umts ran performance trouble shooting guidelines -ericsson umts mobility

UMTS RAN Performance Trouble Shooting Guidelines –Ericsson UMTS MobilityFSC Performance Engineering

Document Initiated September 2, 2008Revision Number 1.4Revision Date April 28, 2009

© Copyright 2008 T-Mobile USA, Inc. All rights reserved.Confidential and proprietary information of T-Mobile USA, Inc. Not for distribution outside T-

Mobile.

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Document InformationThe information in these materials is confidential and proprietary to T-Mobile USA, Inc. These materials are authorized for the use of T-Mobile USA service providers and their employees and agents, solely for the purposes of the agreement under which these materials are provided. The rights granted hereunder constitute a limited, nonexclusive, revocable license and not a transfer of title. Authorized T-Mobile USA service providers and their employees and agents may view, copy or print pages of these materials solely for the purposes set forth herein, but may not otherwise use, modify, copy, print, display, reproduce, distribute, transmit, publish, license, sublicense or create derivative works from these materials in whole or in part, or remove any copyright or other proprietary notices set forth herein, without the express written permission of T-Mobile USA. The information in these materials is subject to change without notice. T-Mobile USA's liability for any errors in these materials is limited to the documentary correction of errors. T-Mobile USA will not be responsible in any event for errors in these materials or for any damages, incidental or consequential (including monetary losses), that might arise from the use of these materials or the information in them. T-Mobile, the T-Mobile logo and the World Class logo are registered or unregistered trademarks of Deutsche Telekom AG.

Acknowledgements

The following individuals are responsible for contribution to the specifications, design and implementations represented in the various revisions:

Cristina Moldoveanu

Kartar Wadhwa

Marty Kameswara

Tim Zhang

Protection of Information Credibility

This document contains confidential material critical to the business and is therefore a controlled document. Outdated copies must be destroyed to prevent erroneous use of obsolete information and compromised security of confidential material. Do not e-mail this file. Do send the link to correspondents so they are assured of seeing the latest revision. The most recent revision of this file is always in softcopy and can be accessed at the following link.

http://docs.eng.t-mobile.com/InfoRouter/docs/~D671501

Note to revisers: For the above link to remain valid, you must use proper check out / check in procedures when you update this document.

Revision Code

The revision number will reflect the modifications by following the format Rev. x, y, where

X is the first digit, incremented for changes of substance, i.e. technical/procedural issues.

Y is the second digit, incremented when editorial only changes have been incorporated.

All draft/preliminary versions are 0.n; the first final version is Revision 1.0.

Revision HistoryRev. Date Author Information1.0 09/02/2008 Tim Zhang and Gurtaj Singh

AlagInitial Template for Ericsson UMTS Phase 1 Trouble Shooting Guideline document for KPI category “RETAINABILITY’

1.1 11/30/2008 Cristina Moldoveanu and Kartar Wadhwa

Updated the document with guidelines for Mobility

T-Mobile USA, INC. Confidential Rev. 1.4 April 28, 2009 2 of 31

http://docs.eng.t-mobile.com/InfoRouter/docs/~D671501


1.2 2/6/2009 Kameswara Marty Updated the document with guidelines for PS

1.3 3/17/2009 Cristina Moldoveanu and Kartar Wadhwa

Updated the document with guidelines for SHO Failures

1.4 4/28/2009 Declan Quinn/Tim Zhang Updated formatting and added flowchart



Table of Contents

1. Introduction.....................................................................................................41.1. Purpose & Scope....................................................................................................................41.2. Definitions for this Document.....................................................................................................4

2. Mobility..........................................................................................................72.1. Troubleshooting Flowchart........................................................................................................7

3. Soft/Softer Handover Failure Rate %...........................................................................83.1. Metric Definition:....................................................................................................................83.2. Ericsson KPI/Counters which can support troubleshooting SHO problems..............................................93.3. Live Data – SHO Failure Rate (%) Macro Level Analysis..................................................103.4. Typical Problems Associated with SHO............................................................................123.4.1. SHO failure due to Interference.......................................................................................123.4.2. SHO failure due to Primary Scrambling Code Collision....................................................123.4.3. Missing Neighbor Definitions...........................................................................................123.4.4. Neighboring sites T1 /Hardware issues............................................................................123.4.5. E/// UTRAN software bug (UTRAN cell locked, sub channels unlocked)............................133.4.6. UMTS cell Not-On-Air (no RBS on site also) but reporting incoming SHO failures.............133.5. Worst Cells Analysis.........................................................................................................13

4. IRAT Failure Rate %............................................................................................144.1. Metric Definition..................................................................................................................144.2. Ericsson CS IRAT Execution Failure Reason Counters.......................................................................174.3. Ericsson PS IRAT Failure and HS Cell change failure Reason Counters.................................................184.4. Live Data – CS IRAT HO Failure Rate % Macro Level Analysis..........................................224.5. Live Data – IRAT Ho Failure Rate % - Drill down Analysis – Cell / Neighbor Specific.........274.6. T-PIM Reference...............................................................................................................27

5. Troubleshooting Tools.........................................................................................296. References................................................................................................30



1. Introduction

1.1. Purpose & ScopeThe intent of this document is to provide UMTS Trouble Shooting and Optimization from KPI and Counter perspectives for Ericsson (E///) Mobility 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 P6 release of 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.

1.2. Definitions for this Document

Term or Acronym Definition

3GPPThird 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

GERAN GSM EDGE RAN

GSM Global System for Mobile Communications




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 RNCs

KPI Key Parameter Indicator

LA Location Area

LAI Location Area Indicator

NBAP Node B Application Part

Node BLogical 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

RB Radio Bearer

RBSRadio Base Station – another name for 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 Telecommunication Services

UTRAN UMTS Terrestrial Radio Access Network

WCDMA Wideband Code Division Multiple Access



2. MobilityMobility is defined as the ability of a user to move between neighboring UMTS and GSM Cells retain its requested service (CS or PS) once connected. This aids the Retainability of the UMTS network. 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 into two main areas:

Soft/Softer Handover (SHO)

Inter Radio Access Technology (IRAT)

2.1. Troubleshooting FlowchartThe following flowchart may be useful for troubleshooting the voice drop issues based on the problem areas



3. Soft/Softer Handover Failure Rate %This KPI provides the percentage of Soft/Softer HO attempts that failed to access a target channel due to any reason for CS voice and PS R99 Data. Soft handover allows a UE to be simultaneously connected to multiple RBS with maximum number of Radio links limited by a RNC level parameter settings and by doing so creates seamless mobility. The soft handover procedure utilizes intra-frequency reporting to control mobility.

Soft and Softer Handover is controlled through the events 1a, 1b, 1c and 1d:

• 1a: A new candidate for the active set enters reporting range

• 1b: A cell in the active set leaves the reporting range

• 1c: A cell not in active set becomes stronger than a cell in the active set

• 1d: Any cell becomes better than the best cell in the active set

3.1. Metric Definition:

This metric will help engineers to be able to identify SHO issues and it can be run on Cell/RNC/Market/Region level. The main report for identifying and troubleshooting SHO issues in T-PIM is the Mobility Report. Cell to Cell stats (neighbor relations) can be obtained using “3G to 3G cell relations” report.

This KPI is pegged at Target cell (means the cell which could not be added to Active set) for both CS & PS R99 data calls.

KPI – SHO Failure Rate % -

KPI KPI Definition KPI Formula

Soft/Softer Handover Failure

Rate (%)

This metrics measures soft/softer handover failure rate or Active Set update failure rate. The counter is increased if during an attempt to add an

RL any of the following occur: admission is not granted, no DL channelization code is allocated, the RL

Setup procedure fails (NBAP Radio link Setup Failure received), RL Addition procedure fails (NBAP Radio link Addition Failure received), RL Setup or Addition procedure times out in the RBS, the Active Set Update procedure fails (RRC Active Set Update Failure received) or Active Set Update procedure times out in the UE. The counter only monitors UEs in

the SRNC and it affects cells which can not enter into the active set.

100*[pmNoTimesCellFailAddToActSet/(pmNoTimesRlAddToActSet+pmNoTimes

CellFailAddToActSet)]

Definitions of E/// counters used to build metrics –



Counter pmNoTimesRlAddToActSetDescription Number of times an RL is added to an active set, also increased at RL replace

This counter is increased when a new RL is successfully added to an active set. The counter is increased after a handover proposal has been received from the handover evaluation function, admission control has been granted, DL channelization code has been allocated for the new cell, RL Setup or RL Addition procedure is successfully completed with the RBS (NBAP Radio link Setup Response or Radio link Additoin Response received), the Active Set Update procedure is successfully completed with the UE (RRC Active Set Update Complete received), and the appropriate parameters are available.

Note: This counter only monitors RLs for cells in the SRNC. I f an RL is replaced in an active set, this counter is increased for the cell which is added.

MO Class UtranCellCounter Type

PEG

ST CS, PSUnit -Counter pmNoTimesCellFailAddToActSetDescription Number of times a cell fails to be added to an active set, also increased at failure at

RL replaceThis counter is increased if during an attempt to add an RL any of the following occur: admission is not granted, no DL channelization code is allocated, the RL Setup procedure fails (NBAP Radio link Setup Failure received), RL Addition procedure fails (NBAP Radio link Addition Failure received), RL Setup or Addition procedure times out in the RBS, the Active Set Update procedure fails (RRC Active Set Update Failure recevied) or Active Set Update procedure times out in the UE.

Note: This counter only monitors UEs in the SRNC. I t affects cells which can not enter into the active set.

MO Class UtranCellCounter Type

PEG

ST CS, PSUnit -

Condition

Condition

3.2. Ericsson KPI/Counters which can support troubleshooting SHO problems Following KPI’s can help to troubleshoot the causes for high SHO failures.

KPI KPI Definition KPI Formula

Voice RL Addition/replacement Failure rate (%)

Voice RL addition/replacement Failure rate. This is pegged at Source cell but only for SRNC.

100*(1-(pmRlAddSuccessBestCellSpeech/pmR

lAddAttemptsBestCellSpeech))

Voice RL Addition/replacement Failures

Voice RL Addition/replacement Failures. This is pegged at Source cell but only for SRNC.

(pmRlAddAttemptsBestCellSpeech-pmRlAddSuccessBestCellSpeech)

PS low RL Addition/replacement Failure rate (%)

PS Low (<64) RL addition/replacement Failure rate. This is pegged at Source cell but only for SRNC.

100 *(1-( pmRlAddSuccBestCellPacketLow / pmRlAddAttBestCellPacketLow))

PS high RL Addition/replacement Failure rate (%)

PS high (> 64) RL addition/replacement Failure rate. This is pegged at Source cell but only for SRNC.

100 *(1-( pmRlAddSuccBestCellPacketHigh / pmRlAddAttBestCellPacketHigh))

RL additon/setup failure due to admission control

Number of Radio Link setup or Radio Link addition requests denied by admission control. This is pegged at Congested cell.

pmNoRlDeniedAdm



3.3. Live Data – SHO Failure Rate (%) Macro Level AnalysisThis section covers analysis of SHO Failure Rate (%) and identification of issues using the available E/// SHO failures reason Counters.

In the analysis; data for New Jersey market from the NE Region has been presented from 10/20 to 11/30/2008.

New Jersey market has 2 RNC NYRNC005 & 6 with total primary traffic of around 75000 Erlangs.

Number of SHO attempts are approximately 22 Million/day

SHO Failure Rate % (average) for NJ Market is 0.05%.

0

5,000

10,000

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0.00

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01.2

6.20

0901

.27.

2009

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0901

.29.

2009

01.3

0.20

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2009

02.0

1.20

0902

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3.20

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3.20

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2009

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7.20

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1.20

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2009

Voice

Traffi

c (Er

lang

)

SHO

Failu

re ra

te %

NJ Market Voice Tarrfic & SHO Failure Rate

Voice Traffic (Erlang) Soft/Softer Handover Failure Rate (%)

Figure: New Jersey SHO Failure Rate is mostly influenced by problems other than Radio Failures, as with the increase in traffic, failures are not increasing.



0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0

500

1,000

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01.2

6.20

0901

.27.

2009

01.2

8.20

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.29.

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0.20

0901

.31.

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02.0

1.20

0902

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3.20

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5.20

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9.20

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1.20

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5.20

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2009

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7.20

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2009

02.1

9.20

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.20.

2009

02.2

1.20

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.22.

2009

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3.20

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5.20

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2009

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Soft

Han

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s

RL ad

ditio

n/se

tup

failu

res

NJ Market Voice Tarrfic & SHO Failure Rate

Soft Handover Failures RL additon/setup failure due to admission control

Figure: Highlighting point of this chart is some SHO failures due to Admission Control, thus indicating congestion on certain sites which must be checked on priority.

0

10000

20000

30000

40000

50000

60000

70000

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6.20

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SHO

Fai

lure

s

NJ Market CS & PS Calls SHO Failures Distribution

Soft Handover Failures Voice RL Addition/replacement Failures Packet RL Addition/replacement Failures

Figure: This chart shows SHO failures distribution between CS & PS calls. It can be noticed that PS calls SHO failures are suddenly spiking on certain days but CS SHO failures are not. In these events, PS core network alarms and availability must be checked to identify the root causes of the problem.

If both CS & PS both type of calls are reporting high SHO failures, then issue must be related to Cells/Sites/RNC problems.



3.4. Typical Problems Associated with SHOMajority of the SHO issues in NJ / Northeast markets have been seen due to following probable causes:

1) Failures due to interference & therefore poor areas of dominance.

2) Primary Scrambling Code collision

3) Missing neighbors

4) Neighboring sites T1 /Hardware issues.

4) E/// UTRAN software bug (cell locked, sub channels unlocked)

5) UMTS cell not on air (without RBS also) but resulting in SHO failures.

3.4.1. SHO failure due to Interference

It has been seen that SHO failure is most likely to occur if there are too many servers for a given area, although they might be neighbors they are also interferers. To resolve this issue, it is important to determine which cell is the interferer, data collection using a TEMS kit will help resolve this issue, antenna down tilts, reorientation or the addition of a new site will ensure that the interferer is removed and pilot dominance is established in the given area.

3.4.2. SHO failure due to Primary Scrambling Code Collision

Scrambling code collision is also a major cause for SHO failures. This has been in seen NJ market on few sites where neighbors with common PSC were experiencing more SHO failures than other neighbors. Although these neighboring sites with common PSC were at a reasonable distance from each other, yet both experienced high incoming SHO failures from their common neighbors.

These sites were optimized to have different PSC and in some cases, antennae were down-tilted to limit overshooting.

3.4.3. Missing Neighbor Definitions

Missing Neighbor definitions are also causing the serving cell dragging and thus resulting in SHO attempts happening in poor radio conditions or to “not the best” neighbors. This ultimately increases the probability for SHO failures with impact on mobility & retainability aspects of the call. Hence, it’s necessary to determine neighbor relationships are defined for the first, second, third or even fourth tier (where applicable) neighbors. Excessive distance (greater than 5km) between neighbor cells should not be considered for defining neighbors but by using WNCS results, this can also be validated. Recommendation is to use WNCS data on a regular basis to optimize neighbor list (addition / deletion/ priority) as per the changing traffic pattern and avoid SHO failures due to this reason.

Extra tilt for sites should be investigated for over-shooting sites causing missing neighbour and SHO issues.

3.4.4. Neighboring sites T1 /Hardware issues

Neighbor sites bouncing T1 or Hardware issues are commonly seen as the biggest potential reason for SHO failures except radio causes. Cell to Cell (neighboring pair) relationship SHO failure can be



used to identify which neighboring is causing high soft handover failures to accordingly act on the problem.

3.4.5. E/// UTRAN software bug (UTRAN cell locked, sub channels unlocked)

Another major reason seen for SHO failures in New Jersey / Northeast markets is the SHO failures to the neighboring cells which were in Locked-Disabled state but their sub-channels remained in Unlocked-disabled state which meant channels were transmitting although cell was locked. This resulted in these “mismatched state” site’s neighbors to attempt incoming Soft handovers to these sites and failing. This was identified as a critical problem and E/// has loaded RBS patch EU 17 (P.6.0.2-17) for T-Mobile E/// UMTS markets to eliminate this mismatch between cell & it’s channels states, however the problems have yet been reported in very few cases after loading this patch but this is to yet to be confirmed.

3.4.6. UMTS cell Not-On-Air (no RBS on site also) but reporting incoming SHO failures

SHO failures have been noticed on some sites which were Not-on-Air” but reported high incoming SHO failures. When investigated, cells were in Locked-disabled state and there was no RBS on site, yet neighbors were defined to this site. To make this issue complex, it was identified that replacement/substitute site was using the same Primary Scrambling Code but had no neighbors and was in Unlocked-disabled state meaning cell was locked but channels were transmitting.

To resolve such SHO failures issues, sites which are Not-On-Air and not required in the network were completely deleted from OSS & RNC along with neighbor relations. Neighbors were added to replacement/substitute site, cell & channels status was matched to status “Enabled-Unlocked” or “Disabled-Locked” as required.

The recommendation for these issues is to clean the RNC/OSS database completely in case any cell is not required in network including its neighbor relations, thus leaving no chance for any SHO failures reported due to this issue.

3.5. Worst Cells AnalysisAll of the mentioned metrics are pegged on Cell level. The Worst Offenders in an RNC/Market/Region level should be ranked by the following metrics:

SHO failures

Voice RL Addition/replacement failures.

PS Low (<64) Addition/replacement failures.

PS High (<64) Addition/replacement failures.



4. IRAT Failure Rate %This KPI provides the percentage of IRAT HO attempts that failed to cease GSM target channel due to any reason for service type CS voice and PS Data.

4.1. Metric Definition CS IRAT failure rate can be divided into two categories:

a) CS IRAT HO Preparation Failure Rate %

b) CS IRAT HO Execution Failure Rate %

Other definitions can be used for the PS and HS Services:

a) PS Interactive IRAT Failure Rate %

b) PS Interactive IRAT HO Failures

c) HS Cell Change Failure Rate %

d) HS Cell Change Failures

Find below the Metric Definitions for KPIs as per T-PIM Specs for E/// -

KPI – CS IRAT Preparation Failure Rate % -

KPI – CS IRAT Execution Failure Rate % -

KPI – PS Interactive IRAT Failure Rate % -



KPI – PS Interactive IRAT HO Failures -

KPI – HS Cell Change Failure Rate % -

KPI – HS Cell Change Failures -

Definitions of E/// counters used to build metrics –



Counter Name

pmnoattoutirathospeech

Description

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. I f the best cell in the active set has no cell relation towards the target cell, the counter is not stepped.

ConditionThe counter is increased when RNC sends "HANDOVER FROM UTRAN COMMAND". This counter will only be incremented in the SRNC.

MO Class GsmRelationCounter Type

PEG

ST CSCounter Name

pmnosuccessoutirathospeech

Description 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. I f the best cell in the active set has no cell relation towards the target cell, the counter is not stepped.

Condition 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.

MO Class GsmRelationCounter Type

PEG

ST CS

4.2. Ericsson CS IRAT Execution Failure Reason CountersFind below E/// definition of CS IRAT execution failure reason counters -



4.3. Ericsson PS IRAT Failure and HS Cell change failure Reason Counters


20

CS IRAT HO Failures

CS IRAT HO Execution Failures

pmNoFailOutIratHoSpeechUeRejection

pmNoFailOutIratHoSpeechReturnOldChNotPhyChFail

pmnofailoutirathospeechgsmfailpmNoFailOutIratHoSpeechReturnOldChPhyChFail

CS IRAT Handover Failure Flowchart

CS IRAT HO Preparation Failures


Understanding and representation of the E/// IRAT failures reason counters

Voice IRAT HO Preparation failures – pmofailoutirathospeechgsmfail Voice IRAT HO Execution failures - pmnoattoutirathospeech – pmnosuccessoutirathospeech Voice IRAT HO Execution failures and return to Old Channel; due to Physical

Channel Failure – pmNoFailOutIratHoSpeechReturnOldChPhyChFail (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' for the best cell in the active set).

Voice IRAT HO Execution failures and return to Old Channel; not due to Physical Channel Failure - pmNoFailOutIratHoSpeechReturnOldChNotPhyChFail (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' for the best cell in the active set).

Voice IRAT HO Execution HO Failure -UE rejection- pmNoFailOutIratHoSpeechUeRejection (Number of failed outgoing (to GSM) inter-RAT handover, rejected by UE, for 'Conversational speech RAB' for the best cell in the active set).


21

UE Cell change order from UTRAN ---- SNRC

Iu Release command -pmNoOutIratCcSuccess++

PS IRAT HO Attempts – pmNoOutIratCcAtt++

Outgoing IRAT Cell change request by UE

pmNoOutIratCcReturnOldCh ++

Send message

End Outgoing IRAT Cell change

Start Handover Evaluation of MR 3a

Start Timer waiting for Iu release command from PS CN

Cell change order from Utran Failure

Signaling Connection Handling

Message ReceivedConfigure PS to

resume DL Traffic

Is PS reconfiguration successful?

YES

NO

End of RRC connection



PS IRAT Handover Failure Flowchart


PS IRAT

PS Cell Change is commonly known as PS IRAT. Unlike CS IRAT where resources in 2G are always allocated (preparation phase) before the UE attempts a Handover (execution phase), this procedure for PS services is quite similar to cell –reselection.

1) The Inter-system change for PS interactive services normally experience quite long outage times before the session can be reestablished on the GSM side. There are no normal tuning activities that can be performed in the radio network to shorten this time.

2) The outage time can be divided into two parts. a. After receiving the request for PS Cell Change by UE, the RNC will stop all packet

transfer from/to the UE. The first radio outage part depends mostly on the UE and consists of the time it takes for the UE to reselect to the GSM cell and then perform LA and RA updates. This typically takes 8–10 seconds.

b. The second part is the application outage that depends on the application, the protocol, and on the TCP/IP procedures, before the application is running normally again. Example: During market IRAT drives as part of UMTS Pre-launch activities, we found that when the phone was doing FTP, the interruption was around 10 - 12 seconds.

The total interruption time experienced by the user doing a PS data session during PS Cell Change can be as long as 22 seconds

4.4. Live Data – CS IRAT HO Failure Rate % Macro Level Analysis

This section covers analysis of IRAT HO Failure Rate % for E/// n/w and identification of issue using the available E/// IRAT failure reason Counters.

In the analysis; data for NY from the NE Region has been presented from 10/20 to 11/30/2008 (since Google G1 phone launch until the time of writing this document). The following chart clearly indicates the following

NY market has 4 RNC NYRNC001 to 4 with total primary traffic of around 75000 Erlangs.

Number of IRAT attempts are approx 274800/day

CS IRAT HO Execution Failure Rate % (average) for NY is 4%

CS IRAT HO Preparation Failure Rate % (average) for NY is 2.5%

CS IRAT HO Failure Rate (Preparation + Execution) % (average) is 6.41%

CS IRAT HO Drop rate (Failed to return to old channel) % (average) is 0.31%



0.001.002.003.004.005.006.007.008.009.0010.0011.0012.0013.0014.0015.0016.0017.0018.0019.0020.00

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

10.2

2.20

0810

.23.

2008

10.2

4.20

0810

.25.

2008

10.2

6.20

0810

.27.

2008

10.2

8.20

0810

.29.

2008

10.3

0.20

0810

.31.

2008

11.0

1.20

0811

.02.

2008

11.0

3.20

0811

.04.

2008

11.0

5.20

0811

.06.

2008

11.0

7.20

0811

.08.

2008

11.0

9.20

0811

.10.

2008

11.1

1.20

0811

.12.

2008

11.1

3.20

0811

.14.

2008

11.1

5.20

0811

.16.

2008

11.1

7.20

0811

.18.

2008

11.1

9.20

0811

.20.

2008

11.2

1.20

0811

.22.

2008

11.2

3.20

0811

.24.

2008

11.2

5.20

0811

.26.

2008

11.2

7.20

0811

.28.

2008

11.2

9.20

0811

.30.

2008

%

Traffi

c (E

rlan

g) /

IRA

T To

tal H

O A

ttem

pts (

num

bers

)

NY Market Voice Traffic, CS IRAT HO Total Attempts & Failure Rate

IRAT HO Failure Rate Voice Traffic (Erlang) Voice IRAT HO Total Attempts



0.001.002.003.004.005.006.007.008.009.0010.0011.0012.0013.0014.0015.0016.00

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

10.2

2.20

0810

.23.

2008

10.2

4.20

0810

.25.

2008

10.2

6.20

0810

.27.

2008

10.2

8.20

0810

.29.

2008

10.3

0.20

0810

.31.

2008

11.0

1.20

0811

.02.

2008

11.0

3.20

0811

.04.

2008

11.0

5.20

0811

.06.

2008

11.0

7.20

0811

.08.

2008

11.0

9.20

0811

.10.

2008

11.1

1.20

0811

.12.

2008

11.1

3.20

0811

.14.

2008

11.1

5.20

0811

.16.

2008

11.1

7.20

0811

.18.

2008

11.1

9.20

0811

.20.

2008

11.2

1.20

0811

.22.

2008

11.2

3.20

0811

.24.

2008

11.2

5.20

0811

.26.

2008

11.2

7.20

0811

.28.

2008

11.2

9.20

0811

.30.

2008

%

Traffi

c (E

rlan

g) /

IRA

T To

tal H

O A

ttem

pts (

num

bers

)

NY Market Voice Traffic, CS IRAT HO Total Attempts & Preparation Failure Rate

Voice IRAT HO Execution Failure Rate (%) Voice Traffic (Erlang) Voice IRAT HO Total Attempts

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

10.2

2.20

0810

.23.

2008

10.2

4.20

0810

.25.

2008

10.2

6.20

0810

.27.

2008

10.2

8.20

0810

.29.

2008

10.3

0.20

0810

.31.

2008

11.0

1.20

0811

.02.

2008

11.0

3.20

0811

.04.

2008

11.0

5.20

0811

.06.

2008

11.0

7.20

0811

.08.

2008

11.0

9.20

0811

.10.

2008

11.1

1.20

0811

.12.

2008

11.1

3.20

0811

.14.

2008

11.1

5.20

0811

.16.

2008

11.1

7.20

0811

.18.

2008

11.1

9.20

0811

.20.

2008

11.2

1.20

0811

.22.

2008

11.2

3.20

0811

.24.

2008

11.2

5.20

0811

.26.

2008

11.2

7.20

0811

.28.

2008

11.2

9.20

0811

.30.

2008

%

Traffi

c (E

rlan

g) /

IR

AT

HO

Exe

cuti

on

att

em

pts

(n

um

be

rs)

NY Market Voice Traffic, CS IRAT Attempts & Execution Failure Rate

Voice IRAT HO Execution Failure Rate (%) Voice Traffic (Erlang) Voice IRAT HO Execution Attempts



0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

01.0

1.19

0001

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1900

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1900

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1900

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1900

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1900

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IRA

T Ex

ecuti

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(Num

bers

)

IRA

T Ex

ecuti

on A

ttem

pts (

num

bers

)

NY Market CS IRAT Exceution Attempts & Failure reasonsIRAT HO Failure due to physical channel failure, ROC Voice IRAT HO Execution Attempts

IRAT HO Failures not due to physical channel failure, ROC IRAT HO Failure due to UE rejection

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

01.0

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1900

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IRA

T Ex

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ps (

Num

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)

IRA

T Ex

ecu

tion

Att

em

pts

(nu

mb

ers)

NY Market CS IRAT Exceution Attempts & Drops (Fail to return to old channel)

IRAT HO Drops Voice IRAT HO Execution Attempts



0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

01.0

1.20

0901

.02.

2009

01.0

3.20

0901

.04.

2009

01.0

5.20

0901

.06.

2009

01.0

7.20

0901

.08.

2009

01.0

9.20

0901

.10.

2009

01.1

1.20

0901

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2009

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3.20

0901

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2009

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5.20

0901

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2009

01.1

7.20

0901

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2009

01.1

9.20

0901

.20.

2009

01.2

1.20

0901

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2009

01.2

3.20

0901

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2009

01.2

5.20

0901

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2009

01.2

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0901

.28.

2009

01.2

9.20

0901

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2009

01.3

1.20

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2009

02.0

2.20

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2009

02.0

4.20

0902

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2009

PS IR

AT Fa

ilure

Rat

e %

PS IR

AT A

ttem

pts

NY RNC 3 PS Interactive IRAT Attempts & Failure Rate

PS Interactive IRAT Failure Rate (%) PS Interactive IRAT Attempts

Find below summary of clear indication as drawn from the IRAT HO Failure counters –

High number of Voice IRAT failures reported on 10/29, 11/1 and 11/5/2008 are actually preparation failures and are due to NYMSS900 outages on these days.

Voice IRAT Execution failure rate is decreasing with the increase in Voice traffic & IRAT attempts indicating that higher failure rate reported earlier was not due to WCDMA pilot pollution or GSM interference otherwise failures should have increased with increase in traffic / IRAT attempts.

Voice IRAT preparation failure rate is still varying around between 1.8 to 2.2% mark despite the increase in IRAT attempts indicating GSM congestion is not the prominent cause for these failures otherwise this failure rate should have increased with increase in traffic / IRAT attempts.

Voice IRAT Preparation failure rate decreased slightly after NYMSS900 multiple outages from 10/29 to 11/5/2008, thus adding a point to above mentioned reason that GSM congestion is not the prominent cause for these preparation failures

Random spikes between 11/17 to 11/25 seen in IRAT HO preparation failure rate are due to NY market (Nortel platform BSC) ongoing V17 ware upgrade

Voice IRAT HO execution failure reasons distribution clearly shows all execution failures are due to Physical channel failures and not due to other reasons including UE Rejection.

Voice IRAT drop contribution is very low and varies around 0.3% mark. PS IRAT Failure rate is decreasing with increase in IRAT attempts. Recent increase in PS IRAT attempts are due to changes in IRAT e2d triggers &service offset

applied to all the cells in NYRNC003 on 2/3/2009, allowing IRAT on PS 128 & 384 RAB’s.



4.5. Live Data – IRAT Ho Failure Rate % - Drill down Analysis – Cell / Neighbor Specific

Market needs to analyze 3G to 2G neighbor relation stats very closely to identify the worst relations and work closely with the region to come up with Voice IRAT HO failures troubleshooting to create tangible actions for the following Categories –

RF Related

3G-2G Neighbor Optimization including addition, deletion, re-prioritization.

Verify the worst 3G-2G neighbor relations for preparation & execution failures and troubleshoot the problem due to coverage, pollution/ interference, BSIC collision, datafill inconsistencies, GSM congestion etc.

Physical coverage restriction by tilts, reorientation to avoid overshooting and HO attempts to far by neighbors etc.

RF Optimization using Features/Parameters

Identify network core area cells with high % of 3G calls ending at 2G network and troubleshoot coverage / pilot pollution problems.

Others/Miscellaneous

Network traffic growth impact on IRAT performance

Regular network UTRAN parameters consistency audit.

Datafill consistencies check to ensure neighbors and other relevant details – LAC, CI, BCCH, and BSIC are defined correctly. (Core, BSS/OSS team involvement).

Handset related performance analysis (call tracing with Tier-II involvement) to distinguish between various handsets response during IRAT / compressed mode event and their subsequent impact on network performance.

Core network unavailability impact.

GSM network TCH blocking analysis – to ensure high preparation failures are not due to GSM network congestion.

Inter MSC / Intra MSC boundaries analysis to evaluate the impact of core network topology on Voice IRAT HO performance.

4.6. T-PIM Reference



3G to 2G cell relation 1

Mobility Report 1



5. Troubleshooting ToolsThe following tools can be used for troubleshooting:

Tektronix K-18

This is a protocol analyzer used for analysis of the Iu and Iub links and the layer 1, 2 and 3 messaging. This can be used for further analysis of the call flows

More detailed information on this can be found in the Tektronix Documentation

W-NCS

The WCDMA Neighboring 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

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




6.References1. 3GPP TS 25.331 V 5.19.0 “UMTS Radio Resource Control Protocol

Specification”.

2. Ericsson Alex

3. Alejandro Aguirre, Sireesha Panchagnula Ericsson UTRAN Parameters.

4. UMTS Network KPI, U12 UMTS Network KPI v6.14 080406TMO LR.doc

5. UMTS Network KPI Level 2, UMTS Network KPI Level-2_v1_20070205ERI_Updated.doc

6. 3GPP TS 25.331, UMTS RRC protocol specification.

7. 3GPP TS 25.211 V 5.8.0, “UMTS Physical channels and mapping of transport channels onto physical channels”.

8. 3GPP TS 25.413 V 5.12.0, “UTRAN Iu Interface RANAP Signaling”.

9. 3GPP TS 25.214, ”UMTS Physical Layer Procedures FDD”.

10.Ericsson Product Documentation 58/1551-AXD 105 03/1 Uen G, “Performance Statistics RNC 3810”.


umts ran performance trouble shooting guidelines -ericsson umts mobility

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