Ky Thuat Truyen So Lieu 6889

5/24/2018 Ky Thuat Truyen So Lieu 6889

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BK

TP.HCM

2008

e

K Thut Truyn S Liu


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2008, Dr. Dinh Duc Anh VuData Communication and Computer Networks

2008

e

Mn hc M s: 504003

S tn ch: 4 Mn hc trc: khng

Ging vin Phannh Khi

Khoa Khoa hc v K thut my tnh

[email protected] (8647256 ext. 6227)

http://cse.hcmut.edu.vn/~khoi

Gii thiu
mailto:[email protected]://cse.hcmut.edu.vn/~khoihttp://cse.hcmut.edu.vn/~khoimailto:[email protected]


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2008

eGii thiu mn hc ng lc

S pht trin v bo ca ccng dng my tnh S cn thit ca vic traoi thng tin gia cc ni, gia cc my tnh

Mcch Gii thiu cc khi nim, thut ng v cc phng php tip cnc dng trong cc

h thng truyn d liu Hiu vic truyn s liu gia 2 thit b v cc vn lin quan Hiu vic truyn d liu qua mng gia 2 thit b thng qua mt nghi thc giao tip Gii thiu mt s mng truyn s liuc s dng hin nay

i tng Sinh vin chuyn ngnh c kin thc v thit k mch, cu trc my tnh, ngn ng lp

trnh cp cao K s chuyn ngnh

nh gi Kim tra gia k: 30% Thuyt trnh:

Nhm 3 - 4 ngi, trnh by 20 pht, cht vn 10 pht Khng bt buc Thay th cho thi gia k

Kim tra cui k: 70% Phng php: t lun


4/4732008, Dr. Dinh Duc Anh VuData Communication and Computer Networks

2008

eNi dung mn hc

Tng quan v truyn s liu v mng truyn s liu Truyn dn s liu

K thut m ha tn hiu K thut truyn d liu s iu khin lp lin kt d liu

Ghp/tch knh

Chuyn mch mch v chuyn mch gi

Ch truyn btng b Tmng trong mng chuyn mch iu khin nghn mch trong mng chuyn mch

d liu



2008

eTi liu tham kho [1] Tp slide bi ging, TS.inhc Anh V, 2008 [2] Data and Computer Communications William Stallings

[3] Data Communications, Computer Networks and Open Systems Fred Halsall

ISDN & B-ISDN William Stallings

ATM Foundations for Broadband Networks Uyless Black Data Communications William L. Schweber

Data communications and teleprocessing systems Trevor Housley

Data communication technology James Martin

Cng nghATM v CDMA LG Information & Communications Lecture notes for M.Sc. Data Communication Networks and Distributed Systems D51 --

Basic Communications and Networks - Saleem N. Bhatti - Department of Computer Science- University College London - October 1994

Lecture notes for DATA COMMUNICATIONS, v4.0 Brian Brown, 1995-2001.

Fiber Optics Communication and Other Applications Henry Zanger & Cynthia Zanger.

Wireless Networked Communications Concepts, Technology and Implementation Regis J.Bates.

Practical digital and data communications with LSI applications Paul Bates


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BK

TP.HCM

2008

e

Chng 1Tng quan v truyn s liu v

mng truyn s liuM hnh h thng truyn d liu

Truyn s liuMng truyn s liu

Kin trc truyn s liu dng my tnh



2008

eM hnh h thng truyn d liu

ng dng d liu ng dng m thanh, ting ni

ng dng video ng dng thi gian thc

S khi tng qut m hnh Shannon

V d



2008

eM hnh h thng truyn d liu

H thng truyn d liu l g? D liu: biu din s liu, khi nim, di dng thch hp cho vic

giao tip, x l, din gii

Thng tin: nghac gn cho d liu

Tp hp cc thit b c kt ni thng qua mt mi tr ng truyndn



2008

eCc tc v chnh S dng h thng truyn dn

Chia s ng truyn hiu qu gia nhiu thit b, chng nghn mch Giao tip gia thit b vi h thng truyn To tn hiu

C kh nng truyn dn trong mi trng truyn Bn nhn phi hiuc d liu ng b gia bn truyn v bn nhn Qun l vic traoi d liu

Cc giao thc truyn d liu

iu khin dng d liu Pht hin v sa li nh v a chv tmng Khi phc

Khi phc li trng thi c ca h thng khi c li lm ngt qung nh dng thng tin Bo mt Qun tr mng

Cit h thng, qun l tr ng thi, x l li, c k hoch nng cp trong tng lai


10/4732008, Dr. Dinh Duc Anh Vu 1Data Communication and Computer Networks

2008

eHthng truyn dliu

Ti sao phi dng hthng truyn dliu Chia sti nguyn

My in

a/bng t Cng sut tnh ton Tp hp dliu

Phn tn ti Tnh ton song song Tnh ton theo m hnh client-server

Fault tolerance

Chuyn thng tin Giao dch csdliu Th in t

Phn tn dliu trn mng lu tr



2008

eTruyn sliu

Lin quann cc vntruyn dliu sdng th Truyn dn dliu (data transmission) M ha dliu (data encoding) Kthut traoi dliu s(digital data communication) iu khin lin kt dliu (data link control) Phn hp (multiplexing)

Lin kt (link) hoc mch (circuit) Knh (channel)



2008

eMng truyn sliu

Giao tipim-imthng khng thc t Cc thit bcch xa

nhau Skt ni tngng k

khi scc thit bcngiao tip ln

Mng truyn sliu

Phn loi da vophm vi hotng



2008

eMng truyn sliu

Mng cc b(Local-Area Networks LAN)c tnh

Tm vc nh(ta nh, nhiu ta nh) Thngc shu bi 1 cng ty, tchc

Tccao hn WAN

Phn loi Switch LAN (Ethernet)

Wireless LAN ATM LAN

Xem chi tit trong [2], phn 4


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2008, Dr. Dinh Duc Anh Vu 1Data Communication and Computer Networks

2008

eMng truyn sliu

Mng din rng (Wide-Area Networks WAN) Khc nhthno so vi mng LAN? Trin khai theo din rng Da vo cc mch truyn dn cng cng

Cng ngh Chuyn mch mchin (circuit-switching) ng truyn dn dnh ring gia 2 node mng

Chuyn mch gi (packet-switching) Khngc dnh ringng truyn dn

Mi gii theong khc nhau Chi phng truyn caokhc phc cc li truyn dn

Frame Relay c dng trong chuyn mch gi c tcli thp Tclnn 2 Mbps

ATM Ch truyn btng b(Asynchronous Transfer Mode) Dng cc gi c kch thc c nh (gi l cell) Tclnn Gbps

ISDN Mng scc dch vtch hp (Integrated Services Digital Network)


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2008

eMng truyn sliu

Mt cch phn loi khc Da vo kin trc v kthut dngtraoi d

liu Mng chuyn mch (switched networks)

Mng chuyn mch mchin

Mng chuyn mch gi

Mng pht tn (broadcast networks)

Mng radio gi (packet radio net.) Mng vtinh (satellite net.)

Mng cc b(local net.)


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BK

TP.HCM

2008

e

Ch

ng 1Tng quan vtruyn sliu v

mng truyn sliuM hnh hthng truyn dliu

Truyn sliuMng truyn sliu

Kin trc truyn sliu dng my tnh


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2008

eKin trc truyn thng my tnh

ng dng truyn file Ngun thit lp kt ni (bo cho mng bitu lch) Ngunm boch sn sng nhn dliu ng dng truyn file trn h/t ngun phim bo chng trnh qun l

file trn h/tch sn sng nhn v lu trfile Nunh dng file dng trn 2 h/t khng tng thch, mt hoc c2 h/t

phi thc hin chc nng chuyni

Tc vgiao tipc phn nhthnh cc mun V d, truyn file c th c phn thnh 3 mun

Truyn file Dch vgiao tip Truy xut mng

V d ki h


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2008

eV dkin trc phn cp

N hi th i ti ( t l)


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2008

eNghi thc giao tip (protocol)

Dnggiao tip gia ccthc thtrong mt hthng Thc th

C khnng gi/nhn thngtin ng dng ngi dng Th in t Thit b u cui

Hthng i tng vt l, cha mt

hoc nhiu thc th My tnh

Thit b u cui Cm bin txa

Phi cng ni mt ngn ng

Cc thnh phn chnh camt nghi thc giao tip Ngphp (syntax)

nh dng dliu Mc tn hiu

Ngngha (semantic) Thng tin iu khin

Xl li nh thi (timing)

ng b Tun t

M h h i 3 l


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2008

eM hnhn gin 3 lp

Lp truy xut mng Lp vn chuyn

Lpng dng

eL t t


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2008 Lp truy xut mng

Traoi dliu gia my tnh v mi trngmng

Cung cpa chmy nhn, tmngi Yu cu cc dch vtmi trng mng

(priority) Phthuc vo loi mngang sdng (LAN,

chuyn mch gi, mch)

eL h


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2008 Lp vn chuyn

m nhn vic truyn dliu tin cy Dliunnga ch

Theo tht gi Khng phthuc vo loi kt ni mng bn

di Khng phthuc vong dng

eL d


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2008 Lpng dng

Cung cp cho ccng dng cc dch v truy cp mng

Web browser: HTTP Email: SMTP

File: FTP

2008

eKin trc 3 lp


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2008 Kin trc 3 lp

2008

eProtocol data unit (PDU)


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2008 Protocol data unit (PDU)

Ti mi lp c nhiu protocol c sdng Dliu ngi dng phic thm vo cc thng tin iu

khin ti mi lp

Lp vn chuyn c thchia nhdliu ngi dng

2008

eHot ng ca kin trc 3 lp


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2008 Hotng ca kin trc 3 lp

2008

eTiu chun ha


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2008 Tiu chun ha Cn thit cho cc tc vlin thng gia cc thit b Cc tchc chun ha

Electronics Industries Association EIA: hip hi cc nh sn xutM, a ra chunRS232 v cc chun tng t

Institute of Electrical and Electronic Engineers IEEE (http://www.ieee.org): tchc nh

nghca cc ks in-in t(IEEE-754: chun cho schmng) International Telecommunications Union ITU (http://www.itu.ch): iu phi cc chun

tm quc t, cp pht tn svin thng vtinh

American National Standards Institute ANSI (http://www.ansi.org): i din cho mt stchc chun haM(chun cho k tASCII)

International Organization for Standards ISO (http://www.iso.ch): c nhiu chun linquann my tnh, i dinMl ANSI (ISO9000 l chun lin quan bo him chtlng)

uim

Bom thtrng ln cho cc thit bv cc phn mm Cho php cc sn phm ca cc nh cung cp c thgiao tip vi nhau

Nhcim Hn chspht trin cng ngh C thc nhiu chun cho cng mt cng ngh

2008

eTiu chun ha
http://www.ieee.org/http://www.itu.ch/http://www.ansi.org/http://www.iso.ch/http://www.iso.ch/http://www.ansi.org/http://www.itu.ch/http://www.ieee.org/


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Tiu chun ha

Hthng kn (shu ring) cnh ngha bi mt vi nh sn xut my tnh Chlin quann vic truyn dliu trong mt my tnh hoc gia my tnh

vi cc thit bngoi vi

Hthng nhiu nh cung cp (thng mi ha) cnh ngha bi mt snh cung cp dch vvin thng SNA (IBM), IPX (Novel), ...

V-series: kt ni gia DTE v modem kt ni vi PSTN

X-series: kt ni gia DTE v PSDN I-series: kt ni gia DTE v ISDN

Hthng DoD

TCP/IP Transmission Control Protocol/Internet Protocol)

Hthng m cnh ngha bi ISO

OSI Open Systems Interconnection

2008

eM hnh DoD


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M hnh DoD Pht trin bi DARPA (Defense Advanced Research Projects Agency) cho mng chuyn

mch gi ARPANET (sau ny l Internet)

Sp xp phn cp ca cc thc thc khnng giao tip vi cc thc thngang cp trongmt hthng khc

Trong mt hthng, mt thc thcung cp dch vcho cc thc thkhc v cng sdng

dch vca cc thc thkhc Nhn mnh vo internetworking, ngha l, khi 2 thc thgiao tip khng ni chung mt mng

Quan tm chthng hngn kt ni v khng kt ni

Bao gm ccng dng: traoi file (FTP, RCP), m phng terminal (telnet, rlogin), sv

truy cp file phn tn (NFS), thc thi lnh txa (rsh, rexec), in n txa (lpr), 802.X, X.25,mail (SMTP), qun trmng (NSP, SNMP)

TCP/IP c pht trinng thi vi m hnh ISO Khng cha cc nghi thc lin quann cc lp trong m hnh ISO

Hu ht cc chc nng ca m hnh ISO c tch hp trong TCP/IP

Khng phi m hnh chnh thc, nhng l mt m hnh thc tin Lpng dng

Lp transport (giao tip gia cc thit b)

Lp Internet

Lp truy xut mng

Lp vt l

2008

eM hnh kin trc nghi thc TCP/IP


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M hnh kin trc nghi thc TCP/IP

2008



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Lp vt l Giao tip vt l gia thit bv mi trng truyn Tnh cht ca mi trng truyn, mc tn hiu, tctruyn

Lp truy xut mng Traoi dliu gia thit bv mng truyn Cung cp chc nng tmng gia 2 thit btrong cng 1 network Yu cu cc dch vtmng truyn (priority)

Lp Internet Cung cp chc nng tmng gia 2 thit bthuc 2 mng khcnhau

Cnc hin thc trong cc router

Lp transport m nhn vic truyn dliu tin cy gia 2 ng dng Chc chn dliuinch, cc gi dliunng tht gi

Lpng dng

Cung cp cho ccng dng cc dch v truy cp mng


2008

eD liu c truyn qua TCP/IP


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Dliuc truyn qua TCP/IP

2008



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2008

eM hnh mng ISO/OSI


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M hnh mng ISO/OSI

Hthng l thuyt raiqu tr TCP/IP ang l tiu chun

thc tin (de facto

standard) 7 lp

ng dng (application) Trnh by (presentation)

Giao dch (session) Vn chuyn (transport) Mng (network) Lin kt dliu (data link)

Vt l (physical)

Application Layer

Transport Layer

Presentation Layer

Session Layer

Network Layer

Datalink Layer

Physical LayerNetworkenvironment

O

SIenvironment

Real system environment

2008

eM hnh mng ISO/OSI


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M hnh mng ISO/OSI

2008

eLp hng ti ng dng


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Lp hng ting dng

Lpng dng Cung cp cho ccng dng cc dch v truy cp mng

Lp trnh by Cung cpnh dng dliuc dngtruyn dliu gia cc

my tnh ni mng (chuyni m k t, m ha dliu, nn dliu)

Lp giao dch Cung cp cch iu khin vic truyn thngip gia ccng dng

(trgip danh b, quyn truy cp, chc nng tnh cc, ) Cho php 2 ng dng to, sdng v xa kt ni C khnng nhn dng tn v cc chc nng khc (security,

recovery) cn thit cho 2 my tnh ni kt qua mng

Quan tmn cc lp di (tlp vn chuyn trxung) Cc lp trnc tch hp trong h iu hnh v khng cn thit phi

chun ha

2008

eLp hng ti ng dng


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Lp hng ting dng

Lp vn chuyn Cung cp cchtraoi dliu gia 2 hthng Cung cp dch vgi thngip (message service) end-

to-end cho cc lp trn Bom dliuc truyn khng c li, theo thtvkhng mt mt, ngt qung hoc dtha

Chu trch nhimng gi dliu tmt message ln

thnh nhiu message kch thc nhhngii v tphp cc message nhthnh mt message ban u khinhnc (c khnnga hp)

Ngt thng bo thnh cc gi nh(c kch thc thch hp) v tp

hp cc gi cho lp mng Kt hp cc giao dch vi cng cc node ngun/ch Ti lp thtcc gi tichn Khi phc li, hhng

iu khin dng tngunnch v ngc li

2008

eLp ph thuc mi trng truyn dn


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Lp phthuc mi trng truyn dn

Lp mng Trung chuyn cc gi gia lp

vn chuyn v lp lin kt dliu

nha chgi v dchachlun l thnha chvt l

Tmng kt ni vi my

tnh khc thng qua mng Mi node cha mt moun

lp mng cng vi mt mounlp lin kt dliu cho mt

lin kt Khng cn thit nu kt ni 2

my trc tip

2008



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Lp lin kt dliu Chu trch nhim truyn dn mt cch tin cy

(error-free) cc gi dliu ca lp mng trn mtlin ktn ng khung: xcnhu v cui cc gi

Pht hin li: xcnh gi no c ling truyn Sa li: cchtruyn li (Automatic Repeat Request

(ARQ))

2008



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Lp vt l iu khin vic truyn dliu (chui cc bit) thc strn cp/mng nh ngha tn hiuin, trng thing truyn, m ha thng tin v

kiu kt nic sdng

Thi gian trtruyn Thi gian t/h truyn tngunnch T/h truyn vi vn tc xp xvn tc nh sng C=3x108 m/s V d

vtinh GEO d=40.000km trtruyn 1/8 s;

cp Ethernet d=1km trtruyn 3s Li truyn

Suy gim cng sut t/h Suy gim do nhiu M hnh knh truynn gin: knh nhphni xng (Binary Symetric

Channel) P: xc sut li 1 bit Li xy rac lp

Thc t, li xy ra thnh chm


2008

eTruyn dliu qua m hnh mng OSI


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y q g

Presentation layer

Session layer

Application layer

Transport layer

Network layerDatalink layer

Physical layer

Application process

Presentation layer

Session layer

Application layer

Transport layer

Network layerDatalink layer

Physical layer

Application process

Data network

Network environment

OSI environment

Real systems environment

Computer I Computer II

2008

eDliuc truyn qua mng OSI


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y q g

2008 e

So snh m hnh OSI v TCP/IP


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2008 e

So snh m hnh OSI v TCP/IP


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2008 ec thm


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W. Stallings, Data and ComputerCommunications (7th edition), Prentice Hall

2004, chapter 1, 2 Web sites for IETF, IEEE, ITU-T, ISO

Internet Requests for Comment (RFCs) Usenet News groups

comp.dcom.*

comp.protocols.tcp-ip

2008 e


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BKTP.HCM

Chng 2Truyn dn sliu

Khi nim v thut ngTruyn dn dliu tng tv dliu sSuy haong truyn

Dung lng knh truynMi trng truyn dn cnh hngTruyn dn khng dyLan truyn khng dyTruynng thng (line-of-sight)

2008 e

Thut ng


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g

Thnh phn trong m hnh truyn dliu (di gcvt l) Thit b

Thit bpht (Transmitter) Thit bthu (Receiver)

Mi trng truyn (Medium)

Kt ni Kt ni trc tip (Direct link) Khng cn cc thit btrung gian

Kt niim-im (Point-to-point)

Kt ni trc tip Chc 2 thit bdng chung kt ni

Kt ni nhiuim (Multi-point) 2 thiet bdng chung kt ni

2008 e

Ch truyn


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Simplex mode Khng dng rng ri v khng thgi ngc li li hoc tn

hiu iu khin cho bn pht Television, teletext, radio

Half-duplex mode

B m

Full-duplex mode in thoi

2008 e

Tn hiu Khi nim min thi gian


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T/h lin tc Thayi mn theo thi

gian

T/h ri rc Thayi tng mc

theo thi gian

T/h tun hon Mu lp li theo thi

gian T/h khng tun hon

Mu khng lp li

theo thi gian

2008 e

Biu din tn hiumin tn s


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Tn hiu thc t c cu to bi nhiu thnhphn c tn skhc nhau

Cc tn hiu thnh phn l cc sng hnh sin Tt ccc tn hiu (tng tln s) u c

th c phn tch thnh tng ca nhiu sngsin (khai trin Fourier)

C thbiu din tn hiu theo min tn s Trc tung: cc tn sc trong tn hiu

Trc honh: bin nh ca tn hiu tngng

vi mi tn s

2008 e

V d


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2008 e

Tn s, phv bng thng


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Ph Tm tn scha trong tn hiu

Bng thng tuyti rng ph(co bng schnh lch tn scao nht

v thp nht) Bng thng knh truyn cng ln, tctruyn cng cao

Bng thng hiu dng Gi tt l bng thng Di tm tn shp cha hu ht nng lng ca tn hiu

Thnh phn mt chiu Thnh phn c tn sbng 0

2008 e

Truyn dn dliu tng tv s


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Dliu Cc thc thchang thng tin Dliu tng t: gi trlin tc trong 1 thi khong

Dliu s: gi trri rc theo thi gian Tn hiu Dliuc biu dindng tn hiuin hocin t

Tn hi

u t

ng t

Thayi lin tc theo thi gian Truyn trn nhiu mi trng: hu tuyn, quang, khng gian

Tn hiu s

Sdng 2 thnh phn DC Truyn dn

Traoi dliu bng cch lan truyn v xl tn hiu

2008 e

Truyn dn dliu tng tv s


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Thng thng Tn hiu tng t

truyn dliu tng t

Tn hiu struyn dliu s

Trong mt strng

hp Tn hiu tng tmang dliu s

Tn hiu smang dliu tng t

2008 e

Truyn dn tn hiu tng tv s


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Truyn tn hiu tng t Khng quan tm ni dung dliu chang bn

trong

Suy gim tn hiu theo khong cch

Dng amplifier khuchi tn hiu (kc

nhi

u) Truyn tn hiu s

Cn ch ni dung dliu chang bn trong

Khong cch truyn ngn Dng repeater tng khong cch truyn

Nhiu khng bkhuchi

2008 e

Truyn dn s


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uim Cng nghs

Cng nghLSI/VLSI lm gim gi thnh

Ton vn dliu Nhiu v suy gim tn hiu khng btch ly bi cc repeater

Truyn khong cch xa hn trn ccng truyn km cht lng

Hiu quknh truyn TDM > FDM

Bo mt Cc kthut m habo mt dliu dp dng

Tch hp Dliu sv analog c xl tng tnhau

2008 e

Suy gim tn hiu


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T/h nhnc khc vi t/h truyni Analog suy gim cht lng t/h

Digital li trn bit

Nguyn nhn

Suy yu v mo do suy yu trnng truyn

Mo do trtruyn

Nhiu

2008 e suy yu tn hiu trnng truyn


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nh ngha (signal attenuation) Khi mt tn hiu lan truyn qua mt mi trng truyn,

cng(bin) ca tn hiu bsuy gim theo khongcch

Ty thuc vo mi trng truyn dn i vi mi trng v tuyn, suy gim cngt/h l mt hmphc tp theo khong cch v thnh phn kh quyn

Cngt/h nhn phi

mnhthit bnhn nhn bitc cao so vi nhiut/h khng bli Suy yu l mt hm tng theo tn s

Kthut cn bngsuy yu trn di tn s

Dng bkhuychai (khuychitn scao nhiu hn) o bngn vdecibel (dB)

Cngt/h suy gim theo hm logarit li/hao ht ca cc tng ni tip c th c tnh bng php

tonn gin (+/-)

2008 e

Phm ca thoi v m nhc


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2008 e suy yu tn hiu trnng truyn


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Cng thc Attenuation = 10log10(P1/P2) (dB) P1, P2: cng sut (watts)

Decibel (dB) l gi trsai bit tngi Cng sut suy gim hao ht l 3dB Cng sut tng gpi li l 3dB

Attenuation = 20log10(V1/V2)

Do cng sut tiu thtrnin trR l P = V2

/R Gi trsai bit tuyti

Decibel-watt (dBW) 1W l gi trtham kho, tngng vi 0dBW

Cng sut (dBW) = 10log10 (cng sut theo W) Decilbel-milivolt (dBmV) 1mV l gi trtham kho, tngng vi 0dBmV in p (dBmV) = 20log10 (in p theo mV) y lin p gistrnin tr75

2008 e

Trlan truyn tn hiu


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Mo trlan truyn Chxy ra trong mi trng truyn dn hu tuyn Vn tc lan truyn thayi theo tn s

Vn tc cao nhtgn tn strung tm

Cc thnh phn tn skhc nhau s nchcc thiim khc nhau Cng thc Transmission propagation delay

Tp = S/V

S : khong cch vt l (meter) V : vn tc lan truyn tn hiu trn mi trng truyn, vi sngin

t: v = 2 x 106 (m/s)

Round trip delay

Tx = N/R N : khi lng dliu truyn (bit) R : tctruyn bit trnng truyn.

2008 e

Nhiu


62/473


T/h thm vo gia thit bpht v thit bthu Nhiu nhit

Do daong nhit ca cc electron trong cht dn Hm ca nhit

Phn tnng nht trn phtn s Nhiu trng

Khng thloi b gii hn hiu sut ca hthng Nhiu trong bng thng 1Hz ca bt kcht dn no N0= kT

N0: mtcng sut nhiu (watt/Hz) k: hng sBoltzmann (= 1.38 x 10-23 J/K) T: nhit(K)

Nhiu trong bng thng B (Hz) N = kTB

2008 e

NhiuNhi i h


63/473


Nhiuiu ch T/h nhiu c tn sl tng hoc hiu tn sca cc t/h

dng chung mi trng truyn Do tnh phi tuyn ca thit bthu/pht

Nhiu xuyn knh (crosstalk) T/h t ng truyn nynh hng sang ccng

truyn khc

Cngln (hoc nhhn) nhiu nhit Nhiu xung Xung bt thng (spike)

e.g. nh hngin tbn ngoi

Thi khong ngn Cngcao nh hng nhiun qu trnh traoi dliu s

Xung 0.01s lm mt 50 bit dliu nu truyntc4800bps

2008 e Tcknh truyn (khnng knh truyn)


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cim C thtruyn nhiu hn mt bit ng vi mi thayi catn hiu trnng truyn.

Tctruyn thng tin cci bgii hn bi bng thngca knh truyn

Cng thc Nyquist Nu tctruyn t/h l 2W th t/h vi tn snhhn

(hoc bng) W l; ngc li nu bng thng l W thtct/h cao nht l 2W C = 2W x log2M

C : tctruyn t/h cci (bps) khi knh truyn khng c

nhiu W : bng thng ca knh truyn (Hz) M : smc thayi tn hiu trnng truyn

hu hiu bng thng: B = R/W (bps Hz-1)

2008 e TcdliuB d t (b d/ )


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Baud rate (baud/s) Nghcho ca phn tdliu ngn nht (sln thayi tn hiu

ng truyn mi giy) Tn hiu nhphn tc20Hz: 20 baud (20 thayi mi giy)

Bit rate (bps hoc bit/s) c trng cho khnng ca knh truyn Tctruyn dliu cci trong trng hp khng c nhiu Bng baud rate trong trng hp tn hiu nhphn Khi mi thaying truync biu din bng 2 hay nhiu bit,

tcbit khc vi tcbaud Quan hgia Baud rate v Bit rate

R = Rsx log2M = Rsx m

R : tcbit (bit/s) Rs : tcbaud (baud/s) M : smc thayi tn hiu trnng truyn m : sbit m ha cho mt tn hiu

2008 e Thut ng


66/473


2008 e

Signal to Noise ratio

Tltn hiu trn nhiu


67/473


Signal to Noise ratio

SNR = 10 x log10(S/N) (dB) S: cng sut tn hiu nhn N: cng sut nhiu

Cng thc Shannon-HartleyC = W x log2(1 + S/N) (bps)

C: tctruyn t/h cci khi knh truyn c nhiu

Tsnng lng t/h ca 1 bit so vi nng lng nhiu ca 1Hz Eb/N0 Tb: thi gian truyn 1 bit

R: tcbit ca dliu nhphn Eb= STb= S/R

Eb/N0= S/(RN0) = S/(kTR)

Tcsai bit l hm gim ca tsny

2008 e


68/473

BKTP.HCM

Ch

ng 2Truyn dn sliuKhi nim v thut ngTruyn dn dliu tng tv dliu sSuy haong truynDung lng knh truynMi trng truyn dn cnh hngTruyn dn khng dyLan truyn khng dyTruynng thng (line-of-sight)

2008 e Bc sng


69/473


Khong cch sng truync trong mt chuk

Khong cch gia 2 im pha tngngtrong 2 chu klin tip

K hiu

Gisvn tc t/h v = vT

= v/f

c = 3*108 ms-1 (tcnh sng)

2008 e Mi trng truyn dn Hu tuyn (guided media wire)


70/473


y (g )

Cpng Cp quang

V tuyn (unguided media wireless) Vtinh

Hthng sng radio: troposcatter, microwave, ... c tnh v cht lngc xcnh bi mi trng v tn

hiu i vi hu tuyn, mi trngnh hng ln hn i vi v tuyn, bng thng to ra bi antennh hng ln hn

Yu t nh hng trong vic thit k: tcdliu vkhong cch

Bng thng Bng thng cao th tcdliu cao Suy yu truyn dn

Nhiu (nhiu nhit, nhiuiu ch, nhiu xuyn knh, nhiu xung) Sthit bnhn (receiver)

Trong mi trng hu tuyn, cng nhiu thit bnhn, tn hiu truyn cngmau suy gim

2008 e Cpng: two-wire open line


71/473


Single pair

Flat ribon

Terminating Connector

2008 e Cpng: twisted-pair


72/473


Insulating

outer cover

Multi core

Insulating

outer cover

Protective screen (shield)

Cch in trn mi dyXon li vi nhau

Thng c b li



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ng dng Mi trng truyn dn thng dng nht Mngin thoi

Gia cc thu bao v hp cp (subscriber loop)

Kt ni gia cc ta nh Tngi ni b(Private Branch eXchange PBX)

Mng cc b(LAN)

10Mbps hoc 100Mbps

u nhcim R Ddng lpt, thao tc Tcdliu thp Tm ngn



74/473


c tnh truyn dn Analog

Cn bkhuchi mi 5km ti 6km (suy gim t/h:~1dB/km, chun trongT: 6dB)

Digital

Dng tn hiu tng thoc tn hiu s Cn blp (repeater) mi 2km hoc 3km

Khong cch gii hn

Bng thng gii hn (1MHz)

Tcdliu gii hn (100MHz)

Dbnhiu v tcng ca mi trng ngoi

2008 e Cpng: twisted-pair Khng v bc gip Unshielded Twisted Pair (UTP)


75/473


Khng vbc gip Unshielded Twisted Pair (UTP) DyT bnh thng Rnht Dlpt Dbnhiu trngin tbn ngoi

Vbc gip Shielded Twisted Pair (STP) Vgip bn gip gim nhiu v tcng bn ngoi t hn Kh lpt (cng, nng)



76/473


UTP Cat 3 Lnn 16MHz c dng trong lin lc thoi hu ht

cc vn phng

Chiu di xon (twist length): 7.5cm ti10cm UTP Cat 4

Lnn 20 MHz

UTP Cat 5 Lnn 100MHz c dng ph bin hin nay trong cc

vn phng Chiu di xon: 0.6cm n 0.85cm

Thch hp cho tc truyn lnn 100Mbps (LAN)

STP Cat 3: thch hp cho tc truynlnn 10 Mbps

2008 e Cpng: twisted-pair cable


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Cable standards

Ten Loai Mbps Thng c dung

Category 1 UTP 1 ModemCategory 2 UTP 4 Token Ring-4

Category 3 UTP 10 10Base-T Ethernet

Category 4 STP 16 Token Ring-16Category 5 UTP 100 100Base-T Ethernet

Category 5 STP 100 100Base-T Ethernet

Category 5e UTP 100 1000Base-T EthernetCategory 6 UTP 200 1000Base-T Ethernet

Category 7 STP 600 1000Base-T Ethernet

2008 e Cp ng: coxial


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2008 e Cp ng: coxial


79/473


ng dng Mi trng truyn linh hot nht Cp truyn hnh Truyn dnT khong cch xa

FDM C thmang ng thi 10.000 cuc gi S b thay th bi cp quang

Kt ni cc thit b khong cch gn Mng cc b

c tnh truyn dn Hiu ng b mt (skin effect) Analog

Cn b khuych i mi vi km Khong cch cng ngn nu tn s cng cao Ln n 500MHz

Digital Cn b lp (repeater) mi km Khong cch cng ngn nu tc d liu cng tng

2008 e Cp ng: c im chung


80/473


T l bit li trn ng truyn (Bit Error Rate BER) vo khong 10-6.

D b nh hng ca nhiu (crosstalk,thermal,...) v mi trng xung quanh.

Tc truyn thng tin thay i ty theo phm

vi h thng c trin khai : LAN: tc 10Mbps ~ 100Mbps, khong cch

khong vi trm mt (UTP: length < 100 m). WAN: tc truyn thp hn, t vi chc Kbpsn vi Mbps. V d: T1 ~ 1,5Mbps, E1 ~ 2Mbps,

telephone line: 64Kbps

2008 e Cp quang: cu trcPlasticPlastic


81/473


Single core

Multicore

coating

Optical core Optical cladding

Single core

Multicore

coating

Optical core Optical cladding

2008 e Cp quang: li ch vng dng Li ch


82/473


Dung lng cao Tc d liu hng trm Gbps (so vi 100Mbps trn 1km coaxial cable v thp

hn ca twisted-pair cable) Kch thc v trng lng nh suy hao ca tn hiu trn ng truyn thp. Cch ly trng in t (khng b nh hng ca nhiu v mi trng xung

quanh, kh cu trm) Khong cch gia cc b lp xa T l bit li trn ng truyn vo khong 10-9 10-12

ng dng Phm vi trin khai rt a dng: LAN (vi km), WAN (hng chc km). Mi trng truyn thch hp trin khai cc ng dng mng sa dch v

tch hp bng rng (Broadband Integrated Services Digital Networks) ng trung k khong cch xa Trung k th Trung k tng i nng thn Thu bao

LAN

2008 e Cp quang: c tnh truyn dn


83/473


Sng lan truyn c hng 1014 n 1015 Hz Mt phn ph hng ngoi v ph nhn thy c

Light Emitting Diode (LED)

R

Tm nhit hot ng rng

Tui th cao

Injection Laser Diode (ILD)

Hiu quhn Tc d liu cao hn

Wavelength Division Multiplexing

2008 e Cp quang : ch truynmultimode: several paths/time delays


84/473


narrow: 1 wavelength no time delays

2008 e Cp quang : ch truyn


85/473


Step-indexmultimode Graded-index multimode Single-mode

Ngun sng LED/ILD LED/ILD ILD

Bng thng Rng (ln n

200MHz/km)

Rt rng (200MHz-

3GHz/km)

Cc rng (3GHz-

50GHz/km)Ghp ni Kh Kh Kh

ng dng Truyn d liumy tnh

ng in thoi(khong cch trung bnh)

Vin thng ngdi

Gi thnh R nht Trung bnh t nht

ng knh li(m)

50-125 50-125 2-8

ng knh v(m) 125-440 125-440 15-60

suy gim(db/km)

10-50 7-15 0.2-2

2008 e Cp quang


86/473


2008 e Mi trng truyn dn hu tuyn

h d i i


87/473


c tnh truyn dn im-im

2008 e V tuyn Truyn v nhn thng qua anten

C h Khc phc nhng kh khn va

l khi t i kh i h th


88/473


C hng Chm nh hng (focused beam) i hi s canh chnh hng cn

thn V hng

Tn hiu lan truyn theo mi hng C thc nhn bi nhiu anten

Tm tn s 2GHz n 40GHz

Vi sng (microwave)

nh hng cao im-im V tinh

30MHz n 1GHz V hng

radio 3 x 1011 n 2 x 1014

Hng ngoi Cc b

l khi trin khai h thng T l bit li trn ng truyn

(BER) thay i ty theo h thngc trin khai. V d: BER of

satellite ~ 10-10 Tc truyn thng tin t cthay i, t vi Mbps n hngtrm Mbps

Phm vi trin khai a dng: LAN(vi km), WAN (hng chc km)

Chi ph trin khai h thng banu rt cao

2008 e V tuyn: cc bng tn truyn thng


89/473


2008 e V tuyn: sng viba mt t Cho parabol (thng 10 inch)


90/473


Chm sng nh hng theo ng ngm (line of sight) suy gim t/h

d: khong cch : bc sng

suy gim tl thun bnh phng khong cch cnamplifier/repeater mi 10-100km suy gim thay i theo mi trng (cng tng khi c ma)

Vin thng khong cch xa

Thay th cho cp ng trc (cn t bamp/repeater, nhng phi nmtrn ng thng)

Tn s cng cao th tc d liu cng cao

( ) dBL d 24

log10

=

2008 e V tuyn: sng viba mt t


91/473


Band (GHz) Bandwidth (MHz) Data rate (Mbps)

2 7 126 30 90

11 40 90

18 220 274

iu sut sng viba s

2008 e V tuyn: sng v tinh V tinh l trm trung chuyn

V tinh nhn trn mt tn s khuych i (lp l i tn hiu) v pht trn mt


92/473


V tinh nhn trn mt tn s, khuych i (lp li tn hiu) v pht trn mttn s khc

Cn quo a tnh Cao 35.784 km

ng dng Truyn hnh in thoi ng di Mng ring

c tnh Thng trong khong tn s 1-10 GHz < 1 GHz: qu nhiu nhiu >10 GHz: hp th bi tng kh quyn

Cp tn s thu/pht

(3.7-4.2 downlink, 5.925-6.425 uplink) 4/6 GHz band (11.7-12.2 downlink, 14-14.5 uplink) 12/14 GHz band

Tn scao hn i hi tn hiu phi mnh khng b suy gim Tr240-300ms, ng ch trong vin thng

2008 e V tuyn: v tinh

d

VSAT : very smal aperture terminal


93/473


Satellite

Footprint

Earth

Earth ground

station

Up

link down

link

point-to-point

Satellite

Hub station

point-to-multipoint

Up

link

down

link

down

link

VSAT VSAT

Equatoria

lOrbit

22,300m

iles

2008 e V tuyn: sng radio V hng, 30MHz 1GHz

Antena khng cn c hnh a v khng cn chnh hng


94/473


Antena khng cn c hnh a v khng cn chnh hng

Sng FM

Truyn hnh UHF v VHF

Truyn theo ng ngm (line of sight) B nh hng bi nhiu a knh (multipath)

Phn x

Radio towerRadio tower

Ionosphere

TroposphereRefracted

wave

Reflected

wave

Direct wave

2008 e V tuyn: sng hng ngoi

Truyn theo ng thng (hoc phn x )


95/473


Truyn theo ng thng (hoc phn x) Cn bi cc bc tng

Biu khin TV t xa, cng iu khin bnghng ngoi (IRD port)

2008 e Mi trng truyn dn


96/473


2008 e Lan truyn khng dy

Lan truyn sng mt t


97/473


Lan truyn sng mt t Tn hiu i theo b mt cong ca tri t

Tn sln n 2MHz

AM radio


Sng khng gian


98/473


Sng khng gian Radio nghip d, BBC world, VoA

Tn hiu b tng in ly phn x li mt t

(thc t l b khc x)


Truyn theo ng ngm


99/473


Truyn theo ng ngm Tn s trn 30Mhz

C th truyn xa hn ng ngm nh sng v bhiu ng khc x

2008 e Truyn theo ng ngm

Khong cch max ca ng ngm


100/473


Khong cch max ca ng ngm

h: chiu cao ca anten k: hng s hiu chnh khc x ca sng (k=4/3)

V d: thp anten cao 100m c th truyn n mt

im trn mt t cch xa 41km

Khong cch max gia 2 anten

h1, h2:chiu cao cc anten

khd 57.3=

)21(57.3 khkhd +=

2008 e Truyn theo ng ngm Suy gim tn hiu trong khng gian

Tn hiu b phn tn theo khong cch


101/473


g i vi cng 1 anten, suy gim cng nhiu i vi tn s thp (bc sng di)

Hp th ca kh quyn Hi nc v oxy hp th sng v tuyn

Hi nc nh hng ln nht ti 22GHz, t hn i vi tn s


102/473


2008 e c thm

W Stallings Data and Computerth


103/473


W. Stallings, Data and ComputerCommunications (7th edition), Prentice Hall

2004, chapter 3, 4, 5

B. Brown, Introduction to Data

Communications

Web pages from ITU-T on V. specification

2008

e


104/473

BKTP.HCM

Chng 3 K thut m ha tn hiuD liu s, tn hiu sD

liu s, tn hiu tng t

D liu tng t, tn hiu sD liu tng t, tn hiu tng t

2008

eTn hiu analog

Ba c im chnh ca tn hiuanalog bao gm


105/473


analog bao gm

Bin

(Amplitute)

Tn s

(Frequency)

Pha (Phase)

Bin

ca tn hiu analog

o

mnh ca tn hiu, n v: decibel

(dB) hay volts

Bin

cng ln, tn hiu cng c cng

mnh

Tn hiu ting ni -

t

hello

Ting ni (speech) l

mt tn hiu rt

phc tp

Ting ni cha hng ngn t

hp khc

nhauca nhiu tn hiu

2008

eTn s ca tn hiu analog Tc thay i ca tn hiu


106/473


trong mt giy, n v Hz

hay s

chu k

trong mt

giy (cycles per second)

T/h 30Hz thay i 30 ln trongmt giy

Mt chu k

l

s

di chuyn

sng ca tn hiu timngun bt u cho n khiquay tr

v

li im ngun

.

2008

ePha ca tn hiu analog

Tc thay i quan h catn hiu i vi thi gian


107/473


tn hiu i vi thi gian,c m ttheo (degree)

S dch pha xy ra khi chuk ca tn hiu cha kt

thc, v

mt chu k

mi ca

tn hiu bt u trc khichu ktrc cha hontt

Tai ngi khng cm nhnc s

dch pha

T/h mang d

liu b nh

hng bi s

dch pha

V

d

cc mi ni khng hon

ho s

gy ra dch pha

2008

eTn hiu digital

Tn hiu s bao gm chhai trng thi, c din t


108/473


vi hai trng thi ON hay OFF hoc l 0 hay 1Tn hiu s

yu cu khnng bng thng ln hn tn

hiu analog.

2008

eTn hiu digital

Cc vn khi s dng knh thoi (voice channel) trong victruyn tn hiu s


109/473


truyn tn hiu s

Mt tn hiu s

l

mt t

hp ca cc tn hiu khc.c bit, tn

hiu s

c

thc biu din nhsau

Signal = f + f3

+ f5

+f7

+f9

+f11

+f13

....f

Do mt tn hiu s

gm 1 tn scbn (f), cng thm tn s

3f

(hi tn bc 3), cng thm tn s

5f (hi tn bc 5),

Nu bin

ca tn s

f,

f3

, f5

,

l

a,

a3

, a5

,

th

a

= 3a3

= 5a5

gi tn hiu s

qua knh truyn thoi, bng thng ca knh

truyn phi cho php tn scbn f, tn s

3f v

tn s5f i qua

m

khng nh hng nhiu n cc tn s

ny

y l

yu cu ti thiu

bn nhn nhn ng c tn hiu s

2008

eTn hiu digital


110/473


Truyn 1 tn hiu s

nh

phn tc

2400bps trn knh thoi c bng

thng 3.1kHz

Tn scbn: 1200Hz (thng thng bng

tc

bit)

Ch

c

tn scbn i qua m

khng bthay i

2008

eD liu, tn hiu v truyn dn Analog data/Analog Signal

Gi bnh thng hoc m ha vo phn ph khc Analog and digital


111/473


Analog data/Digital Signal

M ha dng bcodec

to ra chui bit s

Digital Data/Analog Signal

c m ha dng modem

to ra t/h tng t

Digital Data/Digital Signal

Biu din trc tip d

liu hoc m ha

to ra t/h s

c

c tnh mong mun

Analog Signal/Analog Transmission

Lan truyn thng qua cc b

khuch i, xl t/h nh

nhau bt k

d

liu l

s

hoc tng t

Analog Signal/Digital Transmission

Gi

s

t/h biu din d

liu s, lan truyn qua cc b

repeater

Digital Signal/Analog Transmission

Khng dng

Digital Signal/Digital Transmission

T/h l

chui nh

phn lan truyn qua cc b

repeater

g g

transmission

Analog

data

Analog

signal

Digital

signal

Digital

data

Analog

signal

Digital

signal

2008

eD liu s, tn hiu s

Analog and digital

transmission

Analog

dataAnalogAnalogAnalog

signalsignalsignalDigitalDigitalDigital

signalsignalsignal

Digital


signalsignalsignal

DigitalDigital

signalsignal Tn hiu s

Xung in p ri rc khng lin tc


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data signalsignalsignal signalsignal Xung in p ri rc, khng lin tc Mi xung l mt phn t tn hiu D liu nhphn c m ha thnh cc phn t tn hiu

2008

eThut ng

Unipolar Tt c cc phn t t/h c cng du


113/473


p

g

Polar

Mt trng thi logic c biu din bng mc in p dng, trng

thi logic khc c biu din bng mc in p m

Tc

d

liu

Tc

truyn dn d

liu theo bps (bit per second)

rng (chiu di 1 bit)

Th

i gian thi

t b

pht dng

truy

n 1 bit

Tc iu ch

(tc

tn hiu)

Tc

mc t/h thay i

n v

l

baud = s

phn t

t/h trong 1 giy

Mark v

Space

Tng ng vi 1 v

0 nh

phn

2008

eDin gii tn hiu

Cn bit


114/473


nh thi ca cc bit (khi no chng bt u v kt thc) Mc tn hiu tng ng vi bit 0, 1

Yu t nh hng n vic din gii t/h

Ts SNR: cng ln th BER cng gim Tc d liu (bps): cng tng th BER cng tngBng thng: cng ln th

tc

d

liu cng tng

2008

eNonreturn to Zero (NRZ)

Nonreturn to Zero-Level (NRZ-L)

2 mc in p khc nhau cho bit 1 v bit 0 in p khng thay i trong thi khong bit Khng c transition (no return to 0V level)


115/473


Khng c

transition (no return to 0V level)

Bit 0

khng c in p; bit 1 in p dng

Thng thng, in p m dng cho bit 0 v in p dng dng cho bit 1

Nonreturn to Zero Inverted (NRZI)

NRZI cho cc bit 1

Xung in p hng s

sut thi khong bit

D

liu c m cn c

vo vic c

hay khng sthay i t/h u thi khong bit

Thay i t/h (LH hoc HL) m ha nh

phn 1

Khng c thay i t/h m ha nh

phn 0

Mt v

d

cho m ha sai phn (differential encoding)

2008

eNonreturn to Zero (NRZ)

M ha sai phn D liu c biu din bng s thay i mc t/h (thay v


116/473


D liu c biu din bng sthay i mc t/h (thay v bng mc t/h)

Nhn bit sthay i d

dng hn so vi nhn bit mc

Trong cc h thng truyn dn phc tp, cm gic cctnh d dng b

mt

u v nhc im ca m ha NRZ u D dng nm bt Bng thng dng hiu qu Nhc C thnh phn mt chiu Thiu khnng ng b Dng trong vic ghi bng t, USB t dng trong vic truyn t/h

2008

eMultilevel Binary

Dng nhiu hn 2 mc tn hiu Bipolar-AMI (Alternate Mark Inversion)


117/473


p ( )

0 c biu din bng khng c t/h

1 c biu din bng xung dng hay xung m

Cc xung 1 thay i cc tnh xen k Khng mt ng b

khi d

liu l

mt dy 1 di (dy 0 vn b

vn

ng b)

Khng c

thnh phn mt chiu

Bng thng thp

Pht hin li d

dng

Pseudoternary

1 c biu din bng khng c t/h

0 c biu din bng xung dng m xen k

nhau

Khng c u im v nhc im so vi bipolar-AMI

2008

eMultilevel Binary

Trade Off Khng hiu qu bng NRZ


118/473


g q

g

Mi phn t

t/h ch

biu din 1 bit

H thng 3 mc c th biu din log2 3 = 1.58 bit B

thu phi c

khnng phn bit 3 mc (+A, -A, 0)

Cn thm khong 3dB cng sut t c cng xcsut bit li ca binary code

2008

eBiphase: Manchester

Manchester Thay i gia thi khong bit


119/473


Thay i c dng nht/h ng b

(clock) v

d

liu

LH biu din 1

HL biu din 0

Dng trong IEEE 802.3 (ethernet)

2008

eBiphase: Differential Manchester

Differential Manchester Thay i gia thi khong bit chdng cho ng b


120/473


y g g g g Thay i u thi khong biu din 0 Khng c thay i u thi khong biu din 1 Dng trong IEEE 802.5 (token ring)

2008

eBiphase

u v nhc im NhcTi thi c 1 tha i trong thi khong 1 bit c th c 2


121/473

2008, Dr. Dinh Duc Anh Vu18

Data Communication and Computer Networks

Ti thiu c 1 thay i trong thi khong 1 bit v

c

th

c

2

Tc iu ch

ti a bng 2 ln NRZ

Cn bng thng rng hn

u

ng b

da vo sthay i

gia

thi khong bit (self clocking)

Khng c

thnh phn mt chiu

Pht hin li

Khi thiu sthay i mong i

2008

eBi tp


122/473


2008

eScrambling

Dng k thut scrambling thay th cc chui tora hng sin p


123/473


g p

Chui thay th

Phi to ra sthay i t/h, dng cho vic ng b ha Phi c nhn din bi b

thu v

thay th

tr

li chui

ban u

Cng

di nhchui ban u

Khng c thnh phn mt chiu Khng to ra chui di cc t/h mc 0Khng gim tc

d

liu

C khnng pht hin li

2008

eB8ZS v HDB3 B8ZS (Bipolar With 8 Zeros Substitution) Da trn bipolar-AMI


124/473



Nu c

8 s

0 v xung in p cui cng trc l

dng, m thnh 000+0+ Nu c 8 s 0 v xung in p cui cng trc l m, m thnh 000+0+

Gy ra 2 vi phm m AMI

C

th

lm ln vi tc ng gy ra bi nhiu

B

thu pht hin v din gii chng nh8 s

0

HDB3 (High Density Bipolar 3 Zeros)Da trn bipolar-AMI

Chui 4 s0 c thay th bng chui c 1 hoc 2 xungtheo quy tc:

Nu s

bit 1 k

t

ln thay th

cui cng l

l:

0000

-> 000V

Nu s

bit 1 k

t

ln thay th

cui cng l

chn:

0000

-> B00V

2008

eB8ZS v HDB3


125/473



2008

eBi tp


126/473



2008

eD liu s, tn hiu tng t ng dng Dng truyn d liu s trn

Analog and digital

transmission

Analog


signalsignalsignalDigitalDigitalDigital

signalsignalsignal


127/473


mng in thoi cng cng

300Hz 3400Hz

Thit bMODEM (MOdulator-DEMulator)

K

thut

iu bin: Amplitude-Shift Keying(ASK)

iu tn: Frequency-Shift Keying(FSK)

iu pha: Phase-Shift Keying(PSK)

Digital

Analog

FSK PSKASK

QAM

data signalsignalsignal signalsignalsignal

Digital

data

AnalogAnalog

signalsignal

DigitalDigitalDigital

signalsignalsignal

2008

eiu bin (ASK)

Dng 2 bin khc nhau ca sng mang biudin 0 v 1 (thng thng mt bin bng 0)


128/473


S dng mt tn s sng mang duy nht Phng php ny ch

ph

hp trong truyn s

liu

tc thp (~1200bps trn knh truyn thoi) Tn s ca tn hiu mang c dng ph thuc vochun giao tip ang c sdng

K thut c dng trong cp quang LED: sng, khng sng ILD: 2 mc sng khc nhau

00

1)2cos(

)( binary

binarytfA

ts cc

2008

eiu bin (ASK)


129/473


2008

eiu bin (ASK)


130/473


Ta c

Do ,

2008

eiu tn (FSK)

S dng hai tn s sng mang: tn scao tng ng mc 1,tn s thp tng ng mc 0.


131/473


t li hn so vi ASK

c s

dng truyn d

liu tc

1200bps hay thp hn

trn mng in thoi

C

th

dng tn scao (3-30MHz)

truyn trn sng radio

hoc cp ng trc

0)2cos(

1)2cos()(

2

1

binarytfA

binarytfAts

c

c

2008

eiu tn (FSK)


132/473


2008

eiu tn (FSK)

Vi


133/473


Do,

2008

eiu pha (PSK)

S dng mt tn s sng mang v thay i pha ca sng mang ny

0)2cos(

1)2cos()(

binarytfA

binarytfAts

c

c


134/473


PSK sai phn (differential PSK) thay i pha tng i so vi sng

trc (thay v so vi sng tham chiu cnh)

Cho php m ha nhiu bit trn mi thay i tn hiu sng mang (PhaseAmplitude Modulation)

Phng php ny thng c dng trong truyn d

liu

tc

2400bps (2 bits per phase change - CCITT V.26) hoc 4800bps (3 bitsencoding per phase change - CCITT V.27) hoc 9600bps (4 bits encoding

per phase/amplitude change)

Tng qut cho m ha NRZ-L

)( yfc

elementssignaldifferentofnumber:L

elementsignalperbitsofnumber:

(bps)ratedata:R

(bauds)ratemodulation:D

Llog

RRD

2 ll

2008

eiu pha (PSK)


135/473


2008

eiu pha (PSK)


136/473


Dng

Ta c,

2008

eiu pha (PSK)

Quadrature PSK (QPSK)


137/473


Multilevel PSK H

thng 64 v

256 trng thi

Ci thin tc

d

liu vi bng thng khng i

Tng khnng tim n li

11)2702cos(

10)1802cos(

01)902cos(

00)02cos(

)(

tfA

tfA

tfA

tfA

ts

c

c

c

c

2008

eHiu sut

Bng thng Bng thng ASK v PSK lin quan trc tip vi tc bitB (1+r)R


138/473


BT

= (1+r)R

Bng thng FSK c quan h vi tc d liu i vi cctn s thp, c

quan h

vi

sai lch ca cc tn siu

chi vi tn s

cao

BT

= 2F + (1+r)R

Tn hiu nhiu mcBT= (1+r)R/l = (1+r)R/log2

L

Trong trng hp c

li, tc

li ca PSK v

QPSK cao hn khong 3dB so vi ASK v FSK

2008

eQuadrature Amplitude Modulation (QAM)

QAM c dng trong ADSL v mt s h thng wireless Kt hp gia ASK v

PSK

M rng logic ca QPSK


139/473


Gi ng thi 2 tn hiu khc nhau cng tn s

mang

Dng 2 bn sao ca sng mang, mt ci c dch i 90 Mi sng mang c iu ch

ASK

2 tn hiu c lp trn cng mi trng

Gii iu ch

v

kt hp cho d

liu nhphn ban u

2008

eD liu tng t, tn hiu s ng dng Dng truyn d liu tng t trn

mng truyn d liu sT d i t d

Analog and digital

transmission

Analog


signalsignalsignal

DigitalDigital

signalsignal


140/473


Tn dng cc u im ca truyn dn s

(thit b r, dng repeater, TDM, )

S

ha

D

liu s

c

th

truyn dng NRZ-L hay

cc loi m khc

Thit b

CODEC (COder-DECoder)

K thutiu chxung m: Pulse Code

Modulation (PCM)

iu ch

Delta: Delta Modulation (DM)

Analog

Digital

DMPCM

Digital

data

AnalogAnalogAnalog

signalsignalsignal

DigitalDigitalDigital

signalsignalsignal

2008

eiu ch xung m (PCM)

L thuyt ly muNu tn hiu f(t) c ly mu u vi tc

ly mu cao

hn ti thiu 2 ln tn s cao nht ca tn hiu, th cc


141/473


mu thu c cha thng tin ca tn hiu ban u. T/h

f(t) c thc ti to, dng b lc thng thpCng thc Nyquist: N >= 2f

N: tc

ly mu

f: tn s

ca tn hiu c ly mu

D

liu ting ni

Gii hn tn s


142/473


2008

eiu ch xung m (PCM)


143/473


PAM (Pulse Amplitude Modulation)

Cc xung c ly mu

tn s

R=2B

Lng t

ha cc xung PAM

Xc nh gi

tr

ca im c ly mu, ri vo khong no th

ly gi

tr

khong Ty thuc vo cc mc lng t

2n

(n l

s

bit cn thit

s

ha 1 xung)

M ha d

liu

Thc hin cc thao tc m ha thng tin trc khi truyn i

Nhiu lng t

(quantizing noise)

SNR = 6.02n + 1.76 (dB)

Mi bit dng thm cho lng t

ha stng SNR 6dB

2008

eiu ch xung m (PCM)


144/473


2008

eNon-Linear encoding

Mc lng tkhng u Gim mo tn hiu Companding (compressing-expanding)


145/473


p g ( p g p g)

2008

eCompanding


146/473


2008

eiu ch Delta (DM) Tn hiu tng tc xp xbi hm cu thang(staircase) Hnh vi nh phn


147/473


Hnh vi nh

phn

i ln hay xung 1 mc () ti mi thi khong ly mu Hiu sut

ti to ting ni tt

PCM -

128 mc (7 bit)

Bng thng thoi 4khz

Cn 8000 x 7 = 56kbps i vi PCM

K

thut nn d

liu c

th

lm gim tc

bit

V

d: k

thut m xen khung (interframe coding) cho video lm

gim tc

bit t

92Mbps xung 15Mbps

2008

eiu ch Delta (DM)


148/473


2008

eD liu tng t, tn hiu tng t ng dng Dng iu ch d liu tngt: thay i tn s truyn (tn s

cao hn truyn dn tt hn)

Analog and digital

transmissionAnalog

data

AnalogAnalog

signalsignalDigitalDigitalDigital

signalsignalsignal

Digital AnalogAnalogAnalog DigitalDigitalDigital


149/473


y ) Dng cho FDM K thut

iu chbin: Amplitude

Modulation (AM) iu ch gc (Angle Modulation) iu ch tn s: FrequencyModulation (FM) iu ch pha: Phase Modulation(PM)

Analog

Analog

AngleAM

PMFM

data signalsignalsignal signalsignalsignal

2008

eiu ch bin (AM) Bin ca sng mang c thay i bi bin ca tn hiu ctruyn is(t) = [1+na

x(t)]cos(2fc

t)

To ra t/h 2 bn (DSBTC), trong chcn c mt bn na


150/473


a

n

a

>1

t/h bao ct trc thi gian (thng tin b

mt)

Pt

= Pc

(1+na2/2)

Pt

v

Pc

cng sut t/h c truyn i v

t/h sng mang

na

ch

siu ch, t

sbin t/h c truyn v

sng mang

Single sideband (SSB) v

double sideband suppress carier (DSBSC)

u im D

hin thc (iu ch

v

gii iu ch)

D

bin i tn hiu sang cc gii bng tn khc nhau

Khuyt

im

D

b nh hng ca nhiu

Khng s

dng hiu qunng lng

2008

eiu ch bin (AM)

M(f)


151/473


fB

M(f)

ffc

B fc

+ Bfc

Uppersideband

Lowersideband

Discrete carrier

term

2008

eiu ch gc s(t) = Ac cos[2fc t + (t)]

Phng php iu tn s

(FM)

o hm ca pha (t) tl thun vi tn hiu c truyn i

1


152/473


(t) = nf

m(t)

u im

Kh

b nh hng ca nhiu

S

dng hiu qunng lng

Khuyt im

Tn hiu c iu ch

yu cu bng thng rng hn nhiu tn hiu

truyn i ban u (d

liu)

Hin thc mch iu ch

v

gii iu ch

phc tp hn so vi phngphp iu bin

)('2

1)( tftf

ci

2008

eiu ch gc


153/473


2008

eiu ch gc Phng php iu ch pha (PM)

(t) = np

m(t)

Tn hiu truyn i khng nh hng n thnh phn bin v tn sm chlm thay i pha ca sng mang


154/473


Ph

tn s

ca tn hiu c iu chtheo phng php iu pha

tng tnhphng php iu tn phng php iu pha cngc

cc c im tng tphng php iu tn

Tuy nhin, c hai l do phng php iu pha c d

chp nhn

hn

i vi bn nhn: tn s

ca tn hiu nhn c l cnh, ch

c phathay i nn ch

cn thit k

b

lc tn s

ch

cho mt tn s

duy nht thay

v

nhiu tn snhtrong phng php iu tn gim chi ph

thit k

v

hin thc mchTrong trng hp tn hiu iu ch

ch

nhn mt s

gi

tr(nhtn hiu

s), mch iu ch v gii iu ch hin thc theo phng php iu phac n gin rt nhiu

2008

eHiu sut

Bng thng AM BT = 2B


155/473


T

FM&PMBT

= 2(+1)B

FM&PM cn bng thng ln hn so vi AM

FMB

An

B

F

PMAn

mf

mp

2

2008

ec thm

W. Stallings, Data and ComputerCommunications (7th edition), Prentice Hall2004, chapters 5


156/473


, p

2008

e


157/473

BKTP.HCM

Ch

ng 4 Cc k thut truyn d liu s

Truyn bt ng b v truyn ng bCc loi liPht hin liSa liCu hnh ng truynGiao tip

2008

eTruyn d liu song song Mi bit dng mt ng truyn ring. Nu c 8 bits c truynng thi s

yu cu 8 ng truyn c lp

truyn d liu trn mt ng truyn song song, mt knhtruyn ring c dng thng bo cho bn nhn bit khi no d


158/473


liu c sn (clock signal)

Cn thm mt knh truyn khc

bn

nhn bo cho bn gi bit l snsng

nhn d

liu k

tip

2008

eTruyn d liu tun t Tt c cc bit u c truyn trn cng mt ng truyn,bit ny tip theo sau bit kia

Khng cn cc ng truyn ring cho tn hiu ng b

v

tn

hiu bt tay (cc tn hiu ny c m ha vo d liu truyni)


159/473


i)

Vn nh thi (timing) i hi phi c cchng b

giabn truyn v

bn nhn

2 cch gii quyt

Bt ng b: mi k tc ng b

bi start v stop bit

ng b: mi khi k tc ng b

dng c

2008

eTruyn bt ng b

D

liu c truyn theo tng k t

trnh vic mt ng b

khi nhn

c chui bit qu

di

5 8 bits

Ch

cn ging b

trong mt k t

Ti ng b cho mi k t mi Hnh vi


160/473


Hnh vi

i vi dng d

liu u, khong cch gia cc k t

l ng nht (bng

chiu di ca phn t

stop)

trng thi rnh, b

thu pht hin s

chuyn 1 0

Ly mu 7 khong k

tip (chiu di k t)

i vic chuyn 1 0 cho k t

k

tip

Hiu sut

n gin

R

Ph

tn 2 hoc 3 bit cho mt k t

(~20%)

Thch hp cho d

liu vi khong trng gia cc k t

ln (d

liu nhp t

bn phm)

2008

eTruyn bt ng b


161/473


2008

eTruyn bt ng b

ng b khung (frame synchronization): dngcc k tiu khin (STX, ETX, DLE)STX F R L ETX


162/473


Start bit Stop bitSTX

ETX

F Frame contents

(printable characters)

STXDLE DLE ETX

DLE

STX

DLE

ETX

Frame contents

(binary data)DLE

DLEInserted

DLE

2008

eTruyn ng b

Truyn khng cn start/stop Phi c tn hiu ng b ng b bit (bit synchronization): s dng ccphng php sau


163/473


p g p p

Tch hp xung clock vo d

liu truyn i

Tch hp thng tin ng b

(clock) vo trong d

liu truyn

u nhn s

tch thng tin ng b

da vo d

liu nhn c

Manchester, differential Manchester, tn s

sng mang (analog)

S dng ng clock ring Dng mt ng tn hiu ng b

ring bit

Mt bn (pht hoc nhn) to ra cc xung clock ng b

vi cc bit

truyn i trn ng clock ring

Bn cn li dng tn hiu trn ng clock ring

lm clock

Thch hp khi truyn trong khong cch ngn

Tn hiu ng b

d

b

suy gim trn ng truyn

2008

eTruyn ng b

ng b frameMi block d

liu c bt u bng mt c

gi l

preamble, kt

thc bng mt c

gi l

postamble

Preamble v postamble l mt mu bit (bit pattern) c quy nh


164/473


snMt chui cc k t

SYN (16h trong bng m ASCII)

Mu bit 11111110

Frame: d

liu + preamble + postamble + thng tin iu khin

Hiu quhn so vi truyn bt ng b (ph tn thp hn cho ccbit iu khin)

HDLC: 48 bit iu khin cho mi block 1000 k t

(8000 bit)

2008

eCc loi li xy ra trn ng truyn

Mi trng truyn dn b

nhiu (in, t, ) d

liu nhn

c

li (cc bit bthay i)

2 cch khc phc khi pht hin c

li

Forward error control: thng tin sa sai c thm vo cc k t

hoc

cc frame truyn i, bn nhn c th pht hin khi no c li va linm u sa (c khnng sa li)


165/473


Feedback (backward) error control: thng tin sa sai c thm vocc k t hoc cc frame truyn i ch

pht hin khi no c

li

(khng c

khnng sa li). Cch

yu cu truyn li k t/frame sai

c dng trong trng hp ny

Phn loi li

Li 1 bit Ch

1 bit b

li, khng nh hng cc bit xung quanh

Thng xy ra do nhiu trng

Li chm (busrt error)

Mt chui lin tc B bit trong bit u, bit cui v

cc bit bt k

nm gia

chui u b li

Thng xy ra do nhiu xung

nh hng cng ln i vi tc

truyn cao

Bit error rate (BER): xc sut mt bit nhn c b

li

2008

eCch pht hin li


166/473


2008

ePht hin li bng bit parity

1 bit parity c thmvo 1 khi d liu cntruyn i Bit parity


167/473


Parity chn: tng s bit 1c trong khi d liu, k c bit parity, l s chnParity l: tng s

bit 1 c

trong khi d liu, k c bit parity, l s

l

D a t aD a t a

( ASCII ) B0 B1 B2 B3 B4 B5 B6

Parity bit

(odd )

h 0 0 0 1 0 1 1 0

e 0 1 0 1 0 1 1 1

2008

eParity

c imChd c li sai mts

lbit, khng d c

li sai mt s chn bit


168/473


Khng sa c li

t c dng trong truynd

liu i xa, c bit

tc cao

2008

eCyclic Redundancy Check (CRC)

Nguyn lk-bit message

Bn pht to ra chui n bit FCS (Frame Check Sequence)sao cho frame gi i (n+k bit) chia ht cho 1 s xc nh


169/473


trc

Bn thu chia frame nhn c cho cng 1 s

v

nu

khng c

phn dth

c

khnng khng c

li

S hc modulo 2Exlusive-or

1010

0101-

1111

1 1 0 0 1

x 1 1

1 1 0 0 1

1 1 0 0 1

1 0 1 0 1 11010

0101+

1111

2008

eCRC dng s hc Xc nh FCS

T: frame c truyn (k+n bit)

D: message, d

liu cn truyn (k bit u ca T)

F: FCS (n bit sau ca T)


170/473


P: schia c xc nh trc (n+1 bit)

Gi s

Suy ra nu ly th T chia ht P

Kim tra li?

P

R

QP

Dn2

FDn2T

RF

2008

eCRC dng s hc V d: D = 1010001101 (10 bit) P = 110101 (6 bit)


171/473


F =? (? bit)n = 6-1 = 5 bit, k = 10 bit, n+k = 15 bitp s: F = 01110

D liu T = 101000110101110

2008

eCRC dng s hc S chia P Di hn 1 bit so vi FCS mong mun c chn ty thuc vo loi li mong mun pht hin Yu cu ti thiu: msb v lsb phi l 1


172/473


Biu din li Li = nghch o bit (i.e. xor ca bit vi 1)Tr

= T + E

T: frame c truyn

Tr

: frame nhn c

E: error pattern vi 1 ti nhng v

tr

li xy ra

Nu c

li xy ra (E

0) th

b

thu khng pht hin ra li

khi v

ch

khi Tr

chia ht cho P, ngha l

E chia ht cho

P

kh c khnng xy ra

2008

eCRC dng a thc

Cch khc

xc nh FCS: a thc

D=110011 D(x) = x5+x4+x+1P=11001 P(x) = x4+x3+1

V

d

D liu cn truyn: 1001001 (k = 7 bits) a thc biu din:6 3


173/473


D(x) = x6+ x3+ 1

Cho a thc sinh: P(x) =x3

+ 1 (n = 3 bits)

D

liu D dch tri n bits:

xn D(x) = X9 + X6 + X3

FCS = 001

D

liu T c truyn: 1001001001

2008 e

Cyclic Redundancy Check

Cc li c pht hin Tt c cc li bit n Tt c cc li kp nu P(x) c t nht 3 ton hng Mt s l li bt k nu P(x) cha 1 tha s (x+1)


174/473


Bt k li chm no m chiu di ca chm nhhn hoc bng chiu di FCS

Hu ht cc li chm ln hn

CRC l mt trong nhng phng php thngdng v hiu qu nht pht hin li

2008 e

Cyclic Redundancy Check

4 a thc sinh c s dng rng riCRC-12 = X12

+ X11

+ X3

+ X2

+ X + 1

12-bit FCS

Dng truyn chui cc k t c di 6-bit

CRC 16 X16 X15 X2 1


175/473


CRC-16 = X16

+ X15

+ X2

+ 116-bit FCS

Dng

truyn chui cc k t

c

di 8-bit

USA

CRC-CCITT = X16

+ X12

+ X5

+1

Europe

CRC-32 = X32

+ X26

+ X23

+ X22

+ X16

+ X12

+ X11

+ X10

+ X8

+ X7+ X5

+ X4

+ X2

+ X + 1

32-bit FCS

Point-point synchronous transmission, DVB-T

2008 e

CRC dng mch sD=1010001101P=110101

2

1

C1

C1

C0

C0 C4* C3 C2* C1 C0* Input

Initial 0 0 0 0 0 1

Step 1 1 0 1 0 1 0

Step 2 1 1 1 1 1 1


176/473


1010001101

x2

x4

x5

C4C4

C3C3

+

C2C2

+

+

Step 2 1 1 1 1 1 1Step 3 1 1 1 1 0 0

Step 4 0 1 0 0 1 0

Step 5 1 0 0 1 0 0

Step 6 1 0 0 0 1 1Step 7 0 0 0 1 0 1

Step 8 1 0 0 0 1 0

Step 9 1 0 1 1 1 1

Step 10 0 1 1 1 0

2008 e

Sa li

Cch sa li thng thng l yu cu truyn li khid liu b li Khng thch hp cho cc ng dng trao i d liukh d


177/473


khng dyXc sut li cao, dn n vic phi truyn li nhiu

Thi gian tr

truyn ln hn nhiu thi gian truyn 1 khi

d

liu

Cch

truyn li l

truyn li khi d

liu b

li v

nhiu

khi d

liu khc tip theo

Cn thit sa li da vo cc d

liu nhn c

2008 e

Cch sa li


178/473


2008 e

Cch sa li Thm mt sm dtha vo d liu truyn i B thu c khnng suy lun ra d liu gc ban ukhi c li xy ra V d: m sa li block

T t l th bit k bit d li t


179/473


Tng qut l

thm n bit vo sau k bit d

liu cn truyn

To thnh block d

liu (n+k) bit (codeword)

Trong t

m c

cha k bit d

liu gc

Mt s k thut FEC chuyn k bit d liu gc thnh n (n>k)bit tm trong khng xut hin k bit d

liu gc

Chi tit xem chng 6, phn 6.4 Lm gim tc d liu hiu dng

Code rate: k/(n+k)

2008 e Giao tip

Giao tip

Thit b

x

l d

liu (DTE) thng

khng c

cc phng tin pht d

liu, v

ch pht cc t/h sn gin nhNRZ-L

Cn mt thit b

giao tip (DCE)

v

d: modem, NIC,

DCE pht cc bit d

liu trn mi trng truyn dn

DCE trao i d liu v thng tin iu khin vi DTE

c thc hin thng qua mch trao iC h i i


180/473


c thc hin thng qua mch trao i

Cn mt chun giao tip r rng

c tnh

Ckh

Kt ni vt l, cc u kt ni

in in p, nh thi thay i cc mc in th, m ha,

Chc nng

ngha ca mi chn kt ni

D

liu, iu khin, nh thi, GND,

Th

tc

Chui cc s

kin xy ra khi truyn d

liu

2008 e Giao tip


181/473


2008 e Chun V.24/EIA-232-F

Chun giao tip c s

dng rng ri, quy nh bi

ITU-T ITU-T chc t chc nng v th tc V.24 tham kho cc chun khc cho cc c tnh ckh v

c tnh in

EIA 232 F (USA)


182/473


EIA-232-F (USA) RS-232c tnh ckh: ISO 2110

c tnh in: v.28 Chc nng: v.24

Th

tc: v.24

Dng

kt ni DCE vi modem s

dng trn ng dy

in thoi

2008 e c tnh ckh

DB-25 femaleDTE)


183/473


2008 e c tnh in

Dng tn hiu s Cc gi trc hiu l d liu hoc iu khin tythuc vo mch NRZ-L

>+3V 0


184/473


>+3V

0

+3V

on


185/473


108.2 CD DTE ready DCE DTE is ready to operate

125 CE Ring indicator DTE DCE is receiving a ringing signal on the

channel line

109 CF Received line signal detector DTE DCE is receiving a signal withinappropriate limits on the channel line

Timing signals

113 DA Transmitter sig. elm. timing DCE Clocking signal

114 DB Transmitter sig. elm. timing DTE Clocking signal;

115 DD Receiver sig. elm. timing DTE Clocking signal for circuit 104

Ground

102 AB Signal ground/common return Common ground reference for all circuits

2008 e

Local/Remote loopback testing


186/473


2008 e

Th tc

V

d

modem ring bt ng b, kt ni 2 thit

b khong cch ngn

Ch t t hi


187/473


Chcn mt s tn hiuSignal ground (102)

Transmitted data (103)

Received data (104)

Request to send (105)

Clear to send (106)

DCE ready (107) Received line signal detector (109)

2008 e

Modem ring bt ng b

DCE ready

Request to send

Clear to send


188/473


D

liu

Received line

signal detector

D

liu

200

Documents

Ky Thuat Truyen So Lieu 6889