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CHNG I

Cu 1: Cc c tnh ca h thng thng tin di ng GSM?

S lng ln cc dch v v tin ch cho thu bao c trong thng tin

thoi v truyn s liu.

S tng thch ca cc dch v trong GSM vi cc dch v ca mng

sn c (PSTNISDN) bi cc giao din theo tiu chun chung.

Mt h thng GSM quc gia c th cho nhp mng v qun l mi my

thu bao di ng tiu chun GSM.

T ng nh v v cp nht v tr cho mi thu bao di ng.

linh hot cao nh s dng cc loi my u cui thng tin di ng

khc nhau nh my xch tay, my cm tay, hay my t trn t

S dng bng tn 900 MHz vi hiu qu cao bi s kt hp gia 2

phng php TDMA, FDMA.

Gii quyt s hn ch dung lng, thc cht dung lng s tng ln

nh vic s dng tn s tt hn v k thut nh do vy s thu bao c phc v

cng s tng ln.

Cu 2: Nu v phn tch cc dch v s liu trong GSM?

Truyn dn s liu. Dch v thng bo gn.

Pht qung b trong.

a)Dch v tin nhn ngn SMS

SMS l dch v gip ngi dng c th gi v nhn tin nhn vi cc thu bao

khc trong v ngoi mng GSM. Vi dch v ny thu bao s c c nhng thng

tin nhanh, chnh xc v bo mt.

Dch v bn tin ngn kh ph hp vi mi trng di ng. Cc bn tin ngn divi octet c th c tip nhn bng thit b u cui rt nh.

C hai loi dch v bn tin ngn:

- Dch v bn tin ngn truyn im - im (gia hai thu bao). Loi ny cng chia

lm hai loi:

+ Dch v bn tin ngn kt cui di ng, im - im (SMS - MO/PP): cho

php ngi s dng GSM nhn cc bn tin ngn.

+ Dch v bn tin ngn khi u t Mobile, im - im (SMS MI/PP): cho

php ngi s dng GSM gi bn tin n ngi s dng GSM khc.

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- Dch v bn tin ngn pht qung b: cho php bn tin ngn gi n my di ng

trong mt vng a l nht nh.

b)Dch v Fax-Data

Dch v Fax-Data l dch v gi tr gia tng c cung cp cho khch hng s dng

mng thng tin di ng . s dng c dch v ny bn ch vic kt ni my in

thoi di ng vi mt my tnh xch tay thng qua card Fax-Data (card PCMCIA).

Cc chc nng dch v Fax

Gi v nhn cc bn Fax

Truy nhp vo internet

Gi v nhn e-mail.

c)WAP

L cng ngh c thit k nhm cung cp cho ngi s dng cc thit b u

cui hin i v tch hp cc dch v in thoi vi chc nng tm kim cho php ddng truy nhp Internet t my di ng. WAP l mt giao thc c ti u ho, n

khng ch c s dng cho cc knh v tuyn c bng tn hp ca h thng thng

tin di ng GSM phase 2+ m cn tng thm cc tnh nng v kh nng hin th cho

cc h thng hin th ca cc my di ng ngy nay.

d)Dch v GPRS

GPRS ra i cho php ngi s dng c th truy nhp mng truyn s liu vi tc

ti a c th t ti 171,2 kbit/s. Dch v GPRS em li cho khch hng mt khinim mi v vic truy nhp mng Internet mi lc, mi ni. N cho php tnh cc

thu bao theo s lng cc gi thng tin nhn v gi i ch khng phi tnh cc

bng s thi gian kt ni mng nh trc y. GPRS l bc u tin IP ho cho

mng GSM. Ngoi ra cc thu bao di ng cng c th s dng dch v WAP thng

qua GPRS, nh c GPRS thi gian truy nhp WAP s gim xung, tc gi v

nhn thng tin thng qua giao thc ng dng khng dy WAP cng s c ci

thin rt nhiu.Ngoi ra dch v GPRS cn cho php ngi s dng truy cp internet, gi v

nhn email trn my tnh thng qua my di ng s dng cng ngh GPRS v nhn

tin a phng tin MMS. Vi tc truy cp cao ca cng ngh GPRS khch hng

cn c th ti v my mnh cc ng dng, tr chi, nhc chung a m sc, hnh nh

ng thng qua wap mt cch nhanh chng. Trong tng lai khng xa vi cng

ngh GPRS khch hng cn c th c s dng cc dch v gi tr gia tng khc

trn nn tng mng GPRS sn c nh dch v Streaming Video, Push to talk, chigames trc tuyn...

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e)Dch v MMS

Multimedia Messaging Service (MMS) l mt dch v lu v chuyn tip. Dch

v ny cho php cc thu bao gi cc tin nhn a phng tin ti cc thu bao khc.

Hot ng ca tin nhn MMS tng t nh nhn tin ngn SMS ngoi ra n cn h

tr cc d liu khc nhau trong mt bn tin cc kiu d liu c th gi qua MMS l:

Vn bn

nh mu

m thanh

Video

Tch hp ton b cc thng tin trn

Ngoi ra mi mng GSM cn c cc dch v gi tr gia tng ring nh l: nhc ch

cho ngi gi (ring tunes), 8xxx,1900xxxxx, call me back

Cu 3: Nu cc dch v thoi trong GSM?

Chuyn hng cuc gi v iu kin.

Chuyn hng cuc gi khi thu bao di ng bn.

Chuyn hng cuc gi khi khng tr li.

Chuyn hng cuc gi khi khng n c trm di ng.

Chuyn hng cuc gi khi nghn v tuyn.

Cm tt c cc cuc gi ra.

Cm tt c cc cuc gi ra quc t.

Cm tt c cc cuc gi n.

Cm tt c cc cuc gi n khi lu ng ngoi nc c PLMN.

Gi cuc gi.

i cuc gi.

Chuyn giao cuc gi. Hon thnh cc cuc gi n cc thu bao bn.

Nhm ngi s dng khp kn.

Dch v ba pha.

Thng bo cc ph.

Dch v in thoi khng tr cc.

Nhn dnh ch gi.

Nhn dng cuc gi him th.

Voicemail.

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Dch v gi cuc gi (Call Hold) :Thu bao c th kim sot c hai cuc gi

khc nhau cng mt lc, c th t cuc gi th nht ch ch v thit lp

kt ni vi cuc gi th hai.

Dch v ch cuc gi (Call Waiting): Dch v ny cho bit c cuc gi n

khc khi ngi dng ang ni chuyn vi mt ngi no . ng k dch v

ny, my in thoi di ng s khng bao gi c tn hiu bo bn khi ngi

khc gi n.

Dch v chuyn cuc gi (Call Forwardhay cn gi Call Divert) :l dch v

cho php thu bao chuyn cc cuc gi n s my ca mnh sang mt s

my khc, s my c th l s di ng, s c nh hoc s ca hp th

thoi. Dch v ny li c rt nhiu cc ty chn nh :chuyn cuc gi v iu

kin n s thu bao, chuyn cuc gi khi my bn n s thu bao, chuyn

cuc gi khi ngoi vng ph sng n s thu bao

Dch v chn cuc gi(Call Barring):Cho php thu bao di ng cm cc

cuc gi ra quc t hay cc cuc gi ti cc thu bao ngoi mun ca bn.

C cc ty chn sau:

Chn cc cuc gi ra

+ Tt c cc cuc gi ra

+ Tt c cc cuc gi i quc t

+ Tt c cc cuc gi i quc t tr cc cuc gi v mng thng tr ca thu bao

Chn cc cuc gi n

+ Chn tt c cc cuc gi n

+ Chn cc cuc gi t nc ngoi v

Khng hin th s in thoi gi i (CLIR):Dch v ny cho php thu bao

ch gi khng hin th s ca mnh cho pha thu bao b gi thy.

Dch v chuyn vng quc t (Roaming): Chuyn vng Quc t l mt trong

nhng tnh nng u vit ca h thng Thng tin Di ng Ton cu (GSM).

Mc tiu chnh ca dch v ny l m rng kh nng lin lc ca cc thu bao

GSM trn ton th gii. Hin nay, cng vi xu hng ton cu ho, dch v

Chuyn vng Quc t c s dng rng ri ti hn 135 mng GSM ti

Chu u, Chu , Chu phi v Chu M La Tinh. Dich v Chuyn vng

Quc t l dch v cho php thu bao cc mng GSM s dng in thoi di

ng (TD) ca mnh gi v nhn cuc gi ti tt c cc nc c tha

thun Chuyn vng Quc t vi mng ca nh cung cp m khng cn thayi th SIM v s my TD.

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Dch v gi quc t (IDD): Vi dch v ny khi thu bao c m dch v gi

i quc t khch hng c th d dng thc hin cuc gi hoc nhn tin i quc

t mt cch n gin bng chnh my di ng ca mnh.

Cu 4: Nguyn tc s dng tn s trong h thng GSM?

Ton b di tn pht cho mng GSM 900M ch c t 890MHz n 915MHz tc lc 25MHz, mi knh chim mt khe tn s 200KHz => nh vy c khong 125knh thoi c th s dng mt lc, mi knh thoi c chia thnh 8 khe thi giantrong 1/8 thi gian ginh cho tn hiu iu khin, 7/8 khe thi gian cn li dnhcho 7 thu bao v nh vy tng s thu bao c th lin lc trong mt thi im l125 x 7 = 875.875 thu bao c th lin lc ng thi trong mt thi im cho mt mng di ng,

y l con s qu t khng p ng c nhu cu s dng, v vy ti s dng tn sl phng php lm tng s thu bao di ng c th lin lc trong mt thi im ln

ti con s hng triu .Phng php ti s dng tn s .-Ngi ta chia mt Thnh ph ra thnh nhiu hnh lc gic => gi l Cell , mi c mt trm BTS thu pht tn hiu, cc khng lin nhau c th pht chung mttn s ( nh hnh di th cc c cng mu xanh hay mu vng c th pht chungtn s )- Vi phng php trn ngi ta c th chia ton b gii tn ra lm 3 pht trncc khng lin k nh 3 mu di y, v nh vy mi c th phc v cho 875 /3 = khong 290 thu bao .- Trong mt Thnh ph c th c hng trm trm thu pht BTS v vy n c th

phc v c hng chc ngn thu bao c th lin lc trong cng mt thi im .

Thnh ph c chia thnh nhiu hnh lc gic, mi c t mt trm thu

pht BTS .

Pht tn hiu trong mi

Tn hiu trong mi c pht theo mt trong hai phng php

- Pht ng hng

- Pht c hng theo gc 120o

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CHNG 2

Cu 1: Cu trc ca mng GSM, chc nng cc phn t trong h thng?

Hnh v :

CHC NNG:

Trm di ng MS+ X l truy nhp mng qua giao tip v tuyn

+ Cc giao tip vs ng dng(VD loa, mn hnh,bn phmcho ql ng gi)

+ Cc giao tip vs tb u cui(c th c) nh my tnh c nhn, fax

+ Ch th s b gi

+ Hin th cc tn hiu trong qu trnh gi

+ Chn mng PLMN

+ Giao tip u cui ISDN+ giao tip DTE/DCE

+ ch th v xc nhn cc thng tin ngn

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Phn h v tuyn BSS: thc hin u ni cc MS vs tng i v nh vy

u ni nhng ng sd cc trm di ng vs cc ng sd vin thng khc.

- Trm thu pht gc BTS: chc nng thu pht l chnh

- B iu khin trm gc BSC:

+ qun l cc knh v tuyn v chuyn giao

+ qun l mng v tuyn

+ qun l trm v tuyn gc

+ diu khin ni thng my di ng

+ qun l mng truyn dn

+ dung lng ca BSC

+ cu hnh ca BSC

Phn h chuyn mch NSS: qun l thng tin gia ng sd mng GSM vs

nhau v vs mng khc.

- MSC: thit lp gi v iu khin cuc gi, cc th tc cn thit lm vic vs

cc mng khc(nh PSTN,ISDN) cc th tc lin quan vs ql qu trnh di

ng ca cc trm di ng.

- HLR: lu gi cc thng tin lin quan n vic cung cp cc dv vin

thng.

- AUC: cha cc thng tin v thit b MS(s nhn din phn cng) cho php

MSC nhn bit cc MS hng, mt cp hoc ang gi trm.- VLR: theo di ton b cc MS hin c trong vng MSC, k c cc MS

hot ng ngoi vng qun l HLR

Trung tm vn hnh bo dng OMCoss: pht hin v x l s c.

Ngoi ra 1 s chc nng khc ae t vit thm nh

Cu 2: Cu trc a l ca mng GSM(phn tch s lc)?

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Vng GSM: Gm mt hoc nhiu cc quc gia c cc mng di ng theo

tiu chun GSM.

Vng mng GMSC: Cc vng mng di ng c i din bng tng i

cng (Gateway MSC). Trong mt quc gia c th c nhiu vng mng vin thng,

vic gi vo mt vng mng no phi c thc hin thng qua tng i cng.

Tt c cc cuc gi t mt mng bn ngoi n mng GSM u c nh tuyn

n GMSC. Tng i ny lm vic nh mt tng i trung k gia GSM v mng

ngoi y l ni thc hin chc nng hi nh tuyn cc cuc gi kt cui trm di

ng.

Vng phc v MSC/VLR: Mt mng thng tin di ng c phn chia thnh

nhiu vng phc v nh, mi vng ny c phc v bi MSC/VLR. Vng ny

c qun l bi MSC, nh tuyn n mt cuc gi n mt thu bao di ng,

ng truyn qua mng s ni n MSC vng phc v MSC ni thu bao b gi.

qun l thu bao di ng vng ny c b phn ghi tm thi cc thng tin ca

thu bao nh:

o Thng tin v ng k v cc dch v ca thu bao

o Thng tin v v tr ca thu bao (ang c qun l bi MSC no).

Vng nh v LA: Mi cng phc v MSC/VLR c chia thnh mt s

vng nh v LA (Location Area). Vng nh v l mt phn ca vng phc v y

cc trm di ng c th di chuyn m khng cn cp nht thng tin v v tr cho tng

i MSC/VLR iu khin vng ny. Khi mt thu bao c tm gi mt thng tin

tm gi s c pht qung b cc vng ny tm thu bao ny. H thng c th

nhn dng c vng nh v bng cch s dng nhn dng vng nh v LAI.

T bo (CELL): Mi vng nh v c chia thnh mt s t bo, l vng

bao ph v tuyn, ph sng bi cc trm thu pht gc BTS c nhn dng bng

nhn dng ton cu. Trm di ng t nhn dng mt bng cch s dng m nhn

dng trm gc BSIC.

Cu 3: Chc nng chnh do MSC/VLR v GMSC thc hin?

MSC/VLR thc hin chuyn mch cc cuc gi v to nn im iu

khin cp nht v tr v chuyn giao. MSC ch yu chu trch nhim cho thit lp

cuc gi(bao gm c th tc nhn thc), iu khin cuc gi v tnh cc.

MSC/VLR coi tt c cc thu bao l tm tr MSC cng(GMSC) ni

PLMN. GMSC c phng tin hi, ngha l GMSC c cc chc nng nhn thng

tin t HLR v v tr hin thi ca thu bao. N cng c chc nng nh tuyn li

cuc gi n trm di ng theo thng tin nhn c t vic hi ni trn.

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Cu trc phn cng ca c hai MSC/VLR v GMSC ch yu nh nhau.

Cu 4: Chc nng chnh do HLR/AUC thc hin?

- AUC(Trung tm nhn thc):L mt b phn trong phn cng ca HLR

c nhim v qun l an ton s liu ca cc thu bao c php trong GSM c

nhiu bin php an ton khc nhau trnh vic s dng tri

php, cho php bm v ghi li cuc gi ng v tuyn. Vi mi

mt m thu bao c mt m bo mt ring bit nhm chng li s

nghe trm, m ny c bo v chng mi xm nhp tri php.

- HLR(B ghi nh v thng tr):C s d liu quan trng nht ca

mng di ng s. Cc thng tin lin quan n vic cung cp cc dch v vin

thng c lu gi HLR khng ph thuc vo v tr hin thi ca thu bao. HLR

cng cha cc thng tin lin quan n v tr hin thi ca thu bao.Thng HLR l 1

my tnh ng ring khng c kh nng chuyn mch nhng c kh nng qun l

hng trm ngn thu bao.HLRc s dng theo di MS, l ni thu bao

mua mt ng k t mt hng khai thc GMS m HLR thuc hng

ny. HLR cha thng tin v thu bao nh cc dch v b xung v

cc thng s nhn thc. N cha thng tin v v tr thng tin ca

MS trong mt vng MSC no v thng tin ny thay i th MS

di ng. MS s gi i thng tin v v tr (qua MSC/VLR) n HLR

ca mnh nhm m bo phng tin thu mt cuc gi. Trong

HLR cn thc hin to mt bo hiu s 7 trn giao din vi MSC.

Cu 5: Chc nng ca BSC?

Gim st cc trm v tuyn gc:

Trc khi a vo khai thc BSC lp cu hnh ca trm thu pht (TRX) v cc

tn s cho mi trm BTS. Nh vic ql ny m BSC c th c 1 tp hp cc

knh sn c dnh cho khin ni thng cuc gi.

Qun l cc tim nng BSS.

iu khin ni thng n cc my di ng:

- BSC chu trch nhim thit lp v gii phng cc u ni ti my di ng.

trong qu trnh gi, s u ni c BSC quan st. Cng tn hiu v cht

lng ting c o my di ng v thu pht c gi n BSC. Nh 1 thut ton

BSC quyt nh cng sut pht tt nht ca MS v TRX gim nhiu ca

mng v tng cng cht lng ni thng.

- BSC cng khin qtrnh chuyn giao nh cc kt qu o k trn cho

my chuyn sang khc tt hn.

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nh v v chuyn giao.

Qun l tm gi.

Khai thc v bo dng ca BSS.

Qun l mng truyn dn:

BSC ql cc ng truyn dn t BTS n MSC m bo cho thng tinng v chnh xc. Do n phi lp cu hnh gim st cc lung thng tin

n MSC v BTS. Trong trng hp c s c knh ny th n khin

chuyn mch ti ng d phng.

Chc nng chuyn i m gm c ghp 4 knh lu thng GSM ton tc

vo 1 knh 64kbps.

Qun l mng v tuyn: l qun l cc v cc knh logic ca chng.

Cc s liu qly u c a v BSC o ac x l nh lu lng thng tin 1s ,mi trng v tuyn

Dung lng BSC: c kch c dung lng ty thuc vo lu lng ca cc

ng dng khc nhau

Cu hnh ca BSC: gm thit b v tuyn khin v thit b truyn dn

Cu 6: Chc nng v nhim v ca BTS?(V s v gii thch)

V s khi.

Chc nng:

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Pht qung b c thng tin h thng trn BCCh di s iu khin caBSC.

Ch ra cc knh b kha v gi ti BSC v BSC s sd nhng thng tin ny ch nh knh v tuyn.

Thc hin thut ton nhy tn iu khin cng sut vs s gim st ca BSC Pht li v BSC ch dn ngun v tuyn Bo mt sau khi nhn c m kha ban u ca BSC Tnh ton TA: trm gc nhn c t trm di ng TA hin ti trn knh

iu khin lin kt chm SACCH Pht cc thng tin tm gi trn CCCH. n nh cc knh DCCH di s iu khin ca BSC. Qun l thu pht tn hiu thng tin trn cc knh vt l. M ha, gii m v ghp knh.

Chuyn i m thch ng tc . Nhim v: l phn thu pht v tuyn ca h thng m qua MS c th

lin lc vi h thng. Ti y, cc tn hiu v tuyn c iu ch,khuych i v phi hp thu pht.

Cu 7: Nu v phn tch chc nng chnh ca OMC trong vic qun l mng?OMC l phn no c nhim v g, nm u trong h thng?

Chc nng chnh ca OMC: Thng k cc s kin xy ra trong cc phn t mng. Thu thp v lu gi cc s liu xut hin trong qu trnh khai thc ca cc

phn t mng. Truy nhp cc phn t ca mng t xa bng lnh ngi my. Tip nhn v lu tr cc thng tin trng thi gi ti t cc phn t mng. X l cc thng tin nhn c t trong mng. Qun l s c trn cc phn t ca mng. Qun l sa i cu hnh. Kim sot hot ng ca tt c c phn t trn mng. Qun l thu bao, bo mt cc s liu thu bao. OMC bao gm cho c phn v tuyn v phn chuyn mch, l mt mng

my tnh cc b LAN.Cu 8 Phn bit s ging v khc nhau ca VLR v HLRGing nhau:VLR v HLR u thuc phn h chuyn mch NSS, l ni cha cc c s d liucn thit cho s liu thu bao v qun l di ng ca thu bao . C 2 u lu gi vtr hin thi ca thu bao.Khc nhau :HLR : Cc thng tin lin quan n vic cung cp cc dch v vin thng c lugi HLR ko ph thuc vo v tr hin thi ca thu baob ghi nh v thng

tr. chi tit lin quan n hp ng thu bao ca ngi dng nh cc dch v,identity. N cha thng s Ki dng trong qu trnh bo mt v chng nhn thc.Cc thng tin ny mang tnh permanent.

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VLR : l c s d liu th 2 trong mang GSM, c nhim v lu gi tm thi s liuthu baob gi nh v tm tr hin ang nm trong vng phc v ca MSC tngng v ng thi lu gi s liu v v tr ca cc thu bao vi mc chnh xc hnHLR, VLR cha cc thng tin mang tnh temporal, bao gm cc thng tin lin quann thu bao ( ly t HLR) v v tr chnh xc ca MS trong vng VLR ny (angkt ni vi BSC no...).

CHNG 3

Cu 1: K thut a truy nhp s dng trong GSM l g?

K thut FDMA, TDMA

FDMA: l phng thc phn b u tin v ra i sm nht. Mt thu bao

mun to mt cuc gi s phi nhp s in thoi cn gi v nhn phm gi.

Nu cn dung lng thoi cho t bo, mt cp knh s c phn b cho trm

di ng phc v m thoi - mi knh cho mt chiu thoi. Xt trn mt s

phn b t bo in hnh, s chiu thoi ti a ca mt t bo bt k l

khong 60. R rng l khng th phc v hng triu ngi dng vi mt dung

lng hn ch nh th .

- ph tn s quy nh cho lin lc di ng c chia thnh 2N di tn s k

tip, cch nhau 1 di tn phng v. mi gii tn s c gn cho 1 knh lin

lc, N di k tip dnh cho lin lc hng ln, sau 1 di tn phn cch l N

di k tip cho lin lc hng xung.

- c im:

+ mi MS c cp pht i knh lin lc sut thi gian thng tuyn.

+ nhiu giao thoa do tn s cc knh ln cn nhau l rt ng k.

+ BTS phi c b thu pht ring lm vic vs mi MS trong cellular.

+ dung lng ca h thng b gii hn do b rng bng tn.

TDMA: khc phc vn dung lng knh bng cch chia knh v tuyn

n thnh cc khe thi gian v phn b 1 khe thi gian cho mi thu bao.

V d, h thng TDMA ca Hoa K c 3 khe thi gian trn mi knh trong

khi h thng GSM c 8 khe thi gian trn mi knh. s dng cc khe

thi gian, tn hiu thoi tng t cn c chuyn sang dng s. Mt b

m ho thoi, c gi l vocoder, thc hin cng vic ny. Dung lng

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c c ban u hi nh song vi vic dng cc vocoder tc bt thp,

s knh thoi trn mi knh v tuyn c th c tng ln ng k.

- Trong TDMA, ph tn s quy nh cho lin lc di ng c chia thnh cc

di tn lin lc, mi di tn lin lc ny dc dng chung cho N knh lin

lc, mi knh lin lc l 1 khe thi gian trong chu k 1 khung. Tin tc c

cha di dng gi,mi gi c bt ch th u gi, ch th cui gi, cc bt

ng b, cc bt bo v v cc bt d liu.

- c im:

+ tn hiu ca thu bao c truyn dn s.

+ lin lc song cng mi hng thuc cc di tn lin lc khc nhau.

+ Gim nhiu giao thoa.

+ Gim s my thu pht BTS.

+ pha ing v tr truyn dn l nhng vn k thut ht sc phc tp: giaothoa gia cc tn hiu, mt ng b

Cu 2: Suy hao v pha inh nh hng n h thng GSM nh th no? Nu

cc loi pha inh v suy hao?

1- Suy hao ng truyn v fadinh

- Lm gim cht lng tn hiu, gy ra nhiu dn n tn hiu mong mun qu yu.

- Suy hao ng truyn l qu trnh m tn hiu thu yu dn do khong cchgia trm di ng v gc ngy cng tng.Khng c vt cn gia ta thu c kt

qu:

Ls = d2+ f2 Hay theo [db]

Ls[db]=33,4[db]+20log(f MHz)+20log(d Km)

33,4 l hng s t l .

Vn ny khng l tr ngi h thng v tuyn Cellular. V trc khi mt lin lc

ta phi thc hin mt ng truyn mi qua mt trm gc khc.Tuy nhin t khi s dng trm di ng ca mnh mt mi trng khng c chng

ngi.

Cc chng ngi nh to nh, i ni lm dn n hiu ng che ti v vy lm gim

cng tn hiu thu. Khi di ng cng i di ng cng tn hiu gim v tng

cho d gia anten thu v pht c hay khng c chng ngi. y l mt loi fadinh

lm cho cng tn hin tng gim. Ch gim gi l ch trng ca fadinh. loi

fadinh ny gi l fadinh chun logarit. Loi ny c dng phn b xung quanh mtgi tr trung bnh,nu ta ly log cng tn hiu. Thi gian gia hai ch trng

fadinh thng l vi giy khi di ng lp trn xe v chuyn ng.

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Mt hin tng khc khi mt thu bao my di ng cao hn cc thnh ph. Th

vic s dng trm di ng thnh ph dn n mt hiu ng nhiu c gi l

fadinh nhiu tia hay Raile. Hiu ng ny xy ra khi tn hiu truyn nhiu ng t

anten pht n anten thu.

Tn hiu thu khng c thu trc tip t anten pht Tx m t nhiu phng khc

nhau t cc im phn x , chng hn cc to nh gia cc anten khng c khong

nhn.

Cc tn hiu ny t n trm di ng do nhiu ln phn x t cc to nh ln.

Do vy tn hiu thu l tng ca nhiu tn hiu ging nhau nh khc pha (v khc

bin mc nht nh). Khi ta cng cc tn hiu ny th c th vect tng gn

bng khng ngha l cng tn hiu rt gn khng dn n ch trng fadinh rt

nghim trng .

Khong thi gian gia hai ch trng fadinh ph thuc c vo tc chuyn ngcng nh vo tn s pht. Mt cch gn ng c th ni khong cch gia hai ch

trng gn bng mt na bc sng. di 900 MHz khong 17 cm. Vy nu xe chy

vi vn tc 50Km/h th thi gian ga hai ch trng s nh sau:

V=14m/s =1/3 m T= /2V=12 ms

Mu fadinh ph thuc tn s , mt khong cch nht nh X mt so v Tx. Tn

hiu thu c th nh sau: Cng tn hiu Rx ph thuc khong cch .

Vy nhy ca my thu l tn hiu vo yu nht cn thit cho mi tn hiu ra quinh.

Gi s cn thu X w c th pht hin c thng tin gi t anten Tx. Vy tn

hiu ny phi nh hn X w th mt dn n khng th qui hoch h thng ca mnh

theo gi tr trung bnh chung ca cng tn hiu. Vy phi c mt lng d tr

fadinh t gi tr trung bnh chung n nhy ca my thu bng ch tng ca fadinh

su nht nh hnh trn. Do vy cn phi c cc bin php chng li fadinh

Cc loi pha inh v suy hao: Pha inh chun log:

l hiu ng do mi trng s dng ca MS ca thng c chong ngi

vt gy hiu ng che ti lm gim cng che tn hiu. Khi di

ng cng vi i di ng cng tn hiu gim , tng d gia

TX v RX c hay khng c chng ngi.

Pha inh Raile:

Trong trng hp mi trng thng tin c mt thu bao dy vnhiu chng ngi xy ra khi tn hiu nhiu ng t anten Tx n

Rx.

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hin tng pha inh raile, tn hiu thu c l tng cc tn hiu

phn x khc fa, khc bin . Nhng tn hiu ny khi cng li nh

cc vct to nn mt vct tng gn bng khng c nghi l c-

ng tn hiu bng 0. y l ch trng pha nghim trng.

Suy hao trong khng gian t do:l qu trnh m tn hiu

thu yu dn o khong cch gia trm di ng v trm

gc tng m khng c mt cn gia.

Ls (dB) = 33,4 (dB) + 20logF(MHz) + 20log d(km)

Cu 3: Nu cc phng php phng nga suy hao ng truyn v pha inh?

Phn tp

+ KN: sd 2 knh thu chu nh hng pha inh c lp

+ ch khong cch gia 2 anten

Nu 2 thoai st nhau c th 1 ci k c sng

+ hn ch:

VD thoai ch c 1 anten k khc phc c hin tng thu, sd thm 1 anten thu

theo nh hng pha ing c lp, khong cch 2 anten khong 5,6 m => k/c

hp l c u im hn ch c cng vecto b trit tiu, tng cng tn hiu

ln 6db (vi bng tn 900 MHz), cn vi cc bng tn khc ch tng c 3-4

db

*(Ti Liu tham kho c thi gian th chp)

trnh nguy c c 2 anten thu b ch trng phainh su cng

mt lc, ta s dng 2 anten Rx c lp thu cng tn hiu ri kt

hp cc tn hiu ny li ta s c mt tn hiu ra khi b kt hp t

b phainh hn. Khong cch gia 2 Tx v 2Rx phi ln

khng gian tn hiu 2 anten nh.

15

21

Tn

hiu 1

Tn

hiu 2

CT

HSSAnten


16/55

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phng php m ho knh ta phi pht i mt lng thng tin c s

bit ln hn nhng s t an ton chng li cao hn. M ho knh

c th pht hin v sa li tng bit thu.

Mi knh kim tra li cchia thnh m khi v m xon. m khi,

mt s bit kim tra c b xung vo mt s bit thng tin nht

nh. Cc bit kim tra ch ph thuc vo cc bit thng tin khi

bn tin.

m ho xon, b m ho to ra khi cc bit m khng ch ph

thuc vo cc bit ca khi bn tin hin thi c dch vo b m

ho m cn ph thuc vo cc bit ca khi trc.

M ho khi thng c s dng khi c bo hiu nh hng theo

khi v s dng pht hin li khi thc hin Yu cu t ng

pht ARQ.

M ho xon lin quan nhiu hn n s sai li. C hai m ny -

c s dng GSM. Hai bc m ho c dng cho c ting v s liu.

Nhy tn:

- do pha ing nhiu tia ph thuc vo tn s ngha l ch trng pha ing xy

ra khc nhau vi cc tn s khc nhau.Li dng hin tng ny ta thay

i tn s sng mang sang tn s khc khi ang tin hnh cuc gi. v vy

nu gp ch trng pha ing ch mt 1 phn cuc gi.

- da vo MS, TDMA

M ha knh.

Ghp xen.

Cu 4: Phng php chng phn tn thi gian ^^

Phng php chng phn tn thi gian:

Ta thy phn tn thi gian l nguyn nhn gy ra giao thoa gia cc k hiu

(ISI) nh th no. Cc k hiu phn tn v mt thi gian v cc k hiu cnh nhau

gy nhiu giao thoa ln nhau y l nguyn nhn ca cc kh khn my thu khi ta

c gng quyt nh, xc nh l thng tin no c gi i.

Gia my pht v my thu c lin kt vi nhau bng cc knh,knh c th

l dy dn, quang, v tuyn,.. Mi loi knh c cc nt ring ca mnh lin quan n

rng bng tn, suy hao Ta xt knh nh mt b lc, b lc ny c kch thch

bi mt tn hiu bit trc v sau ta so snh u ra vi u vo bit. Nh vy

nu ta bit tn hiu g c gi i v phn tch tn hiu thu c ta c th tm c

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p ng xung ca knh, v thnh lp m hnh knh. Khi thnh lp c mt m

hnh knh. iu phi lm l to ra tt c cc chui bt c th c v a chng qua

m hnh knh ca ta, chui u vo m t nhn c mt chui u ra ging n

nht .

Ni chung, s nguy him ca phn tn thi gian s tng cng vi khong cch

gia BTS v MS.

Mt s gii php khc phc:

1. Chn v tr t BTS:

Di chuyn BTS n cng gn vt gy phn x cng tt. iu ny s m bo cho

hiu khong cch lun nh nm trong phm vi ca s cn bng.

Chuyn hng anten ca BTS ra khi pha vt chng ngi gy phn x nu

BTS c t xa n. Angten nn c chn c t s tng ch trc trn sau cao.

2. Thay i anten v gc nghing anten:

Nu vt phn x khng b chiu vo th s khng c hin tng phn x. Nh

vy, ta phi c gng gim phn nng lng bc x t vt phn x m c th gy ra

hin tng phn x c hi.

S dng anten down tilt l mt cch c th p dng c. Anten down tilt vi

rng bp sng vo khong 100, c s dng trnh chiu vo nhng vng ni

v trong trng hp cn ph sng cho mt trc ng quc l. Vn chnh khi sdng anten ny l chng phi c lp t tht chnh xc, sai s khng c vt

qu 10.

3. iu chnh tham s cell:

Nu mt vng no trong mt cell c cng tn hiu thp so vi vng

cn li trong cell th cc tham s iu khin chuyn giao nn c thit lp tin

hnh cc cuc chuyn giao ra ngay khi cell ny trc khi my di ng MS i

vo vng nguy him . Cc tham s ca cc cell bn cnh cng nn c thit lp sao cho cc cuc chuyn giao khng b chuyn vo nhng vng c xy ra tn sc

thi gian nm trong cell .

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18/55


19/55

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Ch : Co ny ko nht thit phi = Co n c sd k hiu cc song mang khc

nhau cng 1 . Co c gi l sng mang BCCH, chu k lp li l 51 khung. BTS

lun pht Co MS c th o c cng tn hiu t BTS. Khi ko pht tm gi th

BTS pht cc cm gi thay th CCCH. TSo Co g ln ko cha cc knh ni trn,

n c MS sd truy cp.

Ghp RACH TSo

- TS1 ng xung Co: TS1 c sd xp xp cc knh iu khin ring ln cc

knh vt l chu k lp li 102 khung

- TS1 g ln Co c cng cu trc v y l cc knh ring, ni gp 2 g cho 1 trm

MS 1 thi gian. Tuy nhin thi gian c dch i 15 khung, do m bo MS

thi gian tnh ton tr li ca mnh.- TSo, TS1 g ln v g xung ca Co, nh vy c cc knh iu khin logic

chim, ch cn TS2 n TS7 t do sd cho cc knh TCH.

- Ta xt tt c cc TS Co.

+ TSo: Cc knh iu khin logic, chu k lp li l 51 khung

+ TS1: Cc knh iu khin logic, chu k lp li l 102 khung

+ TS2 n TS7: Cc knh lu lng logic, chu k lp li l 26 khung

- Cc song mang khc t C1 dn Cn-1 dnh cho BTS ch c sd cho TCH ngha lTSo n TS7 u l TCH, ch c 1 Co mi cell. i vi mi song mang b

xung, tt c 8TS c th c sd cho TCH.

Cu 2: o cng in trng c thc hin trm di ng nh th no?

* ch ri: Chn khi bt ngun di ng:

- MS gia 124 knh RF h thng GSM v tnh ton mc trung

bnh cho tng knh, MS iu chnh n sng mang mnh nht

v tm xem n c pht l BCCH hay khng, nu ng th MSc s liu BCCH xem c th kho n ny khng, nu khng

MS s tm n sng mang mnh th hai.

- MS c th c b nh BCCH v n s ch tm cc sng mang ny.

Nu qu trnh khng thnh cng MS thc hin qu trnh 1

BCCH, MS c thng bo cn gim st cc sng mang BCCH no

chn li kho n BTS khc. Nh vy MS trn cp nht danh

sch 6 sng mang mnh nht.*Ch ni thng cuc gi: MS lin tc qua SACCH thng

bo cho h thng cng tn hiu thu t BTS ln cn. BSC s

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dng cc php o ny nhanh chng quyt nh cc ch

khc khi chuyn giao cn thit. Vic o c ln cn thc hin

gia cc khong thi gian pht v thu khe Ts dnh cho trm. C-

ng tn hiu ca mi phc v c gim stkhi thu Ts dnh

cho MS SACCH, cng tn hiu ca cc sng mang BCCH ln l-

t c o theo qui trnh: Pht, o, pht, o,... gi tr trung bnh

tng php o cho tng sng mang c tnh ton v thng bo cho

SBC. cc gi tr o tng ng vi BTS cn o, phi xc nh

nhn dng BTS BSIC pht SCH trn Ts0, Co. Trong thi gian

khung trng (ICLE) TCHC, TDMA-267, BSIC cho BTS ln cn

c.

* Nguyn l o MS:

(1): MS thu v o cng tn hiu

(2): MS Pht

(3): MS o cng tn hiu cho t nht mt ln cn.

(4): MS c BSIC SCH (TS0) cho mt ln cn

MS khng bit khi no xy ra TS0 sng mang BCCH ln cn nu

phi o trong khong thi gian 8Ts chc chn l Tso s xy

ra trong qu trnh o. Vic ny thc hin bng IDLE.

20

IDLE

10 2 7 10 2 7 10 2

10 2 7 10 2 7 10 2

1 2 3 1 2 4

Down link

Up

link

25

2524

24

45 MHz


21/55

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Cu 3: Cc nguyn tc chung ca bo hiu s 7?

Bo hiu knh chung s 7 (CCS7) l mt phng php thng bo gia

cc h thng c iu khin bng my tnh(cc chuyn mch ting/s

liu). bo hiu l 1 phn quan trng ca in thoi v bo hiu gia cc

chuyn mch mang thng tin nh chim, gii phng cc mch trung k,

cc ch s ca thu bao B Phng php thng thng cho bo hiu

c gi l bo hiu tng knh v phng php ny knh bo hiu phi

cng mt ng vi knh ting.

Bo hiu knh chung c 1 mng bo hiu hon ton cch bit vi mng

ting. cc nt chuyn mch thng tin cho nhau v cc knh ting mng

CCS. Mng CCS l mt h thng s tc cao cho php mt knh chung

phc v 5000 cuc ni thng ting. v th ta s thy mt nhn c gn

cho tng tn hiu ch th ni thng ting m tn hiu ny phi th hin.

cc u im khc l dung lng, tc cao, thi gian thit lp ngn v

tin cy cao.

Cu 4: Bo hiu gia BSC v BTS, v bin bn LAPD l g?

C hai loi knh thng tin gia BSC v BTS:

Knh thng tin tc 64kbps mang ting v d liu cho cc knh v

tuyn.

Cc knh bo hiu tc 64kbps magn thng tin tn hiu hoc cho bn

thn BTS hoc cho MS, c pht mt trong cc knh v tuyn.

Cc ng logic gia BSC v BTS c giao tip Abis. Giao tip ny gm 3

lp OSI.

Lp 1 l lp vt l, chu trch nhim truyn dn vt l cc s 0 1 trong

mi trng v cha cc qui nh v kch thc, hnh dng cc xung.

Lp 2 l lp LAPD.

Lp 3 l lp BTSM.

Giao thc LAPD: cung cp 2 loi tn hiu. chuyn thong tin khng cng nhn

vi khng m bo l khung thng tin c a n ngi nhn thnh cng.

Chuyn thng tin cng nhn trong mi tn hiu u c cng nhn v h

thng khng nh l khung t n ni nhn mt cch thnh cng. Thng

tin do lp 3 cung cp c lp 2 bin i thnh cc khung LAPD.

Cu 5: Giao thc LAPDm? c sd ch no trong h thng?

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LAPDm l bin bn truyn thng tin gia MS v BTS s dng knh

Dm. LAPDm th hin lp OSI 2 v khng ph thuc vo tc bit. C hai

loi khai thc c m bo bi LAPDm:

Khai thc khng cng nhn.

Khai thc c cng nhn.

LAPDm t hai lp trong m hnh OSI. Nhng

ngi s dng t trn lp

LAPDm lp 3 (xem hnh sau).

LAPDm c iu khin bng mt khi phn mm gi l

khi s l knh khng gian ALH v LAPDm, chng cng x

l tt c bo hiu ca giao din khng gian. Chng trnh

ca ALH s c t TRxc (b iu khin thu pht),

y l b x l BSS. Khun dng tin bo LAPDm rt

ging khun dng tin bo LAPD.

trng a ch, khi nhn dng im truy nhp dch

v SAPI c th c hai gi tr khc nhau.

+ SAPI = 0 ch th rng tin bo hoc cha s liu hoc

cha tin bo in thoi.

+ SAPI = 3 ch th bn tin bo.

Cu 6: Nguyn l o cng trng MS?(Ging cu 2) o lng tn hiu trong ch ri: Trong ch ri MS lun thong bo

trn knh iu khin v o lng tn hiu cc sng mang cn thit. Khi m

22

Cc ngi sd

Khi ql ALH LAPDm

Cc tn hiu a qua truyndn

Lp3

Lp 2

Lp 1

LAPDm theo m hnh OSI


23/55

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my, MS s qut tt c cc sng mang trong mng MS v tm sng mang

c tn hiu mnh nht. y chnh l sng mang Co ca t bo m MS hin

din. Trn sng mang ny MS s cp nht 6 sng mang ca cc MS ln

cn.

o lng tn hiu trong qu trnh lin lc: trong qu trnh lin lc, MS lin

tc o v thng bo qua knh SACCH c gn lin vs knh TCH cho bit

cng tn hiu thu c t cc BTS ln cn. kt qu o lng s c BTS

x l qnh chuyn vng cho MS khi cn thit. vic o lng c thc

hin gia cc khe thi gian (ko thu pht)

Quy trnh thc hin :pht-o-thu-pht-thu

Tr 3 khe thi gian

Qu trnh khe thi gian th 2(xung): thu

Qu trnh khe thi gian th 3(2 ln): MS pht tn hiu, qtrnh la MS

o cng tn hiu cc BTS ln cn.

khe thi gian th 2 n khe thi gian ca khung tip theo MS c tn

hiu ng b cho cell cn o.

Cu 7: Nu v phn tch khi nim knh logic?

Knh logic c t chc trn quan im ni dung tin tc, c trng cho

thng tin truyn gia MTS v MS. Cc knh ny c t vo knh vt l.

C th chia cc knh logic thnh 2 loi tng qut:

+ knh lu lng TCH : mang ting c m ha hoc s liu ca ng sd.

TCH c 2 loi:

-knh ton tc TCH/F: mang thng tin ting hoc s liu tc khong

22,8 Kbit/s

-knh bn tc TCH/H: mang thng tin tc khong 11,4 Kbit/s

+ knh bo hiu iu khin: mang tn hiu bo hiu hay s liu ng b.c 3 loi knh iu khin:

-knh iu khin qung b BCH :

# cc knh hiu chnh tn s (FCCH): mang thng tin hiu chnh tn scho cc trm MS. FCCH ch c sd ng xung.# knh ng b (SCH): mang thng tin ng b khung cho MS v nhndng BTS. SCH ch sd cho ng xung.

# knh iu khin qung b (BCCH): pht qung b cc thng tin chungv . Cc bn tin ny gi l thng tin h thng. BCCH ch sd cho ngxung.

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-knh iu khin chung CCCH:# knh tm gi (PCH): knh ny c sd cho ng xung tm trm ding.# knh thm nhp ngu nhin (RACH): knh ny c MS sd yu cudnh cho 1 knh SDCCH.

# knh cho php thm nhp (AGCH): knh ny ch c sd ng xung ch nh 1 knh SDCCH cho MS.-knh iu khin ring DCCH:# knh iu khin dnh ring ng 1 mnh (SDCCH): ch sd dnh ringcho bo hiu vs 1 MS. SDCCH c sd cho cc th tc cp nht v trong qutrnh thit lp cuc gi trc khi n nh knh TCH. SDCCH sd cho cng xung v ln.# knh iu khin lin kt chm (SACCH): knh ny lin kt vs 1 TCH

hay 1 DSCCH. y l 1 knh s liu lin tc nh: bn bo co v olng, nh trc thi gian v iu khin cng sut. SACCH sd cho cng ln v ng xung.# knh iu khin lin kt nhanh (FACCH): knh ny lin kt vs 1 TCH.FACCH lm vic ch ly cp = cch thay i lu lng ting hay sliu = bo hiu.

Cu 8: Nu v phn tch khi nim knh vt l?

Knh vt l l mt khe thi gian ca 1 khung TDMA 1 tn s dnh truyn ti thng tin ng v tuyn ca GSM.

Mi khung gm 8 khe thi gian

Nh vy c 8 knh vt l trn 1 sng mang GSM

Thng tin pht i 1 TS c gi l cm

i vs h thng GSM di tn s quy nh :+ ng ln: 890-915 MHz (t MS n BTS)

+ ng xung: 935-960 MHz (t BTS n MS) Di thng tn 1 knh vt l (1 sng mang) l 200 KHz, di tn bo v cng

rng 200KHz

GSM 900 c 124 sng mang v 992 knh vt l

Mi knh tn s v tuyn c t chc thnh cc khung TDMA c 8 khe thigian.mi khe thi gian c lu 577ms. BTS tt c cc khung TDMA tt c cc knh tn s trn ng xung c ng b. tuy nhin khi u

ca khung TDMA ng ln tr 1 khong thi gian c nh 3 khe. L dotr cho php MS sd cng 1 khe thi gian c ng ln ln ng

24


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xung m khng cn phi thu pht ng thi. ngi ta gi khun mu tintc 1 khe thi gian l 1 cm. c cc loi cm khc nhau:+ cm bnh thng NB+ cm hiu chnh tn s FB+ cm ng b SH

+ cm truy cp AB+ cm b nhn DB

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CHNG 5

Cu 1: MSISDN, IMSI, MSRN l g? V sao chng li c 2 tn s/ nhn dng

(IMSI, MSISDN) khc nhau?

MSISDN: l mt s nhn dng duy nht ca mt thu bao di ng k

hoch nh s mng in thoi chuyn mch cng cng.

IMSI: l thng tin nhn dng duy nht mt thu bao cho GSM

PLMN.

MSRN: l s lu ng ca trm di ng c GMSC s dng nh

tuyn mt cuc gi n trm di ng.

MSISDN: (s mng lin kt a dch v ca trm di ng)

Theo khuyen ngh ca CCITT, s in thoi hay s danh b in

thoi ca my ny bao gm:

CC NDC SN

MSISDN=CC+NDC+SD

CC= m nc, NDC= m nI nhn quc gia, SN=s thu bao

S MSISDN quc t c chiu di thay i. Chiu di cc i ca

n l 15 ch s khng k cc tin t

MSISDN l mt s nhn dng duy nht 1 thu bao in thoi di

ng trong k hoch nh s ca mng in thoi chuyn mch

cng cng.

Mi thu bao c lin kt vi b ghi dch thng tr HLR. di ca

MSISDN ph thuc vo cu trc v k hoch nh s ca tng nha

khai thc theo khuyn ngh ca ITU-TE.164

Nhn dng thu bao di ng quc t IMSI

nhn dng chnh xc ng truyn cng nh trn ton mng

GSM, mi thu bao c n nh mt s nhn dng c th. S

nhn dng ny gi l nhn dng thu bao di ng quc t IMSI v

c s dng cho ton b bo hiu trong mng di ng GSM. S

ny c lu tr moun nhn dng thu bao SIM cng nh HLR

IMSI = MCC+MNC+MSIN

MCC= m nc di ng, MNC= m mng di ng ,MSIN=s nhn

dng trm di ng

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IMSI l thng tin nhn dng duy nht mt thu bao di ng thuc

mng GSM

Theo khuyn ngh GSM, IMSI c di cc i 15 ch s

Ton b thng tin v thu bao lin quan n mng u lin kt

vi IMSI

S lu ng ca trm di ng MSRN

HLR bit thu bao di ng thuc vng phc v MSC/VLR no.

cung cp s tm thi cho vic nh tuyn HLR yu cu MSC/VLR

ang phc v thu bao di ng gi n nh mt s lu ng ca

trm di ng cho thu bao ny v gi cho n

Khi thu c MSRN, HLR gi n n MSC cng n ng tuyn

cuc gi n MSC/VLR ang phc v thu bao b gi

S lu ng ca trm di ng bao gm:

MSRN=CC+NDC+SN

CC=country code (m nc), NDC nationnal destination code (m nI

nhn quc gia),

SN=subscriber number(s thu bao)

Chng ta c 2 s nhn dng (IMSI, MSISDN) khc nhau

- MSISDN l mt s nhn dng duy nht 1 thu bao in thoi ding trong k hoch nh s ca mng in thoi chuyn mch

cng cng.

- IMSI l thng tin nhn dng duy nht mt thu bao di ng thuc

mng GSM

Cu 2: Nu cc trng hp chuyn giao?

a) Chuyn giao trong vng 1 BSC:Trong qua trnh goi MS luon luon o cng o trng, chat

lng kenh TCH cua mnh va cng o cua cac o lan

can. MS anh gia tr trung bnh cua ket qua o. Hai lan

trong mot giay no gi bao cao ket qua o (1) en BTS

cung vi ket qua o cua cac o lan can tot nhat. BTS

bo sung them ket qua o c chnh kenh TCH va gi

bao cao ve BSC (2). BSC chc nang nh v c tchcc e quyet nh xem co can chuyen giao cuoc goi en

o khac do chat lng xau hoac nhieu ln o ang phuc

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vu hay khong.

- Trng hp can chuyen giao BSC se lenh chon BTS

o mi c cho tch cc mot kenh TCH (3) va lenh cho BTS

nay gi ban tin en MS thong bao ve tan so va khe

thi gian can chuyen en (4).

- MS ieu chnh en tan so mi va gi ban tin tham

nhap chuyen giao (HO) khe thi gian tng ng (5). MS

khong s dung bat ky s nh thi trc nao ca, v vay

cum HO la cum rat ngan ch cha 8 bit thong tin. MS

khong nhan c bat c thong tin nao ve nh thi

trc cho en khi BTS phat hien ra cum HO.

- MS cung nhan thong tin ve cong suat can s dung (6)

kenh FACCH lay cap t kenh tieng (c lay cap trong

tng trng hp nay lap 1).

- BSC se nhan c thong tin t BTS la chuyen giao thanh

cong sau khi MS gi ban tin hoan thanh chuyen giao (7).

ng tieng trong chuyen mach nhom thay oi va BTS cu

c ra lenh thao g TCH cu cung vi kenh lien ket SACCH

(8).

- chuyen giao ben trong BSC nay chnh BSC x ly moiviec khong co s can thiep cua MSC. MSC ch c thong

bao ve viec thc hien chuyen giao.

b) Chuyn giao gia 2 thuc 2 BTS khc nhau:- BSC cu da tren cac bao cao ve ket qua o quyet

nh chuyen giao en o mi trc thuoc mot BSC khac.

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BSC cu (ang phuc vu) gi ban tin "yeu cau chuyen giao"

cung vi nhan dang o mi (1) en MSC.

- MSC biet BTS ieu khien o nay, no gi yeu cauchuyen giao en BTS nay (2)

- BSC lenh cho BTS mi kch hoat mot kenh TCH neu con

kenh roi (3).

- Khi BTS a kch hoat kenh TCH, no gi thong tin ve khe

thi gian va tan so en MSC (4).

MSC chuyen thong tin nay en BSC cu (5).

- MS c ra lenh chuyen en TCH mi (6).- MS gi i cum tham nhap chuyen giao (HO) TCH mi

(7).

- Ngay sau khi phat hien cum HO, BTS gi thong tin vat

ly cha nh trc thi gian va cong suat ra en MS (8).

- BSC mi nhan c thong tin rang BTS a nhan c

cum HO (9), no thong bao ieu nay qua MSC (10) en BSC

cu (11).

- MSC chuyen thong tin noi tren en BSC cu (11).

- BTS cu giai phong TCH va SACCH cu (12).

- MS nhan thong tin ve o mi SACCH lien ket vi TCH

mi. Neu o nay thuoc LAI mi MS phai cap nhat v tr bnh

thng sau khi cuoc goi c giai phong.

c) chuyn giao gia cc thuc tng i khc nhau

- BSC ang phuc vu gi "yeu cau chuyen giao" en MSC

giong nh trng hp tren (1).

- MSC yeu cau MSC chuyen giao (MSC ch) (2) giup .

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MSC ch cap phat mot so chuyen giao (so ien thoai

thong thng) e nh tuyen lai cuoc goi.

- Yeu cau chuyen giao c gi en BSC mi (3).

- Neu co kenh TCH roi, BSC yeu cau BTS kch hoat mot

TCH (4).

- MSC nhan c thong tin ve kenh TCH mi (5) va

chuyen thong tin nay tr lai MSC cu cung vi so chuyen

giao (6).

- ng truyen c thiet lap en MSC mi (7).

- Lenh chuyen giao c gi en MS cung vi thong tinve tan so va khe thi gian se c s dung o mi(8).

- MS phat i cum HO (chuyen giao) TCH mi (9).- Mot ng mi c thiet lap chuyen mach nhomva cuoc goi c chuyen mach (11).

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- TCH va SACCH cu c giai phong.Tong ai MSC goc van duy tr s kiem tra chnh cuoc goicho en khi no c xoa. MSC nay c goi la MSC neo.Giao thc MAP c thc hien gia cac MSC.Khi di chuyen vao vung nh v mi th sau khi giai phong

cuoc goi no phai thc hien cap nhat v tr. Do mot vungnh v khong the trc thuoc hai MSC nen trng nayphai thc hien cap nhat v tr sau khi cuoc goi c giaiphong. HLR se c cap nhat va gi ban tin en VLR cu,MSC nay phai xoa tat ca cac thong tin lien quan enthue bao.

Cu 3: Th no l Roaming, Handover? Phn tch?

Roaming: kh nng chuyn ng vo nh ng thi vi vic thay i nithng MS giao tip v tuyn, thi im cn thit m bo chtlng thu c gi l lu ng(Roaming).

Handover: l qu trnh chuyn sang mt knh thng tin mi trong qutrnh thit lp cuc gi trng thi bn.

- Chuyen giao la qua trnh xay ra khi lu lng cuaMS c chuyen t mot kenh TCH nay sang mot

kenh TCH khac trong qua trnh goi. Co 2 loai chuyengiao:

+ Chuyen giao ben trong o

+ Chuyen giao gia cac o

Chuyen giao gia cac o c phan loai thanh:

Chuyen giao gia cac o thuoc cung mot BSC:

chuyen giao nay do BSC ieu hanh.

- Chuyen giao gia cac o thuoc hai BTS khacnhau: chuyen giao nay lien quan en cac tong ai

MSC quan ly hai BTS.

- Chuyen giao gia hai o thuoc hai tong ai MSC

khac nhau: chuyen giao nay lien quan en ca hai

tong ai phu trach cac o noi tren.

- Trong trng hp chuyen giao nhieu lan gia hai

o thuoc hai MSC khac nhau, tong ai MSC au tienphu trach MS c goi la tong ai qua giang v

cuoc goi luon luon c chuyen mach qua tong ai

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nay. Lan chuyen giao gia hai o thuoc hai tong

ai khac nhau th nhat c goi la chuyen giao

gia cac o thuoc 2 tong ai lan au, con cac

lan sau c goi la chuyen giao gia cac o thuoc

hai tong ai tiep theo.

Roaming( lu ng )

Khi MS ang trng thi bt my v chuyn ng theo mt phng lin tc,

n c kha n mt tn s v tuyn nht nh c CCCH v BCH khe thi

gian TS0. Khi ri xa BTS ni vi n, cng tn hiu thu c s gim dn.

mt im gn bin gii l thuyt gia hai , cng tn hiu thu c

gim n mc m MS quyt nh chuyn sang tn s mi thuc mt trong

cc ln cn, c cng tn hiu ln hn so vi khi n tn s c. Sau

MS li tip tc nghe cc thng bo tm gi v cc thng tin h thng.Quytnh v vic thay i tn s v tuyn ca MS khng cn thng bo cho mng

tr khi tn s c v mi khng thuc vng nh v LA.MS nhn bit iu ny

khi tm hiu s nhn dng vng nh v LAI trong thng tin h thng pht trn

cc knh BCH. Khi MS s thm nhp vo mng cp nht v tr.C hai

trng hp phi cp nht v tr l:

+ Di chuyn gia cc vng nh v khc nhau ca MSC/VLR.

+ Di chuyn gia hai vng phc v MSC/VLR.Cu 4: Trnh by th tc nhp mng ng k ln u?

Khi MS bt my n s qut giao tip v tuyn tm ra

tn s ng, tn s m MS tm kim s cha thng tin

qung b cng nh thng tin tm gi BCH/CCCH c th c.

MS t kho n tn s ng nh vic hiu chnh tn s

thu v thng tin ng b

V y l ln u MS s dng nn phn mng chu trchnhim s l thng tin ti / t MS hon ton khng c thng

tin v MS ny, MS khng c ch th no v nhn dng

vng nh v mi . Khi MS c gng thm nhp ti mng v

thng bo vi h thng rng n l MS mi vng nh v

ny bng cch gi i mt thng bo Cp nht v tr

mng n MSC/VLR.

T gi tr i MSC/VLR s coi rng MS hot ng v nhdu trng d liu ca MS ny bng 1 c nhp mng co

ny lin quang n IMSI.

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K hiu:

(1): cp nht v tr (LAI mi)

(2): y/c cp nht v tr (IMSI MSC mi)

(3): chp nhn cp nht v tr

(4): cng nhn cp nht v tr

Cu 5: trnh by cuc gi ca MS?

Tm gi:

Cuc gi n MS oc nh tuyn n MSC/VLR ni MS ng

k. Khi MSC/VLR s gi i mt thng bo tm gi n MS,

thng bo ny c pht qung b trn ton b vng nh v LA

ngha l tt c cc BTS trong LA s gi thng bo tm gi MS. Khichuyn ng LA v nghe thng tin CCCH MS s nghe thy

thng bo tm gi v tr li ngay lp tc.

* Gi t MS:

Gi s MS ri v mun thit lp mt cuc gi thu bao ny s quay

tt c cc ch s ca thu bao b gi v bt u th tc ny

bng cch n phm pht . Khi ny MS gi i mt thng bo

u tin n mng bng CCCH yu cu thm nhp . Trc htMSC/VLR s ginh ring cho MS mt knh ring , kim tra th loi

ca thu bao b gi v nh du thu bao ny trng thi bn .

Nu thue bao gi c php s dng mng MSC/VLR s cng nhn

yu cu thm nhp . By gi MS s gi i mt thng bo

thit lp cuc gi , tu theo thu bao b gi l c nh hay di

ng s ca n s c phn tch trc tip MSC?VLR hoc gi

n mt tng i chuyn tip ca mng PSTN c nh . Ngaykhi ng ni n thu bao b gi sn sng thng bo thit

lp cuc gi s c cng nhn, MS cng s c chuyn n mt

knh thng tin ring. By gi tn hiu cui cng s l s khng

nh thu bao.

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Gi n thu bao MS:

Gi s c mt thu bao A thuc mng c nh PSTN yu cu

thit lp cuc gi vi thu bao B thuc mng di ng.

- Thu bao A quay m ni nhn trong nc t ti vng

GSM/PLMN. Ni thng c thit lp t tng i ni ht ca thu

bao A n GMSC ca mng GSM/PLMN.

- Thu bao A quay s ca thu bao B, so thu bao c phn tch

GMSC. Bng chc nng hi p GMSC gi MSISDN cng vi yu

cu v s lu ng (MSRN) n b ghi nh v thng tr (HLR)

- HLR nh s thu bao ca MS c quay v nhn dng

GSM/PLMN

MSISDN IMSI

- HLR ch cho MS vng phc v v

gi IMSI ca MS n VLR ca vng

phc v ng thi yu cu v

MSRN.

- VLR s tm thi gn s lu ng

MSRN cho thu bao b gi v gi

n ngc tr v HLR, HLR s gi n

v tng i cng GSMC.

- Khi nhn c MSRN ng tng

i GMSC s c kh nng thit lp cuc gi n vng phc v

MSC/VLR ni thu bao B hin ang c mt.

- VLR s ch cho thu bao ny vng nh v (LAI) giai on qu

trnh thit lp cuc gi h thng mun rng thng bo tm gi

thu bao b gi c pht qung b trn vng ph sng ca tt c

cc ca vng nh v ny. V vy MSC/VLR gi thng bo tm

gi n tt c cc BTS trong vng nh v.

- Khi nhn c thng tin tm gi, BTS s pht n ln ng v

tuyn knh tm gi PCH. Khi MS trng thi ri v nghe knh

PCH ca mt trong s cc thuc vng nh v LA, n s nhn

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thng tin tm gi , nhn bit dng IMSI v gi tr li v thng bo

tm gi.

- Sau cc th tc v thit lp cuc gi v sau khi gn cho mt

knh thng tin cuc gi ni trn ddc ni thng n MS knh v

tuyn.

*Cuc gi khi xng t MS

- qu trnh nhn thc c thc hin (3)

-Qua trnh ma hoa c thc hien (4)

-MSC nhan c ban tin thiet lap t MS co cha thong

tin ve loai dch vu ma MS yeu cau, so thoai b goi B (5).

MSC kiem tra la MS khong co cac dch vu cam goi ra

(dch vu nay co the kch hoat hoac bi thue bao hoacbi nha khai thac). Neu khong b cam goi ra qua trnh

thiet lap cuoc goi c tien hanh. Gia MSC va BSC

ng truyen c thiet lap va kenh lu lng c

chiem. MSC gi yeu cau en BSC e an nh mot kenh

lu lng cho ng vo tuyen.

- BSC kiem tra neu co kenh lu lng roi no an nh

kenh nay cho cuoc goi va yeu cau BTS kch hoat kenhnay. BTS gi tra li cong nhan khi viec kch hoat kenh lu

lng a hoan thanh (6). BSC thong bao cho MSC ve s

hoan thanh nay. He thong con ieu khien lu lng se

phan tch cac ch so cua so thoai B va thiet lap ket noi

en thue bao b goi. Cuoc goi c noi thong qua chuyen

mach nhom.

Bao chuong se c gi en tram MS (7) cho thay rang

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pha b goi ang o chuong. Tong chuong c tao ra

tong ai pha thue bao B va c gi qua chuyen mach

nhom en MS. Nh vay tong chuong c gi qua ng

vo tuyen ch khong tao ra MS.

- Khi thue bao B tra li mang gi ban tin ket noi en

MS thong bao rang cuoc thoai c chap nhan (8). MS tra

li bang cong nhan ket noi, nh vay thiet lap cuoc goi

a hoan tat.

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Cu 6: My thoi GSM qut v iu chnh n 1 trm gc nht nh ntn?

Qut ln lt 124 tn s.

Cht li 1 tn s.

Khi MS bt my n s qut giao tip v tuyn tm ra tn s

ng, tn s m MS tm kim s cha thng tin qung b cng

nh thng tin tm gi BCH/CCCH c th c. MS t kho n tn s

ng nh vic hiu chnh tn s thu v thng tin ng b

V y l ln u MS s dng nn phn mng chu trch nhim

s l thng tin ti / t MS hon ton khng c thng tin v MS ny,

MS khng c ch th no v nhn dng vng nh v mi . Khi MS

c gng thm nhp ti mng v thng bo vi h thng rng n l

MS mi vng nh v ny bng cch gi i mt thng bo Cp

nht v tr mng n MSC/VLR.

T gi tr i MSC/VLR s coi rng MS hot ng v nh du trng

d liu ca MS ny bng 1 c nhp mng co ny lin quang

n IMSI.

Th tc ri mng lin quan n IMSI. Th tc ri mng ca IMSI cho

php thng bo vi mng rng thu bao di ng s tt ngun , lc

ny tm gi MS bng thng bo tm gi s khng xy ra.

Mt MS trng thi hot ng c nh du l nhp mng.

Khi tt ngun MS gi thng bo cui cng n mng ,thng bo

ny cha yu cu th tc ri mng. Khi thu c thng bo ri mng

MSC/VLR nh du c IMSI ri mng tng ng.

* Tm gi:

Cuc gi n MS oc nh tuyn n MSC/VLR ni MS ng

k. Khi MSC/VLR s gi i mt thng bo tm gi n MS,

thng bo ny c pht qung b trn ton b vng nh v LA

ngha l tt c cc BTS trong LA s gi thng bo tm gi MS. Khi

chuyn ng LA v nghe thng tin CCCH MS s nghe thy

thng bo tm gi v tr li ngay lp tc.

Cu 7: my thoi GSM o cng tn hiu t cc trm gc bn cnh ntn?

Trong qu trnh ca mt cuc gi tram di ong lien tuc bao cao

cng o tn hieu cua cac BTS lan can cho he thong. o

cng o tn hieu cua cac BTS lan can c tram di

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khung ung cha BSIC ch la 10%. e giai quyet van e

nay cac a khung TCH trt so vi cac a khung TCH cha

26 khung IDLE se trt len tat ca cac kenh ieu khien

TS0 va cuoi cung no se gap c SCH.

Hnh cho thay qua trnh c goi la a khung trt. Hai mui

ten s o anh dau hai trng hp khung IDLE a

khung TCH gap SCH a khung ieu khien. Lu y rang

cuoi a khung ieu khien SCH khong xuat hien 10 khung

mot lan v ay moi khung IDLE c a vao, v vay

trong trng hp xau nhat viec xac nh BSIC rat tre.MS

phai co kha nang giai quyet ma BSIC cho 6 o manh

nhat trong 10 giay tham ch trong trng hp xau nhat

oi vi 6 o lan can MS van phai ma tat ca 6 BSIC trong

10 giay.

CHNG 6

Cu 1: Khi thit k h thng Cellular l lm sao c th t c dung lng cholu lng cao? (Phn tch)

Ti s dng tn s

3 kiu mu sd li tn s thng dng l: 3/9, 4/12, 7/21a) Mu ti sd tn s 3/9

Mu ti sd tn s 3/9 c ngha l cc tn s sd c chia thnh 9 nhm tn sn nh trong 3 v tr trm gc.mu ny c k/c gia cc trm ng knh la D= 5,2R.Cc tn s mu 3/9 (gi thit c 41 bng tn chung 41*0.2 MHz= 8,2 MHz sdtrong mng GSM 900 ca VMS). Ta thy mi cell c th phn b cc i n 5sng mang. Nhng phi dnh ra 1 khe thi gian cho BCH, 1 khe thi gian choSDCCH/8. Vy s khe thi gian dnh cho knh lu lng ca mi cell cn (5 x 8-2) = 38 TCH. Trong 9 cell ca cellular phi mt 2*9 = 18 knh,cn li 41*8-18=310 knh logic dnh cho traffic. Theo l thuyt, cu trc mng 9 cells c t sC/I > 9 dB m bo GSM lm vic bnh thng.T s C/A cng l 1 t s quan trng v ngi ta cng da vo t s ny m borng vic n nh tn s sao cho cc sng mang lin nhau ko nn c sd cc cellcnh nhau v mt vt l.tuy nhin, trong h thng 3/9 cc cell cnh nhau v mt al nh A1 & C3; C1 & A2; C2 & A3 li sd cc sng mang lin nhau. iu ny

chng t rng t s C/A vi cc my di ng hot ng bin gii gia 2 cell A1v C3 la 0 dB, y l mc nhiu cao mc d t s ny l ln hn t s chun caGSM l (-9 dB)

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b) Mu ti sd tn s 4/12Mu ti sd tn s 4/12 c ngha l cc tn s sd c chia thnh 12 nhm tn s n

nh trong v tr trm gc. k/c gia cc trm ng knh khi l D = 6R.ta thy micell c th phn b cc i l 4 sng mang. Nhng phi dnh ra 1 khe thi gian choBCH, 1 khe thi gian cho SDCCH/8. Vy s khe thi gian dnh cho knh lu lng

ca mi cell cn (4x8-2)= 30 TCH. Trong 12 cell ca cellular phi mt 2*12 = 24knh, cn li 41*8-24 = 304 knh logic dnh cho traffic.V l thuyt,cm 12 cells c t s C/I>12 dB. y l t s thch hp cho php hthng GSM hot ng tt. tuy nhin, mu 4/12 c dung lng thp hn so vsmu 3/9 nhng m bo vic n nh tn s sao cho cc sng mang lin nhau kosd cc cell cnh nhau v mt a l.c) Mu ti sd tn s 7/12

Mu ti sd tn s 7/12 c ngha l cc tn s sd c chia thnh 21 nhm n

nh trong 7 trm gc. k/c gia cc trm ng knh l D = 7,9R. ta thy mi cellc th phn b cc i l 2 sng mang. Nhng phi dnh ra 1 khe thi gian choBCH, 1 khe thi gian cho SDCCH/8. Vy s khe thi gian dnh cho knh lulng ca mi cell cn (2x8-2)= 14 TCH. Trong 21 cell ca cellular phi mt2*21 = 42 knh, cn li 41*8-42= 286 knh logic dnh cho traffic.

Nhn xt:Khi s nhm tn s N gim (21, 12, 9) th k/c gia cc trm ng knh D

s gim 7,9R; 6R; 5,2R. nh vy, vic la chn mu sd li tn s phi datrn cc c im a l vng ph sng, mt thu bao ca vng ph vtng s knh ca mng.Mu 3/9: s knh trong 1 cell l ln, tuy nhin kh nng nhiu cao. Mhnh ny thng c p dng cho nhng vng c mt my di ng cao.Mu 4/12: sd cho nhng vng c mt lu lng trung bnh.Mu 7/21: sd cho nhng khu vc mt thp

Cu 2: trnh by nguyn tc truyn sng trong thng tin di ng?

- Truyn sng trong ko gian t do- C ptrnh truyn sng ph thuc vo cc yu t: k/c d, tn s f => ph thuc

vo cng sut p- Truyn trong mi trng th v nng thn: ng i ca sng in t

(dng tia) ch yu l tia phn x, tia khc x. gia 2 mi trng khc nhau khigp gc ca cc ta nh th c hin tng b b xung (thc ra vn la 1 mitrng)

- Tn x: cng t 1 tia gp mi trng gh gh ko = phng => tch ra thnh

nhiu tia- Phn x: mi trng ng nht- Suy gim: cho 1 tia vo m ko phn x, ko tn x, ko khc x th b hp th,

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cho tn s i qua nhng b gi li 1 phn c ngha l mi trng hp thsng in t => trng hp ny b suy gim

- Truyn sng nhiu tia gy ra hin tng phaing a ng- Phn tn thi gian phng nga suy hao- Nhiu gia cc k t ISI :

T s C/N; C/I; C/A

Cu 3: mc ch ca quy hoch mang l g? a vo lp t mt h thng bao gi cng phi c nhng k hoch, nhng d nv k thut, nhng d tr v kinh t. Trong thit k mng thng tin di ng s ccvn cng c xem xt k lng. Vi kh nng s dng, kh nng v ngvn m vng ph sng c th rng khp hoc ch p ng c mt s trng hpno , tuy nhin trng hp m rng l ln. iu i hi phi quy hoch mng.

(Chm gi l chnh )

CHNG 7

Cu 1: Nu ra nhng hn ch ca mng GSM, v vic gii quyt nhng vn

trn em li nhng tin ch g?

Hn ch GSM:

V pha ngi s dng, m bo cho ph ca mt knh trong khong200KHz, khi s dng GMSK ngi ta phi gim tc truyn bit cho

knh ting xung cn 13Kbps v knh d liu l 9,6Kbps. Nh vy thng

tin c ct thnh nhng khong 20ms. i vi ting th c th chp nhn

c cn i vi s liu th rt chm, thm na thi gian thit lp mt

cuc gi di 20ms s tr nn ko thun tin. dch v truyn d liu GSM

hin nay cn phi i hi gi cc cao khi kt ni, cc b tr theo thi

gian s dng.. l nhng nhc im chnh ca GSM. V pha nh khai thc: vic qun l ti nguyn ko hiu qu, s lng

ngi s dng b hn ch bi phm vi phc v hp, SMS ko ph hp.

T nhng hn ch th GSM phase 2 + ra i(GPRS)

u im ca GPRS:

- v ch truyn dn:

+ gi v thu d liu ch gi

+ hiu qu v gi thnh v hiu qu sd ti nguyn ln

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+ truyn dn c nhng khi d liu c t/cht ri rc Bursty: c th truyn dn

thng xuyn nhng lng nh d liu v truyn dn ko thng xuyn nhng

lng ln d liu.

- v thit k cu trc mng:

+ ko c s sa i phn cng trong BTS h tr dch v GPRS

+ kh thng qua giao din v tuyn cao: c th ln ti 21,4 Kbps trn 1 khe

thi gian TS v 1 MS c th sd c 8TS ca 1 khung TDMA

+ thi gian truy cp mng ngn

- v mt dch v:

+ c th kt ni vs cc mng d liu ngoi

+ thng thng thi gian kt ni c th ln ti hng gi

+ truyn dn ng ln, ng xung c lp

+ cc gi c di ngn: 500-1000 octet+ ko cn truy cp vo HLR cho mi gi d liu GPRS

+ mi phn t mng u bit ni n tip theo ca gi

+ tnh cc da trn dung lng d liu c truyn

Cu 2: phn tch s khc nhau gia cc phn t mng trong h thng

GSM v GPRS?

Mi cp nht:Nt h tr GPRS phc v (SGSN), nt h tr GPRS cng

(GGSN),Khi iu khin gi (PCU),Cc giao din mi.iu chnh: Phn mm ca HLR v MS.

- Cc thc th mng logic c thm vo c thm vo l : Nt h tr GPRS

dch v (SGSN), nt h tr GPRS cng :GSM khng cung cp cc chc

nng h tr chuyn mch gi. xy dng mng GPRS ta phi thm vo 1

tp cc nt mng mi gi l nt h tr GSN. Cc GSN c nhim v phn phi

v nh tuyn cc gi d liu gia cc trm di ng MS v mng d liu gi

ngoi (PDN)- Kim tra gi (PCU): y l 1 b sung thm vo BSC s l vic truyn d

liu gi gia my u cui MS v SGSN trong mng GPRS. PCU dng x

l giao din v tuyn thong qua vic kim sot cc lp iu khin lin kt v

tuyn thng qua vic kim sot cc lp iu khin lin kt v tuyn RLC v

iu khin truy nhp ng truyn MAC.

- Mng GPRS backbone v 1 s chun giao tip to thnh s mng:

- Tt c cc nt GPRS(GSN) u c kt ni qua 1 mng GPRS backboneda trn c s IP. Bn trong mng backbone ny , cc GSn ng gi PDN v

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pht chng theo c ch dduwwongf ngm , s dng giao thc ng ngm

GPRS

- c 2 loi mng GPRS backbone l : backbone intra-PLMN v backbone inter-

PLMN

- Ngoi ra cn thm vo cc Router, DNS sever, cc firewwall phc v cho

internet.

- Ngoi cc thc th thm vo, nng cp GSM ln GPRS cn phi cp

nht( phn mm) 1 s phn t nh BSC, BTS, MSC/VLR, HLR, h thng

tnh cc, h thng hoch nh mng, h thng vn hnh bo dng O&M

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Cu 3: Ti sao dch v ca mng GPRS li pht trin hn so vs mng

GSM?

- GPRS l 1 h thng mng mi cho mng GSM. GPRS mang nhng c im

hn hn so vi GSM.

- GPRS c kh nng cung cp tc s liu ln ti 171,2 kbps, t c khi

GPRS s dng 8 khe thi gian ng thi. Tc ny nhanh gp 3 ln tc

truyn d liu trn mng c nh hin ti v khong 10 ln so vi dch v d

liu chuyn mch knh trong GSM.

- Thi gian truy cp ngn, tc d liu cao m trong mng GSM truyn thng

vic khi to mt kh nhiu time, v tc ch t 9,6kbps, GPRS thc t

mang li thi gian khi to phin nh hn 1 giy v tc d liu n hng

chc Kbps.

- GPRS to iu kin cho ra s xut hin ca nhiu ng dng m cho nnay mng GSM cha th cung cp do hn ch v tc , GPRS thc hin ton

b cc ng dng Internet quen thuc t duyt trnh web.

- H tr trc tuyn nn thng tin c th truyn hoc nhn bt k lc no khi c

yu cu.

- GPRS dng chuyn mch gi nn tnh cc thn thin hn so vi ngi s

dng dch v chuyn mch knh GSM.

- Cc ng dng mi l : Truyn file, truy cp d liu tng tc, qun l fleet,thu pht email, t ng ha gia nh(truy cp iu khin cc thit b trong gia

nh) hn hn so vi GSM.

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CHNG 8

Cu 1: c im ca m tri ph PN? Thuc tnh ngu nhin m cc chui c

th t c?

c im ca m PN:

L m tt nh m my thu mong mun bit c, cn ging vi my thu

khng mong mun th n ging nh tp m.

N thng c gi l dy gi tp m, Dy PN l dy cc con s tun

hon vi chu kh nht nh.

Ta s dng {ci, i=integer}= {L,c-1,c0,c1,L} ch dy PN. Gi s N l

chu k ca n , tc l ci+N=ci

V dy PN tun hon, chu k ca n phi ln nhn c tnh cht ngu

nhin tt.

Trong h thng DS/SS tn hiu lin tc thi gian c to ra tu dy PN

tri ph. Gi s dy PN l nh phn. Tc ci=+-1, th tn hiu PN l:

( ) ( . )k TC ck

c t c p t k T

=

=

Tn hiu PN cng c gi l tn hiu tri, tn hiu ngu nhin, v dng

sng c trng

M PN phi c thit k c rng bng tn ln hn nhiu so vi

rng bng tn ca bn tin. PN thc cht l 1 tn hiu tt nh

Thuc tnh ngu nhin quan trng m cc chui phi t:

Tn sut tng i ca 0 1 l .

di on chy(ca khng v mt) ging nh k vng trong th nghim

tung ng xu: mt na c di l mt, mt phn t c di l 2, mt

phn tm c di l 3, 1/2n c di l n i vi mi n l hu hn.

Nu dch chui ngu nhin i mt s lng khc khng cc phn t, th

chui nhn c s c s lng cc phn t ging nhau v s lng ccphn t khc nhau ging nh trong chui gc.

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Cu 2: H thng thng tin s c coi l SS l g? V tr, chc nng ca tri ph

v iu ch c th i ln c khng?

H thng c coi l tri ph nu:

Tn hiu pht chim rng bng thng ln hn rng bng thng ti

thiu cn thit pht thng tin.

cc h thng thng tin di ng thng thng, rng bng tn l vn

quan tm chnh v cc h thng ny c thit k s dng cng t rng

bng tn cng tt. cc h thng iu ch bin song bin, rng bng tn

cng thit pht mt ngun tn hiu tng t gp hai ln rng bng tn

ca ngun ny. cc h thng iu tn , rng bng tn ny c th bng vi

ln rng bng tn ngun,ph thuc vo ch s iu ch.i vi cc tn s

rng bng tn cn thit c cng gi tr vi tc bit ca ngun. rng

bng tn chnh xc trong trng hp ny ph thuc vo kiu iu ch.

Tri ph c thc hin bng mt m c lp vi s liu.

cc h thng thng tin tri ph, rng bng tn ca tn hiu c th c m

rng thng thng hng trm ln trc khi pht.Khi ch c mt ngi s dng

trong bng tn SS th bng tn nh vy khng c hiu qu.Tuy nhin, mi

trng nhiu ngi s dng,h c th dng chung bng tn SS v h thng tr

nn c hiu qu m vn duy tr c cc u im ca k thut tri ph.

V tr ca cc chc nng tri ph v iu ch c th i ln cho nhau. Hai

chc nng ny thng c kt hp v thc hin nh mt khi duy nht.

Cu 3: u nhc im ca CDMA?

u im:

+ mt m thng qua chui m gii ngu nhin PN dng k thut tri

ph

+ dung lng ln v mm

+ chuyn giao mm

+ cng sut pht thp

+ hiu qu sd tn s cao (h s sd li tn s 1)

+ cht lng tt

+ d dng nh v thu bao

+ nhiu loi hnh dch v

Khuyt im:

+ vn iu khin cng sut MS v BTS phc tp

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+ vn ng b chui PN phc tp (ng b th v tinh chnh)

Cu 4 : Nu nguyn l k thut ca mng CDMA?

Qu trnh tri ph v nn ph trong k thut CDMA

Trong h thng CDMA, mi ngi dng c gn cho mt chui m xc nh,

v tt c cc ngi dng c th s dng chung khong bng tn trong cng mt

khong thi gian. Do CDMA da trn nguyn l tri ph, do mi trm pht s

s dng mt chui tri ph gi ngu nhin tc ng vo tn hiu tin tc. Khi my thu

nhn c tn hiu t nhiu trm pht khc nhau, n s ly tn hiu mong mun

bng cch gii m tn hiu bng chui m ring ca chnh tn hiu (hnh trn). Tac c kt qu ny l do tnh t tng quan v tng quan cho ca cc chui m

tri ph.

Trong hnh trn, my thu mong mun nhn c tn hiu tin tc t ngi dng

A nn s dng chui m dnh ring cho A gii m. Khi , cc tn hiu nhn

c t cc ngi dng khng mong mun (B, C) tr thnh nhiu i vi tn hiu t

A (do tnh tng quan cho thp), v t ta c th thu c tn hiu t A mt cch

d dng.

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Chng 9

(t tm cc ca 3 cu hi , trong ny ht 3 cu nhng t cha phn

Cu 1 :Trnh by c im ca mng City phone iPas?

1,Mng WLL :

- V tuyn c nh

- Di ng tc < 50Km/h

2,TDMA :

- Thoi : 32kbps v 64kbps

-Data : 384 kbps (3G)

1 Carrier RF chia lm 8 TS (4TS down, 4TS up) Trong 4TS 1 TS dng lm

CCH, 3TS cn li dng lm TCH (ngha l 3 my gi ng thi )2 Carrier RF : 16TS trong 8 TS th 1 TS dng lm CCH , 7 TS dng lm TCH

3, S dng cong ngh IP

Chuyn mch mm IP

Gi tin IP

ng truyn trong mng IP

C kh nng kt ni mng ko IP (ss7)4, Mng phn tn : Nhiu Gate way dung lng thp 20.000 nn rooming nhiu

trm thu pht nh :

CSut nh 500>>2000mW

Dung lng nh 1RF v 2RF ( nn chuyn giao nhiu)

5 im : d trin khai (phn tn ) r

D kt ni IP

Cht lng cuc gi cao, hiu dng , bo tr ko tn km, lp t d

N :

Cht lng ph sng (1800-1900).

Chuyn giao nhiu.

-L mng TTDng ni b, da trn giao thc IP, Ipas kt hp nhiu u im v

cu trc Wacos c kh nng tng thch vi mng TDM

-Cht lng thoi (tc ).-Dung lng cao mt ln n 15000 ngi /Km2. c th dng trong cc thnh

ph c 10000 n 50000 ngi s dng

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-Tc MS di chuyn cho php 50km/h, nu ln hn cht lng knh vi tuyn suy

gim nghim trng do hiu ng doppler >> gy ra s thay i tn s . Do s chuyn

ng.

-Qu trnh Handover cng xut hin (.) cng 1 , khi knh v tuyn ang lin lc

gim cht lng chuyn sang 1 knh v tuyn c dung lng cao hn.

2, Nguyn tc c bn ca h thng city phone iPAS ?

-Nn WACOS c s IP : L 1 th h mi c h thng Softswitch c s IP , ton b

phn cng , phn mm (.) WACOS iPAS i ni mng c nhiu ch v qua IP, Ton

b bo hiu v thoi (h tr trung k IP) i chuyn qua mng IP.

-Nn a dch v thng nht : WACOS IPAS cp nhiu dch v truyn hnh v dch

v mng qua nn thi nht : DV thoi, I/O IP, dch v trung cp mng.Gate way a giao thc : giao thc ss7, v tuyn Q931, V5.x , ISDN, TCP/IP nh l

1 chuyn mch ni ht >> cc giao thc cn c th chuyn i vi nhau , h thng

hot ng trn thc, Bus chung h tr nng cao ca thng tin phng tin v

dung lng h thng.

- Chia s im bo hiu SS7: thng qua cu trc ch t.

Mi Gate way chia s 1 im bo hiu SS7 v thng tin vi nhau qua SNSD

Khi nhiu gateway c thit lp cng 1 v tr chng c th lin kt vi nhau bngcch xp chng .

-Kt ni IP gia cc Gate way

Cc Gate way c th c kt ni vi trung k IP; cng ngh VOIP mang li ton

b u im ca mng IP bng rng v tn dng ti nguyn TDM ca DSTN :

+ H tr truy cp v tuyn v hu tuyn.

+ H tr ci tin dung lng v dch v.+Nn Sottswich hiu sut cao.

+H thng qun l chng trnh ph tr hiu qu.

+Mng bo hiu IP tin tin.

+Gii php ty Chnh theo cc iu kin hot ng c bit.

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Chng 10

Cu 1: Phn tch tnh hnh pht trin chung ca ht thng tin di ng Vit Nam

Ch ny l chm gi thi, cc bn c th lm theo cc bn,

Mi thc s pht trin trong vng 20 nm, nhng nhng bc tin trong cng ngh

cng nh trong s pht trin th trng ca mng di ng cho thy thng tin di ng

l mt nhu cu thit yu v quan trng i vi ngi dng. n nay, in thoi di

khng ch dng gi in, nhn tin SMS m cn c th gi v nhn MMS, email;

lu cc tp m thanh, hnh nh, d liu cng chc nng nghe nhc, gii tr; lt

web, xem TV trc tuyn

Cc nh cung cp dch v v ngi dng u lun mong mun v hng ti

cc cng ngh khng dy c th cung cp c nhiu loi hnh dch v hn vi tnh

nng v cht lng dch v cao hn. Qua cc giai on pht trin cc th hthng tin di ng t 1G, 2G, 3G v 4G trong tng lai u gn cht vi nhu cu ca

ngi dng thng qua cc tc dch v ca cc th h.

Hin nay, phn ln cc nh khai thc vin thng ln trn th gii u ln k

hoch thc hin 4G cho cc vng th, ni m c nhiu cc t chc, cng ty cng

nh s lng khch hng ln - cc i tng m lun mong mun cc dch v cht

lng tt v tc truyn d liu cao. Tuy nhin, trc mt cc nh u t s tip

tc cung cp cc dch v 3G cng nh 3,5G v n c xem nh l qu trnh thchin tng bc cho 4G. iu ny khng ch gip h tip tc m rng vng ph

sng, gia tng s lng khch hng v gip thu hi vn u t cho 3G. Vi ngi

dng, h c th chuyn d dng sang cng ngh 4G, bi n gin vi h ch l s

m rng cc ng dng ca mng 3G hay 3,5G m h ang dng.

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NMT

(900)

TACS

GSM(900)

AMPS cdma2000Mx

WCDMA

SMR

GSM(1800)

GSM(1900)

IS-136TDMA(800)

IS-95

CDMA(800)

IS-136

(1900)

IS-95

(J-STD-008)(1900)

GPRS

iDEN(800)

GPRS

EDGE

cdma20001x

1G 2G 2.5G 3G

Bi tp

Bi tp : v cell

i vi bi tp ny cc bn lm nh sau:u tin cc bn a ra cng thc tnh :

1. D=Cn (3N). R = Cc bn phn tch ra di dng R +cn(3).R nhm nh

la thy l mnh tnh ton xong (tnh chun vo nh , thy cho im cao

ch ny, ch di lon lm, c khi thy cng chng nhn u @@)

D: K/cch 2cell

R: Bn knh cellN: S nhm s dng li

Tnh ton xong , cc bn ko cn bit kt qu th no p ngay 1 trong s cc

Mu ti s dng li tn s di y ty theo bi bn cho l t l : 3/9

hay 4/12, hay 7/21

Thy cho bao nhiu cc bn ch cn m s , v s ra bi sau b

nguyn cc phn t in sn di y vo bi, rt nhanh ng khng? Nuc bn no hi nh thy cho s nhiu hn th sao? Cu tr li l ko u,

v lm sao thi gian , c 60 pht thi

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V mu s dng li tn s 5/15 vi 45 v tnh khong cch s dng li tn

s bit bn knh l 500m?

V d:

D = R N3

Trong : R = 500m.

N: (kch c mng mu) = 15

D = 500 15.3 = 3354,1m (ln phn tch di dng cn)

Trng hp 5/15 cc bn tnh v phn tch khai cn nh bnh thng , v 1 vi

vo, sau di kt lun ko th v c, ko s dng trong thc t V V

Hnh 4.18 Mu ti s dng li tn s 3/9

Hnh 4.19 Mu ti s dng li tn s 4/12

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Hnh 4.20 Mu ti s dng tn s 7/21

Bi tp :M ho xon

2. Thc hin m ho xon c tc r = 1/2 , K=3. Khi tn hiu vo l:

100011001 vi s m sau:

(Gi s thanh ghi u tin c gi tr 000 v sau chui vo l 00000)

Tn hiu ra 1 l: D1 D3

Tn hiu ra 2 l: D1 D2 D3

53

D1 D2 D3

+

+

Tn hiuvo

Tn hiu m ho

2

1

+

+ +


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Trng thi Tn hiu

vo

D1 D2 D3 Tn hiu ra

1

Tn hiu

ra 2

0 0 0 0

1 1 0 0 1 1 12 0 0 1 0 0 1

3 0 1 0 0 1 14 0 0 0 0 0 05 1 0 0 1 1 1

6 1 0 1 1 1 07 0 1 1 0 1 0

8 0 1 0 0 1 19 1 0 0 1 1 1

10 0 0 1 0 0 1

11 0 1 0 0 1 112 0 0 0 0 0 0

13 0 0 0 0 0 014 0 0 0 0 0 0.. .. .. .. .. .. ..

Tn hiu u ra b m xon l: 1101110011101011110111000000

Bi 2 : Thc hin m ho xon c tc r = 1/2 , K=3. Khi tn hiu vo l:

100011001 vi s m sau:

(Gi s thanh ghi u tin c gi tr 000 v sau chui vo l 00000)

Tn hiu ra 1 l: D2 D3

54

D1 D2 D3

+

+

Tn hiuvo

Tn hiu m ho

2

1

+

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Tn hiu ra 2 l: D1 D2 D3

Trng thi Tn hiu

vo

D1 D2 D3 Tn hiu

ra 1

Tn hiu

ra 2

0 0 0 01 1 0 0 1 1 12 0 0 1 0 1 13 0 1 0 0 0 14 0 0 0 0 0 05 1 0 0 1 1 16 1 0 1 1 0 07 0 1 1 0 1 0

8 0 1 0 0 0 19 1 0 0 1 1 1

10 0 0 1 0 1 111 0 1 0 0 0 112 0 0 0 0 0 013 0 0 0 0 0 014 0 0 0 0 0 0.. .. .. .. .. .. ..

Tn hiu u ra b m xon l: 1111010011001001111101000000

+

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