Kỹ Thuật Truyền Số Liệu - dulieu.tailieuhoctap.vndulieu.tailieuhoctap.vn/books/cong-nghe-thong-tin/the-loai-khac/... · • Giảng viên –Nguyễn Hoà ... • [1] “Tập

BKTP.HCM

2008

dce

K Thut Truyn S Liu

2008

dce

2008, Dr. Dinh Duc Anh Vu 2Data Communication and Computer Networks

Mn hc

M s: 504003

S tn ch: 4

Mn hc trc: khng

Ging vin

Nguyn Ho Hng

Khoa Khoa hc v K thut my tnh

[email protected]

(38647256 ext. 6227 or 5843)

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

Gii thiu

mailto:[email protected]://cse.hcmut.edu.vn/~hungnguyen

2008

dce


Gii thiu mn hc

ng lc S pht trin v bo ca cc ng dng my tnh

S cn thit ca vic trao i thng tin gia cc ni, gia cc my tnh

2008

dce


Gii thiu mn hc

Mc ch Gii thiu cc khi nim, thut ng v cc phng php tip cn

c 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 liu c 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: 20%

Thc hnh: 20%

Kim tra cui k: 60%

2008

dce


Ni 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 bt ng b

Tm ng trong mng chuyn mch

2008

dce


Ti liu tham kho [1] Tp slide bi ging, TS. inh c Anh V, 2008

[2] Data and Computer Communications William Stallings (12 chng u)

[3] Data Communications and Computer Networks

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 ngh ATM 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

BKTP.HCM

2008

dce

Chng 1

Tng quan v truyn s liu v

mng truyn s liu

M hnh h thng truyn d liu

Truyn s liu

Mng truyn s liu

Kin trc truyn s liu dng my tnh

2008

dce



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

dce



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: ngha c gn cho d liu

Tn hiu: mt dng biu din ca d liu

Tp hp cc thit b c kt ni thng qua mt mi trng truyn dn

2008

dce


Cc tc v chnh

Ti u 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 hiu c d liu

ng b gia bn truyn v bn nhn im bt u v im kt thc ca tn hiu

Qun l vic trao i d liu Cc giao thc truyn d liu

V d: thc hin cuc gi in thoi

2008

dce


Cc tc v chnh

iu khin dng d liu Tc truyn h thng ch khng b qu ti

Pht hin v sa li

nh v a ch v tm ng a ch l duy nht

Tm ng trong mt mng v gia cc mng

Khi phc Khi phc li trng thi c ca h thng khi c li lm ngt qung

nh dng thng tin (vd: binary code ca m k t)

Bo mt D liu ch c gi n i tng nhn xc nh

Qun tr mng Ci t h thng, qun l trng thi, x l li, c k hoch nng cp

trong tng lai

2008

dce


H thng truyn d liu

Ti sao phi dng h thng truyn d liu Chia s ti nguyn

My in

a/bng t

Cng sut tnh ton

Tp hp d liu

Phn tn ti Tnh ton song song

Tnh ton theo m hnh client-server

Fault tolerance

Chuyn thng tin Giao dch c s d liu

Th in t

Game

Phn tn d liu trn mng lu tr

2008

dce


Truyn s liu

Lin quan n cc vn truyn d liu s dng th Truyn dn d liu (data transmission)

M ha d liu (data encoding)

K thut trao i d liu s (digital data communication)

iu khin lin kt d liu (data link control)

Phn hp (multiplexing) Lin kt (link) hoc mch (circuit)

Knh (channel)

2008

dce


Mng truyn s liu

Giao tip im-im

thng khng thc t

Cc thit b cch xa

nhau

S kt ni tng ng k

khi s cc thit b cn

giao tip ln

Mng truyn s liu

Phn loi da vo

phm vi hot ng

2008

dce


Mng truyn s liu

Mng cc b (Local-Area Networks LAN)

c tnh

Tm vc nh (ta nh, nhiu ta nh)

Thng c s hu bi 1 cng ty, t chc

Tc cao hn WAN

Phn loi

Switch LAN (Ethernet)

Wireless LAN

ATM LAN

2008

dce


Mng truyn s liu

= Brige (cau)

LAN 1

LAN 2

LAN 3

= PC, Work station

a) ng dng trong vn phng

Building A

Building B

Building C

Site-wide (backbone) LAN

2008

dce


Mng truyn s liu Mng din rng (Wide-Area Networks WAN)

Khc nh th no so vi mng LAN? Trin khai theo din rng

Da vo cc mch truyn dn cng cng

Cng ngh Chuyn mch mch in (circuit-switching)

ng truyn dn logic dnh ring gia 2 node mng

Chuyn mch gi (packet-switching) Khng c dnh ring ng truyn dn

Mi gi i theo ng khc nhau

Chi ph ng truyn cao khc phc cc li truyn dn

Frame Relay c dng trong chuyn mch gi c tc li thp

Tc ln n 2 Mbps

ATM Ch truyn bt ng b (Asynchronous Transfer Mode)

Dng cc gi c kch thc c nh (gi l cell)

Tc ln n Gbps

2008

dce


Mng truyn s liu

Mt cch phn loi khc

Da vo kin trc v k thut dng trao i d

liu

Mng chuyn mch (switched networks)

Mng chuyn mch mch in

Mng chuyn mch gi

Mng pht tn (broadcast networks)

Mng radio gi (packet radio net.)

Mng v tinh (satellite net.)

Mng cc b (local net.)

BKTP.HCM

2008

dce

Chng 1

Tng quan v truyn s liu v

mng truyn s liu


Truyn s liu

Mng truyn s liu

Kin trc truyn s liu dng my tnh

2008

dce


V d kin trc phn cp

2008

dce


Kin trc truyn thng my tnh

Trong ng dng truyn file, nhng cng vic phi lm l Ngun thit lp kt ni (bo cho mng bit u l ch)

Ngun m bo ch sn sng nhn d liu

ng dng truyn file trn h/t ngun phi m bo chng trnh qun l file trn h/t ch sn sng nhn v lu tr file

Nu nh dng file dng trn 2 h/t khng tng thch, mt hoc c 2 h/t phi thc hin chc nng chuyn i

Tc v giao tip c phn nh thnh cc mun

V d, truyn file c th c phn thnh 3 mun Truyn file

Dch v giao tip

Truy xut mng

2008

dce


Nghi thc giao tip (protocol)

Dng giao tip gia cc thc th trong mt h thng Thc th

C kh nng gi/nhn thng tin

ng dng ngi dng

Th in t

Thit b u cui

H thng

i tng vt l, cha mt hoc nhiu thc th

My tnh

Thit b u cui

Cm bin t xa

Phi cng ni mt ngn ng

Cc thnh phn chnh ca mt nghi thc giao tip Ng php (syntax)

nh dng d liu

Mc tn hiu

Ng ngha (semantic)

Thng tin iu khin

X l li

nh thi (timing)

ng b

Tun t

2008

dce


M hnh n gin 3 lp

Lp truy xut mng

Lp vn chuyn

Lp ng dng

2008

dce


Lp truy xut mng

Trao i d liu gia my tnh v mi trng

mng

Cung cp a ch my nhn, tm ng i

Yu cu cc dch v t mi trng mng

(priority)

Ph thuc vo loi mng ang s dng (LAN,

chuyn mch gi, mch)

2008

dce


Lp vn chuyn

m nhn vic truyn d liu tin cy

D liu n ng a ch

Theo th t gi

Khng ph thuc vo loi kt ni mng bn

di

Khng ph thuc vo ng dng

2008

dce


Lp ng dng

Cung cp cho cc ng dng cc dch v

truy cp mng

Web browser: HTTP

Email: SMTP

File: FTP

2008

dce


Kin trc 3 lp

2008

dce


Protocol data unit (PDU)

Ti mi lp c nhiu protocol c s dng

D liu ngi dng phi c thm vo cc thng tin iu

khin ti mi lp

Lp vn chuyn c th chia nh d liu ngi dng

2008

dce


Hot ng ca kin trc 3 lp

2008

dce


Tiu chun ha Cn thit cho cc tc v lin thng gia cc

thit b

u im Bo m th trng ln cho cc thit b v cc

phn mm

Cho php cc sn phm ca cc nh cung cp c th giao tip vi nhau

Nhc im Hn ch s pht trin cng ngh

C th c nhiu chun cho cng mt cng ngh

2008

dce


Tiu chun ha Cc t chc chun ha

Electronics Industries Association EIA: hip hi cc nh sn xut M, a ra chun RS232 v cc chun tng t

Institute of Electrical and Electronic Engineers IEEE (http://www.ieee.org): t chc nh ngh ca cc k s in-in t (IEEE-802: chun cho LAN/MAN)

International Telecommunications Union ITU (http://www.itu.ch): iu phi cc chun tm quc t, cp pht tn s vin thng v tinh (X.25 protocol: WAN communication)

ISOC: Internet society (http://www.isoc.org): l mt cng ng chuyn nghip gm nhiu t chc con (Internet architecture Board: IAB), a ra rt nhiu cc chun v internet (TCP/IP)

International Organization for Standards ISO (http://www.iso.ch): c nhiu chun lin quan n my tnh (OSI: Open system interconnection)

http://www.ieee.org/http://www.itu.ch/http://www.isoc.org/http://www.iso.ch/

2008

dce


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 th c kh nng giao tip vi cc thc th ngang cp trong

mt h thng khc

Trong mt h thng, mt thc th cung cp dch v cho cc thc th khc v cng s dng

dch v ca cc thc th khc

Nhn mnh vo internetworking, ngha l, khi 2 thc th giao tip khng ni chung mt mng

Quan tm c h thng hng n kt ni v khng kt ni

Bao gm cc ng dng: trao i file (FTP, RCP), m phng terminal (telnet, rlogin), chia s

v truy cp file phn tn (NFS), thc thi lnh t xa (rsh, rexec), in n t xa (lpr), 802.X, X.25,

mail (SMTP), qun tr mng (NSP, SNMP)

TCP/IP c pht trin ng thi vi m hnh ISO

Khng cha cc nghi thc lin quan n 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

Lp ng dng

Lp transport (giao tip gia cc thit b)

Lp Internet

Lp truy xut mng

Lp vt l

2008

dce


M hnh kin trc nghi thc TCP/IP

2008

dce


Lp vt l Giao tip vt l gia thit b v mi trng truyn

Tnh cht ca mi trng truyn, mc tn hiu, tc truyn

Lp truy xut mng Trao i d liu gia thit b v mng truyn

Cung cp chc nng tm ng gia 2 thit b trong cng 1 network

Yu cu cc dch v t mng truyn (priority)

Lp Internet Cung cp chc nng tm ng gia 2 thit b thuc 2 mng khc

nhau

Cn c hin thc trong cc router

Lp transport m nhn vic truyn d liu tin cy gia 2 ng dng

Chc chn d liu i n ch, cc gi d liu n ng th t gi

Lp ng dng Cung cp cho cc ng dng cc dch v truy cp mng


2008

dce


D liu c truyn qua TCP/IP

2008

dce



2008

dce

M hnh mng ISO/OSI

L mt m hnh tham kho

ISO 7498, nm 1984

M hnh tng ng ca ITU-T l X.200

H thng l thuyt ra i qu tr

TCP/IP ang l tiu chun thc tin (de facto

standard)

2008

dce


M hnh mng ISO/OSI

7 lp ng dng (application)

Trnh by (presentation)

Giao dch (session)

Vn chuyn (transport)

Mng (network)

Lin kt d liu (data link)

Vt l (physical)

Application Layer

Transport Layer

Presentation Layer

Session Layer

Network Layer

Datalink Layer

Physical Layer

Netw

ork

environm

ent

OSI

environm

ent

Real system environment

2008

dce


M hnh mng ISO/OSI

2008

dce


Lp vt l iu khin vic truyn d liu (chui cc bit) thc s trn cp/mng

nh ngha tn hiu in, trng thi ng truyn, m ha thng tin v kiu kt ni c s dng

Thi gian tr truyn Thi gian t/h truyn t ngun n ch

T/h truyn vi vn tc xp x vn tc nh sng C=3x108 m/s

V d

v tinh GEO d=40.000km tr truyn 1/8 s;

cp Ethernet d=1km tr truyn 3s

Li truyn Suy gim cng sut t/h

Suy gim do nhiu

Cc c trng chnh c trng c hc: connector, loi vt liu truyn dn

c trng in: dng biu din ca bit (vd: mc volt), v tc truyn bit

c trng chc nng: chc nng ca cc mch gia h thng v ng truyn

c trng th tc: quy nh cc s kin trong qu trnh truyn bit stream qua ng truyn

Lp ph thuc mi trng truyn dn

2008

dce



Lp lin kt d liu

Chu trch nhim truyn dn mt cch tin cy

(error-free) cc gi d liu ca lp mng trn mt

lin kt n

Khi ng, duy tr v ngt ng truyn

2008

dce



Lp mng

Trung chuyn cc gi gia lp

vn chuyn v lp lin kt d

liu

nh a ch gi v dch a

ch lun l thnh a ch vt l

Tm ng kt ni vi my

tnh khc thng qua mng

Mi node cha mt moun

lp mng cng vi mt moun

lp lin kt d liu cho mt

lin kt

Khng cn thit nu kt ni 2

my trc tip

2008

dce


Lp hng ti ng dng

Lp vn chuyn Cung cp c ch trao i d liu gia 2 h thng

Cung cp dch v gi thng ip (message service) end-to-end cho cc lp trn

Bo m d liu c truyn khng c li, theo th t v khng mt mt, ngt qung hoc d tha

Chu trch nhim ng gi d liu t mt message ln thnh nhiu message kch thc nh hn gi i v tp hp cc message nh thnh mt message ban u khi nhn c (c kh nng a 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 th t cc gi ti ch n

Khi phc li, h hng

iu khin dng t ngun n ch v ngc li

2008

dce


Lp hng ti ng dng

Lp giao dch Cung cp c ch iu khin vic truyn thng ip gia

cc ng dng (tr gip danh b, quyn truy cp, chc nng tnh cc, )

Cho php 2 ng dng to, s dng v xa kt ni

C kh nng nhn dng tn v cung cp cc dch v khc (security, checkpoint, recovery) cn thit cho 2 my tnh ni kt qua mng

Lp trnh by Cung cp nh dng d liu c dng truyn d liu

gia cc my tnh ni mng (chuyn i m k t, m ha d liu, nn d liu)

Lp ng dng Cung cp cho cc ng dng cc dch v truy cp mng

2008

dce


Truyn d liu qua m hnh mng OSI

Presentation layer

Session layer

Application layer

Transport layer

Network layer

Datalink layer

Physical layer

Application process

Presentation layer

Session layer

Application layer

Transport layer

Network layer

Datalink layer

Physical layer

Application process

Data network

Network environment

OSI environment

Real systems environment

Computer I Computer II

2008

dce


D liu c truyn qua mng OSI

2008

dce


So snh m hnh OSI v TCP/IP

2008

dce

Cc giao thc trong m hnh TCP/IP

Ethernet IEEE 802.3.

L chun ph bin nht cho PHY v MAC.

Token Ring iu khin quyn gi nhn message bng token.

IP: Internet Protocol Protocol dng chuyn gi d liu t my ngun n my ch da

trn a ch

ICMP: Internet Control Message Protocol Hin thc da trn IP

Dng gi error message t router hay my ch n my ngun

ARP: Address Resolution Protocol Phn gii a ch IP ra a ch vt l

RARP: Reverse Address Resolution Protocol Xin cp a ch IP cho my. -> DHCP (Dynamic Host Configuration

Protocol)

2008

dce

Cc giao thc trong m hnh TCP/IP

TCP: Transmission control protocol Giao thc truyn nhn d liu tin cy gia cc ng dng

S dng ng truyn lun l tm thi

UDP: User-datagram protocol Truyn d liu khng tin cy

Telnet ng nhp t xa

FTP, TFTP Truyn nhn file

SMTP ng dng gi nhn mail

DNS i tn min thnh a ch IP

2008

dce


Bt li ca m hnh nhiu lp

Processing overhead: d liu phi i qua

nhiu lp t trn xung di

Data overhead: d liu gc c gn thm

cc header ca cc lp

Mt nhiu thi gian xy dng h thng cc

protocol chun cho tng lp

2008

dce


c thm

W. Stallings, Data and Computer

Communications (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

BK TP.HCM

2008

dce

Chng 2

Truyn dn s liu Khi nim v thut ng

Truyn dn d liu tng t v d liu s

Suy hao ng truyn

Dung lng knh truyn

Mi trng truyn dn c nh hng

Truyn dn khng dy

Lan truyn khng dy

Truyn ng thng (line-of-sight)

2008

dce

2008, Dr. Dinh Duc Anh Vu 2 Data Communication and Computer Networks

Thut ng

Thit b

Thit b pht (Transmitter)

Thit b thu (Receiver)

2008

dce


Thut ng

Mi trng truyn (Medium)

Hu tuyn (guided)

V tuyn (unguided, wireless)

2008

dce


Thut ng

Kt ni

Kt ni trc tip (Direct link)

Khng cn cc thit b trung gian

Kt ni im-im (Point-to-point)

Kt ni trc tip

Ch c 2 thit b dng chung kt ni

Kt ni nhiu im (Multi-point)

2 thit b dng chung kt ni

2008

dce


Ch truyn

Simplex mode Khng dng rng ri v khng th gi 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

dce


Tn hiu Khi nim min thi gian

T/h lin tc

Thay i mn theo thi

gian

T/h ri rc

Thay i tng mc theo

thi gian

T/h tun hon

Mu lp li theo thi gian

C bn nht l sng sin

(Bin , tn s v pha)

T/h khng tun hon

Mu khng lp li theo thi

gian

2008

dce


Biu din tn hiu min tn s

Tn hiu thc t c

cu to bi nhiu thnh

phn c tn s khc nhau

Cc tn hiu thnh phn

l cc sng hnh sin

Tn s nh nht: tn s c

bn

Chu k ca tn hiu tng

hp bng chu k ca tn

s c bn

2008

dce


Biu din tn hiu min tn s

Tt c cc tn hiu (tng

t ln s) u c th c

phn tch thnh tng ca

nhiu sng sin (khai trin

Fourier)

=> C th biu din tn hiu

theo min tn s

Trc honh: cc tn s c

trong tn hiu

Trc tung: bin nh ca

tn hiu tng ng vi mi

tn s

2008

dce


Tn s, ph v bng thng

Ph Tm tn s cha trong tn hiu

Bng thng tuyt i rng ph (c o bng s

chnh lch tn s cao nht v thp nht)

Bng thng knh truyn cng ln, tc truyn cng cao

Bng thng hiu dng Gi tt l bng thng

Di tm tn s hp cha hu ht nng lng ca tn hiu

Thnh phn mt chiu Thnh phn c tn s bng 0

2008

dce


Tn hiu c thnh phn DC

2008

dce


Tn hiu s

Tn s f

Chu k T = ?

Thi gian truyn 1 bit Tbit = ?

Tc truyn d liu?

Bng thng???

2008

dce


Tng hp tn hiu s

2008

dce

Tng hp tn hiu s

Khi cng nhiu tn s kf bng bi s l ca

tn s c bn: tn hiu cng gn vi tn hiu

s

Dng biu din ca tn hiu s

2008

dce


Bng thng v tc truyn

Trng hp 1:

ng truyn c bng thng 4MHz

Tn hiu c thnh phn f, 3f, 5f vi f = 1MHz

Trng hp 2:


Tn hiu c thnh phn f, 3f, 5f, vi f = 2MHz

Trng hp 3


Tn hiu c thnh phn f, 3f vi f = 2MHz

Kt lun?

(chi ph, bng thng, mo tn hiu, tc d liu)

2008

dce


Truyn dn d liu tng t v s

D liu Cc thc th cha ng thng tin

D liu tng t: gi tr lin tc trong 1 thi khong

D liu s: gi tr ri rc theo thi gian

Tn hiu D liu c biu din dng tn hiu in hoc in t

Tn hiu tng t Thay i lin tc theo thi gian

Truyn trn nhiu mi trng: hu tuyn, quang, khng gian

Tn hiu s S dng 2 thnh phn DC

Truyn dn Trao i d liu bng cch lan truyn v x l tn hiu

2008

dce


Truyn dn d liu tng t v s

Thng thng Tn hiu tng t

truyn d liu tng t

Tn hiu s truyn d liu s

Trong mt s trng hp Tn hiu tng t

mang d liu s

Tn hiu s mang d liu tng t

2008

dce


Truyn dn tn hiu tng t v s

Truyn tn hiu tng t Khng quan tm ni dung d liu cha ng bn trong

Suy gim tn hiu theo khong cch

Dng amplifier khuch i tn hiu (k c nhiu)

Truyn tn hiu s Cn ch ni dung d liu cha ng bn trong

Khong cch truyn ngn

Dng repeater tng khong cch truyn

Nhiu khng b khuch i

2008

dce


Truyn dn s

u im

Cng ngh s

Cng ngh LSI/VLSI lm gim gi thnh

Ton vn d liu

Nhiu v suy gim tn hiu khng b tch ly bi cc repeater

Truyn khong cch xa hn trn cc ng truyn km cht lng

Hiu qu knh truyn

TDM > FDM

Bo mt

Cc k thut m ha bo mt d liu d p dng

Tch hp

D liu s v analog c x l tng t nhau

2008

dce


Suy gim tn hiu

T/h nhn c khc vi t/h truyn i

Analog suy gim cht lng t/h

Digital li trn bit

Nguyn nhn

Suy yu v mo do suy yu trn ng truyn

Mo do tr truyn

Nhiu

2008

dce


suy yu tn hiu trn ng truyn

Khi mt tn hiu lan truyn qua mt mi trng truyn, cng (bin ) ca tn hiu b suy gim theo khong cch

Ty thuc vo mi trng truyn dn i vi mi trng hu tuyn: l hm m theo khong cch

i vi mi trng v tuyn, suy gim cng t/h l mt hm phc tp theo khong cch v thnh phn kh quyn

Vn cn quan tm Tn hiu nhn phi mnh thit b nhn nhn bit c

Tn hiu phi c gi cao so vi nhiu t/h khng b li

Phi dng amplifier v repeater vi khong cch nht nh

Tn hiu khng c mnh qu mc gy qu ti, mo cho receiver

Vn i vi khong cch trong kt ni a im

Suy yu l mt hm tng theo tn s

Dng b khuch ai (khuch i tn s cao nhiu hn)

2008

dce


suy yu tn hiu trn ng truyn

o bng n v decibel (dB)

Cng t/h suy gim theo hm m

li/ hao ht ca cc tng ni tip c th

c tnh bng php ton n gin (+/-)

Cng thc

Attenuation = 10log10(P1/P2) (dB)

P1, P2: cng sut (watts)

Decibel (dB) l gi tr sai bit tng i

Cng sut suy gim hao ht l 3dB

Cng sut tng gp i li l 3dB

2008

dce


Tr lan truyn tn hiu

Mo tr lan truyn Ch xy ra trong mi trng truyn dn hu tuyn

Vn tc lan truyn thay i theo tn s Vn tc cao nht gn tn s trung tm

Cc thnh phn tn s khc nhau s n ch cc thi im 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 sng in t: v = 2 x 106 (m/s)

Round trip delay

Tx = N/R N : khi lng d liu truyn (bit)

R : tc truyn bit trn ng truyn.

2008

dce


Nhiu

T/h thm vo gia thit b pht v thit b thu

Nhiu nhit

Do dao ng nhit ca cc electron trong cht dn

Hm ca nhit

Phn tn ng nht trn ph tn s => Nhiu trng

Khng th loi b gii hn hiu sut ca h thng

Nhiu trong bng thng 1Hz ca bt k cht dn no

N0 = kT

N0: mt cng sut nhiu (watt/Hz)

k: hng s Boltzmann (= 1.38 x 10-23 J/K)

T: nhit (K)

Nhiu trong bng thng B (Hz) N = kTB

2008

dce


Nhiu Nhiu iu ch (intermodulation)

T/h nhiu c tn s l tng hoc hiu tn s ca cc t/h dng chung mi trng truyn

Do tnh phi tuyn ca thit b thu/pht

Nhiu xuyn knh (crosstalk) T/h t ng truyn ny nh hng sang cc ng

truyn khc

Cng ln (hoc nh hn) nhiu nhit

Nhiu xung Xung bt thng (spike)

e.g. nh hng in t bn ngoi

Thi khong ngn

Cng cao

nh hng nhiu n qu trnh trao i d liu s Xung 0.01s lm mt 50 bit d liu nu truyn tc 4800bps

2008

dce


c im C th truyn nhiu hn mt bit ng vi mi thay i ca

tn hiu trn ng truyn.

Tc truyn thng tin cc i b gii hn bi bng thng ca knh truyn

Cng thc Nyquist Nu tc truyn t/h l 2W th t/h vi cc tn s nh hn

v bng W l ; ngc li nu bng thng l W th tc t/h cao nht l 2W

C = 2W x log2M C : tc truyn t/h cc i (bps) khi knh truyn khng c

nhiu

W : bng thng ca knh truyn (Hz)

M : s mc thay i tn hiu trn ng truyn

Tc knh truyn (kh nng knh truyn)

2008

dce


Tc d liu Baud rate (baud)

Nghch o ca phn t d liu ngn nht (s ln thay i tn hiu ng truyn mi giy)

Tn hiu nh phn tc 20Hz: 20 baud (20 thay i mi giy)

Bit rate (bps hoc bit/s) c trng cho kh nng ca knh truyn

Tc truyn d liu cc i trong trng hp khng c nhiu

Bng baud rate trong trng hp tn hiu nh phn

Khi mi thay i ng truyn c biu din bng 2 hay nhiu bit, tc bit khc vi tc baud

Quan h gia Baud rate v Bit rate

R = Rs x log2M = Rs x m R : tc bit (bit/s)

Rs : tc baud (baud/s)

M : s mc thay i tn hiu trn ng truyn

m : s bit m ha cho mt tn hiu

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

2008

dce


Thut ng

2008

dce


Signal to Noise ratio SNRdB = 10 x log10( ) (dB)

S : cng sut tn hiu nhn

N: cng sut nhiu

Cng thc Shannon-Hartley

C = W x log2(1 + ) (bps)

C: tc truyn t/h cc i khi knh truyn c nhiu

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

R: tc bit ca d liu nh phn

Eb = STb = S/R

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

Tc sai bit l hm gim ca t s ny

T l tn hiu trn nhiu

N

S

N

S

BK TP.HCM

2008

dce

Chng 2

Truyn dn s liu Khi nim v thut ng

Truyn dn d liu tng t v d liu s

Suy hao ng truyn

Dung lng knh truyn

Mi trng truyn dn c nh hng

Truyn dn khng dy

Lan truyn khng dy

Truyn ng thng (line-of-sight)

2008

dce


Bc sng

Khong cch sng truyn c trong mt chu

k

Khong cch gia 2 im pha tng ng

trong 2 chu k lin tip

K hiu

Gi s vn tc t/h v

= vT

= v/f

c = 3*108 ms-1 (tc nh sng)

2008

dce


Mi trng truyn dn Hu tuyn (guided media wire)

Cp ng

Cp quang

V tuyn (unguided media wireless) V tinh

H thng sng radio: troposcatter, microwave, ...

c tnh v cht lng truyn d liu c xc nh bi mi trng v tn hiu i vi hu tuyn, mi trng nh hng ln hn

i vi v tuyn, bng thng to ra bi anten pht nh hng ln hn

Yu t nh hng trong vic thit k: tc d liu v khong cch Bng thng

Bng thng cao th tc d liu cao

Suy yu truyn dn Nhiu (nhiu nhit, nhiu iu ch, nhiu xuyn knh, nhiu xung)

S thit b nhn (receiver) Trong mi trng hu tuyn, cng nhiu thit b nhn, tn hiu truyn cng

mau suy gim

2008

dce


Cp ng: two-wire open line

Single pair

Flat ribon

Terminating Connector

2008

dce


Cp ng: twisted-pair

Insulating outer cover

Multi core

Insulating outer cover

Protective screen (shield)

Cch in trn mi dy Xon li vi nhau Thng c b li Chng nhiu crosstalk

2008

dce


Cp ng: twisted-pair

ng dng Mi trng truyn dn thng dng nht

Mng in thoi Gia cc thu bao v hp cp (subscriber loop)

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

Mng cc b (LAN) 10Mbps hoc 100Mbps

u nhc im R

D dng lp t, thao tc

Tc d liu thp

Tm ngn

2008

dce


Cp ng: twisted-pair

c tnh truyn dn

Analog

Cn b khuch i mi 5km ti 6km ( suy gim t/h:

~1dB/km, chun trong T: 6dB)

Digital

Dng tn hiu tng t hoc tn hiu s

Cn b lp (repeater) mi 2km hoc 3km

Khong cch gii hn

Bng thng gii hn (1MHz)

Tc d liu gii hn (100Mbps)

D b nhiu v tc ng ca mi trng ngoi

2008

dce


Cp ng: twisted-pair Khng v bc gip Unshielded Twisted Pair (UTP)

Dy T bnh thng

R nht

D lp t

D b nhiu trng in t bn ngoi

V bc gip Shielded Twisted Pair (STP) V gip bn gip gim nhiu v tc ng bn ngoi

t hn

Kh lp t (cng, nng)

2008

dce


Cp ng: twisted-pair

UTP Cat 3 Ln n 16MHz

c dng trong lin lc thoi hu ht cc vn phng

Chiu di xon (twist length): 7.5cm ti 10cm

UTP Cat 4 Ln n 20 MHz

UTP Cat 5 Ln n 100MHz

c dng ph bin hin nay trong cc vn phng

Chiu di xon: 0.6cm n 0.85cm

Thch hp cho tc truyn ln n 100 Mbps (LAN)

STP Cat 3: thch hp cho tc truyn

ln n 10 Mbps

2008

dce


Cp ng: twisted-pair cable

Cable standards

Tn Loi Mbps Thng c dng

Category 1 UTP 1 Modem

Category 2 UTP 4 Token Ring-4

Category 3 UTP 10 10Base-T Ethernet

Category 4 STP 16 Token Ring-16


Category 5 STP 100 100Base-T Ethernet

Category 5e UTP 100 1000Base-T Ethernet


Category 7 STP 600 1000Base-T Ethernet

2008

dce


Cp ng: coaxial

2008

dce

Cp ng: coaxial


2008

dce


Cp ng: coxial

ng dng Mi trng truyn linh hot nht

Cp truyn hnh

Truyn dn T khong cch xa FDM

C th mang 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 khuch 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

dce


Cp ng: c im chung

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 Kbps

n vi Mbps. V d: T1 ~ 1,5Mbps, E1 ~ 2Mbps,

telephone line: 64Kbps

2008

dce


Cp quang: cu trc

Single core

Multicore

Plastic

coating

Optical core Optical cladding

Single core

Multicore

Plastic

coating

Optical core Optical cladding

2008

dce


Cp quang: li ch v ng dng Li ch

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 repeater 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 s a 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

dce


Cp quang: c tnh truyn dn

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 qu hn

Tc d liu cao hn

Wavelength Division Multiplexing

2008

dce


Cp quang : ch truyn multimode: several paths/time delays

narrow: 1 wavelength no time delays

2008

dce


Cp quang : ch truyn

Step-index

multimode

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 liu

my tnh

ng in thoi

(khong cch trung bnh)

Vin thng ng

di

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

dce


Cp quang

2008

dce


Mi trng truyn dn hu tuyn

c tnh truyn dn im-im

2008

dce


V tuyn

Truyn v nhn thng qua anten

C hng

Chm nh hng (focused beam)

i hi s canh chnh hng

V hng

Tn hiu lan truyn theo mi hng

C th c nhn bi nhiu anten

Tm tn s

30MHz n 1GHz

V hng

radio

2GHz n 40GHz

Vi sng (microwave)

nh hng cao

im-im, V tinh

3 x 1011 n 2 x 1014 (Hz)

Hng ngoi

Cc b

Khc phc nhng kh khn v a l khi trin khai h thng

T l bit li trn ng truyn (BER) thay i ty theo h thng c trin khai. V d: BER of satellite ~ 10-10

Tc truyn thng tin t c thay i, t vi Mbps n hng trm Mbps

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

Chi ph trin khai h thng ban u rt cao

2008

dce


V tuyn: cc bng tn truyn thng

2008

dce


V tuyn: sng viba mt t Cho parabol (thng bn knh 3m)

Chm sng nh hng theo ng ngm (line of sight)

suy gim t/h

d: khong cch

: bc sng

suy gim t l thun bnh phng khong cch cn

amplifier/repeater mi 10-100km

suy gim thay i theo mi trng (cng tng khi c ma)

ng dng:

Thay th cho cp ng trc trong vin thng khong cch xa (cn t b

amp/repeater, nhng phi nm trn ng thng)

Truyn im - im khong cch ngn

in thoi di ng

Tn s cng cao th tc d liu cng cao

dBL d 24log10

2008

dce


V tuyn: sng viba mt t

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

2 7 12

6 30 90

11 40 90

18 220 274

Hiu sut sng viba s

2008

dce


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

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

Cn qu o a tnh Cao 35.863 km

ng dng Truyn hnh

in thoi ng di

Mng ring (VSAT)

c tnh Thng trong khong tn s 1-10 GHz

< 1 GHz: qu nhiu nhiu t mi trng t nhin

>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 s cao hn i hi tn hiu phi mnh khng b suy gim

Tr 240-300ms, ng ch trong vin thng

2008

dce


V tuyn: v tinh

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

VSAT : very small aperture terminal

Eq

uato

rial O

rbit

22,3

00 m

iles

2008

dce


V tuyn: sng radio

V hng, 30MHz 1GHz Antena khng cn c hnh a v khng cn chnh hng

Sng FM, truyn hnh UHF v VHF

t b suy gim do ma, xuyn qua kh quyn

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

dce


V tuyn: sng hng ngoi

Truyn theo ng thng (hoc phn x)

Cn bi cc bc tng

B iu khin TV t xa, cng iu khin bng

hng ngoi (IRD port)

2008

dce


Mi trng truyn dn

2008

dce


Lan truyn khng dy

Lan truyn sng mt t (ground wave)

Tn hiu i theo b mt cong ca tri t

Do to ra dng in b mt tri t

Do s nhiu x khi qua cc chng ngi vt

Tn s ln n 2MHz

AM radio

2008

dce


Lan truyn khng dy

Sng khng gian (sky wave)

Radio nghip d, BBC world, VoA

Tn hiu b tng in ly phn x li mt t

(thc t l b khc x)

2008

dce


Lan truyn khng dy

Truyn theo ng ngm

Tn s trn 30Mhz

C th truyn xa hn ng ngm nh sng v b

hiu ng khc x

2008

dce


Truyn theo ng ngm

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

dce


Truyn theo ng ngm

Suy gim tn hiu trong khng gian (free

space loss)

Tn hiu b phn tn theo khong cch

i vi cng 1 anten, suy gim cng nhiu i vi

tn s thp (bc sng di)

dBdfLc

fd56.147)log(20)log(20log10

24

2424c

fdd

r

t

P

P

2008

dce


Truyn theo ng ngm

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

2008

dce


Multipath

2008

dce

Bi tp

3.14, 15, 16, 17, 19, 20, 21

4.2, 7, 13, 16


BKTP.HCM

2008

dce

Chng 3

K thut m ha tn hiu

D liu s, tn hiu s

D liu s, tn hiu tng t

D liu tng t, tn hiu s

D liu tng t, tn hiu tng t

2008

dce


Tn hiu analog

Ba c im chnh ca tn hiu 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 nhau ca nhiu tn hiu

2008

dce


Tn s ca tn hiu analog

Tc thay i ca tn hiu

trong mt giy, n v Hz

hay s chu k trong mt

giy (cycles per second)

T/h 30Hz thay i 30 ln trong

mt giy

Mt chu k l s di chuyn

sng ca tn hiu t im

ngun bt u cho n khi

quay tr v li im ngun

.

2008

dce


Pha ca tn hiu analog

Tc thay i quan h ca tn hiu i vi thi gian, c m t theo (degree)

S dch pha xy ra khi chu k ca tn hiu cha kt thc, v mt chu k mi ca tn hiu bt u trc khi chu k trc cha hon tt Tai ngi khng cm nhn

c 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

dce


Tn hiu digital

Tn hiu s bao gm ch hai trng thi, c din t

vi hai trng thi ON hay OFF hoc l 0 hay 1

Tn hiu s yu cu kh nng bng thng ln hn tn

hiu analog.

2008

dce


Tn hiu digital

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

Mt tn hiu s l mt t hp ca cc tn hiu khc. c bit, tn

hiu s c th c biu din nh sau

Signal = f + f3 + f5 +f7 +f9 +f11 +f13 ....f

Do mt tn hiu s gm 1 tn s c bn (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 s c bn f, tn s 3f v tn s 5f 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

dce


Tn hiu digital

Truyn 1 tn hiu s nh phn tc 2400bps trn knh thoi c bng thng 3.1kHz Tn s c bn: 1200Hz (thng thng bng tc bit)

Ch c tn s c bn i qua m khng b thay i

2008

dce


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

Gi bnh thng hoc m ha vo phn ph khc

Analog data/Digital Signal M ha dng b codec 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, x l 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

Analog and digital

transmission

Analog

data

Analog

signal

Digital

signal

Digital

data

Analog

signal

Digital

signal

2008

dce


D liu s, tn hiu sAnalog and digital

transmission

Analog

data

Analog

signal

Digital

signal

Digital

data

Analog

signal

Digital

signal

Tn hiu s Xung in p ri rc, khng lin tc

Mi xung l mt phn t tn hiu

D liu nh phn c m ha thnh cc phn t tn hiu

2008

dce

Thut ng


Baseband signal

Carrier signal

Bandpass

Lowpass

Highpass

2008

dce


Thut ng

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

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) Thi gian thit b pht dng truyn 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

dce


Din gii tn hiu

Cn bit

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

T s SNR: cng ln th BER cng gim

Tc d liu (bps): cng tng th BER cng tng

Bng thng: cng ln th tc d liu cng tng

2008

dce


Nonreturn to Zero (NRZ) Nonreturn to Zero-Level (NRZ-L)

2 mc in p khc nhau cho bit 1 v bit 0

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

in p khng thay i trong thi khong bit Khng c transition (no return to 0V level)

NRZ: bit 0 khng c in p; bit 1 in p dng

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 s thay 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

dce


Nonreturn to Zero (NRZ)

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

bng mc t/h)

Nhn bit s thay i d dng hn so vi nhn bit mc

Trong cc h thng truyn dn phc tp, cm gic cc tnh 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 kh nng ng b

Dng trong vic ghi bng t, USB, CD

t dng trong vic truyn t/h

2008

dce


Multilevel Binary

Dng nhiu hn 2 mc tn hiu

Bipolar-AMI (Alternate Mark Inversion) 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

dce


Multilevel Binary

Trade Off

Khng hiu qu bng NRZ

Mi phn t t/h ch biu din 1 bit

H thng 3 mc c th biu din log23 = 1.58 bit

B thu phi c kh nng phn bit 3 mc (+A, -A, 0)

Cn thm khong 3dB cng sut t c cng xc

sut bit li ca binary code

2008

dce


Biphase: Manchester

Manchester Thay i gia thi khong bit

Thay i c dng nh t/h ng b (clock) v d liu

LH biu din 1

HL biu din 0

Dng trong IEEE 802.3 (ethernet), RFID

2008

dce


Biphase: Differential Manchester

Differential Manchester Thay i gia thi khong bit ch dng cho ng b

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

dce


Biphase

u v nhc im Nhc

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 s thay i gia

thi khong bit (self clocking)


Pht hin li Khi thiu s thay i mong i

2008

dce


Bi tp

2008

dce


Scrambling

Dng k thut scrambling thay th cc chui to ra hng s in p

Chui thay th Phi to ra s thay 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 nh chui ban u


Khng to ra chui di cc t/h mc 0

Khng gim tc d liu

C kh nng pht hin li

2008

dce


B8ZS v HDB3

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

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 nh 8 s 0

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

Chui 4 s 0 c thay th bng chui c 1 hoc 2 xung theo 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

dce


B8ZS v HDB3

2008

dce


Bi tp

2008

dce

Mua bus 1 thc hnh

2008

dce


D liu s, tn hiu tng t

ng dng Dng truyn d liu s trn

mng in thoi cng cng 300Hz 3400Hz

Thit b MODEM (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

Analog and digital

transmission

Analog

data

Analog

signal

Digital

signal

Digital

data

Analog

signal

Digital

signal

2008

dce


iu bin (ASK)

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

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 vo chun giao tip ang c s dng

K thut c dng trong cp quang LED: sng, khng sng

ILD: 2 mc sng khc nhau

00

1)2cos()(

binary

binarytfAts

cc

2008

dce


iu bin (ASK)

2008

dce


iu tn (FSK)

S dng hai tn s sng mang: tn s f1 tng ng mc 1,

tn s f2 tng ng mc 0.

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 s cao (3-30MHz) truyn trn sng radio

hoc cp ng trc

0)2cos(

1)2cos()(

2

1

binarytfA

binarytfAts

c

c

2008

dce


iu tn (FSK)

2008

dce


iu pha (PSK)

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

PSK sai phn (differential PSK) thay i pha tng i so vi sng trc (thay v so vi sng tham chiu c nh)

Cho php m ha nhiu bit trn mi thay i tn hiu sng mang (Phase

Amplitude Modulation)

Phng php ny thng c dng trong truyn d liu tc

2400bps (2 bits per phase change - CCITT V.26) hoc 4800bps (3 bits

encoding per phase change - CCITT V.27) hoc 9600bps (4 bits encoding

per phase/amplitude change)

Tng qut cho m ha NRZ-L

0)2cos(

1)2cos()(

binarytfA

binarytfAts

c

c

elements signaldifferent ofnumber :L

element signalper bits ofnumber :

(bps) rate data :R

(bauds) rate modulation :D

Llog

RRD

2 ll

2008

dce


iu pha (PSK)

2008

dce


iu pha (PSK)

Quadrature PSK (QPSK)

Multilevel PSK H thng 64 v 256 trng thi

Ci thin tc d liu vi bng thng khng i

Tng kh nng tim n li

11)2702cos(

10)1802cos(

01)902cos(

00)02cos(

)(

tfA

tfA

tfA

tfA

ts

c

c

c

c

2008

dce


Hiu sut

Bng thng

Bng thng ASK v PSK lin quan trc tip vi tc bit

BT = (1+r)R

Bng thng FSK c quan h vi tc d liu i vi cc

tn s thp, c quan h vi sai lch ca cc tn s iu

ch i vi tn s cao

BT = 2F + (1+r)R

Tn hiu nhiu mc

BT = (1+r)R/l = (1+r)R/log2M

Trong trng hp c li, tc li ca PSK v

QPSK cao hn khong 3dB so vi ASK v FSK

2008

dce


Quadrature 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

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 nh phn ban u

2008

dce

Quadrature Amplitude Modulation (QAM)

2008

dce


D liu tng t, tn hiu s ng dng

Dng truyn d liu tng t trn mng truyn d liu s

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 thut iu ch xung m: Pulse Code Modulation

(PCM)

iu ch Delta: Delta Modulation (DM)

Analog Digital

DMPCM

Analog and digital

transmission

Analog

data

Analog

signal

Digital

signal

Digital

data

Analog

signal

Digital

signal

2008

dce


iu ch xung m (PCM) L thuyt ly mu

Nu 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

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

f(t) c th c ti to, dng b lc thng thp

Cng 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

2008

dce


iu ch xung m (PCM)

2008

dce


iu ch xung m (PCM)

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 s tng SNR 6dB

2008

dce


iu ch xung m (PCM)

2008

dce


Non-Linear encoding

Mc lng t khng u

Gim mo tn hiu

Companding (compressing-expanding)

2008

dce


Companding

2008

dce


iu ch Delta (DM)

Tn hiu tng t c xp x bi hm cu thang

(staircase)

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

dce


iu ch Delta (DM)

2008

dce


D liu tng t, tn hiu tng t ng dng

Dng iu ch d liu tng t: thay i tn s truyn (tn s cao hn truyn dn tt hn)

Dng cho FDM

K thut iu ch bin: Amplitude

Modulation (AM)

iu ch gc (Angle Modulation) iu ch tn s: Frequency

Modulation (FM)

iu ch pha: Phase Modulation (PM)

Analog Analog

AngleAM

PMFM

Analog and digital

transmission

Analog

data

Analog

signal

Digital

signal

Digital

data

Analog

signal

Digital

signal

2008

dce


iu ch bin (AM)

Bin ca sng mang c thay i bi bin ca tn hiu c truyn is(t) = [1+nax(t)]cos(2fct)

To ra t/h 2 bn (DSBTC), trong ch cn c mt bn

na1 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 s iu ch, t s bin 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 qu nng lng

2008

dce


iu ch bin (AM)

M(f)

fB

M(f)

ffc B fc + Bfc

Upper sideband

Lower sideband

Discrete carrierterm

2008

dce

iu ch bin (AM)

2008

dce

iu ch bin (AM)

na < 1 (V trong Matlab)

2008

dce

iu ch bin (AM)

na > 1

2008

dce

iu ch bin (AM)

na < 1 (V trong Matlab

2008

dce


iu ch gc

s(t) = Accos[2fct + (t)]

Phng php iu tn s (FM) o hm ca pha (t) t l thun vi tn hiu c truyn i

(t) = nfm(t)

u im Kh b nh hng ca nhiu

S dng hiu qu nng 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 phng php iu bin

)('2

1)( tftf ci

2008

dce


iu ch gc

2008

dce


iu ch gc

Phng php iu ch pha (PM) (t) = npm(t)

Tn hiu truyn i khng nh hng n thnh phn bin v tn s m ch lm thay i pha ca sng mang

Ph tn s ca tn hiu c iu ch theo phng php iu pha tng t nh phng php iu tn phng php iu pha cng c cc c im tng t phng 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 c nh, ch c pha thay i nn ch cn thit k b lc tn s ch cho mt tn s duy nht thay v nhiu tn s nh trong phng php iu tn gim chi ph thit k v hin thc mch

Trong trng hp tn hiu iu ch ch nhn mt s gi tr (nh tn hiu s), mch iu ch v gii iu ch hin thc theo phng php iu pha c n gin rt nhiu

2008

dce


Hiu sut

Bng thng

AM

BT = 2B

FM&PM

BT = 2(+1)B

FM&PM cn bng thng ln hn so vi AM

FMB

An

B

F

PMAn

mf

mp

2

2008

dce

Bi tp

5.4, 5, 6, 10, 12, 15, 16, 20, 23, 24, 25, 26


BKTP.HCM

2008

dce

Chng 4

Cc k thut truyn d liu s

Truyn bt ng b v truyn ng b

Cc loi li

Pht hin li

Sa li

Cu hnh ng truyn

Giao tip

2008

dce


Truyn d liu song song

Mi bit dng mt ng truyn ring, truyn ng thi.

Cc ng truyn khc

Clock signal: thng bo cho bn nhn bit khi no c d liu

GND: so snh in p

Direction: hng ca ng truyn

Hand-shaking: tn hiu bt tay (sn sng nhn)

VD: ISA, ATA, PCI

2008

dce


Truyn d liu tun t

Tt c cc bit u c truyn trn cng mt ng truyn

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 truyn i)

Vn nh thi (timing) i hi phi c c ch ng b gia bn truyn v bn nhn

VD: RS232, SPI, I2C

2 cch gii quyt

Bt ng b: mi k t c ng b bi start v stop bit

ng b: mi khi k t c ng b dng c

2008

dce


Truyn 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 gi ng b trong mt k t

Ti ng b cho mi k t mi

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

dce


Truyn bt ng b

LSB

2008

dce


Truyn ng b

Truyn khng cn start/stop

Phi c tn hiu ng b

ng b bit (bit synchronization) 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

dce


Truyn ng b

ng b frame

Mi 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

sn

Mt chui cc k t SYN (16h trong bng m ASCII)

Mu bit 11111110

Frame: d liu + preamble + postamble + thng tin iu khin

Hiu qu hn so vi truyn bt ng b (ph tn thp hn cho cc

bit iu khin)

HDLC: 48 bit iu khin cho mi block 1000 k t (8000 bit)

2008

dce


Cc loi li xy ra trn ng truyn Mi trng truyn dn b nhiu (in, t, ) d liu nhn c li (cc bit

b thay 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 v li nm u sa (c kh nng sa li)

Feedback (backward) error control: thng tin sa sai c thm vo cc k t hoc cc frame truyn i ch pht hin khi no c li (khng c kh nng sa li). C ch 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

dce


C ch pht hin li

2008

dce


Pht hin li bng bit parity

1 bit parity c thm vo 1 khi d liu cn truyn i

Bit parity Parity chn: tng s bit 1

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

Parity 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 0e 0 1 0 1 0 1 1 1

2008

dce


Parity

c im

Ch d c li sai mt

s l bit, khng d c

li sai mt s chn bit

Khng sa c li

t c dng trong truyn

d liu i xa, c bit

tc cao

2008

dce


Block Sum Check

Block Sum Check (BSC): s dng parity hng v ct

Khng sa c sai, ch sa c sai khi s bit sai trong d

liu l mt

D tm c tt c cc li sai mt s l bit v hu ht cc li

sai mt s chn bit.

Khng d c li sai mt s chn bit xy ra ng thi trn

c hng v ct.

D a t a Start D a t a Parity

(even)

Stop

B 1 B 2 B 3 B 4 B 5 B 6 B 7

H 1 0 0 0 1 0 0 1 0 0

E 1 1 0 1 0 0 0 1 0 0

L 1 0 0 1 1 0 0 1 1 0

L 1 0 0 1 1 0 0 1 1 0

O 1 1 1 1 1 0 0 1 1 0

BCC

(odd)

1 1 0 1 1 1 1 0 0 0

2008

dce


Cyclic Redundancy Check (CRC)

Nguyn l k-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 trc

Bn thu chia frame nhn c cho cng 1 s v nu khng c phn d th c kh nng khng c li

S hc modulo 2 Exlusive-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 1

1010

0101+

1111

2008

dce


CRC 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)

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

Gi s

Suy ra nu ly th T chia ht P

Kim tra li?

P

RQ

P

Dn2

FDn2 T

R F

2008

dce


CRC dng s hc

V d:

D = 1010001101 (10 bit)

P = 110101 (6 bit)

F =? (? bit)

n = 6-1 = 5 bit, k = 10 bit, n+k = 15 bit

p s: F = 01110

D liu T = 101000110101110

2008

dce


CRC 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

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 kh nng xy ra

2008

dce


CRC dng a thc

Cch khc xc nh FCS: a thcD=110011 D(x) = x5+x4+x+1

P=11001 P(x) = x4+x3+1

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

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

dce


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)

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

Hu ht cc li chm ln hn

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

2008

dce


Cyclic Redundancy Check

4 a thc sinh c s dng rng ri CRC-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 16-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

dce


CRC dng mch sD=1010001101P=110101

1010001101

x2

1

x4

x5

C4

C3

+

C2

C1

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

Step 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 1

Step 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

dce


Sa li

Cch sa li thng thng l yu cu truyn li khi

d liu b li

Khng thch hp cho cc ng dng trao i d liu

khng dy

Xc sut li cao, dn n vic phi truyn li nhiu

Thi gian tr truyn ln hn nhiu thi gian truyn 1 khi

d liu

C ch 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

dce


C ch sa li

2008

dce


C ch sa li

Thm mt s m d tha vo d liu truyn i

B thu c kh nng suy lun ra d liu gc ban u

khi c li xy ra

V d: m sa li block

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 t m trong khng xut hin k bit d liu gc

Lm gim tc d liu hiu dng

Code rate: k/(n+k)

2008

dce

C ch sa li

VD:

Data block/Codeword

00: 00000

01: 00111

10: 11001

11: 11110

D liu nhn c 00100 -> ? Sa sai c?

(Khong cch Hamming)

D liu khng sa sai c?

2008

dce


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 s n gin nh NRZ-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 i

Cn mt chun giao tip r rng

c tnh C kh

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

dce


Giao tip

2008

dce


Chun V.24/EIA-232-F Chun giao tip c s dng rng ri, quy nh bi

ITU-T

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

c tnh in

EIA-232-F (USA) RS-232

c tnh c kh: 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

dce


c tnh c kh

DB-25 female

(DTE)

2008

dce


c tnh in

Dng tn hiu s

Cc gi tr c hiu l d liu hoc iu khin ty thuc vo mch

NRZ-L >+3V 0

+3V on

2008

dce


c tnh chc nngV.24 EIA-232 Name Direction to Function

Data signals

103 BA Transmitted data DCE Transmitted by DTE

104 BB Received data DTE Received by DTE

Control signals

105 CA Request to send DCE DTE wishes to transmit

106 CB Clear to send DTE DCE is ready to receive, response to RTS

107 CC DCE ready DTE DCE is ready to operate

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 within

appropriate 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

dce


Local/Remote loopback testing

2008

dce


Th tc

V d modem ring bt ng b, kt ni 2 thit b khong cch ngn

Ch cn mt s tn hiu Signal 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

dce


Modem ring bt ng b

DCE ready

Request to send

Clear to send

D liu

Received line

signal detector

D liu

2008

dce


Khong cch di

Hai modem ni vi nhau qua mng in thoi

Cn thm 2 tn hiu

DTE ready (108.2)

Ring indicator (125)

Tng t nh vic s dng in thoi

2008

dce


Hot ng quay s (1)

2008

dce


Hot ng quay s (2)

2008

dce


Hot ng quay s (3)

2008

dce


Null modem

2008

dce


ISDN interface

Chun EIA-232-F cn qu nhiu chn trong giao tip

Chun X.21 a ra chun giao tip 15 chn -> 8 chn -> ISDN

ISDN (Intergrated Services Digital Network): thay th mng li in thoi v truyn t/h tng t bng h thng truyn t/h s

Giao tip gia TE (terminal equipment tng t DTE) v NT (network-terminating equipment)

ISO 8877 giao tip thng qua 8 chn

Transmit/receive truyn d liu ln iu khin

2008

dce


ISDN interface

2008

dce


ISDN interface

Tn hiu c truyn trn cp xon

Balanced transmission

Gi tr nh phn ph thuc vo s sai khc mc

in th gia 2 dy dn

t nhiu: nhiu nh nhau trn 2 dy

M ha ph thuc tc d liu

Basic rate (192 kb/s): pseudotenary (750mV)

Primary rate

1.544 Mb/s: B8ZS

2.048 Mb/s: HDB3

BKTP.HCM

2008

dce

Chng 5

iu khin lp lin kt d liu

iu khin dng d liu

iu khin li

Giao thc iu khin lin kt d liu cp

cao HDLC

2008

dce


Vn khi trao i d liu Mt s vn khi hai thit b kt ni trc tip truyn

nhn d liu

ng b khung

D liu c gi di dng cc frame

Thi im bt u v kt thc mt frame

iu khin tc truyn d liu

X l li gp phi trn ng truyn

nh v a ch trong cu hnh multipoint

Phn bit d liu v thng tin iu khin

D liu v thng tin iu khin truyn chung

Qun l kt ni

Thit lp, duy tr, ngt kt ni

Lp vt l khng th thc hin cc chc nng trn

2008

dce


iu khin dng d liu

Bn nhn thng c b m nhn d liu

Khi d liu n, bn nhn thng thc hin mt s x l trc khi gi ln lp cao hn

iu khin dng nhm m bo bn pht khng gi d liu qu nhanh

Ngn nga vic trn b m

2008

dce


M hnh truyn khung

Dng phn tch qu trnh truyn nhn d liu thnh tng khung (frame)

2008

dce


Khi nim

Thi gian truyn (tframe): thi gian cn thit gi tt c cc bit ca frame d liu ln ng truyn

Thi gian lan truyn (tprop): thi gian cn thit d liu i t ngun n ch

2008

dce


iu kin gi nh

Tt c frame u n ch, khng b mt

Khng c frame li

Cc frame n ng th t

2008

dce


Idle RQ (StopandWait) C ch hot ng

Ngun pht d liu (di dng cc frame)

ch nhn d liu v tr li bng ACK (acknowledgement)

Ngun phi i ACK trc khi pht tip d liu

ch c th dng qu trnh bng cch khng gi ACK

c im

Phng php n gin nht

c dng ch yu trong cc ng dng character-oriented.(byte-oriented)

S dng knh truyn hot ng trong ch half-duplex

2008

dce


Thi gian tng cng TD= n(2tprop + tframe)

Hiu sut ng truyn

Idle RQ Hiu sut

2008

dce


Vn kch thc frame

Phng php Stop-and-wait s dng ng truyn hiu qu nu kch thc (chiu di) frame ln

Nhng thc t d liu ln c chia thnh cc frame c kch thc nh

Kch thc b m c gii hn

Frame kch thc nh kh xy ra li

Li c pht hin sm

Khi c li, ch cn truyn li frame nh

Ngn nga tnh trng 1 trm lm vic chim ng truyn lu

2008

dce


Sliding windows

Cho php nhiu frame c th truyn ng thi

Bn thu c b m vi kch thc W frame (c th nhn W frame)

Bn pht c th truyn ti a W frame m khng cn i ACK

Cc frame c nh s th t

ACK c cha s th t ca frame k tip c th truyn

S th t thng c gii hn bi k bit trong frame

nh s quay vng modulo 2k

2008

dce


Sliding windows

2008

dce


Sliding windows V d

2008

dce


Sliding windows Ci tin

ch c th gi ACK khng cho php Ngun gi tip d liu (Receive Not Ready)

Trong trng hp ny, sau

Documents

Kỹ Thuật Truyền Số Liệu - dulieu.tailieuhoctap.vndulieu.tailieuhoctap.vn/books/cong-nghe-thong-tin/the-loai-khac/... · • Giảng viên –Nguyễn Hoà ... • [1] “Tập