GSM Paging Issue Analyse

8/11/2019 GSM Paging Issue Analyse

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Wireless Network Planning Table of contents

Table of Contents

Chapter 1 Special Topic ........................... ........................... ........................... .................... ...... .... 11.1 The Problem of Coverage ........................... .......................... ........................... ....... ...... .... 1

1.1.1 Equipment Configuration ....................... ........................... .................... ...... ...... ...... 1

1.1.2 ase !tation !ite !election ......................... ........................... .......... ...... ....... ...... ... 1

1.1." #ntenna Engineering $esign an% &nstallation ....................... .................... ....... ...... . "

1.1.' #ntenna fee%er( combiner )%ivi%er*( C$+ connections ........................... ............. ... ,

1.1.- Parameters settings an% others .......................... ........................... ................. ...... .. ,1.2 TC Congestion .......................... ........................... ........................... ........................... ..... /

1.2.1 The Causes of igh TC Congestion 0atio ........................ ................. ...... ...... ...... /

1.2.2 Positioning etho%s of igh TC Congestion 0atio ..................... ...... ...... ...... ..... 11." 3oice Prompt ................................................................................................................... 1"

1.".1 Paging !trateg4 ........................... ........................... ........................... ....... ...... ...... 1"

1.".2 Paging proce%ure ......................... ........................... ...................... ...... ...... ...... ..... 1'

1."." #nal4sis on the Problem 5!ubscriber 6ut of the !ervice #rea5 ...... ...... ...... ...... .... 1-

1.".' !upplementar4 Notes ......................... ........................... ..................... ...... ...... ...... 171.' The Problem of !ignal 8luctuation ........................ ........................... .............. ...... ...... ..... 19

1.'.1 E:amine the !tableness of the ase !tation;s Transmission Power .......... ...... .... 19

1.'.2 Cell 0eselection )in i%le state* or an%over )in conversation state* .................... .. 1/

1.'." Power Control an% $T< ........................ ........................... .......................... ....... .... 1/1.'.' T0< $own .......................... ........................... ........................... ........... ...... ...... ..... 21

1.'.- &nterferences ........................... ........................... ........................... .................... .... 21

1.'., Cell Congestion ......................... ........................... ......................... ...... ...... ...... ..... 21

1.'.7 ultipath Effect ..................................................................................................... 22

1.'.9 6ther causes .......................... ........................... .......................... ........ ...... ...... ..... 221.- 6ther ain Problems ......................... ........................... .......................... ........ ...... ...... .... 2'

1.-.1 Poor 3oice =ualit4 ....................... ........................... ........................... .......... ...... ... 2'

1.-.2 8ailure to attach the network ....................... ........................... ........ ...... ...... ...... .... 2'

1.-." !low to attach the network ......................... ........................... ........................... ..... 2'1.-.' #ccess slow .......................... ........................... ........................... ................. ...... ... 2'

1.-.- unilateral connection ........................ ........................... ........................... .......... .... 2'

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Wireless network Planning Chapter 1 !pecial Topic

Chapter 1 Special Topic

1.1 The Problem of Coverage

#t present there are more or less problem of coverage in the network. The problem ofcoverage concerns a large number of aspects. This section anal4ses the problem ofcoverage that is available on>line from the perspective of base station selection(carrier configuration( antenna fee%er organi?ation( antenna installation( installationqualit4 an% parameter setting( etc.

1.1.1 Equipment Configuration

I. Combiner Configuration

!olution recommen%ations un%er normal circumstances@

8or cells with less than( or equal to 2 T0


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to the problem of coverage( the on>site surve4ing personnel shall insist theirviewpoints from the perspective of network coverage. The issue shall be e:plaine%thoroughl4 if it cannot be solve% ultimatel4. What shall be e:plaine% is also the basestation;s coverage areas an% ob ectives )in particular government offices( hotels(airports( resi%ential areas( main roa%s( shopping centers an% former cell;s coverage

margins*( as well as the cell;s carrier frequenc4 configurations. +suall4 for intensivel4populate% urban areas the height of the base station;s antenna is 2->" metersA theheight of the base station;s antenna in the suburbs )or the ones that point to thesuburbs* is ' >- meters. The planning personnel shall assist the network carriers to%eci%e the coverage areas an% ob ectives after a thorough stu%4 of the geographicalfeatures( the buil%ings; absorption an% loss features( an% multipath effect to ensurethat the base station will be constructe% as e:pecte%. 8urthermore( the base station(in particular the omni antenna base station shall not be too high. This is because theomni antenna;s vertical beamwi%th is narrow. &f the base station is too high( it willhave ba% coverage on the nearb4 area an% goo% coverage on the farawa4 areawhere there aren;t man4 subscribers. +suall4 the height of the omni antenna basestation shall not be - >, meters more than the covere% area. 8or base stations thatare too high( the built>in %own>tilt omni antennas or antennas with broa% vertical beamare %esirable.

II. The antenna !irection !ifference between the ol! an! newl" built networ#

8or %irectional cells( if the antenna %irection of the newl4 built network is %ifferent fromthat of the ol% network( such as@ the ol% antenna;s %irection was D12 D2' ( while thenewl4 built antenna;s %irection is , D19 D" . 8or omni cells( if the antenna %irectionof the newl4 built network is %ifferent from that of the ol% network( such as@ the ol%antenna;s %irection )transmit an% %iversit4 antenna* is D19 ( while the newl4 builtantenna;s %irection is / D27 . This will cause the change of the %iversit4 surface an%transmit antenna position. This ma4 make the previous goo% coverage a ba% one(an% previous ba% coverage a goo% one. ut the mobile phone subscribers are onl4concerne% with the change from goo% to ba%( which will give rise to complaints.

!olution recommen%ations@ $uring the engineering %esign( the antenna shall be so%esigne% as to make the %irection of it as i%entical as that of the ol% one. &n caseswhere the %irection change is %esire%( the main beam of the %irectional antenna orthe %irection of the omni antenna shall point to the places where heav4 coverage isemphasi?e%. $ue e:planations are also %esirable.

III. The !ifference of the antenna height between the ol! an! newl" builtnetwor#

The engineering %esign shall be so ma%e as to ensure that the height of the newantenna is not lower than that of the ol% antenna. &f the tower platform has not enoughspace to install the antenna( the e:planations shall be given for %ecreasing theantenna height.

I$. Concerning the !irectional antenna%s !own&tilt of the newl" built networ#

Preferabl4 the %own>tilt shall not change. &n cases where such change is %esire% %ueto the increase of the base station in the urban area for purpose of controlling thecoverage area( such change shall be %ul4 recor%e%.

$. Change omni cell to !irectional cell

#s the half power angle of the %irectional antenna;s beamwi%th is ,- or / %egrees(an% the beamwi%th of the omni antenna is ", %egrees( after the change( the

marginal coverage of the cell within the %irectional base station can be worse thanthat of the previous omni station. $uring the planning( make sure that the main beam

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of the %irectional antenna points to the area where emphatic coverage is %esire% an%%escribe the coverage %ifferences between the omni>antenna an% %irectionalantenna.

1.1.' Antenna Engineering (esign an! Installation

I. The problem of the !irectional antenna installation

enerall4( the base station;s uplink an% %ownlink signals are balance%. a% antennainstallation ma4 leave the mobile phone subscribers such impression that the basestation;s uplink coverage capacit4 is weak.

)1* The transmitting antenna is installe% inverse.

Transmitting fee%er an% the cell;s antenna were mistakenl4 connecte% or T! set top umper was mistakenl4 connecte%.

Possible phenomenon clue for fault %iscover4@The mobile phone is somewhere in the cell but cannot call out )thereceiving antenna is in the other %irection( the uplink is ba%*A

+nilateral call connectionA

8rom a %istance of the cell( %rop>off happens frequentl4 )infrequentnear the base station*A

$rop>off after frequent han%overs )the han%overs are foun% to bemostl4 cause% b4 weak uplink signal strength or ba% uplink qualit4*A

The fiel% intensit4 %istribution of the CC frequenc4 ban% between the

a% acent sectors were foun% to be %isplace% %uring the %rive testA+ne:pecte% severe interferences with the a% acent frequencies.

This t4pe of error is eas4 to %iscover in the network. &t can be foun% b4 checkinginstallation or b4 anal4?ing the fiel% intensit4 %istribution of the CC frequenc4 ban%%uring the %rive test.

)2* Wrong receiving antenna installation@

This problem( which cannot be foun% b4 anal4?ing the fiel% intensit4 %istribution of themain CC frequenc4 ban% in the %ownlink( can cause ba% uplink in the current cell.

#fter e:clu%ing the possibilit4 that it is cause% b4 transmitting antenna( check if the umper or fee%er of the receiving antenna are wrongl4 installe%( also review themeasurement report to see if the uplink level is too low( or if there are an4 call>out orhan%over problems( power control triggere% b4 the uplink signal( or irrationalhan%over ratio( etc.

II. The problem of sha!ow a!)acent to the coverage area in the !irectional cell

$uring the installation of the %irectional antenna( caution must be taken to avoi% thecreation of large area of sha%ow in its coverage area. !ha%ow usuall4 comes intobeing as a result of huge hin%rance near the base station( such as sk4scrapers( ormountains. Caution must be taken to circumvent such hin%rance %uring theinstallation. When the %irectional antenna is installe% at the surface of the top of thebuil%ing( caution must be taken so that the wave beam is not hin%ere% b4 the e%ge ofthe buil%ing( an% that the antenna is not installe% near the e%ge( thus re%ucing or

e:tirpating the sha%ow. $ue to the comple:it4 of the antenna surface( when theantenna must be installe% awa4 from the e%ge of the buil%ing( it must be installe% high

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above the antenna surface. 8or this reason( the bearing capacit4 of the buil%ingsurface an% the antenna;s against>win% force must be taken into account %uring theengineering.

III. The problem of the !irectional antenna !iversit" interval

The effective hori?ontal interval of the / %irectional antenna space %iversit4shoul% be more than 'm )at least greater than "m*A The effective hori?ontal interval ofthe 19 %irectional antenna space %iversit4 shoul% be more than 2m.

I$. The problems !uring the omni&antenna installation

6mni base stations are mostl4 locate% along the roa%s from villages to counties( orfrom counties to other cities. These base stations are mainl4 to serve the mobilesubscribers along the roa% or subscribers in the villages. The common mistake that isma%e %uring the installation of the antenna fee%er is that the %istribution of the abovesubscribers are not full4 taken into account( lea%ing to the incomplete utili?ation of theperformance of the base station( leaving the subscribers such impression that thecoverage is ba%. There are mainl4 " points concerning the %esign an% installation ofthe omni antenna@

)1* The interval between the omni antennas an% the interval between the antenna an%the tower

)2* $iversit4 %irection@ the %iversit4 surface shoul% be %irecte% to the area wheresubscribers are heavil4 populate%

)"* The position of the host transmitting antenna )T


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M S _ T X P W R _ M

M S _ T X P W R ( n )

H OB T S 1 B T S 2

R X L E V _ N C E L L ( n )

M s O p t L e v

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I. Static Power Setting

To re%uce the interference with the a% acent frequencies( lower the height of theantenna( increase the %own>tilt( or %ecreasing the base station;s transmitting power.

+suall4( %ecreasing the transmitting power can also worsen the in%oor coverage. !owhat are commonl4 a%opte% arefalling %own the height of the antenna an% increasingthe %own>tilt.

II. *AC+ Parameters Setting

To control the uplink access )call( paging response*( an% to balance between thecoverage an% call %rop ratio( uawei a%%s the parameter B0#C access threshol%5 inthe T!".< base station. The parameter can go upwar% from F11 % m( an%effectivel4 controls the mobile phone;s uplink access.

III. Cell Selection an! *eselection Parameters

C1 an% C2 %eci%e the cell selection an% reselection. 01 % m to F1 -% m. !etting the parameter too great willmake it %ifficult for the mobile phone to select the cell( which( when viewe% from thesubscriber;s perspective( is the mobile phone;s call %rop an% no coverageA !etting theparameter too small will lea% to the situation that the mobile phone can receive thesignal but cannot call out.

$uring the parameter setting( also note the %ifferences of sensitivit4 an% ma:imumtransmitting power between the / an% 19 networks( ignoring which ma4cause the unbalance between the uplink an% %ownlink.

I$. ,ther Parameters an! Phenomena

The setting of the ran%om access error threshol% can also restrict the mobile phone;saccess. &ts value( which is usuall4 greater than 19 ( is set sub ect to the ra%ioenvironment;s bottom noise an% statistical result. The other parameters settings thathave effect on the mobile phone attache%( access( han%over( an% connection are@

!&C( NCCHPE0 &TTE$( CEGGH #0H#CCE!!( CEGGH #0H=+#G&8I( ra%io linkfailure timer( the number of mobile phone;s ma:imum retransfer( the number of sen%%istribution time slots )the number of e:ten%e% %istribution time slots*( the number of!#CC multi>frames( the number of ma:imum ph4sical retransfer( ra%io linkconnection timer( location up%ate an% paging>relate% parameters )inclu%ing G#C%istribution*( han%over>relate% parameters( power control>relate% parameters( flowcontrol>relate% parameters( roaming permit>relate% parameters( T0< power settingsof %ifferent C$+ channels( etc.

When the base station;s upper clock is ba%( CJ )T +* is failure( propagation isunstable( or the carrier frequenc4 boar% is failure )no warning( sometimes stableinterferences*( the mobile phone;s accessing( call an% han%over )usuall4as4nchronous han%over* will be affecte%.

When the s4stem information is wrong or is not %elivere% correctl4( the mobilephone;s accessing( call or han%over will be affecte%.

When the frequenc4 interference is severe( the mobile phone;s accessing( call an%han%over will be affecte%.

When the channel is congeste% the mobile phone;s han%over an% call access will beaffecte%.

ultipath effect can lea% to signal fluctuation

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$uring the cell reselection an% frequent location bor%er up%ate( the signal of themobile phone will fluctuate.

$uring the connection( %irect re>tr4 an% loa% han%over cause% b4 congestion can lea%to strong fluctuation of the signalA Priorit4 han%over )for la4ere% network* an% e%ge

han%over )the e%ge han%over threshol% is set too low an% there is no P Than%over* can also lea% to strong fluctuation of the signal. &f the power control an%han%over parameters are not set properl4 %uring the signal fluctuation( the fluctuationwill be strengthene% until call %rop happens.

The cross>area coverage or coverage in the bor%er areas for %ifferent services can allcause problems( lea%ing to the subscriber;s huge increase of roaming bill. To solvethe problem( the coverage area shoul% be controlle% or enlarge% %uring the planningan% optimi?ation phase to avoi% mutual cell reselection or onl4 single>%irection cellreselection. !olve the problem b4 a% usting the height( %own>tilt( an% %irection of theantenna( C0 an% ! minimum access threshol%( an% #& table.

The mobile phone subscriber having not sufficient un%erstan%ing on the terrain(construction material;s absorption loss( or multipath effect will ten% to rise questionson coverage.

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1.2 TC+ Congestion

&n 2 1( the mobile phone companies in all the provinces presente% five in%e:es asnetwork qualit4 criteria. The4 are@ long %istance call success ratio( traffic call %ropratio( traffic channel availabilit4 ratio( ra%io successful connection ratio( an% worstcells ratio( the last two of which are %irectl4 influence% b4 TC congestion ratio.

1.2.1 The Causes of +igh TC+ Congestion *atio

The causes for high TC congestion ratio are man4( among others( %ata configurationproblems( har%ware problems an% e:ternal interference. ut in light of solution stepsan% sequence( it is %esirable to first check the software an% har%ware problems of theequipment per se( an% then check other equipment>unrelate% factors such as e:ternal

interference an% constraints %ue to comple: terrain)1* &nterface # trunk circuit %ata configuration errors.

)2* Carrier frequenc4 boar% faults or unstable performance( lea%ing to highcongestion ratio.

)"* a% base station har%ware installation causes unbalance% uplink an% %ownlinklevel( lea%ing to TC congestion.

)a* +plink branch@ antenna tower amplifier fee%er line %ischarge arrester settop connector %ivi%er or C$+ T0< boar%

$ivi%er casca%e% half>rigi% cable connection error( lea%ing to uplinklevel %iscrepanc4A

alf>rigi% cable %istortion or loose connector( lea%ing to the problemA

$ata bus problem.

)b* $ownlink branch@ T0< P# combiner or C$+ set top connector %ischargearrester fee%er line tower amplifier antenna

The transmit branch has antenna fee%er F stan%ing wave ratio warningA

alf>rigi% cable %istortion or loose connectorA

Cell antenna connection error or T0< natural transmit channel%iscrepanc4 cause the %iscrepanc4 in the coverage %irection an% areaof main CC carrier an% e:pansion carrier( lea%ing to TCcongestion.

)'* The repeater station is subor%inate% to the host cell. The repeater station %oesn;te:pan% as the cell %oes.

)-* &nterferences lea%ing to congestion

),* &solate% station or comple: terrain causes TC assignment failure( lea%ing tocongestion.

)7* uge real traffic lea%ing to congestion.

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1.2.2 Positioning -etho!s of +igh TC+ Congestion *atio

I. *emote Anal"sis of Congestion *atio Cause

)1* 4 traffic statistics anal4sis

4 con%ucting traffic statistics anal4sis on the cell;s TC performance(check if TC congestion is %ue to all>bus4 congestion. &f it is( theproblem can be solve% b4 network optimi?ation which %elegates thecell;s traffic to other cells( or b4 a%vising the operator to e:pan%.

&f the problem is not %ue to all>bus4 congestion( check if the congestionis relate% to interference( namel4( check interference 1 to -. &finterfere%( the cell;s call %rop ratio can be a little high.

0egister the receiving performance measurement traffic statistics tasks.=uer4 the traffic statistics result b4 ob ect an% see if the uplinkD%ownlinkmeasurement report in the same T0< is balance% to %eci%e if theuplinkD%ownlink har%ware branch is balance%. =uer4 the traffic statisticsresult b4 time an% see if there is an4 e:ceptions regar%ing themeasurement report number in the same cell to %eci%e if thecongestion is relate% to that boar%.

)2* 3iew the warning

Check the station warning to which the high>congestion>ratio cell belongs to see ifthere are an4 abnormal warning( such as 3!W0 warning( PC s4nchroni?ation lostwarning( uplink %ata bus warning( etc( an% %eci%e if the congestion is relate% to thatwarning( taking into account the traffic statistics.

)"* 0emote maintenance terminal of the base station

Check if the software of the boar%s in the base station is uniform. The versionupgra%e shall be sub ect to the notice from !+PP60T website.

+se the maintenance terminal of the base station to congest in turn the cell carrierboar%;s TC channels that have high congestion ratio to see if the high congestionratio is relate% to that cell;s carrier boar%. !olution principles@

&f the fluctuation of the congestion ratio is relate% to the block of thecarrier boar%;s channel( then ver4 possibl4 that boar% is at fault. Checkif there is an4 co>channel interference. Check the har%wareperformance of the uplink( %ownlink( an% the boar%.

&f the congestion is not relate% to the carrier boar%( then the whole cell

ma4 be interfere% or affecte% b4 the terrain.)'* +se the !ignaling #nal4?er to %iagnose the # &! interface message.

#ccor%ing to the call flow an% TC assignment failure statistics( use the !ignaling #nal4?er to trace the # &! interface message at ever4 high>congestion>ratio cell. Thefigure shown here uses #1 !ignaling #nal4?er( the %etaile% anal4sis of which is asfollows@

#nal4?e the assignment comman% #ssignment C $ %elivere% in !$CC ( as the TE&value in figure 1 >2( to %etermine the carrier boar% that !$CC is in. The carrierboar% that TC is in can be %etermine% b4 referring to the #08CN ra%io frequenc4ban%. $etermine if the assignment failures are all in a T0


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report. Gocal calling is require%.

&f assignment failure points to a certain T0< boar%( the cause can be one of thefollowing@

T0< boar% %own or unstable performanceA

Cause% b4 ba% uplinkD%ownlink level. The uplink branchD%ownlinkbranch har%ware is at faultA

a% uplinkD%ownlink signal qualit4. $eci%e which branch is interfere%(taking into account the mobile phone;s T# value.

Figure 10-2 ABIS signaling

&f the assignment failures are ran%oml4 %istribute% over the carrier boar%s of thewhole cell( the anal4sis on the measurement report ma4 point to the following causes@

)1* Comple: terrain within the coverage area of the base stationA

)2*&nterference of the frequenc4 ban% within the whole the cell( such as the one fromthe repeater station

II. E amination on the local base station

)1* Gocal maintenance@ !ee if there are an4 abnormal warnings an% solve themtimel4.

)2* Check if there are an4 such har%ware problems in the uplink an% %ownlinkantenna fee%er branch as loose connector( inverse antenna( half>rigi% cableconnection error( an% backplane loose wiring( etc.

)"* +se mobile phones for calling in the same placeA

Calling b4 ever4 carrier or b4 ever4 channel to see if there are an4 timeslots or boar%s that cannot be assigne%.

Check weather all the carrier;s %ownlink levels are approache%. 8or

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carrier boar% whose levels are uneven( replace the boar% oruplinkD%ownlink antenna fee%er s4stem to look for the causes.

Note@ for frequenc4 hopping cells( use comman% line parameters to change that cellto non>frequenc4>hopping cell for the convenience of local calling.

)'* $o the %rive test b4 the network optimi?ation software #NT>PG6T to see if there isan4 han%over e:ceptions( %ownlink interference for an4 clues on the problem ofcongestion.

)-* +se the spectrum anal4?er to look for the interference source.

),* !ee if the terrain of the station;s coverage area is comple:.

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1.' $oice Prompt

The voice prompt in ! is controlle% b4 the !C of ! network an% broa%cast tothe subscribers. !C pla4s the pre>recor%e% voice prompt in the channelcorrespon%ing to the voice car% accor%ing to the %ifferent cause values an% %ataconfiguration of the message. T4pical voice prompt problems can take the followingforms@

)1* When the calle% is in i%le state( BThe subscriber 4ou;re calling is bus45 or BThemobile phone 4ou;re calling has turne% off5 is %elivere%.

)2* When the calle% is in i%le state( BThe subscriber 4ou;re calling is out of the servicearea5 is %elivere%.

)"* When the calle% is in i%le state( B8or the time being the subscriber 4ou;re calling

cannot be accesse%5 is %elivere%.The reasons that cause the above phenomena can be some of the following@!ubscriber status management e:ception on the N!! si%e( roaming number fetchfailure( or no paging response.

&n the following section we emphasi?e on the anal4sis of the problem B!ubscriber outof the service area5.

1.'.1 Paging Strateg"

The primar4 causes for the problem of Bsubscriber out of the service area5 aretwofol%@ one is paging response time overA the other is no paging response. 8irst let;slook at how the paging is %one. The paging strateg4 can be %ivi%e% into the followingthree parts as per !C( !C( an% T!.

I. -SC Paging *etransfer an! Paging -o!e Selection

!C can page the same message for a ma:imum of four times. &f the latest paging isnot respon%e%( it will retransfer the paging message. The resen% time interval is "secon%s( " secon%s( 2 secon%s( an% 2 secon%s respectivel4. Two secon%s after thelast resen%( i.e.( twelve secon%s after the first retransfer( if the paging is notrespon%e%( !C will regar% it as time>over an% %eliver prompt tone of B!ubscriber outof the service area5 to the subscriber. The paging metho%s !C can choose areT !& an% & !&.

II. SC Paging /roup Calculation an! Paging -essage Transfer between the-o!ules

#fter !C receives the Paging 0equest %elivere% b4 !C( it will calculate the paginggroup that the paging belongs to b4 the last three %igits of & !&( the cell;s CCCchannel configuration( an% the paging block configuration( an% then %eliver PagingComman% to that cell. +n%er multiple mo%ules con%itions( the Paging Comman%nee%s to be transferre% between the mo%ules.

III. TS Paging 0ueue an! Paging Combination

#fter T! receives the Paging Comman% from !C( it will put the paging in the

Paging roup =ueue that the Paging Comman% %esignates( an% sen% the paging

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content of the paging group at intervals of the same paging frame perio%. #t present(ever4 queue length of the paging group in T! is /.&n one paging reserve block( 2& !& paging or ' T !& paging can be %elivere%. !o ever4 time the paging is%elivere%( T! must combine the paging accor%ing to the paging message t4pe in thequeue.

I$. -S Paging (etection an! Paging *esponse

When in i%le state the mobile phone can not onl4 receive the s4stem information fromthe broa%cast channel( but also %etect paging in its Paging !ub>channel. Thereforewhen the mobile phone receives the paging that is %irecte% to it( it will sen% Channel0equest to the Network !i%e an% finish an immi%iate assignment process. &f theassignment is successful( it will report the Paging 0esponse in the assigne% !$CCchannel an% complete a call connection process.

8aults in an4 one of the above>mentione% four steps will lea% to the problem ofBsubscriber out of the service area5.

1.'.2 Paging proce!ure

When in i%le state( the mobile phone will sta4 in a cell that belongs to a location area.The mobile phone;s location area information is store% in 3G0. When a mobile phoneis being calle%( !C will rea% the mobile phone;s location area an% status informationfrom 3G0. &f the mobile phone is in B#ttache%( &%le5 state( it will sen% Paging 0equestto the !C to which the location area belongs. The !C will calculate the mobilephone;s paging subgroup( create Paging Comman%( an% %eliver the PagingComman% to all the cells in the location area. When in i%le state the mobile phonecan not onl4 receive the s4stem information from the broa%cast channel( but also%etect an4 paging in the Paging !ubchannel to which it belongs. Therefore after themobile phone receives the paging that is %irecte% to it( it will sen% Channel 0equest to

the Network !i%e an% finish an immi%iate assignment process. &f this immi%iateassignment is successful( it will report Paging 0esponse to the assigne% !$CCchannel an% complete a call connection process.

Note@ The Paging 0esponse is reporte% in Establishment &n%ication.

8or e:ample@ all the cells in a region belong to one location area( the common controlchannel parameter configuration for the cells is as follows@

6ne non>combine% CCC

The number of frames between the same paging@ ,

The number of access reserve block@1

Thus( there are ,:)/>1*K'9 paging groups in ever4 cell. The mobile phone will %eci%ethe paging group it belongs to accor%ing to the last three %igits of its & !& an% thenumber of the paging groups( then %etect in the relevant sub>channel. 8or a mobilephone whose number is 1" 1"",2 ( an% the & !& is ', 1"",1 "7( the lastthree %igits of its & !& is "7( its paging sub group is "7.When in i%le state( the mobilephone will alwa4s listen to the paging sub channel relate% to the No. "7 paging group.&f someone calls 1" 1"",2 ( the paging will be sent to that subscriber from thecells in that area. #fter the mobile phone receives the paging %irecte% at', 1"",1 "7( it will sen% a channel request( an% finish an instant assignmentaccor%ing to the instant assignment from the network si%e. &f there is i%le !$CCchannel in the cell( a !$CC channel will be assigne% to that mobile phone( themobile phone establishes the connection in the channel( an% reports the pagingresponse.

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1.'.' Anal"sis on the Problem Subscriber ,ut of the Service Area

The reasons that cause B!ubscriber out of the service area5 are the time>out of themobile phone;s response to the paging or no response. 8rom the flow of the paging

response report an% anal4sis on the real cases( there are the following reasons thatcause this problem@

I. -SC subscriber status management

&f !C subscriber status management is %own an% the request cannot be %elivere%to !C( then ! will fail to receive the paging an% to respon%( lea%ing to time>out. &nreal situations( there are cases when !C %i%n;t %eliver the paging. There were alsosuch abnormalities as faulte% calle% being regar%e% as caller an% "Tick releaseabnormalities. !uch abnormalities are non>recurrent. #n% can be i%entifie% b4 beingtrace% b4 the ! subscriber interface of !C aintenance !tation.

II. *eceiver in the base station

&f the receiver of the base station( inclu%ing $!P( T0off(causing some to have long time in accessing( lea%ing to the problem of B!ubscriber

out of the service area5. +n%er the protocols of ! 2 an% "( after the call %rop themobile phone follows the principles of #!#P )as soon as possible* an% energ4 savingto access the network. The mobile phone will attempt to access the network inreceiving signal;s strength or%er. / mobile phones search " frequenc4 ban%sA19 mobile phones search ' CC frequenc4 ban%sA $ouble frequenc4 mobilephones search 7 frequenc4 ban%s. #fter the faile% attempt( the mobile phone will%eci%e when to start ne:t time accor%ing to its own algorithm. obile phones of%ifferent mo%els have %ifferent algorithms. 8or e:ample( some mo%els of otorolamobile phones can set accessing network frequenc4. +n%er the low spee% accessingmo%e( it takes - minutes to access the network after the mobile phone %rops off thenetwork an% re>enter the coverage area. &n a%%ition mobile phones of %ifferentmanufacturers have %ifferent accessing mo%e. !ome mobile phones( after severalfailures in fin%ing the network( will stop %oing so for a long time to come. !o( thisproblem is relate% to the mobile phone itself an% can be solve% b4 the switch on an%

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switch off of the mobile phone.

I$. plin# 3 (ownlin# nbalance of *a!io 4in#

The ra%io signal can be classifie% into uplink an% %ownlink accor%ing to thepropagation %irection. &%eall4 the uplink>%ownlink are at balance( that is to sa4( at an4area the base station an% the mobile phone can receive )or not receive* the othersi%e;s signal simultaneousl4. The uncertaint4 of the ra%io signal propagation an% the%iscrepanc4 of the actual circumstances %ictate that complete balance within thewhole network is impossible. !o in the network there must be some areas where he%ownlink signal can cover but the uplink signal cannot. &n these areas( the subscribercan receive message sent b4 the network( while the network cannot receive themessage reporte% b4 the subscriber( inclu%ing paging response. Therefore in theseareas it is ver4 common for the B!ubscriber out of the service area5 message to occur.To solve such problem of B!ubscriber out of the service area5( a% ust the ra%ioparameters such as B0#C access threshol%5( Bran%om access error threshol%5( B !minimum access level5( an% B0!!& check5 to optimi?e the balance. &n particular( notethat the %isplacements of the measure% level value in the measurement report for%ifferent versions of base stations are %ifferent.

$. S(CC+ Congestion

#fter the mobile phone receives the paging comman%( it will sen% channel request tothe network si%e. &f there is no !$CC channel available( or if the proce%ure to set up!$CC channel fails( the paging response cannot be %elivere% to the network si%e(thus the problem of B!ubscriber out of the service area5 occurs. The causes for the!$CC congestion are !$CC all bus4( ran%om ra%io link failure( etc. 8or the!$CC all bus4 situation( a% ust that cell;s coverage area to re%uce the !$CCcongestion. 8or congestion cause% b4 other reasons( such as ran%om ra%io linkfailure or surface link failure( the solution is sub ect to real situation.

$I. PC+ ,verloa!

The paging message in the network is ran%om. $ue to the restrictions on thestructure of the ra%io channels an% the limitations on the capabilit4 to sen% the pagingcomman%( it is possible that some of the paging groups are overloa%e%( lea%ing tofailure to sen% the paging messages out timel4( an% the resen% paging cannot berespon%e% within the vali% time( thus causing the problem of B!ubscriber out of theservice area5.

This situation can be improve% b4 mo%if4ing CCC configuration parameters Bthenumber of frames in the same paging5( Bthe number of access grant reserve% block5(an% BCCC channel allocation5. 0e%ucing Bthe number of access grant reserve%block5 to a proper e:tent will increase the number of PC sub channels( thusincreasing the capacit4 of the paging channelsA 0e%ucing Bthe number of frames inthe same paging5 will improve the frequenc4 of sen%ing the paging messageA&ncreasing the number of CCC channels in the cell can significantl4 improve thes4stem;s paging capacit4( but at the same time re%ucing the number of TCconfigurations. Thus this metho% is sel%om use%. &f PC is severel4 overloa%e%( thesi?e of the location area nee%s to be re%uce%( thus lowering the flow of the pagingmessage.

$II. -obile Phone 0ualit"

When the mobile phone;s ra%io frequenc4 mo%ule is %own( the antenna loosens( orthe batter4 is %own( its receiving sensitivit4 goes %own( the uplink signal qualit4

worsens( an% the capabilit4 to receive the paging comman% an% access the networklowers. obile phones with such problems are prone to have the phenomenon of

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B!ubscriber out of the service area5. The evaluation on the qualit4 of the mobilephone sometimes requires special %evices. The problems of the mobile phone cantake the following forms@

)1* a% power suppl4 lea%s to insufficient uplink transmitting power an% uplink access

failure.)2* 8aulte% mobile phone software lea%s to the mobile phone;s e:ceptional %ea%>en%an% failure to respon% to the paging message.

)"* Problems in the ra%io frequenc4 part of the mobile phone will lea% to failure toreceive( unstable transmission( or high frequenc4 error within some frequenc4 ban%.

$III. 5on&comprehensive Coverage

&n areas where the ra%io signal coverage is not goo%( usuall4 in%oors( the signalqualit4 is likel4 to be ba%( an% the call %rop is not uncommon .#s the subscriber statusin the 3G0 has not change%( when that subscriber is being calle%( the network si%ecan %eliver paging message normall4( but the subscriber cannot receive the pagingmessage an% cannot respon% to the paging message. 6r because of the low qualit4of the signal( the paging response cannot reach the network si%e. &t is normal un%erthis circumstance that B!ubscriber out of the service area5 occurs. 8or suchB!ubscriber out of the service area5 phenomenon( the qualit4 can be improve% b4increasing the number of the base stations an% perfecting the coverage.

There is a significant percentage of complaints concerning the problem of B!ubscriberout of the service area5 that is %ue to ba% coverage.

1.'.6 Supplementar" 5otes

&n the wireless network( because of the ra%io channel congestion or ra%io signalcoverage( it is certain that the problem of BNo paging response5 occurs.

&n some areas where the coverage is ba%( ba% signal qualit4 will lea% to the failure to%eliver the paging or paging response to the peer si%e( causing the phenomenonB!ubscriber out of the service area5.

8or e:ample( %ue to the temporar4 congestion of the !$CC channel( the ! cannotbe assigne% an !$CC channel( an% the paging response cannot be reporte%( inwhich case the first %ial ma4 receive the prompt tone of B!ubscriber out of the servicearea5 an% the secon% %ial ma4 succee%. #s the paging sub channel of the cell wherethe subscriber is in is fi:e%( so the chance for that sub channel overloa% increasessignificantl4. Calling that subscriber man4 times will be ver4 likel4 to encounter thephenomenon of B!ubscriber out of the service area5. These phenomena are all

normal no>paging>response.&t is an e:ception onl4 when the attempt to call an i%le state subscriber with goo%signal continuousl4 for a long time receives B!ubscriber out of the service area5.

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1.6 The Problem of Signal 7luctuation

The causes that can lea% to the mobile phone;s signal fluctuation are@

)1* 8luctuation in the base station;s transmission power

)2* Cell reselection )in i%le state* or han%over )in conversation state*

)"* Power control( $Tcell coverage(( frequent cell reselection an%han%over can also arise( lea%ing to the fluctuation of the signal.

1.6.' Power Control an! (T:

When the power control or $T< is %own( the receiving level in the mobile phonefluctuates. &f the threshol% value for the uplink power control is set too low( the uplinksignal from the mobile phone to the base station will be weak( This( together with thenormal fluctuation in the ra%io space( will give rise to han%over. $uring han%over( ifthe a% acent signal;s qualit4 is not strong to maintain the conversation( call %rop will

arise. Naturall4 the Gevel &n%icator in the mobile phone will go %own to one scale or?ero scale from the previous full scale.

Phenomenon;

The Gevel &n%icator points to full scale( su%%enl4 the peer;s voice at the other en% ofthe line cannot be hear% in the mi%%le of the conversationA the Gevel &n%icator in themobile phone points to one scale or ?ero scale. Call %rop happens. #fter severalsecon%s the conversation is on again.

Proce!ure an! Anal"sis;

The Gevel &n%icator pointing to full scale means that mobile phone is in goo% receivingqualit4. The level value at this time is about >7-% m. &f the %ownlink level e:cee%s thisvalue( the level fluctuation cannot be %ispla4e% in the mobile phone. !o suchfluctuation is not eas4 to be seen when the signal is strong. !o when the network;s

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%ownlink power control is on( it is %esirable to set the %ownlink level control to>7-% m.6ne further note@ the level in%icate% in the mobile phone is the mean value ofits ra%io frequenc4 level. !o the signal fluctuation of the narrow pulse %uration will bepartl4 smoothe% awa4. !o the scale change in the Gevel &n%icator is not the real>timeperformance of the receiving signal;s strength. &t is %ela4e%. $uring %iagnosis( we %i%

the following monitoring an% testing@ Test the %ownlink power at the combiner;s testinterface( no fluctuation was foun%A the %ownlink power at the %rop>off point wasmeasure% to be >9-% m b4 the spectrum anal4?er. Though there was a fluctuation of1 >1-% ( its minimum level was not enough to %rop off the mobile phoneA Ne:t wemonitore% an% teste% the %ownlink level of the mobile phone b4 connecting it tomobile show( we foun% that starting from a certain time )sub ect to small %ifferencesever4 time*( the level went %own from F9-% m along the , %egree slope( when itwent to the mi%%le of the slope( there happene% a han%over( but the strength of thesignal continue% to go %own( until at last the level was almost the same with that ofthe other areas )about F1 -% m*( an% maintaine% at this value for about 1 secon%san% then it %roppe% off. &f after 1 secon%s it %i%n;t %rop off( it went upwar% along the, %egree slope after another 1 secon%s( an% there happene% a han%over in themi%%le of the slope. Then it continue% to go upwar%( an% maintaine% some time forconversation at about F9-% m.Then it repeate% the above proce%ure( making its pathlike a slope% square wave( until it %roppe% off at some trough. 4 watching the +minterface from the backgroun%( we foun% that before or after the %rop>off an%han%over( the %ownlink receiving level was strong an% stable( an% the uplink levelwas mostl4 at F1 -% m.!o it can be %etermine% that the han%over an% %rop>off werecause% b4 the ba% uplink qualit4( that is to sa4( because of the effect from the uplinkpower control( the uplink signal has almost approache% the uplink level;s minimumthreshol% value when it reache% the base station. That( along with the normalfluctuation un%er the ra%io environment( will cause the base station to think that theconversation qualit4 in that cell is poor( so it or%ers the mobile phone to han% over tothe a% acent cell. &f the qualit4 in the a% acent cell is goo%( the conversation goes on(otherwise( there will be a %rop>off. &n light of the call %rop( the level in%icate% in themobile phone after the han%over is the %ownlink level of the a% acent cell. #n% the%ownlink level of the a% acent cell is quite small( so naturall4 the mobile phone;s levelgoes %own to 1 scale or scale. &f the signal in the a% acent cell is not sufficient tosustain the conversation or the %rop>off( the base station will or%er the mobile phoneto han% over back to the previous cell. &f this time it is successful( the conversationcan go on( the level in the mobile phone will return to full scale from scale. This isthe reason wh4 the conversation su%%enl4 cuts off but %oesn;t call %rop( an% after awhile( the conversation recovers. When the subscriber is having long timeconversation( %ue to the perio%icit4 of the above square waves( along with theran%omness of the environment;s fluctuation in the ra%io space( the subscriber wille:perience intermittent cutoff an% recover4( )not necessaril4 cutoff at ever4 trough( butcertainl4 weakening of the conversation qualit4*( until call %rop happens. #s the uplinkpower control makes an4 level from the mobile phone to the base station ver4 weak(giving rise to %rop>off regar%less of the %istance. Certainl4 as the ra%io fluctuation forthe mobile phones that are near to the base station is small( so is its chance of call%rop. #s the in%oor ra%io fluctuation is greater than out%oor ra%io fluctuation( so is itscall %rop ratio. &n a%%ition( the antenna is usuall4 place% at high tower( ( the ra%iationlobe is in fusiform( so the area right un%er the tower is blin%e%. The coverage onl4reaches to the e%ge of the lobe. The carrier;s office is usuall4 locate% at that area(an% the4 keep performing trial %ialing( so the chance for the fluctuation is greater.

Solution;

8irst make some brief u%gments accor%ing to the above anal4sis. &f the situations arelikewise( call the uplink power control parameters from the backgroun% an% set thereasonable threshol% value )preferabl4 F9 % m.&n a%%ition the parametersconcerning the han%over nee% to be set as per the real situation( the reasonableness

of which will affect the qualit4 of the network an% the fluctuation of the signal. Please%o the mo%ifications onl4 after a thorough un%erstan%ing of the meaning of each

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parameter( an% test the mo%ifications.

1.6.6 T*: (own

Phenomenon;

The mobile phone;s 0eceiving !ignal &n%icator points to the full scale. When thesubscriber %ials the number an% press L6JM( the mobile phone %rops out within afew secon%s( at the same time the &n%icator lowers to one scale or ?ero scale. Thisphenomenon happens intermittentl4.

Cause an! Anal"sis;

#fter L6JM ke4 is presse%( CC assigns a TC to the mobile phone through!$CC . When the T0< where the TC is locate% is %own( such as no power outputor output too small( then the TC will fail to set up the communication( lea%ing to%rop>off( an% the &n%icator lowering from full scale to 1 scale or scale. #fter a fewsecon%s it will return to the Wait !tatus( an% the &n%icator returns to full scale. #s theTC ;s assignment is %4namic( that is to sa4( the first subscriber occupies the firstcarrier frequenc4( the first time slotA the secon% subscriber occupies the first carrierfrequenc4( the secon% time slot( an% so on. #fter eight subscribers; calls( )or onesubscriber;s eight consecutive calls*( TC will switch to the secon% carrier frequenc4(thus lea%ing to normal conversation after several calls. #s the number of callers islarge( the interval for the e:aminer to encounter such fault ma4 var4. #n% the morethe number of carrier frequencies in the cell( the more %ifficult for it to %iscover thecause. 6n the other han%( there is no fault warning when the carrier frequenc4 is notbeing use%( but the warning of Power Too !mall after the assignment.

Solution;

!ee if there is an4 warning in the T0< at the backgroun% when the mobile phone is

having call test. &f 4es( replace that T0< with the a% acent carrier frequenc4 amplifieror T0faultboar%. 8urthermore( this metho% can be one of the effective wa4s to %etermine ifthere are an4 faults in the carrier frequenc4 channels at the cell. #t the openingphase( use two mobile phones an% finish continuous testing on all the carrierfrequencies at the cell within several minutes.

1.6.< Interferences

&nterferences can lea% to signal fluctuations. &nterferences can cause the timeout forthe $C! counter )/ Dthe multiframes between the same paging* in the mobile phonesat the current service area( thus lea%ing to cell reselection( which when reflecte% on

the mobile phone si%e( is the fluctuation of signals.

1.6.= Cell Congestion

8irst let us e:plain the problem b4 anal4?ing the signals@ #fter a call is initiate% b4 themobile phone( first !$CC channel is assigne%( after the correspon%ing signaling isfinishe%( a TC will be assigne% to the mobile phone for its use b4 the network. Whatis the normal proce%ure is that !C activates a TC channel b4 sen%ing to T! inthe current cell a signal activation comman%( an% then the channel is assigne% to themobile phone. ut what actuall4 happens is that )in times when the current cell iscongeste%* the network gives the mobile phone a comman% to switch to other cells(whose signal is weaker than the current cell. #s a result( the level goes %own

imme%iatel4( lea%ing to the fluctuations of the signal. &t is possible that after the

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penalt4 time the mobile phone switches to other cell again( whose signal is stronger(in which case the level in%icate% in the mobile phone goes up. 6r after hooking themobile phone is in &$GE state an% receives the CC signal from the cell where themobile phone is in( which reflecte% in the &n%icator is the going up of the signalstrength. Therefore the essential cause of this problem is too much traffic( causing

congestion in the cell.

1.6.> -ultipath Effect

ultipath effect is one of the main causes that lea% to the signal fluctuation in thenetwork. The performance of the ra%io communications s4stem is largel4 constraine%b4 the ra%io channel. The propagation path between the transmitter an% receiver isver4 comple:( ranging from the simple visual %istance propagation to encounteringsuch terrain as buil%ings( hills an% trees. The form the electromagnetic wave takes topropagate is %iverse. &n the main( it can take the forms of reflection( %iffraction( an%scattering. ost cellular ra%io s4stems operate in the cit4. There is no visual pathbetween the transmitter an% receiver( an% what;s more( the sk4scrapers pro%ucestrong scattering loss. 8urthermore( as %ifferent ob ects have %ifferent multipathreflections( the electro>magnetic waves( after passing paths of %ifferent length(interfere to pro%uce multi>path loss. #t the same time the strength of the electro>magnetic waves attenuates as the %istance between the transmitter an% receiverincreases. The attenuation in the ra%io environment can be classifie% into fastattenuation an% slow attenuation accor%ing to the estimation on the fiel% intensit4.

&n sk4scraper cities( as the height of the mobile antenna )mobile phone* is muchlower than that of the surroun%ing buil%ings( there is in most cases no visualpropagation between the mobile station to the base station( thus causing attenuation.Even if there is such a path for visual propagation( multipath effect ma4 still arise %ueto the reflection of the surface an% the surroun%ing buil%ings. The inci%ent wavesarrive in %ifferent %irections an% have %ifferent propagation %ela4. The signal receive%

b4 the mobile station at an4 position in the space consists of man4 signal waves(which have ran%oml4 %istribute% amplitu%e( phase( an% inci%ent angle. Thesemultipath components are combine% in vectors b4 the receiver( thus giving rise to theattenuation an% infi%elit4 of the signal being receive%. Even when the mobile receiveris static( attenuation can still arise as the signal being receive% is affecte% b4 thepropagation me%ium )the air flow change*( or b4 the moving ob ects where the ra%iochannel is in.

The metho% the base station uses to solve the fast>attenuation phenomenon is space%iversit4 )polari?e% %iversit4*( i.e. host %iversit4 antenna. The effectiveness of this host%iversit4 receipt is guarantee% b4 the irrelevanc4 of the host %iversit4 antenna receipt.

4 irrelevanc4( it means the signal receive% b4 the host antenna %oesn;t have thesimultaneous attenuation feature with the signal receive% b4 the %iversit4 antenna.

This requires that the gap of the host %iversit4 antenna is 1 times greater than thera%io signal wavelength )for ! / the antenna gap must be greater than 'meters*( or that the polari?e% %iversit4 is use% to guarantee the %ifferent attenuationfeatures of the signals receive% b4 the host %iversit4 antenna. Whereas the singleantenna mobile station )mobile phone* is helpless before the fast>attenuation featureun%er the wireless environment. !o multipath will lea% to the fluctuation of the mobilephone;s receiving level.

1.6.? ,ther causes

)1* Poor antenna fee%er connection will lea% to ups an% %owns of the stan%ing wave(which when reflecte% in the mobile phone( is the fluctuation of the signals

)2* !erious propagation flickers will lea% to the amplification of the onDoff in the base

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station.

)"* !ome mobile phones will also have fluctuation of the level when %oing locationarea up%ating. This is especiall4 so when in the location area bor%er of the cit4.

)'* The signal level after the assignment will fluctuate %eepl4 %ue to the %ifference ofthe carrier combination metho% or the %isaccor% of transmission channel gain withinthe cell.

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1.< ,ther -ain Problems

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be intro%ucte% in %etail in other %ocuments.

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Documents

GSM Paging Issue Analyse