TS. Nguyn Thanh H

GIO TRNH

K THUT CHUYN MCH V TNG I S

NH XUT BN KHOA HC V K THUT H NI - 2009

MC LC

Li ni u 3Mc lc 5

Chng 1. CC KIN THC TNG QUAN 131.1 Mng v dch v vin thng 13

1.1.1 Mng vin thng 131.1.1.1 Khi nim 131.1.1.2 Cc thnh phn ca mng vin thng 131.1.1.3 Cc phng php t chc mng 14

1.1.2 Dch v vin thng 191.1.2.1 Khi nim 191.1.2.2 Cc dch v vin thng 201.1.2.3 Mng's a dch v (ISDN) 21

1.2 Tng quan v tng i in thoi ^ 211.2.1 Lch s v xu hng pht trin ca tng i 21

1.2.1.1 Lch s k thut tng i 211.2.1.2 Xu hng pht trin 24

1.2.2 Phn loi tng i in t ^ 251.2.2.1 Phn loi theo phng thc chuyn mch 251.2.2.2 Phn loi theo phng thc iu khin 251.2.2.3 Phn loi theo v tr 271.2.2.4 Phn loi theo tn hiu 27

1.3 Tng i in t s SPC 271.3.1 S pht trin ca tng i in t SPC 271.3.2 u im ca cc tng i k thut s SPC 31

1.3.2.1 Tnh linh hot 311.3.2.2 Cc tin ch thu bao 321.3.2.3 Tin ch qun tr 331.3.2.4 Cc u im thm vo ca k thut s 33

1.3.3 S khi chc nng ca tng i s SPC 371.3.3.1 S khi 371.3.3.2 Chc nng 39

1.3.4 Phn tch mt cuc gi trong tng i SPC 461.3.4.1 Tn hiu nhc my (off- hook) 471.3.4.2 S nhn dng ca thu bao gi 471.3.4.3 S phn phi b nh v cc thit b dng chung 471.3.4.4 Cc ch s a ch 481.3.4.5 Phn tch ch s ^ 481.3.4.6 Thit lp ng dn chuyn mch 48

1.3.4.7 Dng chung v m hiu chuQng 491.3.4.8 Tn hiu tr li 491.3.4.9 Gim st 491.3.4.10 Tn hiu xa kt ni 49Chng 2. K THUT CIUYN MCH KNH 51

2.1 Tng quan v chuyn mch 512.1.1 nh ngha 512.1.2 Chuyn mch knh (Circuit Swithching) 51

2.1.2.1 Khi nim 512.1.2.2 c im 52

2.1.3 Chuyn mch tin (Messaee Svvithching) 522.1.3.1 Khi nim' 522.1.3.2 c im 53

2.1.4 Chuyn mch gi 542.1.4.1 Khi nim 542.1.4.2 c im 552.1.4.3 u im 55

2.2 Chuyn mch knh 562.2.1 Phn loi 56

2.2.1.1 Chuyn mch phn chia khng gian (SDTS) 562.2.1.2 Chuyn mch ghp (MPTS) 57

2.2.2 Chuyn mch PCM 582.2.2.1 Chuyn mch thi gian (T) 592 .1 2 2 Chuyn mch khng gian (S) 67

2.2.3 Phi php cc cp chuyn mch 732.2.3.1 Chuyn mch ghp TS 732.2.3.2 Chuyn mch STS 752.2.3.3 Chuyn mch TST 772.2.3.4 Nhn xt 82

Chng 3. K THUT IU KHIN 833.1 Tng quan 833.2 Cu trc phn cng h thng iu khin tng i SPC 84

3.2.1 Cu trc chung 843.2.1.1 S khi 843.2.1.2 Chc nng 843.2.1.3 Nguyn l lm vic 85

3.2.2 Cc loi cu trc iu khin 863.2.2.1 Cu trc iu khin n x l 863.2.2.2 Cu trc a x l 87

3.2.3 iu khin trung tm v s trao i gia cc b vi x l 91

3.2.3.1 iu khin trung tm 913 2 3 .2 S trao i thng tin gia cc b x l 92

3.3 C cu d phng 943.3.1 D phng cp ng b 943.3.2 D phng phn ti 953.3.3 D phng nng 963.3.4 D phng n+1 96

3.4 Cu trc phn mm ca tng i 973.4.1 Khi nim chung 973.4.2 Cc vn v thit k phn mn 98

3.4.2.1 Cc c tnh ch yu ca phn mm 98s.4.2.2 v cu trc 993.4.2.3 Phn chia chng trnh 993.4.2.4 Cc chng trnh h thng 1003.4.2.5 Cc chng trnh p dng 1033.4.2. Cp nht phn mm hin hnh 103

3.4.3 Cc modul chnh ca phn mm 1043.4.3.1 Modul iu khin chnh 1043.4.3.2 Modul giao tip ng y 1043.4.3.3 Modul lin lc ni b 1053.4.3.4 Modul lin lc ra ngoi 1053.43.5 Modul nhn bit v x l li 1063.4.3. Modul giao tip my tnh 106

Chng 4, K THUT BO HIU 107

4.1 Tng quan 1074.1.1 Khi nim 1074.1.2 Cc chc nng bo hiu 107

4.1.2.1 Chc nng gim st 1074.1.2.2 Chc nng tm chn 1074.1.2.3 Chc nng vn hnh 107

4.1.3 c im cc h thng bo hiu 1084.1.4 H thng thng tin bo hiu 1084.1.5 K thut bo hiu 108

4.2 Ni dung ca bo hiu 1084.2.1 Phn tch cuc gi 1084.2.2 Phn theo chc nng 110

4.2.2.1 Bo hiu nghe - nhn 1104.2.2.2 Bo hiu trng thi (bo hiu gim st) 11142.2.3 Bo hiu a ch 111

4.2.3 Phn theo tng quan 1134.2.3.1 Bo hiu gia tng i vi thu bao 113

4.2.3.2 Bo hiu lin tng i 1134.3 Phng php trun dn bo hiu 114

4.3.1 Bo hiu knh kt hp (CAS: Chanel Associated Signalling) 1144.3.1.1 Phn loi 1144.3.1.2 Phng php truyn 1154.3.1.3 Cc k thut truyn cc tn hiu bo hiu trong CAS 115

4.3.2 Bo hiu knh chung (CCS) 1204.3.2.1 Khi nim chung 12043.2.2 Cu trc bn tin CCS 1214.3.2.3 u im 122

4.3.3 H thng bo hiu R2 (MFC) 1224.3.3.1 Khi nim chung 1224.3.3.2 Bo hiu ng dy 1224.3.3.3 Bo hiu thanh ghi 124

4.3.4 Bo hiu s 7 (CCITT No 7) 1284.3.4.1 Khi nim chung 1284.3.4.2 Cc khi nim c bn 1294.3 A 3 Phn mc trong bo hiu s 7 1304.3.4.4 orn v bo hiu 132

4.4 X l bo hiu trong tng i 1334.4.1 Tng quan 1334.4.2 S nh tun trong tng i 134

4.4.2.1 Bo hiu tng i - thu bao 1344A.2.2 Bo hiu lin tng i 138

4.4.3 Cc b thu pht bo hiu 1404.4.3.1 Thu pht MF 1404.4.3.2 Thu pht bo hiu knh kt hp 1414.4.3.3 Chuyn i 1VF sang CAS 145

4.4.4 Cc b to tone v bn tin thng bo 1464.4.4.1 S nh tuyn tones v cc bn tin thng bo 1464.4.4.2 Cc tones x l cuc gi 1474.4.4.3 B to tone v cc bn tin thng bo 148

Chng 5. GIAO TIP KT CUI 1515.1 Tng quan 1515.2 Giao tip ng dy thu bao 152

5.2.1 Tng quan v cc kt cui ng dy thu bao 1525.2.1.1 ng dy thu bao Analogue 1525.2.1.2 ng dy thu bao s 153

5.2.2 Thit b giao tip thu bao tng t 1535.2.2.1 Chc nng cp ngun (Battery feed) 1535 2 2 2 Chc nng bo v qu p (Over Voltage Protection) 154

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5.2.23 Chc nng rung chung (Ringging) 1545.2.2A Gim st (Supervision) 1555.22.5 Gii m, m ha (Codec) 15552.2.6 Sai ng (Hibrid) 15652.2.1 Kim tra (Test) . 1565.2.2.S Cc khi lin quan ln cn 157

5.2.3 Giao tip u cui thu bao s 1575.3 Thit b tp trung 158

5.3.1 Giao tip thit b ng b 1595.3.2 Giao tip thit b chuyn mch nhm 1595.3.3 Giao tip vi khi mch giao tip thu bao 1595.3.4 Giao tip thit b to m bo 1595.3.5 Giao tip vi thit b my in thoi chn s a tn 1595.3.6 Giao tip vi thit b cnh bo 160

5.4 Giao tip thit b kt cui trung k 1615.4.1 Phn loi 161

5.4.1.1 Trung k t thch 1615.4.1.2 Trung k hai dy c o - line 1615.4.1.3 Trung k E&M (4 dy) 1625.4.1.4 Trung k depart (3 dy) 1625.4.1.5 Trung k 6 dy 1625.4.1.6 Trung k s 162

5.4.2 Giao tip thit b kt cui tning k tng t 1625.4.2.1 Bo hiu 1625A.2.2 Cp ngun 1635.4.2.3 Sai ng 1635A.2A Ghp knh v iu khin 163

5.4.3 Giao tip thit b kt cui trung k s 1635.4.3.1 S khi 1635.4.3.2 Hot ng 164

5.5 B tp trung xa 1655.5.1 Cu trc 1655.5.2 Phn phi cc chc nng iu khin 166

5.5.2.1 Phng php phn b 1665.5.22 Phng php tp trung 166

5.5.3 Bo hiu 1675.5.4 Cc c im ng ng ca h thng tp trung xa 167

5.5.4.1 H thng ti 3 thu bao v cc b tp trung phn b 1675.5A.2 Gi ni b 167

/

Chng 6. IU HNH KHAI THC V BO DNG 1696.1 Tng quan 1696.2 iu hnh v khai thc trong tng i SPC 169

6.2.1 iu hnh trang thit b tng i 1696.2.2 Qun l mng thu bao 169

6.2.2.1 To lp thu bao mi 16962.2.2 Chuyn i thu bao 170.2.2.3 Thay i dch v thu bao 170.2.2.4 nh ch thu bao khai thc 170

6.2.3 Qun l s liu, phin dch v to tuyn 1706.2.4 Qun l s liu cc 1706.2.5 Gim st, o th ti v lu lng 170

6.2.5.1 Cc phng thc gim st 1716.2.5.2 Cc c ch o th 171

6.3 Bo dng tng i 1716.3.1 Bo dng ng dy thu bao 1716.3.2 Bo dng ng trung k 1726.3.3 Bo dng trng chun mch 1726.3.4 Bo dng dng h thng iu khin 1726.3.5 Cc phng sch bo dng 173

6.3.5.1 Phn cng 1736 3 .5 2 Phn mm 174

6.4 Nguyn tc x l chng ngi 1756.4.1 Tm li bng phng thc nhn cng 1756.4.2 Bo dng phng nga 175

6.5 Bo dng phn mm 1766.5.1 Cu to v nhim v 1766.5.2 Bo co v li 1766.5.3 Lnh vc hot ng trung tm phn mm 1776.5.4 Th vin phn mm 177

Chng 7. MNG CHUYN MCH GI 1797.1 C s mng chun mch gi 179

7.1.1 M hnh tng th ^ 1797.1.2 T chc phn lp ca mng chuyn mch gi 1797.1.3 Thit lp tuyn ni 1817.1.4 Knhlogic 1817.1.5 Cc hnh thi dch v ^ 1827.1.6 Phng thc nh tuyn trong mng chuyn mch gi 183

7.2 Mt s giao thc trong chuyn mch gi 184

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7.2.1 Giao thc X.25 1847.2.1.1 X.25 cp 1: cpvt l 1857.2.1.2 X.25 cp 2; cp tuyn s liu 1857.2.1.3 X.25 cp 3; cp mng 192

7.2.2 Giao thc TCP/IP 2017.2.2.1 Khi qut v TCP/IP 20112.2.2 Lp ng dng 2027.2.2.3 Lp vn chuyn 20212.2A iu khin lung trong TCP/DP 2097.2.2.5 Khi qut v lp Internet trong TCP/IP 2101 2 2 .6 Tng quan v a ch TCP/IP 2127.2.2.7 Thnh phn v hnh dng ca a ch IP 2137.2.2.8 Cc lp a ch IP 214

Chng 8. MT S CNG NGH CHUYN MCH TIN TIN 2178.1 Cng ngh Frame relay 217

8.1.1 c im 2178.1.2 Cu hnh mng Frame relay 2198.1.3 Tnh nng ca Frame relay 221

8.2 Cng ngh chuyn mch ATM 2228.2.1 Tng quan ATM 2228.2.2 M hnh chun ca ATM v mng ATM 223

8.2.2. M hnh ATM chun 2238.2.2.2 Cc cu hnh giao thc chun 226

8.2.3 Knh o v ng o 2288.2.3.1 Knh o 2288.2.3.2 ng o 228

8.2.4 Nguyn l chuyn mch ATM 2288.2.5 Cu trc t bo ATM 231

8.2.5.1 T bo ATM 2318.2.5.2 Cu trc t bo ATM 232

8.2.6 Bo hiu v nh a ch 2348.2.6.1 BohiuATM 2348.2.6.2 nh a ch 237

8.2.7 Kt lun 2388.3 Cng ngh chun mch MPLS 240

8.3.1 Lch s pht trin MPLS 2408.3.2 Qu trnh pht trin v gii php ban u ca cc hng 243

8.3.2.1 IP over ATM 2438.3.2.2 Toshibas CSR 24483.2.3 Ciscos Tag Switching 2448.3.2.4 IBMs ARJS v Nortels VNS 245

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8.3.2.5 Cng vic chun ha MPLS 2458.3.3 Cc thnh phn MPLS 246

8.3.3.1 Cc khi nim c bn MPLS 2468.3.3.2 Thnh phn c bn ca MPLS 248

8.3.4 Hot ng ca MPLS 2498.3.4.1 Cc ch hot ng ca MPLS 249s.3.4.2 Hot ng ca MPLS khung trong mng ATM-PVC 260

8.3.5 Cc giao thc s dng trong mng MPLS 2618.3.5.1 Giao thc phn phi nhn 2618.3.5.2 Pht hin LSR lan cn 2638.3.5.3 Giao thc CR-LDP 2668.3.5.4 Giao thc RSVP 2768.3.5.5 So snh CR-LDP v RSVP 2818.3.5. So snh MPLS v MPOA 282

Ti liu tham kho 284

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Chng 1 CC KIN THC TNG QUAN

1.1 MNG V DCH v VIN THNG

1.1.1 Mng vin thng

1.1.1.1 Khi nim

Mng vin thng l tt c nhng trang thit b k thut c s dng trao i thng tin gia cc i tng trong mng.

Cng vi s pht trin ca x hi, nhu cu thng tin lin lc ngy cng tng. Nhim v thng tin lin lc c mng li bu chnh vin thng m nhim. p ng nhu cu thng tin th mne phi ngy cne pht trin.

Qu trnh pht trin ca mng tri qua nhiu aiai on. Ban u l mng in thoi tng t, dn dn in bo, telex, facsimile, truyn s liu... cng c kt hp vo.

Vi s ra i ca k thut s thc y SI' pht trin tin mt bc di tr thnh mng vin thng hin i vi rt nhiu dch v.1.1.1.2 Cc hnh phn ca mng vin thng

Thit b pht Node chuyn Node chuyn Thit b thumch mch

Hnh 1-1: Cc thnh phn mng vin thng.Mt mng thng tin phi c cu thnh bi cc b phn sau: Thit b thu/phtL cc thit b vo ra, thit b u cui gi thng tin vo mng v ly thng tin ra t mng. 'Node chuyn mch

Thu thp thng tin ca cc i tng v x l tho mn cc yu cu . Bao gm hai nhim v:

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+ X l tin (CSDL): x l, cung cp tin tc.+ Chuyn mch.

Node chuyn mch hay tng i l ni nhn thng tin ri truyn i. Ty theo loi tng i m ta c th thm nhp trc tip hay gin tip vo n.V d : vi tng i ni ht, thu bao c th trc tip thm nhp vo tng i cn i vi tng i chuyn tip th khng, n ch nhn tn hiu ri truyn i t tng i ny sang tng i khc. Cng c loi tng i va l chuyn tip va l ni ht.

B phn chnh ca node chuyn mch l trng chuyn mch. Vi mt s iu khin th bt k u vo ca trng chuyn mch c th ni ti bt k u ra ca n, iu ny m bo bt k mt thu bao no trong mng c th giao tip vi bt k mt thu bao khc ang ri. H thong truyn dn (mng truyn dn)

H thng truyn n l phn ni cc node chuyn mch vi nhau hoc node chuyn mch vi thu bao truyn thng tin gia chng.

Ngi ta s dng cc phng tin truyn dn khc nhau nh thng tin dy trn, thng tin viba s, thng tin cp quang, thng tin v tinh...

Hin nay, nc ta ch yu l viba s v cp quang. Thne tin v tinh s dng trong lin lc quc t, cn thng tin dy trn hin nay hu nh khng s dng. Ton b cc ng ni gia cc node chuyn mch ti thu bao l ng dy thu bao, cn ni gia cc node chuyn mch l ng dy trung k. Phn mm ca mng

Gip cho s hot ng ca 3 thnh phn trn c hiu qu. Trong , s hot ng gia cc node chuyn mch vi nhau l c hiu qu cao cn s hot ng gia node v thu bao l c hiu qu thp.1.1.1.3 Cc phng php t chc mng Mng li (Mesh)

Nu bn c giao cho mt nhim v thit k mt mng in thoi th bn phi lm g?

Nu s thu bao vng A l khng nhiu lm, c th bn s xy dng mt mng nh hnh sau;

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Hnh 1-2: Mt tng i cho nhiu thii bao.Nhng vi s thu bao mt vng ln cn (B) cha c tng i mun trao

i thng tin vi vng A th c hai gii php t ra l:Th nht, thm cc b tp trung ng dy t vng ln cn (B) v ni

trc tip n tng i ang hat ng vng A. Cch ny n gin, nhng ch p ng c vi mt s lng thu bao vng B nh v nhu cu trao i thng tin sang vng A l t v tnh kinh t khng cao i vi s l'ng thu bao ca vng B l ln.

Th hai, thm mt tng i nh sau:

Hnh 1-3: S ni kt gia hai tng i.Vi gii php trn, thng tin c tnh an ton cao hn, ng thi chi ph ca

mng t hn nu s lng thu bao vng B l nhiu.Trong mng li, tng i c cng mt cp. Cc tng i u l tng i

ni ht c thu bao ring. Cc tng i c ni vi nhau tng i mt. Nh vy mi thu bao ca tng i khc u i bng ng trc tip t tng i ny ntng i kia m khng qua mt tng i no trung gian c.

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Hnh 1-4: Mng li.Mng ny c u im l thng tin truyn trc tip t thu bao ny n

thu bao kia ch qua tng i ch ca thu bao y thi. Tuy nhin, khi s lng tng i tng ln kh ln th vic ni trc tp gia cc tng i l phc tp v cn nhiu tuyn truyn dn. Mc khc, khi tuyn truyn dn gia cc tng i b hng th s khng c ng thay th bng cch qua tng i khc. Trong thc t, mng ny khng tn ti n c. Mng sao (star)

Mng sao l loi mng phn cp, c mt tng i cp cao v nhiu tng i cp di. Tt c cc tng i cp di u c ni vi cc tng i cp cao v gia cc tng i cp di khng ni nhau.

___ t f

Tng i cp cao

Tng i ni ht

Hnh 1-5: Mng sao.

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Tng i cp cao l mt tng i chuyn tip, khng c thu bao ring. Giao tip gia cc thu bao trong cng mt tng i l do tng i m nhn, khng nh hng n tng i khc.

Khi thu bao ca tng i ny mun ni vi tng i khc th vic chuyn tip thng qua tng i chuyn tip v khng c ng trc tip. Mng sao c m t nh hnh trn.

u im ch yu ca mng l tit kim ng truyn, cu hnh n gin. Nhng i hi tng i chuyn tip phi c dung lng cao, nu tng i ny hng th mi lin lc b ngng tr. Mng hn hp

tn dng u im v khc phc nhc im ca hai loi tng i trn, ngi ta a ra mng hn hp, trong mt phn l mng sao v phn kia l mng li, vi cc cp phn chia khc nhau.

Tuy nhin, mt mng quc gia khng phi lc no cng tun th theo chun CCITT m n cn c th thay i sao cho ph hp vi c im kinh t, x hi v quan trong nht l nhu cu trao i thng tin. V d mt mng quc gia tiu biu nh sau :+ Tng i chuyn tip quc gia NTE: L tng i cp di ca tng i chuyn tip quc t (ITE), Tng i ny c hai nhim v:

- Chuyn tip cuc gi lin vng.- Chuyn tip cc cuc gi ra tng i quc t.

+ Tng i chuyn tip vng LTE: Tng t nh tng i chuyn tip quc gia, nhng n qun l theo vng, tng i ny c th c thu bao ring.+ Tng i ni ht LE: Tip xc trc tip vi thu bao. Lin lc gia cc thu bao ca n l do n qun l, khng lin quan n cc tng i cao hn. Khi thu bao mun gi ra th n chuyn yu cu n tng i cp cao hn. Loi ny va c thu bao ring va c ng trung k.+ Tng i PABX: i vi thu bao th n l tng i cn i vi tng i cp trn th n li l thu bao v dy truyn dn l dy thu bao. s thu bao thng nh, nhu cu lin lc trong l ln.+ Tp trung thu bao: Gii quyt trng hp qu nhiu ng dy t thu bao ti tng i.

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IC : International Center

QC : Quaternary Center

TC : Tertiary Center

sc : Secondary CenterPC : Primary Center

LE : Local Exchange

Hnh 1-6: Mng hn hp theo phn cp theo chun ca CCTT.

^ .. . . Hnh 1-7: Mng hn hp ca quc gia tiu biu.

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m bo tin cy, ngi ta t chc cc tuyn d phng. N c nhim v phn ti, p ng nhu cu thng tin ln v trnh hin tng tc nghn.1.1.2 Dch v vin thng L 1.2.1 Khi nim

Bu chnh

Thng tin

I______

Vin thng

Thoi

Telex

Teletex

Facximine

VideoText

S liu

Hnh 1-8: Vin thng, mt trong cc dng c bit ca truyn thng.

''Truyn thng: l s trao i thng tin ca cc i tng c nhu cu trao i thng tin vi nhau bng con ng ny hoc ng khc."'Vin thng: l mt trong s cng c truyn hng. Truyn thng l mt khi nim rng. Vin thng c th coi nh l mt b phn ca ton b x hi truyn thng.Gi s, ta t hng bng in thoi, th l dn truyn thna, rt t bit. Vin thng l m ch mt khong cch a l c bc cu /rao i thng tin t x\""Dch v vin thng-, l hnh thi trao i thng tin m mng vin thng cung cp.""Dch v vt mang: Dch v vt mang cho ta kh nng s dng cc dch v vin thng.V d. Khi ta gi th, th h thng bu chnh dch v nh thng th, phng pht th, chuyn th... hnh thnh dch v vt mang l gi th. Chng ta c cc dch v vt mang khc trong vin thng nh dch v vt mang in thoi, dch v vt mang telex v.v...

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Hnh 1-9: Dch v xa v dch v vt mang.Dch v vt mang ch l s cung cp ca mt h thng truyn ti cho s

trao i thng tin.Dch v xa c tnh bao hm hn, n khng ch cung cp m h thng

truyn ti m cn cc chc nng nh ni kt, nh a ch, ng nht ngn ng, dng thng tin...1.1.2,2 Cc dch v vin thng

- Thoi: S trao i thng tin bng ting ni, vi u cui l my in thoi. Dch v thoi l dch v tri rng nht trong loi hnh vin thng. Dng in thoi, trn thc t ta c th gi mi ni trn th gii.

- Telex: Thit k mng telex da trn thit k mng in thoi, vi cc u cui l my telex thay v my in thoi. Tuy nhin, vic truyn cc k t khng phi l m thanh m bng cc m do cc mc in p to nn. Tc chm (50bits/s), khng k mt s k t c bit th ch c ch ci mi c truyn i.

- Teletex: N c th s dng nh telex thng thng nhng tc l 2400 bits/s thay v 50 bits/s. Hn na, n c b k t bao gm ch ci v ch con. Cng c th lin lc cho vi cc thu bao telex. Vn bn c thu bao tho ra, bin tp, lu gi v gi n thu bao khc trong mng. Do , tc truyn cao, dch v ny tich hp vi cc t liu ln m vi cc dch v telex c l qu t v tn thi gian.

C cc s dch v c a ra, nh cc con s rt gn, truyn t ng n mt hoc nhiu a ch lu gi... khng cn phi gim st thit b v n c m lin tc. Thng tin c nhn lp tc c'ct gi cho n khi c c v c x l.

- Facsimile: Dch v ny cho php truyn thng tin hnh nh gia cc thu bao. Cn c mt thit b c bit c v pht nh tnh.

- Videotex: Dch v Videotex c khai thc trn mng in thoi. S dng cc thit b tng i cm gin nh my tnh c nhn l c th tm gp s

20

lng ln cc c s d liu. Videotex lm vic tc 1200 bits/s trn hng c s d liu n thu bao v 75 bits/s trn hng thu bao n c s d liu. i vi ngi cung cp thng tin trong h thng, tc truyn l 1200 bits/s trn c hai hng.

- S liu: Bao gm tt c cc loi hnh truyn thng, , my tnh c dng trao i, truyn a thng tin gia cc ngi s dng1.1.2.3 Mng s a dch v (ISDN)

Hnh 1-10: Mng ISDN lin kt dch v.y l phong tin vt mang cho cc dch v khc nhau, nhng n l mt

th thng nht m khng phi l t hp ca cc h thng khc nhau. Chng ta ch c mt vt mang l ISDN. l mng s lin kt dch v v mi hnh thi dch v u c cung cp. c t li ca ISDN l mt mng vin thng s ho hon ton, , cc thit b u cui u l cc thit b s dng k thut s v thu bao s ni tt c thit b ca mnh vo cng mt i dy.

1.2 TNG QUAN V TNG I IN THO

1.2.1 Lch s v xu hng pht trin ca tng i

1.2.1.1 Lch s k thut tng iTrong sut lch s pht trin ca loi ngi, u tin trao i nhng

tm t, tnh cm, nhng kinh nghim sng v u tranh sinh tn, ngi ta dng

21

nhng c ch, hnh ng, ting ku n gin truyn t cho nhau, lc ny s giao tip l rt kh khn. Vic pht minh ra ngn ng c th xem l mt cuc cch mng truyn thng u tin ln nht. Ngn ng c th biu t hu ht nhng g c th xy ra trong cuc sng, tuy nhin, ting ni ch c th c truyn i vi mt khong cch ngn. Sau khi tm thy la, con ngi dng n lm phng tin truyn tin i xa c nhanh chng v c hiu qu, nhng vn cn mt s hn ch nh thi tit, i hnh... v tnh an ton thng tin l khng cao. Mi n khi ch vit ra i th con ngi c th truyn thng tin m khng b gii hn v ni dung v khng gian nh trc y na. T pht sinh nhng dch v th bo c kh nng truyn i t nhng ni rt cch xa nhau. Tuy nhin, con ngi lc ny cn n mt h thng truyn thng an ton hn, cht lng hn v hiu qu hn.

Nm 1837, Samuel F. B Morse pht minh ra my in tn, cc ch s v ch ci c m ho v c truyn i nh mt phng tin truyn dn. T kh nng lin lc, trao i thng tin c nng cao, nhng vn cha c s dng rng ri v s khng thn thin, tng i kh gi nh ca n.

Nm 1876, Alecxander Graham Bell pht minh ra in thoi, ta ch cn cp ngun cho hai my in thoi cch xa nhau v ni vi nhau th c th trao i vi nhau bng ting ni nh m c ca con ngi t ngn xa n thi by gi. Nhng cho nhiu ngi c th trao i vi nhau ty theo yu cu c th th cn c mt h thng h tr.

n nm 1878, h thng tng i u tin c thit lp, l mt tng i nhn cng in t c xy dng New Haven. y l tng i u tin thng mi thnh cng trn th gii. Nhng h tng i ny hon ton s dng nhn cng nn thi gian thit lp v gii phng cuc gi l rt lu, khng tha mn nhu cu ngy cng tng ca x hi.

gii quyt iu ny, nm 1889, tng i in thoi khng s dng nhn cng c A.B Strowger pht minh. Trong h tng i ny, cc cuc gi c kt ni lin tip tu theo cc s in thoi trong h thp phn v do gi l h thng gi theo tng bc. EMD do cng ty ca c pht trin cng thuc loa ny. H thng ny cn gi l tng i c in v nguyn tc vn hnh ca n, nhng vi kch thc ln, cha nhiu b phn c kh, kh nng hot ng b hn ch rt nhiu.

22

Nm 1926, Erisson pht trin thnh cng h tng i thanh cho. c c im ho bng cch tch hon ton vic chuyn mch cuc gi v cc mch iu khin. i vi chuyn mch thanh cho, cc tip im ng m c s dng cc tip xc c dt vng v cc c tnh ca cuc gi c ci tin nhiu. Hn na, mt h thng iu khin chung iu khin mt s chuyn mch vo cng mt thi im c s dng. l cc xung quay s c dn li vo cc mch nh v sau c kt hp trn c s cc s quay c ghi li chn mch ti sinh. Thc cht, y l mt tng i c sn xut da trn c s nghin cu k thut chuyn mch v hon thin cc chc nng ca tng i gi theo tng bc, v vy, n khc phc c mt s nhc im ca chuyn mch gi theo tng bc.

Nm 1938, hng Ericsson (Thy in) c pht minh u tin v trng chuyn mch in thoi dng n in t c kh.

Nm 1940, hng BELL (M) pht minh ra phng php chuyn mch l tip im (tin thn ca chuyn mch ta ). Sau , nm 1943, hng BELL (H Lan) thit k h thng tng i c b chn in c kh kiu qut, lm vic theo nguyn l cn in t.

Nm 1945, hng CGCT (Php) thit k tng i in t u tin theo nguyn l chuyn mch thi gian.

Nm 1947, hng PHILIPS (H Lan) thit k tng i in t dng n in t c kh.

Nm 1953, hng BELL (M) thit k h thng tng i cn in t DIAD chuyn mch rle, iu khin c s dng b nh bng trng t.

Nm 1954, hng BELL (H Lan) a vo sn xut v cho khai thc th ti NAUY tng i 8A dng trng chuyn mch ta v iu khin in t. Cng nm ny, hng VT (Tip Khc) cng sn xut tng i in t 10 s. Dng chuyn mch bng n in t c kh.

Nm 1957, hng CGCT (Php) sn xut hng loi tng i c nh 20 s dng trn cc tu chin. Loi tng i ny s dng cc mch in iu khin bng xuyn t v trng chuyn mch bng iot.

Nm 1959, hng BELL( M) a ra thit k u tin v h thng thng tin hp nht PCM ESSEX v mu thc nghim c a ra khai thc th.

23

Nm 1960, hi ngh quc t v cc vn lin quan n tng i in t c t chc v c 3 nm t chc mt ln. Cng trong nm ny, hng BELL (M) cho khai thc tng i in t mang tnh thng dng bang Morrise (M).

Nm 1962, hng SIEMENS (c) cho chai thc tng i in t thng dng ESM. ng thi ti Anh cng cho sn xut v khai thc th tng i chuyn mch thi gian. Hng ERICSSON cng cho sn xut loi tng i ny dng cho mc ch chin tranh. Cng trong nm ny, ti Tip Khc sn xut cc tng i in t c quan loi nh.

Nm 1963, hng STANDARD ELEKTRIK LOREN (c) sn xut v a vo s dng tng i cn in t thng dng u tin HEGOL.

Nm 1965, tng i ESS s 1 ca M l tng i in t c dung lng ln ra i thnh cng, m ra mt k nguyn cho tng i in t. Chuyn mch tng i ESS s 1 c lm bng in t, ng thi, vn hnh v bo dng tt hn, c bit, tng i ny trang b chc nng t chun on v vn hnh theo nguyn tc SPC v l mt tng i ni ht. Cng M, hng Bell System Laboratory cng hon thin mt tng i s dng cho lin lc chuyn tip vo u thp k 70 vi mc ch tng cao tc truyn dn gia cc tng i k thut s.

Thng 1 nm 1976, tng i in t s chuyn tip hot ng trn c s chuyn mch s my tnh thng mi u tin trn th gii c lp t v a vo khai thc. K thut vi mch v k thut s pht trin y nhanh s phttrin ca cc tng i in t s vi kh nng phi hp nhiu dch v vi tc x l cao, ngy cng ph hp vi nhu cu ca mt thi i thng tin.

1.2.1.2 Xu hng pht trinCng vi s pht trin nh v bo ca cng ngh in t, cng ngh thng

tin ni chung v cng ngh thit b chuyn mch v ang c nhng bc tin nhy vt. Trong thi gian ti k thut chuyn mch tp trung vo nhng vn ch yu nh sau:

- Tip tc hon thin an ton, rt gn cu trc phn cng, pht trin thm cc dch v mi.

24

- Hon thin cc phn mm m bo an ton cho vn hnh, bo tr v cho ngi s dng.

- Tip tc pht trin cao phn mm ng dng m, p ng nhu cu ngy cng tng ca ngi s dng dch v.

-Pht trin tip theo hng hon chnh ISDN (Integrated Services Digital Network- Mch s lin kt a dch v) v m rng phm vi s dng B- ISDN (Broadband ISDN - Mng s lin kt a dch v bng rng). Tng cng thng tin theo cng ngh ATM (Asynchronous Transfer Mode - Phng thc truyn khng ng b), p ng nhu cu dch v a phng tin (Multimedia).

- Tip tc hon thin cc tng i theo cng ngh chuyn mch quang.

1.2.2 Phn ioi tng i in t1.2.2.1 Phn loi theo phng thc chuyn mch

-Chuyn mch phn knh khng gian: cu trc cc mt (cc tip im) chuyn mch l cc linh kin in t hai trng thi: n in t, tranzito hay IC. Loi ny hin nay vn ang s dng.

- Chuyn mch phn knh theo thi gian: ang c s dng.- Chuyn mch phn knh theo tn s: hin thi khng s dng trong vin

thng.-Chuyn mch phn knh theo bc sng (chuyn mch quang): ang

nghin cu s dng trong tng lai.- Chuyn mch s: s dng nguyn l PCM. y l phng thc rt ph hp

cho h thng thng tin hp nht v a dch v, h thng thng tin s, truyn s liu. Xt v mt kinh t v k thut thi trong giai on hin nay y l phng thc u vit nht.L2.2.2 Phn loi theo phng thc iu khinTheo phng thc ny, vic iu khin trong tng i in t c chia thnh hai loi:

- Tng i in t iu khin phn tn: phng thc ny ging nh nguyn l iu khin trong tng i c in. Gm c cc thit b nhn dng, ghi pht ring bit v .v ... cc thit b iu khin u c in t ho.

- Tng i in t iu khin tp trung (iu khin bng chng trnh): loi ny vic iu khin u tp trung thit b logic trung tm (CPU). Thit b CPU

25

ny s thng qua cc thit b giao tip ngoi vi iu hnh mi hot ng ca tng i.

- v mt cu trc logic th thit b i khin c th chia lm hai loi:+ iu khin theo chng trnh c lp sn (SPC).+ iu khin theo chng trnh c lp ra tc thi bi cc mch in logic.

Tng i

Nhn cng T ng

T thch Cng in Chuyn mch in c

Chuyn mch in t

Chuyn mch khng gian

Chuyn mch thi

gian

Chuyn mach tn s

iu khin c in trc tip

iu khin in mch cng

iu khin in t chng trnh

in t chn khng gian

in t chn thi gianPAM PCM

Hnhl-11: M hnh phn loi tng qut.

26

1.2.2.3 Phn loi theo v trHin nay, cc tng i c phn thnh bn loi:

- Tng i quc t.- Tng i chuyn tip quc gia.- Tng i chuyn tip vng.- Tng i ni ht.

Ngoi ra c mt s tng i nm gia tng i ni ht v tng i chuyn tip vng, l tng i c nhim v ni ht v chuyn tip.

Cch phn loi ny cng l cch phn loi da trn quan im lu lng. Tng i ni ht lm nhim v chuyn mch, phc v cc cuc gi ni ht

(ni i), t chc cc cuc lin lc t trong ra qua cc ng trung k ra, hoc cc cuc gi t ngoi vo qua cc trung k vo hoc trung k vo - ra.

Tc x l ca tng i thng l 100 cuc gi/giy do tc x l ca mch vi x l v tc chuyn mch quy nh.

Tng i chuyn tip nhm phc v cc cuc gi chuyn tip (tc l gi ng di), tng i chuyn tip th tc x l nhanh hn tng i ni ht (khong 150 cuc gi/giy v ln hn).1.2.2.4 Phn loi theo tt hiu C 2 loi;

- Tng i tng t (analog).- Tng i s (digital).

1.3 TNG I IN T S SPC

1.3.1 S pht trin ca tng i in t SPCCc tng i in t hon ho l biu hin s kt hp thnh cng gia k

thut in t - my tnh vi k thut in thoi. Cc du hiu thnh cng xut hin t nhng nm 60 ca th k 20. Sau hai thp k pht trin, cc th h ca tng i in t cha ng nhiu thnh tu t s pht trin ca k thut in t. S pht trin ny c thc y bi nhu cu gia tng cht lng, ci thin gi c, tnh duy tr v linh hot ca cc tng i c in, v nh vo khai thc cc u im tuyt i trong k thut in t v my tnh.

ng dng u tin ca cc thit b in t vo cc tng i in thoi thuc v lnh vc iu khin: stored-program control. Tng i SPC cng cng

27

u tin l lESS c pht trin bi cc phng th nghim ca AT&T Bell, c gii thiu ti Succasunna, New Jersey, USA vo thng 5 nm 1965. S kin lch s ny khi u s quan tm ca ton th gii vo SPC, kt qu trong nhng nm 70, mt s cc h thng tng i mi dng k thut iu khin my tnh vi cc mc khc nhau ra i. Tuy nhin, cc h thng u tin ny tt c dng cc thit b chuyn mch c v vp phi cc vn trong vic pht trin cc dy chuyn mch bn dn ph hp vi ng dng in thoi cng cng.

C hai tr ngi cn tr vic dng cc chuyn mch bn dn cho tng i in thoi. Trc tin l kh ch to mt ma trn chuyn mch bn dn ln vi c tnh xuyn nhiu thp. Cc chuyn mch hnh thnh nn cc ma trn nh vy yu cu tr khng ng nhp rt cao nu mun cc nhiu b loi tr. Lm vic trong ch tng t, cc chuyn mch bn dn khng th so b c vi c im truyn tuyn tnh v tr khng ng nhp gn nh v hn ca cc chuyn mch c. Tr ngi th hai, cc thit b bn dn khng chu c cc mc in p cao cng nh dng in chung theo chun in thoi.

Mt u im rt quan trng ca chuyn mch s l b cc thit ghp knh thng thng lin quan n cc h thng truyn dn PCM kt cui ti tng i.

Do , mt trong nhng ng lc chnh cho vic ng dng chuyn mch s vo mng in thoi cng cng l kh nng b cc thit b chuyn i analog sang digital trong cc trung k cng nh mng hp ni.

Cho n nhng nm u ip nin 80, cc mch tch hp c ch to rng ri lm gim gi inh cc b chuyn i AD, cho php gi c ca cc mch giao tip ng dy iu bao gim xung to iu kin cho cc h ing dng s hon ton cnh anh c vi cc h ting lai analog-digital ni n. Cc h ng tng i SPC hin ti gm chuyn mch in t v iu khin ieo chng trnh. Ngoi cc ngoi l ong mt vi inh phn ong cc mch giao tip iu bao, cc tng i ny hon ton dig k iut s.

Tuy nhin, tc pht trin nhanh chng ca k thut bn dn c tip din t ra nhiu chn la cho cc nh thit k h thng tng i SPC.

Giai on t nm 1974 n nm 1976 l giai on pht trin nhanh nh v hiu qu nht ca cng ngh in t s trong tng i in t. Nhiu cng ty,

28

trong c nhng cng ty mi chuyn hng sang lnh vc chuyn mch in thoi gii thiu cc sn phm ca mnh.Bng 1-1 gii thiu mt s tng i in t trn phm vi th gii theo th t thi gian bt u sn xut ca n.

Bng 1-1. Mt s Tng i tng t

* r

tng i in t theo th t thi gian sn xut.

Nm K hiu Loi tng i Hng sn xut1965 Nol ESS Ni ht Bell Labs M1969 No4AXBETS Chuyn tip Bell Labs M1972 DIO Ni ht v chuyn tip NEC - Nht1973 Metaconta Ni ht LMT - Php1974 Nol ESS Ni ht v chuyn tip Bell - M

EWSO Ni ht Siemens - cPRX - 205 Ni ht Philips - H Lan

1975 Droteo Ni ht v chuyn tip Proteo - Italy1976 AXE Ni ht PTT, L.M Ericsson -

Thy in

Tng i p dng k thut s

Nm Nhn hiu Loi tng i Hng sn xut1970 E IO -A Ni ht CI T v CNET - Php1976 No4 ESS Chuyn tip Bell - M1978 AXE Ni ht LM Ericsson-Thy in1981 EIOB Ni ht v chuyn tip CI T Alcatel - Php

E12 Chuyn tip CI T v CNET - PhpFETEX Ni ht v chuyn tip Fujisu - NhtNEAX61 Ni ht v chuyn tip NEC - NhtEIO Alcatel NI ht v chuyn tip Alcatel - Php

29

Bng 1-2. Mt s loi tng i in t v cc c trng k thut (cc tng i dung lng trung bnh v l'n).

Loi nc sn xut

Dung lng (nghn thu bao hay

trung k)

Kh nng lu thot ti hoc x l gi S lng (1979-

1982)Thu bao Trung k Ti(Erlangs)S cuc gi

u ni/sMNol ESS 10-65 6000 30 1939Nol ARSS 20- 128 32 10000 65 30(1978)No4A 22,4 6200 35 76XBESS 47500 150 29No4 ESSNht 98 107 4400 30 250DAO 13 2500XEl 240 60 24000 194FETEX150 2 - 100 2,5 - 60 27000 194 2057(91)NEAX61 30 2000 11 - 16 10EWSO 13 5000 1EWSF 10 - vi Vi chc 0,8er/T.B 70 - 280 2500EWSD trm (1992)AnhTXEItaiy 40 5000 60 80Proteo 15Thy in 30AXE 64 10000 35H lanPRX205 10 1000 10- 15 60PhpEIOB 30 4 2400 - 2600 25 300(1982)Metuconta 10-60 10000 83 - 100 20E12 65 15000 86 8(1981)MT20 64 20000 83 - 100 1EIO Alcatel 200 60 25000 200 1

30

1.3.2 u im ca cc tng i k thut s SPCTng i k thut s SPC c nhiu u im i vi s qun tr v cc thu

bao ca n. Tuy nhin, cn phi ni rng cc kt qu u xut pht t cc u th ca SPC, do cc tng i SPC analog cng s c u im nh vy. Hn na, ton b cc u im s khng pht huy cho n khi cc tng i k thut s SPC c dng phi hp vi mt mi trng truyn dn s. Cc u im ca SPC bao gm:L3.2.1 Tnh lnh hot

Trong cc chng sau s m t phn cng trong tng i SPC c iu khin v d liu c lu tr trong cc b nh nh th no. Qu trnh x l iu khin ny to ra tnh linh hot mc cao trong vic iu khin phn cng. Tnh linh hot c cc kha cnh v tc dng lu di v ngn hn.

Tc dng lu di c xem xt trc tin. Trong giai on pht trin h thng chuyn mch, mt lot cc chong trnh c th c to ra cho php mt h thng chuyn mch c bn h tr cc kh nng v dch v ph hp vi nhu cu qun l. S hiu chnh phn mm ny p ng cc c tnh tng qut ca tng i cc b trong mng, v d nh nh s, tnh cc, cc lut nh tuyn, cc loi cuc gi c h tr, qun tr v cc tin ch thu bao.

Mt c trng quan trng ca cc h thng SPC l kh nng mt tng i c th c nng cp m khng ph b cc dch v sn c. iu ny cho php cc kh nng v tin ch mi c phi hp trong hot ng ca h thng . Mt vi tng cng c th t c ch n gin ci t thm mt phn mm mi, v d nh to ra tin ch nhm user thn thin cho mt loi thu bao no . Cc tng cng khc nh chu-yn mch d liu i hi phi thm phn cng mi.

Tnh linh hot ca SPC cn c cc tc dng ngn hn nh kh nng thay i trng thi ca thit b tng i ch cn thao tc n gin l thay i d liu. Do , hot ng ca tng i c th thay i mt cch nhanh chng theo cc iu kin mng. V d cc gii thut nh tuyn c th thay i c, cc cuc gi c th nh tuyn li trnh tc nghn trong mng. Tc dng ngn hn ca tnh linh hot cho php mt lot thao tc qun tr v tin ch thu bao c cung cp mt cch c kinh t v d iu hnh.

31

.3.2.2 Cc in ch thu baoCc tng i SPC cho php hng lot cc tin ch thu bao c cung cp

r hn v d hn trong cc tng i khc. Cc tin ch ny c phn phi bi h thng qun l khi thy thch hp. Sau nhiu tin ch c yu cu bi cc thubao trn c s call - by - call mt s tin ch thu bao nh:

- Short - code dialling: Cc s in thoi thu bao chn trc c gi bng cch quay cc m ngn nhp vo t trc.

- Call transfer: Cc cuc gi n mt in thoi no c chuyn hngn mt s in thoi khc mt cch t ng.

- Ring back when free: Tng i c yu cu thit lp mt kt ni n mt thu bao in thoi ang bn cng sm cng tt ngay sau khi n kt thc m thoi.

-Automatic alarm call: Tng i rung chung ti mt thi im xc nh trc hng ngy.

- Outgoing hay incomming call barring: Cho php ch nhn ca my in thoi ngn cn cc cuc gi i cng nh cc cuc gi ti.

- Itemised billing: Cung cp cc ho n lit k chi tit cc cuc gi v s tin phi tr.

- Malicious - call tracing: Cc thu bao hay c quan c thm quyn c cnh bo ngun gc ca mt cuc gi quy ri.

- Centrex: Tng i ni ht h tr cho vic m rng thng tin trong mt h thng ring ca thu bao. Thm cc tin ch vo PABX, cc thu bao s c dch v in thoi thng thng cho cc cuc gi i v n h thng ring ca h.

Nhiu tin ch trn i hi kh nng bo hiu thu bao, v d nh c h tr bi cc in thoi n phm a tn. Tng t, s m rng cc tin ch ny vt qu kh nng ca tng i, n yu cu mt kh nng bo hiu lin i thch hp, v d nh h thng bo hiu s 7. V d cc bo hiu nh vy cho php mt cuc gi c chuyn n mt vi tng i khc mt cch t ng.

Cc tin ch trn cng c th trong cc tng i SPC tng t v nhiu tng i khng phi SPC cho d kh khn hn v gi c cao hn.

32

1.3.2.3 Tin ch qun trTng i SPC cung cp mt di rng ln cc tin ch qun l, nhng cng

vic m trc kia l t tin hoc.mt nhiu cng sc. Hu ht cc hot ng hng ngy trn tng i cn phi dng cc tin ch ny, c truy xut thng qua cc u cui my tnh lin kt v tng i nm ti trung tm iu khin hoc t xa.Mt s cc tin ch qun l l:

- iu khin cc tin ch thu bao; Cho php thay i danh sch cc tin ch sn c ca thu bao.

- Thay i nh tuyn: Nh c cp trn, mt nhn vin iu hnh c th thay i nhanh chng vic chn tuyn c dng bi tng i nhm hng cc cuc gi n cc tng i khc. Cng vic ny c tin hnh khi vp phi cc vn tc nghn tm thi hay cn thay i lu di trong k hoch nh tuyn.

- Thay i s ca thu bao v cc m trung k: iu ny c th c m trch bi mt ch th n qua mt u cui iu hnh.

- Xut cc thng tin thng k qun l tng i: Cc thng tin cn thng k bao gm s chim dng cc thit b ti cc thi im xc nh, d liu v cuc gi thnh cng, cc chi tit v tc nghn trn cc tuyn, chi tit cc cuc gi thu bao. Thng tin ny c th c sn khi in ra hay hin ln mn hnh mt cch cc b ti tng i v ti cc trung tm iu hnh qun l mng xa. Ngoi ra chng c th c ghi vo cc thit b lu tr hoc a ra trn cc lin kt d liu phc v cho vic x l.

- Cc cng c bo tr: Bao gm s khi to cc kim th v ghi kt qu mt cch t ng, x l cc cnh bo, cc chng trnh chn on h tr cho cc frame b li.1.3.2.4 Cc u im iim vo ca k thut s

Vic dng cc chuyn mch s trong cc tng i SPC lm tng thm mt s cc u im sau: Tc thit lp cuc gi

Phn cng ca phn t iu khin trong tng i SPC hot ng vi tc cao vi mc in p thp (thng l 5VDC). Do , trong cc tng i SPC vi cc chuyn mch c vn chm v i hi hot ng vi in p v dng in cao s khng cn xng v tc cng nh nng lng gia h thng iu khin

33

v chuyn mch, v iu ny phi urc khc phc bi cc thit b m thch hp. Tuy nhin chuyn mch s hon tain bao gm cc cng bn dn v b nh nm di dng cc mch tch hp (IC), (chng hot n vi tc v mc in p tng thch vi cc h thng iu k.hiin, do hnh thnh mt tng i in t SPC hon ton l k thut s.

Cc cuc ni c th c thiit lp xuyn qua cc h thng chuyn mch s rt nhanh chng (thng l 250|i.s). iu ny kt hp vi kh nng tit kim v cc c tnh nonblocking cho php thc hin cc thit k h thng rt tit kim. Dng cc chuyn mch s cho) cc thit lp ng dn tun t gia cc h thng tng i ph trong giai on kt ni cuc gi. Ngoi ra cc n lc lp li t ng xuyn qua cc chuyn mch (trnh tc nghn trong mng) c th c thc hin m khng vp phi s nhn bit s gia tng thi gian tr khi quay s. Kt qu l chuyn mch s cng vi SPC cho php cc kt ni phc tp ca cuc gi trong tng i c thit lp m ch dng cc thit k chuyn mch n gin v r tin. Tit kim khng gian

Cc h thng chuyn mch s nh hn nhiu so vi tng i analog c kh nng tng ng. iu ny c c l do s dng cc mch tch hp v b ghp knh c ln l kh thi v k thut bn dn hot ng vi tc cao c p dng.

Tuy nhin, kh nng tit kim khng gian c th b gim i nhiu do vn cn tn ti cc thit b chuyn i tng t sang s (AD) cn thit kt ni cc ng analog. Do vy, ti thiu nh hng ny cn ti a t l mch s trong cc mch kt ni ti tng i. Ngoi ra kh nng ti thiu khng gian ca tng i cn b gim do cn phi cung cp iu kin gii nhit cng nh mt mi trTig cho iu khin tng i. Trong vi trng hp cn s dng cc thit b cp ngun cho tng i khi h thng s SPC c ci t trong mt tng i. Cho d c cc iu kin hn ch nhng kch thc ton b ca tng i k thut s SPC thng thng vn nh hn 15Vo so vi cc tng i bc (step - by - step) v 50% so vi cc h thng tng i analog SPC.

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D dng bo trCc thit b dng trong cc tng i k thut s SPC c mt t l li thp

hn cc thit b c dng trong cc tng i analog SPC v khng c cc thnh phn vt l phi di chuyn v tha hng tnh tin cy ca k thut bn dn. Ngoi ra khng ging vi cc tng i bc (step - by - step), h thng s khng yu cu bt k s iu chnh thng xuyn no. Cc chng trnh cn on trong h thng iu khin tng i thng cho php nh v nhanh chng cc li phn cng, li thuc modul c bit hay cc n v lp ghp ngoi vi no. y thch hp cho vic dng thit b phn cng d phng, cho php h thng iu khin lu dch v mt cch nhanh chng bng cch t ng cu hnh li thit b, thay th n v h hng bng mt n v d phng khc. Sau , h thng iu khin cung cp cc thng tin cn thit cho ban bo tr thay th cc n v hng hc theo cch thc c hoch nh. Cc n v h hng lun c gi n cc trung tm sa cha chuyn ngnh. Do vy, cng vic bo tr phn cng chm hn so vi vic bo tr trong cc tng i analog.

Cc li c th xy ra ngay trong phn mm ca tng i cng nh trong phn cng ca n. Li phn mm c th c xc nh t ng v c bng tay. Qu trnh bo tr phn mm c thc hin d dng bi hng lot cc chng trnh chn on v cc thng bo li c cung cp bi h thng iu khin tng i. Cht lng ca CIIC gi

C ba u im truyn dn quan trng i vi cc mng dng chuyn mch v truyn dn s (mng s tch hp). Trc ht ton b tht thot truyn dn ca mt cuc ni xuyn qua mng l c lp vi s lng cc chuyn mch v cc lin kt truyn. Hn na, ton b tht thot do bi cc qu trnh chuyn i AD ti mi u kt ni. iu ny cho php ti thiu ting n lm cho mc nghe ca thu bao tt hn, n nh hn v kim sot c ting di. Th hai, bi v ting n khng c tc ng ln h thng truyn dn s, cc thu bao nhn thy cc mc n t hn nhiu so vi cc kt ni qua mng analog. Th ba, cc tng i ni ht s c cc card giao tip ng dy c kt ni mt cch c nh n cc ng ni b hai dy. iu ny ci tin tr khng ph hp vi thit b chuyn i 2 dy sang 4 dy, a n kt qu l cc vn v bt n nh t hn so vi cc

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mng analog chuyn mch hai dy. (iu khin ci thin tr khng nh vy l rt quan trng bi v so vi cc mng analog, cc mng s c xu th tht thot im ni im t^p hn, nhng thi gian tr li gia tng, do tnh hnh xu hn so vi echo). Kh nng cung cp cc dch v phi thoi (non - voice services)

Truyn dn s l mi trng l tng cho truyn dn ti t cc u s liu v my tnh, cc ti ny c ngun gc thuc dng tn hiu s. Truyn s liu r v hiu qu hn qua h thng s so vi qua h thng analog, c bit vi tc ln hn 4,8 kbps bi v cc tn hiu s c th c mang mt trc tip khng cn dng cc modem m tn cng nh phi gi c cao v cc gii hn v lu lng. Cc tn hiu analog c m ho di dng s (v d nh audio v video) c th trn mt cch t do vo ti c ngun gc s v c vn chuyn qua mt phng tin chung m khng c s nn p nng lng ph vo nh khi tn hiu a dng ny c truyn qua cc h thng truyn dn analog. Do , cc tng i k thut s khi lin kt vi truyn dn s c kh nng cung cp nhiu dch v r tin thm vo h thng in thoi. Gi c

Nhn chung cc h thng tng i k thut s SPC tit kim hn so vi cc h thng analog tng ng, v gi u t c th thp hn nhiu. Tuy nhin, cc kha cnh v gi thay i v din tin phc tp khi s dng cc tng i in thoi. Cng nh gi u t thit b chuyn mch, khi s u t bao gm cc gi v v tr lp t, ngun nng lng, h thng h tr iu hnh v bo tr, phong tin lp t, ti liu, ban hun luyn, lin kt vi cc mng khc. Khi quyt nh chn la cc h thng chuyn mch, cc cng c qun l cng cn phi cn nhc hu qu do gi c thay i. Vic d dng nng cp h thng vi cc tin ch mi cng c th c phn nh thng qua gi c. Tt c cc yu t ny chi phi ton b gi c hot ng ca mt h thng tng i. Thi gian lp t

Thi gian lp t cc tng i k thut s SPC t hn so vi thi gian lp t cc tng i analog c dung lng tng ng. iu ny c c l do th tch vt l nh v s modul ho cc thit b s. S lp t nhanh chng cng xut

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pht t nhu cu kim th trc ca nh ch to v s ch to cc n v thit b di dng lp ghp ang c dng trong cc tng i SPC hin i. Bo hiu knh chung

Mt thnh phn quan trng ca tng i k thut s SPC l bo hiu knh chung (CCS), n cung cp kh nng lin lc nhanh chng gia cc h thng iu khin ca cc tng i nh vy trong mt mng. Vi mc n gin nht, ngi dng thc hin cuc gi xuyn qua mt mns s dng CCS rt mun thi gian cn thit to cuc ni rt ngn. Ngoi ra, CCS cho php mt s cc dch v thu bao c m rng xuyn qua mng. Ngoi ra, trong cc cuc gi phi thoi v iu hnh, mng CCS ne gp gi tr ln nht vo cc tng i k thut s SPC. CCS c kh nng truyn mt s thng bo lin h n cc cuc gi thoi v d liu cng nh thng tin iu khin v qun tr khng lin h trc tip vi cc cuc gi ch nh, gia cc tng i v t cc thu bao n tng i .

1.3.3 S khi chc nng ca tng i s SPC1.3.3.1 S khiTng i SPC gm cc b phn chnh sau:

- Thit b kt cui cc ng dy thu bao, trung k tng t v trung k_ S.

- Khi ni dy SWM ( Switching modul ): C th l chuyn mch tng t hoc chuyn mch s.

- Ngoi vi bo hiu: Thit b bo hiu knh chung v ring.- Ngoi vi chuyn mch gm:

+ Thit b iu khin u ni (maker).+ Thit b d th mch dy (qut - Scanner).+ Thit b ngoi vi phn phi tn hiu.

- B iu khin trung tm gm; Mch vi x l v cc b nh s liu, nh chng trnh v.v...

- Ngoi vi trao i ngi - my cho iu hnh, bo dng.

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Thu bao

Thit b kt cui TU

A ------------- BKhi chuyn mch

Trung k tng

Trung kXs

Ngoi vi bo hiu

Ngoi vi chuyn mch

Ngoi vi trao i B iu khinngi - may

1.3.3.2 Chc nng Khi kt cui TU (Terminating Unit)

C chc nng kt cui cho cc ng dy thu bao (tng t v s); cc ng dy trung k (tng t v s) cng nh cho cc thit b nghip v. N gm cc khi ch yu di y:

* Khi kt cui ng dy thu hao (SLTU)C nhim v truy cp ti cc ng dy thu bao, giao tip vi cc phn

ghp knh tn hiu s ca thit b kt ni. y chnh l cc mch in Tig dy thu bao, chng chu s iu khin ca khi iu khin ng dy thu bao. Mt n v iu khin ng dy thu bao ph trch mt nhm ng dy thu bao nht nh tu thuc loi tng i. Khi ny bao gm hai loi ch yu:

- Khi kt cui ng dy thu bao tng t: truy cp cc thu bao tng t, lm chc nng BORSCHT.

B (Batteryfeed): cp ngun cho ng dy thu bao theo cng thc cp ngun i xng.

0 (Overvoltage protection): bo v qu p cho thit b, bo m cho in p trn ng dy khng vt qu ngun cung cp.

R (Ring); thc hin cp tn hiu rung chung cho thu bao b gi.s (Supervision): gim st cc trng thi thu bao.c (Codec): thc hin m ho v gii m trc v sau b tp trung phn

phi thoi (chuyn i A -e> D). a s c ng dy thu bao hiu l nhng ng dy tng tr bi vy trc khi a vo trng chuyn mch s th cc tn hiu tng t phi c m ho thnh lung s PCM v khi a ra phi chuyn i t lung PCM thnh tn hiu tng t.

H (Hybrid): b sai ng thc hin chuyn i 2/4 y, pha bn thu bao ngoi theo hai hng, mt hng pht mt hng thu, mi hng hai dy.

T (Text): o th v kim tra to s liu cho vic qun l v bo dng h thng.

Ngoi ra khi giao tip thu bao cn c mch nghip v nh mch phi hp bo hiu, mch in thu pht xung quay s dng m thp phn v m a tm. cc tng i s, mch in thu bao cn lm nhim v bin i qua li A - D (Analog - Digital) cho tn hiu thoi.

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- Khi kt cui ng dy thu bao s: truy cp n cc thu bao s. Chc nng ca BORSCHT khng hon ton tp trung mt khi. Thu bao s c tc truyn ca ISDN (2B + D) th chc nng B, T, o nm trn SLT; H v c nm trn kt cui mng NTU (Network Temiinating Unit); chc nng s v R nm trn thit b thch ng u cui TA (Terminal Adapter).

* Kh kt cui ng dy trung k (TTU)i^m nhim v kt cui cc tuyn trung k, giao tip vi cc thit b truyn

dn thch hp phc v u ni thng tin lin i. N gm c:- Khi kt cui ng dy trung k tng t (ATTU): chc nng ch yu

ca n gm: bo v qu p; chuyn i 2/4 dy; m ho/gii m (A/D v D/A); cp ngun v chc nng bo hiu (s cp chi tit chng 4).

- Kt cui ng trung k s (DTTU): khi mch kt cui trung k s: nhim v c bn ca khi mch ny l thc hin cc chc nng GAZPACHO, bao gm:

+ To khung (Gerieration of Frame): tc l nhn dng tn hiu ng b khung phn bit tng khung ca tuyn s liu PCM a n t cc tng i khc.

+ ng b khung (Aligment of Frame); sp xp khung s liu mi ph hp vi h thng PCM.

+ Nn dy bt 0: v dy tn hiu PCM c nhiu qung cha nhiu bt 0 s kh phc hi tn hiu ng b pha thu nn nhim v ny l thc hin nn cc qung tn hiu c nhiu bt 0 lin tip pha pht.

+ o cc tnh (Polar conversion): nhim v ny nhm bin i dy tn hiu n cc t h thng a ra thnh dy tn hiu lng cc trn ng dy v ngc li.

+ X l cnh bo (Alarm Processing): x l cnh bo t ng PCM.+ Phc hi dy xung nhp (clock recovery): khi phc xung nhp t dy

tn hiu thu c.- Tch thng tin ng b (Hunt during reframe): tch thng tin ng b t

dy tn hiu thu.

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- Bo hiu (ofice Signalling); thc hin chc nng giao tip bo hiu phi hp cc bo hiu gia tng i ang xem xt v cc tng i khc qua cc ng trung k.

Hin nay c hai loi tc lung s c bn ang c s dng. l: H tiu chun Chu u vi lung c bn 2 Mbits/s. H Nht Bn v Bc M vi cc lung c bn 1,5 Mbits/s.* Cc khi c bn khcNgoi hai khi c bn nh trn, khi kt cui cn bao gm:- Khi ghp knh (MUX) ghp cc tn hiu thoi ca tng knh dng

s thnh lung s.- Khi kt cui ng truvn s to giao din ph hp gia khi chuyn

mch tp trung thu bao vi cc lung s s cp.- Khi chuyn mch tp trung thu bao chuyn mch ni b cc thu bao

trong mt n v kt cui khi khn cp. Bnh thng n lm chc nng tp trung lung s v pha chuyn mch nhm.

- Khi thit b nghip v bao gm: thit b to cc loi m hiu (Tone); thit b thu DTMF t thu bao ti; thit b thu m thanh nghip v. Khi chuyn mch

cc tng i in t, thit b chuyn mch l mt trong cc b phn ch yu v c kch thc ln. N c cc chc nng chnh sau;

- Chc nng chuyn mch: thc hin thip lp luyn ni gia hai hay nhiu thu bao ca tng i hoc gia tng i ny v tng i khc.

- Chc nng truyn dn: trn c s tuyn ni thit lp, thit b chuyn mch thc hin truyn dn tn hiu ting ni v tn hiu bo hiu gia cc thu bao vi tin cy chnh xc cn thit.

C hai loi h thng chuyn mch:* H thng chuyn mch tng t

Loi ny c chia lm hai loi:+ Phng thc chuyn mch khng gian (Space division Switching mode), phng thc ny, i vi mt cuc gi mt tuyn vt l c thit lp gia u vo v u ra ca trng chuyn mch. Tuyn ny l ring bit cho mi cuc ni v duy tr trong sut thi gian tin hnh cuc gi. Cc tuyn ni cho cc cuc gi

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l c lp vi nhau. Ngay sau khi mt tuyn c u ni, cc tn hiu c trao i gia hai thu bao.+ Phng thc chuyn mch thi gian: phng thc ny cn gi l phng thc chuyn mch PAM (Pule Amplitude Modulation), tc l chuyn mch theo phna, thc iu bin xung.

* H thng chuyn mch s (Digital Switching System)Phng thc chuyn mch ny cn gi l chuyn mch PCM ( Pulse Code

Modulation), h thng chuyn mch ny mt tuyn vt l c s dng chung cho mt s cuc gi trn c s phn chia theo thi gian. Mi cuc gi s dng tuyn ny trong khong thi gian xc nh v theo chu k vi mt tc lp thch hp. i vi tn hiu thoi tc lp l 8 kHz, tc l c mi 125 IS li truyn i ting ni mt ln. Ting ni trong mi ln chuyn i gi mu v c m ho theo phng thc PCM. Khi iu khin trung tm (x l chuyn mch)

B iu khin trung tm gm mt b x l c cng sut ln cng cc b nh trc thuc. B x l ny c thit k ti u x l cuc gi v cc cng vic lin quan trong mt tng i. N phi hon thnh cc nhim v kp thi hay cn gi l x l thi gian thc hin cc cng vic sau y:- Nhn xung hay m chn s (cc ch s a ch).- Chuyn cc tn hiu a ch i cc trng hp chuyn tip cuc gi.- Trao i cc bo hiu cho thu bao hay cc tng i khc.

S khi mt b x l chuyn mch tng qut c m t nh sau:

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Hnh 1-13: S khi b x l chuyn mch.B x l chuyn mch bao gm mt b x l trung tm, cc b nh

chng trnh, s liu v phin dch cng thit b vo/ra lm nhim v phi hp a cc thng tin vo v ly cc lnh ra.

B x l trung tm l mt b x l hay vi x l tc cao v c cng sut x l tu thuc vo v tr x l chuyn mch ca n. N lm nhim v iu khin thao tc ca thit b chuyn mch.

B nh chng trnh: dng ghi li cc chng trnh iu khin cc thao tc chuyn mch. Cc chng trnh ny c gi ra v x l cng vi cc s liu cn thit.

B nh s liu dng ghi li tm thi cc s liu cn thit trong qu trnh x l cc cuc gi nh cc ch s a ch thu bao, trng thi bn - ri ca cc ng dy thu bao hay trung k...

B nh phin dch cha cc thng tin v loi ng dy thu bao ch gi v b gi, m to tuyn, thng tin cc...

B nh s liu l b nh tm thi cn cc b nh chng trnh v phin dch l cc b nh bn c nh, s liu hay chng trnh trong cc b nh bn c nh khng thay i trong qu trnh x l cuc gi. Cn thng tin b nh tm thi (nh s liu) thay i lin tc t lc bt u ti lc kt thc cuc gi. Thit b ngoi vi chuyn mch

Lm nhim v m (hay giao tip) v mt tc x l v cng sut gia mch x l trung tm c tc iu khin cao, cng sut ra nh vi cc thit b ti c tc chm v tiu th cng sut ln. N gm cc b phn sau:

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* Thit b d ng dy:C nhim v pht hin v thng bo cho b x l trun tm cc bin c

mang tnh tn hiu ca cc ng dy thu bao, trung k. Trng thi tn hiu cc ng dy thu bao v ng trc a ti thng l khc nh au. i vi cc tn hiu chn s th cn phi d th tc 10 ms/ln, vi cc 1 'ng hp nh nng t hp, t t hp... th c th ko di vi trm ms. Nh vy d d th trng thi mch ng dy th b d th lm vic c sau khong 300 ITI Vln cho mi mch v mi ln d th tin hnh cho 8, 16 hay 32 ng thi.

* Thit b iu khin u ni:Lm nhim v thnh lp hoc gii phng cc cuc gi. N nKn tn hiu

iu khin t b x l trung tm, cc tn hiu ny l kt qu ca qu nh x l. Qu trnh x l gm: x l cc chng trnh, x l gi trn c s cc s liu v c s d liu thu bao v cc thng tin a ch. Qu trnh thit lp mt .uyn qua trng chuyn mch c thc hin ng thi qua cc tip.im u noi v sau khi xc nh trng thi thu bao b gi l ri.

tng i in t s, thit b iu khin u ni lm nhim v iu khin ghi v c cc mu tn hiu (hay cc bit) qua b chuyn mch thi gian ph hp vi a ch tuyn PCM v khe thi gian vo - ra. ng thi n cng iu khin cc tip im chuyn mch ca thit b chuyn mch khng gian s. Cc tip im ny c duy tr ng cho mt cuc gi no theo chu k tng ng vi khe thi gian dnh cho n. Nhng khong thi gian khc c duy tr ng cc tip im ny cho cc cuc gi khc.

* Thit b phi hp tn hiu:Nhm m v mt tn hiu gia ti c tc chm, tiu th cng sut ln

vi mch iu khin trung tm c cng sut nh, tc cao. N cung cp cc tn hiu ng dy nh: ng m cc rle, cp chung cho thu bao... di s khng ch ca iu khin trung tm.

H thng BusLm nhim v truyn dn a ch, s liu, cc lnh iu khin t b iu

khin truyn dn tn hiu qua Bus thng qua b x l trung tii (cho php Bus). N c th dng trc tip hoc ghp knh (Mux).

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H thong bo hiuTrong mng in thoi tn ti nhiu loi tng i khc nhau nh: nhn

cng, in c tng nc, ngang dc, cn in t, in t tng t, in t s v.v... Mi loi tng i c h bo hiu ring, do vy, mun ho mng th tng i in t phi c thit b phi hp bo hiu ph hp vi h thng bo hiu hin c.

+ Bo hiu dng mt chiu, a ch thp phn: cc thng tin trao i dng khng ch dng mt chiu, cc xung s c tc trong mt chui xung a ch 1- 10 xung. Tng i in t cn c thit b thu nhn dng bo hiu ny.

+ Bo hiu dng a tn; cc hng bo hiu u s dng t hp tn hiu m a tn thng bo trng thi v cc con s. Tng i in t cn c thit b phi hp vi cc dng tn hiu a tn khc nhau ca cc h thng tn hiu.

Tng i in t s dng hai phng thc bo hiu;+ Cc tn hiu c truyn dn chung trn knh ting ni hoc knh bo

hiu gn lin vi knh ting ni c gi l tn hiu bo hiu knh ring, tn hiu ny ring bit cho mi knh truyn dn.

+ Cc tn hiu bo hiu truyn dn chung cho mi cuc gi trn mt knh tn hiu ch cho tng i x l tt c cc cuc gi tng i v vo - ra, gi l bo hiu knh chung. Cc h thng bo hiu knh chung, thit b c chuyn mn ho, h thng c tc x l v truyn dn tn hiu cao, do vy lng thng tin qua h thng ln, ngoi ra h thng ny cn truyn dn c cc thng tin iu hnh mng li. Ngoi vi trao oi ngi - my

Lm vic hon ton tic tp theo cc chng trnh ghi sn iit b iu khin trung tm, h thng tng i in t cn c s can thip ca nhn vin iu hnh thng qua cc thit b ngoi vi trao i ngi - my. Thit b ny thng l nhng Display, Teletype, Printer tc cao. Chng c dng nhiu vo mc ch nh:

- Thay i hoc a vo cc dch v thu bao, thay i cc quy trnh to tuyn hoc cc chng trnh vn hnh...

- Thit b trao i ngi - my cn phi hp vi thit b iu khin trung tm nhm thc hin cc cng vic o th thng xuyn cho cc mch thu bao trung k. Kt qu o th c in ra giy bng my in tc cao.

- Thc hin chc nng iu hnh cc thit b nh trn bng t hoc a t. Cc s liu v lng ti, tnh cc... c tng i a ra thng qua cc thit b ngoi vi v ghi li trn bng t, a t. Khi cn thay i phn mm ng dng th

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cc chong trnh phn mm cn c thay i trc khi a vo b nh chnh v c ghi trc vo a t hay bng t.

- Thc hin chc nng cnh bo, nhn cc thng tin cnh bo v a vo cc lnh x l sai st, hng hc thng thng m h thng t ng khng th x l c.1.3.4 Phn tch mt cuc gi trong tng i SPC

e m t h thng chuyn mch, tin trnh ca mt cuc gi xem nh tri qua mi tng.

Thu bao gi Tng i

Tn hiu truy cp

Thu bao c gi

-----------------------

m mi quay s

Nhn dng thu bao gi

Phn phi b nh v cc thit b dng chung

Phn tch v chn knh xut

Thit lp ng dn Dng in chung

Cc ch s quay

m hiu chung.............

m thoi

Ct m hiu chung v dng chung

wTn hiu tr li

m thoi

Tn hiu gc myQun l

Ngt thit b

Tn hiu gc my

Hnh 1-14: Tin trnh mt CIIC gi c nh tuyn qua mt tng i ni ht.

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1.3.4.1 Tin hiu nhc my (off - hook)Mt thu bao mun thc hin mt cuc gi trc ht phi nhc ng nghe.

Tli tc cn thit ny pht ra tn hiu nhc my cn gi l tn hiu truy cp ng truyn, n thng bo vi tng i chun b iu khin cuc gi. Vic nhc ng nghe lm gii phng mt tip im, iu ny to thnh mt mch vng gia tng i v in thoi. Khi mch ny hnh thnh, mt thit b bn trong tng i c kch hot v mt lot cc tn hiu hng n cc phn thch hp ca tng i c khi pht. Khi ng nghe c t xung trng thi rnh ri, tip im b n xung tn hiu truy cp gi n tng i khng cn na, mch vng b ct v cuc gi khng thc thi, nh vy tit kim 'c nng lng. Nng lng trn ng dy thu bao c cp bi ngun pin trong tng i, v n yu cu mt chiu.1.3.4.2 S nhn dng ca liu bao gi

Cuc gi c pht hin ti n v kt cui ng dy thu bao (SLTU Subscriber Line Terminal Unit) thc hin gi trong tng i, n v ny c qui nh ch s thit b (EN Equipment number). Ch s ny cn c dch sang s th mc ca thu bao (DN_Directtory number). Do , cn phi dng cc bng dch. Trong tng i SPC, chng c gi trong cc b nh my tnh.H thng iu khin cng cn nhn dng thu bao v:

- Thu bao cn phi tr cc cho cuc gi.- Cn phi tin hanh kim tra xem thu bao c c php gi ng di hay

khng. Thng tin cn thit c lu gi trong cc record m t chng loi dch v ca thu bao.1.3.43 S phn phi b nh v cc thit b dng chung

Khi tng i nhn mt tn hiu truy cp (off-hook signal), h thng iu khin phi phn phi thit b dng chung cho cuc gi v cung cp ng dn cho n bt u t ng dy gi, hnh thnh nn mt nhm cc thit b chim dng lu, thit b ny cn thit trong sut cuc gi v loi thit b s dng ngn hn ch cn trong giai on thit lp cuc gi m thi. Trong cc tng i tng t, cu truyn dn phn tch ng ting mang tn hiu xoay chiu vi thanh phn mt chiu xuyn qua tng i l mt v d v loi th nht. Trong cc tng

47

i SPC n l record ca cuc gi, l vng nh b x:him gi trong sut qu trnh cuc gi. Loi th hai bao gm b thu v lu tr cc ch s cu thnh a ch thu bao c gi. Trong tng i SPC th cc ch s ny c lu gi trong b nh.L3.4.4 Cc ch s a ch

Sau khi nhn c m hiu mi quay s, thu bao nhp vo cc ch s a ch bng cch quay s. Cc ch s c gi di dng cc till hiu n tng i v c lu gi ti . Hot ng bo hiu l kha cnh ht sc quan trng trong h thng in thoi.u .4 .5 Phn tch ch s

H thng iu khin phi phn tch cc ch s xc nh tuyn i ra t tng i cho cuc gi. Nu cuc gi hng n thu bao thuc tng i ni b th s c nh tuyn n ng dy thu bao c gi. Nu ng dy ang lm vic vi cuc m thoi khc th tng i s gi tn hiu bo bn n thu bao gi. Mt khc nu cuc gi hng n tng i xa n c th c phn phi n bt c mt mch no trn tuyn thch hp i ra khi tng i gc. Nu tt c cc mch u bn, tn hiu bn cng c gi n thu bao gi. Neu c mt mch thch hp ang rnh, n s bt ly v khng th s dng cho bt k cuc gi no khc. Trong tng i c in, vic chim gi ny tc ng n mt iu kin v mc in p t vo thit b kt cui mch v c xem nh thao tc nh du. Trong tng i SPC th thng tin v mch thng c lu gi trong cc bng di dng phn mm, trong trng hp ny m ch nh trong vng d liu cho trc ch ra trng thi ca mt mch.1.3.4.6 Thit lp ng dn chuyn mch

Lc ny h thng iu khin bit c cc danh nh ca mch nhp v mch xut, sau chn ng dn gia chng thng qua chuyn mch ca tng i bng cc gii thut chn ng dn tng i thch hp. Mi im chuyn mch trn ng chn c kim tra m bo rng khng trong trng thi phc v cho cuc gi khc v chim ly n nu rnh. Trong cc tng i SPC c thc hin bng cch d v chn cc entry trong cc bng c xp xp.

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1.3.4.7 Dng chung v m hiu chungMt tn hiu phi c gi n u ra xa tin hnh cuc gi. Nu iu

bao c gi l cc b, iu ny c thc hin thng qua vic gi dng in chung n kch hot chung trong my in thoi c gi. Nu thu bao khng phi l cc b, mt tn hiu truy cp phi c gi n tng i k tip nhm kch hot n tin hnh cc thao tc ring. Cc thao tc ny cng tng t nh nhng thao tc trn, bao gm c cc tn hiu gi li tng i ngun. Khi tt c cc kt ni c thit lp cho php cuc gi tin hnh trn mng ni ht hoc mng hp ni hoc mng trung k, dng in chung c gi n thu bao u xa v m hiu chung c gi n thu bao gi.1.3.4.8 Tn hiu tr li

Mt tn hiu tr li nhn c t thu bao u xa hay t tng i khc, c nhn bit bi h thng iu khin ca tng i cc b. S truyn phi c chp thun trn ng dn chuyn mch chn xuyn qua tng i. Dng in chung v m hiu chung phi c xo trn ng dy thu bao u xa v thu bao gi, sau hai phn ny c ni vi nhau v cng vic tnh cc cuc gi ny vi thu bao gi c khi ng.1.3.4.9 Gim st

Trong khi cuc gi ang c tin hnh, cng vic gim st cng c thc thi tnh cc v pht hin tn hiu xo cuc gi. Cng vic gim st cng thc hin qut tt c cc dy kt cui trn tng i pht hin tn hiu truy cp ca cuc gi mi.1.3.4.10 Tn hiu xo kt ni

Khi nhn tn hiu xo kt ni (c pht hin bi thu bao gi hoc thu bao c gi), thit b tng i hay b nh c dng trong kt ni phi c gii phng v sn sng s dng cho cc cuc gi mi.

49

Thu bao gi Tng i cc b A n tng i k B

Hnh 1-15: Tin trnh mt cuc gi c nh tuyn qua mt tng i th 2.

50

Chng 2K THUT CHUYN MCH KNH

2.1 TNG QUAN V CHUYN MCH2.1.1 nh ngha

Chuyn mch l mt trong ba thnh phn c bn ca mng thng tin (bao gm: cc thit b u cui, cc h thng truyn dn v cc h thng chuyn mch). Mc ch ca chuyn mch

Thit lp ng truyn dn t ngun thng tin n ch theo mt cu trc c nh hoc bin ng thng qua cc mng v cc trung tm. Cc phng tmc chuyn mch chnh

- Chuyn mch knh.- Chuyn mch tin.- Chuyn mch gi.

2.1.2 Chuyn mch knh (Circuit Swithching)2.1.2.1 Khi nim

L loi chuyn mch phc v s trao i thng tin bng cch cp knh dn trc tip cho hai i tng s dng.

Chuyn mach

''y

yyy'/ '

i tng s dng

i tng s dng

iu khin

Hnh 2-1: Chuyn mch knh.Ty theo yu cu ca cc u vo m khi iu khin s i khin chuyn

mch iit lp knh dn vi u kia. Knh dn ny c duy tr cho n khi i tng s dng vn cn c nlu cu. Sau khi ht nhu cu th knh dn c gii phng.

51

Vic thit lp chuyn mch knh thng qua ba giai on sau:Thit lp knh dn: trc khi d liu c truyn i, mt knh dn im

ti im s c thit lp. u tin, tng i (node) pht hin yu cu ca di tng, xc nh ng truyn dn n i tng kia, nu ri, bo cho i tng kia bit v sau ni thng gia hai i tng.

Duy tr knh dn (truyn d liu): duy tr trong sut thi gian hai i tng trao i thng tin vi nhau, trong khong thi gian ny, tng i cn truyn cc tn hiu mang tnh bo hiu nh: gim st cuc ni v tnh cc lin lc.

Gii phng knh dn; knh dn c gii phng khi c yu cu ca mt trong hai i tng s dng, khi phc ii trng thi ban u.2.7.22 c im

Thc hin s trao i thng tin gira hai i tng bns; knh dn trn trc thi gian thc.

i tng s dng lm ch knh dn trong sut qu trnh trao i tin. iu ny lm gim hiu sut.

Yu cu chnh xc khng cao.Ni dung trao i khng cn a ch.c p dng trong thng tin thoi. Khi lu lng trong mng chuyn

mch knh tng ln n mt mc no th mt s cuc gi c th b kho(blocked), mng t chi mi s yu cu ni kt cho n khi ti trong mng lgim.2.1.3 Chuyn mch tin (Mcssagc Swithchiiig)2.L3.1 Khi nim

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Loi chuyn mch phc v s trao i gia cc bn tin (nh in tn, th in t, file ca my tnh...) gia cc i tng vi nhau c gi l chuyn mch tin.

Chuyn mch tin khng cn thit lp mt ng dn dnh ring gia ha trm u cui m mt bn tin c gi t ni pht ti ni thu c n nh mt l trnh trc bng a ch ni nhn m mi trung tm c th nhn dng chng. Ti mi trung tm chuyn mch (nodes chuyn mch), bn tin c tm lu vo b nh, x l ri truyn sang trung tm khc nu tuyn ny ri. Phng php ny gi l phng php tch ly trung gian - lu tr v chuyn tip hay stored and forward'. Kh nng lu li c th trong thi gian di do i x l hay trung tm tip theo cha sn sng nhn.

Thi gian tr gm: thi gian nhn bn tin, thi gian sp hng ch v thi gian x bn tin.V d: thu bao A mun gi mt bn tin n thu bao E, th a ch ca thu bao E 'c gn vo bn tin ca thu bao A v gi i n Node 4. Node 4 gi bn tin v tm nhnh tip theo (chng hn nhnh n Node 5) v bn tin c sp hng v ch truyn n ng ni 4-5. Khi ng ni ny l ri, bn tin c gi n Node 5 v c nh th, n c gi n 6 v n E. Nh vy, h thng chuyn mch tin l h thng lun gi v gi tip thng bo.2.L3.2 Dc client

Chuyn mch tin khng tn ti s thit lp v cung cp knh dn trc tip gia 2 trm u cui nn thi ean tr ln, Do , khng c s lin h heo thi gian thc.

i tng s dng khng lm ch knh dn trong sut qu trnh trao i thng tin.

Yu cu chnh xc cao.a ch ca thu bao c gn vo bn tin v bn tin c chuyn qua mng

t node ny qua node khc. Ti mi node, bn tin c nhn, tm gi v truyn sang node khc bi cc b m ca my tnh. Tc l ni dung c mang a ch.

Tc chuyn tin khng ph thuc vo i tng s dng. Hiu sut cao do knh dn c th dng chung cho nhiu i tng s dng khc nhau. T , dung lng tng cng ca knh dn yu cu khng cao, n ch yu ph thuc vo yu cu s dng ca-cc i tng.

53

c p dng cho truyn s liu, ch vit, hnh nh. Khi lu lng trong mng chuyn mch tin cao, n vn chp nhn cc yu cu ni kt mi nhng thi gian truyn dn c th di, tr ln. Mt h thng chuyn mch tin c th gi mt thng bo n nhiu ch khc nhau. iu ny chuyn mch knh khng thc hin c.2.1.4 Chuyn mch gi2.1.4.1 Khi nim

Chuyn mch gi li dng u im ca chuyn mch knh v chuyn mch gi, ng thi khc phc c nhc im ca hai loi chuyn mch ny.

Mng chuyn mch knh khng thch hp truyn s liu, bi v n c thit k phc v nhng yu cu tng i tha hn so vi tr s thi gian tng i ln (trung bnh 3 n 4 pht). i vi cc bn tin rt ngn th mng chuyn mch knh li cng khng thch hp v khng c hiu qu. Vi lu lng truyn s liu ch m thoi vi cc h s hot ng thp th cc chc nng chuyn mch knh khng cn ph hp na. Ch lm vic tt nht ca mng lc by gi l khi cc yu cu phc v c a ti theo tng gi nh, do ph hp vi mt mng chuyn mch tin ln hn l chuyn mch knh.

i vi chuyn mch tin th ton b ni dung ca bn tin u phi i qua cc trung tm chuyn mch vi kch thc bt k, nn trung tm chuyn mch ging nh mt im dng c chai, hu qu l tr phn hi v thng lng ca mng d dng b suy gim khi lng thng tin n qu ln. T , vic s dng ng dn l khng linh hot.

My thu d liu

Ngun tin

Hnh 2-3: Mng chuyn mch gi.

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Mng chuyn mch gi hot ng ging nh mng chuyn mch tin nhng trong , bn tin c ct ra thnh tng gi nh. Mi gi c gn cho mt tiu (header) cha a ch v cc thng tin iu khin khc. Cc gi c gi i trn mng theo nguyn tc tch ly trung gian ging nh chuyn mch tin. Ti trung tm nhn tin, cc gi c hp thnh mt bn tin v c sp xp li a ti thit b nhn s liu.

chng li, mng chuyn mch gi s dng phng thc t ng hi li, nn cc gi truyn t trung tm ny n trung tm khc tht s khng.c li. Qu trnh ny i hi cc trung tm khi nhn c cc gi th x l cc tn hiu kim tra li cha trong mi gi xc nh xem gi c li hay khng, nu li th n s pht yu cu pht li cho trung tm pht.2.1.4.2 Dc im

c im chnh ca mng chuyn mch gi chnh l phng php s dng kt hp tuyn truyn dn theo yu cu. Mi gi c truyn i ngay sau khi ng thng tin tng ng c ri. Nh vy, cc ng truyn dn c th phi hp s dng mt s ln cc ngun tng i t hot ng.

Mc s dng ca cc tuyn co hay thp ty thuc v khi lng b nh s dng v phc tp ca cc b iu khin ti cc trung tm.

tr trung bnh ca cc tuyn truyn dn ph thuc vo ti trong mng.Thi gian tr lin quan ti vic tch ly trung gian ca mng chuyn mch

gi rt nh so vi chuyn mch tin. Thng tin thoi c th c thit lp chnh xc cng ging nh thit b thit lp mt knh t thit b u cui ny n.thit b u cui khc.

Mng chuyn mch gi khng m bo cho vic lu tr thng tin ngoi tr cc trng hp ngu nhin xut hin vic nhn li cc gi t trung tm ny sang trung tm khc. N c thit k m bo vic kt ni qua tng i gia hai trung tm, trong , hai trung tm u tch cc tham gia vo qu trnh thit lp thng tin. Khng lu tr truyn nu u cui khng hot ng hay bn. 2 .U .3 u im tin cy cao

y l mt mng truyn tin rt tin cy c th chn ng bnh thng khc bna; n v gi c th gi thay th ngay c khi h thng chuyn mch

55

hay mng chuyn mch gi c li v c a ch ca i tc trong gi c truyn i.Cht lng cao

V chuyn mch gi hot ng theo ch truyn dn s biu hin bng 0 v 1, cht lng truyn dn ca n l tuyt ho. N cng c th thc hin truyn dn cht lng cao bng cch kim tra xem c li khng trong khi truyn dn gi gia cc h thng chuyn mch v gia thu bao vi mng.Kinh t

H thng chuyn mch gi dng cc ng truyn tin tc cao ni vi cc h thng chuyn mch nm trong mng nhm ghp knh cc gi ca cc thu bao khc nhau tng tnh kinh t v hiu qu truyn dn ca cc ng truyn dn.Cc dch v b sung

H thng chuyn mch gi c th cung cp nhng dch v b sung nh trao i thng bo, th in t v dch v khp kn khi cc gi c lu tr trong h thng chuyn mch. Hn na, mt dch v la chn nhanh chng a d liu vo cc gi yu cu cuc thoi ca thu bao ch gi, quay s tt v cc dch v thay th tip vin c th c thc hin.

2.2 CHUYN MCH KNH2.2.1 Phn loi

Ty thuc vo s pht trin ca lch s chuyn mch cng nh cch thc, tn hiu m ta c th phn loi nh sau (hnh 2-4):2.2.1.1 Chuyn mch phn chia khng gian (SDTS -Space Division Type Switch)

L loi chuyn mch c cc u ra, u vo c b tr theo khng gian (cch qung, thanh cho). Chuyn mch c thc hin bng cch m ng cc cng in t hay cc im tip xc. Chuyn mch ny c cc loi sau: Chuyn mch kiu chuyn ng truyn

Thc hin chuyn mch theo nguyn tc vn hnh c tng t nh chuyn mch xoay. N la chn dy ri trong qu trnh dn truyn v tin hnh cc chc nng iu khin mc nht nh.

Do n gin nn n c s dng rng ri trong tng i u tin.

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Hnh 2-4: Phn loi chuyn mch.Nhc im: Tc thc hin chm, tip xc mau mn, thay i hns mc tip xc gy nn s rung ng c hc. Chuyn mch c kiu ng m

n gin ho thao tc c hc thnh thao tc m ng. Chuyn mch ny khng c chuyn mch iu khin la chn v c thc hin theo gi thit l mch gi v mch iu khin l hon ton tch ring nhau. u im: Kh nng cung cp iu khin linh hot v c coi l chuyn mch tiu chun. Chuyn mch rle in t

C rle in t mi im ct ca chuyn mch thanh cho.im ct c th la chn theo hng ca dng in trong rle. Do thc

hin nhanh hn kiu m ng. Chuyn mch in t kiu phn chia khng gian

C mt cng in t mi im ct ca chuyn mch thanh cho.Nhc im: Khng tng thch vi phng php c do khc nhau v mc tn hiu hoc chi ph v cc c im thoi kh xu nh mt ting, xuyn m.2.2,1.2 Chuyn mch ghp (MPTS - Multiplexing Type Switch)

L loi chuyn mch m thng tin ca cc cuc gi c ghp vi nhau trn c s thi gian hay tn s trn ng truyn. Chuyn mch phn chia theo tn s (FDM)

Phng php phn chia theo tn s l tch cc tn hiu c cc tn s cn thit bng cch s dng b lc c th thay i. Phng php ny c cc vn

57

k thut nh pht sinh cc loi tn s khc nhau v trong vic cung cp ngt cc tn s ny cng nh trong cc b lc c th thay i. ng thi n li khng kinh t. Do phng php ny c nghin cu trong thi k u ca s pht trin tng i nhng cha c s dng rng ri. Chuyn mch phn chia theo thi gian (TDM)

Thc hin chuyn mach trn c s ghp knh theo thi gian, ta c th phn thnh cc loi:

- Chuyn mch PAM.- Chuyn mch PCM.Chuyn mch PAM c u im l n gin, khng cn phi bin i A/D,

nhng ch thch hp trong tng i nh hay va do tp m, xuyn m ln.Chuyn mch PCM c cht lng truyn dn hu nh khng l thuc

khong cch, tnh m v kinh k cao trong mng thng tin hin i, c kh nng lin kt vi IDN hay ISDN . Do ta xt chuyn mch PCM phn sau.2.2.2 Chuyn mch PCM

L loi chuyn mch ghp hot ng trn c s dn knh theo thi gian v iu ch xung m.

Trong h thng tng i, chng ta gp phi mt s thut ng v chuyn mch nh: chuyn mch, mng chuyn mch, trung tm chuyn mch, trng chuyn mch. trnh s ln ln, chng ta xt cc khi nim sau:- Chuyn mch: m t mt nguyn t chuyn mch n gin.- Trng chuyn mch: m t s hp thnh ca mt nhm cc chuyn mch. Trung tm chuyn mch (tng i) cha trng chuyn mch.

Mt mng chuyn mch gm cc trung tm (nodes) chuyn mch, cc thit b u cui v h thng truyn dn.

Mt trng chuyn mch s cung cp s ni kt gia cc knh trong cc lung PCM 32. Cc lung PCM n trng chuyn mch trn cc buses hay highways. Nh vy, chuyn mch s bao gm s truyn dn ca cc t PCM lin quan n mt knh trong mt khe thi gian mt bus ng vo v mt khe thi gian bus ng ra.

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dy ttng ai

Giao 1ng fifty tipn tt\ ng

bao dy

&;ng dy n thu bao

Hnh 2-5: Tricng chuyn mch.Vic trao i gia cc khe thi gian thc hin theo hai phne php v c

th tch bit hoc phi hp nh sau:- Chuyn mch thi gian.- Chuyn mch khng gian.

2.2.2.1 Chuyn mch ii gian (T)Chuyn mch T v c bn l thc hin chuyn i thng tin gia cc khe

thi gian khc nhau trn cng mt tuyn PCM.v mt l thuyt c th thc hin bng 2 phng php sau:

Phng php dng b trNguyn tc: Trn ng truyn tn hiu, ta t cc n v tr c thi gian tr bng 1 khe thi gian.

fv1b Mb

TSBlM b

TSB

TSA TSAQua R-11 b tr..->

Hnh 2-6: Phng php dng b tr.

59

Ay

A r q trnh Bnichnq IrinhMcutin Mc 1J tin Mc u bnKhi u tin Khilh2 Kthc li l hng ch

ca cc khi

Hnh 3-15: Hng ch chy.* Hng ch ca cc khi t do

Cc khi c s dng trong hng ch chy c ly t hng'ch ca cc khi t do. Hng ch ny u tin nm gi cc khi t do cn thit cho hng ch chy, hng ch ng h v cc hng ch khc trong h thng.

T READY

D0a ch khi u

tina ch khi th 2 aclikhith3 0

Khi FREE utin Khi FREE th 2 Kt thc m t hng ch ca cc khi

Hnh 3-16: Hng ch cc khi t do.

101

a ch ca khi u tin trong hng ch c lu tr trong mt t (a ch k hiu FREE). Khi mt chng trnh c bt u theo yu cu RUN, th mt khi c ly ra t hng ch ca cc khi FREE. Khi c ly ra ny s ci cc thng tin cn thit gm c mc u tin ca n, chng trnh c th chy c. Sau , khi ny c chn vo v tr tng ng trong hng ch chy, ph thuc vo mc u tin, mc u tin cng cao th khi cng c sp gn vi nh hng ch.

Lch trnh s lun chn chomg trnh c mc u tin cao nht thc hin. l chng trnh vi khi m t nm ti nh ca hng ch sn sng chy. Trc khi bt u chng trnh, lch trnh s thit lp mt yu cu v b ch th trng thi n cc gi tr c biu th trong khi m t. T , mt lnh nhy c thc hin, chuyn iu khin n a ch do b m a ra trong khi m t. Sau , chng trnh s thc hin cc lnh ca n, lnh ny tip lnh kia, cho n khi n t ti im m to ra mt yu cu a ti h thng iu hnh. Nu l yu cu ch th cc khi ca n s chuyn ra khi hng ng h. Nu l yu cu chy i vi chng trnh ny th mt khi mi c chn vo trong hng ch chy ti v tr thch hp trong hng v nu l yu cu kt thc th sau khi mi lnh c thc hin cc khi ca n trong hng ch chy c chuyn ra khi v c t vo hng ch cc khi t do, thng thng ti v tr nh ca hng ch t do, do vy, khng cn tm kim ton b hng ch ca khi cui cng. Ngt

Khi xut hin ngt, chng trnh ang chy s ng v vng iu khin ngt s lu gi ni dung ca cc thanh ghi... trong khi m t ti nh ca hng ch chy. Vng ngt c th to ra mt yu cu chy, to nn khi mi chn vo hng ch chy cng c th ti nh ca hng ch ny. Vng ngt s chuyn s kin iu khin ti lch trnh sau khi thc hin ngt mt cch thch hp. Lch trnh s chn chng trnh c mc u tin cao nht thc hin, tc l chong trnh c hot ha khi xut hin ngt.

Mt chng trnh c mc u tin cao hn c th ngt chng trnh c mc u tin thp hn, nhng khng c chiu ngc li. Cc chng trnh c cng mc u tin khng b ngt ln nhau v hot ng theo nguyn l FIFO.

102

Khi mi chng trnh khng hot ng, hng ch s rng. Trong trng hp ny, lch trnh s tin hnh vng ri, ti , n to cc o kim lp ti nh ca hng ch vi t READY. Ch c mt cch thot ra khi vng ri l thc hin ngt ng h thi gian thc hoc t thit b vo ra. Khi , mt khi m t t hng ch ng h hoc hng ch thit b vo ra s chuyn ra hng ch chy. Qun tr hot ng vo ra

Cc chng trnh h thng qun tr cc hot ng vo ra thng c gi l qun tr thit b vo ra. Chng l s la chn cc vng u ni h thng vi cc thit b ngoi vi. C mt b iu khin cho tng loi thit b ngoi vi trong cu hnh phn cng chuyn s liu gia thit b v b nh chnh.

Cc chc nng qun tr gm:- Phn nhim b nh v cc thit b ngoi vi hot ha cc qu trnh.- Bo v h thng t cc sai li phn cng v phn mm.- Qun tr thng tin ngi my.- Cung cp vic xm nhp n s liu m t trng thi ca h thng.

3.4.2.5 Cc chng trnh p dngCc chng trnh p dng c th phn thnh 3 loi chnh:

Cc chng trnh x l giCi' chng trnh x l gi c nhim v thit lp, gim st, gii phng v

tnh cc cho cuc gi ph hp vi cc t tnh ca dch v in thai. Cc chng trnh qun l

Thc hin chc nng gim st, o lng lu lng, o kim ng thu bao, trung k, thay i cc s liu bn c nh c lin quan n ng thu bao, trung k, xc nh cu hnh phn cng ca tng i, thay i s liu trong bng phin dch, bng to tuyn, lu gi cc s liu ca dch v nh dch v quay tt, chuyn gi... Cc chng trnh bo dng

Thc hin chc nng nhn bit li v v tr li bng bin php o kim phn cng ca tng i, bao gm c bn thn ca b x l. s.4.2.6 Cp nht phn mm hin hnh

Mc ch c bn ca mt tng i l thit lp v gii phng cc cuc gi in thai. Chc nng quan trng nht ca phn mm vn hnh l x l gi X

103

l gi bao gm nhn bit pha ch gi, x l tn hiu, tm ne gi qua mng chuyn mch, bin dch a ch v cc con s, tnh cc, gim st... v cui cng l gii phng cuc gi hon thnh.

Mc d x l gi chim phn chnh thi gian x l, nhng phn mm ch chim 15% trong tng th phn mm vn hnh.

Qun [ 25%

X l g 15% ' H thng

20% Bo dng DHthong X ty gi DQun y

Hnh 3-17: T l cc chng trnh trong tng i SPC.Cc chng trnh qun l v bo dng chim 2/3 ca tng th phn mm.

iu quan trng ca cc chc nng qun l v bo dng l kch c ca phn mm tng ng pht trin theo tng ngy, do , tng i cng ngy cng phc tp.3.4.3 Cc modul chnh ca phn mm

Nu phn theo modul , phn mm c th c phn nh sau:

3.4.3.1 Modue iu khn chinhModul chng trnh ny c vit cho khi iu khin chnh. N c np

vo b nh ROM trn khi ny. CPU m nhim vic cnh bo h thng, bo hiu, sa sai, qun l vic trao i thng tin v phi hp hot ng gia cc b x l, qun l thi gian khi lp h thng, qun l trng chuyn mch, giao tip ng dy, giao tip my tnh, iu khin cc cng vo ra, cc bus v cc b nh trong khi.3.4.3.2 Modiil giao tip ng dy

Modul ny c thit k cho b x l ng dy (LP) thc hin cc chc nng sau: qun l thu bao, qut s liu v trng thi ca thu bao, trung k. Tt c cc trng thi ca thu bao, trung k c lu tr trong b nh d liu RAM. Thc cht cc nh ca b nh RAM l bc tranh phn nh tnh trng

104

bn ri ca thu bao, trung k na vi nhne a ch tong ng. V d thu bao bn th nh s c gi tr 0 cn nu ri th c gi tr r . Vic qut nhn bit trn thi c qut theo chu k qut, nn cc s liu trong b nh RAM cng b thay i theo chu k. CPU thc hin vic thay i cc s liu ghi trong RAM bng lnh c ghi sn troriR ROM.

Ngoi ra trong modul cn c cc chng trnh thu nhn s quay t thu bao, phn tch v iu khin cc mch cht u ra cp cc tn hiu cho thu bao.3.4.3.3 Modul Hn lc ni b

Khi thu bao nhc my, tng i nhn bit c trng thi ny ca thu bao v pht m mi quay s. Sau , thu bao ch gi quay s ca thu bao b gi, tng i nhn bit s quay, phn tch ri iu khin chuyn mch ni ti thu bao b gi v cp tn hiu chung cho thu bao b gi, ng thi pht m hi m chung v thu bao ch gi.

Khi thu bao b gi nhc my, tn hiu chune v hi m chung s b ct, cuc m thoi bt u. Khi mt trong hai thu bao t my, thu bao kia s nhn c m bo bn t tng i.

trnh li c th xy ra v gim thi gian ch i, mt chong tnh con s m thi gian t khi nhc my n khi bt u quay s. Nu qu thi gian m thu bao khng quay s th thu bao cng s nhn c m bo bn v mi t my xung.

Khi thu bao b gi chung qu thi gian nh trc no , th tng i cng s t ng ct chung v gi m bo bn ti thu bao ch gi.3.4.3.4 Modul lin c ra ngoi

Khi thu bao mun gi ra ngoi phi quay s gi ra trung k. Nu trung k ri, thu bao s nghe m mi quay s t tng i bn ngoi bo cho thu bao bit ni thng c vi trung k bn ngoi. Tin trnh tip tc din ra gn ging nh cuc gi ni ht. Khi cuc gi kt thc, chng trnh tr li trng thi ban u.

Khi c cuc gi t bn ngoi vo, tng i xc nh xem thu bao ca n l bn hay ri m pht nhng tn hiu bo hiu thch hp cho tng i pha thu bao ch gi bit, tin trnh tip sau ging nh cuc gi ni ht.

105

Ngoi ra, c chng trhh phc v kim tra ng dy trung k ca in thoi vin, trung k nghip v... in thoi vin, hoc k thut vin c th c kh nng nghe xen khi mun kim tra 1 ng dy no .3.4.3.5 Modui nhn bit v x l li

Hat ng da trn cu trc ca chng trnh nh gi, x l li, t sa cha v t phc hi.3.4.3.6 Modul giao 'tip my tnh

m nhn nhim v m phng li chc nng x l cuc gi ca tng i.

106

Chng 4 K THUT BO H IU

4.1 TNG QUAN

4.1. Khi nimMt mng vin thng c nhim v ch yu l thit lp, gii ta v duy tr

knh gia thu bao vi node chuyn mch hay gia cc node chuyn mch vi nhau.' thc hin c iu ny, cn phi c mt h thng thng tin h tr c trao i gia h thng chuyn mch vi cc thit b u cui v gia cc h thng chuyn mch vi nhau, h thng thng tin ny gi l h thng bo hiu. Thng tin bo hiu c th c nhiu dns khc nhau thun tin cho vic iu khin cc thao tc chuyn mch, x gi...

Thc cht, mt s trao i tin gia ngi s dng v cc thit b trong mng cn phi c mt s t chc chng c th lin lc vi nhau mt cch an ton. Cho nn, thng tin bo hiu c trc, trong v sau mt cuc gi. tng hiu sut lm vic, thi gian lm vic ca h thng bo hiu cng nh cng tt, n ph thuc vo cc thit b hin i trong mng.

4.1.2 Cc chc nng bo hiuTa c th nu cc chc nng bo hiu tng qut nh sau:

4.1.2.1 Chc nng gim stChc nng gim st c s dng nhn bit v phn nh s thay i v

trng thi hoc v iu kin ca mt s phn t (ng dy thu bao, trung k..4.1.2.2 Chc nng tm chn

Chc nng ny lin quan n vic thit lp cuc gi v c khi u bng thu bao ch gi gi thng tin a ch ca thu bao b gi. Cc thng tin a ch ny cng vi cc thng tin ca chc nng tm chn c truyn gia cc tng i p ng qu trnh chuyn mch.

Chc nng ny phi c tnh hiu qu, tin cy cao m bo vic thc hin chnh xc cc chc nng chuyn mch.4.1.2.3 Chc nng vn hnh

Nhn bit v chuyn thng tin v trng thi tc nghn trong mng, thng thng l trng thi ng cho thu bao ch gi.

107

Thng bo v cc thit b, cc trung k khng bnh thns hoc ang trng thi bo dng.

Cung cp cc thng tin tnh cc.Cung cp cc phng tin nh gi, ng chnh, cnh bo t tng i

khc.

4.1.3 c im cc h thng bo hiu o Mt h thng bo hiu c c im chung nh sau:- C tnh quc t.- Ph hp vi cc thit b m n phc v.- Kh nng phi hp vi cc h thng bo hiu khc.

4.1.4 H thng thng tin bo hiuH thng thng tin bo hiu cng l mt h thng thng tin in, n cng

gm;- Ngun tt c cc tn hiu cn thit cho vic thit lp cuc gi v cung cp

cc dch v khc.- Cng vic truyn dn chuyn tn hiu t ngun ti ch.0

Ni ungTn

K^h dn Xl ....... ..J X 1 >1 1 I '

hiu-------------------------------Phng php boTn t- iuthu

Ni dung

Hnh 4-1: H thng bo hiu.

4.1.5 K thut bo hiuNh vy, k thut bo hiu nghin cu v;-N i dung bo hiu.-Phng php truyn bo hiu.-K thut x l bo hiu.

4.2 NI DNG CA BO HIU

4.2.1 Phn tch cuc giTrong mng in in thoi, khi mt thu bao mun ni vi mt thu bao

khc bt k trong mng th bo hiu s thng bo cho mng chuyn mch bit

108

rng thu bao yu cu phc v, v sau trao cho chuyn mch ni ht cc s liu cn thit nhn bit thu bao xa cn n v t nh tuyn cuc gi mt cch chnh xc. Bo hiu cn gim st cuc gi v trao cho thu bao cc thng tin trng thi nh mi quay s, m bo bn, hi m chung... Phn loi

C th phn loi bo hiu theo cc cch nh sau:

Hook of'

PABX

0 - (s)PABX

Diailna

se zure Seizure acKnov/ledgement)

.Dkliiiifl-... .

Accress info.Address infc. ssizure ,

Se zure ac-knowleccement

Address info.

B

Ring b.tone R ng signal

B answer B answer

Conversation

Hook onm

-, disconnector!Clear tor.yarc Clear back 3

Hcok on

Hnh 4-2: Phn tch mt cuc gi thnh cng thng thng. Phn theo chc nng:

- Bo hiu nghe - nhn (thng bo),- Bo hiu trng thi (gim st).- Bo hiu a ch (chn s).

Phn theo tng quan;- Bo hiu gia tng i vi thu bao.- Bo hiu gia tng i vi tng i.

109

4.2.2 Phn theo chc nng4.2.2.1 Bo hiu nghe - nhn

L loi bo hiu nghe thy c i vi thu bao trong tin trnh cuc gi. l cc loi thng tin ch yu t tng i n thu bao nh sau; m mi quay s

Khi thu bao nhc t hp, tr khng ng dy gim xung t ngt. Dn n dng in trn dy tng ln. iu ny c tng i nhn bit thu bao yu cu thit lp cuc gi v n pht cho thu bao m mi quay s vi tn s khong 425 Hz lin tc. m bo bn hoc thng bo

Trng hp 1 thu bao bn, hay sau khi kt thc cuc gi, thu bao ny t my, tng i pht m bo bn cho th bao kia vi tn s 425 Hz, t l 1:1.

m bo bn cn c gi cho thu bao ch gi khi thu bao ny sau mt khong thi gian sau khi nhn c m mi quay s m vn cha quay s.

Trng hp thu bao b gi i vng hoc c cc dch v c bit ca n th tng i thng bo cho thu bao ch gi cc bn tin tng ng. Dng chung

Dng chung c pht cho thu bao b gi khi thu bao ny ri vi tn hiu xoay chiu khong 75 VAC, 25 Hz. Hi m chung

Hi m chung c pht cho thu bao ch gi qua tuyn thoi t tng i khi ang chung cho thu bao b gi. Tn hiu hi m chung c tn s 425 Hz, t l 1:3. Cc bn tin thng bo khc

Nu trong tng i c cc bn tin c bit c ghi sn v cc l do cuc gi khng thnh nh tnh trng tuyn, hng hc... th tng i pht cho thu bao ch gi cc bn tin tng ng. Trng hp ny l do cuc gi khng thnh khng phi bi cc l do ca thu bao b gi. Tn hiu gi phc hi v gi my qu lu

Tn hiu ny truyn ti thu bao ch gi khi thu bao b gi t my v tng i gi tn m bo bn m thu bao ch gi khng ngh n vic gii ta tuyn gi. Sau mt khong thi gian tr th tuyn mi c thc s gii ta.

110

Tn hiu ny cng c pht khi thu bao duy tr trng thi chn s qu lu. Tn hiu ny thng l sau m bo bn.4.2.2.2 Bo hiu trng thi (bo hiu gim si)

Xc nh trng thi ng dy ca thu bao v cuc gi. Trng thi nhc t hp

Xut hin khi thu bao nhc t hp hoc tn hiu chim, dng t mt ng trung k gi vo; n biu th yu cu thit lp cuc gi mi. Sau khi thu c tn hiu ny, tng i s u ni vi mt thit b thch hp thu thng tin a ch t thu bao ch gi hoc t ng trung k. Trng thi t to hp

Xut hin khi thu bao t t hp hoc tn hiu yu cu gii ta t ng trung k a ti. Thng tin ny ch rng cuc gi kt thc, yu cu gii ta tuyn gi. Khi nhn c thng tin ny, tng i gii phng tt c cc thit b dng u ni cuc gi ny v xa cc thng tin dng thit lp v duy tr cuc gi, ng thi thit lp thng tin tnh cc. Trng thi ri - bn

Da vo tnh trng t hp ca thu bao b gi hoc ng trung k l ri hay bn hoc tuyn tng i pht thng tin v trne thi ca thu bao b gi hoc ng truyn cho thu bao ch gi. Tinh trng hng hc

Bng cc php th tng i xc nh trnh trng ca ng dy c th thng bo cho thu bao hoc cho b phn iu hnh v bo dng. Tn hiu tr li v

Khi chung, ngay sau khi thu bao b gi nhc my, mt tn hiu dng o ngun c truyn theo ng dy ti thu'bao ch gi. Tn hiu ny dng thao tc mt thit b t thu bao ch gi nh b tnh cc hoc i vi thu bao dng th.4.2.23 Bo hiu a ch

Thng tin a ch gm mt phn hoc ton b a ch ca thu bao b gi, i khi cn km theo cc s liu khc.

Sau khi nhn c m mi quay s, thu bao tin hnh pht cc ch s a ch ca thu bao b gi. Cc ch s ny c th c pht di dng thp phn hay dng m a tn.

111

Tn hiu xung thp phnCc ch s a ch c pht di dng chui ca s gin on mch vng

mt chiu (DC) nh a quay s hoc h thng phm thp phn.r.A f

40mAS.Sr-ii 33.3-m:;

_ r

Hook Quay ms

Hnh 4-3: Quay s bng xung thp phn (So 42...).S lng cc ln gin on ch th ch s da ch tr s 0 n g vi 10 ln

gin on. Tc gin on l 10 ln mi giy v t s xung l 1:2.C mt khong thi gian gia cc s lin tip khong vi trm ms trc ch

s k tip tng i phn bit cc ch s vi nhau.Ch : Phng php pht cc ch s thp phn ny khng th pht khi ang

hi thoi. Tn hiu m a tn ghp cp (DTMF)

679Hz

770Hz

852Hz

941Hz

A

B

D

1G29HZ 133GHz 1477Hz 1533Hz

Hnh 4-4: Quay s bng m a tn.Phng php ny khc phc c nhc im ca phng php trn. N s

dng 2 trong 6 tn s m tn chuyn cc ch s a ch. Khi n mt phm, ta nhn c mt tn hiu bao gm s kt hp ca hai tn s: mt nhm ny v mt nhm kia gi l a tn ghp cp (Dual Tone Multifrequency: DTMF).

Cc tn s c chn sao cho s phng to tn hiu l b nht.

112

Tn hiu truyn i di hay ngn ph thuc v thi gian n phm. Thi gian ny chnh l thi gian ko di ca tn hiu.

Phng php ny c u im l:- Thi gian quay s nhanh hn.- C th quay s trong khi m thoi (s dng cho in thoi hi ngh).

4.2.3 Phn theo tng quan4.2.3.1 Bo hiu gia tng i vi thu bao

Tn hiu ng dy thu bao gi- Tn hiu a ch.- Tn hiu bo bn.- Tn hiu bo ri.- Hi m chung.- Tn hiu tr li v.- Tn hiu gi my qu lu. Tn hiu ng dy thu bao b gi -T n hiu chung.-T n hiu tr li.-T n hiu phc hi. Tn hiu ng dy thu bao th 3Ging nh tn hiu ng dy thu bao b gi. c s dng cho in thoi

hi ngh. N lm gin on thu bao ch gi trong mt khong thi gian nh hn tn hiu gii ta gi khong 200ms n 320ms.4.2.3.2 Bo hiu lin tng i

C th c truyn dn tn hiu bo hiu theo ng dy bo hiu ring hoc i chung vi ng dy thai. Chng s dng tn s trong bng tn ting ni (trong bng) hoc ngoi di tn ting ni (ngoi bng). Thng s dng hai k thut truyn sau;

-B o hiu knh kt hp (CAS).-B o hu knh chung (CCS),Dng ca tn hiu:- Dng xung: tn hiu c truyn i di dng xung, v d nh tn hiu a

ch.

113

-Dng lin tc: truyn lin tc v mt thi gian nhng thay i v trng thi c trng nh tn s ...

-Dng p ch: tng t nh truyn xung nhng khong truyn dn khng n nh trc m ko di cho n khi c s xc nhn ca pha thu qua mt thit b xc nhn truyn v.

4.3 PHNG PHP TRUYN DN BO HIUC nhiu cch phn loi phng php truyn bo hiu, nhng y, ta

phn thnh hai loi sau;- Bo hiu knh kt hp (CAS - Chanel Associated Signalling).- Bo hiu knh chung (CCS - Common Chanel Signalling).

Bo hiu

Bo hiu tng i - thu bao Bo hiu in tng i

.........CAS C C S ___

Hnh 4-5: Phng php truyn bo hiu.

4.3.1 Bo hiu knh kt hp (CAS - Chanel Associated Signalling)

hiu

Hnh 4-6: Bo hiu knh kt hp.Bo hiu knh kt hp l loi bo hiu m trong , cc ng bo hiu

c n nh trn mi knh thng tin v cc tn hiu ny c th c truyn theo nhiu cch khc nhau.4,3.L1 Phn loi

C hai loi thng tin bo hiu trong bo hiu knh kt hp l;- Bo hiu ng dy.

114

- Bo hiu thanh ghi (a ch). Bo hiu ng dyBo hiu ng dy l phng php bo hiu c truyn dn gia cc

thit b kt cui v thng xuyn kim tra ng truyn hoc tt c cc mch kt cui, v d cc trng thi bn, ri...

Bo hiu thanh ghiBo hiu thanh ghi l s truyn tt c cc thng tin c lin quan n tuyn

ni cuc gi bao gm cc con s thu bao b gi, nhng c tnh ca thu bao .43.1.2 Phng php truyn

im ni im (end-to-end)Theo phng php bo hiu ny, thng tin lun c truyn i gia cc u

cui ca tuyn ni theo tin trin ca n. V d khi thit lp tuyn ni qua ba tng i A-B-C, thng tin bo hiu u tin c truyn t A ti B v sau khi qung ni B-C c thit lp th bo hiu li c truyn t A ti c .

ng tip ng (lnk-to-lnk)Tn hiu lun c truyn i v tm lu tng qung ca tuyn ni. u tin

thng tin bo hiu c truyn i t A n B v sau khi qung ni t B n c c thit lp th thng tin bo hiu tip tc truyn i t B n c .

Ni chung, thng tin bo hiu gim st v cc kiu thu bao c truyn dn theo phng thc ng tip ng cn thng tin a ch th c truyn i theo phng php im ni im hoc ng tip ng ty thuc v cu trc mng.4.3.1.3 Cc k thu truyn cc tn lu bo hiu trong CAS

Mt cch chnh xc, bo hiu knh kt hp phi l mt s kt hp vnh vin vi knh mang cuc gi tht s. T , ta c cc dng khc nhau ca tn hiu bo hiu :

- Tn hiu bo hiu nm trong knh thoi (DC, trong bng).- Tn hiu bo hiu nm trong knh thoi nhng phm vi tn s khc (ngoi

bng).- Tn hiu bo hiu trong mt khe thi gian, m trong , cc knh thoi

c phn chia mt cch c nh theo chu k (bo hiu PCM trong TS16).Bo hiu knh kt hp c th s dng gia cc loi tng i khc nhau.

Nh vy, k thut truyn bo hiu ny gm cc tn hiu bo hiu:

115

- Bo hiu DC.- Bo hiu AC.- Bo hiu PCM. Cc tn hiu bo hiu c bnCc tn hiu bo hiu gia tng i vi tng i bao gm mt s tn hiu c

bn sau cho mt cuc gi hon thnh:- Tn hiu chim dng (Seizure); Yu cu chim dng mt ng vo tng

i B (1 knh thoi) v cc thit b nhn thng tin a ch.- Tn hiu xc nhn chim dng (Seizure aknowledgement): Thng bo cho

tng i A bit rng tng i B nhn c tn hiu chim dng t A.- Thng tin a ch (Address Information); So a ch ca thu bao B.- Tn hiu tr li (B answer): Tng i B bo cho tng i A bit thu bao

B nhc my.- Xa v (Clear back): Tng i B bo cho tng i A bit B gc my.- Xa i (Clear forward); Tng i B nhn thng bo cuc gi kt thc,

gii ta thit-b v ng dy.Ex A Ex B

a - - - - - - o - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (...)- - - - - - sSeizure

Seizure ackno'Aiedgement

Address Information

B ans>.ver

Conversation

Clear back

Clear forv/ard

Hnh 4-7: Cc tn hi bo hiu c bn ca mt cuc gi thnh cng. Bo hiu DCTn hiu ny c truyn dng xung nh thay i cc tnh hoc tr khng

116

ca dy dn. Thng thng, h thng lm vic vi ba trng thi hng ti v vi hai trng thi hng v.

Cc trng thi c s dng hng ti l;- Tr khng ng dy thp.- Tr khng ng dy cao.- Cc tnh tch cc. Cc trng thi c s dng hng v l:- Cc tnh bnh thng.- Cc tnh o.Bo hiu DC c th c dng trn i dy vt l. Do thit b DC r tin,

nn h thng ny c s dng rng ri.

SsidiiQ Exchanqe Line ReceivmqExeharKi

Sending of: Reception of: Recepfonof:Seizure S