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GSM Interference Analysis Analysis
GSM Interference AnalysisTable of Contents Table of Contents Course Description .............. ............................. ............................... ................................. ............................... ................... ..... 1 Introduction to Course………………………………………………………… Course ………………………………………………………… 1 Course Objective ……………………………………………………………… Objective ……………………………………………………………… 1 Relevant Materials ............... ............................... ................................. ................................ .............................. ...................... ....... 1 Chapter 1 Overview ............... ............................... ................................. ................................ ............................... .................... .... 1.1 Affection of Interference on Network ................ ................................ ............................... ..................... ...... 2 Interferences Sources .............. ............................ ............................... .................................. ............................... ................. ... ! 1.2 Classification of Interference Sources ............... .............................. ............................... ..................... ..... 3 1.2.1 Natural Noise ............... .............................. ................................ ................................. ............................... ....................... ........ 3 1.2.2 Man ade Noise ............... ................................ ............................... ............................... ................................. .................. .. 3 1.3 Main Interference Sources Affectin! Mobile Counication ................ " Discovery of Interference ............... ............................... ................................ ................................ .......................... .......... # 1." #iscoverin! Interference via OMC $raffic $raffic Measureent........... Measureent ........... ............ % 1.& OMC Alar and Subscriber Co'laint............... Co'laint............................. ............................... ..................... .... ( 1.% #iscoverin! Interference via #rive $e $est st............... ............................... ................................. ................... .. ( Chapter $ocation an% Clearance of Interference Source ...................& 2.1 Recoended )rocedures for *ocation and Clearance of Interference+++++++++++++++++++++++++++., 2.1.1 #eterine Interference Cell accordin! to -e )erforance Inde/ 0-)I .............. ............................... ............................... ............................... ................................. ............................... ............................... ................, , 2.1.2 Ceck Alar of OMC O MC ............................................ ............................................................ .............................., .............., 2.1.3 re4uenc )lannin! Ceck ............................................. ............................................................ ...................., .....,
2.1." Ceck )araeter Settin! of Cell....... l................. .................... .................... .................... ................... ..................1 .........15 5 2.1.& #rive $es est.................. t................................ ............................... ................................. ............................... .........................15 ..........15 2.1.% Interference Clearance .............. ............................. ............................... ................................. ........................15 .......15 2.2 *ocation and Clearance of 6ardware ault..................................................... 15 2.2.1 Antenna )erforance #e!radation ............................................. ..................................................15 .....15 2.2.2 7ater See'a!e See' a!e of Antenna or eeder ............... ............................... ...............................1 ...............11 1 2.2.3 8u'er Connector ault............... ault.............................. ............................... ................................. ......................12 .....12 2.2." Antenna Connected Inversel ............................................. ...........................................................12 ..............12 2.2.& Incorrect 8u'er Connection of 9$S .............. ............................... ............................... .................1" ...1" 2.2.% $R: ault.............. ault............................. .............................. ................................ ................................. ..............................1" ..............1" 2.2.; Clock er ............... ............................... ...............................35 ...............35 ".2 #irectional Antenna ............... ............................... ............................... ............................... ...............................35 ...............35 Chapter ) *ay to Te Test st Interference Inte rference ............... ............................... ............................... ........................!1 .........!1 &.1 $e wa to $est $est Internal Interference ............... .............................. ............................... ...................31 ...31 i
Course Description Intro%uction to Course #o i nt r od $c e a ff ec ti on b r o$ %h t b ! i nt er f er e nc e t o t he G SM s !s tem & f a$ t oc at io nm e t h o d a n d t r o $ b e s h o o t i n % m e t h o d & t h i s c o $ r s e h e r e b ! i s t s o $ t t h e p o s s i b e i nt er fe re nc e s o$ rc es & a nd of fe rs d es cr ip ti on of c as es to f a ci i ta te f a$ t oc at io n a nd t ro $b e sh oo ti n% . # he m ai n c on te nt s o f t he c o$ rs e a r e a s f o o w s : o ' e r ' i e w& cassification of interference so$rce& ($d%ment method& ocation and tro$beshootin%& anti-interference meas$res& introd$ction to instr$ment interference test& etc.
Course Ob+ective After competed the co$rse& !o$ can: •
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%et the ca$se of interference and master the method of ocatin% the interference so$rce Master the method of o'ercomin% interference.
,elevant Materials i n a
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?SM )rinci'le and Network O'tii>ation 6an 9injie Mobile Counication @n!ineerin! *u @rRui
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Chapter 1 Overview *re+$enc! reso$rce is a )ind of rare reso$rce. In GSM s!stem& fr e+ $e nc ! re$ se is 'er! necessar! for GSM s!stem to pro'ide eno$%h capacit!. *re+$enc! re$se means that same fre+$enc! can be $sed sim$taneo$s! in se'era ces when the distance bet ween the m is far eno $%h. #he dis tan ce betw een th e ce s a o cat in % th e sa me fre+$enc! is caed the re$se distance. And the ratio between the re$se distance andthe ce rad i$s is ca ed cofre+$enc! interference factor. *or certain fre+$enc! reso$rce& the networ) capacit! wi be ar%er if the fre+$enc! re$se is more ti%ht& b$t the interference wi be stron%er beca$se the re$se distance becomes nearer .#he interference ca$sed b! fre+$enc! re$se is caed interna networ) interference ,iti s a s o c a e d i n t e r n a s ! s t e m i n t e r f e r e n c e . e s i d e s & t h e G S M n e t w o r ) m a ! b e affected b! interference from other comm$nication s!stems. $d%in % from the aspect s s$ch as con'er sation +$ait !& ca dr op & ha nd o' er an d con%estion& it is fo$nd that interference sit$ation is one of the most important factor that affects the networ). ow to red$ce or eiminate interference is now becomin%t h e p r i n c i p a t a s ) o f n e t w o r ) p a n n i n % a n d o p t i m i 1 a t i o n . # h i s d o c $ m e n t h e r e i n p ro 'i de s a s ! st em ic d es cr i pt io n of i nt er f er e nc e so $r ce & in te rfe ren ce o ca ti on an dtro$beshootin% on the basis of e/'erience of e/'erts.
1.1 Affection of Interference on -etwor 7en tere is interference in te networkB te subscribers usuall encounter te followin! 'enoenon #urin! conversationB te subscriber usuall cannot ear te voice and te back !round noise is too loud. •
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7en fi/ed tele'one subscriber calls MS subscriberB or MS su bsc rib er ca lls fi/ed tele'one subscriberB call dro' occurs after D#uB duB duE is eard. $e conversation cannot be carried on sootlB and call dro' often a''ens. 7en interference e/ists in te networkB fro te result of traffic statisticB tere are soe caracteristic as followin!.
1.$ e r e a r e * e v e l " F * e v e l & i n t e r f e r e n c e b a n d i n $ C 6 e a s u r e e n t function B and te easureent value is ore tan 1. 2.Con!estion rate is co'arativel i! 0As tere is interference in S#CC6 cannelB iediate assi!nent or $C6 assi!nent will fail. 3. $e call dro' rate is i!er tan oter cells. ". $e andover success rate is low. &. $rou! #rive $estB it is found tat %. it is difficult to andover . ;. $e R/ level is i!B but te 4ualit is bad. (. $rou! tracin! te Abis interface si!nalin! wit si!nalin ! a n a l > e r 0MA15G-125&B it is found tat te bit error rate is i!er tan oter cells
Interference Sources 1. Classification of Interference Sources $e interference sources of obile counication ssteGnoise are ainl classes as follows
1..1 -atural -oise • • •
Atos'ere noise ?ala/ noise Solar noise 04uiet 'eriod
1.. Man'/a%e -oise Interference of i!nition sstes of veicles or oter en!ines Interference of electronic counication ssteH Interference of 'ower line Interference of scientific researcB edical and ouseold a''liancesH Researc data of I$$B Aerica on te above noiseGinterference is sown as follows
In te fi!ureB $a denotes te noise te'eratureB a denotes e4uivalent noise factorB and te relation between te two is as follows Fa
0o% #a/#o
7ereinB $o2,5 5
-.ro te researc data of I$$B it can be viewed tat te atos'ere noise and solar n o i s e i s c o ' a r a t i v e l l o w i n 35F1555M6>B wic can be i!nored. A n d a b o v e 1 5 5 M 6 > B a s t e r a d i o n o i s e o f ! a l a / i s l o w e r t a n t e t e r a l n o i s e o f t ' i c a l receiverH te interference can be i!nored as well. $usB natural noises 0atos'ere nois eB !a la / nois e and solar noise are unnecessaril considered for te obile sstes above "&5M6>B (55M6>B ,55M6>B 1(55M6> and 2555M6> J3K. $e affection of suns'ot fasti!iu on obile counication is te'oraril unknownB but scientists b e l i e v e t a t s u n s ' o t f a s t i ! i u a s ! r e a t a f f e c t i o n o n t e e l e c t r i c ' o w e r a n d co unication.Accordin! to te researc of National 9ureau of Standards 0N9SB it is found tat te an=ade noise is one of te ain interference sources. Aon! tose an=ade interferenceGnoise sourcesB certain interference is uncontrollableB suc as i!nitioninterference of veicle en!ineB electric 'ower inte rf er en ce an d in du str ia l el ec tr ic e4ui'ent interference. 6oweverB certain interferenceB suc as interference between counication e4ui'ent and internal network interferenceB wic can be overcoe b reasonableB network 'lannin! and sste o'tii>ation. $e latter is ain researc field of tis docuent.
1.! Main Interference Sources Affectin0 Mobile Co//unication In obile counication ssteB wen 9$S receives te s i ! n a l s f r o t e M S co'arativel far awaB it will encounter interference fro te abient counicatione4ui'entBand 9$S or MS of te sae sste J3K B as sown in te fi!ure below
i0ure 1. Sceatic dia!ra of obile counication interference $e ain interference of tis 'art is as follows 6ardware fault $R: fault if te 'erforance of $R: is reduced due to anufacture cause or a''licationB wic will cause self=e/citation of $R: a'lification circuit resultin!in interference. C#< or divider fault as active a'lifier as been ado'ted for te divider and divider odule of C#
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s'urious eission is co'arativel lar!e. $us i t e a s i l c a u s e s interference to te 9$S. Analo! 9$S $e fre4uenc band used b te analo! obile 9$S overla's witte ?SM fre4uenc band in certain se!ent. Counication e4ui'ent at sae fre4uen c b a n d A s t e t ' e s o f counication e4ui'ent are so anB soe anufacturers abe ado't tefre4uenc band but doesnt co'l wit te current counication standards.As te ?SM fre4uenc band is occu'ied b te e4ui'entsB interference will becaused witin te ?SM sste covera!e area
Discovery of Interference $o solve te interference 'roble and i'rove te conversation 4ualitB find out teinterference firstB and te n use
'ro'er eans for locatin! te interferenceB and at lasteliinatin! or reducin! interference.$e etods available for discoverin! te interference in ?SM sste are as followsOMC traffic easureentB OMC alarB #rive $est and subscriber co'laintB etc. Aste 'uissant toolsB s'ecial test e4ui'ent suc as si!nalin! anal>er and s'ectruanal>er are coonl unused in tis sta!e. 1." Discoverin0 Interference via OMC Traffic Measure/ent After a network on srviceB followin! traffic easureent tasks sould be re!istered todiscover te 'robles in tie $C6 easureen functiontB S#CC6 easureentfunction and andover easureent function. After task re!istrationB ceck te trafficst at us of va ri ou s ce ll sB a nd ov er an d tra ffic ea sur ee nt ind ice s r ela ted to cel l4ualit to discover te cells wit 'otential interference.7at needs to be entioned is tat onl te e/istence of te 'otential interferencec a n b e j u d ! e d a c c o r d i n ! to te ceckin! results. $o find out weter tere isinterference actuallB or tere are oter 'roblesB location and analsis is needed. 1. Discoverin0 potential interference via traffic statistics result Ceck te DAvera!e $C6 bus tie 0secondE in $C6 easureent function of eaccellB te reason is tat tis inde/ can sow te $C6 ean occu'ied tie 0sEB wic isusuall called D$C6 ean oldin! tieE in te 9SC of oter anufacturerEB witin tee as ur e en t 'e ri od . If it is foun d tat te Avera !e $C6 b us tie 0sec ond of certain cell is
co'arativel sort 0suc as less tan 15sB ten abe tere is stron!interference in te cellB causin! tat andoverGcall dro' a''ens due to bad 4ualitafter $C6 cannel occu'ied to MS.CertainlB if ardware fault occurs in certain $R: 0non=9CC6 or non=S#CC6 carrierof a cellB te case entioned above will also a''ear. . Discoverin0 interference via han%over %ata $e andover easureent data reflects te obilit of te subscribers witin tec e l l u n d e r e a s u r e e n t . ? e n e r a l l B w e c a n d i v i d e t e a n d o v e r d a t a i n t o t w o cate!ories for analsisB intra=cell andover and inter=cell andover.
Inter=cell andover $ere are an reasons of MS tri!!erin! andover $e andover easureentindices ainl used for jud!in! weter tere is interference are as follows ties of atte't to initiate andover 0downlink 4ualitB ties of atte't to initiate andover 0u'link 4ualitB ties of receivin! 4ualit level 05F; wen initiatin! andover 0u'linkand avera!e receivin! 4ualit wen initiatin! andover 0u'link.7en certain cell initiates andoverB if te avera!e receivin! 4ualit 0u'link is L "0tis is true wen tere is no fre4uenc o''in!B if tere isB it sould be L &B and te e a n r e c e i v i n ! l e v e l i s L 2&0=(&d9B ten it is 'ossibl caused b u ' l i n k interference.7en certain cell initiates andoverB if te ties of receivin! 4ualit level above & isore tan tat below "B ten tere a be u'link interference as well.If t e ti e s of ce rt ai n ce ll at te ' ts to in it ia te andover 0u'linkGdownlink 4ualit is
ore tan 15 of total andover atte't tiesB ten tere a be interference in tecell. $e two indices are all related to 4ualit
andover tresold and interferenceandover tresold witin te cell 'araeters.
Intra=cell andover or intra=cell andoverB tere is also easureent ites suc as intra=cell andover re4uest ties 0u'linkGdownlink 4ualit and te interference situation. If te intra=cellandover is caused b u'linkGdownlink 4ualitB and te 'ro'ortion taken u' b totalintra=cell andover ties aon! te total inter=cell andover ties is co'arativeli!er tan tat of otersB ten tere a be interference in te cell.$e andover easureent inde/ is closel related to te settin! of cell 'araeters.$ e r e d u c i n ! o f a n d o v e r j u d ! e n t t r e s o l d a n d ) G N d u r a t i o n c a n a k e t e andover ore sensitiveB and cause ore andovers. And on te contrarB andover t i e s w i l l b e r e d u c e d . $ o o f e w a n d o v e r t i e s a b e n o ! o o d t o t e n e t w o r k 'erforance at wilesB and affect te andover success rate directl. 6oweverB too a n a n d o v e r i s n o ! o o d e i t e r . A s f o r t e ar d an do ve r a tt ri bu te of ?S MB a n d o v e r i s a l s o t e ain cause of call dro'. Accordin! to te online data easureentB te 'ro'ortion tat one andover 'er c o n v e r s a t i o n w i l l b e co'arativel reasonable. !. Discoverin0 potential interference via call %rop in%e2 Call dro' is one of te network faults un=acce'table for t e s u b s c r i b e r s . $ e easureent indices related to call dro' are as follows S#CC6G$C6 call dro' tiesBwireless link broken ties wen S#CC6G$C6 occu'ied 0connection failed and eanu'linkGdownlink 4ualit in case of S#CC6G$C6 call dro'.If te call dro' ties of certain cell is rater i!er te te oter wit sae traffic loadBan d t e a in ca use of call dro' is ownin! to conne ction fau ltB ten it is 'ossibl caused b interference.If te avera!e receivin! level durin! call dro' is co'arativel i! 0 L 2&B wile tea v e r a ! e r e c e i v i n ! 4 u a l i t l e v e l i s L %B ten te cell sould be listed into teinterference source. ". Discoverin0 potential interference via interference ban% 9$S will utili>e an idle $S in a frae to scan te u'link fre4uencies of te fre4uenciesused b $R:B and ten ake easu ree nt t o t e le vel
& in te rf er en ce ba nd . $ e default settin! of interference bands in 9SC of 6uawei is as follows 115B 15&B ,(B ,5B(; and (& 0unit =d9B corres'ondin! to te followin! interference bands in trafficeasureent Table .1 Interference bandI
Co'ared wit oter easureent indicesB te easureent inde/ of interferenceband can refle ct t e cel l inte rfer ence situa tion ore directlB but it can onl reflectweter tere is interference in te u'link.If te values of interference band " and interference band & are co'arativel lar!e0 L 1B tenB tere a be co=fre4uenc interference in te cell. If te easureentvalues a inl distr ibute in in terfe rence band 1 and in te rf er en ce ba nd 2B t en t e 'ossibilit of interference will be sall. 6oweverB if tere is co'arativel i! valuein band 3B ten attention sould be 'aid to tis
Note As 6uaweis easureent etod of interference band is based on cellB tev a l u e o f i n t e r f e r e n c e b a n d o f c e r t a i n $ R : t a t s u f f e r s s e r i o u s c o = f r e 4 u e n c interference will be co'arativel sall in lar!e site t'e 0S(G(G(. $e reason is tattis value as been avera!ed b te values of oter seven $R: witout interference.$usB te values cannot reflect te actual interference condition. 1.) OMC Alar/ an% Subscriber Co/plaint OMC alar subsste can re'ort te ardware fault of 9$S side. 9efore startin! tolocate te interference sourceB analsis ust be 'erfored to te
alar inforationfirst. 9efore i'leentation of an o'tii>ation worksB it is wise to eliinate ardwarefault first.7at needs to be entioned is tat te interferenceB weter fro MS or oter 9$SBcannot be jud!ed via te alar inforation of alar subsste.Su bscriber co'laint is also i'ortant cle w f or fin din ! te 'o ten tia l int erf ere nce . Inforation wic sould be collected fro user co'laint includes MS nuberB MSodelB called nuber and fault 'enoenon of callin! side and fault 'enoenon of called side and 'articular fault locationB etc. If te alar inforation is ore detailedBit will be ore easil to find out te network 'robles.$e descri'tion of subscriber co'laint is co'ar a t i v e l f u > > . 6 o w e v e r B i t i s reasonable if te subscriber cannot tell ou were te interference isB te reason ist a t t e d o n t k n o w u c a b o u t t e c e l l u l a r n e t w o r k a c t u a l l . 7 e n t e r e i s interference in te networkB te direct feelin!s of te subscriber a be eav noiseBbot 'arties or eiter 'art cannot ear eac oter clearlB call dro's and call cannotbe 'ut trou!B etc. $usB wen an subscribers witin te sae area co'lain tesae 'robleB ten work sould be done to ceck weter tere is interference inte area. 1.# Discoverin0 Interference via Drive Test # r i v e $ es t i s a e t o d t a t i s o s t c o o n l u s e d t o f i n d o u t ' r o b l e s . $ e sus'icion of interference !ained b te etods described aboveB naelB analsis of traffic easureent and subscriber co'laintB sould also be verified via drive test.Note tat te #rive $est can onl ceck te downlink interference. #urin! actuali'leentationB tere are two #rive $est etods available idle ode test ands'ecial ode test.
2&B subscribers can feel te discontinuous voiceBtat is to saB interference e/ists in tis section of i!wa 0@R easureent of AN$is inaccurate. Chapter $ocation an% Clearance of InterferenceSource $e ost i'ortant 'rocess durin! o'tii>ation is ow to locate te fault in tenetwork wic re4uires uc e/'erience. $e ab ov e se cti on on l re ve al s t at t e interference a e/ist in te networkB but te causes of interference var suc as co=fre4uenc or adjacent fre4uenc interference in te ssteB s'urious interference of i!='ower transittin! e4ui'ent aroundB te self=e/citation of te transitterB etc. .1 ,eco//en%e% 3roce%ures for $ocation an% Clearanceof Interference .1.1 Deter/ine Interference Cell accor%in0 to 4ey 3erfor/ance In%e2 543I6 $e sudden deterioration of suc indices as call dro' rateB andover success rateBtrafficB con!estion rateB interference band indicates tat interference e/ists in te cell.At t is ti e B c ec k t e lo ! of t e o'eration on te cells is re4uired. Ceck weter 9$S ardware is added or odifiedB and data is odified recentlB or weter teoccurrence of te interference is associated wit tese o'erations in ters of tie.I f n o d a t a o d i f i c a t i o n i s ' e r f o r e d i n t i s d u r a t i o n B i t c a n b e s u r e t a t t e interference coes fro te ardware or e/ternal of te network. It is recoendedt o c e c k t e a r d w a r e f i r s t B i f i n t e r f e r e n c e s t i l l e / i s t s a f t e r t e a r d wa r e f a u l t i s e/cludedB ten ceck weter e/ternal interference e/ists 0te etod for ceckin!e/ternal interferenceB 'lease refer to te ca'ter infra. .1. Chec Alar/ of OMC SoetiesB te i! call dro' rateB low andover success rate and i! con!estionrate a be relevant wit te e4ui'ent faultB ceck of OMC alar record will s'areuc tie s'ent in jud!ent and analsis. SiilarlB te association of alar recordwit te deterioration of tese indices in ters of tie is anal>ed ere.It sould be noted tat ost alars of OMC ai at te ardware fault of te suc as$R: no 'o we r ou t' ut B et c. o r ost 'oten tial fault in o'ti i>ati on suc as $R: or C#< receivin! 'erforance de!radationB self=e/citationB etc.B te alar inforationcannot be re'orted. 0Co'ared wit di!ital co'onentsB te analo! co'onents sucas icrowave and so on are ore difficult to detect
.1.! re7uency 3lannin0 Chec If one cell is doubted wit interferenceB ceck te fre4uenc 'lannin! of tis cell andcells around. irst ou sould be ver clear about te 9$S location distribution anda > i u t o f e a c c e l l B t e n a k e a d r a w i n ! o f te to'olo! a'B and ark te9CC6G$C6 fre4uenc and 9SIC. At te sae tieB ake a co'arison between te'lanned fre4uenc and actuall confi!ured fre4uenc in 9SC to ceck weter tereis discre'anc.?enerall ou can jud!e weter tere is co= fr e4 ue nc an d ad ja ce nt fr e4 ue nc interference accordin! to accurate to'olo! a' of fre4uenc 'lannin! .1." Chec 3ara/eter Settin0 of Cell Soe cell 'araeters ave i'act on te interference suc as CROB andover tresoldB andover jud!entGstatistics duration 0)GN c riteriaB and adjacent cellrelation.If CRO is set too lar!er tan te nei!bor cellsB MS is drawn in tis cell wit in idleode even te actual R/ level lower tan te cells aroundB so once CGI cannot beore tan te tresold 12d9 in case of conversationB interference will eer!e.If confi!uration of adjacent cell is oitted in adjacent cell r e la ti o nB M S w il l f a il t o a n d o v e r t o t e cell wit better si!nal level and 4ualitB tis will also lead tointerference. Sli!t interference a also occur in case of lar!e andover tresoldBa n d ) G N criteria as well as andover difficult between cells. 9ut i t i s f a r o r e dan!erous if te value is too sallB te fre4uent andover not onl increases te calldr o ' r a t e B b u t a l s o t e s s t e l o a d B e v e n l e a d s t o d i s a s t r o u s r e s u l t B i . e . B 9 S C bre akdown. .1.) Drive Test #rive $est is an effective wa to locate te interference. $e etod is te sae as'roble location in 3.3. $e difference is tat te cell wit interference is i!li!teddurin! te test wen locate te interference. .1.# Interference Clearance Adjustents sould be ade res'ectivel accordin! to te above location results. or detailsB 'lease refer to te tecnical cases. inall te effect of interference clearancewill be evaluated accordin! to -)IB and #rive $est result.$e s'ecific etods for interference location and clearance are described in
for of cases as followsB at te sae tie te case I# is 'rovided for te con ven ien ce of consultation. . $ocation an% Clearance of 8ar%ware ault 7en a certain cell is doubted wit interference trou! te abo ve an al s isB it is re4uired to ceck weter te 9$S first were te cell is located works norall or not. Ceck weter tere is antenna feeder alarB $R: alarB 9$S clock alar andso on reotelH ceck weter tere is antenna daa!eB water see'a!eB feeder 0includin! ju'er daa!eB water see'a!eB C#< faultB $R: faultB incorrect 9$S ju'er connectionB sste clock unlocked. ..1 Antenna 3erfor/ance De0ra%ation As one of te 'assive devicesB te 'ossibilit of antenna daa!e is ver littleB but tereal antenna daa!e or 'erforance de!radation will lead to 'oor counication4ualit.Case 5515;%1. ault %escription9 $ere are & 9$Ss for a certain network in a count confi!ured asS"G"G" and %G%G%B te 9$S t'e includes 9$S25 and 9$S35. $e interference band &i n $ C 6 e a s u r e e n t f u n c t i o n o f s o e c e l l s i s o v e r 1 & B a n d t e r e i s n o a l a r inforation in OMC ault location process 1 Re!ister te statistics task of interference band of 2" ours for te cell wit 'roblesB it is found tat interference band & ainl occurs in dali!tB and inte sall ours near iddle ni!tB te interference band value is alost 5. 2 After o'enin! te idle 9
& Observe te R:M test interface of C#< wit te s'ectru anal>er in 'eak our in te dali!tB it can be seen tat unstable stron! broadband interference andrise of back noise occur. % irst re'lace all b oards 0$R:B C#
..! :u/per Connector ault $e R si!nal of ?SM falls into te <6 si!nalB if loose contact e/ists in an sectionfr o $ R: B C#
It is found tat tou! interference s'ectru occursB but te interference si!nallevel is not too i! wen ceckin! wit s'ectru anal>er. 3 $e interference still e/ists after re'lacin! c ar ri er bo ar dB 'o we r a 'l if ic at io n b o a r d B ' o w e r b o a r d B a n d C # <. Subse4uentl te interference occurs anddisa''ears a lon! wit te o'erations of screwin! u' and screwin! off t e connector at te e/it of C#<. " It is found tat soe scra' s e/ist on te C#< out'ut con nector. Screw u' teconnector after blowin! off te scra'sB and since tenB interference never occurs.$is 'roble belon!s to te soft fault. $e scra's i n t e c o n n e c t o r w i l l b r i n ! u n co ns 'i cu ou s i nt er fe re nc eB so e/ ' erience is 4uite i'ortant ere. On te oter andB tis 'roble reinds us of te i'ortance of ceckin! te en!ineerin! 4ualitcarefull. .." Antenna Connecte% Inversely It is 4uite usuall tat te antenna is connected inverselB wic will lead to co'letedifference between te usin! fre4uenc and te 'lanned fre4uenc. It will also lead toco=fre4uenc and adjacent fre4uenc interferenceB call dro'B andover failureB etc. If te fre4uenc resources for o'erator is a fewB antenna connected inversel will affectte network 4ualit uc ore.Case551115( ault %escription9 te interference bands " an d & often occur in te tr a f f i c easureent after certain 9$S is on serviceB te inter=cell andover success rate isver low and te con!estion rate is u' to &. $ere is no alar in OMC. ault location process 1 Since te interference bands " and & occur alon! wit low andover successr a t e a n d c o n ! e s t i o n B i t i s d o u b t e d t a t t e i n t e r f e r e n c e c a u s e s t e a b o v e 'enoena. 2 Ceck te fre4uenc 'lannin! firstB no 'r oble is f o u n d . $ e e / t e r n a l i nt er fe re nc e b ec o es t e c i ef c on si de ra tion after te fre4uenc 'lannin!'roble is e/cluded. Can!e te ori!inal used fre4uenc , into te far= awaf r e 4 u e n c , " t o a v o i d e / t e r n a l i n t e r f e r e n c e B b u
t s i t u a t i o n s i t e s a e . Confiration ade wit te o'erators branc office indicates tat te 9$S is reote and witout an i!='ower radio e4ui'ent nearb. It looks as if tefre4uenc 'lannin! or e/ternal interference sould be e/cluded. 3 Since andover failure is involved at te sae tieB it is found tat andover f a i l u r e o c c u r s b e t w e e n c e l l s 1 a n d 3 a c c o r d i n ! t o t e r e ! i s t r a t i o n o f out!oin!Gincoin! cell andover 'erforance easureent. " $e con!estion analsis indicates tat $C6 assi!nent failure is usuall causedb u'link. After re!isterin! te traffic easureent of u'linkGdownlink balanceB itis found tat te easureent ite of u'linkGdownlink balance for cell 1 and cell3 focus on level 1 and 11. $is indicates tat severe ibalance occurs betweenu'link and downlink. & $e ibalance between u'link and downlinkB in cobination wit uc andover failure in cell 1 and 3 turn te doubt to te antenna and feeder wic a beconnected inversel. % On=site e/aination indicates tat te antennas of cell 1G2G3 becoe crossed'air wic causes te transitter antennas of cell 1 and 3 to sta in te saec e l l B w i l e t e r e c e i v e r a n t e n n a s o f t e c o n n e c t t o a n o t e r c e l l . $ e interference band and con!estion disa''ear and te andover is all ri!t after itis corrected.Case 555&23; ault %escription t e # r i v e $ es t f o r c e r t a i n n e t w o r k r e v e a l s t a t t e 9 C C 6 fre4uencies of several cells is different fro te desi!nB te adjacent cell relation isdisordered wit serious co=fre4uenc interference. MoreoverB wit andover successrate affectedB te conversation 4ualit is 'oorB and te call dro' rate is ver i!.On=site detection reveals tat te connections of antenna feeder sste in several9$Ss are disordered. Perif eac cell wit te test MSB it is found tat 3 sector cell of so e 9$ Ss ar e co nf i! ur ed correctl b ut rotated 125 clockwiseB and crossed 'a ir e/ists between two cells of soe 9$SsB causin! te $:GR: of two cells to cover tesae area in te sae direction.
ault location process 1 Make clear te fre4uenc of several cells accordin! to te net wo rki n! 'l an desi!nB and locate te erro wit te test MS on site. 2 $wo etods can be ado'ted to correct te connection error and ve ri f t eaccurac. 3 Metod 1 tere is one len!t fla! ever oter 1 on ;G( feedersB trou! wicte successive two len!t fla!s on ;G( feeders corres'ondin! to eac antenna ineac cel l at t e to wer t o' ca n be obser ved and re co rd ed . So t e in cr ea se or decrease of fla! can be jud!ed in case of cablin! of eac feeder fro te tower to t e e4 ui ' en t ro o B t en ceck tis fla! at te side of li!tnin! arrester of indoors antenna. $e len!t for eac feeder fro te tower to' to e4ui'entroo is basicall te saeB so te len!t fla!s at te two to' and at te side of li! tnin ! arre ster can be used to jud! e to wic cell does te feeder belon!.C o r r e c t t e c o n n e c t i o n a t t e l i ! t n i n ! a r r e s t e r o f t e a n t e n n a a f t e r c l e a r jud!ent is obtained. inall correct te incorrect fla!. " Metod 2 te feeder fla! of soe 9$Ss a be b l u r r d u e t o s c r a t c i n constructionB or no etod is available to jud!e weter te feeder connection iscorrect. In tis caseB #rive $est can be ado'ted for jud!ent. $e jud!ent for $:GR: feeder of one cell is eas and weter te connection is correct can beknown fro te results of #rive $est. 9ut R:# transits no si!nalB it is unable toknow weter te antenna feeder is correctl connected trou! te #rive $est.At tis tieB switc off te 6)A of all carriers in te cellB and connect R:# feeder to $:GR: out'ut of te C#< were te ain 9CC6 of cell is locatedB ten switcon te 6)A for #rive $est. If correct fre4uenc is received in te s'ecified cellBte co nnec tion of R:# feed er in tis cell is corre ctB ot e rwise B it is in co rr ec t. ro te #rive $estB te cell to wic te R:# feeder belon!s can be obtained. Correct te connection at te li!tnin! arrester of antenna and attac new fla!a!ain after akin! a clear jud!ent of all feeders. & Perification wit #rive $est is re4uired after correction. ..) Incorrect :u/per Connection of ;TS
$ere are an ju'ers fro 9$S $R: to te antennaB te confusion of wic willlead to i! call dro' rate.Case 551&353. ault %escription a newl constructed 9$S is of S333 t'e and dual = C # < confi!uration wit te version as 5&.5&2,. $e subscriber co'lains tat it is difficultto ake MOC or M$C in te areas covered b tis 9$S since te on service. In tetraffic easureentB te S#CC6 call dro' rate of one cell in tis 9$S is u' to &5.$ere is no alar in OMC ault location process 1 $e causes for te above 'enoenon a include interferenceB 9SC dataerrorB and ardware fault. $e location will focus on tese 3 as'ects. 2 $e dial test carried out b aintenance en!ineer of te o'erator indicates tattis fault 'enoenon occurs in cell 3. $e DtickE alwas occurs in te MS andte MS returns to te idle ode wen it initiates a callB oreoverB onl one in four and five ties of callin! is successful. 3 ro te traffic easureentB it is found tat S#CC6 call dro' rate of tis cell isver i!B i.e.B &5B and oreoverB all causes are radio link loss connections0error indication. 9ut $C6 assi!nent is nor a l B s o i t c a n b e j u d ! e d t a t S#CC6 call dro' is te reason w te MS is difficult to ake MOCor M$C. " urter analsis of te traffic easureent indicates tat te interference bando f t i s c e l l i s n o r a l B s o t e i ' a c t o f i n t e r f e r e n c e o n S # c a l l d r o ' c a n b e e / cl ud e d. Co n si d er i n! t a t t is 9$ S i s a newl on se rviceB t e ceck sould base on data and 9$S ardware. & A careful ceck of te data of tis 9$S includin! ardwa re data and ne wo rk'lannin! data sows tat tere is no error. % It is found tat tere are 3 carriers in 3 cells of ti s 9 $ S w i t d u a l = C # < c on fi !u ra ti on B t e i n' ut of two carriersB wic sould be connected to tecobiner in'ut end of C#
A s t e c o r e c o ' o n e n t o f 9 $ S B t e f a u l t o f $ R : w i l l l e a d t o t e i n c r e a s e o f interferenceB decrease of covera!eB access difficultB etc.Case 5511&1, ault %escription9 te subscriber re'orts tat te conversation 4ualit in te areanear certain 9$S in certain cit is 'oor and wit call dro'. ro te cell easureentfunction re'ortB it can be found tat te avera!e id le $C6 nu b er of in te rf er en ce band 1 is 11."" wen 9$S cell 2 is busH tat of interference band 2 is 32.2;H tat of interference band 3 and " is 5 all te tieH tat of interference band & is ;.2. At tesae tie it is found tat te nuber of $C6 assi!nent failure of tis cell is u' to&5B and te call dro' rate is about 15. Since tis site is on service for two earsB andrunnin! alwas stabl . $e 9$S t'e is 9$S250M,55 wit te confi!uration of S%G%G%B and te first " $R:s of eac cell are connected to te D"=in=1E cobiner viari!id R cableB wile te last 2 are conn ected to te D2=i n=1E cobi ner. $e du'l e/ $MA is installed in te antenna and feeder sste. No alar inforation as been!enerated recentl
ault location process 1 On=site dial test and analsis of traffic easureent indicate tat tis is aninterfere nce case. ?enerall B te nuber of u'link $C6B $C6 con!estion andcall dro' rate will increase wen interference e/ists. 9 u t f u r t e r l o c a t i o n i s necessar to deterine weter it is e/ternal interference. 2 or e/ternal interferenceB te interference source can be located trou! tesi!nal stren!t witin u'link band wit s'ectru anal>er. 3 $e cause of internal interference is basicall te sae wit tat of adjacentfre4uenc interference. 9ut te followin! will also lead to internal interferencete 'erf oran ce de!r adati on of R de vices suc as a nte nna B $owe r Mo unt A'lifierB li!tnin! arresterB cobinerGdividerB $R: boardB and so onB as well ast e
loose contact of R cable. $is 'roble can be solved b r e ' l a c i n ! corres'ondin! boards and devices. " $e co=fre4uencGadjacent fre4uenc interference can be e/cluded because tefre4uenc as alread been rationall 'laned b te o'tii>ation en!ineers. $ee/ternal interference is sus'ected. $en carr out a test for te si!nal stren!t of wo le u' li nk ba nd in t e ai r un de r te tower wit s'ectru anal>erB and nostable si!nal of ore tan = 155d9 is found. $is indicates tat te interference is!enerated witin te network. & Ceck te connection of antenna and feederB no suc ant e n n a c o n n e c t e d reversel or loose contacted. % $en re'lace te du'le/ $MA of cell 2 wit noral $ower Mount A'lifierB teinterference band as no can!eB it indicates tat te interference is not causedb $ower Mount A'lifier. ; Re'lace related devices in cell 2 wit noral S)*B cobiner and R cableB teinterference band as no can!eB too. So it can be sure tat te interference isnot caused b te above devices. So te location focuses on te antenna andsuc boa rd s a s $R: B )
Re'lace $R:1%B and $R:1; res'ectivel and observe te traffic easureent.$e traffic easureent obtained soe tie after $R:1; is re'laced indicatestat te interference band 3B "B and & of cell 3 becoe 5B te con!estion rate andcall dro ' ra te 5B too . It can be kno wn ta t te interference is caused b self=e/citation of $R:1; internal R circuit and 'erforance de!radation of devices. 15 No call dro' occurs and te voice is distinct wen 'erforin! fre4uenc lockin!dial test on eac cells 9CC6 fre4uenc.Case 555&,"5 ault %escription9 con!estion rate of 2 cells in 9$S 0S%G%G%2 in certain count isusuall u' to 15. $e careful view of traffic easureent 0$C 6 e asu re e nt function reveals tat about ; $C6s in tis cell often sta in interference band "F&B sote interference abe e/ist. ault location process
1 $o locate te fre4uenc wit interferenceB re!ister te traffic easureent of tecell 0a 'eriod of 1& inutes first. 9lock te carriers one b one. $e nuber of $C6 in inter feren ce ba nd " F& be coes 5 we n bl oc ki n! ca rr ie r ( 0f re 4u en c 2(B indicatin! tat te interference is fro te fre4uenc. 2 Connect te antenna and feeder of cell 2 wit s'ectru anal>erB set te centralfre4uenc is fre4uenc 2( 0(,&.%M6Q. No e/ternal interference e/ists trou!observin! te level value. So te interference a coe fro te e4ui'ent. 3 Intercan!e te carrier board wit interference in cell 2 wit noral carrier boardin cell 3B ten observe te traffic easureent. It is found tat te nuber of idle$C6 in interference band & of cell 3 becoes 5B wile tat in cell 2 becoes 5Btoo. So it can be sure tat te carrier board fault leads to te interference. "
re'ortsinterference band &. $is el's furter locate tat te ca rr ie r bo ar d is t einterference source. & $e 'roble is solved after tis fault carrier board is re'laced.$ e self= e/citation of carrier board or te invalidation of devices will brin! stron!interference for te receivin! device. So lar!e aount of ass i! ne nt fa ult le ads to i! con!estion rate of te cell.Case 555;%"% ault %escription9 $e interference of a cell alwas falls into interference band " and& trou! te analsis of traffic easureent of certain networkB and ca rrie r 2( is under te interference via tracin! and analsis. ault location process $e interference source usuall coes fro radio cou nication sste asfollowin!. 1 Carr out a test for te electroa!netic environent of te 9$S wit s'ectruanal>er. Set te start scan fre4uenc to (,&M6> and e nd s ca n f re 4u en c t o ( , % M 6 > f o r t e s ' e c t r u anal>erB ten carr out te test in different tiese!ents. No continuous interference si!nal falls into tis bandB tis indicatestat te interference abe coe fro witin te sste and a be caused bte fault of certain 'art in te e4ui'ent. 2 Re'lace te carrier board wit interference and 'ower a'lifier board to anoter cell at te sae tieB and re!ister te traffic easureent of & inutes. $einterference disa''ears fro ori!inal cell and occurs in new cellB indicatin! tatte in te rf er en ce a be cause d b se lf=e/ citat ion of carri er boar d o r ' ower a'lifier board. 3 Mark te carrier board and 'ower a'lifier board res'ectivelB and re'lace teto te two carriers free fro interference. $en re!ister te traffic easureentof & inu tes fo r tra cin! and obser vatio nB it can b e fo un d t at t e in te rf er en ce occurs to fre4uenc were te carrier board wit ark is located.$is 'roble is also caused b $R: self=e/citation. ..= Cloc >nlocin0 $e clock for te di!ital sste siilar to ?SM is just like te nervous sste of tee4ui'e ntB so te clock unlo ckin! of 9 $S will cause t e 9$ S to D! o a dE . On on e andB te lar!e deviation of 9$S clock will brin! difficult for te MS to be locked inte fre4uenc of te 9$SB and lead to MS andover failure or unavailabilit of residin!in te cell of te 9$S. On te
oter andB it will cause te 9$S to be unable to decodet e s i ! n a l c o r r e c t l . I t s o u l d b e n o t e d t a t t e c l o c k o u t = o f = l o c k w i l l n o t b r i n ! interferenceB but te increase of error code in transission will lead to te decrease of ault %escription9 $e custoer ado'ts transission tieslot ulti'le/er to save tet r a n s i s s i o n r e s o u r c e . A f t e r b e i n ! u s e d f o r s o e t i e B t e s l o t u l t i ' l e / e r i s da a!ed because of te water see'a!e into te e4ui'ent roo. After it is re'lacedBa l l 9 $ S 1 3 M c l o c k s u n d e r t e c o b i n e r a r e o u t of=lockB and interru'tion andcaco'on occur durin! conversation. $e inter=9$S andover is unavailable andcall dr o' ra te rises u'. Man alars of 13M clock out=of=clock occur in OMC alarconsole. $e 9$S is in free oscillation status trou! 4uer of te $M< status of 9$S. ault location process 1 ?enerall 9$S clock out=of=lock is caused b te de!radation of transission4ualit and rise of 9@R. $e clock out=of=lock of suc a lar!e confi!uration 9$SBaccordin! to te forer e/'erience and te 'enoenon of te 'robleB it is nottra ns is si on e4 ui ' en t on l but te sarin! e4ui'ent relevant wit tese9$Ss. Since tese 9$Ss are under different odule s of te 9SCB in ad ditionB tese odules also su''ort te 9$S of oter cities 0were no clock out=of=lock isfoundB so 9SC clock 'roble can be e/cluded. So e'asis sould be laid onte 'sical link fro te 9SC to inter=9$S Abis interface. 2 $e ceck of alar bo/ sows no transission alar. 3 Ceck te transission of eac 9$S and testB $e 9@R is not too i!. " Ceck 9SC clockB te clock is in noral tracin! status. & Ceck of ## sows tat !roundin! is !ood and ## cobines !roundin! witte 9SC. % #isconnect te 9$S under te slot ulti'le/erB and connect it wi t te 9SCdirectl via te ju'erB ski''in! te slot ulti'le/er. It is
observed tat te 9$Sclock can!es fro 'ull=in status to tracin! status. After reovin! te ju'er andr estorin! te ori!inal connectionB te 9$S clo ck is ou t of loc k. So te fau lt is relevant wit te slot ulti'le/er. ; Ceck of te 'ro!ra in slot ulti'le/er sows tat all 'orts are corre c t l defined. ( Ceck of !roundin! of slot ulti'le/er sows tat te 'ower !rou ndin ! is all ri!tB but te 'rotection !roundin! is not connected. All 9$S clocks can trace teu''er=level clock norall after con ne ctin ! te 'ro tec tio n !ro un din !B so te 'roble is solved..$e diversit of transission connection fro te 9SC to te 9$S will easil lead to9$S fault because of te 'roble of certain 'rocess in te connection. #etailed u n d e r s t a n d i n ! o f t e n e t w o r k i s 4 u i t e n e c e s s a r f or solvin! te faultB and fault'enoenon can be used to j u d ! e t e ' o s s i b l e c a u s e s . @ s ' e c i a l l t e ' o o r ! r o u n d i n ! or contact will !enerate 'otential difference wic will le a d t o t e de!radation of transission 4ualit and affect te stable runnin! of overall network. ..? Su//ary $e fault of an one of te $R:B C#in! te traffic easureent data. Certainl t e ad o'ti on of s'ectru anal>er will el' locate te 'roble faster. In te case tat interferenceoccurs suddenl in soe cells durin! te runnin! of network data to wic no dataodification is adeB e'asis sould be laid on te clearance of ardware fault
$e above interference related to te 9$SB is ainl c a u s e d b t i r d o r d e r interodulationB belon!s to te u'link interference and will be directl reflected in teinterference band. .! Intra'networ Interference ?SM intra=network interference ainl coes fro co= c a nn el Ga dj ace nt c an ne li n t e r f e r e c e s . I t i s u n a v o i d a b l e w e n CGIT12d9 or CGIaT=%d9. $e ado'tion of a!!ressive fre4uenc reuse will also increase te 'robabilit of interference. .!.1 Co'channel Interference Since fre4uenc reuse in te ?SM is unavoidableB co=cannel in te rf ere nce wi ll beeasil caused wen te reuse distance between two cells usin! te sae fre4uencis to o sa ll co ' ar ed wit t e ce ll radius. $e fre4uenc reuse in an casesBaccordin! to te e/'erienceB sould be avoided
or AF# 9$Ss sown in te above fi!ureB su''ose tat fre4uenc N is assi!ned for cell A=3B ten fre4uenc N cannot be assi!ned to A1B A2B 91B 92B 93B C1B C2B C3B #1B#2B and #3H fre4uenc NU1 cannot be ass i!n ed to A1B A2 B A3B 91B C2B #1B an d #2 0witout fre4uenc o''in!.$e case of co=cannel interference is scarceB tere are onl one earlier case ando n e c a s e i n l a b o r a t o r f o r r e f e r e n c e b e s i d e s t e
a b o v e c a s e o f c o = c a n n e l interference tat te antenna is connected inversel. ault pheno/enon9 $e co=cannel interference of 6uawei earl 2.5 9$S 0O2 incertain area leads to i! call dro' rate and 'oor voice 4ualit. Serious interru'tionwit occa siona l str on! n oise 0wi>> in ! ener al o ccur s. It is after te 9$Ss noralrunnin! for a certain tie tat te call dro' occurs. *ocated in a little town 0#u cito n t e b o r d e r o f t e c i t B t e 9 $ S i s s u r r o u n d e d b t e 9 $ S s o f t e o t e r anufacturer. ault location process 1 $e fre4uencies assi!ned for te 9$S are %"B and ,2 0%" is of 9CC6 fre4uenc. 2 In te o'tii>in! testB te receivin! 4 u a l it 04 u a li t le ve l i s l e ss t a n 3 i scontinuousl !ood as te downlink si!nal level is =,&d9 in te direction awafro 6uan!!an! and #u Cit. In te direction fro #u Cit to 6uan!!an!B terec eiv in ! 4ua li t is also !ood wen te receivin! level is ore tan =;5d9. $ e n o v e f o r w a r d u n t i l t o t e ' l a c e w e r e $ A & B t e receivin! 4ualit issoeties !oodB and soeties ore tan & in about 1 inute wen tereceivin! level is about =;&d9. And network=dro' occurs fre4uentl wen Idle=ode test is ade at tis 'lace. It is sus'ected tat downlink interference ae/ist on 9CC6 fre4uenc. 3 Carr out continuous conversation test wit one test MS and scan test for %"Vfre4uenc wit anoter MS. $e test carried out a!ain in te section fro #u Citto 6uan!!an! reveals tat te si!nal stren!t of %"V fre4uenc is alread lesstan =155d9 near te 6uan!!an!B and call dro' alread ad occured. 9ut tesi!nal stren!t of %"V fre4uenc rises u' to =% &d 9 an d di sa '' ea rs af te r a duration of 155 seconds wen enterin! te downtown area of 6uan!!an!. So itcan be jud!ed tat te co= cannel interference a be fro te $C6 fre4uencof cell nearb. "
Carr out scan test for tis fre4uenc after arrivin! at te otelB te si!nal levelstill reains i!B but te conversation is not i'leented on tis fre4uenc. $ene/t daB carr out desi!nated scan test at te 'lace wit te stron!est si!nal of tis fre4uenc in te street of 6uan!!an!B and test in Idle ode wit anoter testM S . r o t e s s t e e s s a ! e B i t c a n b e confired tat %"V fre4uenc isa s s i ! n e d t o t e $ C 6 i n 6 ? 5 ( c e l l w i t 9 C C 6 f r e 4 u e n c " & B a n d t e conversation is actuall establised once on %"V fre4uenc in ulti'le ties of conversation tests. & $e interference disa''ears after te a''lication is ade to te custoer toodif te fre4uenc. At te sae tieB te custoer sould adjust te adjacentcell relation of 'eer e4ui'ent. % Carr out test a!ain at te 'lace were te ori!inal co=cannel in te rf ere nce e/ists after te fre4uenc is odifiedB te call dro' and network dro' disa''earBand conversation 4ualit R/ualT3. It indicates tat te 'roble of co=cannelinterference 0downlink is solved.$e ?SM is a du'le/ ssteB so te interface a occur on bot te u'link anddownlink fre4uencies. Current #rive $est tools are unable to easure te co=cannelinterference directlB te e4ui'ent suc as SACOB and AN$ wit so=called CGI testfunction actuall test te CGA. An d in additionB te #rive $est e4ui'ent can onleasure te downlink fre4uenc and notin! for te u'link fre4uenc.$e co=cannel interference in downlink fre4uenc can be confired b usin! current#rive $est e4ui'ent to easure it indirectl. irstB lock te test MS in te cell of teservice area to carr out #rive $est of 2F3 ours in continuous conversation ode. If t e r e c e i v i n ! s i ! n a l in soe areas is a relativel i! 0e.!.B =(&d9 wile t e receivin! 4ualit is ver low 0e.!.B R/ualW"B it is 4uite 'o ss ib le t at co =c a nn el interference e/ists in tis cannel.$e interference of u'link can be jud!ed wit te el' of interference band statisticsdata in traffic easureentCase 555(11, ault pheno/enon9 It is found in te trainin! e4ui'ent roo soe da it is ardfo r te MS to access te network in 9$S35 under 9SC2. @ven it accesses ten e t w o r k n a r r o w l B i t w i l l d r o ' s o o n . $ e s t M S s o w s t a t t e s i ! n a l e / i s t s interittentl and te receivin! level is ver i! 0about =&5d9. ault location process
1 $e correctness of te data confi!ured b te trainees cannot be ensured in tetrainin! e4ui'ent roo. So load standard data 0wic is tested to ensure tatcall can be connected for 9SC2B te fault still e/istsB so te data 'roble can bee/cluded. 2 or te fault 'enoenonB it is 4uite 'ossible tat fault occurs in te carrier board. $e fault still e/ists after re'lacin! te $R:. 3 Ceck eac 'rocess related to te voice for te 9$ S $M
back'lane cableB etc. No 'roble is foundB so te 9$S is all ri!t. " $en focus is turned to te 9SC. a 9$S25 instead of 9$S35 and can!e tedata into 9$S25 0in tis waB overall ceck of 9SC can be 'erfored.And tecall is set u' easil B so te 9SC is all ri!t. & At tis tieB it sees tat tere is no wa outB but restore te 9$S35B oweverBte MS can call a!ain after 'ower=on loadin!. % It sees tat te 'roble is solved but te cause is still not located. Carefulconsideration fro te be!innin! to end reveals tat all data of 9SC2 and 9$S35are not odifiedB but 9$S25 is switced off durin! 9$S35 rollback. $ink aboutte 'enoenon of te test MS te si!nal e/ists interittentl and te receivin!level is ver i! 0about =&5d9B it is 'ossible tat 9$S25 works interference on9$S35X ; Since 9$S25 is in 9SC1B ceck te data of 9SC1. It is found tat te fre4uencof 9$S25 is set to be te sae wit tat of 9$S35. And te 9SC2 data 09$S35Bconfi !ur ed b te train eeB is lo aded in 9 SC1 after it is c an !e d in to 9$ S2 5B leadin! to te sae fre4uenc of 9$S25 and 9$S35. $e 9$S35 is connectedwit te attenuatorB and te si!nal is far weaker tan tat of 9$S25B so te MScannot access te 9$S35B wile can
access te 9$S25 . In tis waB ou tend totink tat it is te fault of 9$S35B but te trut is idden erein. ( $e 'roble is solved after te fre4uenc of 9$S35 is odified. .!. A%+acent'channel Interference or te cells to wic te adjacent cannel cannot be allocatedB 'lease refer to tesection su'ra.Case 5553"&1ault descri'tion te custoer re'orts tat te call dro ' often occurs in te office durin! o'tii>ation of a certain area. $e traffic statistic data and #rive $est data arenoralB $e 9$S distribution and to'olo! a' of fre4uenc 'lannin! are sown asfollows
In te fi!ureB red stands for 9CC6 fre4uenciesB wile black for $C6 fre4uencies. ault location process 1 $ o r o u ! t e s t r e v e a l s t a t t e l e v e l o f c a n n e l 1 12 i s u ' t o = ; 3 d 9 i n t e 'osition of call dro'. irst we tink te test is incorrectB but several tests indicatestat cannel 112 e/ists fro 9$S A to 9B and te level of w ic is even u' to=;5d9 at soe 'laces. 7en te MS occu'ies te cannel 111B call dro'occurs due to interference of cannel 112. 2 $est MS indicats tat cannel 112 is 9CC6 cannel in #3 cell b distin!uisin!C?I. 3 Survein! in 9$S # reveals tat antenna of #3 cell is installed on a 'latfor atte to' of te buildin!B wile ( awa tere is one ouse in !lass structure wicis " lower tan te 'latfor. $estin! near te antenna. $e transittin! si!nalof an te nn a is ab ou t =2 %d 9 B wi le te stren!t of test si!nal near te !lass isune/'ectedl u' to = 1"d9. $e si!nal b co'lete reflection of !lass and leadsto overla' Bten cause interference and call dro'. " It is recoended tat te custoer sould can!e te installation 'osition of te an tenna.$o eet te eer!enc e/can!e fre4uenc 111 of 9$S A witfre4uenc 11"H increase te downtilt an!le of an te nn a in A3 ce ll H ad ju st t e direction an!le of fre4uenc 113 in C1 cell to avoid te interference of fre4uenc11" after te e/can!e. & $e test is all ri!t after te odification. re4uenc 113 of 9$S C will work nointerference for fre4uenc 11"B and te call dro' disa''ears.Case 555"53"ault 'enoenon $e call dro' ratio is universall i! and even u' to about 1&in bus our after several 9$Ss are cut over. And it is difficult for te call to be set u'durin! on=site test. $ere is no alar essa!e in OMC sste ault location process 1 All 9$Ss are connected to te sae 9SCB and call dro' occurs after cutover of new 9$Ss.
2 $e transission 4ualit is !oodB and $R: test is carried out for te above 9$Swit call dro' and tis indicates tat eac $R: is all ri!t. No fault is found bceckin! te data and carrin! out te test for 329I@ 'ort corres'ondin! to te9$Ss. ro te above analsisB te $R: faultB 9SC ardware faultB A interfacecircuit fault and transission fault can be e/cluded. 3 Analsis of traffic easureent result reveals tat serious interference occurs ineac cell of te above sever al 9$S . Most cells ave e as ur e en t va lu es in interference band " and &B and te nuber of cannels fallin! into interferenceband & in several cells is u' to ;. So it is sure tat te interference in te aboveseveral cells is 4uite serious. " It is found tat tere are an adjacent cannels and te fre4uenc 'lannin! isirrational after ceckin! te fre4uenc confi!uration of above 9$Ss and teadjacent cells. @s'eciallB te area were te above 9$Ss are locatedB is newladdedB and interference e/ists aon! te. And te also ave interference inbetween te and te surroundin! runnin! 9$Ss. & Call dro' disa''ears after adjustin! and loadin! te fre4uenc confi!uration of tis area. .!.! Interference Cause% by Over'covera0e $e objective of one rationall desi!ned network is tat eac cell onl covers te areaaround te 9$S and te MS resides in te nearest cell. $e over=covera!e is tat teservice ran!e of a certain cell is too wide tat te si!nal level at an interval of oretan 1 9$S is still stron! to let te MS reselect or and over to it. It is a 'enoenonin w ic t e ac tu al ce ll service ran!e deviates fro te desi!ned service ran!eBleadin! to irrational traffic loadin!B interferenceB ca ll dr o' B co n! es ti on B a nd ov er failureB etc.Case 555&1%" ault pheno/enon9 $e and over success rate of a certain ?SM network is lowBte call dro' rate is i! and conversation 4ualit is 'oor. $e and over successrate is less tan (5B and te call dro' rate is ore tan 2. It is found tat tere arean ties of downlinkGu'link stren!t and overs trou! view and analsis of traffic easureent data. wile tere are an ties of bad downlink 4ualitB andu'link stren!t aon! te ties of unsuccessful andover. $e analsis of cause of call dro' indicates tat te
ties of bad downlink 4ualit are ore tan tose of badu'link 4ualit . $ere is no alar essa!e in OMC sste ault location process 1 ro te result of traffic easureentB it can be ju d ! e d t a t d o w n l i n k interference a e/ist in te sste or te covera!e is not ver !ood. 2 $e actual result of #rive $est sows tat te stren!t of outdoor si!nal can beu' to =(5d 9 above in te downtown areaB tat is to saB te co ve ra !e is al lri!t. 9ut serious over=covera!e e/ists. or e/a'leB te service cell used in tebuildin! were 9$S A is located is cell 9 wit te sae 9CC6 fre4uenc as cellA1B wile cell 9 is % kiloeters awa fro 9$S A in te suburb. In tis waB te' r o b l e e / i s t s i n t w o a s ' e c t s 1 . $ e s i ! n a l o f c e l l 9 f o r s c o = c a n n e l interference wic leads to 'oor downlink link 4ualit in covera!e area of cell 1 of 9$S A. It is found tat EYYYYE is dis'laed in te test MS wen tis cell is lockeddurin! te test. 2. 7en cell 9 is selected as te service cellB its adjacent cell isonl !eo!ra'icall adjacent to itB wile te cell near te 9$S A does not functionas its adjacent cell. So wen its si!nal is unavailableB te Deffect of isolatedislandE will occur because te si!nal of its adjacent cell is 'oorB too. $en andover fault and even call dro' will easil occur. $e on=site surve sows tat teantenna of cell 9 is un! &5 above. $e data 'rovided b te custoer revealstat te tilt an!le is &ZB wic is actuall far less tan &Z
3 $e cause for bad network indices lies in over=covera!eB so t e ba si c wa is ado'ted to lower te antenna and adjust downtilt of it to ake actual covera!earea consistent wit 'lanned covera!e area. $e'oraril tis 'roble can onlbe solved b adjustin! te network 'araeter. $e followin! o'erations can beado'ted lower te 'ower level of cell 9 and add te adjacent cell of cell 9B at tesae ti e in cr ea se te level tresold of candidate cell fro 15 to 1&. $enetwork indices e/ibit obvious i'roveent after te a b ov e c e ck a n d odification are 'erfored for all cells in te
downtown areaB oreoverB teand over success ratio rises u' to (&B wile call dro' ratio dro's to 1.3. .!." Interference Cause% by A00ressive ,euse $e ca'acit and 4ualit are a 'air of contradictions. In te downtown areaB tere arelar!e nuber of subscribersB so te fre4uenc 'lannin! tecnolo! of ti!t reusesould be ado'ted to satisf te re 4u ir e en t of ca 'a ci t. $ at is B t e in cr ea se of ca'acit is traded b te sacrifice of 4ualit.$e ado'tion of ti!t reuse in te 'lace were te laout of soe 9$Ss is irrationalwill easil lead to collision of co=cannel or adjacent cannel.Case 551;3,; ault pheno/enon9 $e interference of fre4uenc o''in! is serious and te conversation is interittent on a brid!eB tis network ado ' t s t e o d e o f 1 Y 3 fre4uenc o''in!. $ere is no alar. ault location process 1 $e si!nals on te brid!e are disorderl due to distribution of ulti'le 9$Ssaround te river. So te interference of fre4uenc o''in! will easil occur wenado'tin! fre4uenc o''in!. 2 irstB adjust te antenna to ake one ain cell on te brid!eB adjust te antennaand transission 'ower of oter cells to reduce te stren!t of teir si!nalsr e a c i n ! t e b r i d ! e . $ e n c a r r o u t t e t e s t . I t i s f o u n d t a t t o u ! t e interference is reducedB et te interference of fre4uenc o''in! still cannot beunder control because all si!nal receivin! levels reacin! te brid!e are veri! due to te clearance around te brid!e. inall odif te fre4uenc 'lanBand ado't te fre4uenc o''in! 'lan of A[9B i.e.B ado't 1Y3 fre4uenc o''in!for soe cellsB wile 1Y1 fre4uenc o''in! for oter cells. $e interference of 1Y3 fre4uenc o''in! occurs in co=directional cellB wile 1Y1 fre4uenc o''in!avera!es te interference. A cobination of te in soe local areas is better f o r t e d i s ' e r s i o n o f i n t e r f e r e n c e . $ e a c t u a l t e s t r e s u l t i n d i c a t e s t a t t e conversation 4ualit is i'roved si!nificantl. ." ,epeater Interference Re'eater reall e/ibits a little convenienceB so custoers often ake use of it. $ere'eater is also one of te ain interference sources.Case 551;5(% ault pheno/enon9
subsc ribe rs of a c ertai n ne twork co'l ain t at te c ann otoccu' cannel in soe area for conversation since soe daB or noise is eav after occu'anc of cannel tou! te si!nal of MS is stron! at tis tie. $ere are twodirectional 9$Ss in tis area and bot of te are 9$S35 wit te version 5&.5&2,.$e a>iut of te first cell directs at nort. $e 9$S in tis area works norall andte network indices confor to re4uireent before te co'laint. 9ot 9SC and MSCa r e devices of 6uawei and two 9$Ss are connected in star ode. $e trafficeasureent indices sow tat traffic of bot 9 $ S s d e c r e a s e s o b v io u s l a f t e r occurrence of tis 'robleB es'eciall in te first and tird cells. Altou! te si!nal of cannel is ver stron!B te 4ualit of voice is 'oor. $en it can be seen fro trafficeasureent tat te interference band of tese four cells is in class treeB fourB andfiveB and ,& of cannels are under interference. In additionB interference of differentclasses also e/ists in oter cells. So subscribers co'lained stron!l. And tere isno alar essa!e in OMC sste ault location process 1 $e feedback of subscribers sows te 'ossible causes as follows 1. )robleoccurs in transission and leads to error codeH 2. )r ob le oc cu rs in an te nn a feederH 3. ault e/ists in $M
Carr out test on site wit antenna feeder anal>er. No 'roble of 9$S itself isfoundB and te situation reains te sae after $M< is re'laced. $ereforeB wea s k c u s t o e r s w e t e r t e r e a r e s u c n e w l c o n s t r u c t e d e 4 u i ' e n t a s icrowave stationB re'eaterB etc. surroundin! te 9$S. $e told tat te didntset u' te. It is said tat Cina Mobile sets u' a re'eater in te areaB wic islocated about two kiloeters awa in te nort lean to te west of bot 9$Ss of 6u awe iB an d we n it is ac tiv at ed B t e 'roble will occur in 6uawei 9$S. $encustoers ne!otiated wit Cina Mobile several ties. inall Cina Mobilecarried out on=site test wit 6uawei en!ineers to!eterB and found tat onl if tere 'eate r is switced offB te interference band and call becoe noral alon!wit te recover of 6uawei 9$SB if te re'eater is activatedB 'roble will occur soo n i n 6 ua wei 9$S B i .e. cal l c ann ot be 'ut t ro u! B or in te rf er en ce is str on ! even after call is 'ut trou!. $e traffic easureent relevant wit interferenceband in two different cases was anded on to Cina MobileB and te a''rovedour view'oint. inall te 'roble is solved wit t e coordination of CinaMobile. .) Off'networ Interference @/ternal interference sources are $P stationB i!='ower broadcastin! stationBicrowaveB radarB i!=volta!e 'ower lineB analo!ue 9$SB C#MAB ?SM 9$S of anoter o'eraterB etc. .).1 Microwave Interference Case 55515("ault 'e no en on it is fou nd ta t c all dr o' ra te in t e se co nd an d t ir d ce ll of a certain 9$S 0S2G2G2 in traffic easureent increases abru'tl. Call dro' rate is u' toabout 25 at soe tie. ault location process 1 Piew of 9SC traffic easureent sows tat i dle $C6 nuber in interferenceband in tis 9$S be!ins to increase in interference ba nd 3= & at ab ou t ( 35 B in interference band "B & at 1555B and in interference band 1 at about 2255. It can be jud!ed fro te above 'enoenon tat interference e/ists.
2
Since tis 9$S o'erates well beforeB te 'roble of fre4uenc 'lannin! can bee/cluded. 3 )erfor 'ower=off restart and re'lace board for 9$S. 9ut interference still e/istsBso te 'ossibilit of $R: self=e/citation can be e/cluded. " $R: ana!eent inforation reveals tat interference e/ists in four boards of te second and tird cell in tis 9$SB and te 'ossibilit of daa!e of te four boards at te sae tie is littleB so te 'roble of $R: can be e/cluded. $R:board is re'laced for cautionB but interference reains & Piew of all 9SC traffic easureent data sows tat interference of diff erentlevels e/ists in te cells of all 9$Ss nearbB wic is facin! te sae direction aste second and tird cells in tis 9$S. And soeties S#CC6 cannels in tec e l l s w i t s e r i o u s i n t e r f e r e n c e a r e a l l o c c u ' i e d a t t e s a e t i e B w i l e t e occu'anc ratio of S#CC6 at te sae tie is ver little accordin! to te aountof subscriber. So it can be sure tat e/ternal interference e/ists in u'linkB but teinterference a be relevant wit direction instead of fre4uenc. % $o furter locateB ju'ers of te first and tird cell are intercan!ed on te rackt o ' . A s a r e s u l t B i t i s f o u n d t a t i n t e r f e r e n c e o c c u r s i n t e f i r s t c e l l B b u t interference disa''ears in te tird cellB so tis as 'roved te above jud!eent. ; Since interference is not relevant wit fre4uencB 9$ S in te rf er en ce a be caused b i!='ower si!nal sent into 9$S sste. ( Measureent on 9$S divider out'ut 'ort wit s'ectru anal>er s o ws t a t i ! = 'ower si!nal e/ists on ,5"M6> fre4uenc 0&M awa fro t e u s e d fre4uencB and tis si!nal level coe u' to about 2&db in 9$S wit seriousinterferenceB wile in oter 9$S it is about &5db. So it can be jud!ed tat tissi!nal as i'act on 9$S. , After fre4uenc scannin! around 9$S wit s'ectru anal>erB it is found tat aicrowave antenna out'uttin! i!='ower si!nal is at a fre4uenc of ,5".
15 7en te icrowave e4ui'ent is switced off and $ R : a n a ! e e n t inforation is tracedB te interference disa''eared. .). 8i0h'power ;roa%castin0 Station Interference Case 55552;, ault pheno/enon9 te 4ualit of MS call is ve r 'oor in te or nin! of te tird da 0Monda after a 9$S cutoverB and it is ard to ake calls 2 k awa fro te9$S. $e voice is un der a serio us interferen ceB and te co'laint of subscriber increases obviousl. Interference band is found lar!e in traffic easureent of OMC. ault location process 1 7en #rive $est is carried out around te 9$SB it is found tat MSs R: si!nallevel 0downlink level as little can!e 0about %5d9B but te si!nal 4ualit Ras too uc can!eB it will ju' fro 5 to ; and call dro' occurs. 2 $e fault reains te sae after te $R: corres'ondin! to te fre4uenc isre'laced. It is sus'ected tat fault is caused b e/ternal interference.
Measureent for e/ternal electroa!netic environent wit 6)(&,&@ s'ectruanal>er sows tat stron! interference e/ists around te fre4uenc of 9$S.$rou! counicatin! wit custoer and te Radio Resource Mana!eentCoitteeB we !et known tat te interference is caused b si!nals transittedb one essa!e transitter of soe co'anB wose R band is just adjacentto te 'lanned ?SM fre4uenc. $is transitter usuall transits ever MondaBand no suc 'enoenon is found in two das after 9$S is activated
.# Other 3heno/ena Causin0 Interference Soeties altou! no intra=network and e/=network interference e/istsB fault of s o e d e v i c e s c a n a l s o a k e c o n v e r s a t i o n 4 u a l i t b a d .
S o e c a s e s b e l o w a r e anal>ed detailedl. $e ave i! reference value.Case 551&2;" ault pheno/enon9 9SC as si/ odules. $e wole 9SC is cascaded wit 1&59$Ss 09$S312B ;&5$R: in total. One ont after te ca'acit e/'ansion of 9SCand MSCB custoers re'ort tat tere is serious voice 4ualit 'roble in te wolenetwork. $ere e/ists serious cink durin! conversation under an 9$Ss. 7e coeto count A wit serious co'laint to ake a dial test. ault 'enoenon is found asfollows tere e/ists stron! back!round noise. It ainl contains sound of etalB sucas Dtin!B dan!E and so on. One 'art or bot 'arties can not ear eac oter clearlwen te noise is serious 0One 'art is in te ran!e of covera!e of tis 9$S and teoter under a noral 9$S. 7en fault occurs te subscriber under tis 9$S can not e a r c l e a r l B w i l e t e o t e r c a n . 7 e n t e v o i c e c a n n e l o f t e f a i l e d 9 $ S i s occu'iedB all te voice cannel of eac cell a ave sound of etal. 9ut it occurs just at soe tie. $e occurrence ratio is 15. $e si!nal of te MS is ver !ood andtere is no interference on te radio interface. $e fault 'enoenon occurs went e rin!back tone is sent b ack. $at is to saB so lon! as te v oi ce c a n n e l i s establisedB te fault will occur. #isturbance of different de!rees will e/ist durin!noral conversation. 7en te fault is seriousB one 'art 0or bot 'arties can notear clearl durin! conversation. $e fault as a certain continuit in ters of tie.Soeties te 'robabilit of occurrence of etal cink is ver i! and soetiesfault 'enoenon cannot be ca'tured. $ere is no alar essa!e in OMC ssteCause analsis tis case is about noise in voice 'roble. It is usuall caused berror code. $e 'ossible cause for error code is te fault of boardsB connectors or wirin! trou! wic te voice si!nal is sent. 9esidesB !roundin!B interferenceB clockalso sould be considered. Interference e/istin! on radio link a also cause error.$e clock tat is unsncroni>ed will cause frae sli' or frae loss. #ifferent error code s ave teir certa in re!u larit as for erro r code o n w ir in !B i f i t i s A i nt er fa ce o r u '' erB n oi se a nd v oi ce av e su'eri'osed effect because )CM sa'le value isinfluenced. $ereforeB te noise is re!ular and tere is little fluctuation. If it is below AinterfaceB error codes are also re!ular. 6oweverB because te co'ressed voice si!nal is influencedB it needs decodin! before earin!. $erefore B tere is !reat noisefluctuation. Soe words are noralB wile soe words can not
be reco!ni>edB sucas bubblin! soundB discontinuitB sound of etal and so on. As for frae sli' or fraeloss of clockB it as a tie re!ularit. or e/a'leB one frae lost in several inutes.$ereforeB noise occurs in tie durin! conversation. Cobine te descri'tion of fault'enoenonB ake s'ecific locatin! 'rocessin!B refer to 'art of 'rocessin! course. ault location process 1 Ceck te 9$S of count A test transission error code and find transission isw i t o u t e r ro r c o de H c ec k $ R: B ) e te coonness of eac failed 9$S and find tat tese 9$S are allunder 9M". Make sure weter all 9$S under 9M" ave tis case. Coose oter 9$Ss und er 9M " to a ke dia l te st and fi nd ever 9$S as tis 'roble. All9$Ss under oter five 9M odules ave no tis case trou! dial test. $e' r o b l e o f e t a l c i n k i s r e l a t e d t o 9 M " t r o u ! a b o v e l o c a t i o n B a n d t e 'roble e/ists in one certain 'rocess of 9M" Dvoice si!nal transission 'atE. 3 $ransission 'at of voice si!nal MS radio link 0includin! antenna feeder s s t e 9 $ S 0 @ 1 l i n e 9 $ S # # t r u n k t r a n s i s s i o n 9SC##0@1 line329I@067 lin e ?N @$ ?O )$ 0o 'ti c fib er ?9I?C$N@3M 0@1 line or transission deviceMSM$CMSC. "
Ado't locatin! etod of anali>in! section b section. At first anal>e and seeweter ter e is soe tin! wron! wit switin! ne tw or k bo ar d 0? N@ $ an d?C$N and fiber interface circuit ceck te connection and connector betweenA M a n d 9 M " . $ e a r e n o r a l . < s e a b s o l u t e a l c o o l t o c l e a n t e f i b e r connectorB but te fault reains te sae. @/can!e te tird and fourt 9Is0i ncl udin ! 9C corres'ondin! to 9M3 and 9M" wit te first and second 9Iboard corres'ondin! to 9M1 and 9M2B but te fault reains te sae. Can!e9M" ?O)$B but te fault reains te sae. $e 'ossibilit of e/istence of circuiterror code in te 'art DO)$0fiber 9IE can be e/cluded. Swa' 9M" ?N@$boardB te 'roble still e/istsH swa' ?C$N boardB te 'roble is stillH e/can!e?N@$ board wit 9M3B te 'roble is stillH e/can!e @3M board wit 9M3B te'roble is still. & $e sae fault e/ists in all 9$S under te wole 9M". @rror code sould note / i s t o n 6 7 * i n e s b e t w e e n 3 2 9 I @ a n d N @ $ b o a r d . $ a t i s b e c a u s e i t i s i'ossible tat all 67 *ines between 329I@ and ?N@$ board are not !ood. % Ceck te connection line of 9M" fro @3M to MSM carefullB and find tat teconnector of @3 M is noralH ceck one con nector of MSM and find tat te4ualit of te connector of trunk lines beind one MSM 0board No. is 3 is bad.#ef or at ion and inv a! ina tio n occ ur on te inner 'in of one connector. $eresult is tat te connector cannot connect te connector of MSM board onback'lane well. $e cause lies in ere. 7en te subscriber occu'ied $CSMunder 9M" sound of etal a occur. $e nuber of MSM of te failed $CSM is3B and te nuber of $C is ("B (&B (%B (;. A interface circuit CIC is 233%F2"%3. ; Redo te trunk connectorB te fault is eliinated. #urin! te conversation under all 9M" tere is no sound of etal.7en MSC assi!ns circuitB te circuits in te odule tat te si!nalin! link belon!s towill be selected wit i!er 'rior it. If te si!nalin! of t e MS call is transittedtrou! odule " of MSCB MSC will assi!n t e c i r c u i t o f o d u l e " f i r s t 0 t e corres'ondin! CIC is fro 22"5 to 2(1&. $e failed circuit 0CIC is fro 233% to 2"%3corres'onds to odule " of MSC. So if te si!nalin! of call is transitted trou!odule " of MSCB te rate for bein! assi!ned to te failed circuit is
ver i!. As for 9SC B 9 $S of od ule " s ele cts A int erf ace lin k f irs t to tr an s it si !n al in !. $ er e ar e tree links on odule " of 9SCB $wo of wic corres'ond to odule " of MSC. So if te MS is used under odule " 9$SB tere is a 'ossibilit of 2G3 to be assi!ned to tecircuit of MSC odule ". 12( of MSC odule " circuits as fault 0corres'ondin! to9SC " odule 0te 'ro'ortion of failed circuit of MSC odule " is 12( G& ;% an d it a brin! about 'robles of voice 4ualit. $e i!est rate of occurrence of fault 0allave fault wen 12( circuits is bus is about 2G3 Y 12(G&;% 1& . In fact te fault of dial test under 9$S is 15 or so. .= alse Interference Soeties we ade !reat efforts to ceckB but onl find tat it is false alar in te end. In fact te interference is false. Indeed it is better to ave no interference tanave it. ault pheno/enon9 te reconstru ction of soe office found tat t e interfere nce band of an S%G%G% 9$S25 in a count is ver i!. $einterference band of two cellsin it can!ed fro & to ;. ault location process 1 #urin! te 'ast interference test oftis officeB soe cells wit i! interferenceband were loca ted. $is is becau se anten na interodulation resulted in teinterference of noral si!nal in case of lar!e traffic and it ade te interferenceba nd ve r i ! . So c an !e t e antennaB but te interference band did not falldown obviousl after tat. 2 #urin! te 'rior 'eriodB te fre4uenc 'lannin! as been cecked several tiesBand te ad=fre4uenc interference as been avoided basicall. At te sae tiete fre4 uenc ta t a caus e ti rd or der interodulation in te cell as beenadjusted. $e 'roble of fre4uenc 'lannin! as been basicall e/cluded. It isunknown weter tere is soetin! wron! wit $ower $o' A'lifierB feeder or connector. 9ut no 'roble was found after ceckin! te antenna feeder ssteof te 9$S several ties. 3 $race te state of interference band of eac cannel via Maintenance Consoleand find tat i! interference band ainl focuses on te four $R:s of te cell. " irst set te fre4uenc wit less interference to te $R: wit ore interferenceBand find tat te interference band does not can!e. It sows
tere is no relationto te fre 4u en c. 7 et er te re is so et in! wron! wit $R: board or not isu n k n o w n . 6 o w e v e r B t e s i t u a t i o n i s u n c a n ! e d a f t e r t e $ R : s w e r e intercan!ed. & $en confir te $R: nubersB and find tat te four carriers coe fro tesae divider. ro te above 'rocessB te 'roble a be te divider. 9ut it isfound tat te interference band becoes i! wen te 9$S is e/'anded froS" G" G" to S% G% G% . 7 il e t e cobinerGdivider used to be noral. Mabe ted e v i c e s b r e a k d o w n a f t e r s o e t i e . S o w e d e c i d e d t o c a n ! e t e cobiberGdivider to ave a tr. % $e idea tat four carriers wit i! interference band are connected to te saesecond level divider before te divider is can!ed. $e ;=d9 !ain of te divider as been considered durin! interference jud!eent. 6oweverB if te #I) switcis not oved to te ri!t 'lace wile cascadedB te interference si!nal will be a'lified b ;d9. SiultaneouslB i!er interference band will e/ist because teca lc ul at in ! er ro r of 2. 5 st ati on it se lf is u' to &d9. Ceck te #I) switc of tedivider. It was reall not oved to DOffE. After it is correctedB view te trafficeasureent of interference band " and &. $e fall down to 5. And tere is alittle value on te interference band tree
Chapter ! Anti'interference Measures Anti=interference Measures of ?SM are re4uenc 6o''in!B dnaic 'ower controlB#$:. 7ile te a!!ressive reuse is ado'tedB fre4uenc o''in! and dnaic 'ower control sould be ado'ted as well.$o adjust te obli4uitB a>iutB ei!t of antenna is also a ain o'tii>ation wa toreduce network interference. $e ai for adjustin! is to ake te real service area of e a c c e l l a ' ' r o a c t o t e d e s i ! n e d s e r v i c e a r e a t o r e d u c e o v e r = c o v e r a ! e . t e etods of adjustin! antenna 'lease refer to relative !uidance book.$ ese anti= interference easures ainl ai at intra=network interference. 7entere is stron! e/ternal interferenceB tese anti=interference easures can ardl takeeffect.9 t e waB re i nd ev er bo d t at
9SC of 6ua wei a s t e fun cti on of fre 4u enc o''in!B 'ower control and #$: b default. 6oweverB for soe e4ui'ent of soeoter vendorsB ever function sould be 'urcased b te o'erators teselvesB andte 'rice is ver i!. $e currentl servin! network e4ui'ents of an o'eratorsave no tese functions. #urin! o'tii>ation as $ i r d ) a r t o r c o = o ' e r a t i o n t o e4ui'ent of oter vendorsB 'lease 'a attention to tis atter Chapter " Interference Test Tools ".1 ;rief intro%uction to Spectru/ Analy@er 1 At 'resentB te ain tool 6uawei as for testin! interference si!nal is S'ectruAnal>er. It is a broadband si!nal receiver wit i! 'e rf or a nc e wi c ca n dis'la te s'ectru of te receivin! si!nals. $e receivin! sensitivit of si!nalbandwidt of /6> e4uals to 16> sensitivit[15lo!/B e.!.B te receivin! sensitivitof ?SM si!nal of 255k6> is =1"2d9[15lo!0255Y1555=(,d9H 2 $e receivin! si!nal resolution bandwidt 0R97 nael te iniu si!nalbandwidt te S'ectru Anal>er can reco!ni>e. $e saller te 'araeter isBte i!er te receivin! sensitivit of instruent. $at is to saB te noise of teinstruent itself is lessH $e S'ectru Anal>er of different t'es as differentreceivin! fre4uenc band and receivin! sensitivit. It is ver i'ortant to akeuse of it corre ctl. A brie f introduction to several ke inde/es of te S'ectruAnal>er is ade as follows 3 In'ut fre4uenc te fre4uenc ran!e te S'ectru Anal>er can receive. $isinde/ deterines te fre4uenc ran!e of interference si!nal tat te Analser can testH " Sensitivit !enerall te iniu receivin! level wit 16> si!nal bandwidt isd e f i n e d a s r e c e i v i n ! s e n s i t i v i t o f t e S ' e c t r u A n a l > e r . $ e r e c e i v i n ! sensitivit of 6)(& series S'ectru Anal>er can be below =1"2 d9. &
Pideo ilter 9andwidt 0P97 it refers to te bandwidt of te interediate filter after re4uenc i/in! of te S'ectru Anal>er. $e saller te bandwidt isBte sooter te curve isH % Central fre4uenc 05 it refers to te central fre4uenc of te s'ectru tat teS'ectru Anal>er can testH ; 9andwidt 0S)AN it refers to te s'ectru s'an te S'ectru Anal> er cantestH ( In'ut si!nal attenuation 0A$$ wen tere is lar!e si!nal in'utB it is re4uired toake attenuation on si!nal 'ro'erl. $e S'ectru Anal>er itself a 'roducelar!e nuber of inter= odu latio n co'one nts witout atte nuat ion. So it willinfluence te veracit of te testin! result.$e ain tecnical indices of interference test s'ectru anal>er
". Directional Antenna #irectional antenna is used for searcin! interference sources. $e stron!er tedirectionalit of antenna isB te i!er te antenna !ain is. And te abilit to searcwill becoe better. So te lo!arit='eriod antenna wit broad fre4uenc band is tebest coice. $is kind of antenna as broad fre4uenc bandB i! antenna !ain andstron! directionalit.
Chapter ) *ay to Test Interference ).1 The way to Test Internal Interference 1. Set te S'ectru Anal>er to 'ro'er stateor ,55M 9$S f5,52M6>BS)AN35M6>BA$$5BR9735k6>BP9735k6>H or 1(55M 9$S f51;1&M6>BS)AN15M6>BA$$5BR9735k6>BP9735k6>.2 . S cr e w o u t t e c on n ec to r o f o u t' u t ' o rt o f C #< d iv i de rB t e n connect te out'utsi!nal of te divider to te S'ectru Anal>er to carr out a test. If te fractionalfre4uenc s'ectru level is less tan (5d9B it sows tat tere is no internalinterferenceH if ore tan (5d9B it sows tat C#< or $R: inside 9ase Station areunder interference or self=e/citation.3. If internal interference e/istsB furter ake sure tat it belon!s to C#< or $R:. Atfi rs t con fi r $R: carrier boardB cut down te cable via wic $R: is connected to dividerB and use te S'ectru Anal>er to test te ain or diversit connector of $R:.If te fractional fre4uenc s'ectru level is less tan (5d9B it sows tat $R: isnoralB oterwise it is re4uired to can!e carrier board.$e tree ste's above ai at interference easure for te u'link fre4uenc band. If tere is sus'ect tat interference e/ists in te downlink fre4uenc bandB 'lease followste's below.". Ceck interference of transission band. irstB set te S'ectru Anal>er i nt ra ns i ss io n f re 4u en c b an d o f t e 9 $S . # ue t o t e l ar !e ou 'u t 'o we r of 9$ SB attenuation sould be ade on te in'ut si!nal. ?enerall A$$ is set as "5d9B tent e t/test si!nal of C#< sould be i'orted to te S ' e c t r u A n a l > e r t o b e observed to ake sure weater interference si!nal is !enerated. ). The way to Test 2ternal Interference 7en we are sure tat interference is caused b te e/ternal causeB first we souldconfir te location of interference source and te s'ectru distribution state. Aconvenient wa is to ake use of te e/istin! antenna feeder of 9ase Station andlow=noise a'lifier of Radio re4uenc ront @nd to ave a test. 1 irstB set te S'ectru Anal>er to 'ro'er stateB 'lease refer to te ca'ter su'ra. 2 Coose out'ut 'ort of divider of cell under interference. In order not to influencete noral o'eration of 9$SB te free out'ut 'ort 0wit du load is !enerallcosenB eiter te ain or te diversit can be selected. 3
Screw out te selected connectorB ten use Coa/ial Cable to i'ort te out'utsi!nal of divider to te S'ectru Anal>erH " Piew te s'ectru distribution state of te S'ectru Anal>erB and find out teabnoral interference si!nal. $e wa to calculate te level of interference si!nalis as followsAntenna 'ort interference level interference level tested b te S'ectru Anal>er 1&d9 $ower $o' A'lifier ?ain [ 3d9 cable loss ;d9 divider !ain.or e/a'le Antenna 'ort interference level = %&d9=1&[3=;=("d9Note Cable loss a var wit cable len!t.$e standard for jud!in! weater interference level as i 'a ct on t e ss te is described as follows
01 $e a/iu interference level at antenna 'ort witout influence on sste =15(d9 sensitivit ,d9 co=cannel interference 'rotection =11;d9.
02 $e a/iu interference level at divider out'ut 'ort witout influence onsste =11;d9[1&=3[; =,(d9 ).! The way to Search 2ternal Interference Sources $e location of interference source can be e/ained via 9$S divider out'ut 'ort. If iti s r e4 ui re d t o f in d t e or e d et ai le d l oc at io n o f i nt er fe re nc e s ou rc eB w al k o ut o f e4ui'ent rooB and use te directional antenna wit stron! directionalit entionedabove to ake a searcB $e ste's for searcin! are as follows 1 In te cell under interferenceB select a test 'oint witout buildin! obstruction. 2 Set te S'ectru Anal>erB and connect te directional antenna. 3 If tere is rotatable 'latforB te antenna can be 'laced on itB and ake tew a v e b e a o f t e a nt en na ' oi nt t o t e frontB and te antenna wit vertical'olari>ation sould be 'laced verticallH if tere is no interferent si!nalB one canraise te antenna over ead wit ands. Rotate te antenna slowlB and at tesa e ti e vi ew
