength, around -100 dBm.
But the low quality in the smaller region is
a case to be analyzed carefully. Lets have
a look at it.
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2- How to analyze with ACTIX Analyzer?
Quality (2/3)
As seen in previous slides the CPICH RSCP in this area is good enough to maintain a good quality
connection.
If the serving cell is providing a good coverage level
but its CPICH Ec/Io is being affected, than it mustbe another cell, not expected SC in the area, that is
arriving with a similar CPICH RSCP affecting the
CPICH Ec/Io of the server.
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2- How to analyze with ACTIX Analyzer?
Quality (3/3)
Lets take a look at what does the UE sees and compare it with the scanner information.
The UE is only attached to the SC170 and due to
the low Ec/No he is not able to communicate to the
NodeB and decode the DL messages, so he doesntupdate his Active Set and dropping after.
The scanner decodes 4 cells with very similar
RSCP, this is a Pilot Pollution condition.
*This is a good example how the Quality affects the
overall performance of the Network, where due to
the reception of more than 3 cells with similarRSCP and Ec/Io creates a quick degradation of
the radio link, causing the DL signalling to failure
reception and the mobile drops.
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2- How to analyze with ACTIX Analyzer?
Scanner/Mobile analysisMobile analysis confirm:
the RF coverage for each cell inside the cluster
insure the power settings
neighbor list tuning.
The troubleshooting can be made by analyzing the following ACTIX maps:
Mobile CPICH EcIo (Uu_ActiveSet_EcNo_0)
Mobile RSCP and RSSI (Uu_ActiveSet_CalculatedRSCP_0)
Mobile Best SC (Uu_ActiveSet_Sc_0)
UE transmitted power (Uu_TxPow)
Number of links in the active set (Uu_ActiveSet_Count)
Based on a crossed analysis (scanner/mobile), it is easy to highlight RFissues and trigger appropriate corrective actions.
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2- How to analyze with ACTIX Analyzer?
Coverage and Quality
EcIo GOOD EcIo BAD
RSCP GOOD OKInterference
Insuffisant Overlap
RSCP BAD Coverage Problem Coverage Problem
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2- How to analyze with ACTIX Analyzer?
Dominance
As a second analysis it is advisable to look for excessive number of SC, 4 or more, arriving at this location.
By locking at the
CPICH_Scan_SC_Sor ted by_EcIo_2an d3
its possible to visualize which SCs are in theboundary of becoming polluters, 2, or the ones
that are already polluters,3, if the
CPICH_Scan_EcIo_Sor ted by_EcIo_(4)is
higher than 5dB from the serving cell
(Problem of Dominance).
This will also provide how many and which SCs
are present in the area. Making easy to identifythe ones that are unwanted, due to, as example,
overshooting or multipathing, making them
strong there.
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2- How to analyze with ACTIX Analyzer?
Neighbor List (1/2)By COMPARE the Uu_ActiveSet_SC_0and CPICH_Scan_SC_Sortedby_EcIo_(0 to X) Vs
Uu_ActiveSet_EcNo_0and CPICH_Scan_EcIo_So rtedb y_Ec Io_(0 to X)
Mobile Scanner
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2- How to analyze with ACTIX Analyzer?
Neighbor List (2/2)
Looking at the following example its understandable the missing neighbour declarations, as the UE, that is
attached to the Cell with SC204, in not scanning SCs 255, which can be seen in the scanner.
This cell should had already been added to the Active Set .
As a consequence of this fact there are severaldrop calls happening in the same area, as the UE
cannot HO to a better cell.
Unfortunately this Site sectors are not declared in
the neighbour cells and the other way around. So
this cell will only be interference when the
connection is not established on it, and will beinterfered by the neighbouring sites when a call is
established on it.
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2- How to analyze with ACTIX Analyzer?
Zone A: Excessive SHO Area. Re-Azimuthing inorder to improve intra-sector separation
Zone B: Sector 2 is clearly very strong in thatarea because of cannon effect of the road, and extra
help of multipathing on the surrounding buildings.
Re-azimuthing or tilting may solve the problem but
this case should be only decided after careful
evaluation of the morphology of the area (analyzing
panoramics may be enough).
Zone C: This area lacks a strong server, so anyweak arriving signal causes a HO.
Create a dominant server by re-azimuthing or
uptilting the nearest cell.
A
B
C
HO Performance:
- Uu_HandoffOk identifies all the handover requested and performed OK. Areas where a abnormalamount of HO are done identifies large SHO areas, due to lack or excess of serving cells.
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2- How to analyze with ACTIX Analyzer?
Drop Calls
-Uu_CallDroppedidentifies all the calls that
were dropped during the measurements
campaign.
To analyze dropped call the first thing to do, is
to check the coverage and quality before thedrop.
You can use maps, tables,queries
You can use the protocol stack and forms in
order to know exactly the events before the
drop, and to know the story of the call.
In this example the cause of the drop is due to interference problem
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3- Optimization Process Diagram, using ACTIX
Measurement
Campaign
Data
Collection
Drive Test
Route
Overall
Quality
Actix Analyzer
Coverage
Quality
Neighbouring
Declaration
Dominance
HO
Performance
Drop
Calls
KPI Production
OK
NOK
- CPICH_Scan_RSCP_Sortedby_EcIo_0- CPICH_Scan_SC_Sortedby_EcIo_0- CPICH_Scan_RSCP_For_SC_(N)
- CPICH_Scan_EcIo_Sortedby_EcIo_0
- CPICH_Scan_SC_Sortedby_EcIo_2 and 3
UE Active Set
Vs
Scanner Top 10
- Uu_HandoffOk
- Uu_CallDropped
CPICH_Scan_EcIo_Sortedby_EcIo_0-
CPICH_Scan_EcIo_Sortedby_EcIo_3> 5dB
CPICH_Scan_EcIo_Sorteby_EcIo > -10dB
CPICH_Scan_EcIo_Sortedby_EcIo_0
-CPICH_Scan_EcIo_Sortedby_EcIo_X
< 15dB
=>
CPICH_Scan_SC_Sortedby_EcIo_X = X should be declared a Neighbour of
CPICH_Scan_SC_Sortedby_EcIo_0 SC.
CPICH_Scan_RSCP_Sorteby_EcIo > -104dB
Uu_ActiveSet_SC_0 and 1 are not
constantly swappingin a big area
No Dropped Calls
CPICH_Scan_RSCP_Sorteby_EcIo > -104dB
CPICH_Scan_EcIo_Sorteby_EcIo > -10dB
- CPICH_Scan_SC_Sortedby_EcIo_(0 3) > 5dBSC in UE Active Set = SC in Scanner Top 10
Uu_HandoffOk = 1 every Inter-Sector in same direction
Uu_CallDropped = 0
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3- Optimization Process Diagram, using ACTIX
ACTIX MAP ACTIVITY
Scanner RSSI or Scanner CPICH
RSCPConfirm coverage
Scanner CPICH EcIo Assess quality
Scanner CPICH EcIo versus Scanner
RSSI
Distinguish between coverage and
quality problems
Scanner Best SC CPICH and
Scanner 2nd, 3rd, 4th, 5th, 6th Best
SC CPICH
Identify interfering cells and cells
performing soft handover
Scanner Per Sector RSCP for SCEvaluate noise contribution of
interfering cells
Scanner Simulated Active SetTrack capacity (identify soft
handover areas)
Mobile CPICH EcIo and Scanner
CPICH EcIo
Compare both maps in order to
identify missing neighbours areas
Mobile and Scanner Best SC CPICHCompare both maps in order to
identify the missing neighbours
Mobile Events (Call Drop and Setup
Failures)
To have the end user perspective
and distinguish between system or
radio problems
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4 -Optimization Actions
How to correct these problems and which tuning
act ions?
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4 -Optimization Actions
TILTING :The SC 255 is clearly overshooting his expected coverage area. You can find his SC in the ASlist with a high RSCP in the location marked. Downtilting is the best, primary, tuning action.
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4 -Optimization Actions
RE-AZIMUTHING :
The SC 143, 144 and 145 are all strongly present in
the area of the biggest opening between sectors.
This location is most probably a strong SHO Area
and dominance must be created by re-azimuthing
the most likely server, Sector with SC 145, creating,
this way, dominance over the area, reducing the HOrequests.
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4 -Optimization Actions
ANTENNA CHANGE :
Antenna changes are advisable when sites covering highway or railroads are overshooting Urbanized
areas.
Its also applied in areas where hotspots are located and all sector capacity is required in a specific
location.
The existing antenna should than be replaced by another one with a smaller Vertical Beamwith andalign the sector with the target area.
Before to perform any change you have to confirm your study with the
planning tool.
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4 -Optimization Actions
PARAMETERS CHANGE:
Cell selection / reselection parameters
Soft Handover (event 1a, 1b, 1c)
Hard Handover (RSCP, Ec/Io)
Compress mode parameter (events 2d_cm, 3a, 2f, 2d_em)
Change CPICH power
Cell Individual Offset
Compress mode EC/I0 RSCP
Dense Urban
Sub-urban
At UMTS border
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OVERVIEW
1. Defining Drive Test Routes
2. Optimization Concepts & Methodology in a Networks
1. What to analyze from the data collection?
2. How to analyze with ACTIX Analyzer?
3. The Optimization Process Diagram, using ACTIX
4. Optimization Actions
3. Conclusion
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Conclusion
The Methodology presented is a simplified version of a process that can easily be much
more complex as the requirement and attention to detail increases.
ACTIX Analyser provides to the optimizer a user friendly layout, with high level of detailand flexibility; making his use unlimited to the requirements of the user. But the analyser
should keep in maind that Actix is only a help.Practice and investigation is the key to
fully understand optimization process .
The most important aspect when starting to optimize is to know what are the most usual
reasons for a bad performance, and create processes that make these aspects clearly.
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Thank You