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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All rights reserved 2005, Alcatel 23/06/05 Page 2

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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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Coverage and Quality

EcIo GOOD EcIo BAD

RSCP GOOD OKInterference

Insuffisant Overlap

RSCP BAD Coverage Problem Coverage Problem


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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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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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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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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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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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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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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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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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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

05_UMTS Networks Optimization Methodology

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