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Assunto ReferênciaOPTIMIZATION GUIDELINES: RETAINABILITY in HUAWEI DEO.OTM.IOP3023

Elaborador Revisor Aprovador Revisão Data Emissão Data Revisão Páginas

QCES Marcio Pereira Laurindo Santos Draft01 07/May/2010 07/May/2010 1/37

DEO - Otimização de Rede de Acesso

INSTRUÇÃO OPERACIONAL para MANUAL

Optimization Guidelines:Retainability in Huawei

CONTENTS

1

INTRODUCTI ON ............................................................................................................................... 3

2 RETAI NABI L ITY ............................................................................................................................... 4

2.1 6

Cell Update ................................................................................................................................................. 4

2.2 6

CS drop versus PS drop ............................................................................................................................ 5

3 2RETAI NABI L ITY KPI s (Key Performance I ndicators) .................................................................... 7

3.1 8

High Level KPIs......................................................................................................................................... 7

3.1.1 14BRetainability Rate - RR (%) ........... .......... ........... .......... ........... .......... ........... .......... ........... .......... .......... ........... 7

3.1.2

15BDropped Call Rate - DCR (%)........ .......... ........... .......... ........... .......... ........... .......... ........... .......... .......... ........... 8

3.1.2.1 32BUCS DCR (%) ....................................................................................................................................... 8

3.1.2.2 32BUSpeech DCR (%) ................................................................................................................................. 8

3.1.2.3

33BU

Video DCR (%) ................................................................................................................................... 9

3.1.2.4 34BUStreaming DCR (%) ............................................................................................................................ 9

3.1.2.5 34BUPS DCR (%) ........................................................................................................................................ 9

3.1.2.6 39BUFurther considerations on PS/HS DCR (%) ......... ........... .......... ........... .......... ........... .......... ........... ..... 9

3.1.2.7 36BUHSDPA DCR (%) ............................................................................................................................. 10

3.1.2.8 37BUHSUPA DCR (%) ............................................................................................................................. 10

3.1.3 16BMinutes per Drop ............................................................................................................................................ 11

3.1.3.1 40BUVoice Minutes per drop ..................................................................................................................... 11

3.1.3.2 41BUVideo Minutes per drop .................................................................................................................... 11

3.1.3.3 42BUHS Minutes per drop ......................................................................................................................... 11

3.1.4

17BDrops per Erlang (or Drops per Hour) ................ .......... ........... .......... ........... .......... ........... .......... .......... ......... 12

3.1.4.1

43BUVoice drops per hour ......................................................................................................................... 12

3.1.4.2 44BUVideo drops per hour......................................................................................................................... 12

3.1.4.3

45BU

HS drops per hour ............................................................................................................................. 12

3.1.5 18BOverall Service Retainability - OSRET (%)........ .......... ........... .......... ........... .......... ........... .......... ........... ........ 12

3.2 9Medium Level KPIs: Voice Drop Reasons ............................................................................................ 13 3.2.1 19BUL SYNCHRONIZATION Speech DCR (%) ................................................................................................ 14

3.2.2 20BSOFT HANDOVER Speech DCR (%) .......... .......... ........... .......... .......... ........... .......... ........... .......... ........... ... 14

3.2.3 21BCONGESTION Speech DCR (%) ................................................................................................................... 15

3.2.4 22BCS IRAT HO Failure Rate (%) ....................................................................................................................... 15

3.2.5 22BCS IRAT HO Preparation Failures Rate (%) .......... ........... .......... ........... .......... ........... .......... .......... ........... ..... 16

3.2.6 23B22CS IRAT HO Execution Failures Rate (%) ........... .......... ........... .......... .......... ........... .......... ........... .......... ....... 18

3.2.7

IRAT HO DCR (%) ........................................................................................................................................ 18


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1

0BINTRODUCTION

This series of Optimization Guidelines covers all the main topics regardingPerformance Monitoring & AnalysisConfiguration settingsTroubleshooting

Refer to the internal Claro document “Optimization Process” (DEO.OTM.IOP3000), for a summary of 3G WCDMA Radio Access Network Optimization Basics.

This specific document focuses on RETAINABILITY and its specifics within HUAWEI infrastructure (RAN10).

Target users for this document are all personnel requiring a detailed description of this process (RetainabilityOptimization), as well as configuration managers who require details to control the functions and optimize parameter

settings. It is assumed that users of this document have a working knowledge of 3G telecommunications and arefamiliar with WCDMA.

Document Revision Control

Revision Date Author ChangesDraft01 07-May-2010 QCES/Huawei First Draft of the document


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functionality disabled. Nevertheless, this worst behavior in the KPI usually does not match the user perception (that is

typically good) thanks to those additional implicit re-establishment mechanisms (Paging/Service Request).

2.2 6BCS drop versus PS drop

One important difference between the Circuit Switched (CS) and Packet Switched (PS) domains is that in the CSdomain, the end-to-end services (voice, video-telephony, CS data) can be maintained only if all lower layer links aremaintained. For example, if the Radio Bearer is broken during a voice call, the network may allow only limited time(T314) to perform a Cell Update before terminating the end-user application.

For PS data, to accommodate the bursty nature of the traffic, links from different layers can be independent. Forexample, the Packet Data Protocol (PDP) context is preserved, while the Radio and Radio Access Bearers arereconfigured or disconnected during low activity periods. The behavior of an FTP session is another example; when

Radio Bearers are dropped or experience a high block error rate, the FTP might time out, even if the PDP context isactive.

The interdependence between layers complicates data service optimization; all layers must be considered.

A single PS call (= a single PS RAB) goes dynamically through different “phases” (DCH R99, HSDPA, EUL, Cell_FACH)based on different radio configurations. It may also go to IDLE (with “pdp context preserved”) due to inactivityperiods. It is the system that re-establishes the lower layer connections, with no user intervention.

When the PS call goes to Idle with “pdp context preserved” due to inactivity, the PS RAB is considered normallyreleased, and there will be a new process of call establishment starting with an RRC connection request, and RABestablishment, etc. (but without the UPLINK DIRECT TRANSFER [SM: Activate PDP Context Request] as it waspreserved).

In case there is a RL Failure, the pdp context is also preserved and either Cell Update or implicit re-establishmentmechanisms (Paging/Service Request) will re-establish the lower layer connections with no user intervention. Userdoes not notice the call drop (but typically experiences low throughput or delay). So in terms of “user perception” (or


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Data Application DCR %, or Data Session DCR %, or PDP context DCR %), the retainability is not impacted. These

latest metrics (from an operational point of view) can only be derived from PS CORE (GGSN) counters.

In terms of Abnormal RAB Releases due to RL Failure, typically those vendors with CU enabled (NSN & Huawei, forexample) will not increase the counter (in fact, they will not increase any RAB Release counter – nor normal neitherabnormal-; RAB is not released); those ones with CU disabled will (Huawei, for instance). So, as already anticipated,you can expect a worst KPI PS DCR % performance in these last ones.


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3

2B

RETAINABILITY KPIs (Key Performance Indicators)

Below the main metrics used for Retainability Monitoring of a 3G WCDMA/UMTS Network, and their implementationwith Huawei counters.

Refer to “SMART Documentation” for further details on the actual implementation of these KPIs in the tool, togetherwith the additional considerations regarding:

Treatment of zeros in the denominatorsDifferentiation of PS: Global, R99, HS, EUL KPIs.Considerations regarding SRNS Relocations and Outgoing Hard Handover

3.1 8BHigh Level KPIs

3.1.1 14B

Retainability Rate - RR (%)

Based in statistical counters, it is possible to count every time a RAB is normally released, e.g.:

Call ended by UE or user control(user generates a “disconnect” towards the CN:

“Normal Release” or “UE Generated Signaling Connection Release” ) Call ended because of any problem or action on the other part

(the monitored user receives a “disconnect” from the CN: “Normal Release” )

Call ended with cause “Network Optimisation” or “Resource Optimisation Relocation”

Connection ends because of “User Inactivity” (PS calls only) Connection ends because the call is successfully transferred to another system (IRAT HO):

“Successful Relocation”.

and abnormally released (= DROP):

Call ended by the network for any other reason than NORMAL.

A global Retainability Rate (%) can be calculated as follows:

However, it is common practice to use the Non Retainability Rate (NRR) instead, a.k.a. Dropped Call Rate (%),that we will use throughout this document:

As already stated, target is to keep Retainability Rate, RR (%) as close as possible to 100%, while target for NRR (%) is tokeep the DCR (%) as close as possible to 0%.

Releases)RAB Abnormalof NoReleasesRABNormalof (No

ReleasesRABNormalof No *100

Releases)RAB Abnormalof NoReleasesRABNormalof (No

ReleasesRAB Abnormalof No *100


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3.1.2

15B

Dropped Call Rate - DCR (%)

It is the most common KPI for Retainability.

The value is dependent on the call duration: the shorter is the average call duration, the lower shall be the drop callrate and vice versa. Any changes in the network that modify the call duration shall impact on the Drop Call Rate (e.g.IRAT Handover thresholds for speech or inactivity timers for PS calls).

Counters available in Huawei for the Normal and Abnormal RAB Releases are:

Number of Normal RAB Releases Number of Abnormal RAB Releases VS.RAB.Loss.CS.Norm VS.RAB.Loss.CS.RF + VS.RAB.Loss.CS.Abnorm + VS.CN.RAB.Loss.CS

VS.RAB.Loss.CS.Norm.AMR VS.RAB.Loss.CS.AMR

VS.Norm.Rel.CS.Conv.RB.64 VS.RAB.Loss.CS.Conv64K

VS.Norm.Rel.CS.Str VS.Abnorm.Rel.CS.Str VS.RAB.Loss.PS.Norm VS.RAB.Loss.PS.RF + VS.RAB.Loss.PS.Abnorm + VS.CN.RAB.Loss.PS

VS.Norm.Rel.PS.Conv VS.Abnorm.Rel.PS.Conv

VS.Norm.Rel.PS.Str VS.Abnorm.Rel.PS.Str

VS.HSDPA.RAB.Loss.Norm VS.HSDPA.RAB.Loss.RF + VS.HSDPA.RAB.Loss.Abnorm.NonRF

VS.HSDPA.RAB.Loss.Inactivity

VS.HSUPA.RAB.Loss.Norm VS.HSUPA.RAB.Loss.Abnorm

As all previous counters are available at cell level, all the DCR KPIs (%) introduced in the following sections will also beavailable at cell level. As expected for High Level KPIs, they can be aggregated at nation, market/vendor, region, city,RNC, cluster,… levels.

3.1.2.1 32BU

CS DCR (%)

The usage of VS.CN.RAB.Loss.CS in the formula is to be confirmed by Huawei. [Pending Huawei feedback]

Another approach, considering just Voice and Video, could be:

High value (e.g. >2%) indicates retainability issues for CS connections.

3.1.2.2 32BUSpeech DCR (%)

High value (e.g. >2%) indicates retainability issues for Speech connections.

s.CS.Norm) VS.RAB.Los.Loss.CS VS.CN.RAB+rmss.CS.Abno VS.RAB.Lo+ss.CS.RF(VS.RAB.Lo

Loss.CS) VS.CN.RAB.s.CS.RF VS.RAB.Los+rmss.CS.Abno(VS.RAB.Lo *100

RB.64)l.CS.Conv. VS.Norm.Re+64K ss.CS.Conv VS.RAB.Lo+.AMR ss.CS.Norm VS.RAB.Lo+ss.CS.AMR (VS.RAB.Lo

64K)ss.CS.Conv VS.RAB.Lo+ss.CS.AMR (VS.RAB.Lo *100

.AMR)ss.CS.Norm VS.RAB.Lo+ss.CS.AMR (VS.RAB.Lo

ss.CS.AMR)(VS.RAB.Lo *100


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If counters for all those transitions are not available, then the KPI could be not that meaningful.

3.1.2.7 36BU

HSDPA DCR (%)

Typically calculated as:

This metric above does not consider the channel switching from HSDPA to any other PS RAB state. So it is highlyrecommended to use the following formula instead:

High value (e.g. >2%) indicates retainability issues for HSDPA connections.The usage of VS.HSDPA.RAB.Loss.Inactivity in the formula is to be confirmed by Huawei. [Pending Huawei feedback]

3.1.2.8 37BU

HSUPA DCR (%)

Typically calculated as:

This metric above does not consider the channel switching from HSUPA to any other PS RAB state. So it is highlyrecommended to use the following formula instead:

High value (e.g. >2%) indicates retainability issues for HSUPA connections.

nactivity)RAB.Loss.I VS.HSDPA.+rm AB.Loss.No VS.HSDPA.R +FRAB.Loss.R VS.HSDPA.+Fbnorm.NonR RAB.Loss.A (VS.HSDPA.

) AB.Loss.RF VS.HSDPA.R +Fbnorm.NonR RAB.Loss.A (VS.HSDPA. *100

rm) AB.Loss.No VS.HSUPA.R +bnormRAB.Loss.A (VS.HSUPA.

norm AB.Loss.Ab VS.HSUPA.R *100

) _other_RAB _HS_to_anyching_fromannel_SwitSuccess_ChReleaseHS_Normal_ al_Release(HS_A bnorm

l_ReleaseHS_Abnorma *100

FACH.SuccChR.EDCHto VS.HSUPA.+CH.Succeq.EDCHtoDhR.InterFr VS.HSUPA.C

+DCH.Succreq.EDCHtoChR.IntraF VS.HSUPA.+CH.Succll.EDCHtoDhR.IntraCe VS.HSUPA.C

rm AB.Loss.No VS.HSUPA.R +norm AB.Loss.Ab VS.HSUPA.R

norm AB.Loss.Ab VS.HSUPA.R *100

eqRNCInterFrccOutIntraHHO.H2D.Su VS.HSDPA.+qNCIntraFrecOutIntraR HO.H2D.Suc VS.HSDPA.H

+ toFACHChR.HSDSCH VS.HSDPA.+oDCHhR.HSDSCHt VS.HSDPA.Cactivity AB.Loss.In VS.HSDPA.R

+rm AB.Loss.No VS.HSDPA.R +FRAB.Loss.R VS.HSDPA.+norm.NonRF AB.Loss.Ab VS.HSDPA.R

) AB.Loss.RF VS.HSDPA.R +Fbnorm.NonR RAB.Loss.A (VS.HSDPA.*100


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3.1.3

16B

Minutes per Drop

This KPI (“Traffic Drop Ratio”, using Huawei terminology) gives the average time length (in minutes) between 2consecutive drops. In other words: It is the average number of minutes of a continuous service before a RAB isabnormally dropped.

i.e., Erlangs translated into minutes divided by the number of drops.

As all High Level KPIs, it can be produced at nation, market/vendor, region, city, RNC, cluster,… levels , but also on cellbasis (as both elemnets involved in the formula, erlangs and drops, can be extracted from the UtranCell MO counters).

Please also note that:

It is not dependent on the call duration. It can be used to evaluate the retainability of each single phase of a call (HSDPA, DCH, and FACH). Target values are difficult to define. It is better used to analyze performance trends. The values are instable in case of good performances (the indicator points to infinite for a perfect network). A certain level of traffic is needed to have a stable indicator.

Formulas to calculate the Minutes per drop for different call types are shown next. In all the cases:

ROP (Report Output Period) = Measurement time in minutes (examples: 15’, 30’, hour = 60’, day = 1440’)

3.1.3.1 40BU

Voice Minutes per drop

3.1.3.2

41BU Video Minutes per drop

3.1.3.3 42BU

HS Minutes per drop

sRbReleaseHpmNoSy stemishhRabEstablestPsHsAdcpmSamplesB

EstablishsHsAdchRabpmSumBestP*ROP

SpeechRabReleasepmNoSystemish0RabEstablestAmr1220pmSamplesB

Establishmr12200RabpmSumBestA *ROP

Cs64RabReleasepmNoSy stemEstablishestCs64RabpmSamplesB

blishs64RabEstapmSumBestC*ROP

ReleasesRA B Abnormalof Number

60*RABaof ErlangsTraffic

SpeechRabReleasepmNoSy stem60*

ish0RabEstablestAmr1220pmSamplesB

Establishmr12200RabpmSumBestA *

60

ROP

Releases Voice Abnormalof Number

60*ErlangsTraffic V oice


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3.1.4 17B

Drops per Erlang (or Drops per Hour)

It is the average number of dropped calls per 1 hour of connection.

i.e., just the inverse of the previous KPI (Minutes per drop).

It is not often used because it is not easily mapped on the user perception. It is not dependent on the call duration. It is more stable than Minutes per Drop in case of good values.

3.1.4.1 43BU

Voice drops per hour

3.1.4.2 44BU

Video drops per hour

3.1.4.3 45BU

HS drops per hour

3.1.5 18B

Overall Service Retainability - OSRET (%)

Since there are many different services defined in UMTS and each one can have a different retainability at any time,an overall service reatainability can be defined to obtain an overall measure of network retainability averaged over allservices. This metric can be used in case one single measurement is to be applied to sort out the worst overall cells interms of drops.

The OSRET criterion will be based on a weighted averaging of the retainability for the CS and PS services supported bythe cell. The weighting factors will be chosen to be the demand for the service given by the number of RAB Establishattempts for that service.

60*RABaof ErlangsTraffic

ReleasesRA B Abnormalof Number

ishhRabEstablestPsHsAdcpmSamplesB

ROP*EstablishsHsAdchRabpmSumBestPsRbReleaseHpmNoSy stem


RO P*Establishmr12200RabpmSumBestA SpeechRabReleasepmNoSystem

EstablishestCs64RabpmSamplesB

ROP*blishs64RabEstapmSumBestCCs64RabReleasepmNoSy stem

60*


Establishmr12200RabpmSumBestA *

60

ROPSpeechRabReleasepmNoSystem

60*ErlangsTraffic V oice

Releases Voice Abnormalof Number


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3.2.1

CS RF DCR (%)(Percentage of CS calls dropped due to RF Failure: "Radio Connection With UE Lost", "Failure in the Radio InterfaceProcedure")

High value (e.g. >2%) indicates retainability problems related to the RF environment.

3.2.1.1 47BU

CS RF UL Synchronization DCR (%)

o

VS.RAB.Loss.CS.RF.ULSyncIn CELL_DCH state, the Radio Connection Supervision functionality is provided by means of two different algorithms:the

3.2.2 20B

CS Non-RF DCR (%)(Percentage of CS calls dropped due to RF Failure: "Radio Connection With UE Lost", "Failure in the Radio Interface

Procedure")

(Percentage of CS calls dropped due to RF Failure: "Radio Connection With UE Lost", "Failure in the Radio InterfaceProcedure")




ss.CS.RF)(VS.RAB.Lo *100






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VS.SHO.Drop.RNC: the number of call drops caused by soft handover in the RNC

During soft handover, when the RNC sends an ACTIVE SET UPDATE message to the UE, it starts the timer to wait for theresponse from the UE. If the RNC does not receive the response until the timer expires, it releases this RRC connection,which results in call drops. At this time, the RNC measures this item.

High value (e.g. >2%) indicates retainability problems related to the Active Set dynamic. A special and importantsubset of these issues is the one caused by missing neighbours:

3.2.3 21B

CONGESTION Speech DCR (%)(Percentage of Voice calls dropped due to cell congestion)

High value (e.g. >2%) indicates retainability problems related to cell congestion.

CD_Cong = VS.RAB.Loss.CS.Congstion.CELL + VS.RAB.Loss.PS.Congstion.CELL

3.2.4 22B

CS IRAT HO Failure Rate (%)

=100*(A-B)/B

Speech)RabReleasepmNoSystemeSpeechlRabReleas(pmNoNorma

SpeechCongpmNoOfTerm *100

tion.CELLs.CS.CongsVS.RAB.LosAMR s.CS.Norm.VS.RAB.Los

tion.CELLs.CS.CongsVS.RAB.Los

( *100


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This KPI covers all IRAT Phases, including the Preparation one.Hence, it provides an overall perception of the IRAT Performance

3.2.5 2

CS IRAT HO Preparation Failures Rate (%)

2CS IRAT HO Preparation Failures =A-C

HOCSAttPrep.IR VS.SRELOC.

RNC)SuccCSOut.VS.IRATHO.-RHOCS.AttPrep.I(VS.SRELOC *100


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In order to isolate the issues, Global IRAT performance shown in the previous section should be analyzed per phases.

The first phase is: PREPARATION PHASE, i.e., how many RELOCATION REQUIRED messages sent by the RNC to CNcould not be converted into HO FROM UTRAN COMMAND sent to the UE.

In order to get a more accurate perception of the importance/impact of Preparation Failures in global IRATperformance, we show now the ratio:100 * Preparation Failures / Total IRAT Failures (including IRAT drops)

100*(A-C)/(A-B)

what give us an idea of the contribution of this type of Failures to the total number of IRAT HO Failures.

RNC)SuccCSOut.VS.IRATHO.-RHOCS.AttPrep.I(VS.SRELOCRHOCS)SuccPrep.IVS.SRELOC.-RHOCS.AttPrep.I(VS.SRELOC *100


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3.2.6 23B

CS IRAT HO Execution Failures Rate (%)

=100*(D-B)/D

3.2.7

IRAT HO DCR (%)

Focus of this paragraph is on the “Execution Failures” (i.e., execution + confirmation failures).

When a UE fails in getting the 2G system, it tries to return to 3G. If it succeeds reacquiring 3G, itwill then send a HO FROM UTRAN FAILURE to the network. This is an IRAT HO FAILURE, but

not a drop.

Sometimes though, the UE does not get the 2G system, nor reacquires the 3G one. It is thenconsidered LOST. This is what we call an IRAT drop.

NCAttCSOut.R VS.IRATHO.

RNC)SuccCSOut.VS.IRATHO.-RNC.AttCSOut.(VS.IRATHO *100


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3.2.8

23BOTHERS Speech DCR (%) ???

(All Voice drop reasons not considered in the previous categories are collected in this subset. We typically find here dropsrelated to faults in the Transport Network, or RNC, or CORE, etc.)

High value (e.g. >2%) indicates reatainability problems related to those “other” causes.

VS.RRC.AttConRel.Cng.RNC Number of RRC CONNECTION RELEASE messages from the RNC to UEs because ofcongestion

VS.RRC.AttConRel.Preempt.RNC Number of RRC CONNECTION RELEASE messages from the RNC to UEs because ofpreemptive release

VS.RRC.AttConRel.UsrIact.RNC: Number of RRC CONNECTION RELEASE messages from the RNC to UEs because ofuser inactivity

VS.RRC.AttConRel.ReEstRj.RNC: Number of RRC CONNECTION RELEASE messages from the RNC to UEs because ofreestablishment rejection

VS.RRC.AttConRel.SigREst.RNC: Number of RRC CONNECTION RELEASE messages from the RNC to UEs because ofdirected signaling connection re-establishment

VS.RRC.AttConRel.Unspec.RNC: Number of RRC CONNECTION RELEASE messages from the RNC to UEs because ofunspecified reason

Inter-Frequency Handover DCR (%)

Speech)RabReleasepmNoSystemeSpeechlRabReleas(pmNoNorma

tion))echUeRejectIratHoSpepmNoFailOu

ChFailldChNotPhyechReturnOtIratHoSpepmNoFailOuailldChPhyChFechReturnOtIratHoSpepmNoFailOu

SpeechsOutIratHopmNoSuccesechtIratHoSpe(pmNoAttOu

SpeechC ongpmNoO fTerm

SpeechSoHopmNoSysRel

ynchlSpeechUlS(pmNoSysRe

SpeechRabReleasepmNoSystem

*100

OuterFreq.AttVS.HHO.Int

cOut)erFreq.SucVS.HHO.Int-tOutterFreq.At(VS.HHO.In *100


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Radio Connection Supervision (RCS) Evaluation

The Radio Connection Supervision Evaluation algorithm keeps track of the synchronization status of the wholeradio connection by assigning a tag to every RLS.

Radio Link Set (RLS) SupervisionThe RLS Supervision function supervises the synchronization status of the RLS provided by the RBS to the radioconnection, and reports any changes to the SRNC. When nOutSyncInd number of consecutive frames are out-of-sync a timer rlFailureT is started and at expiry the RLS is considered out-of-sync and Radio Link Failure isreported to the SRNC. When the RLS is out-of-sync and nInSyncInd number of frames are in-sync, the RLS isconsidered in-sync and Radio Link Restore is reported to the SRNC.

The connection is considered lost by the RCS when the last RLS, for the connection, has been out-of-sync for a timegiven by the parameter dchRcLostT. For a connection that includes HSDPA, the PS part of the connection isconsidered lost by the RCS when the RLS that contains the Serving HS-DSCH cell, has been out-of-sync for a timegiven by the parameter hsDschRcLostT. This means that when the hsDschRcLostT timer expires, an Iu Release

will be requested to the PS CN and when the dchRcLostT timer expires, an Iu Release will be requested to allinvolved CNs.

4.1.1.2 47BU

Radio Connection Supervision for UE in Cell_FACH

In CELL_FACH state, supervision is provided by monitoring periodic Cell Update messages sent by the UE. In URA_PCHstate periodic URA Update messages are sent instead.

The timer cchWaitCuT is started in the RNC whenever the UE enters theCELL_FACH or URA_PCH state. The timer is stopped if the UE entersCELL_DCH state and is reset to zero (but not stopped) upon receipt of a CellUpdate or URA Update from the UE. Upon expiry of the timer, the overallrelease of the connection shall be triggered (abnormal release) by sending

Iu release request to the CN.

The time set on cchWaitCuT is longer than the one set on timer t305. Thetimer t305 indicates how often the UE should send a Cell Update messagewhen in state CELL_FACH and how often to send the URA Update messagewhen in state URA_PCH.

U

Radio Connection Supervision ParametersU

:Final recommended setting under discussion. Trial ongoing to be completed.

Guard Time to detect rl failure in RBS: rlFailureT=10 (1s)Number of consecutive bad frames: nOutSyncInd=20 (20 frames)Number of consecutive good frames: nInSyncInd=1 (1 frame)

Timer in RNC for DCH: dchRcLostT=100 (10s)Timer in RNC for HSDPA: hsDschRcLost=100 (10s)Timer in RNC for FACH: cchWaitCuT=9 (45 min)

URadio Connection Supervision CountersU:

Following 2 counters are available only at RNC level. They cannot be used for cell level troubleshooting:pmNoReleaseDchRcLostT: Number of overall releases triggered by dchRcLostT expirypmNoReleaseCchWaitCuT: Number of overall releases triggered by cchWaitCuT expiryGood counter for speech abnormal release identification at cell level:


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4.1.4 27B

Critical radio procedure failures due to coverage

The most common radio procedure failed by coverage is the Active Set Update (SHO execution)

4.1.5 28B

Radio Environment Evaluation

Evaluating radio environment characteristics by counters:

Radio Environment straight indicators Radio Environment Statistics (RES) and OSS W-MRR

4.1.5.1

48BU

Primary Straight IndicatorsCPICH RSCP (the signal strength of the pilot channel) Samples at low level (


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pmResX is a PDF counter where the first item pmResX[0] is a number that describe the type of measurement

according to this schema:

Radio Environment Statistics (RES) settings (by OSS-W-MRR)

Define 1 –6 measurements, each consisting of a Service + Measurement Quantity Schedule the measurements Define a recording area that is Cell Sets or Cells Define sampling periods (how many seconds between two MRs: from 2 to 64) Define UE fraction (how many UEs are ordered to make measurements: FULL, 1/2, 1/3, 1/4 and 1/5) Manage recording activities: Start, stop and terminate recordings Generate reports

4.1.5.4 51BUGPEH for Radio Coverage Analysis ??? what Huawei has

Some internal and external GPEH events carry some radio measurements that can be collected and correlated withother events or used to build distributions:


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4.1.5.5 52BU

RRC measurement Reports

In case RES is activated it will be possible to capture the periodical MRs containing the scheduled measurements. The

information can be correlated to the other GPEH events to provide a very advanced analysis.

RRC_RRC_CONNECTION_REQUEST - The message has to be fully decoded, then all the included measurement will beavailable, in particular the Ec/No Value of the cell where the connection is requested. Sampling will be uniform all overthe cell. It could be helpful to correlate the Ec/No values with the RRC Establishment Cause to evaluate coverage fordifferent user activities

RRC_MEASUREMENT_REPORT - By counting the measurement reports for events 2d it is possible to count how manytimes the connection was bad for RSCP or for Ec/No. To distinguish 2d-RSCP from 2d-Ec/No use the MeasurementIdentity information element retrieved from the fully decoded message (13 and 12 respectively)

4.2 11BMobility Issues

This section covers Intrafrequency HO, Interfrequency HO (IFHO) and IRAT HO, in those aspects with impact in

Retainability:

Soft/Softer Handover failuresIRAT Handover failuresIF Handover Failures

Refer to Claro internal doc. “Optimization Guidelines – Mobility in Ericsson” (DEO.OTM.IOP) for further detailsregarding Mobility in general.


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4.2.1 29BS

Soft/Softer Handover Failures

When UE in connected mode moves within a WCDMA carrier it should always stay connected with the best cells,otherwise:

The downlink connection quality will deeply decrease because of the interference of the strongest (non-used)cell. (Each cell acts as interferer for the others)

The UE shall generate high UL interference in the closest (non-used) cell.

RNC implements special measures to avoid UL problems in the target cell and it could decide to release a dangerousconnection.

If the UE reports to the RNC the measurement from an unknown (not in the neighbour list) cell that isstronger than the best cell in the current active set + releaseConnOffset parameter, then the call will bereleased.

If the UE reports a measurement from a neighbour cell, that is stronger than the current active set +releaseConnOffset parameter, cannot be added to the active set for any reason, then the call will also bereleased.

U

Huawei counters:


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SHO.FailRLAddUESide.NoReply : The measurement is triggered at point A as shown in Figure 1, when the RNC sends an ACTIVE SET UPDATE message to the UE and starts the timer to wait for the response

from the UE. If the RNC does not receive the response from the UE upon expiry of thetimer, the RNC measures the item in the cell where there is a newly added RL.

SHO.AttRLAddUESide : The measurement is triggered at point B as shown in Figure 1, when the RNC sendsan ACTIVE SET UPDATE message to the UE. If there are newly added RLs, the RNC

measures the item in the cell where the RL is added

SHO.SuccRLAddUESide :The measurement is triggered at point C as shown in Figure 1, when the RNC

receives an ACTIVE SET UPDATE message from the UE. If there are newly addedRLs, the RNC measures the item in the cell where an RL is successfully added.

SHO.AttRLDelUESide :The measurement is triggered at point B as shown in Figure 1, when the RNC sendsan ACTIVE SET UPDATE message to the UE and the RLs are deleted from the cells.In this case, the RNC measures the item in the cell where the RLs are deleted

SHO.SuccRLDelUESide :The measurement is triggered at point C as shown in Figure 1, when the RNCreceives an ACTIVE SET UPDATE COMPLETE message from the UE and the RLs aredeleted from the cells. In this case, the RNC measures the item in the cell where the

RL is successfully deleted.

VS.SoHo.ASU.AttRNC : The measurement is triggered at point B, as shown in Figure 1. During softerhandover, when the RNC sends an ACTIVE SET UPDATE message to a UE, the RNC

measures this item.

VS.SoHo.Succ :The measurement is triggered at point C, as shown in Figure 1. When the RNC receivesan ACTIVE SET UPDATE COMPLETE message from the UE, which indicates that thesofter handover is successful, the RNC measures this item

Based on this counter and the number of successful HOs executions , we can define following Mobility metrics:

4.2.1.1 46BU

SOFTER HANDOVER Speech Success Ratio (%)

[ () ]

VS.SoHO.ASU.SuccRLAdd : Number of Successful RL Additions in Softer Handover (Cell)

VS.SoHO.ASU.SuccRlDel : Number of Successful RL Deletions in Softer Handover (Cell)

VS.SoHO.ASU.AttRLAdd : Number of RL Additions in Softer Handover (Cell)

VS.SoHO.ASU.AttRlDel : Number of Attempts to Delete RLs in Softer Handover (Cell)


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4.2.1.2 4

SOFT HANDOVER Speech Success Ratio (%)

[()( ) ]

SHO.SuccRLAddUESide : Number of Successful RL Additions in Soft Handover (Cell)SHO.SuccRLDelUESide : Number of Successful RL Deletions in Soft Handover (Cell)

SHO.AttRLAddUESide : Number of RL Additions in Soft Handover (Cell)

SHO.AttRLDelUESide : Number of Attempts to Delete RLs in Soft Handover (Cell)

VS.SoHO.ASU.AttRLAdd : Number of RL Additions in Softer Handover (Cell)

VS.SoHO.ASU.AttRlDel : Number of Attempts to Delete RLs in Softer Handover (Cell)

Poor SHO failure rate could explain dropped calls in the neighbours.

4.2.2 30B

Missing Neighbour Relations

The most common cause for a missed handover is the missing neighbour relation

4.2.3 31B

IRAT Handover Failures


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IRAT HO should reduce the dropped calls bymoving the connections towards GSM beforethey drop.

The real user perception of retainability howeverdepends on both drop call rate on WCDMA andon GSM side. Wrong IRAT HO settings or wrongdefinition of IRAT neighbours can delay or blockthe execution of the handover with a negativeeffect on the retainability. Moreover somefailures during the IRAT HO execution canproduce dropped calls.

It is important to understand that CS IRAT HO is basically a 3-steps process:

Step 1: Preparation PhasePreparing the 2G network for the incoming HO.

Step 2: Execution PhaseOrdering the UE to handover to the 2G network. Step 3: Confirmation PhaseReceiving confirmation from the 2G network thatIRAT HO was successful.

Different metrics can be defined to get a complete understanding of the IRAT Performance:

In Section 3.2.4 above we already introduced the IRAT Speech DCR (%), providing the percentage of Voice Dropsthat are IRAT drops. It gives an initial idea of the importance of the IRAT problem, in case it is present.

Be aware that IRAT HO Failure does not mean “dropped call”: If the UE fails in getting the 2G system, it will try to getback to 3G. Only those calls that fail both in getting gsm and then also to reacquire umts are considered “lost” ( IRATdrops). But being already in the border of the 3G coverage, all the delays, attempts and reattempts to move to 2G canonly increase the probability to finally drop. Same impact can be expected from delays due to Preparation Failures.

Following KPIs are calculated also for Voice Calls, but can be calculated as well for other RABs (Multi-RAB, SRBStandalone, CS streaming).

Speech Relocation Preparation Failure Rate (%) Percentage of IRAT HO Failures due to Preparation Phase issues.

High values point out to problems in the Core Network or in the target GSM Network (resource allocation failure in thetarget GSM cell, including congestion)

Percentage of Speech IRAT Handover lost (IRAT drops) over the total number of attempts (%):

ch)IratHoSpeepmNoAttOutlureeechGsmFaiutIratHoSp(pmNoFailO

ureechGsmFailtIratHoSpepmNoFailOu *100

1

2

3

tionechUeRe ectIratHoS emNoFailOu

ChFailldChNotPhyechReturnOtIratHoSpepmNoFailOuailldChPhyChFechReturnOtIratHoSpepmNoFailOu

SpeechsOutIratHopmNoSucces

chIratHoSpeepmNoAttOut


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And again, also for IRAT CC, some PS connections succeed in getting the 2G system (Successful Cell Change), some

others don’t (Cell Change Failures, in general). Amongst these IRAT CC Failures, we have 2 cases now: thoseconnections that managed to get back to 3G, and those ones that don’t (these “lost” connections are IRAT PS drops).

Percentage of Outgoing IRAT Cell Change Drops (%):

where pmNoOutIratCcReturnOldCh provides the total number of the PS Inter-RATCC attempts for UE on DCH wherethe UE returns to old channel. It is stepped for Inter-RAT CC from UTRAN to GPRS, UE on DCH. The counter isincreased when the “Cell change order from UTRAN failure” (RRC) message is received from the UE. It doesn’t triggera dropped call, but it can be responsible of dropped calls for poor coverage due to the delay in the IRAT CC execution,so it’s interesting to get an idea of the contribution of these Failures:

Percentage of Outgoing IRAT Cell Change Failures (%) – not including drops-:

4.2.4 17B

IF Handover Failures

Inter-Frequency HOs are also hard handovers. Also here the possibilities are: the UE succeeds in handover to the target carrier (Successful IF HO) the UE fails in getting the target carrier and comes back to the original carrier (IF HO Failure) the UE fails in getting the target carrier and also fails to get back to the original carrier (“lost” call = IF drop)

Percentage of IF HO lost (dropped) (%):

[()( ) ]

VS.HHO.InterFreq.SuccOut : Number of successful outgoing inter-frequency hard handovers initiated by the RNC.

VS.HHO.InterFreq.AttOut : Number of requests for outgoing inter-frequency hard handovers initiated by the RNC.

Where (RAB) can be any of these possibilities:

tCcAttpmNoOutIra

ldCh)tCcReturnOpmNoOutIra-tCcSuccesspmNoOutIra-atCcAtt(pmNoOutIr *100

tCcAttpmNoOutIra

ldChtCcReturnOpmNoOutIra *100

eqHo(RAB)indInterFrpmAttNonBl

(RAB))eqHoRevertindInterFrpmFailNonl-reqHo(RAB)lindInterFpmSuccNonB-reqHo(RAB)lindInterF(pmA ttNonB *100


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CsConversational

CsSpeech12 PSInteractiveGreater64 PSInteractiveLess64 StreamingOther

A correct neighbours definition is critical for both IRAT and IF HO.

For IF HO the neighbours definition could be even more difficult: Isolated or border second layer cells could have a very large and unpredicted coverage extension because

they are not limited by the surrounding

On the other hand the target WCDMA cells will be only available in the area where they are the best, in otherpositions they will be really interfered and cannot be used

Refer to internal Claro docs. “Multicarrier Strategy in Claro” (DEO.OTM.IOP3112) and “PSC Plan and Neighbor List

Strategy in Claro” (DEO.OTM.IOP3110).

4.3 12BCapacity Issues: Congestion Monitoring (from CAPACITY doc)

Following metrics should be considered in the analysis:

Number of downlink congestion eventspmSumOfTimesMeasOlDl

Number of uplink congestion eventspmSumOfTimesMeasOlUl

Number of speech calls released because of congestion (including calls over Iur)pmNoOfTermspeechCong + pmNoOfIurTermSpeechCong

Number of CS64 calls released because of congestion (including calls over Iur)pmNoOfTermCsCong + pmNoOfIurTermCsCong

Number of PS calls switched to FACH or released due to congestion (including Iur calls)pmNoOfSwDownNgCong + pmNoOfIurSwDownNgCong

Percentage of time a cell was congested in DL during a reporting period100 * pmTotalTimeDlCellCong / [measurementTimeinSeconds]

Percentage of time a cell was congested in DL during a reporting period100 * pmTotalTimeUlCellCong / [measurementTimeinSeconds]

4.4 13BOther Faults

There is no counter for Drops due to “Other” reasons: We just simply calculate them as those cases for which counterpmNoSystemRabReleaseSpeech is pegged without any of the drop reason counters being pegged.

Section 3.2.5 describes the OTHERS Speech DCR (%).

For further analysis of this dropped calls contribution, try to correlate with Transport Network, RNC, CORE,… issues.


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TN checkings should include, amongst others, counters for Transmission Errored Seconds (pmEs), TransmissionSeverely Errored Seconds (pmSes), Transmission Unavailable Seconds (pmUas). Also for other MOs: ImaLink, etc.

Refer to Claro internal Doc. DEO.OTM.IOP3061, “Optimization Guidelines: Transport Network in Ericsson” for furtherdetails.


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5

4B

REFERENCES[1] WCDMA (UMTS) Deployment Handbook. Planning and Optimization Aspects . Christophe Chevallier, ChristopherBrunner, Andrea Garavaglia, Kevin P. Murray, Kenneth R. Baker (All of QUALCOMM Incorporated California, USA). Ed.John Wiley & Sons. 2006

[2] Radio Network Planning and Optimisation for UMTS . Jaana Laiho and Achim Wacker [Both of Nokia Networks,Nokia Group, Finland] & Toma´ sˇ Novosad [Nokia Networks, Nokia Group, USA]. Ed. John Wiley & Sons. 2006

[3] WCDMA Radio Access Network Optimization . LZT 123 8297 R1C. Ericsson 2006.

[4] Retainability-Analysis and Monitor Rev5. Guidelines delivered by Ericsson Brazil to Claro in Nov.2009

[5] Introduction to UMTS Optimization . Wray Castle, 2004

[6] HED 5.5. NodeB Documentation (V100R010_06)

[7] RAN6.1 Feature Description

[8] RAN10.0 Network Optimization Parameter Reference-20080329-A-1.0

[9] NodeB WCDMA V100R010C01B051 Performance Counter Reference

[10] Function List and Description of Huawei UMTS RAN10[1].0 V1.7(20080827)


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6 5B ANNEX I: Call Reestablishment (Cell Update procedure)

If a call drops because of a radio link failure, and if network settings allow Call Reestablishment, the UE can reestablishthe call connection through the cell update procedure.

After the drop, a suitable cell is reselected and the UE sends a cell update, as shown in next slide Figure. Thisprocedure requires the radio condition to recover quickly from the radio link failure; otherwise higher layers on theUTRAN will clear the call.

After a suitable cell is found, the UE transitions to CELL FACH. The UE sends a Cell Update message using a randomaccess procedure, the normal procedure for radio link establishment. In this procedure, the network can send a CellUpdate Confirmed message to instruct the UE to return to the CELL DCH state with new RB, transport channel, andphysical channel information (with new assigned dedicated channel information). This is similar to the procedure usedin channel-type switching (from CELL FACH to CELL DCH) during a packet switched call. The UE then responds withone of the following acknowledgment Layer 3 messages: RB Reconfiguration Complete, Transport Channel

Reconfiguration Complete, or Physical Channel Reconfiguration Complete.

If the connection is successfully reestablished, the dropped call could be a system perceived call drop rather than auser-perceived call drop, because the user does not have to manually intervene to reestablish the connection. System-perceived call drops and user-perceived call drops should be counted separately during network analysis. It can takeup to T315 seconds (for PS) or T314 s (for CS) to complete the link reestablishment procedure, during which the UEtransitions to CELL FACH, recovers from the radio link failure, reads all the SIBs, sends the cell update message, andreceives the cell update Complete message with new channel information. During this time, the conversation soundsare muted to the user.

System and User Perceived PS Call Drops can be easily reported from drive test log-files.

User-perceived call drops are a subset of system-perceived call drops. In these cases, the call was not recoveredautomatically; the user had to reactivate it manually.

Use Actix to get the number of call drops.

Display on table: 3G UMTS >> Event Data >>Uu_OutgoingCallOK_PS, Uu_CallDropped_PS and Uu_CallCompleted_PS The count of “Uu_CallDropped_PS” is the number of system-perceived call drops. The difference between “Uu_OutgoingCallOK_PS” and “Uu_CallCompleted_PS” is the number of user-

perceived call drops.


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7 5B ANNEX II: UL/DL Radio Synchronization

UTRAN and UE (Layer 1) constantly monitor the Uplink and Downlink for synchronization through Qin and Qout, whichare in-sync and out-of-sync primitives, respectively. It is important to understand this process because it is the sourceof dropped calls that can have misleading signatures.

7.1 13BDL Synchronization

Next Figure shows a Call drop due to loss of Downlink synchronization

Downlink out-of-sync is reported with each frame using the CPHY-out-of-sync-IND primitive, which checks to seewhether either of the two following quality criteria is true:

Downlink Dedicated Physical Control Channel (DL DPCCH) quality over the previous 160 ms is worse thanQout [3GPP 25.101. UE Radio transmission and reception (FDD)]. For this situation, Qout is not definedformally in the standard, but is commonly implemented using DL SIR.

All of the last 20 transport blocks received have CRC errors and, of the CRC-protected blocks, all transportblocks received in the last 160 ms have CRC errors.

If N313 successive out-of-sync indicators are detected at Layer 1, the UE waits for the T313 timer to expire beforedeclaring a radio link failure. T313 is implemented to allow the link to recover. If N315 successive in-sync indicatorsare detected, the entire out-of-sync process is reset. N313, T313 and N315 are broadcast in SIB 1.

Downlink in-sync is reported in every radio frame (10 ms), using the CPHY-sync-IND primitive. This process checksto see whether both of the following quality criteria are met:


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DL DPCCH quality over the previous 160 ms is better than Qin [3GPP 25.101. UE Radio transmission and

reception (FDD)].

At least one correct CRC is received in a TTI ending in the current frame. Only CRC-protected blocks areconsidered. The criterion is assumed to be fulfilled if no CRC-protected blocks are transmitted.

After Qout is detected, the UE Power Amplifier (PA) is turned off. Because the Downlink cannot be demodulatedreliably, power control information is not received; thus the PA is turned off to avoid generating interference on theUplink. If the Qout condition is maintained for N313 frames, the UE declares CPHY-out-of-sync. The UE then starts aprocess similar to initial acquisition of the radio link, because the system timing is considered lost at this point. If theacquisition process does not succeed within T313, the link is considered lost and radio link failure is declared.

The N313 and T313 parameters directly influence how long a call can be maintained in bad RF conditions . If theseparameters are too short, many calls may be prematurely dropped under rapidly changing RF conditions. On the otherhand, setting these times too long allows more time for calls to recover but may affect call quality and resourceutilization.

For simplicity, the example in the Figure above assumes that the UE PA turns off after the first Qout. The actualprocess is more complex: 160 ms after physical channel establishment, the UE turns its transmitter on or off accordingto the Downlink DPCCH quality criteria, as follows:

The UE turns off its transmitter when it estimates that the DPCCH quality over the last 160 ms is worsethan a threshold Qout.

The UE can turn its transmitter on again when it estimates that the DPCCH quality over the last 160 ms isbetter than a threshold Qin. When transmission is resumed, the power of the DPCCH is the same as whenthe UE transmitter was turned off.

This allows the UE to turn off its PA after 160 ms, but turn it back on only after 10 ms if the Qin threshold is lowerthan Qout. It is not uncommon for the UE to turn power on and off under bad RF conditions in response tosynchronization loss and recovery.

7.2 13BUL Synchronization

For the Node B, a similar process is available through the CPHY-sync-IND or CPHY-out-of-sync-IND primitives.The Node B monitors the Uplink synchronization [3GPP 25.214. Physical layer procedures (FDD)] and reports a CPHY-sync-IND or CPHY-out-of-sync-IND primitive to the RL Failure/Restored triggering function.

The Uplink synchronization criteria are not specified in the standard, but could be based on similarmeasurements –CRC and/or DPCCH quality.

With soft handover, a call could be supported by several radio links; therefore, some vendors have implementedseparate timers for individual links and the overall connection . If a radio link fails, only the link-specific timerexpires and only that specific link clears. Alternatively, if the connection timer expires, the connection would drop.

Documents

DCR PS et CS