Key Performance Indicators Reference

Prepared by:

Jefferson Aboo

NPO-Mumbai

08/01/2012

Introduction

This document is designed for personnel involved in the performance evaluation and the optimization of UMTS Terrestrial Radio Access Networks (UTRAN) to get the basic idea of UMTS KPIS that need to be monitored

AccessibilityKPIs are:CSV Accessibility rate (RCOM KPI -Voice Access Success Rate (%))Threshold –Should be greater than 98%

CSD Accessibility rate Video BH (RCOM KPI –Video Access Success Rate (%)Threshold –Should be greater than 98%

PSD Accessibility rate (RCOM KPI - HSDPA + HSUPA + PS(R99) Access Success Rate(%) )Threshold –Should be greater than 98%

Call setup processThe call setup process consists of different procedures depending on what kind ofsession/service type is required (for example CS or PS). RRC ConnectionEstablishment and RAB Establishment procedure are the main procedures on theUTRAN side.With the RRC Connection Establishment procedure, the UE requests resources fromthe UTRAN and executes the transition from Idle to CELLDCH state, entering theUTRAN RRC Connected Mode. The UTRAN allocates resources in terms of radioLinks.With the RAB Establishment procedure, all the requested resources are allocated by theCore Network and by the UTRAN in terms of Radio Access Bearers (RABs) while theUE stays in CellNDCH state and acknowledges the resources setup.The call is successfully set-up only if both procedures are successfully completed.

Network level access phaseDuring the network level access phase, the UE has to successfully perform the cell(re)selection process as well as to gain network access using the Random Accessprocedure.RRC Connection Establishment phaseDuring the RRC Connection Establishment phase, the UE requests resources from theUTRAN and executes the transition from Idle to CellNDCH state and enters theUTRAN RRC Connected Mode. The UTRAN allocates resources in terms of radiolinks.

RAB establishment phaseDuring the RAB Establishment phase, the requested resources are allocated by theCore Network and by the UTRAN in terms of Radio Access Bearers (RABs) while theUE stays in CellNDCH state and acknowledges the resources setup.

Determination of accessibility problemIn order to quickly determine whether there are severe problems in the UMTS network,it is possible to analyze the general satisfaction level, from a network point of view, ofthe UMTS mobile subscriber about the network accessibility

Abnormal accessibility rate valuesWhen one of the Accessibility rate values is very low, this can be caused by manydifferent issues. Therefore, it is advised to localize the issue by analyzing theperformance measurements and KPIs separated over the accessibility call phases:Network level access phaseRRC connection establishment phaseRAB establishment phase

RRC Connection establishment procedureIn general the RRC connection establishment procedure may occur in differentscenarios such as:Network attach (the UE is switched on and moves to Idle state)Location updateMO/MT call setup (the UE moves from Idle state to CellDCH state).RRC Connection Establishment starts with the successful receipt at the RNC of theRRC Connection Request message. This means that cell selection/re-selection as wellas Random Access Detection procedures have been successfully completed.Call setup stagesIn case of a mobile originated call setup, the RRC Connection Establishment proceduremay be categorized into the following basic stages:1. Call Admission Control (CAC) at the RNC2. Node B Application Part (NBAP) Radio Link Setup (including transport bearer andsynchronization)3. RRC Connection Setup.

RAB establishment procedureAs soon as the RRC connection establishment procedure has been completed, the callsetup procedure is finalized via the RAB Establishment procedure.The RAB Establishment procedure is executed in case of call setup with:Packet-switched (PS) callsCircuit-switched (CS) calls.RAB establishment initiatorsThe RAB Establishment procedure is initiated by the core network, this means SGSNfor PS calls or 3G-MSC for CS calls, upon receipt of an RRC/RANAP Uplink DirectTransfer message from the UE requesting either a Packet Data Protocol (PDP) ContextActivation (PS call) or a Call Setup (CS call). This procedure is successfully completedupon receipt of RANAP RAB Assignment Response message at the core network.

The RAB Establishment Success Rate is the percentage of calls for all supported service types that successful established a RAB, against the number of valid calls requested/attempted. Depanding on Qos requirement all applications are divided into 4 classes:

Conversational

Interactive

Streaming

Backgroud

Beside delay in communication, BER is also an important Qos criterion(application sensitivity to transmission error )

RCOM KPIS

1.CSV Access Failure Rate .

In the above KPI we are calculating Access Failure Rate for voice .Which contains 2 part1.RRC 2)RAB

1.RRC –2 Types of RRC request taken into consideration – Conversational(Originating & terminating ) and Emergency –these are the only 2 type of RRC request used for making Voice calls in 3G 2.RAB – CS, conversational：AMR 12.2 is the type of RAB used5 for making 3G voice Call . CS, conversational：64K is the type of RAB used5 for making Vide call.PS, streaming RABS – 32, 64 , 128 ,384 etcSimilarly for PS interactive & Background.

2.CSD Access Failure Rate .

In the above KPI we are calculating CS Data Call (Video) Access Failure Rate .

Which contains 2 part

1)RRC 2)RAB

1.RRC –1 Types of RRC request taken into consideration – Conversational(Originating & terminating )2.RAB – CS RAB(64Kbps) is the type of RAB used for making 3G video Call .

3. PSD (HSDPA+HSUPA+PS (R99)) Access Failure Rate .

In the above KPI we are calculating Access Failure Rate for all the PS Services (HSDPA+HSUPA+PS)

KPI contains 2 part

1)RRC 2)RAB

1)RRC – 3 types of RRC request taken into consideration – Background ,Interactive. Note:Streaming type also has to be taken into consideration current formula this is not taken into consideration .

2)RAB – 4 Types of PS RAB Taken into consideration – PS Conversation ,PS Streaming ,PS Interactive and PS Background

RetainabiltyAs soon as the call is successfully set up, the second factor influencing UMTS userPerception is the probability of maintaining the call, as opposed to the probability ofdropping the call.A call drop is defined as an abnormal termination of a voice/data session due to anyreason causing the user to re-initiate the session. Where a drop on a PS session willstill result in PDP context preservation, and the end user will be able to re-establishseamlessly (with some delay). PS drops are generally not as severe for end users as CSdrops.On the UTRAN side, KPI CS&PS Drop Rate, defined as the percentage of droppedRAB due to any reason against the total number of established RABs for all services,can be calculated.

Measurement classificationCall drop defined by the measurement - CS call drop & PS call drop

KPIs are:

CSV Drop rate(RCOM Name -Voice Drop Rate (%))Threshold – Should be less than 2%

CSD Drop Rate(RCOM Name- Video Call Drop rate(%)Threshold – Should be less than 2%

PS Drop Rate(RCOM Name- HSDPA + HSUPA + PS Drop Rate (%)Threshold – Should be less than 2%

Dropped RABs are identified by either a RANAP Iu Release Request message or RANAP Reset Resource message sent by the RNC to the core network. When a Release Request message is sent, the resources on the UTRAN and core network are released.Note: For PS calls the PDP context will not be released.

CSV Drop rate(RCOM Name -Voice Drop Rate (%))Threshold – Should be less than 2%

KPI Formula Counter

CSV Drop Rate (AMR RAB Abnormal Release/AMR RAB Release)*100%

[Number of CS AMR RABs Abnormally Released for Cell]/([Number of CS AMR RABs Abnormally Released for Cell]+[Number of CS AMR RABs Normally Released for Cell(not including WB-AMR)])*{100}

This measurement helps evaluate the call drop rate of CS services. This counter is measured when the RNC initiates the abnormal release procedure through the RAB RELEASE REQUEST and IU RELEASE REQUEST messages.

KPI contains only RAB Part (AMR RABs ).

CSD Drop Rate(RCOM Name- Video Call Drop rate(%)Threshold – Should be less than 2%

KPI contains only RAB Part (64kbit/s RABs).

This measurement helps evaluate the call drop rate of Video call services in a RNC or cluster. This counter is measured when the RNC initiates the abnormal release procedure through the RAB RELEASE REQUEST and IU RELEASE REQUEST messages.

PS Drop Rate(RCOM Name- HSDPA + HSUPA + PS Drop Rate (%)Threshold – Should be less than 2%

This measurement helps evaluate the call drop rate of PS services in a RNC or cluster. This counter is measured when the RNC initiates the abnormal release procedure through the RAB RELEASE REQUEST and IU RELEASE REQUEST messages.Note: The cell level counter calculates only the RAB releases on the SRNC, whereas the result of the above formula includes the R99 call drop and HSPA call drop.

Possible failing reasons for abnormal rab releaseThe major components that constitute RAB Drops may be classified as follows:

• Radio Link Failure, caused by:– poor RF coverage– poorly defined neighbor list– poor Primary Scrambling Code (PSC) plan-pilot pollution– DL power overload.– UL Interference

• Operator intervention (for example reset, lock action)• Inter-RAT handover due to supervision timer expiry (UMTS to GSM)• URANPCH time-out (due to the UE not performing a periodical URA update)• Iu, Iub and Iur link failure• RRC signal connection release Indication sent by the UE.• Failures during SRNS Relocation procedure• Unsuccessful termination of the Iu Rate control procedure• UE Inactivity.

MobilityWCDMA mobility can be divided into different categories.

Soft handover Soft/Softer handover

Hard handover Intra-frequency hard handover

Inter RAT handover Inter-RAT CS handover Inter-RAT PS handover

HSDPA handover Handover between HSDPA cellsHandover between HSDPA and DCH

RCOM KPIs Monitored in Mobilty are :

SHO Failure Rate (RCOM Name - SHO Failure Rate (%))Threshold – Should be less than 1%

CSV IRAT Failure Rate (RCOM Name- IRAT Failure Rate (%)Threshold – Should be less than 2%

Soft/Softer Handover Overhead (RCOM Name- Soft/Softer Handover Overhead (%)Threshold – Should be between 30% & 40%

Soft handover Success Rate

In UMTS networks soft/softer handover is the basic feature that ensures seamlessmobility as well as call performance and quality improvements.

Soft/softer handover procedure steps

The soft/softer handover procedure steps for UE in CellNDCH state are:1. Reporting of soft/softer handover triggering event to the UTRAN via an RRCMeasurement report message2. Set up resources in the UTRAN via NBAP procedure (in case of addition orReplacement)3. Soft/softer handover execution via RRC active set update procedure. Soft/softerhandover procedure is successfully executed on receipt of an RRC active set updatecomplete message at the RNC4. Clear resources in the UTRAN via NBAP procedure (case of removal or replacement)5. Monitored Set update upon neighbor List Selection Algorithm evaluation viaan RRC measurement control message.Handover scenariosSoft/softer handovers can be executed as Intra-RNC as well as Inter-RNC. In case ofInter-RNC soft/softer handover, the RNCs involved are defined as Serving RNC (SRNC)and one or several Drift RNCs (DRNC).

Soft handover event 1AIn case of soft handover with event 1A triggered, other procedures via ALCAP and DCHFraming Protocols are executed on the Iub interface in between Radio Link Set-up (step2) and Active Set Update (step 3) procedures.

Softer handoverIn case of softer handover, the NBAP Radio Link Addition is executed within the sameNode B instead of NBAP Radio Link Setup.

Inter-RNC soft handoverIn Case of Inter RNC soft handover event 1A is triggered in one Node B belonging tothe DRNC then the SRNC initiates the setup of the resources at the DRNC via theRNSAP Radio Link Setup procedure. Afterwards the DRNC allocates the requiredresources at the relevant Node B via the NBAP Radio Link Setup procedure. Thisexample is valid when no soft handover context exists at the Node B, otherwise RNSAPand NBAP Radio Link Addition procedures are executed instead.

Possible failing reasons for SoftHandover Failure

Poor RF ConditionsIncorrect translations settingsNo NodeB resources availableNo transport resources availableNo UE answerUE RejectNodeB/RNC OutagesIub, Iur link OutagesCS Inter-RAT handoverIRAT handover are used to maintain the UMTS voice call in case the 3G RF coverage and/or quality is not sufficient. Furthermore they can be used for traffic distribution. IRAT handovers are always hard handovers and can be either mobile assistant or database assistant.

A handover to another network system or inter Radio Access Technology (inter RAT)handover is always a hard handover with MSC involvement.The UTRAN initiates the Relocation Preparation Procedure at the Iu interface towardsthe MSC of the GSM network. The UE must have established at least a CircuitSwitched (CS) connection to the UMTS network.

KPI Formula Counter

CSV IRAT Failure Rate

1-[Number of successful outgoing inter-RAT handovers (CS)/Number of attempted outgoing inter-RAT handovers (CS) x 100%

[Number of Successful CS Outgoing Inter-RAT Handovers for Cell]/[Number of CS Outgoing Inter-RAT Handover Attempts]*{100}

CS Voice UMTS to GSM handover procedure

In general the UMTS-to-GSM handover procedure can be separated in the followingsteps:1. Handover relocation preparation within UMTS RAN/CN and GSM RAN/CN2. Handover execution involving also the UE3. Release of UMTS resources

UMTS to GSM handover failures

Components that constitute failures of UMTS to GSM handover may be classified asfollows:1. Relocation preparation procedure failures

Relocation preparation failures occur during the RANAP relocation preparationprocedure, for example GSM handover resource allocation fails or the core networkrejects the UMTS to GSM handover request.2. Handover procedure failures.

Upon successful completion of relocation preparation procedure, the SRNC sends thehandover from UTRAN command including the GSM handover command to the UE. Ifthe UE fails to complete the requested handover then the SRNC receives a handover fromUTRAN command failure message from the UE.

System Availability System Availability is defined as the percentage of time the Network can handle one hundred per-cent (100%) of the traffic demand within the limits it is designed for as measured at Cell Level.

The purpose of this metric is to calculate the total amount of time (in percentage) out of the total operating time the RNC and Node-B are available to carry commercial traffic. Minimum granularity for KPI purposes is total loss of traffic at Cell level.

The loss of traffic at Cell Level can be due to one or more reasons:

1.        Equipment failures

2.        Software failures

3.        Other Failures (accidental, misuse, reset etc.)

4. Planned events authorized by Seller (Software upgrade, Equipment upgrade, Parameter change etc)

HSDPA Unavailability duration - VS.Hsdpa.UnavailTime

HSUPA Unavailability duration - VS.Cell.HSUPA.UnavailTime

Coverage Soft/Softer Handover Overhead

It tells the consumption of extra network resources due to soft handover in one RNCIt is nothing but a simple ratio of No. of Radio Links used over the No. of UEs in anRNC

Soft/Softer Handover Overhead KPI provides an indication of how many Cells or Sectors were in the active set during the call on an average basis.

Uplink Interference Ratio

RTWP reflects the total noise level within the UMTS frequency band of one single cell.RTWP (Received Total Wideband Power) analysis is used to evaluate the uplink interference andloading status.If actual loading of the network is empty, then the RTWP is the thermal noise plus the noise figureof the NodeB. With the access of more users in the network, RTWP increases accordingly.

Cell is considered as interefered if the VS.MeanRTWP value is greater than -96

Integrity Indicates the service capabilities for PS/HSDPA throughput on busy hour in each cell and for evaluating the UL BLER values for each cell.

Main KPIs: Average UL Throughput for R99 services. Average DL Throughput for R99 services. HSDPA throughput. HSUPA throughput

Traffic

Used to evaluate the circulated traffic such as CS Erlangs, PS Traffic, Mean UE number for various kind of services.

Key KPIs: No. of CS users, No. of PS R99 users, No. of HSDPA users, No. of HSUPA users, HSDPA traffic volume, HSUPA traffic volume.

This KPI provides the equivalent Erlang values/ & Data Traffic for all the services

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