pdh vÀ sdh

8/14/2019 PDH V SDH

1/13

PDH V SDH

inh Cng Thin Trang 1

SDH

- Tc SDH gm:

STM-1 = 155,52Mbit/s

STM-4 = 4.STM-1 = 622,08Mbit/s

STM-16 = 4.STM-4 = 2488,32Mbit/s

STM-64 = 4.STM-16 = 9953.28Mbit/s

Tc Bit c bn l: STM-1 = 155.52 Mbit/s

STM-N = N.STM-1

Tc bit ca cc tn hiu ghp bng mt snguyn vi tc bit c bn STM -1.

- Tc bit c bn trong SDH:Tc truyn: 155,52 Mbit/srng khung: 125 s2430 Bye gm: 6 hng 270 ct. STM-1 c dung lng l 63E1

- Payload: 9.261 Bye

+ Truyn tn hiu PDH c tc t2 Mbit/s n 140 Mbit/s

+ Cc tn hiu ny c chn trong STM-1

- SDH c 4 phn tchnh:

+ TRM: thit bghp u cui

+ ADM: thit bxen/rt lung

+ DXC: thit bkt ni cho

+ REG: thit blp

TRM c thghp cc lung nhnh thnh cc ngun tng hoc ngc li.

ADM: ly hoc chn lung nhnh vo lung tng.

REG: khuch i tn hiu

DXC: hon i a chca VC

M hnh: 1+1: c ngha l 1 card chy 1 card dphng

8/14/2019 PDH V SDH

2/13

PDH V SDH


T NG QUAN V TRUY N D N NG B SDH hi u ng khi nim v SDH/SONET, trc h t ta c n hi u ng th no l

ng b, khng ng b v cn ng b. Trong tp cc tn hiu ng b, vic

chuyn tip s liu trong tn hiu xy ra chnh xc cng mt tc . Tuy nhinvn c s lch pha gia nhng ln chuyn giao ca hai tn hiu, v s lch phany nm trong gii hn cho php. S lch pha ny c th do suy hao, tr thigian hay jitter trong mng truyn dn. Trong mng ng b, tt c cc ng hu tham chiu n mt ng h chun c s PRC.

1. Nhc im ca truyn dn cn ng b PDH1.1. Khi nim truyn dn cn ng b (PDH)V cc lung 2Mbit/s c to ra t cc thit b ghp knh khc nhau, nn tc bit c khcnhau mt cht. Do , trc khi ghp cc lung ny thnh mt lung tc cao hn phi hiu

chnh cho tc bit ca chng bng nhau, tc l phi chn thm cc bit gi. Mc d tc cclung u vo l nh nhau, nhng pha thu khng th nhn bit c v tr ca cc lung uvo trong lung u ra. Kiu ghp knh nh vy gi l cn ng b (PlesioSynchronous). 1.2. Nhc im ca PDH Vic tch/xen cc lung 2Mbit/s phc tp lm gim tin cy cng nh cht lng ca

h thng. Kh nng gim st v qun l mng km. Do trong cc khung tn hiu PDH khng cc

byte nghip v cung cp thng tin cho iu khin, qun l, gim st v bo dng hthng.

Tc bit ca PDH khng cao (tc bit cao nht c chun ho l 140Mbit/s trnmng vin thng quc t) khng th p ng cho nhu cu pht trin cc dch v bng rnghin ti v trong tng lai.

Thit b PDH cng knh, cc thit b ghp knh v thit b u cui thng c lp nhau. Trn mng vin thng tn ti 2 tiu chun phn cp khc nhau: chun Chu u v Chu

M, gy kh khn v phc tp khi nng cp, m rng v kt ni cc mng vi nhau. Cc mt hn ch trn ca PDH s c khc phc khi s dng phn cp truyn dn ng bSDH.

2. Truyn dn ng b SDH2.1. Khi nim SDH

hiu ng khi nim v SDH/SONET, trc ht ta cn hiu ng th no l ng b,khng ng b v cn ng b. Trong tp cc tn hiu ng b, vic chuyn tip s liu trong tnhiu xy ra chnh xc cng mt tc . Tuy nhin vn c s lch pha gia nhng ln chuyngiao ca hai tn hiu, v s lch pha ny nm trong gii hn cho php. S lch pha ny c thdo suy hao, tr thi gian hay jitter trong mng truyn dn. Trong mng ng b, tt c cc ngh u tham chiu n mt ng h chun c s PRC. chnh xc ca PRC l 10-12- 10-11vc ly t ng h nguyn t Cesium.

Hai tn hiu s l cn ng b nu s chuyn tip xy ra gn nh cng tc , v bt k sthay i no cng c cng bc trong mt gii hn nh. V d nu c hai mng tng tc vinhau, xung ng h ca chng c th ly t hai PRC khc nhau. Mc d cc PRC ny v cng

8/14/2019 PDH V SDH

3/13

PDH V SDH


chnh xc, nhng vn c s khc nhau gia hai loi. iu ny gi l s sai khc cn ng b. Trong trng hp mng khng ng b, s chuyn giao tn hiu khng nht thit phi xy ra

cng tc . Trong trng hpny, khng ng b c ngha l sai khc gia hai ng h lnhn sai khc cn ng b. V d, nu hai ng h ly t dao ng thch anh t do, chng cgi l khng ng b. Phn cp s cn ng b SDH v mng quang ng b SONET ch mt

tp hp cc tc truyn dn bng cp si quang c th truyn ti tn hiu s vi dung lngkhc nhau.Ngi ta chp nhn rng ri rng mt phng thc ghp knh mi c th c ng b v

khng ch da trn vic chn bit, gi l PDH, m cn da trn vic chn byte, l cc cu trcghp knh t 64kbit/s n tc c s 1,544kbit/s (1,5Mbit/s) v 2,048kbit/s (2Mbit/s).

SDH c nh ngha bi Vin tiu chun vin thng Chu u (ETSI), c s dng rt nhiu nc trn th gii. Nht Bn v Bc M cng xy dng cc tiu chun v SDHring. SONET do Vin tiu chun quc gia Hoa K pht trin v c ng dng Bc M. 2.2. Cc tiu chun SDH

Tiu chun mi xut hin ln u tin l SONET do cng ty Bellcore (M) a ra, cchnh sa nhiuln trc khi tr thnh tiu chn SDH quc t. C SDH v SONET c gii

thiu rng ri gia nhng nm 1988 v 1992. SDH c nh ngha bi Vin tiu chun vinthng Chu u (ETSI), c s dng rt nhiu nc trn th gii. Nht Bn v Bc M cngxy dng cc tiu chun v SDH ring. SONET do Vin tiu chun quc gia Hoa K pht trinv c ng dng Bc M.

Bng di y th hin cc tc tiu chun ca SDH v SONET.Mc d SONET v SDH c a ra ban u cho truyn dn cp quang, nhng cc h thngSDH hin ti vn tng thch cao vi c SDH v SONET.

Bng 1: Phn cp ng b SDH/SONET

Tn hiu SONET

Tc

bit(Mbit/s)

Tn

hiuSDH

Dung lngSONET

Dung lngSDH

STS-1, OC-1 51,840 STM-0 28DS1, hoc 1 DS-3 21E1

STS-3, OC-3 155,520 STM-1 84DS-1, hoc 3DS-3 63E1, hoc 1E4

STS-12, OC-12 622,080 STM-4 336DS-1, hoc12DS-3 252E1, hoc 4E4

STS-48, OC-48 2488,320 STM-16 1344DS-1, hoc 48DS-31008E1, hoc16E4

STS-192, OC-192 9953,280 STM-64 5376DS-1, hoc 192DS-34032E1, hoc64E4

8/14/2019 PDH V SDH

4/13

PDH V SDH


Bng 2: Phn cp khng ng b ANSI/ITU-T

ANSI ITU-T

Tn hiu Tc bit S knh Tn hiu Tc bit S knh

DS-0 64 Kbit/s 1 DS-0 64 Kbit/s 64 Kbit/s 1 64 Kbit/s

DS-1 1,544 Mbit/s 24 DS-0 E1 2,048 Mbit/s 1 E1DS-2 6,312 Mbit/s 96 DS-0 E2 8,450 Mbit/s 4 E1

DS-3 44,7 Mbit/s 28 DS-1 E3 34 Mbit/s 16 E1

E4 144 Mbit/s 64 E1

2.3. Tng lai ca SDH.Hu ht tt c cc h thng truyn dn quang hin nay trong mng cng cng u dng

SONET v SDH. Chng c mong i s thng tr mi trng truyn dn trong 10 nm, nhcng ngh PDH i trc lm c trong 20 nm (v hin vn cn c s dng, d rt t).Trong khi tc bit ca vi mng ng trc c k vng vt qua 40Gbit/s th cc tc nh hn hoc bng 155Mbit/s c dng rt rng ri trong cc mng truy nhp. 2.4. Ti sao cn ng b ha2.4.1. ng b v khng ng b.

Ni chung, h thng truyn dn l khng ng b, do mi thit b trong mng u s dngng h ring ca n. Trong truyn dn s, xung ng h l mt thng s rt quan trng. Xungng h c ngha l s dng mt chui cc xung lp i lp li gi cho tc bit ca d liukhng i v ch ra v tr cc bit 1 v 0 trong lung d liu. Ghp knh khng ng b tri quanhiu giaion. Cc tn hiu khng ng b, v d DS-1 ghp vi nhau, cng vi cc bit thmvo, gi l bit chn b cho s sai khc ca mi lung ring l, v kt hp vi cc bit khc (bitkhung) to ra mt lung DS-2. Cc bit chn li c s dng theo cch to ra cc DS-3v cao hn na. Chng ta khng th truy nhp ti cc lung khng ng b tc cao mkhng s dng cc b tch knh. Trong h thng ng b SONET/SDH, tn s trung bnh cacc ng h trong h thng l ging nhau (ng b) hoc gn ging nhau (cn ng b). Ming h c th truy ngc n ngun ng h chnh xc cao. Do , cc lung STS -1 ddng ghp vi nhau thnh cc lung tc cao hn m khng cn bit chn. V th, ta c th truynhp ngay n tc STS-1 cng nh cc tc cao hn STS-N.2.4.2. Phn cp ng b ha.

Cc tng i s thng c dng trong mng s phn cp ng b ha. Mng c t chctheo quan h ch-t (master-slave) vi ng h ca cc node cao hn cung cp tn hiu ng hcho cc node thp hn.Tt c cc node c th truy ngc n ngun ng h chun. Ngunng h chun PRC c chnh xc l 1x10-11theo khuyn ngh G.811 ca ITU-T. Cc ngunng h c chnh xc thp hn l SSU (ngun ng h ph) v SEC (thit b cp xung ng b) theo khuyn ngh ca ITU-T.

8/14/2019 PDH V SDH

5/13

8/14/2019 PDH V SDH

6/13

PDH V SDH


a. C-n: (n = 1-->4) l cc contener: Phn t ny c kch thc cha cc byte ti trngthuc mt trong cc lung cn ng b.

b. VC-n: l cc contener o:+ Contener o c s (n = 1,2): gm mt C-n (n = 1,2) n cng thm cc byte mang

thng tin iu khin v gim st tuyn ni hai VC-n ny v gi l POH.

+ Contener o bc cao hn VC-n (n = 3,4): gm mt C-n (n = 3,4) n v tp hp ccnhm khi nhnh (TUG-2S) hoc mt tp ca TU-3S cng vi cc byte mang thng tin iukhin v gim st tuyn ni hai VC-n v c gi l POH.

Con tr c s dng tm cc phn khc nhau ca AU v TU gi l container oVC. Con tr AU xc nh VC bc cao hn v con tr TU xc nh VC bc thp hn. V dAU-3 gm VC-3 cng vi mt con tr, TU-2 gm VC-2 cng vi mt con tr.

Mt VC l mt thc th ti chy trn mng c to ra v hy i im kt cui dchv hoc gn im . Cc tn hiu lu lng PDH c nh x ti cc container vi kchthc ph hp vi yu cu bng thng, s dng cc bit n bm tc ng h khi cn thit.Cc POH c thm vo sau cho mc ch qun l, to mt VC. Phn mo u ny c bi sau khi VC b hy v tn hiu gc ban u c ti to li. Mi tn hiu PDH c nh x vi

VC ca n, v cc VC vi cng kch thc khng ng k c ghp li bng cch chn byteto thnh ti SDH.c. TU-n (n = 1,2,3) l khi nhnh: gmmt VC cng thm mt con tr khi nhnh. Con tr

khi nhnh ch th s ng b pha ca VC-n i vi POH ca VC mc cao hn tip theo.Con tr khi nhnh c v tr c nh so vi POH mc cao hn.

d. AU-3S (S = 1 hoc 2) v AU-N (N=4): gm mt VC bc cao cng thm con tr khiqun l. Con tr khi qun l c v tr c nh trong khung STM -1 v th hin quan hv pha ca VC bc cao hn.

3.2. Cu trc khung STM-1Khung STM-1 bao gm 2430 bytes v thng c chia lm hai vng, tng ng vi 9

hng x 270 ct. di khung l 125s, tng ng vi tn s ca khung l 8000 Hz. Tc

truyn dn ca mt byte trong khung l 64 Kbit/s. Khung STM-1 gm 3 khi:e. Khi trng ti Payloadf. Khi con tr AUg. Khi SOH

Cc byte trong khung STM-1 c truyn tng hng mtv truyn t tri sang phi,bt u t hng th nht v ct th nht. Nh vy, sau 9 byte SOH (tr hng 4 l 9 byte AU)l 261 byte ti trng c truyn xen k.

+ Phn iu khin SOH: gm c 8x9 byte, gm cc byte cn thit cho dch v nht m ng b khung, cc byte b sung gim st, iu khin v qun l.

+ Phn trng ti : cc tn hiu phn nhnh, cc tn hiu POH trong khuyn nghG.703 ca CCITT t 2 Mbit/s n 140 Mbit/s c truyn ti trong cng ti trng gm c

9x261 byte.+ Phn con tr: Quan h thi gian gia trng ti v khung STM-1 c ghi li nh

con tr, ngoi ra n cn nh v cc tn hiu phn nhnh trong khi ti trng. Do , saukhi din gii con tr mt cch thch hp th c kh nng truy nhp ti tng knh ca ngis dng c lp bt k thi im no, m khng cn tch lung STM-1. Con tr hngth t, ct t 1 --> 9 gi l con tr vng A, cn con tr hng 1 -->3 v ct 11-->14 gi lcon tr vng B. Khung STM-1 c di 125s, c tn s l 8000 Hz, nh vy c truyn8000 ln/s. Do , tc bit ca tn hiu STM-1 l : 8000 x 9 x 270 x 8 = 155520 kbit/s

8/14/2019 PDH V SDH

7/13

PDH V SDH


Hnh 3. Cu trc khung STM-1

Cc mc cao hn STM-N ca phn cp ng b c hnh thnh bi cch chn byte vophn ti ca N tn hiu STM-1, thm cc mo u gp N ln mo u ca STM-1 v lp y vid liu qun l v gi tr con tr ph hp.

Hnh 4. Cu trc khung STM-44. Cc c ch bo v

C hai c ch bo v trong mng SDH: bo v tuyn tnh v bo v mch vng. 4.1. Bo v tuyn tnh

y l hnh thc d phng n gin nht, cn gi l bo v 1+1. y, mi ng lmvic c bo v bi mt ng bo v. Vic chuyn sang ng bo v xy ra khi xc nhc li nh l mt tn hiu LOS. Cu trc 1+1 l d phng 100% khi mi ng lm vic cmt ng bo v. Nhng do vn kinh t, nn ngi ta thng s dng c cu 1:N, nht lnhng ng truyn c khong cch xa. Theo cch ny, vi ng lm vic c bo v bng

8/14/2019 PDH V SDH

8/13

PDH V SDH


mt ng d phng. Cc ng d phng c th s dng cho cc lu lng c u tin thpv c th b ngt i khi ng phng thay th cho cc ng lm vic b li. C cu bo v1+1 v 1:N c tiu chun ha trong khuyn ngh G.783 ca ITU-T.

Hnh 5. S bo v tuyn tnh4.2. Bo v mch vng

Bo v mch vng c nhiu u im hn so vi bo v tuyn tnh. Mt mch vng bo v lcch n gin nht v hiu qu nht khi c mt s phn t mng lin kt vi nhau. C nhiu ccu bo v c dng cho loi mng ny, song ch c mt s c cu c tiu chu n ha theokhuyn ngh G.841 ITU-T. C 2 loi c cu mch vng l vng n hng v vng hai hng.

4.2.1. Mch vng n hng

Hnh 6. Mch vng bo v n hng

Trn hnh th hin cch thc c bn ca mch vng bo v n hng. Gi s c s gin on thng tin gia 2 phn t mng A v B, hng Y khng b nh hng bis c ny. Tt nhin, mt ng th hai c thit lp cho hng X. Do , kt ni ny cchuyn sang ng th hai trong phn t mng A v B. Cn hai phn t khc, C v D c

8/14/2019 PDH V SDH

9/13

PDH V SDH


chuyn qua ng d phng. Th tc ny gi l chuyn ng thng. Mt cch khc n ginhn c s dng l chuyn vng. Lu lng c truyn trn c hai ng lm vic v ngbo v. nu c s c, pha thu (trng hp ny l A) chuyn sang ng bo v v ngay lp tcduy tr kt ni.4.2.2. Mch vng hai hng

Trong cu trc mng ny, kt ni gia hai phn t mng l hai hng. Ton b dunglng mng c chia thnh nhiu ng, mi ng lm vic l hai hng. Nu cs c giahai phn t mng cnh nhau A v B, B s chuyn sang ng bo v. C th mang li hiu qubo v cao hn khi dng mch vng bo v hai hng vi 4 si cp, mi i cp chy c nglm vic v ng bo v. Kt qu, ta c cu trc bo v 1:1, ngha l d phng 100%.

Hnh 7. Mch vng bo v hai hng

5. Cc phn t ca mng ng bHnh v th hin cu trc ca mt vng SDH vi nhiu nhnh. c trng ca SDh l c

nhiu ng dng khc nhau c truyn trn mng. Mng ng b cn c kh nng truyn cc tnhiu cn ng b, cng nh kh nng iu khin cc dch v nh ATM. Tt c iu yu cumng phi c nhiu phn t khc nhau. V c bn, mng c 4 phn t sau: 5.1. B ti to tn hiu

Nh tngi ca n, phn t ny c nhim v ti to li xung ng h v bin catn hiu u vo b suy hao v mo dng do tn sc. Cc thng tin nhn c bng cch trch

ra nhiu knh 64 kbit/s trong phn mo u RSOH.

8/14/2019 PDH V SDH

10/13

PDH V SDH


B ti totn hiu

STM-NSTM-N

Hnh 8. S mng ng b5.2. u cui ghp knh TM

c s dng kt hp cc lung tn hiu cn ng b v ng b u vo thnh cclung STM-N c tc cao hn.

8/14/2019 PDH V SDH

11/13

PDH V SDH


u cuighp knh (TM)

PDHSTM-NSDH

5.3. B xen/r knh ADM

ADM

STM-N

STM-NPDH SDH

Cc tn hiu cn ng b v cc n hiu ng b tc thp c th c ly ra t cc lungng b tc cao hn, hoc c chn vo , s dng cc b ADM. c trng ny lm cho

ADM rt hu ch trong cc cu trc mch vng, to cc ng bo v trong vng trong trnghp xy ra s c. Ti mt nt ADM, ch nhng tn hiu no cn tht truy nhp mi cchn vo / hay r xung. Phn lu lng cn li tip tc c chuyn i trong mng m khngcn mt thit b c bit no khc.

8/14/2019 PDH V SDH

12/13

PDH V SDH


5.4. B u cho s DXCThit b ny c chc nng ng dng rt rng. N cho php nh x cc lung nhnh PDH

vo cc VC cng nh chuyn cc gi tr container thnh VC-4.

Hnh 9. Thit b u cho s

5.4.1. Qun l cc phn t mngB phn qun l mng vin thng TNM cng c xem nh mt phn t trong mng ng

b. Tt c cc phn t c cp trny u c qun l bng phn mm. Ngha l chngc th c gim st v iu khin t xa, mt trong nhng c tnh quan trng nht ca mngSDH. Chc nng ca TNM c tm tt l :"Vn hnh, qun l, bo dng v gim st -OAM&P".

Mt s li thng gptrong qun l, vn hnh mng truyn dn.

STT Cc li M t1 LOS (Loss Of

Signal)

LOS xy ra khi tn hiu ng b gim xung di ngngc BER =1x10

-3. N cng c th o t cp, suy gimmnh tn hiu hoc li thit b. Trng thi LOS c xakhi 2 khung lin tip nhn c khng thy du hiu caLOS mi.

2 OOF (Out of

Frame alignment)

OOF xy ra 4 hoc 5 khung SDH lin tip nhn c b li,mu khung khng hp l. Thi gian ln nht xc nhOOF l 625s. OOF xa khi nhn c 2 khung lim tipc mu khung hp l.

3 LOF (Loss of

frame alignment)

LOF xy ra khi OOF tn ti trong khong thi gian xcnh bng ms. LOF xa khi mt iu kin trong khung tntilin tip trong thi gian xc nh bng ms.

4 LOP (Loss of

pointer)

LOP xy ra khi nhn c N con tr lin tip khng hp l,

hoc nhn c N c d liu mi (NDF), y, N=8,9 v10. LOP xa khi c 3 con tr hp l bng nhau, hoc nhnc 3 ch th AIS lin tip.

5 AIS (AlarmIndicator Signal)

AIS l trng thi t t c cc bit =1. N c to ra thayth cho tn hiu bnh thng khi n bao gm mt iu kinli ngn cc li hoc cnh bo tng ln.

6 RDI (Remote

defect indication)

y l tn hiu tr v ca thip b truyn dn khi c cc liLOS, LOF hoc AIS.

8/14/2019 PDH V SDH

13/13

PDH V SDH


7 RFI (Remote

failure indication)

Mt li xy ra rt di khi vt qua thi gian ln nht chophp ca c cu bo v h thng truyn dn. Khi tnhhung ny xy ra, mt bn tin RFI s c gi n u xav s khi to chuyn mch bo v nu chc nng ny c kch hot.

KT LUNSDH mang li nhu li ch to ln cho nh cung cp mng:

Tc truyn dn cao: Tc truyn dn c th t ti 10Gbit/s, do ph hpvi cc mng ng trc, mng li.

Chc nng xen/r knh n gin: so vi PDH, SDH d dng chn cc lung tc thp vo lung tc cao, v cng nh ly cc lung tc thp hn ra khi cclung tc cao hn.

Kh nng p ng cao v dung lng ph hp: vi SDH, nh cung cp d dng vnhanh chng p ng yu cu ca khch hng. Cc phn t mng c qun l viu khin t trung tm, s dng h thng TNM.

tin cy cao: mng SDH hin i c nhiu c ch bo v v d phng khcnhau. Li mt phn t trong mng khng th gy li ton b h thng.

Lm nn tng ca nhiu dch v tng lai: Ngay by gi, mng SDH l nntng cho cc dch v POTS, ISDN, di ng...N cng d dng p ng c cc dchv video theo yu cu, truyn hnh s qung b...

Kt ni d dng vi cc h thng khc: Giao din SDH c tiu chun ha toncu, c th kt hp nhiu phn t khc nhau trong cng mt mng v tng tc vicc mng khc d dng.

Sp ti, cng ngh ghp knh phn chia theo bc sng DWDM sn sng c s dng thayth cho SDH. Cng ngh ny c th truyn nhiu bc sng trong cng si quang nmode. Hin ti c th truyn 16 bc sng, t 1520nm n 1580nm, do tc truyn dn

c th t ti 40Gbit/s v cao hn na trn mt si quang. Do , c th ni rng DWDM lcng ngh truyn dn quang ca tng lai.

Ht

pdh vÀ sdh

Documents