15 OWJ200204 WCDMA Call Drop Problem Analysis

8/19/2019 15 OWJ200204 WCDMA Call Drop Problem Analysis

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Call Drop Problem

Analysis

ISSUE 1.0



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Call drop analysis is very useful for network

optimiation and trouble!s"ootin#.

$ollowin# dis%ussion will #ive t"e #eneral

ideas on t"is spe%ial topi%.



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Upon %ompletion of t"is %ourse& you will be able to'

Des%ribe t"e %ate#ories for %all drop %auses

Des%ribe t"e flow of #eneral %all drop

analysis

Analye %ommon %all drop %ases



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Chapter 1 Principle of Call DropCha

pter 1 Principle of Call Drop

Chapter 2 Analysis of Call DropChapter 2 Analysis of Call Drop

Chapter 3 Call Drop CasesChapter 3 Call Drop Cases



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Chapter 1 Principle of Call DropCha

pter 1 Principle of Call Drop

Section 1Section 1 Signaling Plane Call DropSi

gnaling Plane Call Drop

Section 2 User Plane Call DropSection 2 User Plane Call

Drop



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Prin%iple of Call Drop

("ere are two types of %all drop' si#nalin# plane %all drop and

user plane %all drop'

Si#nalin# plane %all drop means )*C will send t"e messa#e

+IU )E,EASE )E-UES( to C* after C* re%eives t"e +IU

%onne%tion setup %omplete

User plane %all drop means )*C will send t"e messa#e )A/

release reuest +to C* after C* re%eives t"e +)A/ setup

%omplete


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$ormula of Si#nalin# Plane Call Drop )ate

("e formula of Call Drop )ate of CS Si#nalin# Plane'

Call Drop )ate of CS Si#nalin# Plane )*C!ori#inated CS

Domain Iu Conne%tion )elease 2 )*C!ori#inated CS Domain Iu

Conne%tion Setup Su%%ess3 1004

("e formula of Call Drop )ate of PS Si#nalin# Plane'

Call Drop )ate of PS Si#nalin# Plane )*C!ori#inated PS

Domain Iu Conne%tion )elease 2 )*C!ori#inated PS Domain Iu

Conne%tion Setup Su%%ess3 1004


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5easurement Points of Si#nalin# Plane Call Drop

5easurement points of Si#nalin# plane %all drop

Call Drop )ate of Si#nalin# Plane is %al%ulated by %ountin# )*C!

ori#inated Iu %onne%tion release

A

IU )E,EASE C655A*D

IU )E,EASE C65P,E(E

)*C C*

IU )E,EASE )E-UES(



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Causes of Si#nalin# Plane Call Drop

Usually& t"e typi%al %auses for sendin# t"e IU7release messa#e

are as follows'

65 intervention

User ina%tivity )epeated inte#rity %"e%kin# failure

UE #enerated si#nalin# %onne%tion release

), out!of!syn%"roniation



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Chapter 1 Principle of Call DropChapter 1 Principle of Call Drop

Section 1 Signaling Plane Call DropSection 1 Signaling Plane Call Drop

Section 2 User Plane Call DropSection 2 User Plane Call Drop



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$ormula of User Plane Call Drop )ate

("e formula of Call Drop )ate of CS User Plane'

Call Drop )ate of CS User Plane )*C!ori#inated CS

Domain )A/ )elease 2 )*C!ori#inated CS Domain )A/

Setup Su%%ess 3 1004

("e formula of Call Drop )ate of PS User Plane'

Call Drop )ate of PS User Plane )*C!ori#inated PS

Domain )A/ )elease 2 )*C!ori#inated PS Domain )A/

Setup Su%%ess 3 1004



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5easurement Points of User Plane Call Drop

5easurement points of User plane %all drop

Call Drop )ate of User Plane is %al%ulated by %ountin#

)*C!ori#inated )A/ %onne%tion release

A

)*C C*

)A/ )E,EASE )E-UES(



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Cause of User Plane Call Drop

Usually& t"e typi%al %auses for sendin# t"e )A/ )elease

messa#e are as follows'

65 intervention

U()A* #enerated reason

)A/ preempted



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Chapter 2Chapter 2 The Analysis of call dropThe Analysis of call drop

Section 1 Main causes of high call drop rateSection 1 Main causes of high call drop rate

Section 2 Analysis flow of call dropSection 2 Analysis flow of call drop



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Analysis of Call Drop

A%%ordin# to t"e definition of %all drop measurement points& %all

drop is usually %aused by t"e followin# reasons'

Euipment problem.

)$ problem.



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Euipment Problem

Call drop arisin# from euipment problem

8ardware problem

(ransmission problem

Antenna and feeder fault

6t"er %auses



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)adio ,ink $ailure

Signaling process chart of radioSignaling process chart of radiolink failurelink failure

UE ode! "C C

5easurement )eport

5easurement )esult

), $ailure I*DICA(I6*

IU )E,EASE )E-UES( 9), $ailure:



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Analysis of Causes of )adio ,ink $ailure

Analye t"e %auses of t"e failure of radio links. ("e %auses%an be'

Interferen%e

; Internal interferen%e& e<ternal interferen%e and t"e

euipment interferen%e Poor %overa#e

; Covera#e "ole& dead one& isolated island&uplink2downlink unbalan%e

Improper parameter settin#

; radio link timeout %ounter& "andover& power %ontrolet%.



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)adio ,ink $ault ! Covera#e

Covera#e'

Covera#e overs"ootin#

Covera#e "ole

Si#nal attenuation

In%omplete definition of ad=a%ent %ells

unbalan%e of uplink2downlink





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8andover Problem

Delayed "andover

1:("e soft "andover t"res"old is too "i#" or t"e time!to!tri##er

settin# is too bi#.

?: ("e soft "andover area is too small.

Pin# Pon# 8andover

In t"e "andover area& be%ause of t"e si#nal flu%tuation& t"e UE

will probably repeat "andovers between t"e sour%e %ell and t"e

tar#et %ell.



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Chapter 2Chapter 2 The Analysis of call dropThe Analysis of call drop

Section 1 Main causes of high call drop rateSection 1 Main causes of high call drop rate

Section 2 Analysis flow of call dropSection 2 Analysis flow of call drop





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Call Drop ,o%ation Analysis

Call drop lo%ation analysis' based on t"e lo%ation of

t"e %all drop event in t"e map window in t"e post

pro%essin# tool& followin# information %an be

obtained'

("e pla%e of t"e drop %all

At t"e ed#e of t"e @ %overa#e or not

)elated %ells

Distan%e between related @ %ells and t"e drop

%all point



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*ei#"bor ,ist Analysis

*ei#"bor list analysis' to find out any %ell not defined in t"e

nei#"bor list& followin# information need to be obtained'

/est servin# %ell before t"e %all dropped

/est servin# %ell after t"e %all dropped

E<istin# nei#"bor list of t"e best servin# @ %ell



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Covera#e Analysis

Covera#e analysis' Analye t"e pilot %overa#e to #et

information about'

CPIC8 transmission power

B"et"er followin# %overa#e events take pla%e or not'

; Covera#e limited

; System interferen%e

; Poor uplink %overa#e

; Poor downlink %overa#e; Pilot pollution



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Covera#e Analysis

Covera#e analysis' Analye t"e pilot %overa#e to #et

information about'

CPIC8 transmission power

B"et"er followin# %overa#e events take pla%e or not'

; Covera#e limited

; System interferen%e

; Poor uplink %overa#e

; Poor downlink %overa#e; Pilot pollution



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Covera#e Analysis

Covera#e analysis' Analye t"e servi%e %overa#e to #et

information about'

Servi%e related 5a<imum downlink transmission power

SI) before t"e %all dropped

5a< uplink transmission power allowed for UE

A%tual uplink transmission power before t"e %all dropped



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8andover Analysis

8andover analysis to #et information about'

Si#nal stren#t" %"an#e of t"e tar#et %ell and t"e

servin# %ell

$ollowin# %ause e<ist or not'

; insuffi%ient "andover area

; too late to start C5

; too late to add tar#et %ell

; too early to delete servin# %ell

; intera%tion problem amon# type of "andover





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Case 1 $ault des%ription' ("e position of t"e drop %all was not in t"e

ed#e of t"e @ %overa#e. ("e %all dropped on %ell SC?0.



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Case 1

Analysis'

1.Poor %overa#e 'from t"e pa#e s"own &we %an find t"at

; before t"e drop& t"e best server for t"e UE is not t"e

same as t"at of t"e s%anner.

; t"e CPIC8 E%2Io 9and CPIC8 )SCP: de#rades for UE

6*, w"ile s%anner s"ows no de#radation.





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Case 1

(rouble!s"ootin# dis%ussion



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Case ?

$ault des%ription' ("e position of t"e drop %all was in t"e ed#e of t"e@ %overa#e& t"e %all dropped on %ell SC1G& t"e distan%e between

%ell SC1G was very far away from t"e drop %all point.



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Case ? Analysis

1. analye t"e a%tive set and monitor set information

before %all drop from UE measurement results

only s%1G in t"e a%tive set&

no %ell in t"e monitor set.



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Case ? Analysis

?. Analye t"e s%anner data in %on=un%tion wit" t"e UE data



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Case ?

(roubles"ootin# dis%ussion



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Case ?

Con%lusion to analye t"e %overa#e problem'

Analye t"e pilot %overa#e in %on=un%tion wit" t"e

servi%e %overa#e

Analye t"e uplink %overa#e in %on=un%tion wit" t"e

downlink %overa#e

Analye t"e s%anner data in %on=un%tion wit" t"e UE

data

Analye t"e CPIC8 )SCP in %on=un%tion wit" CPIC8

E%2Io& SC



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Case

$ault des%ription' ("e drop %all o%%urred in t"e area offreuent %"an#e of best server s"own by t"e s%anner



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Case Analysis

1.Compare E%2Io from bot" s%anner and UE at t"e time of

t"e drop' t"e UE E%2Io drop to H !1F d/ w"ile t"e s%anner

remained above ! d/ '





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Case

Analysis

. a%%ordin# t"e latest measurement %ontrol

messa#e& we %an find SCJ0 is in t"e list. ("e

drop %all is not t"e %ase of missin# nei#"bor.



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Case Analysis

G. It seems t"at t"e best %ell %"an#es from SCJ0 to SCJ0J

too fast for t"e UE to perform soft "andover on time.



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Case

Analysis

As t"e "andover t"res"old of 1a event is G.Jd/& t"e

delay is 0d/& t"e delay tri##er time is ?0ms& t"e filter

%oeffi%ient is 91 se%ond is reuired:& so t"e

reuirement for t"e "andover area is' t"e lastin# time

w"en 9E%2Io of J0 %ell K E%2Io of J0J %ell: H G.Jd/ is

about ? se%onds . ("e value in t"e %ir%le as s"own in

t"e dia#ram %annot meet t"e reuirement.



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Case Analysis

Uu7Interfa%e messa#es t"at 1a event of SCJ0J was tri##ered at JG'0G'



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Case

Analysis

/ut SCJ0 went bad too severe for t"e pro%edure of +A%tive

Set Update to be finis"ed'



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Case




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Case

$or analyin# t"e "andover problem& t"e followin#

information s"ould be obtained'

t"e si#nal stren#t" %"an#e of t"e tar#et %all and t"e

servin# %ell

w"et"er followin# %ause e<ist or not' insuffi%ient

"andover area& too late to start C5& too late to add

tar#et %ell& too early to delete servin# %ell& intera%tion

problem amon# type of "andover

w"et"er pin#!pan# "andover e<ist or not







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Case G

Analysis



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Case G Analysis

$urt"er investi#ation s"ows t"at UE reports event 1a of SC1、

SC1 before drop'



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Case G Analysis

In t"e pro%ess of addin# SC1 and SC1 to a%tive set& it is failed be%ause

of t"e wron# data %onfi#uration of nei#"bor )*C. ("e %ell ID are not

known by nei#"bor )*C.



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Case G




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15 OWJ200204 WCDMA Call Drop Problem Analysis

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