ok giai phap toi uu gsm

8/3/2019 Ok Giai Phap Toi Uu GSM

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GII PHP TI U HO MNG THNG TIN DING GSMOptimize network solution of mobile GSM

Sv:ng Minh Tm, GVHD: Bi ThCao, Phm Ngc Dng.

Khoa Cng ngh in t, Tr ng H Cng Nghip TP.HCM.

TM T T: Bi bo ny s gi i thiu s l c v mng thngtin ding GSM. Phn chnh ca bi bo s phn tch s cnthi t ca vic ti s d ng t n s v cc v n pht sinh sau , ng th i s xu t ph ng php t i u mng v tuy n, lv n chnh trong t i u mng thng tin ding GSM.

ABSTRACT:This article introduces a glance over mobileinformation network GSM. The main part of the article willanalyze the need for re-use frequency of the problems arisingthereafter, at the same time, will propose methods optimized radio network, being the main problem in the optimal mobilenetwork GSM.

1. GI I THIUH thng thng tin ding ton cu (ting Anh:

Global System for Mobile Communications; ting Php:Groupe Spcial Mobile; vit tt: GSM) l mt cng ngh dng cho mng thng tin ding. Cc mng thng tin ding GSM cho php c th roaming v i nhau. Donhng myin thoi di ng GSM ca cc mng GSMkhc nhau c th s dng c nhiu n i trn thgi i.

GSM l chun ph bin nht choin thoi di ng(TD) trn th gi i. Kh nng ph sng rng khp n ica chun GSM lm cho n tr nn phbin trn thgi iv cho php ng i s dng c th s dng TD ca h nhiu vng trn thgi i. GSM khc v i cc chun tinthn ca n vc tn hiu v tc , cht l ng cuc gi.N c xem nh l mt h thng TD th h th hai(second generation - 2G). GSM l mt chun m , hin tin c pht trin b i 3rd Generation Partnership Project(3GPP).

Vo u thp nin 1980 ti chu u ng i ta pht

trin mt mng in thoi di ng ch s dng trong mtvi khu vc. Sau vo nm 1982 n c chun hob i CEPT (Conference of European Posts andTelecommunications) v to ra Groupe Spcial Mobile(GSM) v i mc ch s dng chung cho ton Chu u.

Cho n nm 2006 s thu bao ding GSM lnt i con s2 t v i trn 700 nhiu hnh, chim gn 80%th phn thng tin ding trn thgi i.

1.1 T ng quan v h th ng thng tin di ng GSM

Hnh 1. S kh i h th ng thng tin ding GSM MS (mobile station): Trm dingBTS (Base transceiver station): Trm thu phtBSC (Base station controller): B iu khin trm nnBSS (Base station system): H thng trm nnMSC (Mobile services switching center): Trung tm

chuyn mch mobile

GMSC (Gateway Mobile services switching center):Cng kt ni gia MSC v cc tngi ngoi

OMC (Operation and maintenance center): Trung tkhai thc v bo d ng

OS: H thng khai thc

1.2 Giao di n v tuy n (Radio interface) trong GSM Trong GSM, giao din radio s dng tng h p c hai

ph ng thc phn knh theo tn s v th i gian: FDMA(Frequency Division Multiple Access) v TDMA (Tim

Division Multiple Access).Trong GSM s dng bng tn ti 900 MHz (gi l

GSM 900) v 1800 MHz (gi l GSM 1800). y tach cp n GSM 900. Mi knh c c trng b imt tn s (sng mang) cho mi h ng thu pht, cc tnsny cch nhau 200 Khz.

Trong GSM 900, tn hiu t MS n trm thu pht l890-915 Mhz l dy tn uplink, cn dy tn downlink t


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trm thu phtn MS l 935-960 Mhz . C haiu c rng bng l 25 Mhz, v i 125 knh truyn dn.

tng thm hiu sut s dng ph tn s, trongGSM dng k thut TDMAchia mi knh tn s 200kHz thnh 8 khe th i gian,nh s 0 7. Mi khe s

c cp pht cho ng i dng.1.3 Khi ni m Cell

H thng thoi di ng tr c y c cu trc gingnh h thng truyn hnh pht thanh qung b: Mt trmpht sng cng sut mnh t ti mt cao im c th pht tn hiu trong vng bn knhn 50km.

Trong cu trc ny, s knh thoi trong giao dinradio rt hn ch. Gi s dng ht c bng tn GSM 900,theo tnh ton trn ch t ti a l 125* 8 = 1000 knhthoi m thi.

Hin nay cn s l ng knh thoi gp nhiu ln ktqu tnh ton trn, ng i ta cn ti s dng li tn s ticc vng khng gian khc nhau, cc vng khng gian nygi l Cell. Tn s cell ny c th c ti s dng cell khc, cc cuc in thoi vn c duy tr lin tckhi thu bao di chuyn t cell ny sang cell khc.

Hnh 2. Khi nim CellCell (t bo hay ): l n v c s ca mng, ti

trm di ng MS tin hnh traoi thng tin v i mngqua trm thu pht gc BTS. BTS traoi thng tin quasng v tuyn v i tt c cc trm di ng MS c mttrong Cell.

Gi s bng cch phn chia mt vng trung tm thnh100 vng nhh n (cc tbo), nu mi cell v i kh nngcung cp 12 knh thoi. Khi nng lc ca h thng v l thuyt c th tng t 12 lnn 12x100 = 1200 knhthoi. Nh vy l dung l ng h thng tng ln rtnhiu ln.

Vic thit kcc Cell l n hay nh l do thc t.

S dng cc Cell l n khi: Sng v tuyn t b che khut (vng nng

thn, ven bin ) Mt thu bao thp Yu cu cng sut pht l n

S dng cc Cell nhkhi: Sng v tuyn b che khut (vng th l n) Mt thu bao cao Yu cu cng sut pht nh

Hnh 3. Thi t k cc Cell

1.4 C p d ch v - GoS (Grade of Service)V ng i s dng truy cp knh v tuyn theo kiu

ngu nhin. Khi s ng i dng tng ln, s cuc gi iqua knh cng tng, nn thng l ng tng ln. C thxyra tnh hung nhiu ng i dngng th i truy cp mtknh v tuyn, khi ch c mt ng i c dng knh,nhng ng i khc b tc nghn.

Offered Traffic = Carried Traffic + Blocked Trafficmt knh ng trc c cht l ng phc v cao th

xc sut nghn phi thp. Vy nn s ng i dng c th phi b gi i hn. Nu chp nhn mt cp phc v thph n, tc l xc sut nghn l n h n, th t ng ng tng c dung l ng mun truyn (tng sng i dng). GoScng mt ngh a v i xc sut nghn:

Lu l ng mun truyn: A (lu l ng mun truyn)Lu l ng b nghn : A*GoS (lu l ng mt i)Lu l ng c truyn : A*(1 - GoS) (lu l ng pht

ra)Theo thng k cho thy th cc thu bao c nhn s

khng nhn ra c s tc nghn h thng mc d i10%. Tuy nhinmng hot ng v i hiu sut cao th


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mng cellular th ng c GoS = 2 % ngh a l ti a 2%lu l ng b nghn, ti thiu 98% lu l ng c truyn.

Hnh 4. Xc su t ngh n GoS

2. PH NG PHP

V i l ng bng tn gi i hn c phn b tr c, tng cht l ng phc v, gim nghn mch, ng i ta tmcch tng s knh thoi traffic ln bng cch ti s dngli tn s. Nu tm ra cch phn bcc tn s ln cc Cellh p l s t yu cu ti u cc knh thoi v i cht l ngchp nhn c. y l vic phc tp v i hi phikho st nhiu vn . T vic t chc cu trc li mngt ong (Cells), tm kim cc nguyn nhn gy nhiu choh thng cng nh o c thc t chng, cn phi d kin tnh hung lu l ng tng t bin trong t ng lai,ng th i cng cn thit b o v cng c phn mmchuyn dng h tr .

Trong thng tin ding nhiu ng knhnh h ngnhiu nht n cht l ng thoi, k n l nhiu knh lncn, cn nhiu trngnh h ng khng nhiu so v i 2 loitrn.

Nhiu ph thuc nhiu vo cch tchc cc Cell. Nidung sau s trnh by kh k v hai vn ny v milin hgia chng.

2.1. V n nhi uMt c im ca cell l cc knh tn s ang s dng

Cell ny c th c s dng cc cell khc. Nhnggia cc cell ny phi c mt khong cch nht nh.iu ny c ngh a l cell s b nhiu ng knh do viccc cell khc s dng cng tn s.

Vng ph sng ca trm gc s b gi i hn b i l dony h n l do tp m thng th ng. Mt vn trongthit k h t ong liu khin cc loi nhiu ny mcchp nhn c. iu ny c thc hin mt phn b ivic iu khin khong cch s dng li tn s. Khongcch ny cng l n th nhiu cng b.

cht l ng thoi lun c m bo th mc thuca sng mang mong mun C (Carrier) phi l n h n tngmc nhiu ng knh I (Interference) v mc nhiu knhln cn A (Adjacent).

2.1.1. Nhi u ng knh

Nhiu ng knh xy ra khi c hai my pht, pht trncng mt tn s hoc trn cng mt knh. My thuiuchnh knh ny s thu c c hai tn hiu v i c ngph thuc vo v tr ca my thu so v i hai my pht.

T s sng mang trn nhiu c nh ngh a l c ngtn hiu mong mun trn c ngtn hiu nhiu.

C/I = 10log(Pc/Pi) .Trong:Pc = cng sut tn hiu thu mong mun

Pi = cng sut nhiu thu c.Hnh 5. ch ra tr ng h p m my ding (cellphone)

t trong xeang thu mt sng mang mong mun t mttrm gc phc v (Serving BS) vng th i cng angchu mt nhiu ng knh do nhiu pht sinh ca mttrm gc khc (Interference BS).

Hnh 5. T s nhi u ng knh C/I Theo khuyn ngh ca GSM gi tr C/I b nht m

my ding vn c th lm vic tt l 9 dB. Trong thct, ng i ta nhn thy rng gi tr ny cn thit phi lnn 12 dB ngoi tr nu s dng nhy tn th m i c th lm vic mc C/I l 9dB.mc C/I thp h n th t l li bit BER (Bit Error Rate) s cao khng chp nhn c v m ho knh cng khng th sa li mt cchchnh xc c.

T s C/I c dng cho cc my ding ph thucrt l n vo vic quy hoch tn s v mu ti s dng tn


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s. Ni chung vic s dng li tn s lm dung l ngtng ng k tuy nhinng th i cng lm cho t sC/Igim i. Do vic quy hoch tn s cn quan tmnnhiu ng knh C/I.

2.1.2. Nhi u knh ln c n

Nhiu knh ln cn xy ra khi sng v tuyn ciu chnh v thu ring knh C song li chu nhiu t knh ln cn C-1 hoc C+1. Mc d thc t sng vtuyn khng c chnh thu knh ln cn , nhngn vn ngh mt s png nh l cho php knh lncn gy nhiu t i knh m my thuang iu chnh. T ssng mang trn knh ln cn c nh ngh a l c ng ca sng mang mong mun trn c ng ca sngmang knh ln cn.

C/A = 10.log(Pc/Pa)

Trong :Pc = cng sut thu tn hiu mong munPa = cng sut thu tn hiu ca knh ln cnGi tr C/A thp lm cho mc BER cao. Mc d m

ho knh GSM bao gm vic pht hin li v sa li,nhng vic thnh cng th cng c gi i hn i v inhiu. Theo khuyn ngh ca GSM, cho vic quyhoch tn s c tt th gi tr C/A nhnht nn l n h n- 9 dB.

C hai t s C/I v C/A u c th c t ng ln b ngvic s d ng quy hoch c u trc t n s .

2.1.3. M t s bi n php kh c ph c

C cc ph ng php gim can nhiu knh chung(Nhiu ng knh C/I) nh

1. Tng c ly s dng li tn s (D)2. H thp cao anten trm gc3. S dng Antennh h ng BTS (Sector

ha)

V i ph ng php tng c ly s dng li tn s D s lm gim can nhiu knh chung, tuy nhin khi s celltrong mi mng mu s tng, t ng ng v i s knh tns dnh cho mi cell s gim v nh vy th dung l ngphc v sgim xung.

Ph ng php h thp anten trm gc lm chonhh ng gia cc cell dng chung tn s s c gim b tv nh vy can nhiu knh chung cng c gim b t.

Tuy nhin, vic h thp anten s lmnh h ng ca ccvt cn (nh cao tng) t i cht l ng ca h thng tr nn nghim trng h n.

Ph ng php s dng Antennh h ng BTS c haich l i: Mt l bin php lm gim can nhiu knh chungtrong khi c ly s dng li tn s khngi, hai l tngdung l ng h thng.

Khi dng Omni Antenna

Hnh 6. Nhi u khi dng Anten v h ng (Omni )Ta gi thit hai cell E1 v E2 s dng chung mt tn

sv E1 ca th cao h n so v i E2. Mt thu bao MS

ang di chuyn t E1 t i E2. Khi thu bao di chuyncng gn E2, khnng gy nhiu ca n t i E2 cng l n.Khi dng Sector Antenna

Hnh 7. Nhi u khi dng Anten sector ha

By gi ta cng vn dng E1 v E2. Nhng csector ho thnh: EA1, EB1, EC v EA2, EB2, EC2.

MS di chuyn v pha E2, xut pht t EA1 (ckhong cch l n nht t i E2). Khi MS v t qua v tr trm EA1, n c chuyn giao t i EB1 v khong ccht MS t i E2 gn h n. EB1 cng tn s v i EB2 nhngnh a hnh ta thy, cc nhiu n to ra u nm phasau anten ca EB2 (v l antennh h ng nn c t s nng l ng h ng tr c trn h ng sau = 6 15 dB).iu ny c ngh a l kh nng chng nhiu ca h thng

tng t 6 15 dB. T ng t nh vy khi MSi t iEA2 n ch to nhiu cho EA1 t pha sau ca antenEA1.

Tm li dng sector anten l mt bin php lm tngt sC/ I ca h thng.


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2.2. Khi ni m Cell, Site, ClusterCell l vng khng gian ph b i 1 bp sng ca mt

antenSite l vng khng gian ph b i nhiu bp sng ca

nhiu anten trong cng trm thu pht sng BTS

V i Cc antennh h ng lch 1200: 1 Site = 3 Celllch nhau 1200.

Hnh 8. Khi nim Cell, SiteCluster l mt nhm cc cell. Cc knh khng c

ti s dng tn s trong mt cluster.Nh khai thc mng c giy php s dng mt s c hn cc tn sv tuyn. Vic quy hoch tn s, ta phisp xp thch h p cc tn s v tuyn vo mt Cluster sao cho ccCluster s dng li tn sm khng b nhiuqu mc.

Hnh 9. Cluster gm N = 7 cellsC ly dng li tn s

Ta bit rng s dng li tn s cc cell khc nhau th

b gi i hn b i nhiu ng knh C/I gia cc cell nnC/I s l mt vn chnh cn c quan tm.

D dng thy rng, v i mt kch th c cell nht nh,khong cch s dng li tn s ph thuc vo sCell Ntrong 1 Cluster. Nu N cng l n, khong cch s dng litn scng l n v ng c li.

Ta c cng thc tnh khong cch s dng li tn s:

D = R* N *3 (trong: R l bn knh cell)

Hnh 10. Khong cch D ti s d ng t n s Tnh ton C/Ing th i ta c cng thc tnh t sC/I nh sau:P l v tr ca MS thuc cell A, chu nh h ng nhiu

knh chung t cell B l l n nht.

Hnh 11. S tnh C/I Ti v tr P (v tr my ding MS) c:

I C =

x

x

R R D )( =

x

R D

1 = ( N .3 -1)x

Trong x l h s truyn sng, ph bin nm trongkhong t 3 n 4i v i hu ht cc mi tr ng.

)(dB I C = 10x*lg( N .3 -1)

T sC/I (dB)Scell (N)

x=3,0 x=3,5 x=03 9,0 10,5 12,0

4 11,7 13,7 15,67 16,6 19,4 22,2

9 18,7 21,8 24,9

12 21,0 24,5 28,0

21 25,2 29,4 33,6

Hnh 12. Bng quan hN & C/I


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2.3. Cch t ch c Cluster trong m ng t ongK hiu ca mu s dng li tn s l M / NM = tng ssites trongCluster N = tng scells trongCluster Ba kiu mu s dng li tn s th ng dng l: 3/9,

4/12 v 7/21. a. M u ti s d ng t n s 3/9

Mu ti s dng li tn s 3/9 c ngh a cc tn s s dng c chia thnh 9 nhm tn s n nh trong 3 v tr trm gc (Site). Mu ny c khong cch gia cc trmng knh l D = 5,2R.

Cc tn s mu 3/9 (gi thit c 41 bng tn t ccknh 84n 124, chim bng tn chung 41*0.2 MHz =8,2 MHz s dng trong mng GSM900 ca VMS)

n nh tn s A1 B1 C1 A2 B2 C2 A3 B3 C3

BCCH 84 85 86 87 88 89 90 91 92TCH1 93 94 95 96 97 98 99 100 101TCH2 102 103 104 105 106 107 108 109 110

TCH3 111 112 113 114 115 116 117 118 119TCH4 120 121 122 123 124

Hnh 13. Phn b t n s cho cc Cell trong Cluster 3/9Ta thy mi cell c th phn b cc i n 5 sng

mang. Nhng phi dnh ra mt khe th i gian cho BCH,mt khe th i gian cho SDCCH/8. Vy s khe th i giandnh cho knh lu l ng ca mi cell cn (5 x 8 2) =38 TCH.

Trong 9 Cell ca Cluster phi mt 2*9 = 18 knh, cnli 41*8 18 = 310 knh logic dnh cho traffic.

Hnh 14. M u ti s d ng li t n s 3/9

Theo l thuyt, cu trc mng 9 cells c t sC/I > 9dBm bo GSM lm vic bnh th ng.

T s C/A cng l mt t s quan trng v ng i tacng da vo t s ny m bo rng vic n nh tns sao cho cc sng mang lin nhau khng nn c s dng cc cell cnh nhau vmt a l.

Tuy nhin, trong h thng 3/9 cc cell cnh nhau v mt a l nhA1 & C3; C1 & A2; C2 & A3 li s dngcc sng mang lin nhau.iu ny chng t rng t s C/Ai v i cc my ding hot ng bin gi i giahai cell A1 v C3 l 0dB,y l mc nhiu cao mc d t sny l l n h n t schun ca GSM l (- 9 dB).b. Mu ti s dng tn s4/12

Mu s dng li tn s 4/12 c ngh a l cc tn s s dng c chia thnh 12 nhm tn s n nh trong 4 v tr trm gc. Khong cch gia cc trm ng knh khi l D = 6R.

Cc tn s mu 4/12:n nh tn s

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

BCCH 84 85 86 87 88 89 90 91 92 93 94 95

TCH1 96 97 98 99 100 101 102 103 104 105 106 1

TCH2 108 109 110 111 112 113 114 115 116 117 118 11

TCH3 120 121 122 123 124

Ta thy mi cell c th phn b cc i l 4 sngmang. Nhng phi dnh ra mt khe th i gian cho BCH,mt khe th i gian cho SDCCH/8. Vy s khe th i gian

dnh cho knh lu l ng ca mi cell cn (4 x 8 2) =30 TCH.Trong 12 Cell ca Cluster phi mt 2*12 = 24 knh,

cn li 41*8 24 = 304 knh logic dnh cho traffic.

Hnh 15. M u ti s d ng li t n s 4/12


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V l thuyt, cm 12 cells c t sC/I > 12 dB.y lt s thch h p cho php h thng GSM hot ng tt.Tuy nhin, mu 4/12 c dung l ng thp h n so v i mu3/9 nhng m bo vic n nh tn s sao cho cc sngmang lin nhau khng s dng cc cell cnh nhau v mt a l.c. Mu ti s dng tn s7/21

Mu 7/21 c ngh a l cc tn s s dng c chiathnh 21 nhmn nh trong 7 trm gc. Khong cchgia cc trm ng knh l D = 7,9R.

Cc tn s mu 7/21n nh t n s

BCCH TCHA1 84 105B1 85 106C1 86 107D1 87 108E1 88 109

F1 89 110G1 90 111A2 91 112B2 92 113C2 93 114D2 94 115E2 95 116F2 96 117G2 97 118A3 98 119B3 99 120C3 100 121D3 101 122E3 102 123F3 103 124G3 104

Hnh 16. Cc t n s m u 7/21

Hnh 16. M u ti s d ng t n s 7/21

Ta thy mi cell c th phn b cc i l 2 sngmang. Nhng phi dnh ra mt khe th i gian cho BCH,mt khe th i gian cho SDCCH/8. Vy s khe th i giandnh cho knh lu l ng ca mi cell cn (2 x 8 2) =14 TCH.

Trong 21 Cell ca Cluster phi mt 2*21 = 42 knh,cn li 41*8 42 = 286 knh logic dnh cho traffic.d. Nhn xt

Khi s nhm tn s N gim (21, 12, 9, th khongcch gia cc trm ng knh D sgim 7,9R; 6R; 5,2R.Nh vy, vic la chn mu s dng li tn s phi datrn ccc im a l vng ph sng, mt thu baoca vng phv tng sknh ca mng.

Mu 3/9: s knh trong mt cell l l n, tuy nhin kh nng nhiu cao. M hnh ny th ng c p dng chonhng vng c mt my ding cao.

Mu 4/12: s dng cho nhng vng c mt lul ng trung bnh.

Mu 7/21: s dng cho nhng khu vc mt thp.

2.4. Thay i quy ho ch t n s theo phn b l u l ngS thay i lu l ng v hiu ng im nng

(hotspot) hnh thnh nhu cu tng thm knh tn s mtcell no. Khi ng i ta ngh ngayn kh nng lyknh tn s cell no c lu l ng rt nh thm vocho cell no c lu l ng qu l n. Tuy nhin, vic lmny ph hng quy hoch tn sv mang li can nhiu qumc cho php, gim C/I v C/A nu nh vic thc thikhngng khoa hc.

Mun phn tch chnh xc C/ I, phi k n yu t ahnh thc t. iu ny cn n cng c phn mm cbit x l vn bng my tnh.

Mt trong nhng gii php cho vn ny l cu trcng tm ca cell c tng c ng thm ti tn ly t cell khc. Khi, cc ti tn sn c banu ca cell vn c dng nh vn c, cn ti tn tng c ng c pht

cng sut b h n mc microcell.Cc nhn t khc: Cng c phn mm quy hoch v

tuyn s tnh n nhiu yu t sau y khi chuyn knhtn s:- S khc nhau vcng sut pht v tuyn c cc BTS.- S khc nhau v anten c dng cc c s mt

bng.


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- a hnh thayiV GSM l h thng b gi i hn b i can nhiu, nn

phi xt mu s dng li tn s no c mc can nhiuchp nhn c.Quy ho ch ph sng khng lin t c

Bi ton quy hoch ny phi x l c bit. Tuynhin, c s gii bi ton ny vn l quy hoch tn ssaocho cc t sC/ I v C/ At mc quynh cht l ng.Nhng mu thun pht sinh c th c dung ha tyhon cnh. V d: trong lng x ven quc l c th chuC/ I nh.

Hnh 17. Ph sng khng lin t c

2.5. M t s cng c h tr cng tc t i u

a. MapInfoL phn mm bn tr gip quan st v phn tch h

thng cc Cell, cc trm ca mng thng tin ding.Cung cp mt c s d liu v a hnh,a vt ca khuvc a l phn tch.

Hnh 18. Giao din ca MapInfo.

b. OSS (Operating SubSystem)

L phn mm h tr cho nh khai thc dch v (Operator) tnh nng gim st tnh trng hot ng, vnhnh khai thc ca h thng mng. N cung cp cc giaodin quan st, gim st cu hnh, cnh bo ca h thng. N h tr cho cng tc ti u, thit k h thng..v.v..

Hnh 18. Phn m m h tr khai thc OSS.

Ta ni qua cc giao din quan trng sau:Configuration Management (Qun l c u hnh)

a ra giao din ho quan st cu hnh cc thnhphn trong mng, v d nh cu hnh ca cc Cell trong

mng.

Hnh 19. Giao din Qun l c u hnh mng.


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X l cc cu lnh (Command Handling)L giao din thc hin cc lnh gim st h thng

mng.

Hnh 20. Giao din th c hin cc dng lnh

Alarm (C nh bo)Gim st cc cnh bo v tnh trng hot ng ca cc

thnh phn mng. Nhn voy ta c th thy c ccli c th ca h thng, t a ra cc phn ng thchh p mng hot ng tt h n.

Hnh 21. Giao din hi n th cc cnh bo (Alarm).

c. TEMS Investigation

Cng v i cc cng c khc, my TEMS c s dngth ng xuyn trong vic o v kim tra cht l ng h thng. y l phn mm h tr o c, phn tch chtl ng mng v tuyn. Da vo TEMS ta c thbit cc ng tn hiu, cht l ng tn hiu, Cell phc v vcc Cell ln cn ti mt khu vc kho st. TEMS cungcp cc s kin v cc bn tino c ca h thng gip

phn tch mt cch kh chnh xc cht l ng mng vtuyn ti mt khu vc nht nh.

Hnh 22. Cc c a s giao din ca TEMS Investigation.

Phn tch k t qu o sng pht hin nhi u t n s S dng my TEMS T68i ca Sony Ericsson o

sng pht hin nhiu tn s ti khu th m i PhpVn - H Ni. D i y l ph tn hiu thu c ti khu th m i Php Vn.

Hnh 23. K t qu o sng pht hin nhi u t n

Trn biu ph tn hiu thu c ta thy: mt s v tr c ch s C/ I rt thp, c nhng lc b gim xung

d i 9dB (gi tr C/ I b nht m cht l ng c th chpnhn c theo khuyn ngh GSM ). Mc nhiu ngknh qu cao l nguyn nhn dn n s l ng yu cuHandover tngt bin trong khi mc thu tn hiu vn tt(RxLevel khong -52 dBm). Nhiu tn s xut hin lmcho tn hiu m thoi d b ngt qung, nghe khng r,nh h ng n cht l ng thoi. Nu ko di s lm cucgi b r t mch.


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Kt lun: Mc nhiu ng knh nh vy l v t qumc cho php,iu ny c th l do khi thc hin quyhoch tn s c s khai bo nhm tn s (sau khi kimtra d liu mng cho thy 2 trm BTS ti khu th m iPhp Vn khai bo cng tn s BCCH). Nh vy cnkim tra v tin hnh khai bo li tn s m bo yucu.

3. KT LUNBi bo trnh by khi qut vcc hot ng ti u

trong mng thng tin ding GSM. Tuy bi bo nycha thc s i su, phn tch cc d liu ca mng vtuyn, nhng cng nu vn , t nn tng cho ti umng v tuyn mt cch trc tip hoc gin tip t c trng thi hot ng ca mng v tuyn mt cchtt nht c th. Bi bo cng cp n cc cng vic

kho st, thit k, lp t, vn hnh h thng ... Docth ca mi tr ng truyn dn l v tuyn v do yu cupht trin mng l i lun lun bin ng tng ngy nnti u mng v tuyn l hot ng th ng xuyn, lintc, ko di cng v i s tn ti v pht trin ca h thng.

4. TI LIU THAM KHO[1] Thng tin ding GSM. PTS.Nguyn Phm Anh Dng[2] Tnh ton mng thng tin ding sCELLULAR.

V c Th [3] Th vin Alex. Ericsson.[4] BSS System Description. Alcatel.[5] http://www.vntelecom.net[6] http://www.gsmworld.com

ok giai phap toi uu gsm

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