cong nghe ftth

7/30/2019 Cong Nghe FTTH

1/39

TIU LUN

CNG NGH CP QUANG THU BAO FTTH

Chng 1 : Gii thiu cng ngh cp quang thu bao FTTH

Cng ngh cp quang thu bao FTTH (Fiber-To-The-Home) l mng vin

thng bng thng rng bng cp quang c ni n tn nh cung cp cc dch v

tc cao nh in thoi, Internet tc cao v TV.

Ngun: Cc ti liu v PON trn Vntelecom.org

Hnh 1.1: M hnh mng FTTH

Hin nay, cng ngh FTTH (Fiber-To-The-Home) ang c trin khai. Khi

dng cng ngh FTTH, ng truyn dn hon ton bng cp quang ti tn phng my

ca ngi s dng. Cht lng truyn dn tn hiu bn b ,n nh khng b suy hao tn

hiu bi nhiu in t, thi tit hay chiu di cp nh i vi ADSL v bo mt rt

cao. Vi ADSL, kh nng bo mt thp hn v c th b nh cp tn hiu trn ngdy, cn vi FTTH th hu nh khng th b nh cp. Vi cng ngh FTTH, nh cung

cp dch v c th cung cp tc download ln n 10 Gigabit/giy, nhanh gp 200

ln so vi ADSL 2+ (hin ch c th p ng 20 Megabit/giy). Tc truyn dn vi

ADSL khng cn bng, c tc ti ln lun nh hn tc ti xung v ti a 20

Mbps. Cn FTTH cho php cn bng, tc ti ln v ti xung nh nhau v cho php

ti a l 10 Gbps, c th phc v cng mt lc cho hng trm my tnh.

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FTTH c bit hiu qa vi cc dch v: Hosting Server ring, VPN (mng

ring o), Truyn d liu, Game Online, IPTV (truyn hnh tng tc), VoD (xem phim

theo yu cu), Video Conferrence (hi ngh truyn hnh), IP Camera. Vi u th bng

thng truyn ti d liu cao, c th nng cp ln bng thng ln ti 1Gbps, An ton dliu, n nh cao, khng b nh hng bi nhiu in, t trng. Bo co mi nht

ca Heavy Reading, s h gia nh s dng kt ni bng rng FTTH trn ton th gii

s tng trng hng nm trn mnh m trn th gii. 30% cho n nm 2012 v t 89

triu h khi . Hin Nht Bn, Trung Quc v M l cc quc gia i u trong lnh vc

bng thng rng s dng cng ngh cp quang ny. Cng ngh FTTH c khong 20

triu kt ni ton cu, ch tnh ring 3 nc Nht Bn, Trung Quc v M c thm

khong 6 triu thu bao, trong chu c nh gi l th trng c tim nng phttrin ln. Theo d on, vo cui nm 2012, ring chu s c 54 triu kt ni FTTH,

tip theo l chu u/ khu vc Trung ng/ chu Phi vi 16 triu, ri n Bc M v

Nam M vi 15 triu. Hin nay, qu trnh chuyn i sang FTTH ang c thc hin

nhiu nc, gm an Mch, Php, Hng Kng, Nht Bn, Hn Quc, Thy in, i

Loan v M.

M hnh trin khai mng FTTH

` Hin nay, cng ngh FTTH (Fiber-To-The-Home l mng vin thng bng

thng rng bng cp quang c ni n tn nh cung cp cc dch v tc cao

nh in thoi, Internet tc cao v TV) ang c trin khai kh mnh m trn th

gii.

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Ngun: Ti liu v FTTX ca cng ty CMC-IT

Hnh 1.2: M hnh trin khai mng FTTH

Ti nc ta, FTTH cng c FPT Telecom trin khai ti mt s thnh ph

ln. M hnh trin khai c th hin nh Hnh 1.2. Tiu chun ny cn c gi bng

tn khc l FTTB (Fiber To The Building), khc vi FTTC (Fiber To The Curb) -

ng dn cp n bn ngoi ng thi, cn dn vo nh vn l tiu chun dy ng

nh c.Tc i Internet cam kt ti thiu ca Fiber to the x >= 256 Kbps, ln hn tc

i Internet ca tt c cc gi ADSL. Vi ADSL, chiu di cp ti a cn 2,5 Km

t s n nh cn thit, cn vi FTTH th con s ny ln ti 10 km.

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D kin FTTH s dn thay th ADSL trong tng lai gn mt khi bng thng

ADSL khng sc cung cp ng thi cc dch v trc tuyn trong cng mt thi

im.

Chng 2: MT S M HNH PON C TRIN KHAI TRONG MNG

FTTH

I. ATM trn nn PON ATM PON (APON)

1 M hnh tham chiu APON

H thng bao gm OLT, ONU, cp quang s dng cu hnh PON trong c

mt b chia quang th ng. Cc ONU chia s chung dung lng ca mt si quang,khi s dng b chia, vn ta cn c bit quan tm l s bo mt. ng ln, cn

phi s dng giao thc mt phng thc a truy nhp.

Ngun: Cng ngh truy nhp trong mng NGN-HVCNBCVT

Hnh 2.1: Cu hnh tham chiu APON

Mng phn phi quang ODN cung cp 1 hoc nhiu hn cc ng dn quang t OLT

n mt hoc nhiu hn cc ONU. Mi ng dn quang c nh ngha gia im

tham chiu S v R trong 1 ca s bc sng nht nh. Hai hng truyn dn trong

ODN c nh ngha nh sau:

ng xung cho tn hiu t OLT n ONU.

ng ln cho tn hiu t ONU n OLT.Giao din ti hai im tham chiu S, R (c gi chung l IFPON) h tr tt c

cc thnh phn giao thc cn thit cho php truyn dn gia OLT v ONU.

ONU c th c mt chc nng thch ng cho truyn dn ng dy thu bao s

DSL qua cp ng n nh thu bao. OAM c qun l thng qua giao din qun tr

Q3

2 Cc c t cho APON

4

Q3

ODN

ONU

ONU

R/S

IFPON

S/R

IFPON

Node

dchv

SNI

UNI

Chc nng qun l h thng mng truy nhp

OLT

AF


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APON l s kt hp gia phng thc truyn ti khng ng b ATM vi

mng truy nhp quang th ng PON.

Mng APON s dng cng ngh ATM l giao thc truyn tin. Cng ngh ATM

cung cp s mm do theo khi nim trong sut dch v v phn b bng tn,ngoi racn c nhng tnh nng rt hu ch cho hot ng khai thc v bo dng cc kt ni t

u cui n u cui nh gim c chi ph hot ng ca mng. Cc u im ca

ATM c kt hp vi mi trng truyn dn l si quang vi ti nguyn bng tn

dng nh l v hn to ra mt mng truy nhp bng rng c bit ti nh l

BPON (Broadband PON - mng PON bng rng). Nh mi h thng khc, APON cng

c chia thnh cc lp, lp con vi cc nhim v c th. Cc lp ny thuc mt trong

hai mt bng:Mt l mt bng d liu c nhim v phn phi lu lng n v i t cc thit

b u cui, trong trng hp ny l cc cng ti OLT v ONU.

Hai l mt bng iu khin, hay mt bng OAM hay h thng h tr hot ng

(OSS), thc hin cc chc nng vn hnh, iu khin, qun l. Nhng chc nng ny c

tnh cht khng lin tc, v d nh l cc chc nng OAM: khi to, khi phc li, bo

co trng thi, vi trng hp mng quang c cc chc nng ring bit nh iu chnh

cng sut laser.

Thng tin iu khin cha trong cc trng tiu , tiu con, hay cc phn

thng tin mo u trc lu lng ngi dng. Phi ni rng, thng tin tiu thuc v

mt lp s khng c nhn thy bi cc lp trn ti c pha gi v pha nhn. Miu

t cu trc ng php cc bn tin bng cch lit k tng bit, tng byte trong nh dng

bn tin. Thc t, ch cn xem bn tin ca mt lp ni g, nghe g ta c th hon ton bit

chc nng ca giao thc lp .Hot ng ca APON cng s c cp thng qua vic m t qu trnh trao

i bn tin gia cc thc th ngang hng theo thi gian, vic trao i cc lnh v cc

p ng gia cc lp lin k theo chiu dc trong ngn xp giao thc.

3 Cu trc phn lp APON

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M hnh phn lp mng ATM gm c lp mi trng truyn dn v lp ng,

lp mi trng truyn dn phn chia thnh lp mi trng vt l v lp hi t truyn

dn.

Trong mng ATM-PON lp ng tng ng vi lp ng o ca lp ATMLp di cng l lp phng tin vt l thc hin giao tip vi phn quang ca mng

(hay chnh l mng phn phi quang ODN). Lp ny thc hin cc chc nng: chuyn

i in-quang, nhn/truyn cc tn hiu n/i phng tin vt l ti mt trong ba

bc sng quang (1310, 1490, 1550nm), kt ni vi si quang ca ODN. Cu trc ca

lp tun theo tp cc tham s quang in c chun ha.

Gia lp phng tin vt l v lp ng (giao in m qua t bo ATM

c phn phi ti lp khch hng) l lp hi t truyn dn TC (tng ng vi lp 2trong m hnh OSI). Lp TC c phn chia thnh lp con truyn dn PON v lp con

thch ng nm trn, tng ng vi lp con hi t truyn dn ca m hnh B-ISDN.

Lp con thch ng c chun ha da trn chun ATM trn c s cp ng truyn

thng. Chc nng ca lp ny l chuyn i gia khung 125s mc ngi dng (n v

d liu giao thc PDU) v t bo ATM.

3.1 Lp vt lLp ny khng ging nh cc lp trn l cc thnh phn phn cng ch khng

phi l phn mm. Phn cng ny c nh ngha bi cc chun [G.983.1 & G.983.3]

v tun theo cc tham s sau:

Tc bit: 155.52 hoc 622.08Mb/s ng xung v 155.52Mb/s ng ln

Bc sng: 1260 n 1360nm ng ln, 1480 n 1580nm ng xung

Dng lu lng: s c hai hng, h tr tng t ng xung

T l chia cng sut quang: ln n 32, con s ny b gii hn bi suy hao ODN.

Lp ng Chuyn i t bo ATM v cc khung

d liu ngi dngLp

Mi

Lp

hi

Lp con Thch

ng

Lp thch ng ca B-ISDN

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trng

truyn

dn

t

truyn

dn Lp con truyn

dn PON

-Xp xp

-Cp pht khe t bo

-Cp pht bng tn

-Bo mt v an ton-ng chnh khung

-ng b cm(Burst)

-ng b bit/byteLp vt l -Tng thch E/O

-Ghp bc sng

-Kt ni si quang

Ngun: Cng ngh truy nhp trong mng NGN-HVCNBCVTHnh 2.2: Cu trc phn lp mng APON

3.2 Lp hi t truyn dn

Lp con hi t truyn dn bao gm lp con truyn dn PON v lp con thch

ng c th hin nh sau:

Lp con truyn dn PON hon ton lm vic vi t bo. Theo hng v, lp

ny nhn cc t bo t tn hiu in do lp phng tin vt l a n, ng b ti mcbit v byte, gii hn t bo v khung c xc nh, mo u c tch v x l,

chuyn cc lung t bo ln lp cao hn tip theo. Theo hng i, qu trnh x l din

ra ngc li. Trong lp ny, giao thc sp xp c s dng m bo rng cc t bo

n t cc ONU khc nhau khng chng lp ln nhau.

Lp con thch ng: y l lp trong c s chuyn i din ra gia t bo

ATM v PDU (c th l: SONET/SDH, xDSL, cc PDU da trn khung 125s) Lp

ny khng cung cp giao din vi cc lu lng trn c s gi nh Ethernet hay IP.

cung cp nhng giao din ny ta phi c 1 phn mm chuyn i thm vo, phn ny

khng trong phm vi chun.

4 Khung truyn dn APON/BPON

ITU-T G.983.1 nh r kin trc tham chiu, c im ca b thu pht, cu trc khung

truyn ti v cc chc nng sp xp trong APON/BPON. Tn hiu APON/BPON c

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truyn trong khe thi gian. Mi khe thi gian cha mt cell ATM hay mt cell hot

ng, qun l v bo dng lp vt l (PLOAM - Physical LayerOperation,

Administration and Maintenance). Cell PLOAM c dng truyn thng tin qun l

ca lp vt l nh l cc bn tin giao thc dng cho vic sp xp, trn kha vi d liuv cp nht. Cc khe thi gian hng xung l cc cell ATM v PLOAM c di mi

cell l 53 byte. Mt cell PLOAM c chn vo c mi 28 khe thi gian (hay 27 cell

ATM). tc 155.52Mbps, APON/BPON quy nh khung xung c 54 cell ATM l

truyn d liu nh vy tc xung thc s l: 54/56 155.52 Mbps = 149.97 Mbps

V 2 cell PLOAM dnh cho ng b, iu khin li, bo mt, bo dng v phn phi

bng thng. Khung ln c 53 khe nh vy khung ln thc s tc d 155.52 Mbps l:

53/56 155.52 Mbps = 147.19 Mbps, v mi khe ln c chia thnh nhiu khe con,mi khe con cha 3 byte overhead t trc cell ATM v PLOAM. Bn cnh , mi

khe hng ln c th c chia thnh nhiu khe nh. Hnh 2.3 (a,c) m t khung xung

v ln ca APON/BPON ti 155.52 Mbps. Cu trc khung ti 622.08 Mbps v 1244.16

Mbps th tng t ngoi tr s khe thi gian trn khung tng ln ln lt 4 v 8 ln. Cu

trc PLOAM hng xung m t Hnh 2.3 (b) n gm cc phn sau:

1 5 byte header c th c m t nh bng 3.1.

2 Bng 3.1: nm byte header

Vng IDENT c nm v tr u tin trong PLOAM hng xung

1 K tip l 2 byte ng b.2 PLOAM c 27 grant, c mi 6-7 grant th c kim tra CRC.

3 MSG_PON_ID nh a ch cho mi ONU. Trong th tc sp xp ONU c

gn s nhn dng PON_ID. S nhn dng ny c gi tr t 0 n 63.

4 MSG_ID m t loi bn tin.

5 MESSAGE_FIELD cha bn tin cnh bo, x l cc bn tin nhn c ONU

lin quan n th tc sp xp.

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6 BIP8 (bit-interleaved parity) c 8 bit, cho php ONU kim tra tc li bit

BER. Mi bit ca BIP8 s XOR vi tt c bit cng v tr trong mt byte. ONU s so

snh BIP8 nhn c vi BIP8 c tnh trn lung nhn c, mi bit khng ging s

c tnh ton.

Ngun: ITU-T Recommendation G.983.1, Broadband optical access systems based

on

Passive Optical Networks (PON), 2005.

Hnh 2.3: Cu trc khung hng xung v ln ca APON

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Vic truyn cell ATM, cell PLOAM hng ln c iu khin bi OLT

thng qua cell PLOAM truyn hng xung.Chun G.983 yu cu ti thiu c mi

100 ms c mt cell PLOAM trn mt ONU. Ngoi ra 3 byte u hng ln cha thi

gian ngh, li m u v ranh gii bt u cell.APON/BPON ch nh thi gian ngh ti thiu l 4 bit. N cung cp thi gian

ngh gia 2 cell hay khe con lin k trnh ng . Li m u ly pha ca cell n

hay khe con ng b bit v khi phc bin . Ranh gii l phn ch nh bt u

cell ATM hay khe con, m c th c dng thc hin ng b byte.

1 Hnh 2.3(a) m t khun dng khung hng xung tc 155 Mbps, Hnh

2.3(b) m t khun dng bn tin PLOAM hng xung, Hnh 2.3(c) m t khun dng

ca bn tin hng ln, Hnh 2.3(d) m t khun dng bn tin PLOAM hng ln.

Khun dng cell PLOAM ln c m t hnh 2.3(d) bao gm cc phn sau:

Ging nh khung hng xung n cng c 5 byte header v 1 byte IDENT bt

u khung hng ln. MSG_PON_ID v MSG_ID phc v cho vic nhn dng ONU.

Byte CRC truyn cnh bo cc thng tin hot ng, qun l v bo dng t ONU. K

l 17 byte iu khin ngun laser: s dng cho ONU bo co cc mc cng sut

cho mi ngun laser ca ONU chng c th duy tr gi tr thch hp. Tip theo l 16byte iu khin b thu c dng b thu ca OLT hiu chnh mc ngng cho vic

pht hin mc 0 v mc 1. Cui cng, BIP cng c chc nng tng t nh khung

hng xung

II. Broadband PON ( BPON )

Lch s pht trin ca BPON:

Nm 1997: Pht trin BPON da trn nn tng ATM leased-line.

Nm 1999: Gii thiu cc thit b u cui (End-User) cho FTTB ti M.

Nm 2000: Pht trin thit b u cui cho khu dn c v cc module quang

cc ONT nhn bit v tch d liu ng xung ca mnh da vo VCI/VPI ca ATM

cell.

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Hnh 2.4: M hnh BPON

Lung xung :Bng tn c bn 1,4801,500

Lung ln:

Bng tn c bn :1,260-1,360

Hnh 2.4 ch ra kin trc ca BPON (Broadband PON). Trong kin trc ny,

OLT kt ni n ONU qua b chia 1:N. Khong cch truyn dn ti a l 10-20 km.

Lu lng hng ln t ONU c truyn bc sng 1310 nm v hng xung t

OLT l bc sng 1490 nm v bc sng 1550 nm c dng ti hnh nh. D liu

hng xung s truyn tt c cc gi d liu n tt c ONU v n s nhn gi m ng

a ch ca n cn hng ln th cc gi t cc ONU s truyn ln lt cc gi n

OLT thng qua s iu khin ca OLT. OLT s qui nh khe thi gian m ONU no

c truyn ti thi im c th trnh c s ng .

Trong thit b, OLT thng c to thnh line card v c ghp vo trong b

khung v kt ni n mng li/metro. Cn ONU th c mt hay nhiu cng dnh cho kt

ni thoi (T1/E1) v data (10/100BASE-T Ethernet) n khch hng.

Mng quang th ng bng rng B-PON c chun ha trong chui cc

khuyn ngh G.938 ca ITU-T. Cc khuyn ngh ny a ra cc tiu chun v cc khi

chc nng ONT v OLT, khun dng v tc khung ca lung d liu hng ln v

hng xung, giao thc truy nhp hng ln TDMA, cc giao tip vt l, cc giao tip

qun l v iu khin ONT/ONU v DBA.

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Trong mng B-PON, d liu c ng khung theo cu trc ca cc t bo ATM. Mt

khung hng xung c tc 155Mbit/s (56 t bo ATM c khch thc 53byte), hoc

622 Mbit/s (4*56 t bo ATM) v mt t bo qun l vn hnh bo dng lp vt l

(PLOAM Physical layer Operation Administration and Maintenance) c chn voc mi 28 t bo trong knh.

PLOAM c mt bt nhn dng cc t bo PLOAM. Ngoi ra cc t bo

PLOAM c kh nng lp trnh c v cha thng tin nh l bng thng hng ln v

cc bn tin vn hnh qun l v bo dng OAM.

Ngun: CEDRIC F. LAM , Passive Optical Networks Principles and Practice,

October 2007.

Hnh 2.5: Kin trc h thng BPONCn c vo cc thng tin v m s nhn dng knh o v nhn dng ng o

(VPI/VCI) trong cu trc ATM, cc ONT nhn bit v tch d liu ng xung ca

mnh.

Cu trc khung hng ln bao gm 56 t bo ATM (53 byte). Mi mt knh

gm c mt t bo ATM/PLOAM v 24 bt t mo u. T mo u mang thng tin v

thi gian bo v, mo u cho php ng b v khi phc tn hiu ti OLT, v thng tin

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nhn dng im kt thc ca t mo u. Chiu di ca t mo u v cc thng tin

cha trong c lp trnh bi OLT. Cc ONT thc hin gi cc t bo PLOAM khi

chng nhn c yu cu t OLT.

B-PON s dng giao thc gn bng thng ng DBA cho php OLT nhnbit lng bng thng cn thit cp cho cc ONT/ONU. OLT c th gim hoc tng

bng thng cho cc ONT/ONU da vo gi cc t bo ATM ri hoc lm y tt c

hng ln bi d liu ca ONT/ONU.

OLT dng nh k vic truyn hng ln do vy n c kh nng mi bt k

ONT/ONU mi no tham gia vo hot ng h thng. Cc ONT/ONU mi pht mt

bn tin phc hi trong ca s ny vi thi gian tr ngu nhin trnh xung t khi m

c nhiu ONT/ONU mi mun tham gia.OLT xc nh khong cch ti mi ONT/ONU mi bng vic gi ti

ONT/ONU mt bn tin o c ly v xc nh thi gian bao lu thu c bn tin phc

hi. Sau OLT gi ti ONT/ONU mt gi tr tr, gi tr ny c s dng xc nh

thi gian bo v ng vi cc ONT/ONU.

III. Gigabit PON (GPON)

1 H thng GPON

G-PON l giao thc FSAN TDMA PON th 2 c nh ngha trong chui

khuyn ngh G.984 ca ITU-T. G-PON c xy dng trn tri nghim ca B-PON v

E-PON.

GPON vit tt ca t Gigabit Passive Optical Network. GPON l s pht trin

ca APON/BPON n hot ng tc ln ti hng Gbps v c chun ha thnh

ITU-T G.984. GPON khng ph thuc vo ATM, GPON s dng lp con truyn dn

hi t (GTC- GPON Transmission Convergence), khung GTC c th ng gi cc cell

ATM. Khng ging nh APON/BPON, khung GTC c th ng gi trc tip cc gi d

liu thng qua phng php ng gi GPON (GEM- GPON Encapsulation Method).

Phn ti khung GTC cha c ATM v GEM.

Mc d G-PON h tr truyn ti tin ATM, nhng n cng a vo mt c ch

thch nghi ti tin mi m c ti u ha cho truyn ti cc khung Ethernet c gi l13


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phng thc ng gi G-PON (G-PON Encapsulation Method - GEM). GEM l

phng thc da trn th tc ng khung chung trong khuyn ngh G.701, ngoi tr

vic GEM ti u ha t mo u phc v cho ng dng ca PON, cho php sp xp

cc d liu Ethernet vo ti tin GEM v h tr sp xp TDM.G-PON s dng cu trc khung GTC (G-PON Transmission Conversion) cho

c hai hng xung v hng ln. Khung hng xung bt u vi mt t mo u

PLOAM, tip sau l vng ti tin GEM hoc cc t bo ATM.

PLOAM gm c thng tin cu trc khung v sp t bng thng cho ONT/ONU

gi d liu trong khung hng ln tip theo.

Khung hng ln bao gm cc nhm khung gi t cc ONT. Mi mt nhm

c bt u vi t mo u lp vt l m c chc nng tng t trong B-PON, nhngcng bao hm tng hp cc yu cu bng thng ca cc ONT. Cc yu cu bng thng

chi tit hn c gi i km vi cc nhm hng ln khi c yu cu t OLT.

OLT gn cc thi gian cho vic gi d liu hng ln t cho mi ONT/ONU.

Ti u ha cho truyn ti cc khung Ethernet bng phng thc GEM (GPON

encapsulation method).

S dng cu trc khung GTC (GPON tranmission coversion) cho c hai hng

ln v xung.

Hnh 2.6: Lp con truyn dn hi t

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2 Lp truyn dn hi t GPON

2.1 Chc nng ca GTC

Chc nng chnh ca lp truyn dn hi t GPON (GTC- GPON Transmission

Convergence) l cung cp ghp knh vn chuyn gia OLT v ONU. Cc chc nng

khc bao gm:

Thch nghi vi giao thc tn hiu lp con, cc chc nng hot ng, qun l v

bo dng lp vt l PLOAM, giao din phn phi bng tn ng, sp xp v ng k

ONU, sa li (mc nh), mt m lung d liu hng xung (mc nh) v knh thng

tin cho giao din qun l v iu khin ONT/ONU.

1 H thng GTC cung cp iu khin a truy nhp cho lu lng hng ln.Trong khi nim c bn, cc khung hng xung ch th vng c php truyn lu

lng ln trong khung hng ln ng b vi khung hng xung.


on Passive Optical Networks (PON), 2005.

Hnh 2.7 : Khi nim iu khin a truy nhp GPON

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Khi nim iu khin a truy nhp GPON c m t Hnh 2.7. OLT gi cc

con tr trong khi iu khin vt l PCBd, cc con tr ny ch th thi gian bt u v

kt thc m mi container truyn dn (T-CONT) c th dng truyn d liu hng

ln. Bng cch ny, ch c mt ONU truy nhp mng ti bt k thi im no khng cs tranh chp trong hot ng bnh thng. Cc con tr c a vo cc khi byte, cho

php OLT iu khin mi trng mng vi tc 64 kbps. Tuy nhin, chun cho php

nh khai thc dch v thm cc tc ln hn.

2.2 Tc bit ca GPON

Khi tc bit tng ln n hng gigabit th cn c b pht cng sut cao v do

dn n l cng cn c b thu c nhy cao hn. iu ny c th c khc phcbng cch s dng c ch cn bng cng sut. C ch cn bng cng sut h tr cho

vic iu chnh cc mc cng sut ca ONU lm gim vng chnh lch cng sut nhn

c OLT. Mt ONU gn OLT th suy hao thp, S khi to nh hn cng sut

ONU xa.

Bng 3.1: Lit k tc bit trong GPON

3 Khung truyn dn GPON

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3.1 Cu trc khung hng xung

Mi khung hng xung GTC di 125 s c tc khung l 1.24416 Gbit/s v

2.48832 Gbit/s, cha khi iu khin vt l (PCBd- downstream Physical Control

Block) v phn ti c m t hnh 2.8.

Header ca khi iu khin vt l bao gm phn c nh v phn c th thay

i. Phn c nh cha vng ng b vt l, vng ID v vng PLOAM. Phn c th thay

i bao gm chiu di ti hng xung (Plend-Payload length downstream) v b nh

bng thng hng ln. Chi tit cc vng c m t Hnh 2.9.


on Passive Optical Networks (PON), 2005.

Hnh 2.8 : Khung hng xung GTC

a. Vng ng b vt l

Vng ng b vt l c c nh l 4 byte v n bt u mi khi PCBd.

ONU s dng phn ny tm v tr bt u khung. ONU thc hin c ch ng b nh

hnh 2.10. ONU bt u trng thi tm kim. ONU tm ra Psync trong hng i. Mi lnn tm ra Psync th n s chuyn thnh pre-sync v thit lp b m ci gi tr l 1. Sau

, ONU s tm Psync khc sau chu k 125 s. C mi Psync ng, b m s tng

thm 1. Nu Psync khng ng, ONU s truyn ngc li trng thi tm kim. Trong

trng thi pre-sync, nu b m truyn ng ti M1 th ONU s truyn n trng thi

ng b sync. Mi ln ONU n trng thi sync, ONU biu th n tm ra cu trc

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khung hng xung v bt u x l thng tin PCBd. Nu ONU pht hin vng Psync

M2 k tip khng ng, n s biu th l mt khung v tr v trng thi tm kim.

b. Vng ID

Vng ID c 32 bit trong mt bit dng kim tra li khung FEC hng

xung, mt bit dnh v 30 bit ch th cu trc khung ln hn. B m siu khung ny

c dng cho h thng m ha d liu ca ngi dng v cng c th c dng

cung cp tn hiu tham chiu ng b tc thp. 30 bit ca vng ID dng m v

mi ID ca khung s ln hn khung trc . Bt c khi no b m tng ti gi tr ti

a th n s quay v 0 cho khung tip theo.

c. Vng qun l, vn hnh v bo dng lp vt l PLOAM

Vng PLOAM c 13 byte trong khi iu khin vt l, n cha cc bn tin

OAM lp vt l. Hot ng, qun l v bo dng OAM lin quan n cc cnh bo gy

ra bi cc s kin c truyn qua cc bn tin trong vng PLOAM 13 byte. Tt c kch

hot u lin quan n bn tin c nh x trong vng PLOAM.

ONU ID nh a ch cho mi ONU ring. Trong lc sp xp, ONU s cgn mt s gi l ONU ID. S ny c gi tr t 0 n 253. Lc cha c sp xp vng

ny c gi tr l 0xFF qung b cho tt c ONU.

1 Bn tin ID ch th loi bn tin.

2 D liu c dng cho phn ti ca bn tin truyn dn hi t GPON GTC.

CRC dng kim tra li khung.

d. Vng BIP

Vng BIP c 8 bit cha s bit chn l c chn vo ca tt c byte truyn i,

u thu cng tnh s bit c chn vo l chn hay l, sau so snh vi kt qu ca

BIP c truyn o s li trn ng link.

e. Vng chiu di ti hng xung

Vng chiu di ti hng xung (Plend) ch nh chiu di b nh bng thng

v phn dnh ring cho ATM trong container truyn dn. Vng ny c gi 2 ln.

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Trong 12 bit u biu din chiu di b nh bng thng. iu ny gii hn s ID

phn b c th c gn ch ln ti 4095. Chiu di phn dnh ring cho ATM c

biu din 12 bit tip theo. iu ny cho php hng ln 4095 cell ATM trong mt

khung v tc ln ti 10 Gbps. 8 bit cui kim tra CRC. u thu ca vng Plend sthc hin pht hin v sa li.

f. Vng b nh bng thng

Vng b nh bng thng l mt mng c cu trc 8 byte. Mi vng trong mng

ny biu th phn bng thng cho mt container truyn dn ring. Ton b s vng

trong b nh c biu din chiu di ti Plend. Khun dng mi vng c m t

Hnh 2.9.


onPassive Optical Networks (PON), 2005.

Hnh 2.9 : M t chi tit khung hng xung GTC

Vng phn b ID cha 12 bit ch th CON-T ring m n c gn thi gian

lung ln ca mng PON. Tip theo l Vng c cha 12 bit ch th cch phn phi

dng (Hnh 2.9 biu din cc chc nng ca 12 bit c) . Tip l Bit 11 gi PLSu

(power levelling sequence upstream): nu bit ny c ci t, ONU s gi thng tin

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PLSu trong lc phn b. Nu khng c ci t th ONU s khng gi thng tin PLSu

trong lc phn b. Bit 10 gi PLOAMu: nu bit ny c ci t, ONU s gi thng tin

PLOAMu trong lc phn b. Nu khng c ci t th ONU s khng gi thng tin

PLOAMu trong lc phn b. Bit 9 s dng sa li FEC (forward error correction): nubit ny c ci t ONU s tnh ton v chn FEC trong lc phn b. Bit 7 v 8 gi

bo co bng thng ng DBRu (Dynamic Bandwidth Report upstream): ph thuc vo

ni dung 2 bit ONU s gi DBRu ph hp vi v tr ID hay khng. V 00: khng gi

DBRu, 01: gi DBRu mode 0 (2 byte), 10: gi DBRu mode 1 (3 byte), 11: gi DBRu

mode 2 (5 byte) cui cng l Bit 0-6: dnh.

Hnh 2.10 : C ch trng thi ng b ONU

Vng StartTime cha 16 bit ch th thi gian bt u phn b. Thi gian ny

tnh bng byte, bt u khung l 0. iu ny gii hn kch thc ca khung ln l

65,536 byte. iu ny nh a ch cho tc hng ln ti 2.488 Gbps. Thi

gian bt u tr n ni bt u truyn d liu khng bao gm thi gian overhead ca

lp vt l.

Vng StopTime cha 16 bit ch th thi gian kt thc phn b. Thi gian ny

c tnh bng byte, bt u khung l 0. Thi gian kt trc tr n byte d liu cui

cng c kt hp vi vic phn b ny.

Vng CRC: cu trc phn b c bo v s dng CRC-8.

g. Vng ti

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Vng ti truyn dn hi t c 2 phn: phn dnh ring cho ATM v phn dnh

ring cho GEM.

Phn dnh ring cho ATM: cha 53 cell ATM. Kch thc phn ny c a

vo vng Plend dnh cho ATM. Do vng ny cng c kch thc l bi s 53 byte.Cc cell hng xung th c lc ONU da vo ch s nhn dng ng o VPI

cha trong mi cell.

Phn dnh ring cho GEM: cha mt s khung GEM phc ha thnh a khung.

Kch thc ca phn dnh ring GEM th bng ton b chiu di khung tr i khi iu

khin PCBd v phn ATM. Khung hng xung c lc ONU da vo 12-bit Port-

ID cha trong mi phn on khung.

3.2 Cu trc khung hng ln

Cu trc khung hng ln c biu din Hnh 2.11. Chiu di khung th ging nh

khung hng xung. Mi khung cha mt s truyn dn t mt hay nhiu ONU. B

nh bng thng ch nh vic sp xp truyn dn ny. Mi chu k phn phi phi theo s

iu khin ca OLT, ONU c th truyn mt n bn overhead v d liu ngi dng.

Bn loi overhead l:

Overhead lp vt l (PLOu- Physical layer overhead).1 Cc hot ng, qun l v bo dng lp vt l (PLOAMu-Physical layer

operations, administration and management upstream).

2 San bng cng sut (PLSu- Power levelling sequence upstream).

3 Bo co bng thng ng (DBRu-Dynamic Bandwidth Report upstream).

4 Hnh 2.12 ch ra chi tit cc overhead. OLT ch th thng qua c trong b nh

bng thng c hay khng thng tin vng PLOAMu, PLSu hay DBRu c gi trn mi

vng phn b. Trng thi ca PLOu th n trong vng sp xp khi phn phi. Quy lut l

mi ln mt ONU chuyn qua mi trng mng PON

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.

1 Ngun: ITU-T Recommendation G.984.3, Gigabit-capable Passive Optical

Networks (G-PON): Transmission convergence layer, 02/2004.

Hnh 2.11 : Khung hng ln GTC

a. Vng overhead lp vt l hng ln

Vng overhead lp vt l hng ln gm cc vng l li m u, vng ranh gii

v 3 vng d liu tng ng vi ONU. duy tr kt ni vi ONU, OLT s th cp

vic truyn ln ca mi ONU trong khong thi gian ti thiu. Khong thi gian ny

c xc nh bi cc thng s dch v ca ONU. OLT s nh dng v iu khin li

m u v ranh gii trong cc bn tin overhead. Vng BIP c 8 bit.

Trc khi ONU-ID c gn, ONU t gi tr khng xc nh l 255 trong

vng ny. OLT c th kim tra vng ny xc nhn a ch phn b v truyn ng

n ONU. Vng ID cung cp trng thi ONU thi gian thc bo co cho OLT. Khi

ONU ch ra mt PLOAM khn cp ang i, OLT s cp mt v tr hng ln cho

php ONU gi bn tin PLOAM. Thi gian p li s t hn 5 ms.

b. Vng vn hnh, qun l v bo dng lp vt l PLOAMu

Cc hot ng, qun l v bo dng lp vt l PLOAMu c 13 byte cha cc

bn tin PLOAM c m t phn PLOAMd.

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Ngun: CEDRIC F. LAM , Passive Optical Networks Principles and Practice,

October 2007.

Hnh 2.12 : M t chi tit khung hng ln GTC

c.Vng san bng cng sut PLSu

Trnh t san bng cng sut PLSu c kch thc 120 byte, ONU s dng cho

vic o cng sut. Chc nng gip iu chnh mc cng sut ONU. Vng ny c gi

khi c ch th c. C ch iu khin cng sut th c li trong 2 trng hp l khi to

cng sut ban u ca b pht ONU (ch xy ra lc kch hot ONU) v thay i cng

sut ca b pht ONU (xy ra lc hot ng cng nh lc kch hot). PLSu c th c

yu cu bt k thi im no. nhiu trng hp, trong lc kch hot, OLT c th ci

t bit PLSu qung b cho php ONU thit lp b pht. Nu ONU khng s dng

vng PLSu th ONU s khng kch hot b pht. iu ny lm gim s ng .

d. Vng bo co bng thng ng DBRu

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Cu trc DBRu cha thng tin T-CONT. Vng ny c gi khi c ch th c.

Vng DBA cha trng thi lu lng ca T-CONT. Vng 8, 16 hay 32-bit c dng

cho mc ch ny. Vng CRC: cu trc DBRu c bo v s dng CRC-8. u thu

ca DBRu s thc hin pht hin v sa li CRC-8. Nu CRC ch th rng li khng thsa c th thng tin trong DBRu s b loi b.

e. Phn ti

Phn ti a ln c th l cell ATM, khung GEM hay bo co DBA.

Phn ti ATM hng ln c 53 byte. Chiu di ca phn ti ny phi nh hn chiu di

overhead c yu cu. OLT sp xp cc con tr phn ti ATM lun l 53 bytes.

Nu ti khng 53 bytes th n s n thm cho 53 byte, cc cell ATM hng ln

c trnh by nh Hnh 2.13.

Ngun: ITU-T Recommendation G.984.3, Gigabit-capable Passive Optical

Networks (G-PON): Transmission convergence layer, 02/2004

Hnh 2.13 : Cc cell ATM hng ln

Phn ti hng ln GEM cha mt s khung GEM (Hnh 2.14). Chiu di ca

phn ti ny phi nh hn chiu di overhead c yu cu.

Phn ti hng ln DBA cha bo co phn b bng thng ng t ONU nh

trong Hnh 2.15. Bo co bng thng ng u tin c xp hng cc byte u tin

ti v tr bt u phn b, tt c bo co th lin tip nhau. Nu chiu di phn b khng

khp vi ton b chiu di bo co th ONU s b bt phn cui ca bo co hay m

thm cc bit 0 phn cui nu khng . Ch rng ONU phi phn hi vic phn b

ti DBA thm ch nu mode ny ca DBA khng h tr th n vn duy tr phn ti ny.

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Hnh 2.14 Cc khung GEM hng ln



Hnh 2.15 : Bo co DBA hng ln

4 Phn b bng tn ng DBA trong GPON

Phng php c bn nht ca phn phi bng thng hng ln l phn b bng

nhau gia cc ONU. Phng php ny khng hiu qu. c bit l lu lng gi bi

nhu cu bng thng ca cc ONU th t khi bng nhau ti mi thi im. Vic tn dng

ton b bng thng c th c thc hin nu bng thng hng ln c phn phing ty theo nhu cu ca ONU. Trong khi ITU-T khng quy nh thut ton DBA,

G.983.4 quy nh khung v c ch thc hin DBA trong h thng BPON v GPON.

G.983.4 quy nh 2 c ch gn bng tn ng nh sau:

Vi phng php u tin, ONU ng vai tr l b ng, OLT gim st bng

thng ca mi ONU c s dng da trn s cell ATM nhn ri v khung GEM nhn

ri m n nhn trong khung GTC hng ln. V l do ny, phng php ny c coi

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nh l iu chnh cell nhn ri. Phng php ny cn c gi l bo co khng trng

thi. C nhiu bng thng hn c gn cho ONU nu vic tn dng bng thng vt

qu ngng quy nh. Thun li ca phng php ny l lm n gin ha ONU v

trnh vic s dng bng thng hng ln cho vic bo co nhu cu bng thng.Vi phng php th 2, ONU bo co trng thi b m n OLT. Do vy, n

c gi l bo co trng thi b m hay bo co trng thi SR (Status Reporting). Ch

th nhu cu bng thng trong loi T-CONT c truyn trong vng overhead lp vt l

c th hn l vng bo co bng thng ng DBRu. OLT s dng thng tin bo co

trng thi quyt nh phn b bng thng ph hp cho mi v tr ID.

5 Bo mt

Trong h thng PON th hng xung, d liu c truyn broadcast n tt c

ONU. Mi ONU ch c th truy cp d liu ca mnh, nhng nu ngi dng no c

nh ph hoi th c th gi ONU ca ngi dng khc truy cp d liu, h thng bo

mt PON s ngn chn vic ny. Ging nh cc mng khc, GPON s dng th tc mt

m ngn nga vic nghe trm cc tn hiu khng mong mun. Khng ging nh truy

cp wireless hay modem, trong mng PON, bt k ONU no cng khng th thy c

lu lng hng ln ca ONU khc. iu ny cho php lm n gin ha th tc mtm. u tin l ch cn mt m hng truyn xung ca d liu. Th 2 l d liu

hng ln c th truyn kha mt m. GPON s dng chun mt m AES (Advanced

Encryption Standard). l mt khi mt m m n hot ng trn mt khi d liu 16

byte (128 bit). c bit ch m c s dng. Khi mt m gi ngu nhin 16 byte

c pht ra v XOR vi d liu ng vo to ra d liu mt m OLT. ONU, d

liu c mt m ny th XOR vi chui gi ngu nhin 16 byte tng t nh OLT

to li d liu ban u. Vi ATM ch c 48 byte c mt m, vi GEM ch c phn tiGEM c mt m. OLT khi to vic trao i kha bng vic gi bn tin n ONU

thng qua knh PLOAM. Sau ONU s chu trch nhim to ra kha v pht ngc

tr v OLT.

Chng 3 : S LA CHN M HNH PON V HOT NG QUN L BO

DNG TRONG H THNG FTTH

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I. s la chn m hnh PON

T quan im k thut, mt im khc nhau c bn gia GPON v EPON l

cch h tr mch TDM. GPON chia tn hiu ln v xung thnh khung 125s. Khung

d liu c ng gi s dng k thut ng gi GEM. Cn trong EPON khungEthernet c chiu di c th thay i c dng lp vn chuyn. M phng mch th

cn thc hin mch TDM c bng thng c nh.

Trong khi EPON th ti u ha vn chuyn gi Ethernet, ng gi GEM cho

php thch nghi hn vi dng tn hiu khc. Trong h thng EPON, chc nng bo co

v chp nhn bng thng c b sung s dng MPCPDU. Mi port ONU vi LLID

(logical link indentifier) khc nhau yu cu khung Gate v Report ring, m chng l

khung Ethernet. Cng nhiu ID c phn phi th cng c nhiu overhead ca giaothc iu khin a im MPCP. Tri ngc li, cc chc bng bo co v nhn bng

thng GPON c th c i ln thnh phn u ca khi iu khin vt l PCB ca

khung GTC. Mi PCBd cha thng tin phn phi bng thng cho tt c container truyn

dn c phn b. iu ny lm cho GPON hiu qu hn so vi EPON. B chia 1:32

cho EPON v GPON, h thng EPON cung cp bng thng trung bnh l 31.25 Mbps

trn mi ONU c hng xung v ln, trong khi GPON vi tc truyn 2488Mbps

i xng hng xung v ln th bng thng cp cho mi ONU l 77.75 Mbps.

II . Chc nng hot ng, qun l v bo dng trong mng quang th ng PON

Trong mng truyn thng, nh cung cp dch v c nhim v l cung cp v

qun l cp truyn dn v cc thit b u cui mng. Vic thc thi, hot ng v qun l

ca mng yu cu kh nng cu hnh v kim tra cc thit b mng mt cch nhanh

chng v d dng cc kt ni v dch v lun c sn sng. Vic pht hin ra cc

trng thi hot ng bt thng trong mng s khc phc c cc s c ang tim n

v c th dn n s c ln hn nh l h mng. Trong mng PON th khc vi mng

truyn thng ch ti u cui pha khch hng th n l thit b nm trong nh khch

hng v n thuc quyn s hu ca khch hng, v th m khch hng phi t bo

dng thit b ca mnh v nh cung cp dch v ch c trch nhim vi thit b trm

trung tm v cp bn ngoi khng thuc quyn s hu ca khch hng. Trong phn

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ny, chng ta s ni v chc nng hot ng, qun l v bo dng trong mng quang

th ng PON.

2.1 Qun l mng

Hnh 3.1 ch ra cc thnh phn h thng qun l mng in hnh v cc mi quan

h ca chng. Ni iu khin qun l mng l mt trm lm vic vi phn mm qun l

mng chuyn bit. Ti trm lm vic ngi lm vic c th quan st c cc trng

thi ca mng, c th kim tra tt c thit b ang hot ng, cc thit b ny c cu

hnh ng hay cha v phn mm ng dng c c cp nht hay khng. Ngi qun l

mng c th nhn thy mng ang hot ng. Thm vo trm lm vic c th iu

khin ngun ti nguyn mng.Thit b c qun l trong mng PON l OLT, ONU, ngun d phng v b

ngun. Mi thit b c gim st v iu khin bi h thng qun l chung (EMS -

Element Management System). im quan trng y mc d pha khch hng t

bo dng thit b ONU nhng hot ng trong mng PON th thit b ny cng phi

c h tr t vn trng thi v iu khin cc chc nng t h thng EMS.

Cc module phn mm qun l c gi l agent nm trong b vi x l bn trong

n thu thp v bin dch thng tin lin tc v cc trng thi v vic thc thi cc thit b.

Cc agent ny s lu cc thng tin da trn thng tin qun l (MIB - Management

Information Base) ti trm trung tm v sau n cung cp thng tin qun l cc

thc th bn trong h thng qun l mng (NMS - Network Management System) t

trm lm vic. MIB th da trn thng tin c s ha, n xc nh d liu v s

nhn dng thch hp nh l cc vng trong c s d liu. Thng tin ny c lu trong

bng, b m. MIB khng vch r cch thu thp v s dng d liu nhng n ch nhr nhng g m agent c th thu thp v cch t chc d liu h thng khc c th s

dng chng. Khi agent thng bo cc vn m n ang gim st v d nh c s gim

cng sut ng ra OLT hay ONU, trng thi ngun d phng bt thng hay tc li

b vt qu gii hn, n s gi cc cnh bo n thc th qun l.

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Ngun: Gerd Keiser, FTTX Concepts and Applications,2006

Hnh 3.1 :Cc thnh phn h thng qun l mng v mi quan h ca chng

Vo lc nhn c cnh bo, cc thc th qun l c th khi to mt hay nhiu

hot ng nh l thng bo hot ng, ghi s kin, thot khi h thng hay t ng th

cch li hay sa li. H thng EMS cng c th truy vn v thm d trong h thng

kim tra cc trng thi. Vic thm d ny c th t ng hoc c khi to bi ngiqun l.

2.2 Cc chc nng qun l

a. Qun l thc thi

H thng vin thng s dng th tc qun l thc thi gim st v iu khin

cc thng s chnh m bo cht lng dch v QoS n cc u cui mng. Trong

mng FTTH, cc thng s ny bao gm chc nng loop-back iu khin t xa, gim stli, thng k li ONU v chuyn mch ngun trong trng hp c s c ONU. V

d cc thng s c gim st ti lp vt l l tc li bit v cc mc cng sut quang

OLT v ONU. Th tc qun l thc thi gn gi tr ngng cho cc thng s v thng

bo cho h thng qun l hay pht ra cnh bo khi n tin n ngng.

b. Qun l cu hnh

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Mc tiu ca qun l cu hnh l gim st thng ci t v cu hnh thit b mng.

Mc ch ca iu ny l kim tra v qun l hiu sut hot ng mng cu thnh t

phn mm v phn cng khc nhau. Qun l cu hnh cho php h thng cung cp ti

nguyn v dch v mng, gim st v iu khin cc trng thi v thu thp thng tintrng thi. Vic cung cp ny bao gm ci t cc mc cng sut quang t ng (v d

nh trong GPON ng ra ca ONU c th c ci t mt trong ba mc khc nhau),

gn bng thng hay ci t cc tnh nng ring c yu cu bi khch hng, phn phi

phn mm, nng cp agent v cu hnh thit b c lp li. Qun l cu hnh lu tt c

thng tin ny trong c s d liu c th truy cp d dng khi c s c n c tm

thy d dng gii quyt vn .

c. Qun l k ton

Chc nng qun l k ton l o cc thng s khi to mng ring mt c

nhn hay mt nhm khch hng trong mng c th iu chnh v ng nhp vo cc

dch v ph hp. Do , qun l k ton o t, thu thp v thng k ti nguyn v vic

s dng mng. Thm vo , qun l k ton c th kho st cc mu s dng hin thi

phn phi mng. T vic thng k, nh cung cp dch c th pht ha n v nh

thu cho vic s dng dch v.

d. Qun l li

Li trong mng nh l t cp trong truyn dn si quang, s c OLT hay

ONU c th xy ra trong mng FTTH. Li trong mng c th do bi thi gian cht ca

h thng hay do s gim st ca mng, qun l li l mt trong nhng chc nng quan

trng v c b sung y nht. Khch hng th mong i cch gii quyt nhanh

chng v ng tin cy khi mng c li. Hnh 3.2 m t qun l li bao gm quy trnhsau:

Gim st cnh bo c dng bo co cc cnh bo v cc nguyn nhn c

th xy ra cho h thng qun l mng. Qun l li c th tm lc cc cnh bo v cho

php nh qun l truy tm quan st thng tin cnh bo t log cnh bo.

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K thut c lp li quyt nh ngun gc, v tr v cc nguyn nhn c th gy

nn li c th l do t ng hoc c s can thip ca nh iu hnh mng. N bao gm

chc nng cnh bo lin quan n t cc phn khc nhau trong mng v chy th.

Th s c c cp bi h thng qun l mng. Cc th ny cho bit l li gv cch gii quyt n. Khi li c cp thnh th th chng s c th nh s can thip

ca nh iu trong c s d liu.

Kim tra th c thc hin mi ln khi c s c. Trong th tc sa li th vic

kim tra th l cng vic ch yu trong mng. N bao gm kim tra thc thi, kim tra

tin trnh x l v ghi li kt qu.

e. Qun l bo mt

Trong mng PON, d liu hng xung t OLT qung b n tt c ONU, mi

bn tin c truyn trong cng mt OLT u ging nhau. BPON, GPON v EPON u

c cc phng php ring m bo rng user ch truy cp c d liu ca mnh.

Mt k thut chun c gi l mt m, n s chuyn d liu thnh dng kh hiu ti

u gi bo v chng vic truy cp tri php, vic sa i, vic s dng min ph hay

s ph hoi khi d liu truyn qua mng.

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Ngun: Gerd Keiser, FTTX Concepts and Applications,2006.

Hnh 3.2: Cc tin trnh qun l li

Chun BPON ITU-T G.983 m t k thut c ch bo mt gi l trn, n ch mt

m d liu hng xung. C ch ny s dng s khng thay th cho mi 4 bit trn v

di ca mi byte v mt m s dng t kha ring. Mi t kha c trn c ci t

v cp nht t nht mt ln mi giy t mi ONU ring v hng ln th mi ONU

s gi t kha ny cho OLT OLT s dng lm t kha mt m. OLT cng c th

yu cu mt khu t mi ONU ngn chng vic ph hoi cc ONU khc. (ngi s

dng khc). hng ln th khng mt m bi vic nghe ln hng ny l rt kh do

mi ONU khng th nhn thy nhau tc khng th lin lc trc tip vi nhau m u

phi thng qua OLT. Chun GPON m t vic s dng c ch mt m im- im P2P.

y l chun mt m cao cp, c dng bo v thng tin d liu cho khung GPON.

Thut ton mt m cao cp ny mt m v gii m khi d liu 128 bit t khun dng

d liu gc.

III. Hot ng qun l bo dng trong h thng FTTH

tha mn nhu cu ca khch hng v p ng dch v cht lng cao, mng

FTTH phi trin khai th tc hot ng qun l v bo dng ng tin cy. Th tc ny

h tr vic tnh cc, bo mt, bo dng, cung cp v gim st hiu sut mng. N c

th thc hin vic s dng cc chun hay dng c phn mm h thng h tr hot ng

m rng trong h thng qun l mng. C nhiu chng trnh h tr hot ng c th

cp quyn thng qua trnh duyt web v vic chn la cc ng dng rng ri, n cho

php qun l mng cu hnh v iu khin hng trm phn t trong . Vic cung cp

phn phi cc mc dch v cung cp v cu hnh khc nhau cho cc loi dch v thoi,

d liu v video cho khch hng. Nh iu hnh mng cng nh c ch t ng cn xc

nh nu thit b ti u cui khch hng c th cung cp cc dch v c yu cu. V

d nh vic cung cp phi xc nh nu ONU c kh nng iu khin tc d liu ca32


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mnh d c kh nng kt hp vi kim tra hay khng th n cng h tr hot ng t xa.

iu ny th quan trng i vi nh cung cp dch v, vic qun l v xc nh cc vn

t xa c th ngn nga vic yu cu cc dch v chi ph t . Chc nng bo dng

hay qun l li trnh cc li tim n v s gim st trong mng FTTH. Nu li xy ra,tin trnh bo dng cn xc nh v lm r cng nhanh cng tt tha mn nhu cu

khch hng. Kh nng kt hp vi kim tra thay i thng tin trng thi gia ONU

v OLT bao gm chc nng loop-back iu khin t xa pht hin li trn mch hay cp,

thng k li ONU v thot khi ngun trong trng hp c s c ti ONU. Hnh 3.3

m t tn hiu iu khin trng thi mch vng, n c khi to OLT v truyn n

ONU sau ONU bo co trng thi v truyn ngc v OLT. Vic bo co ny ch th

mi th hot ng tt hay chng c th c dng xc nh nguyn nhn tc li bit cao.

Ngun: Gerd Keiser, FTTX Concepts and Applications,2006

Hnh 3.3 : OLT khi to loop-back iu khin t xa

Kt lun

Ni dung ca tiu lun gii thiu khi qut v cng ngh FTTH v trnh by

mt s m hnh PON c trin khai trong mng FTTH, nh l: APON, BPON,

GPON. T c th la chn phng php hay m hnh ph hp i vi h thng

FTTH m m bo c iu kin c s vt cht sn c cng nh p ng c y

nhu cu ca khch hng. Vi kh nng v thi gian cn hn ch v vy nghin cu ni

dung tiu lun cha thc s y v cn nhiu soi st. Chng ti rt mong c s

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ng gp kin ca thy v cc bn chng ti c th hon thin tiu lun ca mnh

c tt hn. Chng ti xin chn thnh cm n!

CC T VIT TT

ADSLAsymmetric Digital Subscriber Line ng dy thu bao s

bt i xngASE Advanced Encryption Standard Tiu chun m ha

APON ATM-Passive Optical Network Mng quang th ng

cng ngh ATM

ATM Asynchronous Transfer Mode Mode truyn dn

khng ng b

BPONBroadband Passive Optical Network Mng quang th ng

bng rng

BIP Bit Interleaved Parity

B-ISDN Bandwith-Intergrated Service Mng quang bng rng

Data Network a dch v bng rng

CDMA Code Division Multiple Access a truy nhp phn chia theo

m

CO Central Office Vn phng trung tm

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CRC Cyclic Redundancy Check a ch ch

DBA Dynamic Bandwidth Allocation Phn b bng thng ng

DBRu Dynamic Bandwidth Report Bo co bng thng ng

UpstreamDCE Data Communication Equipment Thit b u cui thng tin

DTE Data Terminal Equipment Thit b u cui thng tin

EPON Ethernet Passive Optical Network Mng quang th ng trn

EThernet

FCS Frame Check Sequence Kim tra li khungFEC Forward Error Correction

FTTB Fiber To The Building Cp quang thu bao ti ta

nh

FTTC Fiber To The Curb Cp quang thu bao ti chung

c

FTTH Fiber To The Home Cp quang thu bao ti nh

FSAN Full Service Access Network Mng truy nhp y

GEM GPON Encapsulation Method Giao thc ng gi GPON

GPONGigabit-capable Passive Mng PON tc gigabit

Optical Nnetwork

GTC G-PON Transmission Convergence Khung truyn dn hi t

GPON

HEC Header Error Control iu khin liIEEE Institute of Electrical and Vin tiu chun

Electronics Engineers

ITUT International Telecommunication

Union Telecommunication

Standardization

ISDN Integrated Services Digital Network Mng a dch v tch hp

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MAC Medium Access Control iu khin truy nhp mi

trng

MPCPMulti-Point Control Protocol Giao thc iu khin a im

MPCPDU Multi-Point Control Protocol Khi iu khin giao thcData Unit im-a im

NGN Next Generation Network Mng th h sau

OAM Operation, Administration Qun l vn hnh bo dng

and Maintenance

ODN Optical Distribution Network Mng phn phi quang

OLT Optical Line Terminal u cui ng quang

OMCI ONT Management Giao din iu khin vand Control Interface qun l ONT

ONT Optical Network Terminal u cui mng quang

ONU Optical network unit n v mng quang

OSI Open system interconnect H thng m

PCBd Physical control block downstream Khi iu khin vt l

PDU Protocol data units n v giao thc d liu

PLendPayload length downstream Chiu di ti hng xung

PLOAM Physical layer OAM Qun l vn hnh bo

dng lp vt l

PLOAMu Physical layer operations Qun l vn hnh bo

administration and maintenance dng lp vt l

upstream

PLOu Physical layer overhead upstream Mo u lp vt lPLSu Power leveling sequence upstream San bng cng sut

PON Passive optical networks Mng quang th ng

PRE Preample Tin khung

SA Source address a ch ngun

SFD Start of frame delimiter Khng gii hn bt u

khung

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MC LCMc Ni dung Trang

Chng1

Gii thiu cng ngh cp quang FTTH 1,2,3

Chng2

Mt s m hnh PON c trin khai trong mng FTTH 4

I APON 41 M hnh tham chiu APON 42 Cc c t cho APON 43 Cu trc phn lp APON 5

3.1 Lp vt l 63.2 Lp hi t truyn dn 64 Khung truyn dn APON/BPON 7II BPON 11III GPON 141 H thng GPON 142 Lp truyn dn hi t GPON 15

2.1 Chc nng cu GTC 15

2.2 Tc Bit ca GPON 173 Khung truyn dn GPON 173.1 Cu trc khung hng xung 17a Vng ng b vt l 18

b Vng ID 19c Vng qun l , vn hnh v bo dng lp vt l PLOAM 19d Vng BIP 19e Vng chiu di ti hng xung 19f Vng b nh bng thng 20g Vng ti 21

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3.2 Cu trc khung hng ln 22a Vng everhead lp vt l hng ln 23

b Vng vn hnh 23c Vng san bng cng sut 24d Vng bo co bng ng DBRu 24

e Phn ti 244 Phn b bng tn ng DBA trong GPON 255 Bo mt 26

Chng3

S la chn m hnh PON v hot ng qun l bo dng 27

I S la chn m hnh PON 27II Chc nng hot ng qun l 27

2.1 Qung l mng 282.1 Chc nng qun l 29

a Qun l thc thi 29b Qun l cu hnh 30c Qun l k ton 30d Qun l li 30e Qun l bo mt 31

III Hot ng qun l bo dng trong h thng FTTH 33Kt lun 34

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CC TI LIU THAM KHO

1. Cedric F. Lam, Passive Optical Networks Principles and Practice, October 2007.

2. Glen Kramer, Interleaved Polling with Adaptive Cycle Time (IPACT): A Dynamic

3. Gerd Keiser, FTTX Concepts and Applications,2006.

4. Http://www.metroethernetforum.org, Ethernet Passive Optical Network (EPON)

5. IEEE 8023ah - EPON spec

6. ITU-T Recommendation G.983.1, Broadband optical access systems based onPassive Optical Networks (PON), 2005

7. ITU G.984.3 - GPON spec

8. FPT Slide mng ngoi vi

9. Trng i hc Thi Nguyn Cng ngh mng quang th ng

V cc ti liu v FTTX, FTTH ca cc cng ty, FPT, CMC, NDC

Cc bi tho lun v FTTH trn cc trang VNtelecom, ientuvienthong.net,

haiphongit.

cong nghe ftth

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