wcdma interference analysis opt2.3

1 © Nokia Siemens Networks Presentation / PLe /15.3.2010For public use – IPR applies

WCDMA Optimisation with Optimizer 2.3WCDMA Interference Analysis

2 © Nokia Siemens Networks Presentation / PLe / 15.3.2010For public use – IPR applies

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Module Objectives

At the end of this module the trainee should be able to:• Prepare the network optimization by creating, verifying, importing and

exporting an interference matrix (IM) for WCDMA

• Visualise Propagation Delay KPIs on Map, Browser and in Histograms

• Find problem cells that cause interference especially over a long distance


WCDMA Interference Matrix and Propagation Delay

• How can I create an Interference Matrix?

• How do I visualise the Interference Matrix and the Interference on the Map?

• How can I find the cells that cause interference far away?

• How do I visualise propagation delay KPIs?


IM Basics

• “Interference Matrix” represents the interference relations between cells

• Interference in this context means simply average received power, whether user signal or “real” interference (adjacent cells are measured as well)

• Interference for WCDMA can be expressed as

– P-CPICH Ec/No

– P-CPICH RSCP

– Scaled RSCP (estimate for average total received power level at UE)

• Interference Matrix is used in Optimizer

– as an input for manual WCDMA Interference Analysis – e.g. to detect Pilot Pollution, candidates for antenna downtilt, P-CPICH power optimization

– together with Propagation Delay Analysis – e.g. to identify overshooting cell, coverage holes, resurgences

• IMs are calculated based on WCDMA measurements (HO reports and DSR)

• IMs can be exported and imported


Interference Matrices Tab

• Precondition: WCDMA measurements were run• Select Interference Type WCDMA• Retrieve measurements


Calculating the Interference Matrix

• Create based on

– specific dates – can be subset of a measurement

– by measurement name – whole measurement included

• Warnings and errors are displayed


Interference Matrix Visualisation

• select IM to be visualised

• press “Show Sets” button


Interference Matrix on Map

• Interference Matrix values between cells can be seen on the map

• For each pair of cells the value above threshold is shown on the map as a line between the cells

• Interference values represent Ec/No, RSCP and Scaled RSCP valuesfrom the measurements


Interference Lines

• Activate correct IM from IM tab with right mouse click

• On Map Visualizations select Other... for Interference Line visualisation

• Select Interference MatrixKPI

• Open the interference analysis parameter dialog


Interference Line Parameters

• Select parameters

• Select a cell(s) from the map

• Calculate Interference


Exercise

• View and visualise measured sets

– It is enough if one person retrieves a set

• Export interference matrix in CSV format and study the contents

• Visualise Interference Matrix Values on the map


Interference Analyzer: Manual IM Analysis

• The Interference analyzer tool allows you to find problematic cells that cause interference (e.g. over great distances) in the network

• You need to select the Interference Matrix that you want to use

• Active IM is in bold



Select RNCs, sites, or cells from the Navigator or use the active scope and start Interference Analyzer



Select filter thresholds and Analyse interference

Example: Show me the cells that interfere over 1 km, with Ec/No > -20.0 dB, with RSCP > -120 dB


Problem Cells

• Adjust thresholds and Analyse again if needed• Select WCEL(s) and Show Chart or Locate on Map• Visualization based on Ec/No, RSCP or Scaled RSCP


Interference Analyzer Chart

• Top right cells suffer the most interference over the longest distance


Interference Analysis on the Map


Interference Analyzer: Automatic Interference Analysis

For the automatic interference analysis you need to have the WCDMA Interference Anaysis KPIs available. (Tools – Network Statistics – Existing KPIs)


Dominant SHO neighbor

Serving Cell

55%

10%

5%

20%

20%

• Finding cells where one or more SHO adjacencies carry excessive amount of SHO’s

• User can define thresholds for

• SHO share [%]

• Number of ADJS adjacencies per WCEL


High total TX power

Serving Cell

• Finding cells with high total transmission power

• User can define thresholds for the KPI :

• Average Downlink load (=average transmitted power [dBm])


Long range cell

• Finding cells with excess coverage area or resurgences far away

• User can define thresholds for the KPI relation:

• Nth percentile of Propagation Delay Distance in relation to Average Length of Defined SHO Adjacencies

1.2 km

2.1 km

1.7 km

Average Length of Defined SHO Adjacencies: 1.67 km

Nth percentile of Propagation Delay Distance: 4.4 km


Pilot pollution

• Finding cells with excess SHO connections (active set size) and a high relative amount of SHO branch replacements

• User can define thresholds for the KPI’s :

• Average Active Set Size

• SHO Update Attempts (Replacement) / SHO Update Attempts

Cell 4ADJS

ADJS

Cell 1

Cell 2

Cell 3

Cell 1

Cell 4

Cell 3

Cell 2

Cell 3

ADJS

Cell 1

Active Set New Active Set (Replacement)


WCDMAWCDMA

GSM GSM

Poor coverage

• Finding cells with insufficient P-CPICH quality and excess IS-HO’s due to poor P-CPICH signal strength

• User can define thresholds for the KPI and KPI ratio:

• Nth percentile of Received P-CPICH Ec/No

• IS-HO Attempts due to poor RSCP / IS-HO Attempts



Rules for Automatic Interference Analysis 1/2



Rules for Automatic Interference Analysis 2/2


Visualizing the Analysis Results


What Can I Do About It?

• Tilt down the antenna

• Turn the antenna

• Lower the antenna

• Change the antenna (pattern)

• Reduce P-CPICH transmit power

• Create adjacencies

• After one or more of these changes new measurements should be performed to get optimum results from the optimisation


Exercise

• Analyse one RNC and find the cell that causes interference over the longest distance with the highest C/I probability

• Locate the interfering cell and interfered cells on the map

• What can you do to these cells before/after the frequency allocation?


Propagation Delay Visualisation

• WCDMA measurements must be run or KPIs retrieved from PM DB

• Propagation Delay can be visualised

– as distance arcs on Map

– as histogram

– as statistics in Browser

• Select correct summarisation level and KPI date


Propagation Delay on Map

• Select scope from Navigator or from Map

• In Distance Color visualisation select Other…

• Select WCDMA->WCEL ->Propagation Delay Histogram

• Tick Distance Color on if off

• Do the same for Distance Label

• Press Show Distance


Propagation Delay on Histogram

• Select scope from Navigator• Right click and select Show on Histogram• Compare with others option uses common scaling if multiple cells are in

scope


Summary Workflow

1. Select Tools->Network Statistics->Interference Matrices

2. Select RNCs and interference type as WCDMA for measurement retrieval

3. Retrieve measurement sets from the correct period

4. Verify interference matrix in table view and on the map

5. Use Interference analyzer and Propagation Delay visualisation to find out if you have problem cells that cause interference


Document change history

Date Version Name Change comment

15.3.2010 1.0 PLe First version for Optimizer 2.3

wcdma interference analysis opt2.3

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