2. GHP KNH SDH

2.1. Cc tiu chun ghp knh SDH

2.1.1. Cc khuyn ngh ca ITU-T v SDH

G.707 Cc tc bit SDH G.708 Giao din nt mng SDH G.709 Cu trc ghp ng b

G.773 Cc b giao thc ca giao din Q G.774 M hnh thng tin qun l SDH

G.782 Cc kiu v cc c tnh chung ca thit b ghp SDH G.783 Cc c tnh ca cc khi chc nng thit b ghp SDH G.784 Qun l SDH

G.803 Cu trc mng truyn dn da vo SDH G.825- iu khin rung pha v tri pha trong mng thng tin SDH

G.957 Cc giao din quang ca thit b v h thng lin quan n SDH G.958 Cc h thng s SDH s dng cho cp si quang

2.1.2. Tc bit ca SDH

Mng SDH l mng ng b, trong mi phn t mng s dng tn hiu ng b c cung cp t mt ngun ng h chun quc gia. Theo khuyn ngh G.707/Y.1322 th tc bit phn cp SDH c 6 mc. Mc 0 c tc bit l 51, 84 Mbit/s. Mc 1 c tc bit l 155,52 Mbit/s. Tc bit cc mc cao l bi s nguyn ca tc bit mc 1. Su mc tc bit bao gm:

STM-0 = 51,840 Mbit/s

STM-1 = 155,520 Mbit/s

STM- 4 = 622,08 Mbit/s

STM- 16 = 2048,32 Mbit/s

STM- 64 = 9953,28 Mbit/s

STM- 256 = 39813,120 Mbit/s

Cc lung nhnh PDH u vo thit b ghp SDH c ITU-T chp nhn gm c:

Theo tiu chun chu u: 2,048 Mbit/s; 8,448 Mbit/s; 34,368 Mbit/s v 139,264 Mbit/s.

Theo tiu chun Bc M: 1,544 Mbit/s; 6,312 Mbit/s v 44,376 Mbit/s.

2.1.3. Quy nh v conten o (VC)

Tn hiu lung nhnh PDH a n thit b ghp SDH trong khong thi gian 125 s c cha trong mt hp c dung lng nht nh v gn nhn ch r trong hp cha loi tn hiu lung nhnh no, hp nh vy gi l conten o. C hai loi conten o: conten o mc thp VC-11, VC-12, VC-2 v conten o mc cao VC-3, VC-4. Ngoi cc conten o, khuyn ngh G.707/Y.1322 cn quy nh cc loi conten o kt chui nh: VC-4-4c, VC-4-16c, VC-4-64c v VC-4-256c. Tc bit tng v tc bit ti trng ca cc conten o n v kt chui c lit k nh bng 2.1.3

Bng 2.1.3 - Dung lng cc VC-n

Loi VC-nTc bit tng (kbit/s)Tc bit ca ti trng (kbit/s)

VC-1116641600

VC-1222402176

VC-268486784

VC-34896048384

VC-4150336149760

VC-4-4c601344599040

VC-4-16c24053762396160

VC-4-64c96215049584640

VC-4-256c3848601638338560

2.1.4. Quy nh v ng, tuyn v on

Khi tm hiu thit b cng nh cu trc v hot ng ca mng SDH c lin quan n khi nim v ng, tuyn v on nh biu th trn hnh 2.15, v vy trong mc ny trnh by cc quy nh .

(1) on (section)

C hai loi on, l on ghp v on lp. on ghp l mi trng truyn dn gia hai trm ghp knh k tip nhau, trong mt trm to ra tn hiu STM-N v trm kia kt cui tn hiu STM-N ny. on lp l b phn truyn dn gia hai trm lp k tip nhau, hoc gia trm lp v trm ghp knh k tip.

(2) Tuyn (Path)

Tuyn l b phn truyn dn c tnh t im nhp vo mt tn hiu c hnh thnh bi conten o (VC) n im tch ra chnh tn hiu y. C hai loi tuyn, l tuyn mc thp lin quan n tn hiu VC-11, VC-12, VC-2 v tuyn mc cao lin quan n tn hiu VC-3 v VC-4.

(3) ng (Line) l tp hp ca tt c cc tuyn ca h thng truyn dn thng sut tn hiu STM-N.

Hnh 2.1.4- M hnh xc nh ng, on v tuyn.2.2. S khi ghp cc lung PDH vo khung SDH-N2.2.1. S khi b ghp knh SDHS khi b ghp knh SDH nh hnh 2.16.

Hnh 2.2.1- S khi thit b ghp knh SDH

2.2.2. Chc nng cc khi

u vo b ghp l cc lung nhnh PDH ca chu u v Bc M. Cc khi ca thit b ghp c phn thnh cc nhm C-n, VC-n, TU-n, TUG-n, AU-n, AUG v STM-N. Chc nng ca cc khi trong cc nhm ny l:

(1) C-n: conten mc n (n = 1, 2, 3, 4).

Mc 1 ca Bc M k hiu C-11 v ca chu u k hiu C-12. Cc mc cn li c mt ch s. C-n c chc nng sp xp lung nhnh PDH tng ng, n thm cc byte khng mang tin cho s byte nh mc ca khung chun C-n.

(2) VC-n: conten o mc n.

VC-n c chc nng sp xp tn hiu C-n, chn thm bit chuyn lung vo cn ng b thnh lung ra ng b, b sung cc byte mo u tuyn (VC-n POH).(3) TU-n: con tr khi nhnh mc n (n = 11, 12 v 3).

Con tr khi nhnh c chc nng ng chnh tc bit v tc khung tn hiu ghp VC-n mc thp cho ph hp vi tc bit cng nh tc khung ca tn hiu VC-n mc cao hn.

(4) TUG-n: nhm khi nhnh mc n (n = 2, 3)

Nhm khi nhnh ghp xen byte cc tn hiu TU-n mc thp thnh khung chun TUG-2 hoc ghp cc tn hiu TUG-2 thnh khung chun TUG-3. Cng c th sp xp tn hiu TU-3 thnh khung TUG-3.

(5) AU-n: con tr khi qun l mc n (n = 3, 4).

Con tr khi qun l ng chnh tc bit v tc khung ca tn hiu ghp VC-3 hoc VC-4 cho ph hp vi tc bit v tc khung ca tn hiu AUG.

(6) STM-N: mun truyn dn ng b mc N (N = 1, 4, 16, 64 v 256).

STM-N ghp xen byte N tn hiu AUG, mo u on v con tr khi qun l AU-n thnh khung STM-N.

2.3. Qu trnh ghp cc lung nhnh PDH vo khung STM-1

Trong SDH, khung ca tt c cc mc ghp u c 9 hng v thi hn l 125 s, s ct nhiu hay t l ph thuc vo dung lng byte trong khung nhiu hay t.

Khung STM-1 c cu trc nh hnh 2.17.

Hnh 2.3- Cu trc khung STM-1

Khung STM-1 c 9 hng 270 ct. Khi nim ct ng nht vi khi nim byte (8 bit). Khung bao gm 4 phn: mo u on lp (RSOH) chim 3 hng v 9 ct, mo u on ghp (MSOH) chim 5 hng v 9 ct. Con tr AU-4, k hiu l AU-4 PTR ghp vo hng 4, ct 1 n ct 9. Phn ti trng dnh ghp tn hiu VC-4 c 261 ct v 9 hng.

Tng s byte trong khung STM-1 = 270 byte 9 = 2430 byte.

Tc bit truyn ca khung STM-1: STM-1 = 8 bit / byte 2430 byte /khung 8.103 khung/s = 155,52 Mbit/s. y chnh l tc bit mc 1 ca SDH.

Trong mc ny ch trnh by ghp cc lung nhnh PDH ca chu u vo khung STM-1. Mun to thnh khung STM-1 c th p dng mt s phng php sau y:(1) Ghp mt lung nhnh 139,264 Mbit/s;

(2) Ghp 3 lung nhnh 34,368 Mbit/s;

(3) Ghp 63 lung nhnh 2,048 Mbit/s;

(4) Ghp 1 lung nhnh 34,368 Mbit/s v 42 lung nhnh 2,048 Mbit/s;

(5) Ghp 2 lung nhnh 34,368 Mbit/s v 21 lung nhnh 2,048 Mbit/s.

2.3.1. Sp xp cc lung nhnh 139,264 Mbit/s vo khung STM-1

(1) Sp xp lung nhnh 139,264 Mbit/s vo khung VC-4

Trc ht khi C-4 chuyn i m ba mc ca lung nhnh thnh m hai mc v chuyn giao cho khi VC-4. c th bin lung nhnh cn ng b thnh lung ng b theo ng h ca thit b SDH, khi VC-4 cn tin hnh chn m. Ct th nht ca khung VC-4 ghp 9 byte VC-POH, cn li 260 ct c chia thnh 20 khi, mi khi 13 byte nh biu th trn hnh 2.18.

Mi hng ca khung VC-4 c 260 byte nh hnh 2.18b, ghp cc loi bit nh sau:

130 bit n khng mang tin (R); 10 bit mo u (O); 5 bit iu khin chn (C); 1 bit chn S; v (241 byte + 6 bit) tin I.

S lng byte I m lung nhnh 139,264 Mbit/s cung cp cho khung VC-4 trong thi hn 125 s c xc nh nh sau:

BE4 = 139264.103 bit : 8 bit : 8.103 = 2176 byte (2.3)S byte tin I sp xp c nh trong khung VC-4 l:

B0 = (241 byte + 6 bit) 9 = 2169 byte + 6 byte + 6 bit = 2175 byte + 6 bit. (2.4)

So snh cc biu thc (2.3) v (2.4) thy rng lung nhnh E4 cung cp cho khung VC-4 nhiu hn 2 bit I so vi s lng bit I ghp c nh trong khung ny.V vy phi tin hnh chn bit v y l chn m. 2 bit chn m ny c chn vo 2 hng ca khung VC-4. Hng no cn chn th lnh iu khin chn m c ci t trong 5 bit iu khin CCCCC = 11111 v bit chn S ca ca dng trong khung sau l bit tin I. Dng no khng chn th c lnh iu khin

DC = 00000 v bit S l bit n khng mang tin.

(2) Ghp khung VC-4 vo khung STM-1

Sau khi sp xp khung VC-4 th khung ny c ghp vo phn ti trng ca khung STM-1 nh hnh 2.3.1a. Khi STM-1 ghp thm cc byte mo u SOH v cc byte con tr AU-4 hnh thnh khung STM-1 hon chnh.

Hnh 2.3.1- Sp xp lung nhnh 139,264 Mbit/s vo VC-4

2.3.2. Sp xp lung nhnh 34,368 Mbit/s vo khung STM-1

(1) Sp xp lung nhnh 34,368 Mbit/s vo khung VC-3 Qu trnh sp xp c th hin ti hnh 2.3.2.1. Trc ht mi khi C-3 chuyn i tn hiu xung ba mc 34,368 Mbit/s thnh hai mc v chuyn giao cho khi VC-3. Khi VC-3 chuyn lung nhnh cn ng b 34,368 Mbit/s thnh lung ng b bng cch s dng chn dng v chn m. Khung VC-3 c 85 ct 9 hng, trong ct u tin l VC-3 POH c cu trc nh VC-4 POH. Chia khung VC-3 thnh 3 phn khung T1, T2 v T3, mi phn khung chim 3 hng nh hnh 2.3.2.1a v c c th ho nh hnh 2.3.2.1b.

Trong mi phn khung c:

(71 byte + 5 bit) n c nh R; 5 bit C1 v 5 bit C2; mt bit S1 v mt bit S2; (178 byte + 7 bit) tin I.

S byte khi tc lung nhnh E3 t nh mc 34,368 Mbit/s cung cp cho mt phn khung l:

BE3 = 34368.103 bit : 8 : 8.103 /3 = 179 byte.(2.5)

Trong thi gian tc lung nhnh E3 t nh mc th S1 l bit n, S2 l bit I v C1C1C1C1C1= 00000, C2C2C2C2C2 = 00000.

Hnh 2.3.2.1- Sp xp lung nhnh 34,368 Mbit/s vo khung VC-3

- Chn m

Khi tc lung nhnh tng 30 ppm th s bit tng thm trong mi phn khung l: bTng = 34368. 103 bit 30. 10-6 / 8. 103/3 = 0,4 bitC ngha l c sau 5 phn khung tng thm 2 bit I. Khi c lnh C1C1C1C1C1 = 11111 chuyn bit chn m S1 ca hai phn khung sau t bit n thnh bit I v C2C2C2C2C2 = 00000 cc bit S2 gi nguyn trng thi bit I.

- Chn dng

Chn dng xy ra trong trng hp tc bit ca lung nhnh gim 30 ppm, ngha l trong mi phn khung gim 0,4 bit v sau 5 phn khung gim 2 bit. Khi c ch th chn C1C1C1C1C1= 00000 cc bit S1 trong hai phn khung sau gi nguyn trng thi l cc bit n, cn C2C2C2C2C2 = 11111 chuyn cc bit I ti bit chn dng S2 ca 2 phn khung sau thnh cc bit n.

(2) Ghp 3 khung TU-3 vo VC-4

Trnh t ghp 3 khung TUG-3 vo khung VC-4 nh hnh 2.3.2.2.

Khung TUG-3 c 86 ct v 3 TUG-3 c 258 ct. Trong khi , khung VC-4 c 261 ct. V vy phi n 18 byte c nh vo ct th hai v th 3 ca khung VC-4. T ct th 4 n ct th 261 dnh ghp 3 khung TUG-3. Qu trnh ghp xen byte t cc byte trong cng mt khung TUG-3 vo mt ct ca khung VC-4. Do to thnh cc ct A, B, C.

Hnh 2.3.2.2- Ghp 3 khung TUG-3 vo khung VC-4

(3) Ghp 3 VC-3 vo khung STM-1

Trnh t ghp 3 khung VC-3 vo khung STM-1 nh hnh 2.3.2.3.

Hnh 2.3.2.3- Ghp 3 VC-3 vo khung STM-1

Khung C-3 c 84 ct 9 hng. VC-3 bao gm C-3 v VC-3 POH, v vy khung VC-3 c 85 ct 9 hng. Khi TU-3 ghp cc byte H1 H2 H3 ca TU-3 PTR vo u ct th nht ca khung TU-3.

Khi TUG-3 n 6 byte S to thnh khung TUG-3 c 86 ct 9 hng. Ba khung TUG-3 ghp vo khung VC-4. V 3 khung TUG-3 ch c 258 ct, nn khi VC-4 n thm 18 byte S vo ct th hai v th ba, ghp 9 byte VC-4 POH to thnh khung VC-4 c 261 ct 9 dng. Khung AU-4 v AUG ging nhau, gm khung VC-4 v 9 byte AU-4 PTR. Cui cng, khung AUG ghp vo khung STM-1.

2.3.3. Sp xp 63 lung nhnh 2,048 Mbit/s vo khung STM-1

(1) Sp xp a khung VC-12 v a khung TU-12

Trong thi hn 125 s lung nhnh E1 cung cp cho khi C-12 34 byte. Mi khung C-12 s dng mt s byte mo u nh khung VC-n bc cao l khng cn thit. V vy cn phi ghp 4 khung C-12 v b sung thm mt s byte mo u vo u cc khung C-12 to thnh a khung VC-12. VC-12 POH c 4 byte (V5, J2, N2 v K4). Cu trc a khung VC-12 nh hnh 2.22a. Khi TU-12 b sung vo u khung th nht, th hai, th ba, th t ca a khung VC-12 mt byte con tr (V1, V2, V3) v V4 l byte d tr to thnh a khung TU-12 c 4 khung nh hnh

Hnh 2.3.3.1- Cu trc a khung VC-12 v TU-12

(2) Ghp 63 lung nhnh 2,048 Mbit/s vo khung VC-4

Qu trnh ghp 63 lung nhnh 2,048 Mbit/s vo khung VC-4 c minh ho bi qu trnh ghp 63 khung TU-12 vo khung VC-4 nh hnh 2.23.

Chuyn khung TU-12 mt ct, 36 byte thnh khung TU-12 c 4 ct 9 hng. Ba khung TU-12 ghp xen byte thnh khung TUG-2 c 12 ct 9 hng, trong khung ny c 3 byte V. Ghp 7 khung TUG-2 thnh khung TUG-3 c 86 ct 9 hng. Trong khung TUG-3 c 21 byte V.Tuy nhin, 7 khung TUG-2 ch c 84 ct, v vy khi TUG-3 ghp 3 byte NPI v 6 byte n S vo ct th nht ca khung TUG-3. Tip theo ghp 9 byte n S vo ct th hai. T ct th ba n ct 86 dnh ghp 7 khung TUG-2. NPI l 3 byte con tr khng c hiu lc. y l cc byte c cu trc c nh v mang du hiu ring pha thu phn bit trng hp ny vi trng hp khung TUG-3 c 3 byte TU-3 PTR khi ghp 3 VC-3 vo khung VC-4.

Hnh 2.3.3.2- Ghp 63 lung nhnh 2,048 Mbit/s vo VC-4

V 3 byte TU-12 PTR ghp phn tn trong a khung TU-12 ko di trong 500 s, nn pha thu cng mt 500 s mi c kt qu x l con tr ny. Hnh 2.3.3.2 ch minh ho ghp 63 khung TU-12 vo khung VC-4. Nhng trong thc t phi ghp 63 a khung TU-12 vo a khung VC-4. Vn ny c trnh by trong phn sau.

Sau khi hnh thnh khung VC-4, tip tc ghp khung VC-4 vo khung AUG v tip ghp khung AUG vo khung STM-1.Khi STM-1 ghp thm cc byte mo u on lp (RSOH), mo u on ghp (MSOH) v 9 byte con tr AU-4.

(3) Ghp 7 TUG-2 vo TUG-3

hiu r vic ghp 7 khung TUG-2 vo khung TUG-3, s dng hnh 2.3.3.3. Trc ht ghp 3 khung TU-12 thnh khung TUG-2 v sau ghp 7 khung TUG-2 thnh khung TUG-3.Ba khung TU-12 ghp xen byte thnh khung TUG-2 c 12 ct. Sau 7 khung TUG-2 ghp xen byte vo khung TUG-3. Nhng 7 khung TUG-2 ch c 84 ct nn khi TUG-3 n thm 18 byte vo ct th nht v th hai.Hnh 2.3.3.3- Ghp 7 khung TUG-2 vo khung TUG-3(4) Ghp 63 a khung TU-12 vo a khung VC-4

Hnh 2..3.3.4 th hin vic ghp 63 a khung TU-12 vo a khung VC-4.Hnh 2.3.3.4- Ghp 63 a khung TU-12 vo a khung VC- 4Mi khung VC-4 dnh 252 ct ghp 63 khung TU-12. 63 khung TU-12 ghp vo mt khung VC-4 c cng loi byte con tr. C th l trong khung VC-4 th nht c 63 byte V1, trong khung VC-4 th hai c 63 byte V2, trong khung VC-4 th ba c 63 byte V3 v trong khung VC-4 th t c 63 byte V4. Dy ch s trn cng ca hnh v (1 2 3 .....63, 1 2 3 .... 63...) biu th ghp xen byte 63 khung TU-12.

Trnh t ghp 63 khung TU-12 vo 252 ct (t ct 10 n ct 261) ca mi khung VC-4 nh sau:

Hng th nht: 63 byte V, 63 byte th hai, 63 byte th 3, 63 byte th t.

Hng th hai: 63 byte th nm, ...., 63 byte th tm. Ghp tip tc cc byte ca hng th ba, t, nm, su, by, tm.Hng th chn: 63 byte th 33, 63 byte th 34, 63 byte th 35 v 63 byte th 36.

(5) Chn m v chn dng

Trong qu trnh ghp 63 lung nhnh 2,048 Mbit/s vo khung STM-1 s dng kiu sp xp khng ng b sp xp cc byte ca lung nhnh ny vo a khung VC-12. Kiu sp xp nh vy c lin quan n chn m v chn dng. Vn ny c gii thch da vo hnh 2.26.

Hnh 2.3.3.5- Sp xp khng ng b lung nhnh E1 vo a khung VC-12

T hnh 2.3.3.5 thy rng trong khung VC-12 th t ch ghp (31 byte + 7 bit) tin I. Trong khi lung nhnh 2,048 Mbit/s cung cp cho khung ny 32 byte. V vy khi lung nhnh c tc bit nh mc 2,048 Mbit/s th S1 l bit n, S2 l bit tin I. Cu trc cc bit iu khin chn trong trng hp ny l C1C1C1 = 000 v C2C2C2 = 000. y l trng hp khng chn.

- Chn m

Khi tc lung nhnh tng 50 ppm th s bit tng trong mt a khung l: bTng= 2048 .103 bit 50. 10-6 : 2. 103 = 0,05 bit.Sau 20 a khung tc lung nhnh tng thm 1 bit. V vy phi chn vo a khung sau (a khung th 21) mt bit tin I. thc hin cng vic ny, trc ht thit b ci t C1C1C1 = 111 iu khin chn vo v tr bit S1 mt bit tin I v C2 C2 C2 = 000 iu khin bit S2 gi nguyn trng thi bit tin I.

- Chn dng

Chn dng xy ra trong trng hp lung nhnh gim tc bit 50 ppm. S bit gim trong mt a khung l 0,05 bit. Sau 20 a khung tc lung nhnh gim 1 bit. Vy phi chn vo v tr S2 ca a khung th 21 mt bit khng mang tin. Lnh iu khin chn dng gm C1C1C1 = 000 S1 vn gi nguyn trng thi bit khng mang tin v C2C2C2 = 111 chn 1 bit khng mang tin vo v tr S2.

Tm li, S1 l bit chn m khi C1C1C1 = 111; S2 l bit chn dng khi C2C2C2 = 111. Khi khng chn m v cng khng chn dng th C1C1C1 = 000 v C2C2C2 = 000.

2.4. Mo u on SOH v mo u tuyn POH

2.4.1. Mo u on

(1) Cu trc Cc byte mo u on trong khung STM-1 p dng cho mng thng tin quang nh hnh

2.4.1.1.

Hnh 2.4.1.1- Cu trc ca SOH

(2) Chc nng cc byte

A1 = 11110110, A2 = 00101000: su byte ng b khung

J0: nh v khung STM-1 trong khung STM-N (N= 4, 16, 64). Nu khng s dng cho chc nng ny th c th s dng nh tuyn on lp.B1: gim st li on lp, k hiu l BIP-8.

B2: ba byte gim st li on ghp knh, k hiu l BIP-24. E1: knh thoi nghip v kt ni trm lp vi trm ghp knh. E2: knh thoi nghip v kt ni cc trm ghp knh.

F1: knh iu hnh mng.

K1 v K2: knh truyn tn hiu chuyn mch bo v t ng v thng bo li D1 D3: cc knh truyn s liu kt ni trm lp vi trm qun l.

D4 D12: knh truyn s liu kt ni trm ghp knh vi trm qun l. M1: truyn cnh bo trng thi ca ng.

S1: Chuyn ti mc cht lng Q ca ng h ti trm ghp knh tip theo. Z1, Z2: cc byte d tr.(3) Mt s khi nim

- Knh truyn s liu DCC

D1 D3 l DCC t trm lp n trm qun l, c tc bit l 192 kbit/s (64 kbit/s 3). D4 D12 l DCC t trm ghp knh n trm qun l, c tc bit 576 kbit/s (64 kbit/s 9).

- Cc knh thoi nghip v

E1 v E2 s dng iu xung m PCM c tc bit 64 kbit/s. - S1Trong SDH c mt ng h ch quc gia c n nh cao nht, thng l ng h nguyn t, khng ch ng h tt c cc trm trong ton mng. ng h ny c truyn xung cc trm cp th hai v t ng h c truyn t cp cao hn xung cp thp hn lin k. Qua mi cp, cht lng ng h gim i mt t. ITU-T quy nh mc cht lng cho ng h tng cp. Bn bit cui ca S1 c s dng ch th mc cht lng Q ca ng h cc cp nh bng 2.2.

Bng 2.4.1.- Mc cht lng Q ca ng h

QS1 ngha

00000Khng tn ti

20010G.811,ng h cp1(cp quc gia)

30100G.812, ng h cp chuyn tip

41000G.812, ng h cp ni ht

51011ng h ni b thit b SDH

61111Khng s dng cho SDH

Hnh 2.4.1.2 minh ho vic s dng S1 chuyn ti mc cht lng Q.

Trm (nt) A ni vo ng h cp 1 c Q =2 (theo khuyn ngh G.811 ca ITU-T). T nt A ng h c truyn n nt B v gi km theo byte S1 = 0010 ch th ng h ly t ng h cp 1. Ti nt B, ng h Q=2 tin hnh ng b lung s u ra cng hng v u vng ngc hng. Theo quy nh ti bng 2.2, ng h u vng c Q = 6 cc nt khng s dng ng h cht lng thp ny. T nt B ng h c chuyn n nt C v gi km theo S1= 0010 thng bo ngun gc ca ng h ly t ng h cp 1. Ti C, ng h Q=2 ng b nt ny, ng thi a ra ngoi ng b ng h cp chuyn tip c Q= 3. ng h Q=3 ni vo hng thun chuyn ti nt C, ng thi ni trc tip sang hng ngc ng b lung ra ca cc nt theo hng ngc li .

Hnh 2.4.1.2- S dng byte S1 chuyn ti mc cht lng Q ca ng h ng b mng SDH

- BIP- n (n = 8, 24)

BIP-n l t m c n bit s dng kim tra tng chn cc bit trong khung nhm pht hin li trong khung . Th d tnh gi tr 8 bit ca BIP-8 nh hnh 2.4.1.3.em tt c cc bit th nht ca tt c cc byte trong khung STM-1 th nht (khung n) cng li. Nu tng l s l th bit th nht (b1) ca byte B1 trong khung STM-1 tip theo (khung n +1) bng 1. Nu tng l s chn th bit b1 ca byte B1 trong khung STM-1 # n+1 bng 0. Cng tt c cc bit th hai ca tt c cc byte trong khung STM-1 # n, nu tng l th bit b2 ca byte B1 trong khung STM-1 # n+1 bng 1, tng chn th bit b2 ca byte B1 trong khung STM-1 # n+1 bng 0. Tin hnh theo cch nh vy i vi cc bit tip theo. Cui cng, cng tt c cc bit th tm ca tt c cc byte trong khung STM-1 #1, nu tng l th b8 ca B1 trong khung STM-1 # n+1 bng 1, nu tng chn th b8 = 0.

Qua mi trm lp, b cng tin hnh cng cc bit cng th t ca cc byte, k c byte B1 trong khung STM-1 # n+1, nu pht hin c tng l th m 1 li. y l li khi.

i vi BIP-24 th gp 3 byte trong khung STM-1 #1 thnh mt khi con v xem mi khi con y l mt t m p dng cch tnh ton gi tr bit 1 n bit 24 ca BIP-24 trong khung STM-1 # n+1 nh trn.

Hnh 2.4.1.3- Nguyn tc tnh BIP-8Chc nng ca byte K1 v K2 nh hnh 2.4.1.4.

Hnh 2.4.1.4- Cu trc v cc chc nng ca K1 v K22.4.2. Mo u tuyn

(1) VC-3/ VC-4 POH

VC-3 hoc VC-4 u c 8 byte nh hnh 2.4.2.1

J1 Nhn dng im truy nhp tuyn VC-3 hoc VC-4

B3BIP-8

C2Nhn tn hiu

G1Ch th li u xa

F2 Knh iu hnh mng

H4S th t khung VC-4 trong a khung

F3Knh iu hnh mng

K3Knh iu khin APS cc tuyn VC3/ VC-4

N1Gim st im chuyn tip tuyn VC- 3 hoc VC-4

Hnh 2.4.2.1- Cu trc v chc nng VC-3/ VC-4 POH

- Byte J1:

J1 l byte u tin trong khung VC-3 hoc VC-4. V tr ca n trong khung c ch th bi 10 bit gi tr con tr. Trong mng quc gia hoc trong phm vi ngi iu hnh th m nhn dng im truy nhp lung mc cao ghp vo cc byte J1 l mt lot gm 4 tp hp, mi tp hp gm 16 byte c cu trc nh bng 2.4.2.

Bng 2.4.2.1- M nhn dng im truy nhp

C1 C2 C3 C4 C5 C6 C7 l t m kim tra s d chu trnh CRC- 7 ca khung ng lin trc. 0XXXXXXX l t m c k t theo khuyn ngh T50.

- BIP-8:

Cch tnh tm bit ca byte B3 trnh by trong phn tnh B1 ca SOH. Nhng cn ch y l tnh cho khung VC-3 hoc VC-4.- C2:

Byte C2 c s dng ch th thnh phn v cch sp xp ti trng trong khung VC-3/VC-4 nh trong bng 2.4.- G1

Byte G1 c s dng chuyn ti thng bo v trng thi v cht lng cui tuyn (u vo trm u xa) ti trm gc. Chc nng cc bit ca G1 c quy nh nh sau:Bit 1 n bit 4 ch th li u xa (REI) khi kim tra byte B3. Chn gi tr u ca 4 bit ch th t khng c li (0000) n 8 li (1000). By gi tr cui ca 4 bit ch th u xa khng c li.

Cc bit b5, b6, b7 ch th u xa khng hon ho (RDI) nh AIS, mt tn hiu VC-3/ VC-4 (LOS), mt khung (LOF). Khi xy ra cc s c th ci t b5 b6 b7 = 101 v chuyn v trm gc.

Bng 2.4.2.2- Cu trc ca C2

Cc bitCc bitMDin gii

b1 b2 b3 b4b5 b6 b7 b8HEX

000000000 0Khng trang b

000000010 1C trang b

000000100 2Cu trc TUG

000000110 3TU c nh

000001000 4Sp xp khng ng b E3 vo VC-3

000100101 2Sp xp khng ng b E4 vo VC-4

000100111 3Sp xp ATM

000101001 4Sp xp ti trng MAN

000101011 5Sp xp ti trng FDDI

01111110F ESp xp tn hiu o O.181

11111111F FVC-AIS

(2) VC-12 POH

Mo u tuyn mc thp gm c V5, J2, N2 v K4. - V5

y l byte ng u a khung VC-12. V tr ca n trong a khung TU-12 c ch th trong 10 bit gi tr ca con tr TU-12. Chc nng ca V5 c m t ti hnh 2.4.2.2.BIP-2REIRFINhn tn hiuRDI

12 34567 4

BIP-2- Kim tra li tuyn VC-12

REI- Ch th li u xa

RFI- Ch th c s c ti u xa

RDI- Ch th u xa khng hon hoHnh 2.4.2.2- Cu trc VC-12 POH BIP-2

T m kim tra tng chn c s dng kim tra li khi ca a khung VC-12. Hai bit ca BIP-2 c tnh nh sau:

em tt c cc bit l ca tt c cc byte trong a khung VC-12 # n cng li, nu tng chn th bit b1 ca V5 trong a khung VC-12 # n+1 bng 0, nu tng l th b1 ca V5 trong a khung VC-12 # n+1 bng 1. Cng tt c cc bit chn ca tt c cc byte trong a khung VC-12 # n, nu tng chn th bit b2 ca V5 trong a khung VC-12 # n+1 bng 0, nu tng l th b2 ca V5 trong a khung VC-12 # n+1 bng 1.

REI

u cui xa ln lt kim tra tng ca cc bit, k c cc bit ca V5, trong a khung VC-12 # n+1, nu pht hin c tng l th m mt li khi. Nu c li th ci t bit th ba ca V5 (REI) bng 1 v truyn ngc v trm gc.

RFI

Nu trm cui xa hng hc th ci t bit th t ca V5 bng 1 v truyn v trm gc. RDI

Trong cc trng hp u xa nhn c AIS, mt con tr TU-12 hoc mt a khung VC-12 th ci t bit th tm ca V5 bng 1 v truyn v trm gc.

b5, b6 v b7

y l nhn tn hiu, gii thch trng thi ca tn hiu VC-12 trong a khung VC-12 (bng

2.4.2.3).Bng 2.4.2.3- Cu trc nhn tn hiu VC-12

b5b6b7 ngha

000Khng trang b

001C trang b

010Sp xp khng ng b

011Sp xp ng b bit

100Sp xp ng b byte

101D tr cho pht trin

110Tn hiu o th O.181

111VC-AIS

- J2

Byte J2 l m nhn dng im truy nhp tuyn VC-12 c cu trc nh byte J0 v J1 c gii thch trong cc phn trn.- N2

Gim st im chuyn tip lung VC-12 v c cu trc nh bng 2.4.2.4.Bng 2.4.2.4- Cu trc ca N2

b1 b2b3b4b5b6b7b8

BIP-2"1"AIS nTC-REIOEITC- APId, TC-RDI, ODI

BIP-2

T m kim tra tng chn ca lung VC-12 ni chuyn tip. Cch tnh gi tr 2 bit ca t m ny trnh by trong phn BIP-2 ca V5. Ch khc l kim tra c thc hin ti im ni chuyn tip lung VC-12. Thng bo li va hin th ngay ti trm c ni chuyn tip x l s c, ng thi truyn cng hng v trm cui v li c ci t trong TC-REI.

Bit th ba c nh bng 1 ngn nga trng hp N2 l dy 8 bit 0.

Bit th su ch th li khi trong lung VC-12 u ra (OEI) Bit 7 v 8 ci t m nhn dng ni chuyn tip (TC- APId), ci t thng bo cho trm gc bit ti u xa lung ni chuyn tip VC-12 b mt hoc mt khung (TC-RDI), ci t ch th c AIS trong lung ni chuyn tip (ODI).

- K4

Knh chuyn ti tn hiu iu khin chuyn mch bo v t ng lung VC-12.

(3) S truyn tn hiu cnh bo

Cc tn hiu cnh bo truyn trong mt h thng thng tin SDH theo hng thun v c theo hng ngc. Hnh 2.4.2.3 tm tt hot ng cnh bo ca cc byte VC-n POH.

Trng hp th nht:

Khi mt trm hoc mt khi no ti u vo mt tn hiu thu (LOS), hoc mt khung (LOF), hoc nhn c tn hiu cnh bo AIS th ci t AIS trong tn hiu ra truyn cng hng cho trm hoc khi tip theo.Trng hp th hai:

Trm u cui xa xy ra LOS, LOF hoc nhn c AIS th ci t cnh bo RDI truyn ngc v cho trm gc.

Trng hp th ba:

Trm u cui ci t BIP-8 trong byte B1 kim tra li qua tng on lp, kt qu kim tra cn chuyn n trm u cui xa.Trng hp th t:

Cc khi u cui ng, lung mc cao (HOVC), lung mc thp (LOVC) ci t BIP-24 trong 3 byte B2 hoc BIP-8 trong byte B3 kim tra li ca cc khi tng ng, nu pht hin c li th ci t cnh bo REI truyn ngc v khi tng ng ti trm gc.Hnh 2.4.2.3- Truyn tn hiu kim tra v cnh bo trong h thng SDH

TM TT

Trong b ghp PCM-24 ca Bc M v PCM-30 ca chu u s dng k thut iu xung m chuyn i tn hiu thoi analog thnh tn hiu s. C hai loi thit b ny u s dng nn-dn s. Khung ca PCM-30 c 32 khe thi gian, trong 30 khe thi gian dnh ghp 30 knh thoi, 2 khe thi gian cn li ghp bo hiu v tn hiu ng b khung. Mi a khung ca PCM-30 c 16 khung nhm mc ch hnh thnh 16 khe thi gian TS16 ghp tn hiu ng b a khung v bo hiu ca 30 knh thoi.Trn th gii hin c 3 tiu chun tc bit PDH: chu u, Bc M v Nht Bn. Vit Nam s dng thit b ghp knh theo tiu chun chu u. Trong ghp knh PDH s dng k thut ghp xen bit. Chn bit nhm mc ch ng b tc bit cc lung nhnh trc khi ghp thnh lung c tc bit cao hn.

B ghp SDH ghp xen byte cc lung nhnh PDH ca chu u v Bc M to thnh STM-1, STM-4, STM-16 v STM-64 v STM-256. Con tr ng vai tr ng chnh lch tc khung gia khung tn hiu n v khung ghp. Mt khc, nh c con tr m vic xen- r knh trong SDH n gin hn nhiu so vi PDH. Cc byte mo u trong SDH rt phong ph v to thun li cho vic hnh thnh cc knh gim st, iu khin, bo dng, v.v. mng thng tin SDH.