UMTS Performance Trouble Shooting and Optimization Guidelines Ericsson Retainability

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UMTS RAN Performance

Trouble Shooting Guidelines –

Ericsson UMTS Retainability

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Introduction

Purpose & Scope

The intent of this document is to provide UMTS Trouble Shooting and

Optimization from KPI and Counter perspectives for Ericsson (E///) Retainability and provide detailed analysis strategies for identifying reason for the KPI trends and offering guidelines for improving performance by Key Optimization

techniques.

The KPI/Counters described here are applicable to the Ericsson UTRAN.

This document is not all inclusive and is only intended to provide a quick cook book to understand available E/// for trouble shooting and optimization best practices Guideline Document. For any information not covered here, the Ericsson product documentation (CPI/ALEX Libraries) should be referenced.

1.1. Definitions for this Document

Term or

Acronym Definition

3GPP Third Generation Partnership Project

AS Active Set

BSIC Base Station Identity Code BTS Base Transceiver Station

CN Core Network

CPICH Common Pilot Channel DCH Dedicated Channel

DL Downlink

DPCCH Dedicated Physical Control Channel DPCH Dedicated Physical Channel

DRNC Drift Radio Network Controller FACH Forward Access Channel FIFO First In First Out

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Term or

GSM Global System for MobileCommunications HCS Hierarchical Cell Structure

HSDPA High Speed Data Packet Access IAF Intra Frequency

IE Information Element IEF Inter Frequency

IFHO Inter Frequency Handover Inter-RAT Inter Radio Access Technology IRAT Inter Radio Access Technology Iur Interface between two RNC’s KPI Key Parameter Indicator

LA Location Area

LAI Location Area Indicator

MO Managed Object

NBAP Node B Application Part Node B

Logical node responsible for radio transmission and reception in one or several cells

OCNS Orthogonal Channel Noise Simulator PLMN Public Land Mobile Network

RA Routing Area

RAB Radio Access Bearer RAI Routing Area Indicator RAN Radio Access Network RAT Radio Access Technology

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Term or

RBS Radio Base Station – another namefor the Node B RF Radio Frequency

RL Radio Link

RNC Radio Network Controller RRC Radio Resource Control RSCP Received Signal Code Power

RSSI Received Signal Strength Indicator SIB System Information Block

SIR Signal to Interference Ratio TRX Transceiver

TX Transmit

UE User Equipment

UL Uplink

UMTS Universal Mobile TelecommunicationServices UTRAN UMTS Terrestrial Radio AccessNetwork WCDMA Wideband Code Division MultipleAccess

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Retainability

Retainability is defined as the ability of a user to retain its requested service once connected for the desired duration. The metrics within the Ericsson RNC and OSS provide counters and KPI’s that describe the behaviors and experience of the subscribers on the UMTS network.

This is divided up into a number of areas, CS and PS, as well as being divided on an RRC and RAB basis.

The main items which affect retainability on the UMTS network include:

• Handover performance (soft/softer/Iur/IRAT) and missing neighbour cell • UL/DL imbalance

• Incorrect parameter settings (power, admission, release) • Congestion

• Radio environment impact (corner effect, fast Ec/No drop, Pilot pollution etc)

• Node Hardware failure • T1 Congestion

The services which have counters for retainability are:

 CS Voice  CS Data  Video  PS Streaming  PS Interactive  HSDPA  EUL (HSUPA)

In the following sections, CS Voice, PS Interactive and HSDPA will be discussed in detail.

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Troubleshooting Flowchart

The following flowchart may be useful for troubleshooting the voice drop issues based on the problem areas

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Ericsson

Retainability flowchart.ppt

CS Voice RAB Retainability

The metrics for CS Voice RAB Retainability are the most extensive of the UMTS Services in the Ericsson OSS. These metrics can be run on an RNC/Market level or on a cell level.

The main report for identifying and troubleshooting retainability .This contains the Drop Rate and Drop Reason counters that will be discussed. For drops during the IRAT procedure, the 3G-2G Relation report can also be used to identify the IRAT Drops.

The KPI for Voice is the Voice RAB Drop Rate %. This is made up of the following counters:

Counter Description Condition MO Class

pmNoSystemRabReleaseSp eech Number of successful system RAB releases (Speech) referred to the Best Cell in the Active Set.

This counter is only increased due to a RANAP Iu Release Command or RAB Assignment Request message with “release cause” = anything except ’Normal Release’, ’Successful Relocation’, ’Resource

Optimisation Relocation’, ’User Inactivity’ or ’release-due-to-UE-generated- signaling-connection-release’. This counter is incremented for the best cell in the Active Set in the SRNC.

UtranCell

pmNoNormalRabReleaseSpe

ech Number of successful normal RAB releases (Speech) referred to the Best Cell in the Active Set.

This counter is only increased due to a RANAP Iu Release Command or RAB Assignment Request message with “release cause” = ’Normal Release’, ’Successful Relocation’, ’Resource Optimisation

Relocation’, ’User Inactivity’ or ’release-due-to-UE-generated signaling- connection-release’. This counter is incremented for the best cell in the Active Set in the SRNC.

UtranCell

The KPI is defined in T-PIM shows the percentage of system/abnormal RAB releases over the total number of RABs. It is defined as follows:

] Speech RabRelease pmNoNormal Speech RabRelease pmNoSystem Speech RabRelease pmNoNormal 1 [ * 100 (%)    opRate VoiceRABDr

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In the Ericsson RNC, there are also counters that breakdown some of the RF Drop Reasons (Other than IRAT) to aid the troubleshooting of issues. The counters for Voice Drop reasons are:

pmNoSysRelSpeechSoHo Number of system disconnects of a speech call for the best cell in the active set due to Soft Handover action.

Network initiated call release of speech calls due to inability to include a non-valid or 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. UtranCell pmNoSysRelSpeechNeighbr Number of system disconnects of a speech call for the best cell in the active set due to unknown measured cell (missing neighbor relation).

Network initiated call release of speech calls due to inability to include a 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. UtranCell pmNoSysRelSpeechUlSynch Number of system disconnects of a speech call for the best cell in the active set due to lost UL synch.

Incremented if the timer dchRcLostT expires and the RAB type is a CS

Conversational Speech 12.2 Kbps RAB. Note that the counter is applicable for CS Speech RAB and for Multi- RAB, that is, the counter will be stepped if the released RAB is a multi-RAB including a CS Conversational speech RAB Note: This counter is only incremented in the SRNC. UtranCell pmNoOfTermSpeechCong Number of speech Radio Connections served by this RNC terminated due to congestion

The counter is increased when a UE using the speech service is released due to cell

congestion. The counter is increased in CRNC for non-drifting UEs for the one cell with congestion.

UtranCell

The counters for Soft Handover and Neighbours can be used to determine the drops caused by Radio Link Addition failure (SHO Failure). This is typically due to site issues or T1 issues causing a failure to add a Radio Link on this SHO leg.

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These counters can be used in conjunction with the IRAT Drop calculation to determine the breakdown of drops on the RNC/Market or Region level. The IRAT Drops are given by the following formula:

IRAT Drops (c) = pmNoAttOutIratHoSpeech

-pmNoSuccessOutIratHoSpeech-pmNoFailOutIratHoSpeechReturnOldChPhyChFail

-pmNoFailOutIratHoSpeechReturnOldChNotPhyChFail-NoFailOutIratHoSpeechUeRejection

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The raw counter descriptions for these are below.

pmNoAttOutIratHoSpeech Number of

attempted outgoing (to GSM) inter-RAT handover for ’Conversational speech RAB’. The counter is stepped for the best cell in the active set but only if that cell has a cell relation towards the target cell. If the best cell in the active set has no cell relation towards the target cell, the counter is not stepped. The counter is increased when RNC sends "HANDOVER FROM UTRAN COMMAND". This counter will only be incremented in the SRNC. GsmRelati on pmNoSuccessOutIratHoSpeech Number of successful outgoing (to GSM) inter-RAT handover for ’Conversational speech RAB’. The counter is stepped for the best cell in the active set but only if that cell has a cell relation towards the target cell. If the best cell in the active set has no cell relation towards the target cell, the counter is not stepped.

The trigger is when IU RELEASE

COMMAND is received with cause ’Normal release’ or ’Successful

relocation’ and based on the CS RAB state. This counter will only be incremented in the SRNC.

GsmRelati on

pmNoFailOutIratHoSpeechReturn

OldChPhyChFail Number of failed outgoing (to GSM) inter-RAT handover due to

physical channel failure, where the UE returns to the present Active Set for

’Conversational speech RAB’. The counter is stepped for the best cell in

The trigger is the reception of "HANDOVER FROM UTRAN FAILURE" with Inter-RAT handover failure cause=Physical Channel Failure and based on the CS RAB state. This counter will only be incremented in the SRNC.

GsmRelati on

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the active set but only if that cell has a cell relation towards the target cell. If the best cell in the active set has no cell relation towards the target cell, the counter is not stepped

pmNoFailOutIratHoSpeechReturn

OldChNotPhyChFail Number of failed outgoing (to GSM) inter-RAT handover due to

reasons other than physical channel failure, where the UE returns to the present Active Set for ’Conversational speech RAB’. The counter

is stepped for the best cell in the active set but only if that cell has a cell relation towards the target cell. If the best cell in the active set has no cell relation towards the target cell, the counter is not stepped

The trigger is when "HANDOVER FROM UTRAN FAILURE" is received with inter-RAT handover failure cause=any other cause apart from Physical channel failure or configuration unacceptable, and based on the CS RAB state. This counter will only be incremented in the SRNC.

GsmRelati on

pmNoFailOutIratHoSpeechUeReje

ction Number of failed outgoing (to GSM) inter-RAT handover, rejected by

UE, for

’Conversational speech RAB’. The counter is stepped for the

best cell in the active set but only if that cell has a cell relation towards the target cell. If the best cell in the active set has no cell relation

towards the target cell, the counter is

The trigger is when "HANDOVER FROM UTRAN FAILURE" is received with inter-RAT handover failure cause=configuratio n unacceptable, and based on the CS RAB state. This counter will only be incremented in the SRNC

GsmRelati on

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Drop Breakdown

These metrics can be used to determine the breakdown of drops on an RNC, Market or Region level and can be shown as follows.

The “Other Drops” shown in the chart represent the drop causes which cannot be tagged with a specific reason for the drop. This represents:

Other Drops = Total Voice Drops – Voice Drops with a defined Reason This chart provides an overview of the areas to concentrate the performance analysis for the network.

MOU Per Drop

The other metric which is important to monitor is the MOU Per Drop (MPD). This gives a measure of the Customer Experience on the network.

This is given by:

MOU Per Drop = Minutes of Use [Derived from Erlangs] / Total Number of Voice Dropped Calls

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As expected, as the drop rate decreases, the MPD will increase.

Iur Drops

When more than one RNC is used to serve a particular area, drops may occur when the user travels between the area served by one RNC to the area served by the 2nd

RNC over the Iur boundary. These can be seen in the retainability Iur report which can be broken down by Iur Link MO. This metric uses the same counter names as the Drop Rate metric but on an Iur MO.

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As can be seen from the graph above, the Iur Drop Rate is higher than the overall RNC Drop Rate and the number of samples is much lower.

Other Metrics/Counters

Other counters which are included in the report which may be useful in troubleshooting on an RNC level are:

pmNoReleaseDchRcLostT Number of overall release triggered by dchRcLostT expiry When the RBS detects loss of UL synchronization for an RL Set in a Radio Connection it will send the Radio Link failure

Indication message to the RNC. If all RLs have failed the timer

dchRcsLost is started. When the timer expires the Radio Connection is considered lost and the counter is increased. The counter is never incremented in relation to a successful or a failed Rcs

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Cell_DCH to IDLE Transition. However, this does not apply to cases when RCS failure is the actual trigger of CELL_DCH to idle transition pmNORlcErrors Number of RLC

unrecoverable error (UTRAN) for UEs on FACH or DCH An RLC unrecoverable error in RNC L2 initiates the IU Release procedure. The counter is increased.

NOTE: The counter is not stepped for L2 errors in the UE. The UE

shall send Cell Update with ’RLC Error’ in that case.

Rcs

These counters are active in the Radio Connection Supervision (RCS) Subsystem.

Drops Due to Missing Neighbours (Invalid Neighbours)

When analysis is completed for Missing Neighbours for a cell, both the WNCS/GPEH Missing Neighbour tool and Drive Test Coverage analysis should be used. Existing neighbours should also be optimized using the RL Addition counters in the 3G-3G Report. The following steps are a suggestion for troubleshooting (Effect on the surrounding sites must also be taken into account):

1. Ensure that during the period the missing neighbours were pegged that surrounding sites were not off air creating a coverage hole and false missing relations.

2. Addition of suggested neighbours by WNCS/GPEH (Including deletion of unused neighbours if required) if deemed valid

3. Analysis of existing neighbours on cell

4. Analysis of coverage area of cell (Problem Cell and Proposed Neighbour) and Target Cells using the Planning Tool, existing drive tests or by performing new drive tests

5. Perform Downtilts and other physical optimization as required

After these steps are performed, monitoring should continue on a cluster of cells around the affected cell to determine the performance improvement.

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Drops Due to RL Addition Failures (Valid Neighbours)

When a large number of Radio Link Addition failures are detected on a cell/RBS, this may highlight a problem with the transport network (T1’s, IMA Groups) or Hardware issues.

This metric is developed from two of the available metrics in the Retainability Report:

 Voice Drops due to Missing Neighbor

 Voice Drops due to inability to add Neigh to AS

RL Addition Failure Drops = Inability to Add to AS – Missing Neighbour Drops

The following steps are a suggestion for troubleshooting: 1. Check for alarms on the site for Hardware Issues 2. Check the T1 Errors on the site

3. Check the Cell Availability (Auto Downtime) on the cells. This may cause these issues if the PICH radiates while the cell is locked down

4. Determine if the issue affects only one cell or a RBS or a cluster of Sites

This issue should be dealt with in the normal T-Mobile process for T1’s and hardware issues. After these steps are performed, monitoring should continue on a cluster of cells around the affected cell to determine the performance improvement.

Drops Due to UL Sync

UL Synchronization drops are difficult drops to define the exact reason for the drop. The algorithms that cause the counter to be incremented are:

1. Supervision of radio link synchronization status 2. Supervision of RLC protocol (Layer 2 failures) 3. Supervision of connections on common channels

This can be a symptom of lack out of UL or DL coverage or high UL Interference. The following steps are a suggestion for troubleshooting:

1. Using Drive Tests (Existing or New)and W-MRR, investigate the UE Tx Power for high values

2. Check the parameters for the Max UE Tx Power and maxSir values

3. Analysis of coverage area of cell (Problem Cell and Proposed Neighbour) and Target Cells using the Planning Tool, existing drive tests or by performing new drive tests

4. Use of GPEH event (INTERNAL_MEASUREMENT_HANDLING_ EVALUATION) to determine the number of Event 6a occurrences to determine UE Reports on Max Tx Power or number of Event 2d occurrences to determine reported EcNo in a cell

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Drops Due to IRAT

This cause is determined by calculation using a number of counters from the Mobility report. Issues with IRAT Drops may show an issue with the defined neighbours for the cell. These include:

 Incorrect Prioritization

 Neighbour List too long (Too long in compressed mode searching for neighbours)

The following steps are a suggestion for troubleshooting:

1. Neighbour List cleaning/deletion based on Relation Usage counters to reduce the search time/time in compressed mode

2. Coverage area verification for IRAT Neighbours

3. Re-prioritization of Neighbour Relations based on usage

Drops Due to Congestion

This cause is related to a lack of Hardware or Software licenses on the RBS Base Band or to interference. It uses Power and UL RTWP measurements to resolve the overload in the Uplink and Downlink. The following steps are a suggestion for troubleshooting:

1. Check the downswitch counters for congestion reasons – determine whether the issue is in the UL or DL

2. Investigate the RRC Accessibility Failures due to Lack of DL Power and Lack of Channelization Codes

3. Perform analysis of the coverage area and reduce overshooting

4. Verify the CE Usage and HW Allocation and dimensioning with the BSS Team

Miscellaneous Drops

These drops are the remaining drops that cannot be accounted for in the drop reasons outlined above. There are a number of reasons for these and the drops with defined reasons above should be actioned first. Some of the causes for the drops include:

1. Transport Issues (T1’s etc) 2. Hardware Issues

3. RF Issues outside of the previously mentioned counters 4. UE Issues

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Some of the corrections for the previous issues will aid the remedy of these

Miscellaneous/Other drops. For further investigation of the drop causes, GPEH, CTR and the Tektronix K-18 tools should be used to determine the reason behind the drop.

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CS Voice RRC Retainability

The metric for CS Voice RRC Retainability is only made up of 2 counters. This metrics can be run on an RNC/Market level or on a cell level. The counters are below:

pmTotNoRrcConnectReqCsS ucc Total number of Successful Conversation al Call (originating and terminating) and Emergency Call RRC Connection attempt.

The counter is increased when an RRC Connection Setup Complete message is received following an attempt to setup an originating or terminating conversational call. UtranCell pmNoSpeechDchDiscAbnor m Number of abnormal disconnect of a speech call for the Best Cell in the Active Set..

The counter is only increased for the speech RAB, that is the conversational/speech 12.2 Kbps RAB". The counter is only increased when the RRC Connection is released with the RRC Connection Release command with "release cause" = anything but ’normal event ’ or ’user inactivity’ or ’Directed Signalling Connection Re-establishment’. In case of multi-RAB or multi signaling connection, the RRC

Connection will remain after that the signaling connection or RAB to one CN have been released and therefore the counter is not be increased. The counter is only increased the first time the RRC

Connection Release is sent to the UE. (The RNC may transmit several RRC messages to increase the probability of proper reception of the message by the UE).

UtranCell ] CsSucc ConnectReq pmTotNoRrc orm DchDiscAbn pmNoSpeech [ * 100 (%) opRate VoiceRRCDr

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PS Interactive RAB Retainability

The KPI for PS Interactive is the PS Interactive RAB Drop Rate %. These metrics can be run on an RNC/Market level or on a cell level. This includes the HSDPA RAB’s as well as PS R99 RAB’s.

The main report for identifying and troubleshooting retainability issues in T-PIM is the Retainability Report. This contains the Drop Rate and Drop Count.

This is made up of the following counters:

pmNoNormalRabReleasePac

ket Number of successful normal RAB releases (PS Data) for the best cell in the active set. When releasing a HS RAB, this counter is stepped for the Serving HS-DCH cell

This counter is only increased due to a RANAP Iu Release Command

or RAB Assignment Request message with “release cause” =

’Normal Release’, ’Successful Relocation’, ’Resource

Optimisation

Relocation’, ’User Inactivity’ or ’release-due-to-UE-generated-signalling-connection-release’. It is for the Best Cell in the Active Set

and when releasing a HS RAB, this counter is stepped for the Serving

HS-DCH cell.

UtranCell

pmNoSystemRabReleasePac

ket Number of successful system RAB releases (PS Data) for the best cell in the active set. When releasing a HS RAB, this counter is stepped for the Serving HS-DCH cell

This counter is only increased due to a RANAPIu Release Command or RAB Assignment Request message with

“release cause” = anything except ’Normal Release’, ’Successful

Relocation’, ’Resource

Optimisation Relocation’, ’User Inactivity’ or

’release-due-to-UE-generated- signalling-connection-release’. This

counter is incremented for the best cell in the Active Set in the SRNC

and when releasing a HS RAB, this counter is stepped for the Serving

HS-DCH cell

UtranCell

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] Packet RabRelease pmNoNormal Packet RabRelease pmNoSystem Packet RabRelease pmNoSystem [ * 100 (%)   DropRate PSInterRAB

There are no IRAT Drop Counters for PS Interactive so a useful metric is the PS Interactive IRAT Failure Rate (%).

] tCcAtt pmNoOutIra tCcSuccess pmNoOutIra 1 [ * 100 (%) _ _IRAT Failure   PSInterRAB

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The raw counter descriptions for these are below.

pmNoOutIratCcReturnOldCh Total number of the PS Inter-RATCC attempts for UE on DCH where

the UE returns to old channel.

The counter is stepped for the best cell in the active set, but only if that cell has a cell relation towards the target cell. If the best cell in

the active set has no cell relation towards the target cell, the counter is not stepped.

Inter-RATCC from UTRAN to GPRS, UE on DCH. The

counter is

increased when the Cell Change Order From UTRAN Failure (RRC) message is received from the UE

GsmRelati on

pmNoOutIratCcAtt Total number of the PS Inter-RATCC attempts on DCH. The counter is stepped for the best cell in the active set, but only if that cell has a cell relation towards the target cell. If the best cell in

the active set has no cell relation towards the target cell, the counter is not stepped. Inter-RATCC from UTRAN to GPRS, UE on DCH. The Handover evaluation function triggers this function to indicate that we need to make handover to a GSM cell. (A Measurement Report message (RRC) for event 3a has been received from the UE). The counter is

increased when the Cell Change Order From UTRAN (RRC) message has been sent to the UE.

GsmRelati on

pmNoOutIratCcSuccess Number of

successful PS Inter RAT cell change attempts for UE on dedicated channel. The counter is triggered by CN Iu Release Command following the sending of the CELL CHANGE Inter-RAT CC from UTRAN to GPRS, UE on DCH. The Handover Evaluation function triggers this function to indicated that we need to make a handover to a GSM cell (A GsmRelati on

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ORDER

FROM UTRAN message. The counter is stepped for the best cell in the active set, but only if that cell has a cell relation towards the target cell. If the best cell in

the active set has no cell relation towards the target cell, the counter is not stepped

Measurement Report message (RRC) for event 3a has been received from the UE). The Cell Change

Order from UTRAN (RRC) message is sent to the UE and the counter

is increased when a Iu Release

Command is received from the PS

CN, with cause ‘Normal release’ or ‘Successful

Relocation’. The IRAT Drop Rate can be estimated from the following formula:

] tCcAtt pmNoOutIra ldCh tCcReturnO pmNoOutIra -tCcSuccess pmNoOutIra -tCcAtt pmNoOutIra * 100 (%) _IRATDrop  PSInterRAB

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Iur Drops

As in the CS Voice example, where more than one RNC is used, drops may occur over the Iur Boundary. These can be seen in the retainability Iur report and can be broken down by Iur Link MO. This metric uses the same counter names as the Drop Rate metric but on an Iur MO.

As can be seen from the graph above, the Iur Drop Rate is higher than the overall RNC Drop Rate and the number of samples is much lower. This mirrors the

experience on CS Voice.

These plots should be used as an indication of issues that should be investigated further on a Cell/RBS basis. Detailed troubleshooting will be included in the Cell Analysis section.

Cell/RBS Analysis

The Drop Rate and Count metrics can be used on a Cell level also. The Worst

Offenders in an RNC/Market/Region level should be ranked by the following metrics:

 PS Interactive Drop Rate

 PS Interactive Count (Contribution to Total RNC/Market/Region)

These PS Interactive drops do not have broken down drop reasons similar to the Voice examples. There are a number of possible reasons for these drops and they should be investigated like the miscellaneous drops in CS Voice.

1. Transport Issues (T1’s etc) 2. Hardware Issues

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Some of the corrections for the Voice drop issues will aid the remedy of these PS Interactive drops. For further investigation of the drop causes, GPEH, CTR and the Tektronix K-18 tools should be used to determine the reason behind the drop.

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1.2. PS Interactive RRC Retainability

The metric for PS Interactive RRC Retainability is only made up of 3 counters. This metrics can be run on an RNC/Market level or on a cell level. The counters are below:

pmNoPacketDchDiscAbnorm Number of abnormal disconnects of a packet call over DCH and

E-DCH for the Best cell in the Active set

The counter is only increased when the RRC Connection is released

with the RRC Connection Release command with "release cause"

= anything but ’normal event ’ or ’user inactivity’ or ’Directed Signalling

Connection Re-establishment’. In case of multi-RAB or multi signaling

connection, the RRC

Connection remains after that the signaling

connection/RAB to one CN have been released and therefore the

counter shall not be increased. The counter is only increased the first

time the RRC Connection Release is sent to the UE. (The RNC

may transmit several RRC messages to increase the probability of

proper reception of the message by the UE).

UtranCell

pmNoCellFachDisconnectAb

norm Number of abnormal disconnectio ns from common channels (that is, CELL_FACH state).

This counter is only increased when the packet FACH RRC Connection

is released with an RRC Connection Release message with

“release cause” = anything except ’normal event ’ or ’user inactivity’

or ’Directed Signalling

Connection Re-establishment’. The counter is

only increased the first time the RRC Connection Release is sent

to the UE. (The RNC may

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transmit several RRC messages to increase

the probability of proper reception of the message by the UE). pmTotNoRrcConnectReqPsS ucc Total number of Successful ’Originating Interactive Call’, ’Terminating Interactive Call’, ’Originating Background Call’, ’Terminating Background Call’, or ’Originating Subscribed Traffic Call’ RRC connection setups.

The counter is increased when an RRC Connection Setup Complete

message is received following an attempt to setup Originating Interactive Call’, ’Terminating Interactive Call’, ’Originating Background

Call’, ’Terminating Background Call’ or ’Originating Subscribed Traffic Call’. UtranCell ] eqPsSucc rcConnectR pmTotNo ctAbnorm chDisconne pmNoCellFa orm DchDiscAbn pmNoPacket [ * 100 (%) R DropRate PSInterRRC  

These metrics can be investigated in the same way as the PS Interactive RAB Drops.

HSDPA Data RAB Retainability

The KPI for HSDPA is HSDPA RAB Drop Rate %. These metrics can be run on an RNC/Market level or on a cell level.

This is made up of the following counters:

pmNoSystemRbReleaseHs Number of successful system releases of packet RABs mapped on HS-DSCH in the Serving HS-DSCH cell

The counter is stepped for the Serving HS-DSCH cell at

RAB/RB combination transition from PS Interactive 64/HS (or 384/HS or EUL/HS) - HS-DSCH to SRB-DCH or to Idle mode due to the same reasons as for stepping the existing counter pmNoSystemRabReleasePacket

UtranCell

pmNoNormalRbReleaseH Number of successful normal

The counter is stepped for the Serving HS-DSCH cell at

RAB/RB combination transition

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releases of packet RABs mapped on HS-DSCH in the Serving HS-DSCH cell.

from PS Interactive 64/HS (or 384/HS or EUL/HS) - HS-DSCH to SRB-DCH or to Idle mode due to the same reasons as for stepping the existing counter pmNoNormalRabReleasePacket

] RbReleaseH pmNoNormal RbReleaseH pmNoSystem RbReleaseH pmNoSystem [ * 100 (%) _   e RABDropRat HSDPA

HSDPA MB Per Drop

Another metric, aside from the Drop Rate and Count, which can be monitored, is the MB Per Drop (MBPD). This gives a measure of the Customer Experience on the network.

This is given by:

MB Per Drop = MB Downloaded / Total Number of HSDPA Dropped Calls

Cell/RBS Analysis

The Drop Rate and Count metrics can be used on a Cell level also. The Worst

Offenders in an RNC/Market/Region level should be ranked by the following metrics:

 HSDPA Drop Rate

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These HSDPA drops do not have broken down drop reasons. There are a number of possible reasons for these drops and they should be investigated like the

miscellaneous drops in CS Voice. 1. Transport Issues (T1’s etc) 2. Hardware Issues

Some of the corrections for the Voice drop issues will aid the remedy of these HSDPA Drops. For further investigation of the drop causes, GPEH, CTR and the Tektronix K-18 tools should be used to determine the reason behind the drop.

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2.Configuration Management

Configuration Management tools and methods should also be used in improving retainability. Some of these items have been discussed already but these include:

– Neighbour List Optimization • Counts (3G-3G and 3G-2G)

– Removals – Additions

• Selection Priority (3G-3G and 3G-2G)

– Counter Based Changes to Priority levels – Antenna Changes

• Tilts • Azimuths

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3.Troubleshooting Tools

The following tools can be used for troubleshooting:

 W-NCS

 The WCDMA Neighbouring Cell Support (W-NCS) is an Ericsson OSS Tool which provides suggestions on missing neighbour additions and

neighbour removals

 More detail on this tool can be found in ALEX

 GPEH

 The General Performance Event Handling (GPEH) tool is a feature in the Ericsson OSS that provides capability similar to a protocol analyzer. This also has visibility of internal RNC events such as Missing

neighbour etc

 This can be run on an RNC level

 CTR/Uech

 The Call Trace (CTR) tool is a feature in the Ericsson OSS that provides capability similar to the GPEH Tool

 This can be run on a Cell level for specific cell troubleshooting. These files can be read in Actix

 UETR

 The User Equipment Trace (UETR) tool is a feature in the Ericsson OSS that provides capability similar to the GPEH Tool

 This is run on a particular IMSI for specific issue troubleshooting, typically a test SIM attempting to recreate problem conditions. These files can be read in Actix