mang truy nhap-hv bcvt i

7/30/2019 Mang Truy Nhap-HV BCVT I

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HC VIN CNG NGH BU CHNH VIN THNG

MNG TRUY NHP

(Dng cho sinh vin ho to i hc t xa)Lu hnh ni b

H NI - 2007


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HC VIN CNG NGH BU CHNH VIN THNG

MNG TRUY NHP

Bin son : THS. L DUY KHNH


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MC LCTrang

Mc lc iLi ni u viiChng 1: Gii thiu chung v mng truy nhp 11.1 Mng truy nhp

1.1.1 S ra i1.1.2 Khi nim mng truy nhp1.1.3 Hng pht trin mng truy nhp1.2 Phn loi mng truy nhp1.2.1 Truy nhp bng hp1.2.2 Truy nhp bng rng1.3 Giao din mng truy nhp1.3.1 UNI (User Network Interface)1.3.2 SNI (Service Network Interface)1.4 Cp ngun cho mng truy nhp1.4.1 S cn bng truyn thng1.4.2 Nhng vn trong cng ngh mi1.4.3 D phng accu1.5 Mch vng ni b1.5.1 nh ngha mch vng ni b1.5.2 Cc v d v mch vng ni b1.6 Cng trnh ngoi vi1.6.1 Phn loi1.6.2 Nhng yu cu i vi cng trnh ngoi vi1.6.3 Cc vn quan tm khi thit kng dy thu bao bng cp kim loi

1.6.3.1 i vi cp treo1.6.3.2 i vi cp ngm1.7 Cc dch vc mng truy nhp h tr

1.7.1 Gii thiu1.7.2 VoD1.7.3 Video trn ATM1.7.4 Qung co theo nhu cu mua bn t xa1.7.5 Cc dch v internet1.7.6 Hc t xa1.7.7 Cc dch v cnh bo1.7.8 Cc dch v trang vng1.7.9 Cc dch v cho nhu cu thit yu1.8 Cc tiu chun1.8.1 ADSL/VDSL1.8.2 Cable Modem/HFC1.8.3 DOCIS1.8.4 IEEE 802.14

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1.8.5 CableLabs1.8.6 ATM forum

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Chng 2: Cp v k thut lp t cp thng tin 232.1 Cp kim loi i xng

2.1.1 Kt cu cp i xng2.1.1.1 Kt cu dy dn2.1.1.2 Cht cchin2.1.1.3 Vchngm v gia cng2.1.1.4 Mng bao che2.1.1.5 Nhng quy lut xpt b dy rut cp

2.1.2 Xon dy trong cp ng2.1.2.1 i dy xon nguyn bn2.1.2.2 Hsxon2.1.2.3 Bc cn bng

2.1.3 Cc tham s truyn dn ca mch dy cp2.1.3.1 Stngng ca mch dy cp2.1.3.2 Mch dyng nht v khngng nht2.1.3.3 Csca phng trnh mch dyng nht2.1.3.4 Nhng hin tng hiung khi truyn dngin cao tn2.1.3.5 in tr2.1.3.6 tcm2.1.3.7 in dung2.1.3.8 in dn cchin2.1.3.9 Trkhngc tnh2.1.3.10 Suy gim tn hiu2.1.3.11 Suy hao di hay suy hao phn hi2.1.3.12 Tctruyn dn s2.1.3.13 Xuyn knh

2.1.4 Phn loi cp2.1.4.1 Cp UTP2.1.4.2 Cp ScTP2.1.4.3 Cp STP

2.1.5 Cc u kt ni cp2.1.5.1 u ni UTP2.1.5.2 u ni ScTP2.1.5.3 u ni STP2.1.5.4

u ni STP-A2.1.6 Kt cui cp

2.1.6.1 Cc bc tin xcnh2.1.6.2 Kt cui IDC cpng xoni

2.1.7 o th cp2.1.7.1 Gii thiu2.1.7.2 M tcc loi li cp2.1.7.3 Cc phpo thcp2.1.7.4 Cc phpo dng phng php TDR

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2.2 Cp ng trc2.2.1 Cu trc2.2.2 Cc cng thc tnh ton2.2.3 Cc c tnh k thut2.2.4 u ni cp ng trc2.2.5 Kt cui cp

2.2.5.1 Cc bc thc hin chung2.2.5.2 Mt v dkt cui cpng trc vou ni loi F

2.2.6 o th cp ng trc 50-Ohm v 75-Ohm2.3 Cp quang2.3.1 Lch s2.3.2 Cu trc2.3.3 Tn sc trong si quang2.3.4 u ni cp quang2.3.5 Ni si quang2.3.6 o th

2.4 Cu trc cc h thng cp2.4.1 Gii thiu2.4.2 Entrance facilities2.4.3 Backbone cables2.4.4 Horizontal cables2.4.5 Work Areas2.4.6 Equipment Rooms2.4.7 Telecommunications closets2.4.8 Cross-Connections2.4.9 Topologies

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Chng 3: Cc cng ngh truy nhp 873.1 Truy nhp bng quay s3.2 ISDN

3.2.1 Gii thiu3.2.2 Thit b ISDN

3.2.2.1 TA3.2.2.2 Dtel

3.2.3 Cu hnh ISDN3.2.4 Cc im tham chiu

3.3 Giao din V53.3.1 M hnh truy nhp V53.3.2 Kin trc dch v trong giao din V53.3.3 Giao din V5.13.3.4 Giao din V5.23.3.5 Mt sim khc nhau gia V5.1 v V5.23.3.6 Chng giao thc V.5

3.3.6.1 Nguyn l cbn

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3.3.6.2 Cu trc khung ca tn hiu 2M3.3.6.3 Cc giao thc V5

3.4 x.DSL3.4.1 Gii thiu3.4.2 Tc , phm vi bao ph, v gii hn thit k ca DSL3.4.3

Cc loi DSL

3.4.4 Cc thnh phn ca h thng DSL3.4.5 Tng thch ph ca cc h thng DSL

3.4.5.1 nh ngha3.4.5.2 Gii thiu3.4.5.3 ISDN3.4.5.4 HDSL3.4.5.5 SDSL3.4.5.6 CAP RADSL3.4.5.7 DMT ADSL3.4.5.8 Tng thch phca CAP RADSL vi DMT ADSL

3.4.6 iu ch DMT3.4.7 iu ch CAP/QAM3.4.8 o th DSL3.4.9 Lp t DSL

3.4.9.1 u chuyn ti dn MDF3.4.9.2 Nhng yu tcn lu khi chnng dy ADSL3.4.9.3 Lpt ti nh thu bao

3.5 HFC v Cable modem3.5.1 Mng HFC3.5.2 Truyn dn trn mng HFC3.5.3 IEEE 802.143.5.4 Kh nng bng thng3.5.5 Cable modem

3.5.5.1 Gii thiu cable modem3.5.5.2 M hnh kin trc phn lp cable modem3.5.5.3 Phcable modem3.5.5.4 nh xphca cable modem

3.5.6 POTS trn HFC3.5.7 An ton trong mi trng HFC

3.5.7.1 Gii thiu3.5.7.2 An ton v b mt trong mng HFC

3.6 Truy nhp quang3.6.1 Gii thiu3.6.2 Cu trc mng truy nhp quang

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3.6.2.1 Cu hnh tham chiu3.6.2.2 Cc khi chc nng

3.6.3 Topology v cc p dng ca truy nhp quang3.6.3.1 Aggregated Point to Point Using a Single Channel per Optical Fiber3.6.3.2 Aggregated Multichannel Point to Point3.6.3.3

Spatially Distributed WDM

3.6.3.4 Arbitrary Mesh3.6.3.5 Link Protection

3.7 Truy nhp v tuyn cnh (FWA)3.7.1 nh ngha3.7.2 Cc phng thc ng dng FWA3.7.3 Phn loi FWA

3.7.3.1 Dng ton bFWA3.7.3.2 Dng FWA thay thon B v C3.7.3.3 Dng FWA thay thon C

3.7.4 Cu hnh cbn FWA3.7.4.1 p dng cng nghchuyn dng3.7.4.2 p dng cng nghvibaim-aim

3.7.5 Ch tiu k thut ca FWA3.7.5.1 Sdng tn s3.7.5.2 Sp xp tn s3.7.5.3 Phm vi phsng3.7.5.4 Dung lng v dch v3.7.5.5 Tn x

3.8 VSAT3.8.1 Gii thiu3.8.2 Cu trc cbn ca VSAT3.8.3 K thut truyn dn ca VSAT

3.8.3.1 M ha ngun tin3.8.3.2 M ha knh v sa sai3.8.3.3 iu chv giiiu ch

3.8.4 Topology ca VSAT3.8.4.1 Star Topology3.8.4.2 Mesh Topology

3.8.5 Cng ngh truy nhp ca VSAT3.8.6 Cc ng dng VSAT trn th gii

3.8.6.1 VSAT IP ti Vit Nam3.8.6.2 VSAT for the World Bank and Africa Virtual University (AVU)

3.9 H thng thng tin v tinh di ng v khng dy3.9.1 Gii thiu

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3.9.2 Quo3.9.3 Cc h thng v tinh di ng

3.9.3.1 INMARSAT3.9.3.2 MSAT3.9.3.3 ARIES3.9.3.4

ELLIPSO

3.9.3.5 IRIDIUM3.9.3.6 ORBCOMM3.9.3.7 GLOBALSTAR

3.9.4 Cc bng tn trong h thng thng tin v tinh di ng3.9.5 LMDS

3.9.5.1 Gii thiu3.9.5.2 Kin trc LMDS

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vii

LI NI UBi ging Mng truy nhpc bin son nhm ging dy cho cc sinh vin theo hc h

o to t xa ti Hc vin cng ngh bu chnh vin thng. Ni dung Bi ging ny c bachng:

Chng 1: Gii thiu chung v mng truy nhp: Gip cho sinh vin nm c khi nimv mng truy nhp, phn loi mng truy nhp, xu hng pht trin mng truy nhp, cc cshtng xy dng mng truy nhp, cc dch v mng truy nhp h trv mt s ni dung cnthit d dng tip cn hai chng sau.

Chng 2: Cp v k thut lp t cp thng tin: Ni dung chng ny rt rng, ch yutrnh by sinh vin nm c cc vn :

Cu trc, cc thng s k thut, o th, v nguyn l hot ng cbn ca cc loicp ng xon i, cp ng trc v cp quang.

Cu to, cc thng s k thut, o th ca cc loi u ni cp ng xon i, cpng trc v cp quang.

Cu trc mng cp ca cc h thng mng in thoi, mng my tnh. Yu cu k thut cbn ca cc mng in thoi v mng my tnh c phm vi

hot ng va v nh c th thi cng lp t mng cp v thit b cho hai mngny.

Chng 3: Cc cng ngh truy nhp: C th ni mi cng ngh truy nhp l mt mn hcm sinh vin hc ngnh k thut vin thng cn c trang b. V d: i vi mng bng hp ccng ngh truy nhp in thoi truyn thng, vi mng bng rng hu tuyn c truy nhp ISDN,

x.DSL, HFC, PLC, vi mng bng rng v tuyn c h thng thng tin v tinh cnh VSAT vcc h thng thng tin v tinh di ng: GEO, LEO, MEO. Ni dung chng ny trnh by cccng ngh nu ra trn.

Bi ging Mng truy nhp cng c dng lm ti liu tham kho cho cc h khc trongHc vin cng ngh bu chnh vin thng.

Bi ging ny khng trnh khi nhng ch thiu st, rt mong sng gp ca ngnghip v bn c.

Ngi bin son chn thnh cm n tc gi ca cc ti liu v kin thc tham kho cngnh cc h trkhc bin son bi ging ny./.

TP. H ch Minh, ngy 08 thng 5, nm 2007

L Duy Khnh.


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GII THIU

Mng truy nhp l phn mng nm dm cui cng ca mng thng tin

lin lc. S ra i v pht trin ca n nhm phc v cho nhu cu s dng thngtin lin lc ca con ngi ngy cng phong ph hn. Tin thoi truyn thng,fax, cho n cc dch v mang tnh tng tc hn nhin thoi hi ngh truynhnh, hc tp t xa, xem truyn hnh theo yu cu, internet,

Nh vy mng truy nhp trnn a dng t bng hp nh truy nhpquay s theo kiu truyn thng v ISDN cho n bng rng nh x.DSL, HFC vCable modems, PLC, cp quang, h thng thng tin v tinh,


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Chng 1: Gii thiu chung vmng truy nhp

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1.1 MNG TRUY NHP1.1.1 S ra i

Mng vin thng hin nay c pht trin theo hng hon ton s ha a phng tin vinternet. iu ny lm cho vic tm kim phng n gii quyt truy nhp bng rng c gi thnh

thp, cht lng cao trnn rt cp thit.Cng vi s pht trin ca x hi thng tin, nhu cu s dng dch v vin thng ngy cng

tng, t dch vin thoi n dch v s liu, hnh nh, a phng tin. Vic tch hp cc dchv ny vo cng mt mng sao cho mng vin thng trnn n gin hn ang trthnh vn nng bng ca ngnh vin thng quc t.

1.1.2 Khi nim mng truy nhpMng truy nhp v tr cui ca mng vin thng, trc tip u ni vi thu bao, bao gm

tt c cc thit b v ng dy c lp t gia trm chuyn mch ni ht vi thit bu cuica thu bao. C th hiu khi nim v mng truy nhp theo cc ni dung sau y:

Mng truy nhp (AN) l phn mng gia SNI v UNI, c nhim v truyn ti cc tnhiu n thu bao.

M hnh tham chiu vt l ca mng truy nhp c m t qua hnh sau:

Phm vi ca mng truy nhp c chia ra thnh ba phn: SNI ni n nt dch v; UNI nin thu bao; v Q3 ni n TMN.

Cn c vo phm vi ca mng truy nhp m mng ny c cc c im nh sau:

Thc hin chc nng ghp knh, ni cho, v truyn dn. Mng truy nhp khng thc hinchc nng chuyn mch.

Cung cp a dch v: chuyn mch, s liu, hnh nh, thu knh, ... ng knh mng tng i nh: trong ni thnh khong vi km, ngoi thnh khong t

vi km n hn 10 km.

Gi thnh u t mng ph thuc vo thu bao: bi v thu bao gn nt dch v cn tcp truyn dn hn so vi thu bao xa nt dch v. S chnh lch gi thnh u t c thln n 10 ln.

SW SW

SW RSU RSU CPESN

FP DP Sub

Dy phn phiDy chnh Dy thu bao

Mng truy nhp

Hnh 1.1: M hnh tham chiu mng truy nhp


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Thi cng ng dy kh khn: Vic xy dng mng cp ni ht l phc tp, nht l trongkhu vc ni thnh. Cn phi quan tm n nhiu vn : m quan, cc cng trnh khcnh nh , in, nc, ng s, ...

Kh nng tip cn cp quang ca thu bao: ONU t cng gn nh thu bao th on cpng ni n nh thu bao cng ngn.

Kh nng thch ng i vi mi trng: ONU ca mng truy nhp c th thch ng chohon cnh mi trng khc nghit, c tht ngoi tri. Tuy nhin mi trng cng khcnghit th yu cu i vi thit b cng cao. S bin thin tnh nng ca cc linh kin int v linh kin quang theo nhit tun theo hm m, do tnh nng cc linh kin trongthit b mng truy nhp xu i nhanh gp 10 ln thit b thng thng.

1.1.3 Hng pht trin mng truy nhpC tha ra vi con s trong qu kh thy s quan tm trong vic pht trin mng truy

nhp: Hng Bell ca M v nhiu cng ty khc u t 50-60 t USD i mi mch vngthu bao cho hn 10 triu thu bao. Cng ty Future Vision xy dng ti bang New Jersey mtmng bao gm MPEG-2, ATM, PON v trong thng 8 nm 1995 hon thnh giai on 1 thnghim 200 h gia nh. Nht Bn vo u nm 1995 u t 20 t USD xy dng ton dinmng truy nhp, n nm 2000 c 10% khu vc thc hin cp quang n ta nh, n nm2015 s thc hin cp quang n h gia nh. Ti Anh, c, Trung Quc cng c su tngk cho mng truy nhp.

p ng nhu cu ngy cng cao ca ngi s dng, th vic u t mng truy nhp ca ccnc ni chung v Vit Nam ni ring cng theo cc nh hng sau y:

Bng rng ha mng truy nhp. Cp quang ha mng truy nhp. i mi cng ngh cp ng. Mng cp quang thng ly cng ngh ATM lm cs. Truy nhp v tuyn bng rng. Cng ngh truy nhp SDH. Cng ngh SDV da trn FITL v ATM.

1.2 PHN LOI MNG TRUY NHPSau y l mt s loi truy nhp c phn loi da trn bng thng.

1.2.1 Truy nhp bng hpTruy nhp bng quay s (Dial-up Aceess): y l mt loi truy nhp bng hp da trn

phng thc quay s thng qua modem. Nu p dng trn ng dy thu bao truyn thngth modem cht c tc ti a 56 Kbps. Nu p dng trn ng dy thu ISDN-BA,c 2 knh B vi mi knh bng 64 Kbps v mt knh D bng 16 Kbps nn cn gi l truynhp 2B+D.


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1.2.2 Truy nhp bng rngng dy thu bao s (DSL):Vi cng i dy in thoi truyn thng c thc dng truyn d liu tc cao, nh minh ha trong hnh 1.2. C mt vi cng ngh cho DSL, khi mngi dng c nhu cu tc ng xung cao hn tc ng ln th c hai loi DSL bt ixng : DSL v VDSL. Ty thuc vo chiu di mch vng, cc h thng DSL c tht n tc t 128Kbps n 52Mbps.

Cable Modems:Cable Modem l mt loi modem cung cp truy nhp d liu c truyn trn hthng truyn hnh cp. Cable modem ch yu c dng phn phi truy nhp internet bng rng.Bng thng ca dch v cable Modem thng mi thng thng trong khong t 3 Mbps n 30Mbps hoc ln hn.

Cp quang:iu mong mun ca cc cng ty vin thng l a cp quang n tn nh ca ngis dng. Vi SONET im ni im v cc vng ring, cp quang s bao ph cc khu dn c,cng s c th phc vin thoi, d liu, hi ngh truyn hnh, v cc dch v khc trong hinti, v cng d dng nng cp khi c yu cu bng thng ln hn trong tng lai. Vi cng nghAPON nh m t trong hnh 1.4, sp ng yu cu t ra cng nh vn v chi ph xy dngmng. Cu trc mng GPON c bng thng 1,244 Gbps cho ng ln v 2,488 Gbps cho ngxung.

Hnh 1.2: Truy nhp ADSL

Hnh 1.3: HFC vi cable Modems


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V tuyn: Cc h thng v tinh c quo thp nh Teledesic v Bridge c th ti hng chcMbps n u cui ngi s dng, cn h thng LMDS bng thng t n 1 Gbps tn s28 GHz.

Truy nhp qua ng dy in:ng dy in l mt mi trng c nhiu nghim trng, nhngn c kh nng truyn cc dch v vin thng c tc bit cao. Chng c ni vi ng dyin trong nh kin trc nn mt mng truyn dn hon chnh. Cc thit bu cui c ktni vo cm in trong nh c th truy nhp n mng bng rng. Kin trc ny kt hp mtcch hi ha vi cc h thng tng ha trong nh, cho php iu khin t xa cc thit bt tinh thng qua internet.

1.3 GIAO DIN MNG TRUY NHP1.3.1 UNI

UNI l mt im phn nh ranh gii gia nh cung cp dch v v thu bao. Ranh gii ny

thit lp nn giao din k thut v phn phi cc hot ng tng ng. UNI c hai loi: c lp vdng chung. UNI dng chung l ch mt UNI c thm nhim nhiu nt dch v, mi truy nhplogic thng qua SNI khc nhau ni vi nt dch v khc nhau. V d, trong metro ethernetnetwork, UNI l mt lin kt ethernet hai chiu (bidirectional ethernet link).

1.3.2 SNIL giao din pha dch v ca mng truy nhp. SNI ch yu gm giao din tng t (giao

din Z) v giao din s (giao din V). thch ng vi nhiu mi trng truyn dn trong mngtruy nhp, phi hp vi nhiu loi truy nhp v nhiu loi dch v truy nhp, giao din V phttrin thnh giao din V1 n giao din V5. Giao din V5 l mt loi giao din thu bao s tiu

chun quc t ca tng i chuyn mch s ni ht, n c thng thi h trnhiu dch v truynhp thu bao, c th chia thnh giao din V5.1 v V5.2.1.4 CP NGUN MNG TRUY NHP1.4.1 S cn bng truyn thng

Trong mng PSTN truyn thng, my in thoi c cp ngun t tng i. Ngun cungcp l mt chiu (dc) trn cng i dy ng truyn ti tn hiu thoi. Cc u cui thng thngkhng cn c s cp ngun ring, tr nhng u cui c bit nh my fax.

Hnh 1.4: Mng APON


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Vn quan trng trong mng PSTN l d ngun in li b s c th mng cng phihot ng tip tc. Cc dch v trong mng PSTN c thit k hot ng khng ph thucvo ngun in li ca a phng. Cng chnh v tng i cp ngun cho u cui, nn phm vi

phc v ca tng i b hn ch, nu s dng cp c ng knh ln th kh nng u cui ko xahn, tuy nhin nu dng cdy ln th chi ph cao, nng, chim nhiu khng gian hn.

Nh vy trong mng PSTN truyn thng, khong cch t tng i n my u cui b giihn mt cch t nhin sao cho ph hp kh nng truyn dn ngun n u cui. Tuy nhin trongcc cng ngh mi, gii hn ny khng cn l t nhin, bi v khong cch t tng i n ucui ch ph thuc vo vic tn hiu c truyn n c u cui hay khng, ch khng ph thucvo vic cp ngun. Do s cn bng gia vn cp ngun v vng phc v khng cn na.

1.4.2 Nhng vn trong cng ngh miMt trong nhng thch thc i vi s cn bng trong phng n truyn thng dnh cho

in thoi l vic tn dng ht tim nng truyn ti thng tin ca nhng i dy ng hin c.Nhng c gng trin khai ny hin nay th hin r rng nht s pht trin cc h thngHDSL v ADSL, nhng thch thc ban u li n t cng ngh li dy.

Khi tt c nhng i dy d tr trn ng cp hin c c s dng ht, th vic lp tmt cp ng mi s l tn km. Thm ch cn c th tn km hn, nu phi thc hin vic ny p ng mt nhu cu v dch vt xut.

Cc h thng li dy v cc h thng ghp knh, c tp trung v phn tn, u c phtminh ra tn dng nhng dung lng truyn ti thng tin cha c s dng ca cc i dyng. Cc h thng li dy cn cp ngun cho cc thit bin t ti u xa ca i dy ng.May thay, c th tn dng tnh cht dn cm ca nhu cu v ngun l chc chn nm trong khnng ca n, v thi gian ng truyn khng hot ng thng nhiu hn l hot ng. Mt accuc th np li c c th dng b ngun cp t tng i khi ng truyn hot ng.

Trong thc t, vic trin khai mt accu np li c theo cch nh vy to ra nhiu vn ,bi v khi s dng ng truyn cng cao, mt khch hng thng mi c th lm phnght in ca accu. mt mc no , iu ny c thc b p nu vic lp t c thchin theo yu cu c th, sao cho kt cui s dng cng cao nht c cp ngun bnhthng vi kt qu l ch cn mt accu cho nhng kt cui c s dng cng km hn.Nhng cp ngun nh th s khng tin cy, bi v thu bao c t do thay i vic s dng cc

in thoi khnghot ng

in thoihot ng

Ngun in ctch tr trong accu

t

Hnh 1.5: S dng mt accu np li c b s tiu hao ngun


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kt cui . Ngoi ra, thi gian s dng ca mt accu np li c l c hn, k c trong iu kinmi trng tt ti nh ring ca thu bao, dn n nhng chi ph bo dng ln. c bit, nukhng c s cnh bo v s ngng hot ng ca mt accu s pht sinh vic bo dng ngoi khoch khi accu gp s c.

ng tic, khng th s dng mt accu m (b) s tiu th ngun cho nhng h thngli dy rt tiu hao ngun, cc h thng HDSL v ADSL dung lng cao hn. l v nguntrung bnh cho nhng h thng ny thng vt qu kh nng c thc cung cp trn cc idy ng. Vn ny khng ln nh vi cc h thng v tuyn v si quang, bi v vic truyndn ngun ti cc kt cui xa bng v tuyn hoc si quang l khng kh thi. D vy, cc hthng dy ng s dng mt accu b s tiu th ngun ca cc kt cui xa, c th khng cu im ln so vi cc h thng v tuyn v si quang bi chi ph bo dng v thay th accu xa.

Thot nhn th v tuyn dng nh l phng tin km nht cho vic cp ngun, v khngth chuyn i c mt lng ngun in ln dc mt tuyn v tuyn. Tri li, cc si quang cth truyn c mt lng nng lng c ch, v ngi ta cho rng n c th cp ngun

cho mt my u cui c bit cng sut thp. Ngi ta cng cho rng cc tuyn cp quang/dyng c thc s dng chuyn i c thng tin v ngun. Nhng khng may, trong nhngkhi nim ny c mt s sai lm. Mc d mt lng ngun nht nh c thc chuyn itrn mt si quang, nhng hiu sut bin i sang cng sut in thp lm cho cng sut pht cnthit phi rt cao, m iu ny c th lm nguy him cho cc hot ng bo dng. Ngoi ra, cngc th cn ti mt accu m, nh c th gim c cng sut quang t cc nh xung gn hngi tr trung bnh, iu ny li gy ra vn v bo dng accu. Hn na, nu nhng u im vchi ph ca vic chia tch thng c tng ln, th cng sut pht quang s cn c tng lnvt qua gi tr yu cu cho hot ng im ni im, do cc b chia quang gy ra vic gim cngsut thu. Khi nim v mt cp lai cng l sai lch, bi v cc h thng dy ng thm ch khngth cp ngun tng xng vi dung lng truyn ti thng tin ca chnh chng, mt dunglng km xa dung lng truyn ti thng tin ca mt si quang lin i.

C mt ng dng ca vic dng si quang cp ngun, nhng ng dng ny li c tnhmu thun. Gii hn trn i vi tc d liu ca cc h thng si quang c th tng nu sdng cc b khuch i quang khuch i tn hiu quang. Cc b khuch i ny c thccp ngun rt hiu qu bng si quang, bi v yu cu ch yu ca chng l ngun quang, chkhng phi ngun in. y l s mu thun, bi v vic s dng ph hp nht ca ngun quangl lm tng dung lng truyn ti thng tin ca cc h thng si quang, v v th lm trm trnghn vn cp ngun cho cc kt cui xa, bi v nhng kt cui xa cn nhiu ngun hn,do dung lng ca h thng tng ln.

1.4.3 D phng accuNu ngun in ni b trong mt tng i b s c, th ngun khn cp thng c cung

cp bng mt my pht in d phng. Nhng my pht in ny lun c mt sn sng v c thc bo dng trong mt mi trng tt, thng vi s c mt ca cc nhn vin bo dng.Cc my pht in cng sut ln c th to ra nhiu nng lng hn so vi nhng accu np lic.


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Trn thc t thng khng s dng cc my pht in ti nhng u xa ca cc mng truynhp, d l nhng my pht in c cng sut nh, bi nhng kh khn ca vic thng gi v bodng. Thng gi c th l mt vn , bi v u xa c tht trong mt khng gian kn,chng hn mt hp ngm. Bo dng cng l mt vn bi v cn phi gi mt k thut vin

bo dng ti cc v tr xa b s c v ngun.

Bi vy nhng accu np li c l gii php hin nhin i vi vn ngun d phng ticc u xa ca mt mng truy nhp. Nhng accu ny c thm bo lun c np y trong khihot ng bnh thng, v c s dng cp ngun cho mi u xa ca mt mng truy nhpnu ngun cp in chnh b s c. Nhng accu khng np li c c thc s dng lm giiphp thay th cho cc accu np li c cho hot ng mt ln. Ging nh cc my pht in dphng, i vi cc accu khng np li c, cn c mt nhn vin k thut n thay cc accu sau khi chng c s dng ht in. Cc accu khng np li c cng c mt tui th hnch v v vy s cn c thay th khi chng qu hn s dng, cho d chng vn cha c sdng. Cc accu np li c c a chung bi v chng c chi ph bo dng thp hn, dochng khng cn phi thay th sau khi s dng.

Tuy nhin, c mt s vn lm cho vic s dng cc accu np li c km hp dn i.C l vn r nht v mt vt l l kch thc ca nhng accu ny. Nhng tham s xc nhkch thc ca nhng accu ny l cc yu cu v ngun ca cc u xa v khong thi gian mngun in phi cung cp c, cng vi cng ngun, l tham s xc nh mc hiuqu m cc accu tch tr ngun.

Cn c nhng tr ngi v mt mi trng i vi vic s dng cc accu np li c.Nhng trngi ny c th trnn r rt hn theo thi gian do s nhn thc ngy cng tng v ccvn mi trng. Nhng accu axit ch, nh loi s dng trong cc xe hi, l loi accu np lic ph bin nht. Ch trong cc accu ny gy ra nhim cho mi trng, v c mt yu cu lnhng accu c phi c thu hi v hy b mt cch an ton.

1.5 MCH VNG NI B1.5.1 nh ngha mch vng ni b

Trong vin thng, mch vng ni b (local loop) l mt mch dy kt ni t thit b ti snkhch hng n bin ca nh cung cp dch v vin thng. Trong mng PSTN, mch vng ni bl mch dy cp kt ni thit bu cui n tng i ni ht. Mch vng ni b h trcc ngdng truyn thng s liu, hoc kt hp truyn ting ni v s liu nh trong DSL.

Cc kt ni mch vng ni b c thc s dng trong cc cng ngh: Tn hiu thoitng t v bo hiu trong POTS, ISDN, DSL.

Cc kt ni mch vng ni b cn hin din trong cc cng ngh: PLC : Electric local loop,thng tin v tinh: Satellite local loop, Cablemodem: Cable local loop, v LMDS-WiMAX-GPRS:Wireless local loop.

1.5.2 Cc v d v mch vng ni b Loi n gin nht ca mch vng ni b c khong cch t 2 Km n 4 Km vi cdy

0,4 mm hoc 0,5 mm, s dng cp ng xon i.


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Loi c p dng c dy khc nhau, trong khong cch t n 2,5 Km dng dy0,4 mm, tip theo 1,5 Km dng dy 0,5 mm. Khong cch dng dy 0,4 mm c th thayi t 1,5 Km n 5,55 Km, v c th mrng n 6 Km.

Loi mch vng dng ba cdy khc nhau : on 0,2 Km tnh t tng i ni ht dng dy0,32 mm (28 AWG) ; tip theo t 1Km n 5 Km dng dy 0,4 mm ; v khong cch cnli dng dy 0,9 mm (10 AWG), khong ny c th l 4 Km tnh n CPE. Vi loi mchvng ny khi mrng n ht kh nng khng cn cun ti.

Loi mch vng c cu r, trong cu hnh ny ch dng mt cdy l 0,4 mm. Tuy nhincho php cu r c th ko di n 0,5 Km tnh tim r.

1.6 CNG TRNH NGOI VI1.6.1 Phn loi

Cng trnh ngoi vi c th phn loi theo kiu mng, lp t, v h thng truyn dn.

Phn loi theo kiu mng c cc loi cng trnh sau y:

Cng trnh ng dy thu bao: l cng trnh nh thu bao, phng tin in thoi cng cng,v thit b PBX c kt ni vi thit b ca tng i trung tm. Cp dng cho ng dy thubao c gi l cp thu bao v c phn thnh cp feeder v cp phn phi. Cp feeder l phncp thu bao i t tng i n im ni cho CCP.

Cng trnh cp trung k: l cng trnh kt ni cc tng i trung tm vi nhau.Cng trnh ng dy ng di: l cng trnh kt ni cc tng i trung tm ng di vi nhau.Thng thng, cc loi cp ng trc, cp quang, v tuyn c s dng lm kt ni.

Phn loi theo lp t, c cc cng trnh nh sau:

Cng trnh ng dy trn khng (cp treo): Mc d ng dy truyn dn trn khng c nhnghn ch cbn do bnh hng ca mi trng t nhin v nhn to, n vn c s dng khrng ri, c bit l ng dy thu bao. Sdnh vy l v cc cng trnh ngoi vi trn khngthng thng rt kinh t so vi cc cng trnh ngm.


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Cng trnh ngm (cp ngm): Thng thng, khi cp ngm c chn su di lng t trn 1mt th chng c nhng s ph hoi ca thin nhin v nhn to. Tuy nhin, chi ph xy dngt hn chi ph cng trnh trn cao. ng truyn dn ngm thng c s dng cho cp ngdi, cp trung k v cp feeder dng cho thu bao. Chng c chn trc tip hay t trong ngngm di lng t. Cng trnh ngm lm p cnh quan th v khng chim dng khng gianbn trn, nn gn y c xu hng ngm ha cc cng trnh ngoi vi cp.

Cng trnh ng dy di nc: Cc dy cp c t di y h, sng, gi l cp di nc.Cp t di y bin gi l cp bin. Cp di nc v cp bin c lp v bc c bit chngli cc tc nhn gy nguy hi cho cp nh: thm nc, n mn, lc nn, ...

Phn loi theo h thng truyn dn, c cc cng trnh nh: truyn dn hu tuyn, v tuyn,v truyn dn quang.

1.6.2 Nhng yu cu i vi cng trnh ngoi viCng trnh ngoi vi phi c nhng tnh cht in tt truyn cc tn hiu thng tin. N

phi vng chc di nhng iu kin hy hoi khc nhau ca thi tit, a hnh, v nhn to. Sauy l cc yu cu vin v ci vi cng trnh ngoi vi.

- in trcch in.- Sc bn in mi.- in trdy dn.- Suy hao truyn dn.- Mo.- Xuyn m.- Sng nht ca cc tnh cht in.- Sc bn chc.-Nghin cu nhng mi nguy him v nhiu lon.- Xem xt v bo dng.

1.6.3 Cc vn quan tm khi thit kng dy thu bao bng cp kim loi1.6.3.1 i vi cp treoLa chn tuyn: Mt tuyn cp treo phi tnh n yu t kinh t, s tin li cng vic v tin libo dng nh sau:

- C li th nht cho vic phn phi v lp t dy tch ra.- C di ng dy ngn nht.- Dc theo tuyn cp khng c s thay i d kin hay bi bng s theo k hoch pht

trin th.

- Khng ng n cc ng s, giao thng v cc kt cu do ngi khc qun l iu hnh.Xc nh vng n v v vng phn phi: Vng n v l vng c tuyn cp d ton nhu cu trong10 nm cho ng dy chnh phn phi cnh, c cn nhc n thay i ng s, nh ca, ....


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Mt vng n vc phn chia thnh cc vng phn phi, trong mi vng phn phi c mtng dy chnh v cc tuyn nhnh lin quan c hoch nh phn phi. Cc vng phnphi c thit lp sao cho s phn phi c kinh t nht c cn nhc n cc ng dy hinhu v cc iu kin ng s.

D bo nhu cu: Khi lp d bo nhu cu cn lu n cc im sau y:-Nhu cu i vi cc ng dy cho thu v cc dch v phi thoi c th khc vi nhu cu

c d bo trong cc khu trung tm ca thnh ph ln.

- S thu thp thng tin cha y t cc tng i in thoi ti thi im d bo nhu cu vvic thit kng dy thu bao c th dn ti cc don khng chnh xc v nhng sthay i trong nhng iu kin tng lai ca vng ny.

-Ngay c trong cc vng m ti cc ct in thoi c phn b mt cch ng nht,nhu cu cho mi ct thc t c th thay i do s khc nhau din tch t ai cho mi nginh.

- Kho st cc iu kin thc t: y l mt chui cng vic kim tra xem nhu cu hin tii vi ton b vng phc v ca mt tng i c phn phi nh th no trn cc vngphn phi cnh lin quan d bo nhu cu cho tng lai. Tm tt cc bc kho stthc t nh sau :

Bc 1: Thu thp v sp xp cc t liu, s liu v cc ti liu khc.

Bc 2: Kho st hin trng.

Bc 3: D bo nhu cu.

Xc nh ng knh dy cp:- ng knh phi tha mn suy hao ng dy, in trdc, v cht lng truyn dn ghi

r do tng i qui nh. Cc gi tr tng ng ca phn cp ngm di t phi c tri.

- Mt s v d thc t v cc phng php xc nh ng knh dy cp:Mu M t V d thc t Vng c th pdng

1 Ch c cp ca ng dy chnh trongmt vng phn phi cnh c tiuchun ha vi mt ng knh dy cp h tr cho thu bao xa nht trongvng. Cc ng knh dy ca cpnhnh c tnh ton khi cn thit.

Cc vng ngoivi thnh ph.

2 ng knh dy c tnh ton cho micp trong mt vng phn phi cnhtheo tng di cp ring, h tr thubao xa nht trong vng. Cc ngknh dy ca cp nhnh c tnh tonkhi cn thit.

Cc vng trungtm thnh ph.


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3 Mt vng phn phi cnh c chiara thnh mt s khu vc nh hn theong knh dy cp. ng knh dycp c p dng mt cch tng chocc ng dy chnh v nhnh trongmi khu vc. Cp c tiu chun hatrong mi vng phn phi cnh theong knh dy dn nhm h tr thubao xa nht trong vng.

Cc vng ngoi v trung tm

thnh ph xenln nhau.

4 Cp c tiu chun ha trong mtvng phn phi c nh theo ngknh dy h tr thu bao xa nhttrong vng.

Cc vng ngoivi thnh ph(trong giai onlp t khilng ln)

Xc nh loi cp: Cp treo c nhiu loi khc nhau nh : CCP-AP (cc loi SS v round), CCP-CS, CCP-HS, CCP-ES. Bng sau y trnh by cc tiu chun c th p dng cho nhng loi cp

ny.

Loi p Khu vc ng dngCp CCP-AP (1) Loi SS: tt c cc khu vc tr khu vc dnh cho cp CCP-CS, CCP-HS v

CCP-EC.

(2) Loi round: cc loi 0,4-400; 0,65-200; 0,9-100.Cp CCP-CS Nhng khu vc d b h hng do chim, cn trng, ng vt, sn bn, ...

Cp CCP-HS Nhng khu vc d b h hng do chim, cn trng, ng vt, sn bn, ...

Cp CCP-ES Nhng khu vc cn c cc bin php chng li hin tng can nhiu do cm ng.

Xc nh loi ct: La chn loi ct cn xem xt n yu t tit kim, kh nng lm vic, v ccyu cu x hi. Tuy nhin khi p dng loi no th n cng cn c xc nh theo cc yu cusau y:

- Phi dng cc ct thp nu d kin phi thay th trong tng lai gn do phi di chuyn hocv bt k l do no khc.

-Nu qui nh trong cc cuc thng lng vi nhng ngi ngoi cuc (cc khu t tnhn, ng s hoc c dn a phng) th cc loi ct quy nh phi c s dng.

- Cc ct i ngoi tr cc ct c np, chc dng vi cc ct hp quy cch.- Cc ct kinh t nht phi c dng trong cc trng hp trn.

Xc nh v tr ct: Vic s dng ring a im lp t ct trnn rt kh khn do: gi ttng, quyn li ca c dn a phng. V tr dng ct c nh hng rt ln n kh nng thi cngv an ton cho vic xy dng v bo dng ct. i khi chng c th gy phin h cho c dn aphng. Do vy, cc v tr phi c la chn cn thn, c lu n cc im sau y:

-Nu ct cn phi xy dng trn ng, phi iu tra xem liu b rng ng c c dkin mrng hay khng. Nu s mrng nh vy c quy hoch th kim tra xem c bao lu ri.


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-Nu ct cn c xy dng ti nh ring ca c dn, th b tr v tr ct trn vnh ai canh ring sau khi kim tra xem ch nh c k hoch mrng hoc xy li nh,

- Trong cc khu vc c tuyt hay nhit thp cn ch n cc yu t do tuyt v nhit thp gy h hng ct.

Trong trng hp s dng chung ct vi ng dy in lc n cho php gim ng k chi

ph lp t v bo dng ct, s dng hiu qung s, gim thiu cc nh hng ca ct ngiao thng v ci thin m quan th. Vic s dng chung ny cn c ngha nhng conng hp, ni m chnh quyn a phng, b phn qun l ng s mun ci thin tnh hnhcc ct chim c c hai bn ng lm trngi giao thng.

1.6.3.2i vi cp ngmCc phng tin ng dy thu bao phi ni mt cch hiu qu cc thu bao phn tn trn

khp mt vng no ti mt tng i in thoi t ti trung tm, n khng ging nh ccng trung k ni hai im vi nhau. V vy, cc phng tin ng dy thu bao ni chung chai cu hnh: mng ng trc gn tng i in thoi c gi l h thng ng dy feeder, vmng nhnh gn cc thu bao gi l h thng phn phi.

Mi h thng s dng mt phng php phn phi cp sao cho ph hp vi tnh nng can. i vi h thng ng dy feeder s dng phng php phn phi FD thay cho phng phpphn phi feeder cin. i vi h thng phn phi th dng phng php phn phi t do.

Phng php phn phi cp feeder cin:

Phng php ny c mt sc im nh sau:

- Mt s vng phn phi c nh ln cn nhau (trong vng 2,5 Km) to thnh mt vngng dy chung c coi nh mt n v.

- Mt ng dy chung kt ni 200 i c lp t dng chung gia cc vng phn phicnh trong phm vi mt vng ng dy chung.

- Mt ng dy d phng chung 100 i, thm vo ng dy chung c dnh ring chomt cp feeder, p ng nhu cu t xut cha c d kin trc.

Cc ng dytng i cnh

Cc ng dy chung (200 i chomi vng ng dy chung)

Cc ng dychung (100 i)

Cc t cp

Cc vngng dy chung

Cc vngng dy chung

MDF

Hnh 1.6: Phng php phn phi cp feeder cin


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- Mt t cp c t ti im feeder hnh thnh nn mt nhm ng dy hon chnh tonn t cp feeder v cp phn phi ngn chn s gia tng ca suy hao chn vo (insertionloss) trong cc ng dy chung a kt ni.

Phng php phn phi cp feeder FD

Phng php ny c mt sc im nh sau:

- Mt dung lng phc b sung x l bin ng nhu cu da trn csnhu cu tngtrng trong 2 nm (trc y l 5 nm), mt khong thi gian trung bnh k t khi lp khoch n khi bt u cc dch v.

- Cc si cp c chia s mt cch linh hot gia cc vng phn phi chung thng qua phnphi lin kt bao gm cc dy ph, v dy ph khng phi l dy a kt ni.

Theo quy tc chung, cc t FD c trang by cc giao din gia mng cp feeder vcp phn phi c t ti cc im feeder ci thin kh nng thi cng cho phn chia dy cp

v hot ng bo dng.Tnh ton s lng cpS lng cp quy hoch cho mi ng knh dy =

max

1515

N

nn

+

Trong : n15 s lng cc chm cp cn cho nhu cu trong thi gian 15 nm.

n15 s lng cc chm cp tng ng vi cc thay i nhu cu c c t sgia tng nhu cu trong 15 nm.

h s thch hp dy cp.

Nmax s cc i ca nhm cp c th thch hp trong mt cp.

1.7 CC DCH VC MNG TRUY NHP H TR1.7.1 Gii thiu

S xut hin cc dch v vin thng mi c th tng t nh s xut hin cc phn mmng dng sau khi my tnh c nhn c s dng. Tuy nhin, s pht trin ca cc dch v vinthng i sau s pht trin ca cc phn mm ng dng cho my tnh c nhn.

Hnh 1.7: Phng php phn phi cp feeder FD

Cc ng dytng i cnh

Cc vng

ng dy chung

Cc dy ph

Cc t cp FD

MDF

Cc vng

ng dy chung

Cc dy phCc dy ph

lin kt


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Cc dch v vin thng lc u pht trin chm tr l do ngh rng chng phi c iukhin tp trung bi cc nh khai thc vin thng. Nhiu dch v vin thng tin tin ban u dnh c cung cp bi nh khai thc vin thng thng qua cc tng i s th nay c cung cpbi chnh cc my in thoi.

Mc d khi u c chm tr, nhng s pht trin ca dch v vin thng r rng. Dchv ph bin nht cho khu vc dn c rt c th l gii tr video, vi nhng hng dn chngtrnh c tnh tng tc v s la chn theo nhu cu t nhng th vin giu chng trnh. Dch vnhu cu mua sm ti nh v cc dch v ti chnh cng hnh thnh.

S pht trin dch v vin thng c ngha x hi nht c th l giao tip t xa, iu khint xa, l dch v cho php con ngi lm vic ti nh, v internet - l dch v cho php conngi truy nhp thng tin bt cu trn ton cu. Truyn thng n gin trn ton cu c thc phc v tt hn bng thin t. y l mt dch v nhanh, n gin khng cn thi gianthc.

1.7.2 VoDDng nh s khng tha mn ang ngy cng tng i vi cc dch vc cung cp bi

truyn hnh CATV. S ph bin ca vic thu video cho thy hai iu l khch hng (thu bao) rtthch th c nhiu dch v v c iu khin mnh thng qua vic sp lch ca h hn l c htr bi pha truyn hnh cp. Cc dch v video trong tng lai khng chc da trn kiu phtqung b trn t lin thng thng, v ph v tuyn sn c l hn ch v c th tm cch s dngtt hn ngun ti nguyn hn ch ny. Tng lai ca video dng nh l cng vi cc h thng vtinh hoc vi cc mng truy nhp c mt csh tng cnh, hn l truyn hnh qung b thngthng hoc kiu phn phi bng cp khng tng tc thng thng.

VoD thc t l mt dch v thu video in t, nhng c nhng u im l a ra yu cungay trn mn hnh, c ngay tc th, iu khin ging nh cc u video (VCR), khng c nhngkh khn do nhng b phim ni ting u ang c cho mn chiu. Vic s dng cc tiuchun nn MPEG v truyn dn ADSL cho php cung cp cc video cht lng VCR trn hu htcc i dy ng hin c. Dch v cht lng cao hn c thc cung cp trn nhng ngngn hn hoc tuyn truyn dn c b trbng cc nt tch cc. Vic s dng cc i dy ngcho VoD c th l mt chin lc mu hiu qu, v n s dng csh tng ang c. Nhngn cha chc l mt gii php lu di bi v n khng cung cp c cht lng truyn dn tttrn tt c cc ng truyn nu khng c cc nt tch cc xa, m nhng nt ny s gy tn kmchi ph bo dng.

VoD c th bao gm cc ng dng nh sau:

MoD (Movies on Demand): y l mt dch v VoD u tin, cho php mt thu bao nh ringyu cu bt k b phim no t th vin lu tr phim rng ln. Dch v ny tng t nh vicchn ra mt b phim t b lu tr video o, khng c s kh khn nhi vi b lu tr videotht, thu mn mt b phim v ri tr li bng VHF hoc a DVD vo mt ngy khc.

SVoD (Subscription Video on Demand): l mt loi thu bao c k hn ca VoD, cho php khchhng xem c tt c ni dung chng trnh trn mt knh c ph thng qua lch chng trnh cakhch hng. V d, ton b ni dung chng trnh ca knh HBO trong thng 10 c lu tr trncc a VoD. Vi mt t cc ph hng thng cng thm, cc khch hng HBO c th la chn


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mt dch v nng cao (HBO SVoD) cho php xem bt k chng trnh no ca HBO trong thng. Dch v ny cho php thng thc theo chng trnh sp xp ca ring khch hng.

PVR (Networked Personal Video Recorder):PVRang dn tr thnh ph bin ghi hnh ccchng trnh biu din trn tivi v cho php xem li trong thi gian sau . Mt PVR tch hp vimt a cng trong mt STB (Set Top Box) ghi cc chng trnh dng nn tn hiu s rixem li sau .

V cu trc VoD bao gm ba dng cu trc:

Centralized VoD

Distributed VoD

Hybrid VoD


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1.7.3 Video trn ATMATM c mt s ngi xng l h tng cbn cho VoD bi tnh linh hot ca n.

ATM c thc m t nh l cng ngh c kh nng cung cp cc dch v trong tng lai, biv ATM khng hn ch bng thng. Mt khc, n c xem nh l mt gii php chp nhn tnhkhng chc chn v bn cht ca mt dch v VoD, v chi ph ca vic s dng ATM c thcloi b nu bn cht ca dch v ny r rng. Ngi lc quan c th xem vic s dng ATM lvic lm y cm hng. Cn ngi bi quan c th so snh n vi vic mt ngi sp cht ui vphi cc.

Mt trong nhng u im ca ATM l n cung cp mt ti mang chung c lp vi phngtin vt l c s dng trong mng truy nhp. iu ny cho php tch cc dch v ra t phngtin vt l, cho php thay i phng tin vt l m khng cn thay i phng tin dch v.ATM c th cung cp gi tr gia tng l nhn c kh nng cung cp mt csh tng chung chomt s dch v khc nhau v lm n gin s tin trin ln cc dch v bng rng tc cao hn.

Mt u im na ca ATM l n cho php ti thiu phn bng thng mo u cn cho bohiu, v khng cn dnh ring mt knh c dung lng cnh cho bo hiu m thng l khng

hot ng. iu ny trnn quan trng hn nu mt s lng ln cc dch v tc bit thp cnc h trng thi. Mt gii php thng thng hn kt hp cc knh bo hiu c thavo mc tng tc cao hn gia cc dch v, nu nhng yu cu bo hiu ca mt trong s ccdch v tng t ngt. Tuy nhin ATM cng c th chu ng nhng vn tng tc, v n sdng phng thc ghp knh thng k.

Sau y ta xem xt mt gii php Video trn ATM SVCs ca Cisco MC3810:

Video trn ATM m rng cc kh nng ca b tp trung truy nhp a dch v Cisco MC3810 cung cp tnh hiu qu v chi ph, nng ng, v h trdch v hi ngh truyn hnh mtcch linh hot. S dng plug-in VDM cung cp mt giao din quay s RS-366 n b H.323video codec, Cisco MC3810 tip nhn mt cch tng cc yu cu quay s ra ngoi t h thngvideo. B codec kt ni n mt trong cc cng ni tip ca Cisco MC3810 v cng ni n cngquay s ca Cisco MC3810.

Hnh 1.8: Mt v dng dng video trn ATM

1.7.4 Qung co theo nhu cu mua bn t xa


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Nhng dng ban u ca mua hng ti nh n gin gm nhng qung co qung b kthp vi vic t hng bng in thoi, th tn dng v gi th, vi phng thc truyn thngthng thng qua mng truyn hnh cp.

Mt phng n hiu qu hn l to ra nhng chng trnh qung co ph hp cho tng itng khch hng. iu ny c thc hin theo mt cch hn ch bng vic ln lch qung co ph hp vi ni dung chng trnh. i vi mua sm ti nh tinh vi phc tp hn, th vic phtqung b hoc pht trn din hp nhng chng trnh qung co c thay bng s truy nhptng tc, hoc l thng qua s la chn cc ti liu qung b hoc l thng qua vic xem ltbng video cc ca hng o.

Kiu mua sm ti nh ny c thc nh gi qu cao. N c th hiu qu hn cho nhngcng ty t hng bng th hin c gi i cc tp ch ca hdng a CD.

Mc tnh vi phc tp tip theo, v c l dng kh thi u tin ca mua sm t xa, loi bvic phn pht bu phm bu kin. Tuy nhin vic ny s vn cn i vi hng ha vt l, v cngngh c kh nng vn chuyn t xa nhng hng ha ny ti ch ca chng vn cha kh thi. Vicloi b phn pht bu phm bu kin trnn kh thi trong nhng trng hp nht nh m

hng ha c phn pht cha thng tin. Dch v VoD l mt dng thng tin c mua bn, mcd thng thng n khng c coi l nh vy bi v thng tin khng c lu tr. m nhccng c thc phn pht theo cch ny, v i vi m nhc th vic lu tr nghe li sau nyc th thch hp hn, v m nhc thng c nghe li thng xuyn hn cc chng trnh video.Tuy nhin, trong c hai trng hp vic truyn d liu i lu tr v nghe hoc xem li sau thng d hn l pht d liu i hin thch thi gian thc, v nhng trngi v tr vhin tng trt s t hn.

1.7.5 Cc dch v internetNhng dch v cbn c internet cung cp l thin t gia nhng ngi s dng, truy

nhp t xa vo cc my tnh khc, v truyn file n hoc t cc my ch. c bit, internet chophp truy nhp thc hin truyn thng ton cu vi chi ph ca mt cuc gi in thoi ni htti my ch, v chi ph thm ch cn t hn nu ngi s dng c ni trc tip vi my ch.Thin t cng l dch vc s dng ph bin rng ri bi v n nhanh v cho php truyn ivn bn hoc cc ti liu c m ha ph hp gia cc my tnh khc nhau. Vi s pht trin ccng lin kt siu vn bn v vic to ra World-Wide Web (www) v nhng trnh duyt tinh vi,lm cho internet trnn d truy cp hn vi nhng ngi bnh thng.

S tng trng ca lu lng internet phn no l do nhng ngi mi s dng mun khmph internet, cn nhng ngi ang s dng c th thay i phng thc lm vic nn s dngnhiu hn. Nhng yu t ny cng c thc tng ln bi tnh d s dng ca nhng cng c c

tnh thn thin vi ngi dng.1.7.6 Hc t xaHc t xa l mt thut ng chung dng ch vic s dng vin thng cho gio dc. N

thng c mt yu cu truyn dn bt i xng tng t nh VoD, v cn truyn nhiu thng tinti cc ngi hc hn l nhng thng tin nhn t h. dng n gin nht, hc t xa khng cng nhiu hn VoD vi mt ni dung c tnh gio dc. Mt dng tinh vi phc tp hn s cho phptruyn cc bi ging ch thi gian thc n ngi hc v cung cp cho h kh nng a ra


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nhng cu hi thng qua in thoi hi ngh nh l hang c mt trong cng mt phng hc.Ty thuc vo s trin khai, c th tt hn nu cc cu hi a ra c nh vo my hn l ni,v m thanh hi nght ra nhng kh khn cho cc mng my tnh. Truyn thng tng tc cvit ra c thm nhng u im l diu khin hn v to ra nhng bng ghi xem li sau ny.

Bng thng yu cu cho mt bi ging hoc mt bi trnh by t hn bng thng yu cu chomt dch v VoD, v thng tin c trnh by khng thay i nhanh chng. Mt quy tc i vingi trnh by l cho php 2 pht cho mi slide ni v ch ra nhng kha cnh quan trngbng mt con tr. Bng thng cho vic ny nh hn t nht hai ln so vi bng thng cho videothng thng. Nhng tc d liu c th d dng cung cp c bng mt tuyn truyn dnISDN bng hp. Cng ngh cbn truyn cc bi ging cho mt phm vi hp ngi s dng c th nghim qua internet, v nhng loi modem tinh vi phc tp hn s cho php cung cphc tp t xa thm ch thng qua truy cp internet trn nhng ng dy tng t hin c.

1.7.7 Cc dch v cnh boCc dch v cnh bo c thc c trng bi tnh tng t vi cc dch v khn bo

cng an, cu ha v cp cu. Dch v cnh bo pht hin trm khc vi nhng dch v cnh bo

cu ha v cp cu, v nhng tn trm c th lm mt tc dng ca cnh bo ny. Cc tnh hungcu ha v cp cu khng c gng lm mt tc dng ca dch v h trcho cnh bo. Mt dch vcnh bo phi pht ra mt tn hiu cnh bo nu truyn thng b mt hoc b can nhiu, v n cnphi pht hin s lc li tm kim ca nhng tn trm. iu ny cng hu ch cho cp cu v cuha, v la c th lm cho cc thit b truyn thng khng hot ng c, v s mt ngtruyn thng c th gy nguy hi n sinh mng ca con ngi trong trng hp cn c cp cu yt.

Mt trong nhng vn ln nht i vi cp cu v cu ha l vic xy ra nhng cnh bosai. c bit, mt s ngi s dng cnh bo y t ch th chng m khng ch n hu quxy ra. iu ny c chn li bng mt th tc xc nhn chc chn. V d, gi in cho ngi s

dng khng nh rng cnh bo l c tht. Tuy nhin, vic xc nhn li nh vy gy ra chmtr m c th l mm mng ca cc tnh hung cp cu v cu ha, cng nh b phn tc dngnu vic chm tr cho php kt nhp bt gi ngi s dng .

Nhng tn trm cng c th chng to ra mt dng cnh bo sai lm chm tr thmcho nhng ngi c trch nhim khi nhng cnh bo thc xy ra. Trong nhng tnh hung ccoan, chng thm ch c th tn cng mng truyn thng sao cho mc tiu c th ca chng khngb pht hin. trnh nhng vn nu trn ngi ta s dng truyn thng v tuyn c bo vchng nhiu. Cc h thng v tuyn ny thch hp cho cc cnh bo y t di ng v d dnntonglp t.

1.7.8 Cc dch v trang vngCc dch v trang vng dng nh c nhng yu cu v bng thng cao nht trong tt c

cc dch v vin hnh, v chng lin quan n vic trnh by thng tin ti khch hng. Chng khcvi gii php thng thng dng cho mua sm ti nh l dch v c ngun gc t video qung b.Cc dch v trang vng in t c th lm chi tit hn phng php trang vng trn giy thngthng, v chng c th cung cp nhiu thng tin hn bng nhng sn phm c th. Kiu truynthng ny cn cho php a vo phng thc bn l khng cn kho cha hng, ngi bn l


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c th x l n t hng v sau t mt t cc n t hng vi kho ca ngi phn phichnh, nh ngi bn l khng gi mt kho hng vt l.

1.7.9 Cc dch v cho nhu cu thit yuCc dch v vin hnh yu cu cho cc nhu cu thit yu (gas, nc, in, v vin thng)

cn c xem khc vi cc sn phm khc c bn cho khch hng, v chng yu cu bng

thng thp hn v h trcho cc chc nng khc nhau. Chc nng hin nhin l c cng-ttxa, v iu ny trnh c chi ph c nhn vin n tn ni lm vic ny. N cn c th h trlp ha n trc tip. Dch v ny khuyn khch vic thanh ton cc ha n ngay lp tc v vth li tc tit kim c l mt ng cmnh cho cc cng ty tin ch. Lp ha n in t trctip c th cn r hn so vi phng php lp ha n thng thng, v khng cn gi ha nbng ng th. Cn n gin hn na nu vic thanh ton cng c thc hin theo phngthc in t. Tht mu thun khi chnh cc nh khai thc vin thng khng tn dng s titkim ny gim chi ph ca h trong vic lp ha n cc ph cho khch hng.

Cn c nhng u im i vi vic qun l nhu cu v cc mt hng (dch v) tin ch, cbit i vi in, v kh c th lu trc in. Vic qun l nhu cu c tht c bng vic

iu khin trc tip s tiu th nhdch v vin hnh hoc l bng iu khin gin tip thng quavic thng bo v nhng thay i cc ph. Phng n sau c thc tch hp vi mt iukhin thng minh t ti cc gia nh, n c th tnh ton sao cho vic mua bn thi im no lc li cho khch hng nht.

1.8 CC TIU CHUNMt vi t chc tiu chun sau y chu trch nhim v s pht trin cc tiu chun truy

nhp.1.8.1 ADSL/VDSLTiu ban T1E1: T1E1 l mt hi vin ca Vin tiu chun quc gia Hoa K (ANSI). Trong ccc nhm:

1. T1E1.1 Cc truy nhp vt l v cc truy nhp tng t2. T1E1.2 Truy nhp bng rng3. T1E1.3 Truy nhp in v quang4. T1E1.4 Truy nhp DSL5. T1E1.5 Cc h thng ngun6. T1E1.7 Bo an vin7. T1E1.8 Bo v vt l v thit k

ADSL Forum: Din n v ADSL ra i cui nm 1994 nhm h trcc cng ty in thoi. Ccng dng ca n em n mt tim nng th trng ADSL to ln. Vi gn 300 thnh vin,trong c cc thnh vin cho v cc lnh vc vin thng, networking, v cng ngh thngtin. Din n ADSL c chia thnh 7 nhm:

1. ATM over ADSL2. Packet over ADSL3. Giao tip v cu hnh CPE/CO


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4. Operations5. Qun tr mng6. o th v tng tc hot ng7. H trnhm nghin cu VDSL

1.8.2 Cable Modem/HFCCc t chc tiu chun, din n, v hip hi sau y chun ha cable modems trn nn

HFC:

1. SCTE2. MCSN3. IEEE 802.144. CableLabs5. ATM Forum6. DAVIC

1.8.3 DOCISD n DOCIS i din cho cable industry system operations, cung cp dch v cho phn ln

thu bao cp Bc M. D n DOCIS cung cp cc c trng giao tip cho cable modems v linkt cc thit b trn nn HFC. M hnh tham chiu cho d liu trn h thng cp c thit lp, nbao gm cc phn t truyn thng s cng nh cc hot ng cn thit v cc phn t h trtrongthng mi nh lit k sau y: Bo v, cu hnh, thc hin, li mng, k ton v qun tr.

1.8.4 IEEE 802.14Nhm IEEE 802.14 to ra 3 nhm ph : PHY SWG, MAC SWG, v kin trc SWG.

PHY SWG: c y nhim pht trin tiu chun cho lp vt l ca cable modem. Cng b cah nhm m rng s m ha iu ch, trong cng phi ti u ha tc truyn bit, hiuqu, BER, v kh nng h tr trn MAC a truy nhp theo Tree-branching c ly xa c nhiungi s dng.

MAC SWG: c y nhim pht trin tiu chun cho lp MAC ca cable modem.Kin trc SWG: c giao nhim v gim st cc lin kt, tng tc hot ng bn trong, vcc giao tip chc nng gia MAC SWG v PHY SWG. Kin trc SWG cng c pht trin trnm hnh tham chiu OSI cho cable modem v kin trc dch v phn lp ca n da trn MAC vPHY.1.8.5 CableLabs

CableLabs thc hin cc d n R&D do cc thnh vin chnh hoc cc nhm thnh vin,v cng chuyn giao cc cng ngh c lin quan n cc thnh vin ca n. CableLabs cng tcvi computer industry pht trin cc mng cp s HFC. T chc ca CableLabs c xy dngxung quanh cc hot ng nh sau:

Truyn hnh tin tin: ph trch cc cng ngh truyn hnh mi (nn hnh, HDTV). Cc d n, cng ngh, hot ng: ph trch ton b hot ng c lin quan n ban hnh

cc mng CATV.


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u t v thit k kin trc mng: ph trch vic thit k kin trc mi (PCS, SONET,hubs, ...).

Ging nh Bellcore, CableLabs khng l thnh vin ca ANSI. Do vy nhim v caCableLabs khng to ra cc tiu chun, nhng cc i l s dng CableLabs kim tra s phhp khi tip cn cc vn k thut cng nh cc tiu chun i vi th trng CATV.

1.8.6 ATM ForumATM Forum c thnh lp nm 1991, l mt t chc quc t phi li nhun nhm mc ch

thc y vic s dng cc sn phm v dch v ATM nhvo s hi t nhanh ca cc c tnh kthut c tnh lin kt hot ng c vi nhau. Nm 2004, ATM Forum lin kt vi MPLS vFrame Relay hnh thnh nn MFA Forum.

ATM Forum khng lin kt vi bt k t chc tiu chun no. C mt vi MOU thit lpnn nh l ITU, IETF, v cc t chc khc.

ATM Forum cng hnh thnh ra RBB Working Group vo thng 2 nm 1995. Nhm nyc c trch l a ATM n tn nh ca ngi s dng.

ATM Forum cn c cc nhm lm vic khc, bao gm 14 nhm sau y:

1. SIG P-T-P v P-T-M Siganaling Point-to-multipoint2. SAA Services appects and application3. TM Traffic management4. B-ICI Interoffice interface ; +PNNI/B-ICI IW5. PNNI Private NNI interface specifications6. NM Network Management (M4, M5 interface specifications)7.

RBB Residential Broadband services

8. MPOA Multiprotocol Over ATM9. PHY Physical Layer10.LANE LAN Emulation11.Testing Testing (PICS)12.Security Security13.VTOA Voice Telephone Over ATM14.WATM Wireless ATM


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GII THIUMng cp ni ht v ang ng mt vai tr quan trng trong mng

thng tin lin lc ni chung v mng truy nhp ni ring. Cc vn cu to cady dn, kt cu ca mt si cp c nhng nh hng quyt nh n cht lngthng tin lin lc.

Tn hiu truyn trn cc i dy trong si cp khng ch c tn s thpnh tn hiu in thoi truyn thng, m cn c cc tn hiu tn s cao, tc ln ca cng nghng dy thu bao s. Do , cn phi xem xt cc nhhng ca tn hiu tn s cao nh cc hiu ng b mt dy dn, hiu ng lncn, hiu ng kim loi,

S pht trin phong ph cc dch v vin thng i hi cc thnh phnthit b mng truy nhp a dng hn rt nhiu, t cp kim loi i xng, cpng trc, cp quang, v tuyn v cc thit bu cui nhin thoi truynthng, cc u cui s, my tnh, v cc u cui a phng tin khc.

Vn bo dng o th mng truy nhp cng yu cu k thut cao hn c th duy tr hot ng tt cc dch v.


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2.1 CP KIM LOI I XNG2.1.1 Kt cu cp i xng

Kt cu ca mt si cp ty thuc vo yu cu khai thc, mi trng lp t m c rt nhiudng khc nhau.

Nhng chung qui c cc yu cu sau: Bn vng v chc v ha hc.

Truyn dn tt, t tiu hao nng lng tn hiu, c kh nng chng xuyn nhiu gia ccmch cao, chng c snh hng xuyn nhiu t cc ngun ngoi lai.

Tn t nguyn vt liu, nht l kim loi mu.

D thi cng lp t, s dng v bo qun.

m bo c cc yu cu trn l do kt cu cng nh k thut ch to si cp quytnh.

Cp i xng c s dng truyn tn hiu m thanh, hnh nh, hoc d liu. Chng gmhai si bc cch in xon li vi nhau.

Nhn chung cp i xng c ba phn t kt cu cbn l:

Dy dn.

Cht cch in gia cc dy dn.

V chng m.

Ngoi ra ty thuc vo ch khai thc v mi trng t cp m cn c: V gia cng,lp bao che in t.

2.1.1.1 Kt cu dy dnDy dn c mt yu cu cbn l phi dn in tht tt, ngha l in trcng nh cng tt,

song yu cu cng phi dung ha vi mt iu kin khc l s dng vt d kim v r tin.Chnh v vy m ng l kim loi lm dy dn rt ph hp.

Trong ch to c hai loi dy ng l cng v mm. Dy rut cp u c cu trc hnh trtrn, vi yu cu ng knh phi u mt ngoi phi nhn.

Ty theo yu cu s dng m ng knh dy dn c cc c khc nhau t 0,4 mmn 1,4 mm, nhng thng dng nht l c0,4 mm hoc 0,5 mm cho ng dy in thoi trongthnh ph.

Cu trc dy dn cng ty thuc vo yu cu s dng, c th c cc loi sau y: dy dn cv trn, dy dn bn, dy dn lng kim, v dy dn c nhiu si xon quanh mt si to gia(hnh 2.1)

Hnh 2.1: Cu trc dy dn ca rut cp


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2.1.1.2 Cht cch inKhi ch to cht cch in cho dy dn, cc nh ch to tp trung quan tm n cc yu

t sau:

Cht cch in tiu hao nng lng tn hiu nhiu hay t, v do c ly thng tin c rtngn hay ko di. c bit i vi cp truyn tn hiu cao tn th yu t ny cng quan

trng. in trca cht cch in cng ln th thnh phn dng in r gia hai dy dn gn

nhau s cng b. Ngi ta mong mun cht cch in c in trbng v cng ln, nhngthc t rt kh thc hin c.

in p xuyn thng ( E ): cht cch in cng chu c mt in p cng ln, chng tvt liu cng bn vng vin.

in trsut ( ): thng s ny c trng cho mc chuyn i cc ion trong cht in

mi. in trsut cng ln th mc chuyn di cc ion cng nh, l iu ta mongmun.

Hng s thm thu ca in mi ( ): thng s ny c trng cho dy ca lp in mib phn cc trn b mt ca n khi c tc dng ca trng in t.

Lng tiu hao ( tg ): i lng ny biu hin s tiu tn nng lng ca trng vo vic

xoay chuyn cc phn t lng cc in ri khi v tr ban u ca n. Trong l gc

chuyn di , cng ln chng t cc phn t lng cc in c xoay mt gc ln,ngha l tiu hao nng lng trng cng nhiu.

Cc thng s E , , , v tg ni trn dng lm tiu chun chn dng cht cch in

cho tng loi cp theo yu cu s dng ca n.

Trong ch to ngi ta thng dng cc vt liu cch in nh: polyethylene (PE),polyvinyl chloride (PVC), fluorinated ethylene propylene (FEP), si thin nhin, t nhn to,giy. Cc kt hp ca nhng vt liu ny thnh thong cng c s dng. Mt s kt hp cbit l gia cc lp cch in c bm khng kh, bi v ta bit rng khng kh l mi cht cchin rt tt.

Vic chn la cht cch in no khng chnh hng n kch thc vt l ca si cp mcn quyt nh n hai trong bn c tnh in ca si cp, l in dung (C) v in dn (G).

in dung (C) khng ch ph thuc vo vt liu cch in m cn ph thuc vo dy calp cch in. Cn in dn (G) chc quan tm khi truyn tn hiu tn s cao. Tuy nhin, cc tn s nh vy th in dn cng gp phn ng k vo suy hao ca cp.

Cht cch in c nh hng trc tip n tc lan truyn ca tn hiu trong mt mchdy. Thi gian truyn tn hiu tim ny n im kia trong mch dy c gi l tr lan truyn,khc vi tr lan truyn gia cc i dy trong mt si cp, c bit nh l lch ca tr.

2.1.1.3 V chng m v gia cngV chng m c th lm bng kim loi hoc nha. Cp hin nay c v chng m l nha

dai, bn. dy lp v chng m ty thuc vo loi cp v kch thc cp. Ni chung khi chn


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la vt liu lm v chng m cho cp phi da trn cs: kh nng lm phng b mt, kh nngchu ng thi tit, tnh bc chy, kh nng mu sc, kh nng in n. tn s cao, v bc ngoicng gy ra lm phin toi cho cp. C th tham kho vi vt liu lm v bc ngoi bng sauy:

Vt liu Kh nngmu sc Kh nng lmphng b mt Tnh bcchy Kh nngin n Gi thnhPVC Xut sc Tt Kh kh Xut sc Thp-trung bnh

Polyethylene Tt Rt tt Rt kh Tt Trung bnh

Polypropylene Tt Rt tt Rt kh Tt Trung bnh

FlamarrestTM Tt Kh tt Rt d Xut sc Trung bnh cng

TeflonTM Kh tt Xut sc Rt d Rt xu Cao

c tht cp nhng mi trng nh vch ni , di lng sng, lng t v bin, thcp cn phi c thm mt lp v nha, l v gia cng.

C ba loi v gia cng (hnh 2.2) thch ng vi mi trng t cp khc nhau l:

- Loi qun hai bng st l (a): cp c gia cng nh vy ch yu chn trc tip di lng

t.

- Loi qun bng cc si st dt (b): cp c gia cng nh vy dng t nhng ni hayb chn ng mnh v nhng sn ni khng th chn xung c, hoc chn theosn i dc 450 trxung.

- Loi qun bng cc si st trn (c): cp c gia cng nh vy dng th di nc.

Hnh 2.2: Kt cu v gia cng ca cp2.1.1.4 Mng bao che

Bn cnh vic xon dy, chng ta cn bo v tn hiu trnh b nhiu bi cc i dy bncnh, hoc tn hiu, nhiu t bn ngoi xm nhp vo. C ba loi mng bao che cbn l: xonc, bn, v bng kim loi.

C su l do khi la chn mng bao che:

Mc bao ph (coverage).

mm do (Flexibility). bn khi phi un nn nhiu ln (Flex life).

Tm tn s hot ng (Frequency range).

Nhiu in ma st (Triboelectric noise).

Xuyn knh gia cc i dy (Multipair crosstalk).


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C ba cch bao che cbn trong si cp l: phn i (a), theo lp (b), v theo chm (c).

2.1.1.5 Nhng quy lut xp t b dy rut cpMt vn rt quan trng l cu trc ca li cp, cc i dy trong si cp phi c sp

t sao cho lm nh tit din si cp, d dng nhn bit, hn chn mc thp nht nh hngca trng in t ca dng in tn hiu gia mch dy ny vi mch dy khc, t gim nhc xuyn nhiu.

sp xp c qui lut, ngi ta thc hin nhm dy. C bn cch nhm dy c bn(hnh2.4) l: nhm xon i (a), nhm xon hnh sao (b), nhm xon i kp (c), v nhm xon

sao kp (d).

Khi nhm dy nh vy th ng knh ca cc nhm xon c tnh nh sau:

ng knh dy dn k c cht cch in

[ ]mmg

gdd

01

1001

1+= (2.1)

Vi: d0 ng knh dy kim loi [mm]

0 t trng ca vt liu lm dy dn

1 t trng ca vt liu cch in

0g trng lng ca dy dn kim loi trn n v di

1g trng lng ca cht cch in trn n v di

ng knh nhm xon i

Ta c:Di= d1 + bd, m bd = x nn:Di= d1 + x

Ta c: d12 = 2x2 , suy ra: x = d1/ 2

Suy ra: Di= d1 + d1/ 2 =1,71 d1

Hnh 2.3: cc dng sp xp mng bao che

Hnh 2.4: Mt ct ca cc kiu xon dy cbn trong cp


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ng knh nhm xon sao 4 si

ng knh nhm xon i kp

ng knh nhm xon sao kp

Trn y ch mi cp n kt cu ca nhm dy cbn. Ta cn phi xem xt s sp xpcc nhm dy cbn y trong b dy rut cp. C bn loi sp xp cc nhm dy cbn sau y:

ng nht theo chm: Cc nhm dy cbn xon chung mt dng theo tng chm, chng hn ttc xon i, hoc tt c xon hnh sao thnh tng chm. Trong mi chm bao gm t 50 n100 nhm cbn, mi nhm trong chm c xon theo bc xon khc nhau. Loi sp xp nythng dng cho cp c dung lng ln.

ng nht theo lp: Cc nhm dy cbn xon chung mt dng theo tng lp, chng hn tt cxon i, hoc tt c xon hnh sao thnh tng lp. Loi sp xp ny c qui lut hn. Ty vodung lng cp m n bao gm lp trung tm v nhiu lp pha ngoi. Cng ra ngoi s nhmtrong lp cng ln. Hai lp st nhau c xon ngc chiu nhau.

Hn hp theo chm: Cc nhm dy cbn va c loi xon i va c loi xon sao, c xonvi nhau thnh tng chm.

Hn hp theo lp: Cc nhm dy cbn va c loi xon i va c loi xon sao, c xon vinhau theo lp.

2.1.2 Xon dy trong cp ng2.1.2.1 i dy xon nguyn bn

Vo nm 1877, Alexander Bell ni in thoi qua ng dy st n v ly t lm ngv ca mch in. Phng php ny truyn dn rt km khi kh hu kh ko di.

Sau vn ny c gii quyt bng cch s dng i dy trn cng song song cchnhau vi cm. Phng php ny cung cp ng trv ca tn hiu in tin cy hn. Tuy nhin,khi ng pht hin ra hin tng xuyn m, v cng bit c rng xuyn m c th gim theochu k bng cch thay i v tr bn phi v bn tri ca dy dn.

Bell pht minh ra i dy xon vi nhau. Vi bc xon va , nng lng in ttrng trn mi phn nh ca dy b trit tiu bi nng lng bao quanh phn nh ca dy tiptheo.

Ta c:Di kp = 1,71 Di=1,71.(1,71 d1) = 2,92 d1

Ta c:

Dsao kp= 2,41Di= 1,71 (2,41d1) = 4,12 d1


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Khi thit k cp vin thng, ngi ta trnh chn si cp c hai i c bc xon bng nhautrong nhm 25 i cp. Vic xon dy ny ci thin ng k s mt cn bng in dung v hiung in t trng, lm ti thiu nhiu v xuyn knh c hi. iu ny i hi ngi thit k cpphi quan tm c bit n vic xon ca cc i dy.

2.1.2.2 H s xonSau khi xon, di thc t ca si dy ln hn khi cha xon. V th m cc tham sin

kh ca mch dy c s thay i. tnh ton cc tham s sau ny cho chnh xc, ta cn xc nhh s xon. H s xon cng ni ln di thc ca mch tng ln bao nhiu ln so vi dica cp.

xc nh h s xon, ta gi thit, c mt si dy qun theo trc qun, trc ny c ngknh D1.

Ta dng hai mt phng ct, ct vung gc vi trc qun ti hai im khi u v kt thcca mt bc xon. Kt qu l tit din ct i vi trc xon l hnh trn, i vi dy qun lhnh elip.

Sau dng mt mt phng ct khc b dc trc qun (mt phng ny vung gc vi haimt phng trc), v tri mt ct ny trn mt phng, ta c hnh v sau:

Trong :

L l di dy qun ca mt bc xon.

H l di bc xon.D1 ng knh trc xon. l gc hp gia dy qun trong mt bc xon vi mt

phng ct ti im kt thc bc xon.

T hnh v ta c:

( )21122

1sindDH

H

b

d

++==

(2.2)

Suy ra:( )

2

2

11

22

1

H

dDHdb

++=

t:( )

2

2

11

22

H

dDHK

++= v gi l h s xon. (2.3)

Nh vy ng knh ln ca tit din dy dn (hnh elip) l b=Kd1, cn di thc t dy dn

qun trong bc xon l: ( ) KHdDHL =++=2

11

22

(2.4)Nu mt nhm hai dy xon vi nhau th trc xon ca n c th hnh dung nh mt nt mnh n

mc ng knh ca n khng ng k, v lc : 071011 ,,H

LK ==

2.1.2.3 Bc cn bngTrong mt b dy c nhiu mch nn nhiu i dy c bc xon trng nhau, m bc

xon trng nhau th kt qu chng xuyn nhiu gia chng khng cn tc dng. Cho nn trn thc


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t: c hai mch gn nhau, xon theo bc xon no , chng hn nhm mt xon theo bc xonh1, nhm hai xon theo bc xon h2. Nu cc bc xon tha mn iu kin:

D

hhx;

D

h.hLS

2121 +== (2.5)

Trong : D l c s chung ln nht ca h1, h2, x l mt s nguyn l, v ==

8

1LS . Vi l

bc sng tn hiu c tn s cao nht. Nh vy sm bo cho hai mch st nhau nh hng quali l t nht, hay ni xon dy nh vy c hiu qu nht.

di LSc gi l on cn bng.

Ta xt mt v d sau y:

T hnh v, ta c mch mt c bc xon h1= 40mm, mch hai c bc xon h2= 50mm.

Do c s chung ln nht ca 40 v 50 l D=10. Vy di on cn bng 20010

5040==

.LS

v 910

5040=

+=x l s nguyn l; xon nh th l tt.

2.1.3 Cc tham s truyn dn ca mch dy cp2.1.3.1 S tng ng ca mch dy cp

Cht lng truyn dn trn mch dy cp thng tin v c tnh in kh ca n c trng bicc tham s : in tr(R), t cm (L), in dung gia hai dy (C), v in dn cch in giahai dy (G).

Cc tham s ny khng ph thuc vo in p v dng in, m chc xc nh thngqua kt cu mch, vt liu ch to v tn s ca dng in m thi.

V ngha vt l, cc tham s mch dy cp tng t nh cc tham s ca mt mch daong c hnh thnh bi cc phn t R, G v L,C.

Ch khc ch l cc tham s ca mch dao ng th tp trung. Cn mch dy cp cc

tham s R, L, C, G phn b trn mi im ca mch. Hnh v sau y l s tng ng camch dy cp bao gm cc tham s trn.

Hnh 2.5 : S tng ng ca mch dy cp


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y l s tng ng ca mt on ngn mch dy cp, v trn on y ta gi thit sphn b cc i lng R, L, C, G l u n. Trong cc tham s R v L phn b lin tc theochiu dc ca mch v hnh thnh tng trkhng:

Z=R+jL

Cn cc tham s G v C hnh thnh tng dn np ngang:

Y=G+jC

Khi truyn tn hiu trn mch dy, do c s tn ti ca trkhng dc v dn np ngang min p cng nh dng in gim dn tu mch in n cui mch. Do , cng sut ca tnhiu cui ng dy nh hn cng sut u ra ca my pht.

Trong bn tham s R, L, C, G th phn t gy ra tiu hao nng lng tn hiu chnh l R vG, nhng phn t cn li c c trng bi kho in v kho t, n tch t nng lng in t vsau li tr v ngun, cho nn L v C thng c coi l phn t tch phng nng lng.

Rc trng cho s tiu hao nng lng trong dy dn v nhng kim loi k cn.

G c trng cho s tiu hao nng lng trong cht in mi.

Bn tham s trn y c th coi n c trng y v bn cht ca mt mch dy.

2.1.3.2 Mch dy ng nht v khng ng nhtNi chung v khi nim mch dy ng nht v khng ng nht c mt v tr c bit khi

ta nghin cu s truyn dn tn hiu in trn mt mch dy.

Khi nim v sng nht c ngha hp l s phn b cc tham su n trn mi imca mch. Ngoi ra cn hiu khi nim l iu kin kt cu ca b dy rut, ngha l mi sidy li c cng chung mt iu kin in kh nh nhau hay khng.

Khi nim ng nht cn c mt nh ngha khc l : mt mch dy ng nht khi trkhng

ca ngun bng trkhng sng ca mch v bng trkhng ti.

Ngc li vi nhng khi nim l mch dy khng ng nht.

2.1.3.3 C s ca phng trnh mch dy ng nhtTa hy nghin cu mt mch cp ng nht thng qua cc tham s R, L, C, G ca n.

Trkhng ngun l Z0, trkhng ti l ZL, in p v dng in u mch l U0 v I0, inp v dng in cui mch l UL v IL.

T hnh v ta ly mt on mch v cng ngn l dx. Cch im u ca mch l x. Dngin truyn qua phn t mch dx l I v in p trn hai dy dn l U. T st p trn ondx l:


41/188


32

( )LjRIdx

dU+=- (2.6)

Dng hao ht trn on dx l:

( )CjGUdx

dI+=- (2.7)

Gii phng trnh (2.6) theo I ri thay gi tr I tm c vo phng trnh (2.7), ta c:

( )LjRdx

dI

dx

Ud2

2

+=- (2.8)

Thay gi tr cadx

dIt (2.7) vo phng trnh (2.8) ta c:

( )( )CjGLjRUdx

Ud ++=

2

2

(2.9)

t: ( )( )CjGLjR ++=

Vy: Udx

Ud.2

2

2

= (2.10)

Gii phng trnh vi phn cp hai (2.10), ta sc nghim ca n c dng tng qut l:

xx BeAeU += (2.11)

Ly o hm hai v theo x, ta c:

( )xx

xx

BeAe

eBeAdx

dU

=

=(2.12)

Thay (2.12) vo phng trnh (2.6), ta nhn c:

( ) ( )xx BeAeLjRI =+ Hoc k hiu:

CjG

LjRLjRZB

++

=+

= (2.13)

th:

xx

B BeAeIZ += (2.14)

n y ta c hai phng trnh vi hai n s A v B nh sau:

xx

B

xx

BeAeIZBeAeU

+=+= (2.15)

tm A v B ta li dng gi tr dng v p u mch (khi x=0) l I0 v U0, t phngtrnh (2.15) c vit:

BAZI

BAU

B +=

+=

0

0 (2.16)


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Suy ra:2

;2

0000 BB ZIUBZIU

A =

= (2.17)

Thay (2.17) vo (2.15) ta c:

xBxB

xBxB

eZIUeZIUI

eZIU

eZIU

U

++=

++

=

22

22

0000

0000

Thc hin bin i hai phng trnh trn vi ch rng:

Ta s nhn c in p Ux v Ix ti mt im bt k x no ca mch:

xshZ

UxchII

xshZIxchUU

B

x

Bx

00

00

=

=

(2.18)

cui mch tc l khi x=1 th:

11

11

001

001

shZ

UchII

shZIchUU

B

B

=

=

(2.19)

Gii phng trnh (2.19) theo U0 v I0, ta li c:

11

11

110

110

shZUchII

shZIchUU

B

B

=

+=

(2.20)

Cc phng trnh (2.18), (2.19), (2.20) cho ta quan h gia dng v p vi cc tham s R,L,C, G hoc vi v ZB. Qua , cho php xc nh c in p v dng in ti im bt k ca

mch, ty thuc vo in p v dng in u ca mch .

Cc phng trnh ng vi trng hp trkhng ca ngun v ti l bt k (Z0 v Z1).

Khi c s phi hp tc l khi Z0=Z1=ZB v U0/I0=U1/I1=ZB, th cc phng trnh (2.18),(2.19), (2.20) c dng n gin nh sau:

x

x

x

x

eII

eUU

=

=

0

0

110

110

eII

eUU

=

=(2.21)

xeII

eUU

=

=

01

101

2

2xx

xx

eexsh

eexch

=

+=


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34

T (2.21) ta c th suy ra dng hay dng hn c l:

xx eI

Ive

U

U

1

0

1

0 (2.22)

Nu li p dng cng thc P=UI th t (2.22), ta li suy ra:

12

1

0 eP

P

= (2.23)

Nh vy khi xt mch dy ng nht ta ln lt nhn c cc phng trnh (2.18),(2.19), (2.20) trong trng hp trkhng ngun v ti l bt k. Cn cc phng trnh (2.21),(2.22), (2.23) l trng hp trkhng ngun bng trkhng sng v bng trkhng ti.

ng thi chng ta cng rt ra mt kt lun l: t cc phng trnh dn ra chng t rng struyn dn nng lng trn ng dy th dng v p ti im bt k trn mch do hai tham sch yu ZL v ZB quyt nh, m hai tham s ny li ph thuc vo cc tham s R, L, C, G. Hayni cch khc chng ph thuc vo cc tham s R, L, C, G.

2.1.3.4 Nhng hin tng hiu ng khi truyn dng in cao tnHin tng hiu ng mt ngoi: i vi mtdy dn c lp, khi truyn dng in tn scao th mt dng in ngy cng dn ra phamt ngoi (dy dn hnh tr) trong khi tmdy dn mt rt nh. Tn s cng cao th mt dng in tm dy dn hu nh khng c.Hin tng nh vy gi l hin tng hiu ngmt ngoi.

l gii hin tng ny, ta xt dy dn nh hnh trn. I l dng chy trong dy dn. Ditc dng ca t trng H, pht sinh cc dng xoy. pha trc ca dy dn, dng xoy ngcchiu vi dng dn I , cn pha mt ngoi th chng cng chiu. Do , mt dng in I cphn b tp trung ra pha ngoi, cn tm dy dn th mt dng nh. Khi tn s cng cao, thhin tng ny xy ra cng mnh, kt qu l tit din dn in hu hiu ca dy dn xem nh bgim i.

Hin tng hiu ng ln cn: Xt hai dy dn hnh tr song song gn nhau, cng truyn dng incao tn th mt dng in li phn b tp trung v pha hai dy dn gn nhau, pha hai dydn xa nhau th mt dng in nh.

xt hin tng vt l ca hiu ng ln cnta xut pht t hnh bn. Khi dng in chy

trn hai dy dn c chiu nh hnh v, ttrng H do dng trn dy a gy ra, tonhng dng xoy Ibm trn dy b. pha gndy dn a, dng xoy Ibm cng chiu vidng chy I, pha xa chng c chiu ngcnhau. Kt qu l pha gn dy a, dng inl I+Ibm, pha xa dy a dng in l I-Ibm.Do , mt dng khi c hiu ng ln cn tp trung v pha hai dy dn gn nhau.


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35

Khi hai dy dn c dng in ngc chiu v cng chiu th qua hiu ng ln cn ta c thbiu din s phn b mt dng in trn tng dy dn nh m t trong hnh sau:

Hin tng hiu ng kim loi: Trn si dy dn truyn a dng in cao tn, th chung quanhdy dn y c mt trng bin i. Trong phm vi khng gian nht nh xung quanh n, nu tat nhng vt dn, th lp tc trn cc vt dn t vo s c nhng dng in xoy xut hin dotng tc ca ng sc t. Nhng dng in xoy y tiu tn i di dng nhit.

2.1.3.5 in tr

( ) ( )

( )

++=2

0

2

0

0

1

12

a

dKrH

a

d

KrpGKrFxRR [/Km]

Trong :

d0=2r ng knh dy dn [mm]a khong cch gia hai dy trong mt mch [mm]x h s xon (1,011,07)p tiu hao ph thm do xon dy. Khi xon i p=1 ; sao p=5 ; i kp p=2R0 in trca dy dn i vi dng mt chiu

Trong tnh ton ngi ta thng p dng cng thc:

S

lR =0 []

Trong :

in trsut [.mm2/m]. nhit 200C, vi dy ng: =0,01754; i vi dynhm : =0,0291.

l di dy dn [m]S tit din dy dn [mm2]

i vi dy dn hnh tr th 4

. 20dS

= ; d0 l ng knh dy kim loi [mm]

i vi mch hai dy th cng thc tnh in trmt chiu l:2

0

0.

8000

dR

= [/Km]

Sau khi xon dy th in trmt chiu c nhn vi h s xon x.

xd

R2

0

0.

8000

= [/Km]; x = (1,011,07)

+ ++


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nhit khc 200C:

( )[ ]20120 += tRRt [/Km]

Rt l in trnhit oR20 l in tr20

0C

l h s nhit in tr vi dy ng =0,004; vi nhm =0,0037; vi st=0,0046.

2.1.3.6 t cmCng thc tnh t cm ca mt mch dy cp i xng:

( ) [ ]KmHKrQr

raL /10ln4 4

+

=

Trong :

a khong cch gia hai dy trong mt mch [mm]d0=2r ng knh dy dn [mm] h s t thm

Tr s c cc hm F (Kr), G(Kr), H(Kr), Q(Kr),Kr F(Kr) G(Kr) H(Kr) Q(Kr)

0

0,1

0,2

0,3

0,4

0,50,60,70,80,9

11,11,21,31,41,51,61,71,8

0

0

0

0

0

0,0003260,0010,0010,0020,003

0,0050,0080,0110,0150,0200,0200,0330,0420,052

0

4

4

6

kr

4

4

6

kr

4

4

6

kr

4

4

6

kr

0,009750,002020,003730,006320,01006

0,015190,02200,03060,04130,05410,06190,08630,10550,1262

0,0417

0,0417

0,0417

0,0417

0,0417

0,0420,0440,0450,0460,049

0,0530,0580,0640,0720,0800,0920,1060,1220,137

1,0

1,0

1,0

1,0

1,0

0,99980,99980,9990,9990,998

0,9970,9960,9960,9930,9900,9370,99830,9790,974


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37

1,922,12,22,32,42,5

2,62,72,82,933,23,43,63,844,24,4

4,64,855,25,45,65,866,26,46,877,4

7,889101112

0,0640,0780,0990,1110,1310,1520,175

0,2010,2280,2560,2860,3180,3850,4560,5290,6030,6780,7520,826

0,8990,9911,0431,1141,1841,2581,3241,3941,4631,5331,6731,7431,844

2,0242,0942,4462,7993,1513,504

0,14890,17240,19670,22140,24620,27080,2949

0,31840,34120,36320,38440,40490,44390,48070,51600,55030,58420,61790,6517

0,68580,72030,75500.79020,82550,86090,89620,93160,96711,00301,07301,10901,1180

1,2511,2871,4641,6411,8181,995

0,1540,1690,1870,2050,2240,2420,263

0,2800,2480,3160,3330,3480,3670,4000,4200,4400,4600,4740,490

0,5050,5160,5300,5400,5500,5580,5660,5750,5820,5900,6020,6080,620

0,6300,6340,6550,6700,6820.690

0,9680,9610,9530,9450,9350,9250,913

0,9010,8880,8740,8600,8450,8140,7820,7430,7170,7020,6570,629

0,6030,5790,5560,5350,5160,4980,4560,4510,4360,4120,4060,3970,360

0,3600,3510,3130,2820,2560,235

2.1.3.7 in dungin dung ca mch cp tng t nhin dung ca mt tin. mch dy cp th hai

bng t chnh l hai na din tch b mt ca hai dy dn hnh trpha gn nhau, cn in mil cht cch in dy dn hoc khng kh.

in dung c xc nh bi t s gia in tch trn in p gia hai dy.

Cng thc tnh in dung nh sau:

[ ]Km/F

r

raln36

xC

=

Trong :


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38

x: h s xon (1,011,07)a khong cch gia hai dy trong mt mch [mm]d0=2r ng knh dy dn [mm]

: h sin mi tng ng ca cht cch in

: l h s hiu chnh c trng cho hiu ng ln cn.

Cng thc tnh h s hiu chnh ng vi xon nhm i, xon nhm sao (c

mng bao che v khng mng bao che) v xon i kp nh sau:

( )

( ) 2201

2201

addd

addd

i

ii

++

+=

( )

( ) 2201sao

22

01saosao

addd

addd

++

+=

22

22

saoad

ad

+

=

( )( ) 2201

2201

65,065,0

addd

addd

kpi

kpikpi

+++=

Trong :d0 ng knh dy dn [mm]d1 ng knh dy dn k c cht cch in [mm]d ng knh mng che chn [mm]a khong cch gia hai dy trong mt mch [mm]

2.1.3.8 in dn cch inin dn cch in l mt i lng c trng cho mc tiu hao nng lng tn hiu

trong mi trng cht cch in. xt in dn cch in, ta hy xem mt mch gm hai dy dn nh mt tin. Kt qu

xem xt, ta c cng thc tnh in dn cch in nh sau:

[ ]KmcimenGGG f /0 +=

Trong :

cRG

10 = : in dn cch in mt chiu (Rc: in trcch in mt chiu)

CtgGf = : in dn cch in xoay chiu vi tg l h s tiu hao in mi.

2.1.3.9 Tr khng c tnhTrkhng c tnh c xc nh nh trkhng u vo i vi ng truyn dn tn hiu

tng t dng chun c c ly v hn. Trkhng c tnh c hnh thnh tin dung, tcm, v in tr. Mi si cp u c trkhng c tnh ca n, gi tr ca trkhng c tnh cxc nh bi kch thc hnh hc v hng sin mi ca dy dn.

Cc loi cp truyn dn c ch to t c trkhng c tnh khng i theo dica cp. V d, nu si cp c di 30 m c trkhng c tnh l 100 th n vn l 100 khi di ca n tng ln gp i, gp ba ln ng vi mt tn s tn hiu truyn.


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Vic phi hp trkhng trnn rt quan trng khi tn s cao.

Vi cp UTP, ScTP c trkhng c tnh 100 15% tn s 1 MHz hoc cao hn. Vicp STP, STP-A c trkhng c tnh 150 10% tn s 3 MHz300 MHz.

2.1.3.10 Suy gim tn hiuSuy gim tn hiu ca ng dy l s khc nhau v t l ca cng sut ng vo v ng ra.

T l ny c biu din bng gi tr decibels (dB). Tuy nhin, suy gim tn hiu ca ng dyl trng hp c bit v ch p dng khi c s phi hp trkhng gia trkhng ti v trkhngngun vi trkhng c tnh ca i dy. i vi tt c cc u cui khc, cc php o lng vsuy hao c tham chiu nh l suy hao chn vo v s ln hn gi tr suy gim tn hiu c chotrn ng truyn dn.

2.1.3.11 Suy hao di hay suy hao phn hiKhi m trkhng ti khng phi hp vi trkhng c tnh th c mt phn nng lng tn

hiu b phn hi v ngun. Suy hao ny gp phn vo suy hao chn ca ng truyn dn.

Ton b nng lng phn hi lin quan n cp mt phi hp gia ti v ng truyn

dn. Phi hp cng tt nng lng phn hi cng b. Cng t nng lng phn hi th nng lngtn hiu truyn n ti cng ln.

Trong h thng cp, cc im kt ni khng phi hp trkhng tt cng gy ra suy haophn hi. V d: cc u ni, cc kt cui ng dy.

2.1.3.12 Tc truyn dn sn v cbn ca tin tc s l bit (cch gi tt ca s nh phn). N c dng biu din

hai trng thi (v d: c hoc khng c dng in, ...). Mt vi bit nh vy nhm theo lut m chotrc to ra mt character.

Tc bit l s lng bit tin truyn i trong mt giy. V d, trong mt giy truyn c1000 bit, ta gi ng truyn c tc 1000 bps (bits per second).

Tc baud l s lng mu tin truyn i trong mt giy. V d: 250 Bd (baud) l trongmt giy truyn i c 250 mu tin.

C 16 mu tin khc nhau c s dng. Mi mu i din 4 bit tin, trong mt giy c 1000bit tin c truyn i nhng ch c 250 mu tin c truyn. Khi ta gi ng truyn c tc bit l 1000 bps hoc tc baud l 250 baud.

Baud khng c nhm ln vi bits per second (hoc bytes per second, ...). Mi mu truyni c th c mt hoc nhiu bit tin tc (v d: 8 bits trong iu ch 256-QAM). Khi m mt mutruyn i ch c mt bit th lc tc baud bng tc bit.

2.1.3.13 Xuyn knhHin tng tn hiu truyn trn mt mch dy ny to ra mt hiu ng khng mong mun

trn mt mch dy khc, hoc s chuyn di tn hiu t mch dy ny sang mch dy khc cgi l xuyn knh. S chuyn di ny c th xy ra gia cc i dy k cn nhau trong mt sicp. Hin tng xuyn knh s gim i khi cc i dy c xon, c s xp t cp, c lp bov, v tnh cht cch ly ca cc i dy trong qui trnh ch to cp. Hin tng xuyn knh s tngln khi tng tn s ca tn hiu truyn, nhng khng t l vi nhau.


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C hai loi xuyn knh trong cc h thng cp kim loi. Xuyn knh u gn (NEXT-NearEnd Crosstalk) l mc tn hiu ca i dy gy xuyn knh so snh vi tn hiu trn i dy bxuyn knh cng mt pha u gn.Trong khi xuyn knh u xa (FEXT-Far End Crosstalk) lmc tn hiu ti u gn ca i dy gy xuyn knh so snh vi tn hiu truyn n i dy bxuyn knh u xa.

2.1.4 Phn loi cp2.1.4.1 Cp UTP (Unshielded Twisted Pair)

Cp UTP c dng truyn tn hiu thoi v d liu, ph bin trong mng my tnh, hthng in thoi. Cp UTP thng c gi l cp Ethernet v c cc c tnh sau y:

Bao gm nhiu i dy xon c trong si cp.

Thng thng chp nhn t 2 n 1800 i.

Khng cn c lp bo v cho n 600 i v c lp bao bng thp-nhm khi t n 1800i.

Bo v nhiu in bng cch xon dy.

C trkhng c tnh 100 . Khuyn ngh cdy t 22 AWG24 AWG.

Dy c rut.

C th ni cp UTP c cc u im sau y:

C kch thc nh, mm do d dng cho i cp theo cc btng.

Do kch thc nh, n khng d chim y trong ng.

Gi cp UTP thp hn so vi tt c cc loi cp LAN khc.

Tuy vy n cng c nhc im l d bnh hng ca nhiu so vi nhiu loi cp khc.

Chun ANSI/TIA/EIA-568-A xy dng mt s loi cp UTP c c trng truyn dn nhsau:

UTP


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Cp UTP loi 3 (Category 3-UTP cables) v phn cng lin kt c th truyn tn hiu tn tn s 16 MHz.

Cp UTP loi 4 (Category 4-UTP cables) v phn cng lin kt c th truyn tn hiu tn tn s 20 MHz.

Cp UTP loi 5 (Category 5-UTP cables) v phn cng lin kt c th truyn tn hiu t

n tn s 100 MHz.Cp UTP loi 1 v 2 (Category 1 and Category 2) khng c cng nhn cho lp t trong

cc dch v mi. Chng c th ch dng cho cc ng dng thoi.

Cp UTP loi 3 l cp b nht m ANSI/TIA/EIA-568-A ngh lp t trong cc dch vmi.

Vi cp ng UTP loi 5:

c ngh l la chn th hai trong lp t cp ra (area outlet) (ANSI/TIA/EIA-568-Atha nhn la chn th nht l cp UTP loi 3).

S h tr10BASE-T Ethernet, 100BASE-T Fast Ethernet, 1000BASE-T Gigabit Ethernet,

ATM 155 Mbps, TP-PMD 100 Mbps, v cc cu hnh LAN khc.

C th h trbng thng n 100 MHz.

Categories of Unshielded Twisted Pair(cc loi cp UTP)Type Use

Category 1 Voice Only (Telephone Wire)

Category 2 Data to 4 Mbps (LocalTalk)

Category 3 Data to 10 Mbps (Ethernet)

Category 4 Data to 20 Mbps (16 Mbps Token Ring)

Category 5 Data to 100 Mbps (Fast Ethernet)

Khi lp t cp xon i cn ch phn bit r rng cc i dy, cc si dy trong si cp.Cc m mu cp gip ngi lp t nhn bit mt cch nhanh chng cc i dy trong si cp.Ngi lp t cng phi phn bit gia hai si trong mt i. Trong in thoi, mi i dy c si

tip v si ring hoc dy dng v dy m theo th t.

Cm t tip v ring c a ra trc y trong h thng in thoi, trong trng hpmt in thoi vin thc hin mt kt ni vt l cho cuc gi bng dy ni lp i lp li nhiu ln.

Cp UTP c dng lm kt ni tm (UTP patch cable/cord), c s kt ni lp i lp linhiu ln cn c cu trc dy bn mm do. Cc u ni cng phi c thit k dnh ringcho loi cp ny trnh lm hng dy v kt ni sai.


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Mt loi khc ca UTP l cp i di thm. Cp i di thm khng phi l s la chnu tin. N khng c khuyn khch dng bi l:

D b hng.

B hn ch linh ng khi di chuyn, thm vo, v thay i.

Nu phi s dng cp i di thm, ngi lp t cn trnh:

Cc ni c mt s dng cao.

Cc vt dng trong vn phng nng t bn trn.

Cp ngun i di thm.

Cp c nhiu i dy (ln hn 4 i) thng c dng lp t backbone.

Cp UTP loi 6 v 7 (Category 6 and Category 7 cable) khng c U ban tiu chun chpnhn. Chng c c tnh ca cc nhm lm vic TIA t c:

Category 6 s h trcc bng thng t n 200 MHz.

Category 7 s h trcc bng thng t n 600 MHz.

2.1.4.2 Cp ScTP (Screened Twisted Pair)Cp ScTP c gi thnh t hn cp UTP. Cp ScTP cho kh nng min dch cao i vi s

giao thoa tn hiu v c dng trong cc khu vc d b nhiu v giao thoa.

Nu khng tnh n lp bo v bng mylar/aluminum dng l v dy dn lu (drain wire)th cu trc v trnh by ca cp ScTP ging nh cp UTP. Lp bo v mylar tip nhn v truyndn cc tn hiu tn s cao thng qua lp bao cp (cable jacket). Dy dn lu chy gia lp mylarv lp bao bn ngoi (outer jacket) dng ni t lp mylar.

Cp ScTP c :

Trkhng c tnh 100 . Bn i dy c rut c22 AWG24 AWG (thng thng).

Lp bo v bng mylar/aluminum bao quanh cc i dy.

Dy dn lu c ni t.

Cc c tnh in cng tng t nh cp UTP loi 3, 4, 5.

Loi ScTP c mn bao che (S/STP- Sreened Shielded Twisted Pair) cn gi l SreenedFully shielded Twisted Pair (S/FTP) c hai lp bao che ring bit: lp bao che cho mi i cp(ging nh cp STP) v lp bao che bng kim loi bn ngoi bao bc ly ton b nhm bao checa cc i dy ng (ging nh cp (S/UTP). Loi cp ny bo v rt tt s giao thoa tn hiu tcc ngun tn hiu bn ngoi.

S/FTP (Screened Fully shielded Twisted Pair)(Screened Shielded Twisted Pair)


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ScTP loi khng c mn bao che (S/UTP-Sreened Unshielded Twisted Pair) cn gi l cpFully shielded (or Foiled) Twisted Pair (FTP).

2.1.4.3 Cp STP (Shielded Twisted Pair)Cp STP c pht trin ti thi im

m cp UTP khng cn ph hp truynd liu tc cao. Cp STP c mn bao chebng kim loi ring bit cho mi i dytrong si cp. Mn bao che ny chng lihin tng giao thoa in t bn ngoi(EMI-Electromagnetic Interference).

Cp STP 150 h trtruyn dn tn hiu ln n 20 MHz. Vi yu cu tng bng thng thcp STP c mn bao che c bit v cc u ni (STP-A) c th h trtruyn dn tn hiu ln n300 MHz.

Cp STP v STP-A thng s dng trong lp t mng token ring. STP-A c bng thngcao nht trong cc phng tin truyn dn cp ng c ANSI/TIA/EIA-568-A ph chun. Nc dng hu ht cho cc ng dng trong trng hp khng dng hn hai i dy.

Cp STP-A c cc c im sau :

Ch bao gm hai i dy.

Mi i c bao bc bng mng bao che mylar/aluminium dng l gim thiu hintng giao thoa tn hiu tn s cao.

Mng bao che dng bn bao bc ton b hai i dy gim thiu hin tng giao thoa tnhiu tn s thp.

Dy dn c kch thc 22 AWG.

Mng bao che ni t.

C duy nht m mu: cc i green/red v black/orange.

2.1.5 Cc u kt ni cp2.1.5.1 u ni UTP

8P8C (eight positions, eight conductors/contacts) l u cm hoc l cm (plug or jack) c8 v tr v 8 dy/8 chu. u cm hoc l cm 8P8C rt ging vi u cm v l cm RJ45(Register Jack). Tuy vy, khng th so snh mt cch hon ton RJ45 vi cc u ni 8P8C.RJ-45 khng s dng ht 8 dy m cng khng th cm va vn vo 8P8C v RJ45 l loi c cht(keyed).

(Sreened Unshielded Twisted Pair/Fully shielded (Foiled) Twisted Pair)


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C ba loi u cm v l cm c s dng trong vin thng l:

4P4C - u ni 4 v tr, 4 chu: dng cho dy ni t hp my in thoi.

6P6C - u ni 6 v tr, 6 chu: dng kt ni ng dy vi my in thoi v modem(tham chiu nh cc u ni RJ11).

8P8C - u ni 8 v tr, 8 chu: dng cho cc dy ni truyn d liu (tham chiu nh cc

u ni RJ45).Cc u ni UTP (ch yu l cc u cm v l cm 8P8C) c thit k cho:

Kt cui cp 100 , 4 dy, 22 AWG24 AWG.

H tr100 MHz, Category 5 standards.

S dng cc kt cui IDC (Insualation Displacement Connections).

C rt nhiu h thng tng i PBX s dng cp 25 i c u ni loi Telco 50-pin.

S BM CP CHO RJ45 (CROSS-OVER)

MALE

TELCO 50-PIN CONNECTOR (IDC)

FEMALEMAL FEMAL


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2.1.5.2 u ni ScTPMt u ni 8P8C c v bao che thng s dng cho cp ScTP 4 i. Cc u ni ScTP l

cc u cm hoc l cm 8P8C c v bao che c thit k cho kt cui cp 100 , 4 i,22AWG24AWG ; h tr n 100 MHz, Category 5 standards; s dng cc kt cui IDC(Insualation Displacement Connections), c bao bc bi lp bo v bng kim loi, v kt nivi v bao che ca cp ScTP bng dy dn lu (drain wire).

2.1.5.3 u ni STPu ni STP d liu l u ni lng tnh c 4 chu dng kt ni cp c mng bao che. Cc

u ni ST c th kt ni vi nhau.

Khi thit k cho cc ng dng token ring, cc u ni ny chuyn tip tn hiu n thit bthng qua mt i dy ca u ni. Tn hiu sau i ra t mt dy khc ca u ni. Tt c ccthit bc kt ni trong mt vng ni tip ln. Ch mt mch u b hth ton b vngring b hng.

Trong mi u ni c mt cp thanh ngn mch trnh b hmch vng ring khi u nitho ra. Ngay khi u ni b tho ra th thanh th nht s ngn mch hai dy tip v thanh th hais ngn mch hai dy ring. iu ny lm ni thng u vo v u ra ca mt u ni, nn vngring vn m bo khp kn.

Kh nng ca cc u ni c th truyn dn vi bng thng n 20MHz, v cc u ni nyc thit k :

Kt cui cp 150 , 2 i dy, 22 AWG.

C bng thng 20 MHz.

S dng m mu red/green v black/orange.

2.1.5.4 u ni STP-ACp v u ni STP-A cng ging nh cp v u ni STP ngoi tr lp bao che nng cao.

N c ng dng trong truyn dn s liu c tc cao. y cng l cc u ni lng tnh c 4

chu. Cc u ni STP-A c bng thng ca i dy xon cao nht c tha nhn biANSI/TIA-568-A v c ch to cho :

Kt cui cp nng cao 150 , 2 i dy, 22 AWG.

C bng thng 300 MHz.

S dng m mu red/green v black/orange.

ICC ScTP Category 5e

Modular Schielded Connector


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2.1.6 Kt cui cp2.1.6.1 Cc bc t in xc nh1) T chc cp ti ni kt cui: Cn bit trc s ni dy, xc nh cc phn t khng tng

thch. i vi kt cui IDC cho cp ng, c ba s ni dy ph bin : T568A, T568B, vUSOC (Universal Service Order Code). Ch c s ni dy T568A v T568B tun th theo

chun ANSI/TIA/EIA-568-A. S ni dy nh m t trong hnh sau :

2) Sp xp cp ti ni kt cui: trnh cp chng cho ln nhau, tt c cc si cp t songsong nhau, sp xp phi gn gng, trt t. Sau khi xc nh chng cp, th cc si cp phic t tn li v ct b cc cp tha sao cho di cc si cp ng dng. Mi si cp phic lm du cn thn trc khi ct b phn tha cha tn cp, sau t tn li cho chnhxc. S dng cc phng tin gi cht cp nh dy buc, cc mc , mc gi, v ch buccht cp bng tay.

3) Xc nh di v chng cp theo yu cu: cn xc nh khng gian ng i ca cp y v chnh xc m bo cp sau khi kt cui c chng t yu cu. Trong trng hp chng khng m bo th s gp rt nhiu kh khn khi di chuyn, thm vo, thay i.

mang truy nhap-hv bcvt i

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