Sdh

GVHD: ThS. Ph Trn TnCp quang truyn dn ng b SDHMC LC1. NGUYN L GHP KNH PDH51.1 CC TC BIT CA ANSI/CEPT51.2 CU TRC KHUNG CA TN HIU PDH.61.3 GHP V TCH LUNG TRONG PDH.71.4 NHC IM CA PDH92. GII THIU V SDH92.1 KHI QUT V SDH91) Cho php xy dng mt mng vin thng kinh t v linh hot:102) Tng cng kh nng bo tr v qun l mng:103) Cung cp kh nng truyn ti tn hiu linh hot:114) Cho php xy dng mt h tng mng vin thng thng nht:112.2 TRUYN DN NG B L G?132.3 TC TRUYN DN TRONG SDH152.4 CU TRC KHUNG SDH162.5 CU TRC GHP KNH SDH203. MT S PHNG PHP TO TN HIU STM-1233.1 SP XP TN HIU 140MB/S VO KHUNG STM-1233.2 SP XP 3 TN HIU 34MBIT/S VO KHUNG STM-1244. CON TR SDH264.1 NHIM V CON TR265. MO U TRONG SDH265.1 MO U ON TI SINH275.2 MO U ON GHP KNH MSOH285.3 MO U TUYN POH CP CAO (VC-4/VC-3)295.4 MO U TUYN POH CP THP (VC-2/VC-1)306. NG B MNG316.1 MC CH NG B316.2 CC PHNG PHP NG B327. KT LUN347.1 U IM CA H THNG SDH347.2 NHC IM CA SDH35TI LIU THAM KHO36

DANH MC HNHHnh 1: Cc bc chuyn tn hiu analog thnh digital dng PCM4Hnh 2: Phn cp s cn ng b ca Bc M (ANSI)5Hnh 3: Phn cp s cn ng b ca Nht Bn5Hnh 4: Phn cp s cn ng b ca chu u (CEPT)5Hnh 5: Cu trc khung tn hiu PDH6Hnh 6: S ghp v tch lung trong PDH7Hnh 7: S xen r lung7Hnh 8: Ghp cc lung 2Mb/s thnh tn hiu ng dy140Mb/s (PDH) v 155Mb/s (SDH)11Hnh 9: Trm ghp/r knh PDH v SDH11Hnh 10: Phn cp ng b SDH/SONET14Hnh 11: Phn cp khng ng b ANSI/ITU-14Hnh 12: Cu trc khung SDH15Hnh 13: Qu trnh to VC-4 u pht v khi phc tin hiu u htu16Hnh 14: Cu trc khung STM-N17Hnh 15: Cu trc khung STM-118Hnh 16: Cu trc khung STM-418Hnh 17: Cc loi knh o19Hnh 18: Cu trc b ghp SDH G.709 ITU-T19Hnh 19: Cc bc ghp knh ng b21Hnh 27: Sp xp tn hiu 140MB/s vo khung C-422Hnh 28: Khung ti trng C-422Hnh 29: Sp xp tn hiu 34Mbit/s vo C-323Hnh 30: Ti trng khung C-323Hnh 31: Sp xp 3x34 Mbitps vo STM-124Hnh 20: on lp, on ghp v tuyn truyn dn trong SDH25Hnh 21: RSOH STM-126Hnh 22: MSOH STM-127Hnh 23: POH CP CAO (VC-4/VC-3)28Hnh 24: Cu trc POH cp thp29Hnh 25: Cu trc byte V530

NGUYN L GHP KNH PDHT khi hnh thnh cho n nay, mng in thoi ch yu truyn tn hiu ting ni (tn hiu u ra my in thoi cn gi l tn hiu thoi)Trc nm 1970, truyn i xa mng in thoi thng s dng tn hiu tng t (analog) v ghp knh theo tn s (FDM). Phng tin truyn dn ch yu s dng dy kim loi trn hoc cp ng trc. H thng truyn dn analog ny c dung lng v cht lng thp chi ph cho khai tht bo dng rt ln.u nhng nm 1970, cc h thng truyn dn s (digital) bt u pht trin.Trn cc h thng ny ch yu s dng iu ch m xung (PCM) v ghp knh theo thi gian (TDM) .Nh k thut PCM m tn hiu thoi analog c bng tn (0-4) KHz c chuyn thnh tn hiu digital c tc 64 kb/s.Cc bc thc hin PCM c th tm tt trn s hnh 1.

Hnh 1: Cc bc chuyn tn hiu analog thnh digital dng PCMNhng nu truyn ring bit tng knh 64kb/s trn dy cp ng (hoc vi ba) s rt lng ph. V vy, ngi ta ghp cc knh s 64kb/s thnh cc lung s c tc cao hn nh ghp cc knh s 64kb/s thnh lung s 1.544kb/s ( Bc M v Nht Bn) hoc 30 knh s 64kb/s thnh lung s 2.048Mb/s ( Chu u) ri mi truyn i (gi l lung cp 1). T cc lung cp 1 ny li tin hnh ghp c c cc lung s c tc cao hn. H thng ghp knh s nh vy gi l H phn cp s cn ng b PDH (Plesiochronous Digital Hierarchy).CC TC BIT CA ANSI/CEPTCc cp truyn dn s cn ng b ang tn ti theo nhiu tiu chun khc nhau: Bc M (ANSI), Nht v Chu u (CEPT).Theo chiu chun ca Bc m, to thnh s cp cao ngi ta thc hin nh hnh 2:

Hnh 2: Phn cp s cn ng b ca Bc M (ANSI)Tiu chun ca Nht Bn (hnh 3):

Hnh 3: Phn cp s cn ng b ca Nht BnTheo tiu chun Chu u, mun c lung s cp cao hn th phi ghp 4 lung s cp thp hn (hnh 4):

Hnh 4: Phn cp s cn ng b ca chu u (CEPT)CU TRC KHUNG CA TN HIU PDH. u pht, ngi ta ghp cc tn hiu s cp thp to ra lung s cp cao bng phng php xen bit. phn th ng b vi phn pht v phn vic c cc khung, lm c s cho vic tch cc lung s cp thp t lung s cp cao nhn c th khi ghp knh ngi ta ci mt t hp cc bt gi l tn hiu ng b khung (FAS) v trc mi khung truyn. Tip theo l cc bt nghip v (D+S) cnh bo t xa cho trm i bit s c ca trm mnh tip theo mi l cc bit ca lung s liu cc nhnh a vo ghp knh.Thc t, cc lung s cp thp c tc khng bng nhau (do t nhiu ngun ng h khc nhau) nn thc hin ghp knh ngi ta phi dng k thut chn thm bit (justification) nhm to ra mt t chung ng u cho tt c cc lung nhnh trc khi ghp xen bit. Chnh v vy, phn thu nhn bit cv c bin php tch cc bit thm ny, nhm khi phc ng lung s liu ban u th phn pht ngi ta dng mt t hp cc bit gi l cc bit kim sot chn (CB) ghp thm vo khung lung s cp cao m bo ch ra chnh xc qu trnh chn bit c c thc hin ng hay khng.Do c im trn m cu trc mt khung ca lung s cp cao sau khi ghp knh s c dng nh hnh 5.

Hnh 5: Cu trc khung tn hiu PDHGHP V TCH LUNG TRONG PDH. Ghp lung trong PDH l ghp xen bit,do phi chn thm bit trong qu trnh ghp nn tc ca tn hiu sau khi ghp bao gi cng ln hn tng tc ca tn hiu nhnh.do vy khng th tch trc tip cc lung s cp thp t lung s cp cao(do khng th bit chnh xc quan h v pha gia tn hiu ng b khung ca lung s cp thp trong lung s cp cao). Sau mi cp ghp knh,thit b s a vo lung s tn hiu ng b khung mi.S ghp v tch lung trong PDH nh hnh 6. S xen r lung biu din nh hnh 7.

Hnh 6: S ghp v tch lung trong PDH

Hnh 7: S xen r lung Nhn xt: Tc bit ca h ANSI:1,5Mb/s ,6Mb/s ,45Mb/s v 405Mb/s. Tc bit ca h CEPT: 2Mb/s ,8Mb/s ,34Mb/s,140 Mb/s. Mi tn hiu sau khi ghp knh c cu trc khung khng nh nhau. Cc tn hiu nhnh khng s dng ng b khung. Cc tn hiu nhnh gn n b ni nhau(gi l cn ng b), tc l tn s nhp mc d c cng gi tr nhng li hi khc nhau.NHC IM CA PDHMng PDH ch yu p ng cc dch v thoi, i vi cc dch v mi nh: in thoi truyn hnh, truyn s liu, th mng PDH kh c th p ng c.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 h thng.Tc bit ca PDH khng cao (tc bit cao nht c chun ho l 140Mbit/s trn mng vin thng quc t) khng th p ng cho nhu cu pht trin cc dch v bng rng hin 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.S hn ch v kh nng xen r cc lung kin kt ni km linh hot v kh cung cp dch v nhanh chng,ng thi i hi nhiu thit b ghp knh lm cho gi thnh tng ln.Cc mt hn ch trn ca PDH s c khc phc khi s dng phn cp truyn dn ng b SDHGII THIU V SDHKHI QUT V SDHH phn cp s ng b SDH (Synchronous Digital Hierarchy) l mt chun quc t v truyn dn ng b tc cao cho cc mng vin thng quang, c Lin minh vin thng quc t ITU (trc y gi l U ban t vn v in thoi v in bo quc t CCITT) ph chun ln u tin vo thng 111988, ni dung gm cc khuyn ngh G.7 ny nh ngha v tc truyn, khun dng tn hiu, cc cu trc ghp knh v cch x l, sp xp cc bit truyn ng vi mt dch v vo mt cu trc ti trng SDH cho mt giao din nt mng NNI (Network Node Interface giao din chun quc t ca SDH).Bn cnh vic xc nh cc chun giao din cho NNI nh trn, CCITT cn xy dng mt lot cc chun khc qun l hot ng ca cc b ghp knh ng b (nh G.781, G.782 v G.783) v qun l mng SDH (nh G.784). Vic tiu chun ho cc thit b SDH vic qun l mng kinh t, linh hot hn, ph hp vi cc i hi ca cc nh iu hnh mng, nhm p ng cho cc dch v mi bng rng trong tng lai.Khi nim v mt h thng ti ng b, da trn cc chun SDH khng nhng vt ra khi nhu cu c bn ca h thng truyn dn im ni im m cn p ng c nhng i hi ca cc mng chuyn mch, truyn dn v iu khin mng. Nhng kh nng 3 vng ng dng mng truyn thng l: mng ni ht (Local Network), mng lin i (Interexchange Network) v mng ng di (Long Haul Network). Mc d SDH da trn vic a mt tn hiu ghp knh ng b vo mt lung quang truyn trn cp si quang, thc t SDH cng c s dng trn cc tuyn v tuyn tip sc, thng tin v tinh v cc giao din in trong thit b vin thng. Do , c th ni SDH to ra mt h tng mng vin thng thng nht.Vi tnh linh hot, truyn di rng v cu hnh n gin lm cho h thng PDH hin nay. Cc u im gm:Cho php xy dng mt mng vin thng kinh t v linh hot: Cc chun SDH c xy dng da trn nguyn l ghp knh ng b trc tip, y l yu t then cht to nn tnh kinh t v linh hot ca mng vin thng. Thc cht, iu c ngha l cc tn hiu nhnh c th c ghp trc tip vo mt tn hiu SDH tc cao hn m khng cn qua cc cp ghp trung gian. Cc phn t mng SDH c th c kt ni trc tip trn mng vi rt t thit b nn c hiu qu kinh t rt cao. (V d, s so snh ghp PDH v SDH). Tng cng kh nng bo tr v qun l mng: Vic tng cng cc kh nng bo tr v qun l mng l yu cu khng th thiu i vi mt mng vin thng. thc hin iu , SDH c cu trc nhiu lp trong mt cu hnh ghp knh, ti cc lp tng ng vi cc vng bo tr (on v tuyn) u c thng tin y v r rng h tr cho vic iu hnh khai thc v bo tr cho vic iu hnh vng tng ng trn mng. Trong mt cu trc tn hiu SDH, ngi ta dnh ra khong 5% dung lng s dng cho cc th tc qun l, bo tr v thc hnh mng ( h thng PDH ch c khong 0,5%).Cung cp kh nng truyn ti tn hiu linh hot: Tn hiu SDH c kh nng truyn tt c cc tn hiu nhnh hin c trn cc mng vin thng PDH hin nay (nh cc tn hiu nhnh 2, 34 v 140 Mb/s ca chu u CEPT cng nh cc tn hiu nhnh DS1, DS2 v DS3 ca Bc M). Tc l, SDH c th hon ton tng thch vi mng hin c. Ngoi ra, SDH cn c kh nng truyn ti cc tn hiu bng rng ng vi cc dch v tin tin trong tng lai nh: Phng thc truyn khng ng b ATM (Asynchronous Transfer Mode): chun cho B-ISDN. Giao din truyn s liu phn tn trn cp quang FDDI (Fiber Distributed Data Interface): chun cho mng cc b LAN tc cao.Cho php xy dng mt h tng mng vin thng thng nht: Nhm t c tnh mm do, cu trc tn hiu SDH c ti u ho i vi c mng truyn dn v cc ng dng chuyn mch. iu lm cho vic qun l mng rt n gin trn c 3 vng ng dng vin thng truyn thng ni trn. C th c mt h tng mng SDH duy nht, trong cho php kt ni gia cc vng trc tip, hiu qu v n gin. Ngoi ra, SDH cn a ra mt giao din mng chun ho l NNI, cho php kt ni trc tip thit b truyn dn ca nhiu nh cung cp thit b khc nhau.

Hnh 8: Ghp cc lung 2Mb/s thnh tn hiu ng dy140Mb/s (PDH) v 155Mb/s (SDH)

Hnh 9: Trm ghp/r knh PDH v SDHTRUYN DN NG B L G? Khi nim v ng b ca cc tn hiu s hiu chnh xc cc khi nim v cc ni dung ca SDH, vn quan trng l phi hiu ng khi nim th no l ng b, cn ng b v khng ng b?Hai tn hiu c gi l ng b vi nhau nu nh s dch chuyn s ca chng l cng mt tc mt cch chnh xc. Thc t, vn c th c s sai pha gia hai tn hiu nhng iu khng c vt qu gii hn cho php. S sai pha ny c th do tr truyn sng hoc do hin tng tri tn thp (low-frequency wander) trong mng truyn dn. Trong mng ng b, tt c ngh u hot ng theo mt ng h chun PRC (Primary Reference Clock). chnh xc ca PRC l khng ti hn 10-11 v nhn c t ng h chun nguyn t Cesium.Hai tn hiu s c gi l cn ng b nu nh s dch chuyn s ca chng ch "gn nh" cng mt tc vi s bin thin v tc b rng buc trong mt gii hn rt cht ch. Gii hn ny c ITU-T a ra trong khuyn ngh G.811. V d, nu hai mng c ni vi nhau v chng c hai ng h chun ly t hai ngun PRC khc nhau, mc d cc tn s nhp ny l rt chnh xc nhng gia chng vn c s chnh lch tn s no - iu ny c th hiu nh l cn ng b.Trong trng hp tn hiu khng ng b, cc tn hiu khng nht thit phi dch chuyn theo cng mt tc . Khi nim khng ng b trong trng hp ny c th hiu l s sai khc gia hai ng h phi ln hn s sai khc ca hai ng h trong trng hp cn ng b. V d, hai ng h ly t hai ngun dao ng thch anh. ng b v khng ng b trong truyn dn sThng thng, cc h thng truyn dn s l khng ng b, trong mi thit b u cui ni chung u hot ng theo nhp ng h ring ca n. Trong truyn dn s, yu t "nh thi" (timing) l mt trong nhng hot ng c bn nht ca h thng.Do cc ng h ny khng ng b nn c s chnh lch v tn s gia chng, dn n tc lung bit ca chng cng khng bng nhau. V d, lung E3 c tc cho php l 34 Mb/s 20.10-6, tc l c th gy ra chnh lch v tc ln n 1789 bit/s so vi mt lung E3 khc.Ghp lung khng ng b phi s dng s ghp nhiu cp. Cc tn hiu khng ng b, v d nh cc lung 2 Mb/s (E1), c ghp vi nhau (theo kiu xen bit) v s dng cc bit ngoi b sung (nhi bit) b li s chnh lch v tc gia chng, ng thi cng vi cc bit khc (cc bit khung) to ra lung s E2 cp cao hn (8 Mb/s). K thut xen bit v nhi bit li c s dng ghp cc lung E2 thnh lung E3 (34 Mb/s) v c nh vy to ra lung s cp cao hn. Chnh v vy, khng th nh v c cc lung E1 trong khung ca E3, hay khng th truy nhp c lung cp thp trong lung cp cao. Mun ly mt lung cp thp trong lung cp cao th phi s dng thit b tch knh xung theo tng cp.Trong h thng ng b (nh SDH) th li khc, tn s trung bnh ca tt c cc ng h trong h thng l nh nhau. Mi ng h th cp u bm theo mt ng h chun c n nh rt cao. Do vy, tc lung s STM-1 lun c gi vng 155,52 Mb/s, lm cho vic ghp cc lung STM-1 li vi nhau khng phi dng k thut nhi bit, dn n vic truy nhp vo lung STM-1 t lung cp cao hn (v d STM-N) rt d dng.Cc lung nhnh tc thp nh 2,048 Mb/s c chuyn trong container o (VC12) vi tc hi cao hn (2,304 Mb/s). tch ra lung nhnh t VC, ngi ta dng c ch "con tr" kt hp vi cc b m b li s chnh lch v tn s nhp ca cc ng h cng nh s tri pha, trnh c hin tng mt d liu khi mt ng b. Phn cp tn hiu ng bTrong mng vin thng c cc h thng chuyn mch s v ni cho s, tn hiu ng b thng c chia thnh cc cp khc nhau. Trn mng, cc tn hiu ng h s quan h vi nhau theo kiu ch-t tu theo chnh xc ca tn hiu ng h. Cc nt c ng h chnh xc hn s cp tn hiu nh thi cho ng h cc nt cp thp hn. Tt c ng h ca c theo ng h chun PRC. ng b trong SDHTn hiu ng h ca bn thn mt thit b u cui SDH c th nhn c t khi cung cp tn hiu ng b SSU (Synchronisation Supply Unit) thng qua cc h thng chuyn mch v cc thit b khc. Do , thit b u cui ny c coi l thit b ch (master) i vi cc nt SDH khc, cung cp tn hiu nh thi vo tn hiu STM-N u ra ca n. Cc nt SDH khc s lm vic trong ch t (slave) vi ng h ca chng c nh thi theo tn hiu STM-N nhn c. Cc chun hin nay quy nh mt mng SDH phi nhn tn hiu nh thi t mt ngun ng h chun PRC. TC TRUYN DN TRONG SDH Tiu chun mi xut hin ln u tin l SONET do cng ty Bellcore (M) a ra, c chnh sa nhiu ln 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 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 SDH ring. SONET do Vin tiu chun quc gia Hoa K pht trin v 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 thng SDH hin ti vn tng thch cao vi c SDH v SONET.Tn hiu SONETTc bit (Mbit/s)Tn hiu SDH Dung lngSONETDung lngSDH

STS-1, OC-151,840STM-028DS1, hoc 1 DS-321E1

STS-3, OC-3155,520STM-184DS-1, hoc 3DS-363E1, 1E4

STS-12, OC-12622,080STM-4336DS-1, hoc12DS-3252E1, 4E4

STS-48, OC-482488,320STM-161344DS-1, hoc 48DS-31008E1, 6E4

STS-192,OC-1929953,280STM-645376DS-1, hoc 192DS-34032E1, 4E4

Hnh 10: Phn cp ng b SDH/SONETANSIITU-T

Tn hiuTc bitS knhTn hiuTc bitS knh

DS-064 Kbit/s1 DS-064 Kbit/s64 Kbit/s1 64 Kbit/s

DS-11,544 Mbit/s24 DS-0E12,048 Mbit/s1 E1

DS-26,312 Mbit/s96 DS-0E28,450 Mbit/s4 E1

DS-344,7 Mbit/s28 DS-1E334 Mbit/s16 E1

E4144 Mbit/s64 E1

Hnh 11: Phn cp khng ng b ANSI/ITU-

CU TRC KHUNG SDH Cu trc chung tn hiu SDH

Hnh 12: Cu trc khung SDHTn hiu ng b sdh bao gm mt tp cc byte 8 bit c biu din di dng mt cu trc khung.trong cu trc cc byte u c nh vi mt cch r rng trong mi quang h i vi khung.C th mi khung trong lun tn hiu ni tip c th biu din bng m bng gm N hng v M ct.Mi vung trong bn ng vi mt byte 8 bit ca tn hiu ng b.byte u tin hng 1 ct 1 gi l byte nh du khung F n cho php inh v cc byte khc trong khung mt cch d dng.Cc bit tn hiu s truyn theo trnh t bt u l byte F v t tri qua phi,t trn xung di(ht hng th 1 n hng th 2).sau khi truyn ht byte cui cng ca khung(byte hng th N v ct th M) th qu trnh truyn lp li bt u t byte F ca khung tip theo. Cu trc khung ti ng bCc tn hiu nhnh khi truyn qua mng ng b vn c gi nguyn hnh thnh nn thut ng khung ti ng b p dng cho cc cu trc tn hiu ng b. Tuy nhin iu quang trng hn l dung lng tn hiu t bn trong mt khung ti ng b.hnh thnh kh nng ti ca mng. Mt khung ti ng b bao gm 2 thnh phn khc nhau: Phn container o (Virtual Continer - VC) v phn mo u on (Section Overheat SOH) Container o VCCc tn hiu nhnh PDH c xp vo container ni cnh khc container la s nh x cc tn hiu PDH thanh mt khung dng sdh theo mt khun dng xc nh.Sau container c b xung mt s byte phc v cho viec giam st,bo tr quang l container chuyn t u pht n u thu cc byte b xung gi l mo u tuyn POH(path overhead) v container sau khi c gn POH l container o (VC). VC c truyn t u cui n u cui hay VC chi c xp v d ch 1 ln cho d n c th c chuyn nhiu ln t h thng ti ny sang h thng ti khc trong qu trnh lun chuyn qua mng.vd qu trnh hnh thnh VC-4 u pht v khi phc tn hiu PDH 140Mb/s u thu c biu din nh hnh sau.

Hnh 13: Qu trnh to VC-4 u pht v khi phc tin hiu u thu Mu u on SOHSOH l mt s byte mt s v tr xc nh rong khung ti m nhim cc chc nng(nh gim st kim sot li bt va to cc knh thng tin s liu) phc v cho vic vn chuyn VC gia cc nt(gm cc trm ti sinh,xen/r hoc trm ni cho s)trong mng ng b.SOH c gng vo h thng ti v khong b chuyn cng cc VC gia cc h thng ti.Cu trc chung mt module chuyn ti ng b STM-N nh sau

Hnh 14: Cu trc khung STM-N 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 125ms, 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: Khi trng ti Payload Khi con tr AU Khi SOHCc byte trong khung STM-1 c truyn tng hng mt v 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 nh t 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 ngh G.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 , sau khi din gii con tr mt cch thch hp th c kh nng truy nhp ti tng knh ca ngi s dng c lp bt k thi im no, m khng cn tch lung STM-1. Con tr hng th t, ct t 1 9 gi l con tr vng A, cn con tr hng 13 v ct 1114 gi l con tr vng B.Khung STM-1 c di 125ms, c tn s l 8000 Hz, nh vy c truyn 8000 ln/s. Do , tc bit ca tn hiu STM-1 l:8000 x 9 x 270 x 8 = 155520 kbit/s

Hnh 15: Cu trc khung STM-1Cc mc cao hn STM-N ca phn cp ng b c hnh thnh bi cch chn byte vo phn ti ca N tn hiu STM-1, thm cc mo u gp N ln mo u ca STM-1 v lp y vi d liu qun l v gi tr con tr ph hp.

Hnh 16: Cu trc khung STM-4 Container oSDH c mt khi nim gi l VC qua s dng con tr v cc gi tr offset, cc VC c th c truyn trong ti trng SDH nh l cc gi d liu c lp.Cc VC c s dng ti cc tn hiu nhnh tc thp hn.Nhm tng kh nng truyn ti linh hot c nhiu loi VC ng dng cc kh nng ti khc nhau, nh bng sau

Hnh 17: Cc loi knh oCU TRC GHP KNH SDHH thng s ng b c hnh thnh t cc h thng cn ng b khc nhau, cc h thng cn ng b ny c th thuc h Chu u hoc Bc M. u vo ca cc h thng ng b c s l cc lung cn ng b c tc bt khc nhau, c ghp li thnh nhiu bc, mi bc li c a vo cc bit iu khin, qun l v phi hp tc . Khi , u ra c mt lung ng b c s. Cc lung ng b c s c nng ln N ln thnh cc lung ng b cp N. Cu trc b ghp SDH nh hnh 18.

Hnh 18: Cu trc b ghp SDH G.709 ITU-TCc ch s trong hnh ny lin quan n cc tc truyn dn cn ng b nh sau:11tng ng vi1554 Kbit/s

12tng ng vi2048 Kbit/s






Ch s u tin i din cho mc phn cp truyn dn nh quy nh trong G702-"Tc bit ca cc cp truyn dn s", v ch s th hai c trng cho tc thp hn (1) v cao hn (2). Cn ch s 4 l mc th 4, bng 140 Mbit/s c trong tiu chun Chu u v Bc M. Cc khi c k hiu v chc nng sau y: C-n: (n = 14) l cc contener: Phn t ny c kch thc cha cc byte ti trng thuc mt trong cc lung cn ng 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 cc nhm khi nhnh (TUG-2S) hoc mt tp ca TU-3S cng vi cc byte mang thng tin iu khin v gim st tuyn ni hai VC-n v c gi l POH.

Hnh 19: Cc bc ghp knh ng bCon tr c s dng tm cc phn khc nhau ca AU v TU gi l container o VC. Con tr AU xc nh VC bc cao hn v con tr TU xc nh VC bc thp hn. V d AU-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 dch v hoc gn im . Cc tn hiu lu lng PDH c nh x ti cc container vi kch thc 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 b i 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 byte to thnh ti SDH. TU-n (n = 1,2,3) l khi nhnh: gm mt 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. AU-3S (S = 1 hoc 2) v AU-N (N=4): gm mt VC bc cao cng thm con tr khi qun l. Con tr khi qun l c v tr c nh trong khung STM-1 v th hin quan h v pha ca VC bc cao hn. Cc nv nhnh TU v n v quang tr AU ( vung in m) l ni x l con tr. Cc bit ghp v phn knh ng b c th c biu din nh hnh 19.MT S PHNG PHP TO TN HIU STM-1SP XP TN HIU 140MB/S VO KHUNG STM-1 Sp xp tn hiu 140MB/s vo khung C-4

Hnh 20: Sp xp tn hiu 140MB/s vo khung C-4Trc khi a vo module chuyn ti ng b STM-1, lung s cn ng b 139264Kbit/s phi c a vo container C-4.Ti trng ca C-4 gm 9 hng v 260 ct (tc l c 9x260=2340 byte), trong khi s bit ca lung s PDH 140Mbit/s (chnh xc l 139264 kbit/s) l:139264 kbit/s : 8000Hz= 17408 bit (2176 byte)

Hnh 21: Khung ti trng C-4Tn hiu 140Mbit/s chim cha y mt ti trng C-4. Trong thi gian 125s, phn t C-4 b xung thm 164 byte (bit chn c nh, cc bit chn, cc bit iu khin chn, cc bit mo u OH, bit ng b) u ra t tc nh mc 2340 byte. Sp xp tn hiu C-4 vo STM-1 a C-4 vo STM-1, ngoi 164 byte b sung, phn t C-4 cn b sung thm 9 byte VC-4 thnh VC-4. Nh vy, lc ny VC-4 s c 261 ct v 9 hng cha 2349 byte v chuyn n AU-4. Phn t AU-4 b sung thm 9 byte con tr AU-4 PTR vo vng A. Phn t STM-1 tip nhn 2358 byte do AU-4 chuyn n v b sung thm 72 byte SOH to thnh tn hiu STM-1 c 270 ct v 9 hng.SP XP 3 TN HIU 34MBIT/S VO KHUNG STM-1 Sp xp tn hiu 34Mbit/s vo C-3Trc khi a vo module chuyn ti ng b STM-1, lung s cn ng b 34Mbit/s phi c a vo container C-3.

Hnh 22: Sp xp tn hiu 34Mbit/s vo C-3Ti trng C-3 gm 9 hng v 84 ct (9x84=756 byte), lung PDH 34Mbit/s c 34368 Kbit/s : 8000Hz = 4296 bit (537 byte) chim cha y 1 container C-3/

Hnh 23: Ti trng khung C-3Phn t C-3 c d ln l truyn thm lung PDH 44,736 Mbit/s ca chun ANSI:44,736 Mbit/s : 8000Hz= 5593 bitTrng ti STM-1 l 18720 bit nn ch truyn c 3 lung 34 Mbit/s.Trong qung thi gian 125s, C-3 tip nhn 537 byte lung PDH v b sung thm 39 byte (cc bit chn c nh, cc bit chn, cc bit iu khin chn, cc bit mo u OH, cc bit ng b). Sp xp 3 tn hiu C-3 vo VC-4Trc khi a 3xC-3 vo STM-1, mi phn t C-3 b sung thm 9 byte VC-3 POH thnh VC-3. Nh vy, khung tn hiu 125s ca VC-3 s c 85 ct v 9 hng cha 765 byte.Phn t TU-3 tip nhn 756 byte v b sung them 3 byte con tr TU-3 PTR. Bn cnh TU-3 cn chn thm 6 byte c nh to thnh khi TUG-3 (c kch thc 9x86).Nh vy, a TUG-3 vo C-4 cn a thm 2 ct cc byte chn c nh m bo tc nh mc. Sp xp tn hiu C-4 vo STM-1Thc hin nh mc 1.2

Hnh 24: Sp xp 3x34 Mbitps vo STM-1CON TR SDHNHIM V CON TRCon tr c s dng tm cc phn khc nhau ca AU v TU gi l container o VC. Con tr AU xc nh VC bc cao hn v con tr TU xc nh VC bc thp hn. V d AU-3 gm VC-3 cng vi mt con tr, TU-2 gm VC-2 cng vi mt 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 , sau khi din gii con tr mt cch thch hp th c kh nng truy nhp ti tng knh ca ngi s dng c lp bt k thi im no, m khng cn tch lung STM-1.MO U TRONG SDHTrong chun SDH cc chc nng chuyn ti v mo u cng khc nhau cc lp khc nhau. C cc lp nh sau: on ti sinh ( on lp) on ghp knh ( on ghp) Tuyn

Hnh 25: on lp, on ghp v tuyn truyn dn trong SDHMO U ON TI SINH

Hnh 26: RSOH STM-1Mo u on lp RSOH (regenerator section overhead) ch cha cc thng tin phc v yu cu ca cc phn t trn hai u on lp .RSOH chim 3 hng u ca cc ct t 1-9 trong cu trc khung STM-1.Cc byte trng () l d tr quc gia v quc t.Cc byte A1,A2 ng b khung, 6 byte ny c cu trc c nh c cu trc nh phn: A1 (11110110), A2 (00101000). Khi ghp cc STM-1 thnh STM-N cc byte ny u c mt trong cu trc ca n.Byte C1: nhn dng khung STM-1. Byte ny mang s th t c khung STM-1 trong STM-N.Byte B1 : gim st bit li trong tng on lp. byte B1 l t m 8 bit c trng s chn v k hiu l BIP-8.Byte E1 dng cho knh thoi nghip v, khi ghp nhiu khung STM-1 to STM-N, byte ny ch c trong STM-1 th nht ( mi STM-N ch c 2 knh thoi nghip v).Byte F1 knh ca ngi s dng, byte ny ch c mt trong khung STM-1 th nht, dng cho ngi iu hnh mng.Cc byte D1-D3: s dng truyn s liu gia cc trm lp.MO U ON GHP KNH MSOH

Hnh 27: MSOH STM-1Mo u on ghp MSOH (Multiplex Section Overhead) ch cha cc thng tin phc v theo yu cu ca cc phn t ghp knh u cui trn 2 u ca on ghp .MSOH chim 5 hng cui ca cc ct 1-9. Trong cu trc khung STM-1. Chc nng ca cc byte trong MSOH.Cc byte trng () l d tr quc gia v quc tCc byte B2 : gim st bit li ca mt on ghp, byte ny hp thnh t m 24 bit v k hiu BIP-24.Cc byte K1, K2 dng cho knh chuyn mch t ngCc byte D4-D12: s dng truyn s liu vi tc 576kbit/s gia cc trm ghp knh, s dng truyn tin cho cng tc bo tr v qun tr mng. cc byte ny ch c nh ngha cho STM-1 th nht trong STM-N.Cc byte Z1, Z2: cc byte d tr c trong tt c c khung STM-1 ca khung STM-N.Byte E2: dng cho knh thoi nghip v gia cc trm ghp knh, khi ghp nhiu khung STM-1 to STM-N,byte ny ch c trong STM-1 th nht (mi STM-N ch c 2 knh thoi nghip v).MO U TUYN POH CP CAO (VC-4/VC-3)Mo u tuyn c gn vo container v c chuyn cng vi container t khi container o VC c to ra cho n khi ti trng c phn knh ti u cui cng ca tuyn.

Hnh 28: POH CP CAO (VC-4/VC-3)

POH chim hng 1-9 ca ct u tin trong VC-4 hoc VC-3. Chc nng ca cc byte trong POH nh sau:Byte J1: byte nh tuyn, byte ny mang thng tin iu khin thay i im ni kt cui ca tuyn VC-n (n=3,4).Byte B3: gim st li ca tuyn ni gia 2 VC-3 hoc VC-4, n c k hiu l BIP-8. y l t m 8 bit, cc bit c hnh thnh theo quy tc m bit ca cc byte trong container hoc TUG-2 trc nhn gi tr 0 hoc 1 trong t m BIP-8 ca VC-3 hoc VC-4 hin ti, sao cho trng s ca t m l chn.Byte C2: nhn tn hiu , byte ny ch r ti trng ca VC-n ( n= 3,4). Hin ti ch dng 2 trong 256 gi tr ca C2. Gi tr (C2=00000000) ch th VC-21; VC-32 hoc VC-4 khng tham gia. Gi tr 1: (C2=00000001) ch th VC-31;VC-32 hoc VC-4 tham gia.Byte G1: ch th trng thi ca tuyn, byte ny mang thng tin v trng thi ca tn hiu thu v gi thng tin ny tr li cho pha my pht.Byte F2: knh ca ngi s dng tuyn, byte ny cung cp knh truyn s liu cho ngi s dng tuyn.Byte H4: Ch th a khung.Byte Z3-Z5: cc byte d tr.MO U TUYN POH CP THP (VC-2/VC-1)

Hnh 29: Cu trc POH cp thpTi trng cc container o VC-1 v VC-2 khng cu trc ring cho tng khung, m c cu trc thnh mt a khung (gm 4 khung). Cc byte V2, J5, N2 v K4 c t trong POH ca VC-2/VC-1. Chc nng c th ca cc byte nh sau:Byte ng u a khung chnh l VC-1 POH hoc VC-2 POH c k hiu l V5Byte V5 c dng khi cc byte trong ti trng VC-1 (hoc VC-2) c s x dch (tri), bnh thng V5 l byte n c nh.

Hnh 30: Cu trc byte V5Bit 1 v 2 hnh thnh t m BIP-2 gim st li bit. Bit 1 c hnh thnh do kt qu m bit l (1, 3, 5, 7) ca cc byte VC-1, VC-2 trc , nu trong s m cc bt l l chn s c gi tr. S hnh thnh bit 2 cng tng t, nh vo vic m cc bit chn (2, 4, 6, 8). T m BIP-2 c t vo v tr u tin ca VC-1 hoc VC-2 hin ti.Bit th 3 (FFBE): s dng ch th li khi u xa cu tuyn, bit ny bng 0 l khng li, bng 1 c li.Bit th 4: khng s dng.Bit th 5, 6, 7 (L1, L2, L3): l nhn tn hiu ca VC-1 hoc VC-2. Ba bit ny nhn 8 gi tr (000, 001,, 111) nhng ch s dng hai gi tr u l L1L2L3 = 000 ch th tuyn VC-1, VC-2 c mt; L1L2L3 =111 ch th tuyn VC-1, VC-2 khng c mt.Bit th 8: bit cnh bo t xa ca tuyn, mang gi tr 1 ch th bo cnh tuyn (AIS) hoc mt tnh hiu thu, mang gi tr 0 l bnh thng.NG B MNGMC CH NG Bng b l phng thc gi cho cc thit b s trn mng hot ng theo cng mt tc trung bnh trn tt c cc giao din. Nu tc ng vo v tc ng ra khng bng nhau th mt phn thng tin s b mt, do vn ng b l cha kho quan trng t c cht lng dch v nh mong mun.ng b mt tuyn s c thc hin nh tch thng tin t lung s thu, cn phi nhn dng chnh xc mi khe thi gian n. khng vn g tn ti nu khng c s c lm li lung bit. Tuy nhin, cng c lc lung bit c li v lm mt t m ng b khung. Vic khi phc ng b khung c thc hin mt cch t ng trong h thng PDH th mi mt cp ghp khi to thnh cc khung cp 1, cp 2, cp 3, cp 4 v cp 5 u c t ng b khung.Do vic thit lp mt tn s nh thi thng nht cho ton b h thng s c lp hn so vi cc lung bit thu, cung cp nh thi gia cc thit b u cui trong mng v khng cn bit cc lung bit ny n t cc lung khc nhau c c ly t ng b hay khng ? iu s tt hn nu b tr truyn dn gia cc trung tm chuyn mch hoc cc thit b u cui cc mng c ng b cc dng sau: nh thi c iu khin nh ng h chun ring hoc ng h ch. Mng bao gm mt nhm cc phn mng m nh thi ca mi phn mng c iu khin nh mt ng h chun nhng hot ng d b gia cc phn mng. Mng c th l d b hon ton nu nh thi ca mi nt c iu khin bi mt ng h chun ring bit.CC PHNG PHP NG B ng b cng bcng b cng bc hoc ng b ch/t l loi ng b m tn s ch duy nht c thit lp cho ton mng nh hot ng ca mt ng h ch mng v mi t khc u ph thuc vo n,s ph thuc din ra theo cu trc nt, trong cc ng h nt c kha t ng h ch ln lt t mnh tr thnh ng h ch.cc b to dao ng thch anh iu khin nhit c n nh cao c s dng lm ng h chun cc nt khi kha pha vi ch mng. ng b c lpPhng php ng b c lp l cung cp cho mi nt trong mang mt ng h chun c chnh xc v n nh cao. Phng php ny c nhc im l xut hin trt do s khc nhau ca cc ng h ca cc nt hoc do s chn bit trn cc lung s gy ra. ng b tng hPhng php ng b ny nhm to mt ng h thng nht cho ton mng quc gia nh hot ng tng h ca cc b dao ng tinh th iu khin nhit c n nh nh s dng b kha pha nhiu u vo, cc b dao ng ny t cc nt mng v c cp ngun t mt trong cc nt chuyn mch khc ni n n.

KT LUNU IM CA H THNG SDHTrong PDH vic ghp knh c tin hnh ti mi cp, qu trnh ghp phi ln lt qua cc mc trung gian t 2 n 140 Mb/s. Vic truy cp trc tip n mt lung 2Mbit/s trong mt lung 140 Mb/s l khng th thc hin c. Chng hn nh khi cn ni cho cc lung 2 Mb/s th phi thc hin h knh t lung 140 Mb/s qua nhiu cp xung n 2 Mb/s ri mi dng cp nhy thc hin ni cho. Mng li ny rt cng knh v phc tp v khng linh hot ng thi chi ph vn hnh rt ln do i hi nhiu sc lao ng trong cc khu lp t chuyn cp...i vi SDH th u im ni bt hn l n gin ho mng li, linh hot trong s dng khai thc. Khc vi PDH, trong mng SDH qu trnh ghp knh ch thc hin qua mt giai on, do vic tch mt knh 2Mbit/s trong mt lung tc cao l n gin. Hn na, vic s dng phn mm trong qun l bo dng lung 2 Mbit/s lm cho vic u cho cc lung 2 Mbit/s tr nn thc s n gin v nhanh chng. Chnh v th vic vn hnh v qun l mng li n gin hn nhiu so vi cng cng vic ny mng PDH.Trong SDH tc bit ln hn 140 Mbit/s ln u tin c tiu chun ho trn phm vi ton th gii.M2 truyn dn ca tn hiu quang c tiu chun ho tng thch cc thit b ca cc nh sn xut.C cu trc khi :Tc bit v cu trc khung ca cp cao hn c to thnh t tc bit v cu trc khung ca lung c bn cp thp hn do vic tch ghp lung thng tin d dng.C cc knh ring cho gim st, qun l, o th hoc iu khin trong phn mng qun l.Tt c cc tn hiu PDH c tc thp hn 140 Mbit/s u c th ghp c vo cp SDH thp nht l STM - 1 c tc 155 Mbit/s.NHC IM CA SDHK thut phc tp hn do phi ghi li s tng quan v phase gia cc tn hiu lung v overhead.Vic nhi byte - byte tng Jitter hn kiu bit - bit ca PDH.ng h phi cung cp t ngoi.Truyn d tha v thiu mc 8 Mb/s.

TI LIU THAM KHO1. Marconi, SDH Synchronous Digital Hierarchy2. Hc vin Cng ngh Bu chnh Vin thng, K thut thng tin quang 2 (Dng cho sinh vin h o to i hc t xa)3. B t lnh thng tin lin lc, Trung tm K thut Thng tin cng ngh cao, K thut thng tin quang v SDH 4. Neotelis, PDH & SDH Digital TransmissionMng th h mi NGN3DHDT7BLT - Nhm 1

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