Bai Giang Truyen Thong Multimedia

8/2/2019 Bai Giang Truyen Thong Multimedia

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HC VIN CNG NGH BU CHNH VIN THNG---------------------------------------------------

BI GING:

TRUYN THNG A PHNG TIN(Dng cho cc sinh vin ngnhin-in t)

BIN SON: TS. NGUYN QU S

H NI, 06/2010


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Mc lc

THUT NG VA CH VI T T T ............................................................................................ vLI M U ................................................................................................................................ 1CHNG I TRUYN THNG APHNG TIN .............................................................. 31.1. Gii thiu............................................................................................................................... 31.2. S pht trin v hi t ......................................................................................................... 4

1.2.1. S hi t ca vin thng v tin hc ......................................................................... 51.2.2. Kin trc ca cc dch v ni mng ........................................................................ 61.2.3. Lin kt .................................................................................................................... 71.2.4. S tnh ton c th truyn ti c.......................................................................... 8

1.3. Khung c s cng ngh ........................................................................................................ 81.3.1. Cccng ngha phng tin ................................................................................ 91.3.2. Kt ni mang a phng tin ................................................................................ 131.3.3. Hi ngh a phng tin ........................................................................................ 141.3.4. Multicasting ........................................................................................................... 161.3.5. Cc cng ngh cho ni dung in t (e-Content) .................................................. 17

1.4. Khung c s tiu chu n ho a .............................................................................................. 191.4.1. Cc tiu chun m thanh/hnh nh s v cng nghip a phng tin .................. 201.4.2. Cc tiu chun ca ITU-T cho cac hthng truyn thng nghe nhn . .................. 211.4.3. Cc tiu chun m ha hnh nh ............................................................................ 221.4.4. Cc tiu chun m ha m thanh ........................................................................... 241.4.5. Cc tiu chun ng b v ghp a phng tin ................................................... 241.4.6. Cc tiu chun MPEG trong truyn thng a phng tin ................................... 25

1.5. Kt lun ............................................................................................................................... 29CHNG II KHUNG C S TIU CHU N HO A MULTIMEDIA............................. 302.1. Gi i thiu............................................................................................................................. 302.2. Cc hot ng tiu chun ha. .......................................................................................... 31

2.2.1. Nhngl do tm kim m t tiu chun. .............................................................. 322.2.2. Nhng giao din c tiu chun ha. .................................................................. 322.2.3. Thi gian tiu chun ha................................................................................... 342.2.4. S chun ha s din ra nh th no ?................................................................... 352.2.5.

Ai s qun l cc hot ng chun ha?................................................................ 36

2.2.6. S chun ha c s dng nhng ni no ? ........................................................ 362.2.7. Chu trnh cng ngh v sn phm hoc dch v s c chun ha. .................... 37

2.3. Cc tiu chun xy dng mt c s h tng thng tin ton cu mi ....................... 382.3.1. Khi nim .............................................................................................................. 402.3.2. Mc ch thc hin ................................................................................................ 412.3.3. M hnh ch c nng ................................................................................................ 442.3.4. M hnh thc thi .................................................................................................... 452.3.5. Cch tip cn theo ki ch ban (Scenarios Approach ) .............................................. 472.3.6. Cc n lc tiu chun ha...................................................................................... 482.3.7. Chng tr

nh nghin cu cu

a cc nhm tiu chun hoa ca ITU -T cho GII ........ 50

2.3.8. Cc nh hng cho tng lai ............................................................................... 532.4. Tiu chun ha cc qu trnh truyn thng a phng tin.......................................... 53


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2.4.1. Chin lc ca ITU-T ........................................................................................... 532.4.2. nh hng ca ISO/IEC JTC1 trong nhng tiu chun a phng tin ............. 552.4.3. Cc tiu chun IETF .............................................................................................. 602.4.4. D n chun ha ca ETSI i vi cc ng dng, phn Middleware v mng .... 612.4.5. Cc hot ng lin quan t i GII ............................................................................ 63

2.5. ISO/IEC MPEG-21 ............................................................................................................ 632.5.1. M hnh ngi s dng (User Model)................................................................... 652.5.2. Cc phn t s (Digital Items)............................................................................... 652.5.3. K hoch thc hin (Work Plan) ........................................................................... 662.5.4. Cc kch bn s dng MPEG-21 ........................................................................... 672.5.5. Cc yu cu cu a ng i s dung ............................................................................. 68

2.6. Cc tiu chun internet v a phng tin cu a IETF..................................................... 702.7. Din n v lin doanh cng nghip ................................................................................. 712.8. Kt lun ............................................................................................................................... 85CHNG III L P NG DUNG ............................................................................................... 86

3.1. Cc ng dng ca H.323 cho truyn thng a phng tin........................................... 86

3.1.1. Cc giao thc s dng trong H.323 ....................................................................... 863.1.2. Cc thnh phn ca H.323 ..................................................................................... 873.1.3. Qu trnh kt ni .................................................................................................... 87

3.2. ng dng H.264 v MPEG-4 trong nen truyn hnh s ................................................. 883.2.1. ngdng MPEG-4 ................................................................................................ 883.2.2. ng dng H.264 .................................................................................................... 91

3.3. Cc ng dng MPEG-2 trong truyn ta i IPTV ............................................................... 973.4. Cc ng dng qung b s ................................................................................................ 99

3.4.1. H i tu vin thng va quang ba ............................................................................... 993.4.2. Dch v pht thanh/truyn hnh s -DAB/DMB ................................................... 1003.4.3. Cc dch v tng tc trong truyn hnh s ......................................................... 106

3.5. Kt lun ............................................................................................................................. 107CHNG IV L P MIDDLEWARE ....................................................................................... 1084.1. Gi i thiu........................................................................................................................... 1084.2. Middleware cho a phng tin ..................................................................................... 1094.3. M ha thng tin .............................................................................................................. 109

4.3.1. Biu din n i dung thng tin ............................................................................... 1104.3.2. Cc cng ngh nn ct li ................................................................................... 1124.3.3. Cc kin trc v cng ngh chuyn m ............................................................... 115

4.4. To dng thng tin ........................................................................................................... 1194.4.1. To dng video qua Internet ................................................................................ 1204.4.2. Nh ng thach th c truyn ta i video th i gian thc qua Internet ...................... 1304.4.3. Kin tru c end-to-end cho truyn ta i video MPEG-4 qua Internet ....................... 1314.4.4. Truy c p bng rng .............................................................................................. 1324.4.5. C s cu a cht lng di ch vu .............................................................................. 133

4.5. An ninh cu a ca c hth ng a phng tin...................................................................... 1334.5.1. Hthng truy c p co iu kin (CA) ................................................................... 1334.5.2. Hthng quan ly ban quyn s DRM-K thut Watermarking .......................... 136


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4.6. Kt lun ............................................................................................................................. 143CHNG V L P MANG ........................................................................................................ 1445.1. Gi i thiu........................................................................................................................... 1445.2. Cc chc nng mng ........................................................................................................ 145

5.2.1. M hnh tham chiu OSI ..................................................................................... 1455.2.2. Bo hiu trong cc mng truyn thng ................................................................ 1495.2.3. Th tc nh tuyn cho truyn thng a phng tin .......................................... 150

5.3. Phn tch lu lng mng ............................................................................................... 1505.4. Ch t lng di ch vu trong ca c hthng a phng tin n i mang .............................. 151

5.4.1. nh ngha QoS ................................................................................................... 1525.4.2. Cc m hnh QoS................................................................................................. 1525.4.3. Cc tham s cht lng dch v .......................................................................... 156

5.5. Mng vin thng th h sau NGN ................................................................................... 1585.5.1.

M hnh kin trc chc nng NGN ..................................................................... 158

5.5.2. M hnh phn lp NGN ....................................................................................... 1625.5.3. Phn h a phng tin IP (IMS) ........................................................................ 1645.5.4. Xu hng pht trin NGN ................................................................................... 168

5.6. Cc mng truy cp bng rng ......................................................................................... 1695.6.1. Cng ngh truy nhp xDSL ................................................................................. 1695.6.2. Mng cp quang .................................................................................................. 1855.6.3. Cc mng v tuyn bng rng -Wimax ................................................................ 189

5.7. Mng phn phi ni dung (CDN) ................................................................................... 1915.7.1. Mng s dng Caching Proxies ........................................................................... 1925.7.2. Mng s dng Server Farms................................................................................ 1945.7.3. Mng phn phi ni dung .................................................................................... 1955.7.4. Hthng i nh tuyn yu cu ............................................................................... 198

5.8. Kt lun ............................................................................................................................. 199TI LIU THAM KHO......................................................................................................... 200


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THUT NG VA CH VI T T T

Ch vi t

t tT ting Anh Ngha ting Vit

AAA Authentication, Authorization and

AccoutingXc thc, Cp php, K ton

AES Advanced Encryption Standard Tiu chun mt m ha tin tin

AK Authorization Key Kha cp php

ASI Asynchronous Serial Interface Giao din s ni tip bt ng b

ATSCAdvanced Television Systems

Committee

y ban cc h thng truyn hnh

tin tin

AVC Advanced Video Coding M ha Video tin tin

CA Conditional Access Truy cp c iu kin

CBC Cipher Block Chaining Chui khi mt m

CEK Content Encryption Key Kha m ha ni dung

CI Common Interface Giao din chung

CMLA Content Management License

Administrator

Qun tr giy php qun l ni

dung

COFDM Coded OFDMGhp knh phn chia theo tn s

trc giao c m ha sa li

CRL Certificate Revocation List Danh sch hy b chng nhnCSA Common Scrambling Algorithm Thut ton trn chung

DAB Digital Audio Broadcasting Pht thanh qung b k thut s

DCF DRM Content Format Khun dng ni dung DRM

DEA Data Encryption Algorithm Thut ton m ha d liu

DES Data Encryption Standard Tiu chun mt m ha d liu

DLDRM Download and DRM Ti v v DRM

DMB Digital Multimedia Broadcasting Pht qung b a phng tin s

DRM Digital Rights Management Qun l bn quyn k thut s

DTH Direct To Home Ti tn nh

DTTBDigital Terrestrial Television

Broadcasting

Truyn hnh qung b mt t k

thut s

DTV Digital TV Truyn hnh s

DVB Digital Video Broadcasting Pht qung b video s

DVB-

CBMS

DVB-Convergence

of Broadcast and Mobile Services

Hi t cc dch v qung b v di

ng-DVBDVB-H DVB-Handheld DVB cho thit b cm tay


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Ch vi t


DVB-T DVB-Terrestrial DVB pht mt t

ESG Electronic Service Guide Hng dn dch v in t

ETSI European TelecommunicationStandards Institute

Vin tiu chun Chu u

FDM Frequency Division Multiplexing Ghp knh phn chia theo tn s

FEC Forward Error Correction Sa li trc

FLUTE FLUTEng dng truyn file c dng

trong cc mng n hng

GPS Global Positioning System H thng nh v ton cu

H.264 Tiu chun nn video ca ITU

HSDPA High-Speed Downlink Packet AccessTruy cp gi ng xung tc cao

ICI Inter Carrier Interference Can nhiu gia cc sng mang

IMT2000The ITUs framework for 3G

services

C cu ca ITU cho cc dch v

3G

IPDC IP Datacasting Qung b IP

IPE IP Encapsulator ng gi IP

IPsec IP security Bo mt IP

ISDB-TIntegrated Services Digital

Broadcasting Terrestrial

Tch hp dch v s pht qung

b mt t

ISI Inter Symbol InterferenceCan nhiu gia cc k hiu iu

ch

ITUInternational Telecommunication

UnionHip hi Vin thng quc t

LTE Long-Term Evolution Pht trin di hn

MBMSMultimedia Broadcasting and

Multicasting Services

Dch v pht qung b v ahng a phng tin

MediaFLO Media Forward Link OnlyCng ngh qung b a phng

tin ca Qualcomm

MPE Multi-Protocol Encapsulation ng gi a giao thc

MPEG Motion Pictures Expert GroupNhm chuyn gia v hnh nh

ng

NOC National Ops Center Trung tm iu hnh quc giaOFDM Orthogonal FDM Ghp knh phn chia theo tn s


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Ch vi t


trc giao

OFDM Orthogonal FDMGhp knh phn chia theo tn s

trc giaoOMA Open Mobile Alliance Lin on di ng m

OMA

BCASTOMA Standard for Broadcasting

Tiu chun OMA cho pht qung

b

PKI Public Key Infrastructure H tng kha cng khai

Podcasting

The broadcasting of multimedia

programs available on the Internet

in multimedia format.

Cc chng trnh qung b nh

dng a phng tin trn Internet

PPV Pay Per View Xem phim tr tin

PRG Pseudo Random Generator B to gi ngu nhin

QAM Quadrature Amplitude Modulation iu ch bin pha vung gc

QCIF Quarter Common Interface Format

nh dng giao din mn hnh

(176x120 NTSC v 176x144

PAL).

QPSK Quadrature Phase Shift Keyingiu ch kha dch pha vung

gcRI Rights Issuer B pht hnh quyn

RS Reed-Solomon code M Reed-Solomon

SAS Subscriber Authorization System H thng cp php thu bao

S-DMB Satellite-DMB Ch pht DMB v tinh

TPS Transmission Parameter Signalling Bo hiu tham s truyn dn

TV Television Truyn hnh

VOD Video on Demand Video theo nhu cu


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LI M U

Truyn thng a phng tin ni ln l mt lnh vc nghin cu pht trin ch

o. C th cc my tnh a phng tin m ra nhiu kh nng kt hp cc dng thng

tin s khc nhau nh vn bn, ha, m thanh v phim nh. V s lng ngi sdng a phng tin ngy cng tng nn nhu cu sch v cc h thng v truyn thn g

a phng tin rt ln.

Bi ging Truyn thng a phng tin ny s cung cp cac kin th c sinh

vin hiu truyn thng a phng tin trong 3 lnh vc: ng dng, phn nhng v kt

ni mng. Nh gip ch cho sinh vin thc hin nghin cu v pht trin trong lnh

vc h thng cc thng tin giao thc cn thit h tr a dng dch v a phng

tin.

Bi ging ny s gip cho sinh vin hc c cc cng ngh truyn thng a

phng tin ct li.Mc tiu ca cun bi ging ny l cung cp:

Ngun thng tin v cc ch quan trng trong truyn thng a phng tin. Cc tng, phng php phn tch, thit k v thc hin cc h thng truyn

thng a phng tin.

T chc ca bi ging nh sau:

Chng I: Bt u bng gii thiu s hi t ca truyn thng v my tnh ivi cc ng dng v dch v a phng tin. Tip gii thiu v cc cngngh truyn thng a phng tin, cc c s d liu a phng tin v nh

hng cng tc tiu chun ha a phng tin.

Chng II: Gii thiu cc nn tngtiu chun ha a phng tin, gii thiucc khun kh tiu chun ha ca ITU, IETF, ETSI....

Chng III dnh cho lp ng dng, phn ny trnh by v cc ng dng caITU, cc ng dng ISO MPEG, cc ng dng a phng tin IETF qua IP,

phn tch cc ng dng qung b.

Chng IV gii thiu tng quan lp nhng, m t m ha v chuyn i thngtin, v xy dng kin trc giao thc a phng tin, bn v cc m hnh h

thng cho cc dch v a phng tin cng vi cht lng dch v v hot

ng end-to-end trong cc h thng a phng tin, cc kh nng truy cp h

thng v dch v a phng tin, an ninh h thng. Chng ny s kt lun

bng phn nhng lung thng tin.

Chng V tp trung vo lp mng (phn pht/vn chuyn), bao gm nhiu vn lin quan ti cht lng dch v v hot ng mng, phn tch lu lng v

qun l lu lng, m hnh ha ngun video v lu lng mng, phn tch

qun l lu lng cng vi cc th tc nh tuyn trong truyn thng a


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phng tin. ng thi phn ny cng cp ti bohiu trong cc mng a

phng tin. Chng ny s m ra cho sinh vins pht trin tng lai ca

truyn thng a phng tin v hiu r hn tim nng ca truyn thng thng

a phng tin trong tng lai.

Tuy rt c gng v cn thn trong qu trnh bin son nhng chc rng khngtrnh khi nhng thiu sot, tc gi mong nhn c nhiu kin ng gp ca cc

ng nghip cng nh ca cc em sinh vin bi ging ngy cng hon thin hn.

Th gp xin gi v:

- TS. Nguyn Qu S- Khoa k thut in t 1, Hc vin Cng ngh Bu chnh Vin

thng

- Email: [email protected] ni, ngy 06/2010

Tc gi

TS. Nguyn Qu S
mailto:[email protected]:[email protected]


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CHNG ITRUYN THNG A PHNG TIN

a phng tin-mt s biu din ca ging ni, m thanh, hnh nh, ha v vn

bn tr thnh ch chnh trong cng ngh thng tin ngy nay. Cc cng ngh

thng tin ny hp nht truyn thng, tin hcv x l thng tin. Trong vi nm gn

y, c mt s lng hot ng ng k trong lnh vc truyn thng a phng tin

nh cc ng dng, phn nhng v kt ni mng. Nhiu k thut khc nhau t cc

nguyn l cc nhau nh x l nh tnh v phim, th gic my tnh, qu trnh x l ting

ni v m thanh, nhn dng mu thng k, l thuyt hc v cc nghin cu da trn d

liu v ang c khai thc.

Bi ging ny s cp ti: Xu hng tng lai trong lnh vc s ha S tng trng ca cc mng s v c bit l Internet Nng lc tnh ton ngy cng cao ca cc my tnh c nhn v my xch tay,

PDA v cc in thoi di ng

S hi t ca nhiu cng ngh khc nhau, trong c truyn thng, qung b,cng ngh thng tin v in t gia nh

S ni ln ca cc dch v v ng dng mi do s pht trin ca Internet vcc cng ngh v tuyn

S hi t ca cc cc mng tc cao, cht lng cao, x hi s yu cu ccng dng a phng tin thi gian thc nh l mt s m rng ca cc h

thng n phng tin ang c.

Hot ng end-to-end ca cc h thng v dch v a phng tin theo tiuchun ca ITU...

1.1. Gii thiuTruyn thng a phng tin ni mng c bt ngun t s hp li ca 2 xu

hng cng ngh:

Th nht l s pht trin ca tnh ton a phng tin Th hai l s tin b trong kt ni mng cho php vn chuyn tin cy d liu

s mc bng thng cao.

Cng nhn rng cc bn tin khc nhau c vn chuyn tt nht bng nhiu

phng tin khc nhau, nhng nhng ngi pht trin tnh ton a phng tin mong

mun b sung thm s phong ph ca cc m thanh v hnh nh ca th gii thc, t

dn ti vic m rng phm vica cc ng dng v cng a cc ng dng ny tinhng ngi s dng. My tnh c nhn tr thnh mt nt truyn thng trung tm thay


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th mt s lng ln cc thit b v h thng khc bao gm my thu hnh, my ch,

my fax, in thoi v chuyn th. Tuy th ng lc thc y kt ni cc thit b

khch hng ti mng a phng tin vn cn li. Ni mng cho php truyn thng

gia mi ngi vi nhau v cn cho khch hng tri nghim cuc sng, cc s kin

xa. Cc ng dng cho cuc sng, truy cp t xa bao gm hi ngh, gio dc, gii tr vgim st cc vng t xa.

Truyn thng a phng tin ang c khuyn khch bi cc nh hng sau

trong mng truyn thng:

Chuyn tip khng gin on t iu khin mng tp trung ti iu khin phntn

Kt ni khng gin on cc mng khc nhau vi chi ph hp l (chi tr c) Truyn dn hp nht khng gin on ca a phng tin vi nhiu mc QoS

(bao gm c multicast)Cc dch v truyn thng a phng (multicast) c k vng tr thnh mt trong

nhng ng dng ph thng nht, xut bn hng ny, phn phi phn mm, ti to c

s d liu v tip tc trong cc mng truyn thng a phng tin tng lai. cung

cp cc dch v truyn thng a phng trong cc mi trng truyn thng khng

ng nht, cn thit phi pht trin mt c ch m bo QoS m c th cung cp QoS

hp l cho mi ma ch theo bng thng v ti nguyn c th s dng.

s dng ti nguyn mng hiu qu, multicast theo thi gian thc v khng theo

thi gian thc u rt quan trng. Trong trng hp ny, s cn ti h tr nhiu lp

QoS v kh nng cho t trc bng thng ng.

Chng ny bt u vi m hnh truyn thng a phng tin. Sau cung cp s

hi t ca vin thng, tnh ton my tnh v in t dn dng, cng vi m t cc cng

nghcho truyn thng thng a phng tin. Cc ni dung nghin cu, tiu chun ha,

cc chnh sch truyn thng a phng tin cng c nhn mnh. Nhng nt chnh

ca cc tiu chun m ha hnh nh/m thanh s v vai tr ca n trong truyn thng

a phng tin cng c cp ti trong chng ny.1.2. S pht trin v hi t

a phng tin t n chng t c thao tc kt hp ca cc d liu thng tin

lin tc v c cc d liu thng tin ri rc. Cc thao tc ny bao gm bt gi, x l,

truyn thng, trnh din v/hoc lu tr. Cc d liu thng tin lin tc l d liu ph

thuc vo thi gian (nh d liu m thanh v hnh nh) trong cc h thng a phng

tin. Ngoi ra truyn thng a phng tin cn lin quan ti chuyn giao, cc giao

thc, cc dch v v cc c ch cho cc thng tin lin tc v ri rc qua cc mng s.

S truyn dn d liu hnh nh s qua mng phn phi TV chuyn dng khng phimng a phng tin khng cho php chuyn mt s dng d liu thng tin ri rc.


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Trong cc ng dng a phng tin ni mng, nhiu thc th khc nhau cng hp

tc cung cp nhng s bo m thi gian thc, v vy cho php d liu trnh din

c giao din ca khch hng. Nhng yu cu ny thng ch yu c xc nh

di dng cht lng dch v (QoS). Chng ta phn bit 4 lp QoS:

QoS khch hng (ngi s dng): Cc tham s QoS m t cc yu cu trn ccdch v ng dng v c th xc ng di dng cht lng thng tin (nh tr

end-to-end) v cc quan h thng tin (nh ng b lung gia cc lung hoc

trong mt lung)

QoS ng dng QoS h thng: m t cc yu cu trn dch v truyn thng theo QoS ca ng

dng. Chng c th c xc nh theo cc tiu ch nh lng (nh s

bit/giy, thi gian x l cng vic) v cht lng (nh multicast, ng b gia

cc lung, khi phc li hoc vn chuyn d liu theo th t) QoS mng: m t cc yu cu trn dch v mng (nh ti mng hoc cht

lng mng). Cc ng dng a phng tin m phn QoS mong mun trong

sut giai on thit lp kt ni cng vi lp h thng hoc c th trc tip vi

lp mng, nu nh h thng khng th cung cp QoS cho ng dng.

1.2.1. S hi t ca vin thng v tin hcHin nay quan h gia vin thng v tin hc phong ph hn rt nhiu so vi

trc. Cc quan h ny s tr nn d phn bit hn trong tng lai rt gn. S hi t

ny v s tip tc tc ng mnh ti cng ngh, cng nghip v x hi.

d hiu chng ta s chp nhn mt m hnh 3 mc cho mt mng thng tin v

cc dch v, ng dngca truyn thng a phng tin.

Hnh I-1 M hnh 3 mc cho mt mng truyn thng a phng tin

Mt ng dng l mt tp hp chc nng cung cp cho ngi s dng. Chng ta

quan tm y l cc ng dng c ni mng, chng c phn phi qua cc mi

trng vin thng v tnh ton phn tn. Cc v d ca cc ng dng ni mng l th

in t, in thoi, truy cp c s d liu, truyn file, duyt Web v hi ngh truyn

hnh. Cc v d ca dch v c th l truyn ti m thanh, hnh nh, qun l h thng

file, in, cc c ch thanh ton in t, m ha v phn phi kha v vn chuyn d liutin cy. Hai loi ng dng ni mng lin quan l:


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ng dng khch hng-khch hng, trong hai hoc nhiu ngi s dngtham gia vo mt s mi trng dng chung

ng dng khch hng-my ch thng tin, trong mt khch hng tng tcvi mt h thng t xa, nhn hoc tng tc vi thng tin lu tr trong h

thng.Mi ngi s dng trong mt ng dng ni mng tng tc vi mt thit b u

cui ni b, thit b ny li trao i thng tin vi cc my tnh hoc thit b u cui

xa qua mng. Chng ta cng c th tch cc ng dng ni mng thnh hai lp tng

ng vi quan h tng tc ca ngi s dng vi mt m ch hoc vi mt ngi s

dng khc:

Ngay lp tc: mt ngi s dng tng tc vi mt my ch hoc mt ngis dng khc theo thi gian thc, dch v ny yu cu v tr v khong lng

ln nht. Tr hon c: Mt ngi s dng tng tc vi mt ngi s dng khc hoc

mt my ch vi quan h khng c nh v tr khng quan trng.

1.2.2. Kin trc ca cc dch v ni mngCc ng dng ni mng c thc hin bi cc nt thit b u cui hoc cc thit

b b u cui c kt ni vi nhau. V chc nng c hai kin trc c bn c th t

dng cho cc dch v ni mng(Hnh I-2):

Peer-to-Peer: Ngang hng V Client-Server

Hnh I-2 Kin trc ngang hng v Client-Server

Trong cu trc ngang hng, hai hoc nhiu thit b u cui, mi thit b gn vi

mt ngi s dng, trao i thng tin qua mt knh cung cp mt ng dng ni

mng gia nhng ngi s dng. Thnh phn truyn thng ni mng gia cc cp

ngang hng thng l i xng v chc nng v ti nguyn knh.

Cn trong cu trc Client-Server, mt thit b u cui Client ca ngi s dng

trao i thng tin vi my tnh ch, khng lin quan trc tip ti ngi s dng nhng

thc hin chc nng my ch thng tin. Chc nng ny thng khng i xng, trongkhi my ch thc hin chc nng chnh hoc truy cp c s d liu th thit b u cui


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client tp trung vo giao din ngi s dng. Cc thnh phn truyn thng thng l

khng i xng vi hng t my ch v client (knh hng v) thng yu cu bng

thng ln hn.

Hnh I-3 Mt ng dng gia hai ngi s dng

c thc hin bng kin trc ngang hng hoc client-server

1.2.3. Lin kt

Hnh I-4 Hai m hnh ca cc dch v ni mng: dc v ngang

C 2 m hnh kin trc cho cc ng dng ni mng nh (Hnh I-4): Lin kt ngang

v lin kt dc. Trong hu ht cc lin kt dc, mt h tng chuyn dng c s dng thc hin tng ng dng, ngc li m hnh linkt ngang c cc c im sau:

Mt hoc nhiu knh truyn ti d liu lin kt v lung thng tin nh mthanh v hnh nh c cc tham s QoS c th cu hnh c

Mt tp hp cc dch v nh cc dch v phn nhng (th vin. chuyn tinin t, qun l kha.v.v.) v cc dch v thng tin (m thanh, hnh nh...)

lun sn sng cho tt c cc ng dng.

Mt tp cc ng dng a dng sn sng cho ngi s dng


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u im chnh ca m hnh ngang l cho php lin kt cc thng tin khc nhau

trong mi ng dng, cng nh cc lin kt cc ng dng khc nhau trong knh. Hin

nay trong vin thng, cc mng ch yu l mng a dch v.

Mt s khc bit khc gia cc mng l chng l cc mng hiu bit ni dung v

khng hiu bit ni dung hoc hiu bit ng dng hoc khng hiu bit ng dng.Cc mng lin kt dc thng l hiu bit ni dung, c ngha chng nhn dng c

cc ng dng m chng vn chuyn (chng hn nh hi ngh truyn hnh, truyn file,

truyn hnh theo yu cu-VoD). Trong khi cc mng lin kt ngang thng l m ng

dng (chng hn nh Internet).

Mt c im quan trng ca lin kt ngang l giao din m vi nhng c im

ring. Chng c mt b ch tiu k thut c th s dng t do v cho php nhiu thc

thi khc nhau t b ch tiu ny. Mt c im ring mong mun khc l kh nng

thm mi hoc ng chc nng.Chng ta c th nh ngha chc nng ng khi khngmun xut bn hoc cho t chc khc m rng. Chc nng ring ny c th c pht

hnh v m rng nhng phi chu bo v quyn s hu tr tu.

Mt mc ch ca cc giao din ngang m l ng gp cc m un tho ri nh

s c lp ca ng dng vi c s nn tng.

1.2.4. S tnh ton c th truyn ti cS tnh ton c th truyn ti c a ra 4 u im chnh:

Kh nng m rng: Cho php c b nh (tm thi v c nh) v tnh ton tc trn bt k my tnh hoc thit b u cui no thun tin nht. V d,

trong mt ng dng client-server, cho php s tnh ton c dch chuyn t

my ch xung cc client ca n, nh vy trnh c qu ti trn my ch

Khong lng: Thi gian thi hnh chng trnh loi b c khong lng do trtruyn ti trn mng.

Truy cp d liu ni b: Mt chng trnh truyn ti c c th truy cp vthay i s liu lu tr trn bt k my tnh no m n c th chuyn n.

S lin kt: Nu cc chng trnh lin quan ti mt ng dng phn tn to rat mt ngun chung, c th ni rng chng lin kt vi nhau theo s iu phi

hot ng ring.

1.3. Khung c s cng ngha phng tin v truyn thng a phng tin c nhn nhn tng th nh l

mt h thng phn cp. Cc ng dng v phn mm a phng tin cung cp mt mi

trng tng tc cho cc i tng s dng. Khi mt my tnh yu cu thng tin t

cc my tnh hoc my ch xa, thng tin a phng tin phi vn chuyn qua mng

my tnh. V s lng thng tin truyn dn hnh nh v m thanh c th rt ln, nn gim tr truyn thng thng tin a phng tin ph c nn trc khi truyn qua


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mng. Cc rng buc nh l gii hn tr v bin thin tr c s dng mbo

c cc hiu ng m thanh v hnh nh pha thu. Do cc mng truyn thng

ang thc hin nng cp lin tc nng cao kh nng truyn thng a phng tin.

Cc mng ni b c s dng kt ni cc my tnh ni b vi cc thit b khc.

Mng vng rng (WAN) v Internet ni vi mng ni b (LAN). Cc tiu chun mihn v tt hn lin tc c pht trin cung cp mt xa l thng tin ton cu, m

qua thng tin a phng tin s c chuyn qua.

1.3.1. Cc cng ngh a phng tinC mt s lng ln cc cng ngh v sn phm a phng tin c chp

thun rng ri nhQuickTime v Video for Windows.

C mt tiu chun ISO vi tiu MHEG (Multimedia Hypermedia Information

Coding Expert Group)-tiu chun ny l ISO/IEC JTC1/SC29 WG12 dnh cho cc lp

i tng iu khin trnh din thng tin a phng tin v siu thng tin. MPEG -5 ltiu chun h tr phn phi cc ng dng a phng tin tng tc trong mi trng

client/server a nh cung cp thit b. Cc nh pht trin s dng cc tiu chun ny

pht trin ca\cs ng dng, bi v s trnh din thng tin l c th thay th cho nhau

trong cc kh nng m t ti liu ca HTML (Hyper Text Markup Language). MHEG

cung cp cc kh nng gim st a phng tin b sung . Tiu chun Abstract Syntax

Notation (ASN.1) ca ISO c s dng miu t gia cc nn tng my tnh khc

nhau, cc ngn ng v h iu hnh khc nhau. Tiu chun s dng khng gian (ta

3 chiu) v thi gian ng b biu din.

a/ SONET (Synchronous Optical Network)SONET c Bellcorepht trin cho kt ni mng vng rng ANSI v c s

dng nhiu nc trn th gii, ban u l M v Canada. Tng t Chu u, SDH

(Synchronous Digital Hierarchy) l mt tiu chun ca ITU-T. SONET v SDH v c

bn tng thch vi nhau tn hiu truyn ti ng b (STS 3C 155,52Mbps) v n

ub truyn ti ng b (STM-1). SONET s dng mt khung vn chuyn thng tin

tc thp hn (cc nhnh: m thanh, hnh nh v d liu). Bng thng cho minhnh c bo m. SONET s dng ghp ng b (SMUX) v cc b ghp

add/drop (ADM) chn mt tn hiu t ngun v tch tn hiu pha thu.

b/ Cc mng my tnhMng my tnh l cc phng tin truyn ti a phng tin. Mt s c im

chnh ca cc mng my tnh:

Cc mng ni b (LAN) 802.x: Tiu chun 802.x do IEEE nh ngha chacc tiu chun sau:

o 802.1bao gm quan h gia 802.X v m hnh tham chiu lin kt hthng mkt ni 802.x bng cc cu v qun l mng


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o 802.2iu khin knh logic nh a ch cc im a dch v cho nhiung dng ng thi v cho cc hot ng nh hng kt ni, phi kt ni

v xc nhn.

o 802.3Tiu chun Etherneto

802.4Giao thc tiu chun tokeno 802.5Tiu chun token ringo 802.12Tiu chun 100VG-AnyLAN.

Ethernet l LAN c trin khai rng ri nht v mi hn l tiu chun Fast-

Ethernet. Token Bus c trin khai rt hn ch v vn sn xut.

Token Ring s dng cc trm theo mt vng trn v s dng mt token trnh

tranh chp.

Fast Ethernet v 100VG-AnyLAN: Ethernetban u c thit k ni ccmy trm bng cp ng trc, sau c pht trin ln cc i dy xon ni cc my trm ti mt hub. Tc truyn ti l 10Mbps. nng cao tc

, fast Ethernet c pht trin cung cp 100 Mbps v phi s dng

mt Hub kt ni cc my trm. 100VG-AnyLan c thit k gim

st truyn thng a phng tin thng qua mt phng thc nhu cu yu tin.

N n nh u tin cao cho a phng tin, tri vi Ethernets dng a truy

nhp cm ng sng mang vi pht hin xung t (CSMA/CD). Ethernet khng

th n nh u tin cao cho lu lng thi gian thc nh d liu m thanh v

hnh nh. Cc Hub ca mt 100VG-AnyLAN c th c kt ni theo hnh

sao phn cp vi ln nht 3 lp, v LAN token ring c th c kt ni nh l

mt phn ca mng. Cp s dng trong fast Ethernet c th dng trong

100VG-AnyLAN.

Cc LAN c chuyn mch: Mt mi trnghf dng chung trong LAN trnh by trn s c cc vn v kh nng m rng. Khi s lng cc my

trm tng ln, bng thng hiu dng ca mi trm bgim xung. Vn ny

c th c lm nh bt nh s dng mt LAN c chuyn mch, LAN nykt ni cc my trm qua mt hub chuyn mch. Truyn thng khng th b

chn nu khng c tranh chp i vi cng ch n. Hn na hot ng ca

mng c th m rng c. B chuyn mch c th hiu v tr mt my trm

LAN thng qua iu khin truy cp mi trng (MAC) v a ch trong mt

my trm LAN phm vi tng t nh s dng cu ni.

o B chuyn mch lp 2 thc hin lp 2 ca m hnh tham chiu OSI vx l nh mt cu ni. N c th kt ni nhiu LAN v my trm. B

chuyn mch lp 2 nhanh hn cu ni bi v n s dng cc mch tchhp chuyn dng (ASIC) chuyn mch lu lng.


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o B chuyn mch lp 3 c thit k nng cao hot ng v gim chiph router, router dng kt ni mng lp 3 ca m hnh tham chiu

OSI. Mt router thc hin 2 chc nng: (1) to ra bng nh tuyn cho

chng tip theo nh thu thp thng tin ca cc router ln cn cng nh

(2) chuyn mch khung ti cng ra thch hp da trn bng nh tuyn.B chuyn mch lp 3 c thit k thc hin chc nng th hai bng

ASIC. Bng nh tuyn c th c c t mt my ch nh tuyn (c

thit k thc hin chc nng u tin). Mt s b chuyn mch c th

dng chung mt tuyn gim chi ph v ASIC c th chuyn mch

nhanh hm l mt router da trn RISC.

c/ Asynchronous Transfer Mode (ATM)-Sinh vin tnghin cu tm hiud/ TV ch t lng cao (HDTV).The Federal Communications Commission (FCC) thu ht v nhn c cc

xut vo nm 1988 cho HDTV. Hip hi Grand bao gm General Instruments,

Philips, David Sarnoff Research Center, Thomson Consumer Products, AT&T, v

Zenith c thnh lp nm 1993. Hip hi Grand chn MPEG-2 Main Profile v

High Level m ha v truynti hnh nh, v AC-3 do Dolby Labs pht trin cho

m ha m thanh, trong khi s dng MPEG-2 TS cho ng gi v ghp knh. Bng

thng ca knh truyn l 6MHz, tc d liu 19,4 Mbps, trong khi cc gi MPEG

c trn v b sung thm cc thng tin sa li.

e/ Cable TV (CATV)Cc dch v mi t CATV bao gm in thoi, fax, video theo nhu cu v truy cp

my tnh ti Internet. Mt modem cp phi c s dng kt ni Internet c ni

gia cp dn v cc card giao din mng Ethernet. Bng thng ca cp c dng

chung cho tt c cc khch hng trn cng cp CATV nh l Ethernet.

Ty theo nh cung cp thit b modem cp, tc hng v t Headend ti gia

nh t 4-27Mbps v hng i t gia nh ti headend l 96Kbps-27Mbps. CATV

thc hin cc dch v thoi thong qua SONET ni Headend vi mng in thoichuyn mch cng cng PSTN.

f/ Mch vng ( ng dy) thu bao s (DSL). cnh tranh vi CATV i vi cc dch v VoD v Internet, cc cng ty in

thoi ang trin khai DSL. DSL bao gm:

ISDN Mch vng thubao s khng i xng (ADSL) DSL tc d liu cao (HDSL) DSL n ng (SDSL) DSL tc d liu rt cao (VDSL)


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DSL h tr in thoi tng t cng nh giao din tc c s ca ISDN (BRI)

(2 knh d liu B 64Kbps v 1 knh iu khin D 16Kbps, v c 384kbps cho hi ngh

truyn hnh. DSL c th trin khai cho nhiu khch hng. Cng ngh DSL p ng

c truyn thong a phng tin. Bng thng DSL chuyn dng cho 1 khch hng

trong khi bng thng ca cp dng chung cho tt c cc khch hng (b chia s). g/ Internet.Internet pht trin t mng d liu cng ng ng thnh mt h tng x hi

thng tin ton cu. Cc khch hng ang tin tng vo Internet trong kinh doanh,

khng ch cc dch v World Wide Web v cc ng dng truyn thng nh truyn

Email, truyn file m cn ang ngy cng tng cc ng dng thi gian thc nh m

thanh, hnh nh thi gian thc v cc ng dng dng chung.

Mc tiu thit k ban u ca Internet l lm mng d liu c kh nng chu li

cao cho quc phng. thc hin c, s lng d liu dng chung trong mng vcc h thng u cui l ti thiu, l thng tin tnh ton tp hp cc tuyn.

Trc y cc routerr s dng hng i FIFO (vo trc ra trc) cho tt c cc lu

lng v thc hin n n gin. Nhng saumt thi gian ngy cng tng nhu cu thc

hin qun l cho cc dng khc nhau, cho cc khch hng khc nhau v cho cc mng

qu ti.

Cc giai on pht trin giao thc v thc hin mng Internet nh sau:

Giai on u nh ngha dch v v tng chuyn kiu dch v c xut. Cc router phn bit lu lng hoc bng kim tra cc bit c bit trong

giao thc IP hoc bng giao thc ng dng. Tt c cc giao thc truyn file

(FTP) v giao thc ng dng World Wide Web, giao thc truyn siu vn bn

hot ng qua giao thc iu khin truyn dn (TCP), giao thc ny m rng

t giao thc IP khng tin cy cung cp vn chuyn ng dng tin cy v

trnh t.

Tc dng ca nh tuyn kiu dch v v iu khin tc ngn TCP l mngcung cp dng chung cng bng cho cc khch hng. Bi v tt c cc khchhng TCP c chung mt dung lngmilc, nn thi gian s dng b thay i

ph thuc vo s lng ngi s dng hin ti. Mt h thng truy cp thu

ring c cc nh khai thc Internet a vo khai thc.

Truyn thng nhm rt hu ch cho cc ng dng lin quan ti nhiu thit bthu v pht ng thi. ng trc multicast l mt chng ph o trn mng

Internet hin ti cung cp dch multicast, nh gim c ng k ti trn

mng cho cc ng dng nh vy. Ban u ng i ta hy vong co th s dung no

cho cac giao di ch thay th , nhng thiu cac giao th c truyn tai (end-to-end) h tr chng. Multicast a c trin khai nhanh chong hn cho ho cac ng


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dng da trn UDP , cho cc chng trnh hi ngh truyn hnh v m thanh .

Cc ng dng in hnh da trn UDP cung cp tc gi gn nh c i nh t i

mng. h tr s lng ty khch hng s dng cc ng dng ny m

khng biqua tai, Internet a phai m rng bng m t s cach nh :

ot trc ti nguyn : c th lm vic vi mt lp ln cc ng dngnhng se lun lun la m t s ng dung chim phn l n dung lng

mng

o Tnh cc da trn s dng: phng th c nay a nhn c s quan tmtronng nghin c u phat trin tiu chun

1.3.2. Kt n i mang a phng tinNhiu ng dung nh th in t , h i nghitruyn hnh , v cc h thng lm vic

cng tac yu cu a phng tin c ni mng. Trong cac ng dung nay , cc i

tng a phng tin c lu ta i m t may chu (server) v c chi li (play back) cc my khch (Clients). Cc ng dng nh vy c th yu cu qung b d liu ti

cc v tr xa khac nhau ho c truy c p nhng ni tr cac tai nguyn a phng tin

l n. Cc mng a phng tin yu cu tc hoc bng thng rt ln , thm ch ngay

c khi d liu c nn . Cc mng truyn thng c dng cung c p cc truyn

dn lit do (error-free). Tuy nhin hu ht cac ng dnga phng tin co th chi u

dng li truyn dn do s hong ho c tn tht go i ma khng cn truyn la i ho c s a li .

Trong m t s tr ng h p , tha man cac yu cu vn chuyn th i gian thc hoc co

c ng b , m t s go i thm ch bi bo i . Chng ta c th p dng cc giao thc

truyn dn trong s thp cho cac mang a phng tin . Cc giao thc ny khng th

chp nhn pht li bi v chng c th gy ra tr khng chp nhn c .

Cc mng a phng tin cung cp khong lng thp cn thit cho hot ng

tng tac. V dliu a phng tin phai c ng b khi no t i ch , cc mng nn

cung cp truyn dn ng b co di ch thp (jitter).

Trong cc mng a phng tin, hu ht cc trao i thng tin l a im tri vi

truyn thng truyn thng. V dnh cc hi nghlin quan ti nhiu hn 2 thnh vintham gia cn phn phi thng tin bng cc thit bkhc nhau ti tng thnh vin khc.

Cc mng hi ngh s dng cc phng php phn phi multicast v ni cu. Multicast

ti to mt tn hiu vo duy nht v vn chuyn n ti nhiu ch. Cu ni kt hp

nhiu tn hiu u vo thnh mt hoc nhiu tn hiu ra, sau vn chuyn cc tn hiu

ti ti cc thnh vin.

Cc mng truyn thng Ethernet khng ph hp vi a phng tin v n ch cung

cp 10Mbps, thi gian truy cp khng b gii hn, cn khong lng v dch khng

th don c. Cc mng token-ring cung cp 16Mbps, chng c thgim stv aphng, tuy nhin khong lng truy cp c th rt cao.


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Mt mng FDDI (Giao din d liu phn phi trn cp quang) cung cp bng

thng 10Mbps, cho a phng ti. chng b, FDDI c khong lng truy

cp nhv dch nh. N cng m bo tr truy cp b gii hn v bng thng trung

bnh dbo c i vi lu lng ng b. Tuy nhin do chi ph cao, cc mng

FDDI c s dng chyu lm mng ng trc nhiu hn l mng cho cc mytrm.

Cc la chn tn km hn l cc mng truyn thng mrng:

Fast Ethernet cung cp ln ti 100Mbps Token ring u tin: lu lng a phng tin c tch ring khi lu lng

thng thng theo u tin. Hnh I-5 ch ra mt tokenring u tin. B qun

l bng thng ng vai tr chnh nhcc phin theo di, xc nh u tin v

ng k phin a phng tin.

Hnh I-5 Token ring u tin

Chng c 3 phng thc vng u tin cho cc ng dng hi ngh truyn hnh:

u tin nh nhau i vi video v cc gi khng ng b u tin cao c nh cho cc gi video v u tin thp c nh cho cc gi

khng ng b

u tin cao c iu chnh theo thi gian cho cc gi video v u tin thp cnh cho cc gi khng ng b

Phng thc th nht i hi cnh tranh trc tip gia hi ngh truyn hnh v cctrm ng bv phng thc ny t c tr mng nh nht cho cc khung khng

ng b. Tuy nhin n lm gim cht lng hi ngh truyn hnh.

Phng thc thhai, trong cc trm hi ngh truyn hnh c u tin cao cnh

skhng b suy gim cht lng hi nghnhng lm tng tr mng khng ng b.

Cui cng h thng u tin c iu chnh thi gian cung cp scn bng gia hai

phng thc trn. Cht lng ca hi ngh truyn hnh tt hn phng thc th nht

trong khi tr mng khng ng bcng ngn hn phng thc th hai.

1.3.3. Hi ngh a phng tin


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Hi ngh a phng tin cho php s lng ln cc thnh vin trao i thng tin

a phng tin qua cc mng thoi v d liu. Mi thnh vin c mt my trm a

phng tin kt ni vi cc my trm khc qua cc mng tc cao. Mi thnh vin

c th gi hoc nhn hnh nh, m thanh v d liu; ng thi c th thc hin cc

hot ng cng tc nht nh. Hi ngh a phng tin s dng khi nim khng gianlm vic o dng chung, khng gian ny m t mt phn mn hnh c ti to li

mi my trm.

Thch thc ln nht trong hi ngh a phng tin xy ra khi cc thnh vin hi

nghlin tc pht i cc dng hnh nh v m thanh. Cc nghin cu tp trung vo kt

hp cc dng ny vi nhau to thnh mt dng ghp. Ngi ta a ra nhiu cng

ngh v giao thc cho nh s phng tin v kin trc truyn thng ti u.

Cc h thng hi ngh a phng tin phi cung cp nhiu chc nng nh thit lp

nhiu cuc gi ng thi, truyn dn tnh trng hi ngh , iu khin m thanh va hnhnh theo thi gian thc ,phn b ng tai nguyn mang , truyn d liu a im , ng

b khng gian dung chung v iu chnh h thng di cc iu kin li .

Cc kin trc h thng hi ngh c th c phn bit bng v tr ca cc chc

nng tng h p m thanh va cac cu hnh kt ni cu a chung . Do vyc 2 lp kin tru c

c tn gi l Tp trung v Phn tn , ngoi ra lp th ba l lp lai . Cc h thng t cc

h ny c th c nh gi di dng cht lng , kh nng m rng , kh nng m

rng, kh nng tng thch vi cc tiu chun hin ti v thc t .

a/ Kin tru c h i nghi tp trungH i nghithoa i t xa a c cung cp bng cac cu ni h i nghit p trung , nh ng

ng i tham d quay s t i m t trung tm vao m t th i im a chun b trc . Cc

im cui thit l p kt ni m t -m t (t ng i m t ) v cc kt ni bo hiu . Cc cu

ni thit l p cac ng dn d liu gi a cac im cui nh tng h p cac tn hiu u

vo vi nhau v tr li tn hiu a tng h p cho cac h i nghi . tranh ting vong ,

nhng ng i tham d nhn m t tn hiu m thanh r rng bao gm tt c m thanh ca

nhng ng i tham d tr ting no i cu a ho . Cu ni lam giam nhiu nn va kha n ngxy ra ting vng nh ch tng hp M trong N ngi ni .

b/ Cc kin trc hi ngh phn tnTrong m t h i nghi phn tan , cc thit b trao i vi nhau gia cc im cui m

khng s dung cu t p trung . Cht lng m th anh c tng ln nh loa i bo c

chuyn tip cu a cac cu . Tuy nhin cac im cui phai co kha nng nhn va tng h p

nhiu dong ng th i . S phn tan ch c nng x ly m thanh qua cac im cui dn

t i khng yu cu tn h toan nhiu nh cac cu ni thng th ng . H i nghi phn tan

c biu din bng cac m hnh full -mesh va m hnh h i nghimulticast (aphng).


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Trong h i nghifull -mesh (N thanh vin ), m t kt ni phng tin full -duplexc thit l p gia tt ca cac cac thanh vin tao ra cac kt ni mesh . Mi im

cui phat m t ban sao dong d liu cu a no t i N-1 im cui khac va nhn N -

1 dng v. Mi c p u cui co th trao i thng tin v i nhau bng m t kiu

CODEC bt ky . iu khin bao hiu cu a cac i

m cui co th

t p trung maych, sao trang thai cho h i nghic duy tr , trong o trang thai h i nghico

th bao gm cac thanh vin h i nghiho c cac yu cu dch v m thanh b

sung.

H i nghimulticast la ng ngha v i h i nghivung rng qua MBone . Trongm t h i nghimulticast , mi im cui phat m t ban sao duy nht cu a dong d

liu t i i a ch multicast v nhn N -1 dng v. i vi pha thu , khng co g

thay i so v i ki ch ban cu a full -mesh tr cac dong v trn 1 cng. H i nghi

multicast la m t dang khac cu a h i nghi t p trung. Thay v kt ni t i m t cuh i nghicac im cui tham gia h i nghi bng ng ky t i m t i a ch

multicast cu a h i nghi . i a ch nay co th c quang cao b i m t trong

nh ng im cui hoc b i m t may chu trung tm hoc c phn phat t i cac

thnh vin tham d trc khi hi ngh.

c/ L p lai (gia phn ta n va tp trung)Kin tru c h i nghikhng co chuyn tip la m t kin tru c la i gi a cac tip cn kin

trc tp trung v phn tn truyn thng . M hnh nay s dung m t cu ni khng co

trung gian (cu ni h i nghichon -v-chuyn tip cho nhiu ng i no i ng th i ). Cu

ny chn M ngi ni hin ti chuyn cc tn hiu nn ca h ti N -M im cui ,

ti chng c gii m v kt hp li .Nu M=2, ng i no i th nht nhn tn hiu

ca ngi ni th hai v ngc li .

Kin tru c h i nghikhng co chuyn tip nay co m t s c im cn quan tm . H

thng loa i bo c chuyn tip , hot ng c lp vi CODEC m thanh v gim yu

cu tnh toan cu a cu . Nhc im lag cac m rng cu a giao th c cn phai mang d

liu cu a h i nghi , trong khi cac im cui phai h tr thit biu cui va kt h p nhiudng d liu ng thi.

1.3.4. MulticastingInternet a ch ng kin m t s tng tr ng phi th ng cung v i s phat trin cu a

nhiu ng dung m i hn , tinh vi hn o i ho i mang phai co cac ch c nng phong phu

hn. Vi c lam chu s tin b cu a cac cng nghbng rng , v tuyn va Web hon ton

c th thit k va thc hin cac mang hn h p c l n co th h tr phn phi n i

dung, h i thithoa i , dng m thanh , hc t xa , khng gian lam vi c cng tac va cac

dng y . Theo i nh h ng nay, multicast a tr thanh m t cng nghcho phep vaong vai tro quan trong trong thit k ,pht trin v khai thc nhiu ng dng , dch v


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hin nay va tng lai da trn vn chuyn go i hiu qua t i nhiu ch ng t h i. M c

d khi nim ca multicast c v nh rt hp dn bn ngoi nhng thc ra l rt kh

khn thc hin trong mi tr ng nhiu nha cung cp di ch vu Internet .

V i nh ng tin b trong cng nghhnh anh s , dch v video theo nhu cu a

trin khai trong thc t m t vai nm gn y . Hthng VoS l n cn lu tr vai trm b phim va h tr hang nghn khach hang.

phat trin m t giai phap tit kim chi ph , nhiu nha nghin c u a ngh in c u

trn nhiu tai nguyn khac nhau , cc chnh sch phn chia s dng kh nng multicast

ca cc mng truyn thng tin tin . Trong m t m t nm gn y , cc phng thc

qun b khc nhau nh pyramid (kim t thap ), harmonic (iu hoa ), skyscraper

(chc tri ) a c xut lam giam tr kh i tao va yu cu bng thng

nh s dung b m thu .

Ngoi qung b ,phng th c multicast cung c s dung phuc vu m t nhomcc khch hng ti thiu yu cu hthng . Khc vi phng thc qung b c bng

thng bigi i han, yu cu bng thng cho phng th c multicast c l p v i tc t i

ca cc phim video . Gi a nhiu cach tip cn nhom khac nhau trong hthng

multicast nay th qua th i gian nhom (batching-by-timeout) v kch thc nhm l hai

cch tip cn ph thng nht s dng cc chnh sch n gin . M t s phng th c

nhm mi nh mang thch ng v nhm thch ng c xut cho cac di ch vu

theo yu cu th i gian . R rng, truyn dn quang ba se la hiu qua nht nu video la

rt ph bin . Tuy nhin nu tc t i cho video khng u th m t s tai nguyn se bi

b ph v phng thc nhm se hiu qua hn.

1.3.5. Cc cng ngh cho ni dung in t(e-Content)M t cng nghm i co hiu lc co ngha la m t cu thu c cu a nganh cng nghi p .

C thc ca thi i chng ta l kt qu ca hiu ng kt hp 3 cng ngh chnh:

X ly tn hiu: chuyn i cac tn hiu tng t thanh cac tn hiu s ; Cng nghthng tin: cho phep x l d liu dng s

Vin thng: cho phep truyn d liu s n/t bt ky ch nao trn th gi i .N i dung s t i c cac khach hang cui go i la n i dung in t .

a/ X ly tn hiu s Vo thp k 80, Philips va Sony a gi i thiu m t loa i a m nha c m i - Compact

Disc ho c CD ho c CD -Audio. Loi a ny s dng cc cng ng hquang-in t

cung cp m thanh cht lng tr ng quay ma khng thay i cht lng theo th i

gian. CD a la m t thit bithanh cng va s lng u a CD trn th gi i a ln t i

hng trm triu b . Khng ging v i casset, cc khch hng thng thng khng th

copy t ng bit cu a CD ma ch co th sao chep u ra tng t.


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Vo u nhng nm 1990, CD-ROM-m t thit bingoa i vi cu a may tnh khai thac

k thut s tng t CD tr thnh mt thit bi ph bin lu tr d liu may tnh

v cc chng trnh. T i gi a nh ng nm 90, CD-ROM a tr thanh m t thit bingoa i

vi tiu chun cho may tnh PC va sau o la cac CD co th ghi c , khi o hang triu

ng i s dung co th

sao chep cac a CD cu a ho . ng thi cc cng ngh nn mthanh-hnh nh t c hon thin v c tiu chun ha . Hng triu CD video

c th xem phim hng gi trn mt a nh CD , cc u thu truy n hnh s va DVD -

m t th hm i cu a CD co th lu tr cac b phim 2 gi cht lng cao . Cc thit b

ny tha mn c khch hng , cung cp cho khach hang cac thit bingay cang

nh hn vi nhiu chc nng hn v nhiu hnh anh, m thanh hn.

b/ Cc mng k thut sVo gia nhng nm 90, Internet a a t c m c s dung m rng t i mi

tr ng giao duc/nghin c u/quc phong.Ngn ng HTML-m t tiu chun khun dangtrang v i kha nng i nh ngha ng dn a tao ra World Wide Web v i hang triu

trang vn ban v i hoa c siu lin kt va s dung may tnh co th truy c p c

bng cac trnh duy t . M t s cng ty a b sung them m t s thng tin khac nh hnh

nh v m thanh . Tuy nhin tc bit thp co th s dung cho phn l n khach hang

(vi chc kbps) a lam giam cht lng m thanh va hnh anh .

c/ Chui gia tri Cc m hnh kinh doanh ang pht trin khng ngng , i lu ccho phep va i lu c

biu hin s phat trin cu a cng ngh . S dung in hnh hin nay cu a WEB la

qung b sn phm hoc dch v .

Hnh I-6 m ta cac nhn t trong chui gia tri . Trung tm cu a hnh ch r 3 nhn t

chnh: nh cung cp ni dung , ng i ban le va thit bicu a ng i tiu dung .Ngoi ra

cn c 4 nhn t n a:

Cc dch v ti chnh: gii quyt cc giao dch gia 2 khi bt ky Cc dch v th vin : cung cp thng tin n i dung va h tr khach hang tm

kim n i dung quan tm Cc dch v cng ngh: yu cu biu din, s gn kt,phn phi, tiu dung n i

dung ho c d liu v n i dung

Cc dch v vn chuyn: chuyn n i dung gi a nh ng ng i s dung


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Hnh I-6 Chui gia tri

Ni chung, c th ni rng c gia 2 khi co m t lung n i dung va d liu lin

quan t i n i dung : m t lung cac quyn s du ng, m t lung cac quyn cng nghcho

php mang v tiu th ni dung v mt lung ti chnh gii quyt chuyn giao ccquyn n i dung va lin quan . Hn na , lu t phap ong m t vai tro quan trong trong

cho phep va hu y bo m t s ch c nng cu a m t s khi.

Ngoi ra cn mt s cng ngh khc:

Biu din thng tin: MPEG-1, MPEG-2 v MPEG-4 M ta, nhn dang va bao vn i dung

1.4. Khung c s tiu chun ho aKhi cac cng nghm i a ra cac ch c nng va hot ng tt hn th nhu cu i

v i cac tiu chun ngay cang tr nn quan trong . Khng co cac tiu chun , cc dch vth i gian thc se bianh h ng v cac b ma hoa va giai ma khng th trao i thng

tin v i nhau. Cc dch v khng theo thi gian thc s dng cc dng bit lu tr cng

c th bt li hoc bi v s khng sn sng ca cc nh cung cp dch v trong m

ha ni dung ca h theo nhiu khun dng tha m cc kh n ng ca khch hng

hoc b i v s min cng cu a khach hang khi phai cai t s lng l n cac b giai

m.

S tiu chun hoa cac h thng truyn thng tr c y c tao ra b i cac nganh

cng nghi p theo s kt h p do c. a phng tin kt h p cac dang truyn thng khac

nhau yu cu m t cach tip cn m i -ngang hoc theo lp - pht trin cc tiu chun .

iu o co ngha m t s thay i cn ban v cach ma cac tiu chun c tao ra . S

tng c ng bng thng cho cac khach hang cui cung gy ra s thay i v vai tro cu a

quyn lc cng cng trong iu chnh s dung cng nghcung cp di ch vu.

C nhiu nh ngha v tiu chun ha . Chng ta c th nh ngh a l qu trnh

cc c nhn nhn bit c u im ca cng vic ang lm nhng th xc nh theo

m t cach ng thun va soan thanh lu t l rng thoa thun bng m t h p ng .Ngcli chng ta tha hip gia ci chng ta mun lm v ci ngi khc mun lm . M c


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d n rng buc t do ca chng ta , nhng chu ng ta vn th ng tham gia vao nh m t

tha thun bi v cc u im vt tri cc nhc im .

Cc bc thc t sau y nn c thc hin co kt qua mong mun:

Chn cc ng dng mc tiu

Li t k cac ch c nng cn thit cho t ng ng dung Chia nho cac ch c nng thanh cac thanh phn co ph c giam xung u c th nhn dng trong cc ng dng khc

Nhn dang cac thanh phn chung trong hthng quan tm Kim tra cac cng cu nay co th c s dung lp rap cac h thng muc

tiu va cung cp cac ch c nng mong mun .

1.4.1. Cc tiu chun m thanh/hnh nh s v cng nghip a phng tinCc dch v nghe nhn cung cp truyn thng thi gian thc ca m thanh cng

v i thng tin hnh anh gi a hai hoc nhiu khach hang cui . Thng tin nhn la cac anhchuyn ng thng h ng , nhng co th la anh tnh , hoa ho c dang bt ky khac .

ITU-T SG15 a tiu chun hoa cac h thng truyn thng nghe nhn trong nhiu mi

tr ng mang khac nhau.

B tiu chun u tin la cac khuyn nghicu a ITU -T a c thit l p chnh thc

vo thng 12/1990 cho ISDN bng he p:

Knh B: 64kbps Knh H0: 384 kbps V knh H11/H12: 1536/1920kbpsKhuyn nghiH.320 m ta toam b h thng va quy i nh m t s khuyn nghikhac

cho cac thanh phn tng ng cu a h thng cn tun thu nh:

M ha m thanh M ha hnh nh Ghp a phng tin iu khin h thngCc ng dng mc tiu chnh l hi ngh truyn hnh , in thoa i co hnh , sau o m rng an ninh va kt ni a im cho hthng ISDN bng he p a c nghin c u.

Song song v i hoa t ng tiu chun hoa nay , cc hot ng tiu chun ha mi

c bt u vao thang 7/1990 cho bng rng va cac h thng nghe nhn cht lng

cao. Cng vi c nghin c u a thanh cng v i khuyn nghiH .261. Nhm nghin cu

m i nay ban u co trach nhim v i ma hoa video cho ch chuyn giao ng b

(ATM) v hp tc v i ISO/IEC JTC/SC29/WG1 (MPEG).

Thnh cng ca MPEG da trn s ln g cac phn t ng th i . Quan trong nht

l c th nh thi im thit lp . MPEG a xut hin vao th i im khi cac thu t toanm thanh va hnh anh a a t t i tim cn , v kh nng ca x l tn hiu s a thoa


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mn ph c ta p cu a thu t toan . MPEG cung thanh cng trong gianh c cac thanh

vin tham gia la tt ca cac nha cng nghi p , nh ng ng i ang o i ho i h i tu .Nh s

quan tm cu a cac nha cng nghi p i v i MPEG trong cac ng dung m thanh va

hnh nh s, MPEG tham gia vao lp trnh din nghe nhn va hoan toan c l p v i lp

truyn tai . M t thanh phn cui cung thanh cng la cac b giai ma thay cho cach tipcn b ma hoa -b giai ma thng th ng. Do o , MPEG co th cung cp giai phap

chun cho nh ng ng i tham gia chnh , h xem xt vic s dng m ha m thanh

v hnh nh s cho cc sn phm ca th trng mi rng ln .

i vi cng nghip a phng tin c 2 t ch c tiu chun chnh la ITU va ISO .

Cc tiu chun m ha hnh nh hin nay a c 2 t ch c nay i nh ngha . Cc tiu

chun nay khac nhau chu yu tc bit theo cac ng dung . Tt ca cac tiu chun co

th c s dng ch yu cho cc ng dng c khong tc bit ln . Theo cac thu t

ton m ha, tt ca cac tiu chun u theo m t khung c s tng t nhau .

1.4.2. Cc tiu chun ca ITU-T cho ca c hth ng truyn thng nghe nhn.H thng PSTN a c m t nhom chuyn gia cu a nghin c u ma hoa tc bit

thp. H a ra khng ch khuyn ngh H .324 cho toan b h thng , m c khuyn

ngh m ha video H .263, khuyn nghima hoa m thanh G .723.1 v nh ngha

phng th c ghep knh trong khuyn nghiH .223. M t m hnh ngn xp giao th c

chung cu a cac thit biu cui nghe nhn theo Seri H c ch ra trong Hnh I-7.

Hnh I-7 Ngn xp giao th c chung cu a ca c thit bi u cu i nghe nhn

a/ Tiu chu n ITU-T H.320Theo tt ca cac tiu chun cu a ITU , lin kt theo tiu chun H .320 l bt buc .

Lin kt nay co c qua m t gateway . Trong m t s trng h p, gateway phai thchin cac giao di ch gi a cac giao th c bao hiu khac nhau , cc tiu chun nn khc


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nhau va cac phng th c ghep khac nhau .Nh ng bin i cu a bao hiu , nn v ghp

knh la do cac c im kh c nhau ca cc mng c s m mi tiu chun p dng .

Tiu chun H .320 i nh ngha m t may chu h i nghitrung tm go i la MCU (Khi iu

khin a im) cho phep nhiu cuc go i ng th i.

b/

Tiu chu n ITU-T H.310 v H.321Hai khuyn nghinay cho cac h thng nghe nhn trong mi tr ng ATM :

H.321-Thch ng cc thit b u cui in thoi c hnh H .320 v i mitr ng ISDN bng rng.

H.310-Cc h thng truyn thng nghe nhn bng rng .c/ Tiu chu n ITU-T H.322Khuyn nghinay bao trum lp t cac mang LAn va cac thit bih i nghiin

thoi c hnh v thit b hi ngh truyn hnh , tng ng nh khuyn nghiH .320

cho NISDN.

d/ Tiu chu n ITU-T H.323 Standard.Khuyn nghina y xac i nh thit biva cac h thng cho in thoa i c hnh trn

mng LANc QoS khng c m bo.

Cc xem xt thit k trong pht trin ca H.323 nh sau:

Lin kt, c bi t v i NISDN va H.320 iu khin truy c p LAN t rnh tc ngn Cc m hnh a cuc gi Kh nng m rng t cc mng nh ti cc mng c kch thc trung bnh

1.4.3. Cc tiu chun m ha hnh nhC 2 cch tip cn hiu cc tiu chun m ha hnh nh (H.261, H.263 v

H.26L)

M t cach tip cn la t p trung vao cu tru c dong bit va cn nm c milp cu tru c biu din cai g va mi bit trong dong bit ch thicai g . Cch tip

cn nay rt quan trong i v i cac nha san xut v cc sn phm ca h phi

tun thu tiu chun. Cch tip cn khc l tp trung vo cc thut ton m ha c th s dng to ra cc dng bit tun th tiu chun v cn nm c thnh phn no khng

xc nh cc th u t toan ma hoa . Cch tip cn ny cung cp hiu bit su hn

v cac ky thu t ma hoa hnh anh .

a/ Tiu chu n ITU-T H.261Tiu chun nay i nh ngha cac ng dung h i nghitruyn hnh va in thoa i co

hnh. H.261 nhn manh c c tc bt thp v tr m ha thp . Thu t toan ma hoa s

dng trong H .261 c ban la m t lai ghep cu a bu chuyn ng loa i bo cac d th a


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tm thi v chuyn i m ha gim d tha khong trng . Do o H .261 c nh

h ng rt quan trong t i cac tiu chun ma hoa ang co va ang phat trin .

b/ Tiu chu n ITU-T H.263Trong sut qua trnh phat trin cu a H.263:

Mc tiu ngn han l m rng H.261 s dng khung chung

Mc tiu di hnl thit k mt tiu chun m ha hnh nh c th khc cbn vi H.261 c c hiu qu m ha cao hn .

V cc hot ng tiu chun ha din ra rt di , nh ng n lc ngn han tao ra

H.263 v H .263 version 2, trong khi n lc dai han c xem nh la H .26L/H.264.

Thc cht H .263 kt h p cac yu t cu a H .261 cng vi MPEG v c ti u cc

tc bt rt thp.

Thc t, H.263 cung cp hiu qua ma hoa cao hn so v i H .261 ttc cc tc

bit. V H.263 a c xy dng trn H .261 nn cu tru c chnh cu a 2 tiu chun thccht tng t nhau. Cc khc bit chnh bao gm:

H.263 h tr nhiu khun dang anh hn H.263 s dung bu chuyn ng n a im nh (half-pel), nhng khng s dung

lc nh trong H.261.

H.263 s dung 3D VLC cho hs ma hoa DCT ngoai thu t toan ma hoa cbn, 4 la chon trong H .263 l m phn gia b m ha v gii m cung

cp cht lng cao hn.

H.263 cho phep kch th c b c lng t thay i mi khi l n(Macroblock-MB) v i tiu nho .

M t khac bi t chnh gi a H.261 v H.263 l d bo na im nh trong b chuyn

ng. Khi nim ny cng c s dng trong MPEG.

c/ Tiu chu n H.264/AVCMc du H.264 c da trn khung c s chuyn i d bao bu chuyn ng theo

khi thng th ng trong H .261, H.262, H.263, nhng nh ng thay i quan trong nh

lc vng , chuyn i nguyn (4x4) v chuyn i ngc , d bao khng gian h ngcho d bao bu chuyn ng anh tham chiu m ha trong anh , nhiu anh (ln t i 5),

m ha di thay i

H.264 c h ng t i m t dai rng tc bt rng (64kbps n 240Mbps), di

rng cc mc cht lng v cc phn gii theo thi gian thc , tr end-to-end thp

cho nhiu dang ngun khac nhau. Tiu chun nay co th c ap dung cho dong video ,

truyn hnh quang ba , cc dch v i thoi Tt c cc y u t ny v li m ha

l chi ph ca phc tp ngy cng tng . Trong khi ma hoa chnh (dng bit c m

ha thc s ) a c tiu chun hoa , cc phn khc nh cc dng bit tun th ,phn


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mm tham chiu , khun dang 4:4:4, su bit tng c ng (ln t i 12bpp), kim tra ,

giy phep s h u ang c phat trin nh ng giai oan khac nhau .

1.4.4. Cc tiu chun m ha m thanh ITU a tiu chun hoa 3 b ma hoa 3 tiu chun m thanh c th p d ng cho

truyn thng a phng tin tc thp . Khuyn nghiG .729 8 kbps CD-ACELP co tr b codec thu t toan 15ms va

cung cap m thanh cht lng mang . Bma hoa nay c thits k cho cac

ng dng v tuyn nhng cng c th p dung cho truyn thng a phng

tin.

Khuyn nghiG .723.1:b ma hoa m thanh 6,3 v 5,3 kbps cho truyn thnga phng tin a c thit k cho in thoa i co hnh tc bit thp . Kch

th c khung 30ms va tr codec thu t t on 1 chiu 37,5ms cho phep giam tc

bit so v i G.729.1.4.5. Cc tiu chun ng b v ghp a phng tin

Cc dng s cp theo khuyn ngh ITU -T H.222 nh m thanh , hnh nh, d liu,

iu khin ng b khung hnh anh va cac t n hiu ch thi , mi loa i co th c tiu

chun hoa quc t ho c tiu chun ring . Cc dng s cp ny c ghp thnh mt

dng gi ni tip theo cc chc nng ca H .222.0, H.222.1/H.222.1. Cc chc nng

ny bao gm khi p hc c s thi gian ghp , ng b thit bi , loi b dch (tr t),

qun l b m , an ninh va iu khin truy c p , bo hiu knh con v cc ch

trick (mo) l cc c ch h tr ch c nng iu khin tng t ghi hnh . Khuyn

ngh H.222.1 xc nh cc phn t v cc th tc t H .222.0 s dng chng trong

cc mi trng ATM v cng xc nh cc im m v th tc cheo cc dng s cp

theo i nh ngha cu a ITU -T. H.222.1 cho phep s d ng c hai dng chng trnh

H.222.0 v dng truyn ti H .222.

a/ Khuyn nghiH.221 ca ITU-TKhuyn nghinay quy i nh cu tru c khung knh 64-1920kbps trong cac di ch vu

nghe nhn. H.221 l giao thc ghp v ni cho cc thit b u cui H.320. C th ghpt i 30 knh B tao thanh m t siu knh v i tc bit la nx 64 kbps. Cc knh thng

tin cho thng tin m thanh va hnh anh khng thc hin iu khin li m da hoan

ton vo kh nng sa li ca m ha thng tin .

b/ Khuyn nghiITU-T H.223.Khuyn nghinay quy i nh giao th c ghep dung cho truyn thng a phng tin

tc bit thp . C th s dng 3 kiulp thch ng (AL), cc lp khc nhau tnh cht

xc sut li v tr. AL1 v AL2phc v cc nhim v khc nhau cn AL 3 c thit

k s dung ma hoa video.


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c/ Khuyn nghiITU-T H.225.Khuyn nghiH .225.0 m ta cac phng tin kt h p , m ha v ng gi m

thanh, hnh nh , d liu v iu khin truyn ti gia cc thit b u cui H .323

trn cac LAN khng am bao QoS , ho c gia cac thit biu cui H .323 v cc

gateways H.323. Cc gateway H .323 c th kt ni ti cc thit b u cui H .320,H.324 ho c H .310/H.321 trn cac mang tng ng NISDN , PSTN ho c BISDN . Cu

hnh thit b u cui gateway ny v cc th tc c m t trong H .323 v H .225

bao trum cac giao th c va khun dang ban tin . Phm vi ca truyn thng H .225 l gia

cc thit b u cui H .323 v cc gateway H .323 trn cung LAN bng cung giao th c

truyn tai.

d/ Giao th c iu khin chung H.245.Khuyn nghinay i nh ngha cac ban tin va cac thu tuc trao i thng tin iu

khin gi a cac thit biu cui a phng tin . H.245 xc nh bo hiu thit b ucui-t i-thit biu cui xac i nh cac kha nng ma hoa va giai ma cu a thit biu

cui xa sau khi thit l p kt ni mang va iu phi n nh v gii phng cc ti

nguyn thit biu cui qua cuc go i .

H.245 a c i nh ngha nh la cac khuyn nghichung phu h p v i s dung cho

m t dai cac ng dung thit biu cui a phng tin . H.245 a c cu tru c bng 3

phn chnh : c php , ng ngha va cac thu tuc (syntax, semantics, and procedures ).

Tng tac gi a cac thc th giao th c khac nhau ch qua truyn thng v i ng i s

dng H.245. H.245 cung cp nhiu dch v khc nhau cho ngi s dng H .245. M t

s di ch vu la trao i kha nng , cc th tc bo hiu knh logic , cc tn hiu iu

khin va ch thi .

1.4.6. Cc tiu chun MPEG trong truyn thng a phng tinS thanh cng cu a MPEG da trn nhiu thanh phn ng th i . Quan trong nht la

th i im ma MPEG a c thit l p . V tn go i MPEG a xut hin vao th i im

khi cac thu t toan ma hoa m thanh va hnh anh a a t t i cht lng tim cn . MPEG

cng thnh cng trong quy nh s tham gia cu a t t ca cac nganh cng nghi p (cxu h ng h i tu trong cac ng dung m thanh va hnh anh ). MPEG a ong gop vao

s chp thun thc t cu a lp biu din nghe nhn , lp ny c lp vi hthng vn

chuyn. Thnh phn thnh cng cui cng tp trung trn cc b gii m thay cho cch

tip cn b ma hoa -b giai ma truyn thng . Do o MPEG co th cung cp giai phap

tiu chun cho nhng ng i chi-l nhng ngi ang cn nhc s dng m ha s

cho m thanh va hnh anh cho cac san phm i m i co thi phn l n , ng th i MPEG

c th cho php t c nhanh hn l khng c n .

Mi m t tiu chun MPEG bt u bng nhn dng phm vi v pht hnh mtM i tham gia xut (Call for Proposals), sau o i vao 2 giai oan chnh:


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Giai oan th nht la giai oan canh tranh lin quan t i kim th va anh giacc xut sng gi chn ra mt vi xut cao nht , sau o cac thanh

phn cu a xut nay la c s bt u cu a giai oan 2

Giai oan 2 gm phat trin h p tac cac thanh phn (giai oan 1) qua qua trnhsng lc tng tc ca m hnh th nghim (m ta ma hoa ). Khun dang cu ad liu biu din c xem nh cu tru c va co th da vao xy dng cac

dng khc nhau ca cc dng d liu (dng bit) h p l . Cc quy tc dch d

liu (dng bit) c go i l qu trnh gii m . Khi a ra nen d liu m thanh

v/ho c hnh anh , m t b ma hoa phai tun theo m t qua trnh cac b c tun

t go i la qua trnh ma hoa . Tuy nhin qua trnh ma hoa nay khng c tiu

chun hoa va thay i v cac b ma hoa co ph c ta p khac nhau co th c

s dung cho cac ng dung khac nhau . Ch c rng buc l u ra ca qu trnh

m ha l dng bit ra chun v cu trc c th dch c theo ng ngh agii m ca cc cc b gii m tun th tiu chun .

a/ Tiu chu n MPEG-1MPEG-1 l tiu chun lu tr v khi phc cc nahr ng v m thanh trong mi

tr ng lu tr s . i nh h ng ban u cho tiu chun MPEG -1 l m thanh v h nh

nh c cht lng tt khong 1,4Mbps cho ng dung a CD . Cc yu cu c bn

bao gm:

M ha hnh nh vi cht lng tt 1 n 1,5 Mbps va m thanh v i chtlng tt 128-256 kbps

Truy c p ngu nhin t i m t khung trong th i gian han ch Kh nng chuyn tip nhanh v o li nhanh , cho phep tm kim va xem xui

ngc m t s ln v i tc thng th ng

M t h thng chi la i (playback) c ng b va truy c p t i d liu nghenhn

Bn canh cac yu cu co tr c , s lng cac yu cu khac cung tng ln nh h

tr nhiu phn giai anh , s v ng chc i v i li , cn bng cht lng ma hoa v itr ma hoa (t 150ms n 1s), v kh nng ca cc b m ha thi gian thc vi chi

ph hp l. Tiu chun MPEG-1bao gm cac phn sau : Hthng, hnh nh, m thanh,

tun thu va phn mm.

Phn m thanh cu a tiu chun MPEG -1 a tr thanh thanh phn chnh cho phat

thanh quang b lp 2 m thanh MPEG 1 v i cht lng CD . Lp III a tr thanh

khun mu tiu chun cho phn phi m nhac trn veb . Tiu chun MPEG -1 y u

(Cc h thng m thanh -hnh nh) l khun dng tiu chun cho phn phi cc chi tit

hnh nh chuyn ng qua Web.


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MPEG-1 a cung cp c h i v ng chc u tin cho cng nghi p vi in t u

t vao cng nghhnh anh s . Hin nay cac chip giai ma MPEG -1 c san xut t

nhiu ngun , m t s trong o kt h p v i cac nha in t oc cac bit t CD . Cc

thit biva s lng ngay cang tng cu a cac may tnh ca nhn ang tao ra cac iu kin

ph bin sn xut ni dung a phng tin .b/ Tiu chu n MPEG-2Tiu chun MPEG -2 c thit k cung cp kh nng nn , m ha v pht

cht lng cao ,pht cc tn hiu a phng tin a knh qua qung b mt t ,phn

phi qua vtinh va cac mang bng rng . Tiu chun MPEG -2 xc nh cc yu cu

i v i ma hoa hnh anh , m ha m thanh v m ha cc h thng tng hp m

thanh va hnh anh a ma hoa thanh cac dong d liu ring do ng i s dung i nh

ngha, kim tra tun thu kim tra cac dong bit va b gia i ma o co thoa man cac yu

cu hay khng va m phong phn mm cho ma hoa va giai ma ca hai chng trnh vadng truyn ti. L mt tiu chun truyn dn , MPEG-2 h tr nhiu dang khun dang

gi khc nhau bao gm cc g i l n co dai thay i t 1 n 64 kbp. ng thi

MPEG-2 cng cung cp kh nng sa li ph hp vi truyn dn qua TV cp v cc

knh vtinh. Tiu chun MPEG-2bao gm cac phn sau:

Cc h thng, hnh nh, m thanh Tun th,phn mm, Thit bi , lnh va iu khin lu tr s (DSM-CC) M ha n thanh tin tin (AAC), hnh nh 10 bit, giao din th i gian thc, Tun thu cu a DSM-CC

c/ Tiu chu n MPEG-4MPEG-4 l tiu chun cho cc ng dng a phng t in. Tiu chun nay h ng

t i video cho Internet va Intranet , video v tuyn , mua ban tng tac , th in t hnh

nh v ph im anh nha , cc tr chi , m phong va hun luyn cac c s i tng

thng tin. V cc vng ng dn g nay co m t s yu cu chnh da trn s h tr cu a

cc tiu chun trc y, nn MPEG-4 xc nh cc chc nng sau : Tng tac da trn n i dung Kh nng truy cp ton cu Ci thin nnTiu chun MPEG -4 bao gm cac phn sa u: Cc h thng , m thanh , hnh nh ,

tun thu ,phn mm va khung c s vn chuyn a phng tin .

Kin tru c khai nim cu a MPEG -4bao gm 3 lp: lp nen, lp ng b va lp vn

chuyn:

Lp nen la hiu thng tin va khng hiu vn chuyn Lp ng b la khng hiu thng tin va khng hiu vn chuyn


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Lp vn chuyn khng hiu thng tin va hiu vn chuyn Thit k cu a MPEG -4 c t p trung quanh m t khi n i dung c s go i la i

tng nghe nhn (AVO). Mi AVO c biu din tach ring va tr thanh c s cho

m t dong c l p.

d/

Tiu chu n MPEG-7MPEG-7 l tiu chun biu din ni dung cho tm kim , lc, qun l v x l

thng tin a phng tin . M t muc tiu cu a MPEG -7 l cho php tm kim a

phng tin trn Internet va nng cao trang thai hin ta i bng cac giai phep h p ly la

tiu chun hoa m t giao din cho cac b m ta va cac phng th c m ta -cc phng

th c nay kt h p v i n i dung thoa ma tm kim nhanh va hiu qua .Nh vy n i

dung nghe nhn v i metadata MPEG -7 c th d dng c nh ch s v d dng

c tm kim . MPEG-7 h ng t i xac i nh khng ch tm n i dung quan tm trong

cc ng dng ko (pull application) nh la khi phuc c s d liu ma ca trong cacng dng y (push applications) nh la chon va loc trch n i dung quan tm tr0ong

cc knh qung b .Ng i ta ky vong MPEG-7 s lm vic khng ch v i cac n i dung

m ha theo MPEG m c cc ni dung c m ha khng phi MPEG .

S lng l n cu a cac vung ng dung truyn thng cung nh ang n i ln khai thac

tm kim v khi phc m MPEG -7 c th p dng l:

Cc s kin quan trng-Lch s, chnh tr Gio dc-khoa hoc, y t va i a ly Thng ma i-t ai, ti chnh, kin tru c X hi v gii tr-dch v hng ngy, cc tr chi tng tc Th i gian ri-Th thao, mua sm, du li ch Lu tphp-thm tra t i pham va(tm kim ) cc c nhnmt tchB m ta MPEG -7 m ta cac dang thng tin a phng tin khac nhau . S m ta

ny s c kt hp vi ni dung ca n cho php tm kim cc chi tit nhanh hn

v hiu qu . Chi tit nghe nhn co d liu MPEG -7 lin quan t i no co th c anh

ch s v tm kim . Chi tit nay nay co th bao gm cac anh tnh , cc ha , cc mhnh 3D, m thanh , ging ni, hnh nh v thng ti n v cac phn t nay c kt h p

nh th nao trong m t trnh din a phng tin . Cc trng hp c bit ca cc cc

kiu d liu chung co th bao gm ca m ta khun m t va cac c im cu a ng i .

Mc du MPEG -7 khng tiu chun hoa vi c trch thuc tnh nhng s m ta

MPEG-7 c da trn u ra cu a qua trnh trch thuc tnh va m c du MPEG -7

khng tiu chun hoa search engine nhng m ta kt qua c search engine s dung .

e/ Khung c s aphng tin MPEG-21Cc mc tiu ca MPEG-21 nh sau;


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Phi hiu c nu cc thnh phn khc nhau ph hp vi nhau v ph hpnh th nao

Phi bn lun cn thit cc tiu chun mi no , nu cac khoang trng trong ha tngcn tn ti v khi hai im trn tin ti c

Phi thc hin lin kt cc tiu chu

n khac nhauD an MPEG-21 a bt u v i muc tiu cho phep s dung trong sut va s dung

tng them cac ngun a phng tin qua nhiu mng v thit b .Nghin c u a thc

hin uwocj nhn dang m t s cng nghcn thit a t c muc tiu MPEG -21,

bao gm:

Khai bao hang muc s Biu din n i dung -d liu c biu din nh th nao v i cac thit bik hc

nhau

Qun l v s dng ni dung -ci ddawtj cc giao din , giao th c cho phep taora, thao tac, tm kim, truy c p , lu tr , vn chuyn va s dung (s dung la i )

n i dung

Qun l v bo v s hu tr tu -phng tincho phep n i dung c quan ly ,bo v lin tc v tin cy qua cc mng v dch v khc nhau .

Cc thit b u cui v mng -kh nng cung cp truy cp lin kt v trongsut t i n i dung qua cac mang va cai t thit b u cui.

Bo co s kin -cc n v v cc giao din cho php ngi s dugnj hiuchnh xc hot ng ca tt c cc s kin bo co trong khung c s.

f/ Cc tiu chun m ha nh tnh Cng vi vic s dng ng y cang tng cac h thng truyn thng a phng tin ,

nn nh yu cu cht lng ngy cng cao hn v yu cu nhiu thuc tnh mi .Nn

nh khng ch phi gim c yu cu lu tr v bng thng , m cn phi cho php

trch son tho , x ly va h ng t i cac thit bi v ng dng c th . Cc tiu chun

sau y a c quan tm nghin c u la MPEG -4 VTC, JPEG, JPEG-LS, PNG,

JPEG2000.1.5. Kt lun

Chng I trnh bay tng quan cac vn lin quan t i truyn thng a phng

tin, s h i tu cu a vin thng va quang ba la ng lc cho s phat trin truyn thng

a phng tin . Vai tro cu a cac t ch c tiu chuan quc t trong cac lnh vc khac

nhau cu a truyn thng a phng tin cung c c p.


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CHNG IIKHUNG C S TIU CHU N HO A MULTIMEDIA

S tiu chun hoa toan cu ang ngay cang tr nn quan trong hn trong a t c

m t ha tng thng tin toan cu (GII). Cc t chc tiu chun ha vin thng v thng

tin nh ITU va ISO/IEC, mi t ch c a thanh l p cac nhom c bi t t p trung vaoxc nh cc tiu chun cho GII . Chng nay tm kim cac hoa t ng cu a cac t ch c

lin quan t i GII . ng thi tng kt li hi n trng ca cc tiu chun truyn thng a

phng tin.Nh ng thanh t chnh h ng t i trin khai GII c m ta . IETF la m t

t ch c tiu chun t p trung vao phat trin cac giao th c s dung trn mang IP . IETF

bao gm nhi u nhom nghin c u va c quan ly b i nhom Internet Engineering

Steering Group, Internet Architecture Board , v Internet Society . N i dung chng

cng cp ti qu trnh tiu chun ha ca ETSI i vi ng dng , phn sun va

mng.

Ngoi cc t chc tiu chun ny , cc din n cng nghip tham gia vao nghin

c u xy dng tiu chun bao gm:

Telecommunication Information Network Architecture (TINA), International Multimedia Telecommunications Consortium (IMTC), MPEG-4 Industry Forum (M4IF), Internet Streaming Media Alliance (ISMA), Third Generation Part- nership Project (3GPP/3GPP2), Digital Video Broadcasting (DVB), Digital Audio

2.1. Gi i thiuNhiu nm v trc, chun ha trong vin thng l lnh vc hot ng ca cc t

chc chun ha nh lin minh vin thng quc t (ITU), t chc chun ha quc t

(ISO), y ban k thut in quc t (IEC), y ban k thut lin hp 1(JTC1). By gi,

cc hot ng ny cng ang c trin khai bi cc hi ng(nhm) chun ha khu

vc nh vin cc tiu chun vin thng Chu u (ETSI), y ban T1, y ban cng nghvin thng (TTC). S phi hp gia cc nhm ny rt quan trng m bo rng cc

ngun ti nguyn khng lng ph trong vic t c mc ch cui cng l cc tiu

chun ton cu.

Nm 1989, cc hot ng phi hp ny c bt u vi s thnh lp ca hi cc

chun vin thng quc t(ITSC). Nm 1994, ITSC c t chc li thnh nhm phi

hp cc tiu chun ton cu (GSC) v tip tc cc cng vic ca mnh. Trong cc lnh

vc c quan tm nhiu nh phng thc truyn ti khng ng b (ATM) v a

phng tin, cc din n v cc t chc c thnh lp v nhanh chng t c

nhng thnh tu trong cc mc tiu ca mnh. Do , cc t chc chun ha quc t


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ang kin thit li chnh mnh c th m nhn nhng cng vic mt cch nhanh

chng.

T do trong vin thng m ra mt th trng cnh tranh trong v ngoi nc

trong nhng nm gia 1980 M, Chu u, v Chu , cng vi cc k thut tin tin

trong truyn thng s, thng tin di ng v cc h thng nh v ton cu lm thayi nn kinh t x hi v cc mi trng k thut. Cc k thut v nn cng nghip vin

thng, thng tin, gii tr, in t dn dng ang hi t thng qua s ha v mang n

cc ng dng a phng tin trong cc lnh vc ny. Trong cc mi trng mi nh

vy th cc chun ang c pht trin bi cc t chc v cc nhm tr nn ngy cng

quan trng. Thng thng cc chun cng nghip c pht trin rt nhp nhng. Cc

t chc chun ha nh ITU-T, ISO/IEC, v JTC1 i hi phi hot ng nhanh hn.

C s h tng thng tin ton cu(GII) l im mu cht trong hi t cng ngh v

cc ngnh cng nghip, v s cung cp a dng cc dch v a phng tin. Lin ktv hp tc ton cu l mt trong nhng tiu ch chnh ca GII v i hi cc chun

ton cu. Nm 1994, ETSI, y ban T1 v TTC ca Nht Bn thnh lp mt y ban

c bit cho vic nghin cu cc kha cnh ca cc chun v truyn thng a phng

tin v GII. Nm 1995, ITU-T to ra nhm cc bo co vin lin on trong GII(JRG-

GII). Nm 1996, ISO/IEC, JTC1 to lp mt nhm hot ng c bit trong GII

(SWG-GII). Cng v l m c nhiu nhng hot ng chung lin quan ti cc

chun GII cho vic xc lp nhng vn bao trm v thit lp mi quan h hi ha

gia cc t chc cho chun quc t, vng v khu vc.

Truyn thng a phng tin bao gm nhiu cc cng ngh vin thng, x l

thng tin, v pht thanh. Cng ngh thng tin gii quyt cc qu trnh nh tng hp,

vn chuyn, thu hi, lu tr, trnh by v bin i tn hiu thnh nhiu dng. Trong

nhng dng ny bao gm thoi, ting ni, video, ha, vn bn, hnh nh, d liu v

s kt hp gia chng, trong khi nhng ngi s dng u cui ti pha thu c th l

ngi s dng, my mc hoc kt hp c hai. V th chun ha vin thng v IT cn

phi c m rng xa hn trong tng lai v nhng mi quan tm n vn qun l.Nhng ngi sn xut c gng cn bng vi nhng chun cn thit bo v th

trng ca h. Cc nh cung cp dch v cng c gng gim gi thnh sn phm

chun ha. Trong nhng g sau y chng ta s c gng bao qut nhng kha cnh k

thut v kinh t x hi ca nhng chun v vic qun l cc chun. Chng ta cng s

miu t nhng quan im v nhng im ni bt trong qu trnh a ra cc chun, lm

cho chng tng thch, r rng

2.2. Cc hot ng tiu chun ha.Cc chun nhm duy tr nhng tng thch trong mi trng a phng tin ngy

cng phc tp. Thnh cng trong vic chun ha i hi s hiu bit v mi trng


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trong n c tin hnh. S pht trin ca cc h thng thng tin nh in thoi di

ng, internet, multimedia.. i hi nhng hp ng c bit gia cc bn lin quan:

nh sn xut thit b, vn hnh mng, nh cung cp dch v, ngi s dng u cui.

Nhiu cc h thng mi hng ti s hp nht cc phn t t cc cng ngh vin

thng, x l thng tin v cng ngh pht thanh. Ngy nay, i a s cc chun clm trong, thi thong lm trc qu trnh thit k sn phm. Kt qu l khng nhng

c nhiu k thut cn thit m thi gian hon thnh mi sn phm cng nhanh hn.

iu ny trc tin lm gia tng cc nhm chun khu vc v quc gia, sau lm tng

s lng cc congxoocxiom. Tuy nhin, chun ha i hi thi gian v nhng ti

nguyn hiu nhng ci g thc s cn c chun ha v lm th no thnh tu

t c phi hi ha gia cc quyn li i lp. S thnh cng trong vic truyn ti

kin thc t nghin cu cho n qu trnh ng dng vo thc hnh lun lun i hi

nhng cuc th nghim. Nu chun ni n cc khi nim mi, th cn phi b i cckha cnh khng r rng lc u.

Nhng nhn t chin lc l nhng l do yu cu mt chun, giao din c

chun ha, v thi gian tiu chun ha. Mt khc, vic xem xt cc chin thut lin

quan ti nhng cu hi sau: chun ha s din ra nh th no? Ai s ch o hot ng

chun ha? V cc chun s c s dng u.

2.2.1. Nhng l do tm kim m t tiu chun .Chun ha l mt quyt nh kh khn. Trong trng hp nhng cngngh

c xem xt cn thn, mt t chc thng mi s chp nhn v s dng cc chun

nu chng gip h m rng th trng. Tuy nhin chun ha cng l cch gip

cc t chc mi trong th trng gm nhng cng ty c u th vt tri hn. Chun

hacng gip hp php ha cc cng ngh mi v cho php cc t chc s dng cc

cng ngh ny chim c v tr trung tm. V pha ngi dung, cc chun m

tnh sn c ca ca mt thit b, thnh phn t mt vi ngun, c bit l chng cho

php ta s dng ln cc sn phm t nhiu nh cung cp.

Quyt nh khng chun ha cng cha 2 n . Nhng nh sn xut c l munmnh l ngi duy nht iu khin c thitrng . S khn cp tiu chun ha

ngh rng nhng sn phm v nhng ngi tiu dng theo ui s n nh sut thi k

di. V d, th trng ton cu cho nhng th thng minh trong thng mi in t i

hi mt chui cc chun cho cc h thng vn hnh, nhu cu, cc giao din..

khuyn khch s pht trin ca cc ng dng.

2.2.2. Nhng giao din c tiu chun ha.Hnh II-1 minh ha nhng giao din c t chc trong tng lp khun dng.

Chng gm cc chun cho tham chiu, tng ng, tng thch v linh hot. Thmvo , nhng chun cho thi hnh v cht lng c th tt c cc tng.


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Nhng chun tham chiu cung cp cc thit b o lng m t nhng thc th

thng thng bng nhng b tham chiu. V d in hnh l nhng chun n v cho

cc n v o lng vt l (Ohm, volt, watt, dBm). V d khc trong lnh vccng

ngh thng tin v vin thng l b k t ASCII tiu chun ha cc ngn ng my bc

cao, m hnh kt ni cc h thng m, v k hoch a ch ha cho cc dch v thoiv internet quc t.

Nhng chun tng ng vch r nhng kha cnh phi ng nht c hai pha

ca ng truyn tin cng nh nhng s thay i hoc dung sai cho php nu c. S

tng ng cn thit thit lp thnh cng kt ni. Nhng v d gm c nhng tiu

chun thng thng ca cc mc tn hiu, hnh dng nhng xung hin ti, thut ton

m ha ngun cho ting ni v video tng tc, thut ton mt m v cc h thng vn

hnh my tnh.

Nhng chun tng thch phi hp cc lung sinh ra bn truyn v bn nhn pha cui bn kia. Nhng chun ny c lin quan ti cc cu hnh, cc chun chc

nng, cc mu giao din, cc hp ng ngi s dng. Cc cu hnh, chun chc nng,

cc mu giao din xc nh mt tp hp cc la chn c nh thi hnh cc dch v

c a ra. V d nh nhng chun kin trc ch ra nhng cch sp xp c th ca

cc thnh phn v nhng khi kin trc thc hin mt chc nng c bit cc bn

lin quan. Mt v d khc bao gm cc giao thc giao din xc nh cc khi chung

ca bn pht v bn thu phi m bo s thnh cng trong giao tip mc d c hai bn

khng phi ng nht.

Hnh II-1 Cc tiu chun k thut vi kin trc phn lp


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Nhng tiu chun linh hot ch trng vo s tng thch cc tnh hn tp, kh

nng ca mt bn n so vi cc nhm khc vi nhng h thng khc nhau, v chiu

hng ln xung ca n. V d nh m phn gia cc nh sn xut s dng khuyn

ngh ca ITU-T v modem cho php s thay i ca d liu ngi dng vi nhng

modem trc thng qua nhng quy tc chung.2.2.3. Thi gian tiu chun haC hai kiu cho vic nh thi cc chun: mt kiu m t v mt kiu d on.

a/ Kiu m tKiu m ta miu t mi quan h v thi gian gia chun v chu k sn xut sn

phm. N gip chng ta hiu mi quan h hu nghim ca chun ti s pht trin th

trng, nhng khng hng dn trong vic a ra cc kt lun v nh thi hoc trnh

by t m v s chun ha. V tr ca chun trong chu k sn phm c ch ra Hnh

II-2. i vi sn phm ca chu trnh dch v cuc sng, cc chun c th l chunon trc, hoc p ng. Cc chun on trc l nhng chun cn thit cho s cng

nhn rng ri mt thit b hoc dch v. Chng rt quan trng lin kt cc h thng

thng tin, v iu ny gii thch v sao li c nhiu cc chun d on trc(V.32

mode, giao din gi X.25, ISDN, TCP/IP, Recomm. H.323 cho thit b u cui a

phng tin, tng bo mt cho thng mi in t-SSL).

Hnh II-2 V tr tiu chun trong chu ky sa n phm

Cc chun d on trc phi c phm vi v ch th rnh mch v a ra mt tp

nhng kha cnh kich thch th trng. Cc chun participatory theo ui tng bc

vi nhng s b sung kim tra nhng c im k thut trc khi lm theo chng.

Mt vi chun participatory l thut ton m ha thoi v ting ni trong cc khuyn

ngh ca ITU-T G.726, G.724, G.728 v G.729. Cc ng dng khc nhau ca internet

trn tng TCP c th cng c xem nh l cc chun participatory( MBONE,MMUSIC).


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Cc chun p ng h thng ha cc sn phm hoc dch v c bn, hoc

vch r cht lng mong i ca mt dch v. Cc chun ny a ra mt cch c h

thng thng tin khoa hc v d liu sn c bn trong cc sn phm k thut hu dng.

Kiu d on lm cho ph hp thi gian ca cc chun vi nhng kh nng thc

cht bn trong cng ngh s dng cng ngh ng cong hnh S. nh thi gian cacc chun trong mi quan h vi cng ngh ng cong hnh S c m t Hnh II-3

di y:

Hnh II-3 i nh th i gian cu a ca c tiu chu n lin quan t i ng cong S cng ngh

Trc tung i din cho vic thc hin cng ngh. nh thi cho cc chun on

trc phn gii thiu cng ngh. Cc chun participatory c sinh ra trong khi vic

thi hnh nhng ci mi pht trin theo hm m v cc sn phm ban u c

thng mi ha. Cc chun participatory cng ch vo trng thi ca cc h thng

ng dng m bo mt s pht trin linh hot ti mt trng thi mi ca qu trnh

hot ng. Mt chun p ng lin quan ti s biu l ca cng ngh trong h thngdch v: mt tp hp cc h thng cng ng

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