Using WNCS 2 ID Missing NCells

Using WNCS to Resolve Missing Neighbor

Cells in an Ericsson UMTS System

UMTS Performance Team

Central Region RF Planning and Engineering

2

Overview

Retainability performance has been poor in Ericsson UMTS

markets since P2 upgrade in early June, 2006.

There are many contributing issues, some have been resolved and

others are being addressed. Here is a list of most issues that are

or have been contributors to poor Retainability performance:

RNC module restarts addressed in CU2, resolved Sleeping cell addressed in CU2, CU4, and upcoming CU8,

current performance is good.

Corrupted target 2G LAC on Ericsson RNC CU6 currently being tested, deployment expected this coming week.

Old firmware on air cards issue has been escalated. New sites in pre-launched phases negatively impacting commercial

system performance Needs to be managed more closely Missing neighbors Use WNCS to identify missing neighbor

relationships or overshooting sectors.

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Handover in Connected Mode List Events

Intra-Frequency Handover

Event 1a Add cell to Active Set

Event 1b Delete cell from Active Set

Event 1c Replace worst cell in Active Set

Event 1d Change best cell in Active Set

Inter-Frequency or Inter-RAT Handover

Event 2d Current used frequency is below threshold, start Compressed Mode

Event 2f Current used frequency is above threshold, stop Compressed Mode

Event 6a UE transmit power is above threshold, start Compressed Mode

Event 6b UE transmit power is below threshold, stop Compressed Mode

* Not all events are listed

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Using Event Data in WNCS

WNCS Wide-Band CDMA Neighbor Cell Support

Active

Set

A B

C

RNC

WNCS uses the event data processed by the RNC for normal mobility

management to evaluate neighboring cell relationships. WNCS is used

to:

Identify missing neighboring cell relationships Identify radio link failures Provide data to determine when cells are overshooting their coverage

OSS-RC

5

Example Process of Troubleshooting DCR, Statistics

Use CNN, Watchmark Prospect, or Business Objects to

Determine Retainabilty performance.

* This example uses CNN

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Example Process of Troubleshooting DCR, Daily Report Missing Neighbors

Missing Neighbor report shows cells that have at least 1 occurrence of

the pmNoSysRelSpeechNeighbr being incremented in a 15 minute period

between 5:00 a.m. and 11:00 p.m. each day.

Counter Name pmNoSysRelSpeechNeighbr

Description Number of system disconnects of a speech call for the best cell in the active set due to unknown measured cell (missing neighbor relation).

Condition Network initiated call release of speech calls due to inability to include an non-valid cell in the active set. The counter shall be incremented for the best cell in the active set prior to the call release. Note: This counter is only incremented in the SRNC.

MO Class UtranCell

Counter Type PEG

ST CS, PS

Unit -

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WNCS Explanation How are we using this tool?

WNCS is part of the Radio Network Optimization (RNO) tool.

It is similar to the NCS tool in the Ericsson GSM OSS.

We set up a measurement for the Dallas area for all cells in all RNCs.

The measurement ran from 6:00 a.m. to 10:00 a.m. on Sept 7, 2006.

Once the measurement was complete, we performed the following:

Opened the WNCS Overview Report. Sorted on Dropped Calls in descending order. Investigated each cell starting from the cell with the most dropped

calls, then the cell with the next most dropped calls, etc.

For our investigation we used the WNCS Probable Neighbor Cell Report to determine what cell relation might be missing.

We also used a mapping tool similar to Mapinfo, CNN, and a database of the markets configuration and neighbor relation data in our investigation.

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WNCS Report Basics

Launch the RNO application from the OSS RC Workspace menu, Select the Recording Results

tab, double-click on the report you wish to open.

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Example First Scenario, slide 1

Cell DXU0775Z has 29 drops in the

WNCS Overview Report.

When we use the WNCS Probable

Neighbor Cell Report for DXU0775Z,

we learn that there are 18 Possible

Radio Links Addition attempts; these

are *Event 1a occurrences that did not

happen because the cell was not

defined as a neighbor.

The 18 Possible Radio Link Additions

Could have come from 4 possible cells.

Best Cell

CPICH Ec/No

reportingRange1a

Candidate Cell

timeToTrigger1a

hysteresis1a

MEASUREMENT

REPORT to RNC

Time

* It is possible that Events 1c or 1d rather than

Event 1a could have happened.

Event 1a Add cell to Active Set Event 1b Delete cell from Active Set Event 1c Replace worst cell in Active Set Event 1d Change best cell in Active Set

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29 Drops

In WNCS

Overview

Report

18 Possible

Radio Link

Addition

attempts

4 Possible

Cells based

on Scrambling

Code 308

WNCS

suggests

what cell

is missing

based on

distance,

uses Lat.

Long.

Note: WNCS may not have all the information

required to make the correct prediction.

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DXU0775Z is the cell that shows drops due

to missing neighbors on WNCS.

WNCS suggested that DXU2164Z be

added as a neighbor to DXU0775Z.

The dark blue sector is DXU0775Z. The green sectors are DXU0775Zs neighbors.

The royal blue sectors are undefined neighbors to DXU0775Z.

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If in this case the Event 1d trigger point

was met , and if the signal strength of

DXU1264Z exceeded the value of

releaseConnOffset the system would

release the call and a user perceived drop

would occur.

releaseConnOffset is typically set to 12 dB

Best Cell

CPICH Ec/No

Another Cell in AS

timeToTrigger1d

hysteresis1d

MEASUREMENT

REPORT to RNC

Description:

Threshold, for a cell to be included in the Active Set, when the connection is released due to an inclusion rejection. If UE enters a new cell area, and the quality Ec/No of the new cell is ReleaseConnOffset dB above the quality of the best cell in the Active Set, and for any reason, the new cell cannot be included in the Active Set, then Handover algorithms will ask for UE connection release. The reason is that it is not permitted to stay (with an established connection) in a cell area without being power controlled by the cell serving that area. The UE may cause interference in the uplink.

Range: -3 - +12 dB

Default: 12 dB

Resolution: 0.5 dB

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Example Second Scenario, slide 1

We set up a measurement for the Dallas area for all cells in all RNCs.

The measurement ran from 4:00 p.m. to 9:00 p.m. on Sept 5, 2006.

Once the measurement was complete, we performed the following:

Opened the WNCS Overview Report. Sorted on Dropped Calls in descending order. Investigated each cell starting from the cell with the most dropped

calls, then the cell with the next most dropped calls, etc.

For our investigation we used the WNCS Probable Neighbor Cell Report to determine what cell relation might be missing.

We also used a mapping tool similar to Mapinfo, CNN, and a database of the markets configuration and neighbor relation data in our investigation.

WNCS is part of the Radio Network Optimization (RNO) tool.

It is similar to the NCS tool in the Ericsson GSM OSS.

14


Cell DXU1512X has 495 drops in the

WNCS Overview Report.

When we use the WNCS Probable

Neighbor Cell Report for DXU1512X,

we learn that there are 240 Possible

Radio Links Addition attempts; these

are *Event 1a occurrences that did not

happen because the cell was not

defined as a neighbor.

The 240 Possible Radio Link Additions

Could have come from 4 possible cells.

Best Cell

CPICH Ec/No

reportingRange1a

Candidate Cell

timeToTrigger1a

hysteresis1a

MEASUREMENT

REPORT to RNC

Time

* It is possible that Events 1c or 1d rather than

Event 1a could have happened.

Event 1a Add cell to Active Set Event 1b Delete cell from Active Set Event 1c Replace worst cell in Active Set Event 1d Change best cell in Active Set

15


495 Drops

In WNCS

Overview

Report

240 Possible

Radio Link

Addition

attempts

4 Possible

Cells based

on Scrambling

Code146

WNCS

suggests

what cell

is missing

based on

distance,

uses Lat.

Long.

Note: WNCS may not have all the information

required to make the correct prediction.

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The dark blue sector is DXU1512X. The green sectors are DXU1512Xs neighbors.

The royal blue sectors are undefined neighbors to DXU1512X.

RNC Border

DXU1512X is the cell that shows drops due

to missing neighbors on WNCS.

No WNCS suggestions make sense.

Looking at the site data on this map

shows that DXU1547X has a

Scrambling Code of 146 and is close

to DXU 1512X.

This is a new site from a pre-launch

phase.

Slide 16

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If in this case the Event 1d trigger point

was met and if the signal strength of

DXU1547X exceeded the value of

releaseConnOffset the system would

release the call and a user perceived drop

would occur.

releaseConnOffset is typically set to 12 dB

Best Cell

CPICH Ec/No

Another Cell in AS

timeToTrigger1d

hysteresis1d

MEASUREMENT

REPORT to RNC

Description:

Threshold, for a cell to be included in the Active Set, when the connection is released due to an inclusion rejection. If UE enters a new cell area, and the quality Ec/No of the new cell is ReleaseConnOffset dB above the quality of the best cell in the Active Set, and for any reason, the new cell cannot be included in the Active Set, then Handover algorithms will ask for UE connection release. The reason is that it is not permitted to stay (with an established connection) in a cell area without being power controlled by the cell serving that area. The UE may cause interference in the uplink.

Range: -3 - +12 dB

Default: 12 dB

Resolution: 0.5 dB

Thats All Folks

For now anyway

Using WNCS 2 ID Missing NCells

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