DATN (MobileTV)

7/23/2019 DATN (MobileTV)

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n tt nghip Nghin cu cc cng ngh truyn hnh di ng c bn

SVTH : o Minh Tin 1 Lp KTTT&TTK48

MC LC

MC LC .................................................................................................. 1LI MU ............................................................................................. 5THUT NGV CHVIT TT ............................................................. 7DANH MC HNH V ..............................................................................10 DANH MC BNG BIU .........................................................................11CHNG 1 TNG QUAN V TRUYN HNH DI NG................. ........12

1.1 Khi nim v truyn hnh di ng........................................................12 1.2 Phng php thu pht tn hiu truyn hnh di ng ...............................121.3 Cc tiu chun i vi MobileTV........... ............... ............ ............... ...151.4 Ti nguyn pht trin truyn hnh di ng ............. ............... ............ ....151.5 Gii thiu cc cng ngh truyn hnh di ng ............... ............... .........16

1.5.1 MobileTV s dng cc mng t bo ............... ............... ............ ....161.5.2 MobileTV s dng truyn dn s mt t v v tinh ............. ..........18

1.5.2.1 Cng ngh qung b a phng tin s cho cc my cm tay

(DVB-H).........................................................................................18 1.5.2.2 Cng ngh qung b a phng tin s qua mt t (DMB-T)...181.5.2.3 Cng ngh qungb a phng tin s qua v tinh (DMB-S)....191.5.2.4 Cng ngh qung b s dch v tch hpmt t (ISDB-T) ....191.5.2.5 Cng ngh ch lin kt hng i a phng tin (MediaFLO) ...201.5.2.6 Cng ngh cc h thng truyn hnh tin tin ti my di ng cmtay (ATSCM/H) ...........................................................................201.5.2.7 Cc cng nghMobileTV khc ang trong giai on tiu chunha hoc c trin khai ............. ............... ............ ............... ............20

1.5.3 MobileTV s dng cng ngh v tuyn bng rng ............. .............211.5.3.1 MobileTV s dng cng ngh WiFi .............. ............... ...........211.5.3.2 MobileTV s dng cng ngh WiMAX...................................21

CHNG 2 CC CNG NGH TRUYN HNH DI NG C BN ...... ..232.1 Mobile TV s dng mng 3G..............................................................23


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2.1.1 Gii thiu ...................................................................................232.1.2 MobileTV s dng cc tiu chun 3GPP Dch v truyn ti dngchuyn mch gi (PSS) .............. ............... ............ ............... ............ ....242.1.3 Cng ngh MBMS ......................................................................27

2.1.3.1 Kin trc MBMS ..................................................................282.1.3.2 Cc ch ca MBMS ............. ............... ............ ............... ...292.1.3.3 Truy nhp ti cc dch v MBMS ............... ............... ........... ..30

2.1.4 Kin trc in hnh h thng Mobile TV qua mng 3G ............. ......352.2 MobileTV s dng cng ngh DVB-H.................................................36

2.2.1 Khi nim DVB-H ......................................................................362.2.2 Cu trc v hot ng ca h thng DVB-H ............ ............... .......372.2.3 Cc cng ngh ca DVB-H ..........................................................39

2.2.3.1 Thnh phn chc nng ca m hnh pht d liu DVB-IP .........392.2.3.2 Ct lt thi gian (Time Slicing) ............... ............... ............ ....402.2.3.3 Thi gian chuyn gia cc knh v cc bit bo hiu tham s my

pht (TPS).................... ............ ............... ............... ................. ........422.2.3.4 MPEFEC ..........................................................................42

2.2.4 Kin trc mng ...........................................................................442.2.5 Truyn dn DVB-H ............... ............... ............ ............... ............442.2.6 Mng my pht DVB-H .............. ............... ............ ............... .......462.2.7 u cui v cc thit b cm tay....................................................48

2.3 MobileTV s dng cng ngh T-DMB ................................................482.3.1 Gii thiu ...................................................................................482.3.2 M ha knh T-DMB............. ............... ............ ............... ............502.3.3 Ghp knh ............... ............... ............ ............... ............ .............512.3.4 iu ch v ghp xen tn s .........................................................52

2.3.5 Cc ch truyn ti ca DMB .............. ............... ............ ...........53


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2.4 Cng ngh MediaFLO........................................................................55 2.4.1 Gii thiu ...................................................................................552.4.2 Kin trc h thng FLO ...............................................................56

2.4.2.1 M t h thng......................................................................56 2.4.2.2 Phn pht ni dung................................................................57

2.4.3 Kin trc phn lp ca MediaFLO ............... ............... ............ ......582.4.3.1 Lp vt l.............................................................................582.4.3.2 Lp truyn ti .......................................................................60

CHNG 3 SO SNH, NH GI CC CNG NGH TRUYN HNH DI

NG ............... ............... ................. ............... ................. ............... .........61

3.1 Mu .............................................................................................613.2 So snh cc cng ngh MobileTV ............... ............... ............ .............62

3.2.1 Hiu qu s dng ph, s lng knh v tc d liu ...................623.2.2 So snh cc tham s truyn dn ....................................................643.2.3 So snh tham s mng my pht ............. ............... ............ ...........653.2.4 So snh s audio/video ............. ............... ............. .............. .....66

3.3 nh gi cc cng ngh......................................................................67 3.3.1 Cng ngh DVB-H .............. ............... ............ ............... ............ ..673.3.2 Cng ngh T-DMB......................................................................69 3.3.3 Cng ngh MediaFLO .................................................................703.3.4 Cng ngh 3G (MBMS) .............. ............... ............ ............... .......72

CHNG 4 XUT HNG LA CHN CNG NGH TRUYN HNHDI NG, KT LUN V HNG PHT TRIN ......... ............... ............74

4.1 xut hng la chn cng ngh v pht trin Mobile TV................. .744.1.1 Hng la chn MobileTV trn mng 3G......................................744.1.2 Hng la chn cng ngh DVB-H ..............................................754.1.3 Hng la chn cng ngh DMB v m hnh th nghim T-DMB ca

i truyn hnh Vit Nam ....................................................................79


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4.2 Kt lun v hng pht trin ti .............. ............... ............ .............834.2.1 Kt lun......................................................................................83 4.2.2 Hng pht trin .........................................................................85

LI CM N ... ............... ................. ............... .................... ............ ..........87TI LIU THAM KHO ...........................................................................88


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LI M U

Ngnh truyn hnh c vai tr to ln trong vic truyn ng li, ph bin cc

chtrng chnh sch ca ng v Nh nc, qung b cc thng tin v kinh t,

chnh tr, khoa hc gio dc, vn ha x hi v thng tin dch v cho mi tng lp

nhn dn trong x hi. Ngy nay vi s hi t v cng ngh, truyn hnh khng

ch dng li nh vy m ang dn tr thnh mt phng tin truyn thng i

chng quan trng trong cc x hi pht trin, dn tr thnh mt ngnh cng

nghip gii tr v dch v siu li nhun. c bit l i vi truyn hnh di ng

ang l mt trong nhng hng pht trin thu ht c s quan tm ca nhiu nc

trn th gii.

Dch v truyn hnh di ng l mt dch v hi t gia truyn hnh v di

ng, dch v ny mra nhiu c hi li nhun mi cho cc nh khai thc qung

b, khai thc di ng, cc nh cung cp ni dung v c nhng nh kinh doanh

thng mi in t. Tuy nhin vic la chn cng ngh truyn hnh di ng no

va ph hp vi nc ta va em li li nhun ng thi phc v khch hng

mt cch tt nht li l vn rt ln i vi cc nh khai thc dch v.

Thi gian gn y, bn cnh vic pht trin h thng truyn hnh s mt t,

tng cng ty VTC cng trin khai th nghim dch v truyn hnh di ng vi

thit b thu truyn hnh s bng cng ngh DVB-H c tch hp trn in thoi di

ng. Sra i mng di ng 3G tch hp h trtruyn hnh di ng ca cc nh

mng nh: Viettel, Mobifone, Vinaphone .... Cng ngh truyn hnh di ng T-

DMB ca Hn Quc ang c i truyn hnh Vit Nam pht th nghim v

MediaFLO ca Mcng c gii thiu vo Vit Nam. Vn t ra i vi

cc nh khai thc qung b v di ng l cng ngh no s l cng ngh hiu qu

v thnh cng vi dch v truyn hnh di ng.

ti "Nghin cu cc cng ngh truyn hnh di ng c bn" tp trung

vo nghin cu cc vn k thut, cng nghcng nh tim nng ng dng ca

4 cng ngh truyn hnh di ng c bn. T phn tch, so snh, nh gi, xut


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nhng khnng ng dng ca cc cng ngh ph hp vi tnh hnh nc ta.

Qu trnh nghin cu ti gm 4 phn chnh sau :

Chng I : Tng quan v truyn hnh di ng

Chng II : Cc cng ngh truyn hnh di ng c bn

Chng III: So snh, nh gi cc cng ngh truyn hnh di ng

Chng IV: xut hng la chn cng ngh truyn hnh di ng,

kt lun v hng pht trin ti

Em xin chn thnh cm n thy Nguyn Tin Hng trc tip hng

dn em trong qu trnh nghin cu n ny ! ng thi em cng xin chn

thnh cm n sgip ca cc thy c trong b mn, v em mong nhn c

nhng kin ng gp qu bu n trln hon thin hn !

H Ni, thng 05 nm 2012

o Minh Tin


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THUT NG V CH VIT TT

3GPPThird Generation PartnershipProject

Dn i tc th h th ba

3GPP2 Third Generation PartnershipProject 2 Dn 2 i tc th h th ba

AAC Advanced Audio Coding M ha m thanh tin tin

AMR Adaptive Multirate a tc thch nghi

ATM Asynchronous Transfer ModeCh truyn ti khng ng

b

ARQ Automatic Repeat Request Yu cu pht li tng

ATSCAdvanced Television SystemsCommittee Standard

Tiu chun y ban cc h thngtruyn hnh tin tin

AVI Audio Video Interleaved Ghp xen video audio

BCMCS Broadcast/Multicast Service Dch v broadcast/multicast

BM-SCBroadcast/Multicast ServiceCenter

Trung tm dch vbroadcast/multicast

BSC Base Station Controller Biu khin trm gc

CIF Common Interface Format Khun dng giao din chung

COFDMCoded Orthogonal FrequencyDivision Multiplexing

Ghp knh phn chia theo tns trc giao c m ha

DABDigital Audio Broadcasting-Internet Protocol

Qung b m thanh s da trngiao thc Internet

DQPSKDifferential Quadrature PhaseShift Keying

Kha dch pha vung gc vi sai

DVB Digital Video Broadcasting Qung b video s

DVB-HDigital Video BroadcastingHandheld

Qung b video s my cm tay

EDGEEnhanced Data for GSMEvolution

Cc d liu tin tin i vipht trin GSM

ESG Electronic Service Guide Hng dn dch vin t

ETSIEuropean Telecommunication

Standards Institute

Vin tiu chun vin thng chu

u


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EV-DO Evolution Data Only D liu pht trin

FDMFrequency DivisionMultiplexing

Ghp knh phn chia theo tns

FEC Forward Error Correction Sa li trc

FLO Forward Link Only Ch lin kt hng i

GERANGSM EDGE Radio Access

NetworkMng truy nhp v tuyn GSMEDGE

GGSN Gateway GPRS Support Node Node h trcng GPRS

GPRS General Packet Radio Service Dch v v tuyn gi tng hp

GSMGlobal Systems for Mobilecommunications

H thng thng tin di ng toncu

HSDPAHigh Speed Downlink PacketAccess

Truy nhp gi ng xung tc cao

HSPA High Speed Package Access Truy nhp gi tc cao

ISI Intersymbol Interference Nhiu lin k t

ITU InternationalTelecommunications Union Hip hi Vin thng quc t

LOC Local Operation Center Trung tm khai thc ni ht

MBMSMultimedia Broadcast andMulticast Service

Dch v broadcast v multicasta phng tin

MCIMultiplex ConfigurationInformation

Thng tin cu hnh ghp knh

MFN Multifrequency Netwok Mng a tn s

MOT Multimedia Object TransferTruyn ti i tng aphngtin

MPE Multiprotocol Encapsulation ng gi a giao thc

MPEG Motion Pictures Expert Group Nhm chuyn gia vnh ng

MMS Multimedia Messaging Service Dch v tin nhn a phng tin

MSC Main Service Channel Knh dch v chnh


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NOC National Operating Center Trung tm khai thc quc gia

PDA Personal Digital Assistant H trs c nhn

PSS Packet Switching Streaming Dng chuyn mch gi

QAMQuadrature AmplitudeModulation

iu chbin cu phng

QCIFQuarter Common InterfaceFormat

Khun dng giao din chungmt phn t

QPSK Quadrature Phase Shift Keying Kha dch pha vung gc

QVGA Quarter Video Graphics Array Mng ha video mt phn t

RAN Radio Access Network Mng truy nhp v tuyn

RS Reed Solomon M Reed-Solomon

RTCP Real Time Control ProtocolGiao thc iu khin thi gianthc

RTSP Real Time Streaming ProtocolGiao thc truyn ti dng thigian thc

SFN Single Frequency network Mng n tn s

SGSN Serving GPRS Support Node Node h trGPRS phc v

SI Service Information Thng tin dch v

SMILSynchoronized MultimediaIntergration Language

Ngn ng tch hp a phngtin ng b

UMTSUniversal MobileTelecommunications Service

Dch v vin thng di ng toncu

UTRA Universal Terrestrial RadioAccess Truy nhp v tuyn mt tton cu

WCDMAWideband Code DivisionMultiple Access

a truy nhp phn chia theo mbng rng


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DANH MC HNH V

Hnh 1.1 M hnh chung thu pht tn hiu truyn hnh di ng .............. ..........13Hnh 1.2 Phn loi cc cng ngh truyn hnh di ng ...................................14Hnh 2.1 Gi giao thc dch v truyn ti dng gi 3GPP .............. ............... ..24Hnh 2.2 Truyn ti tn hiu MobileTV theo chun 3GPP .............. ............... ..26Hnh 2.3 Kin trc MBMS ..........................................................................28Hnh 2.4 Lung phin MBMS...................... ............ ............... ............... ......31Hnh 2.5 Kin trc h thng cung cp tn hiu Mobile TV qua mng 3G. ........35Hnh 2.6 H thng truyn dn truyn hnh di ng DVB-H............ ............... ..37Hnh 2.7 DVB-H IP Datacasting ........................... ............ ............... ............38Hnh 2.8 Ct lt thi gian trong DVB-H.... ............... ............. .............. ..........41Hnh 2.9 Cu trc khung MPE-FEC .............. ............... ............. .............. .....43

Hnh 2.10 DVB-H trong ghp knh dng chung ................. ..... ..... ..... ......... ..45Hnh 2.11 Cc mng n tn s DVB-H ............... ............... ............ .............46Hnh 2.12 Khong cch tng i SFN. Tt c khong cch trn csiu ch16QAM vi khong bo v cho COFDM ............... ............... ............ ........47Hnh 2.13 M hnh dch v truyn hnh di ng trn nn cng ngh T-DMB ....49Hnh 2.14 Chui truyn dn DAB/DMB ............................ ............ ...............51Hnh 2.15 iu ch mt sng mang s dng DQPSK trong DMB ............. ..... .52Hnh 2.16 Ghp xen theo tn s ...................................................................53 Hnh 2.17 Mng MediaFLO.........................................................................56Hnh 2.18 Kin trc phn lp FLO ...... ............... .................... ............ ..........58Hnh 4.1 M hnh trin khai dch v truyn hnh di ng DVB-H ca VTC......76Hnh 4.2 S khi th nghim T-DMB ti H Ni .............. ............... .........79


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DANH MC BNG BIU

Bng 2.1 Cc tham s vi 4 ch truyn dn T-DMB ............... ............... ....54Bng 3.1 So snh v hiu qu s dng ph, s lng knh v tc d liu.....62Bng 3.2 So snh cc tham s truyn dn .............. ............... ............ .............64Bng 3.3 So snh tham s mng my pht............... ............... ............ ...........65Bng 3.4 So snh s audio/video ............ ............... ............ ............... .......66


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CHNG 1 TNG QUAN V TRUYN HNH DI NG

1.1 Khi nim v truyn hnh di ng

Truyn hnh di ng (MobileTV) l cng ngh m ha v truyn dn ccchng trnh truyn hnh hoc video c ththu c trn cc thit bdi ng

nh in thoi di ng, cc thit b s h tr cm tay (PDA), cc thit b a

phng tin v tuyn, cc my in thoi c khnng thu tn hiu truyn hnh di

ng.

i vi MobileTV, ngi xem c th truy nhp cc chng trnh truyn

hnh trong khi di chuyn. Cc chng trnh c thc xem tc ging nhkhi c pht hoc c thc xem vi tr thi gian hoc c ghi li ton b

nh bng cassette video hoc a DVD. MobileTV khng ch cho php truyn

dn mt chiu thng thng m cn cho php truyn tn hiu truyn hnh tng

tc nh s dng cc knh phn hi c cung cp bi cc mng t bo. Cc

chng trnh c thc pht ch qung b (broadcast) trong mt vng ph

sng hoc pht ti mt ngi s dng theo yu cu (unicast) hay pht ti mt

nhm ngi s dng (multicast).

Mobile TV l cng ngh c thit k p ng c cc yu cu

truyn dn tn hiu truyn hnh trong mi trng v tuyn di ng c bng thng

hn ch, my thu u cui di ng c cng sut pin tiu th nh, kch thc mn

hnh nh v gii hn v tc lm ti. Cc nh hng quan trng ca mi

trng v tuyn di ng bao gm truyn dn a ng, fading v hiu ng

Doppler. Trong khi hn ch ca my thu di ng l cng sut pin nh, anten

tch hp bn trong c tng ch nh. Cc cng nghMobileTV c pht

trin khc phc cc hn ch ca mi trng truyn dn tn hiu truyn hnh di

ng cng nh nhng hn ch ca my thu tn hiu truyn hnh di ng ni trn.

1.2 Phng php thu pht tn hiu truyn hnh di ng

Hnh 1.1 m t m hnh chung thupht i vi truyn hnh di ng. upht cc chng trnh trc tin c m ha ngun (H.264, MPEG-4, HE-


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ACC, AMR,), sau c m ha knh, ghp xen, ghp knh vi cc chng

trnh khc ri a ti biu ch, khuch i cng sut v a ti anten pht ra

mng truyn dn v tuyn. u thu, my cm tay di ng thu c tn hiu

truyn hnh di ng s thc hin cc chc nng ngc vi phn pht bao gmgii iu ch, gii ghp xen, gii m knh v gii m ngun c th xem cc

chng trnh.

Mng 3G, DVB-H,

T-DMB, MediaFLO

.

B m ha

1

B m ha

n

B m ha

2

Ghpkn

h

iuch

KCS

Video

Audio

Chng trnh 1

Chng trnh 2

Audio

Audio

Video

Video

Chng trnh n

..

.

Hnh 1.1 M hnh chung thu pht tn hiu truyn hnh di ng

Hin nay c 2 phng php chnh pht tn hiu truyn hnh di ng,

l pht qua mng t bo hai chiu v pht qua mng qung b dnh ring mt

chiu. Mi phng php u c nhng u nhc im ring.

Pht tn hiu truyn hnh qua mng tbo c u im l s dng c c

sh tng mng c thit lp, do gim chi ph, cc thu bao ch cn ng

k dch v truyn hnh di ng m h mun s dng do c sn thtrng truy

nhp. Nhc im chnh ca phng php ny l bng thng b hn ch, lm

gim cht lng cc dch v truyn thng.


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Cc h thng MobileTV dnh ring c thit k ti u ha s phn

pht tn hiu truyn hnh di ng. Cc h thng ny c th pht trn mt t, v

tinh hoc kt hp c hai. Mt trong nhng u im chnh ca phng php ny

l c thc pht qung b ti nhiu ngi s dng ng thi. Nhc imca h thng ny l cn u t ng k vo h tng mng v cc la chn ni

dung b hn ch.

3G NetworkBased

Unicast

MulticastBroadcast

3GPP

3GPP2

3G - UMTS

HSDPA

CDMA2000

EV-DO 1x

3GPP

3GPP2

HSUPA

EV-DO 1x

MBMS

BCMCS

TerrestrialTransmission

Broadcast

DVB-H

DMB-T

ISDB-T

SatelliteTransmission

Broadcast

DMB-S

ISDB-S

DAB

Broadband

Unicast &Multicast

Wi-max

WiBro

UWB

DAB-IP

MediaFLO

Hnh 1.2 Phn loi cc cng ngh truyn hnh di ng

Cc cng ngh MobileTV cnh tranh nhau t c th phn chia s th

trng, chng c ngun gc khc nhau v c pht trin vi cc mc ch khc

nhau. Cc cng nghMobileTV c phn loi nh Hnh 1.2. MobileTV c

chia thnh MobileTV da trn cc mng 3G, cc mng qung b mt t v v

tinh, cc mng v tuyn bng rng.


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1.3 Cc tiu chun i vi MobileTV

Xem truyn hnh di ng c vhon ton n gin, nhng chnh sn

gin n cha rt nhiu cng ngh v tiu chun c pht trin trong

mt thi gian a vo truyn hnh nhng mn hnh nh c2 inches.

MobileTV c khong trn 30 loi khun dng file m thanh gm dng cc

file n gin c ui .wav, .mpg, Real, QuickTime, Window Media 9/10/11 v

cc khun dng file khc. Video th c khong 25 khun dng khc nhau t cc

file video khng nn n file nn c khun dng MPEG-4, MPEG4-AVC/H.264.

Hn na, video c th trnh din vi mt di rng phn gii, kch thc

khung v tc .

Cc tiu chun c s dng lm nn tng chung cho vic phn pht cc

dch v MobileTV. Cc tiu chun c th khc nhau da trn cng nghnhng

t c s thng nht chung. iu ny i hi cc b phn phi lm vic

cng nhau. T cc nh thit k v sn xut chip ti cc nh thit k hiu hnh

v phn mm ng dng, cc nh thit k v sn xut my cm tay, cc nh pht

trin phn mm, cng ng qung b tn hiu truyn hnh, cc nh khai thc 3G

v cc nh khai thc qung b truyn hnh v tinh cng nh cc b phn lin

quan khc. Ngoi ra vic tiu chun ha ny cng lin quan n ngnh cng

nghip ch to ni dung thit k ni dung m thanh v video cho cc my u

cui di ng, ngnh cng nghip di ng tbo thit lp cc h thng truyn

dn tn hiu truyn hnh di ng v nhiu ngnh cng nghip khc. Cc tiu

chun MobileTV c tng kt trong khuyn ngh ITU-R BT1833. Ngoi cctiu chun trong khuyn ngh ny cn c cc cng ngh truyn hnh di ng

c tiu chun ha v c trin khai nhiu nc nh cng ngh VSB tin

tin, h thng qung b a phng tin di ng Trung Quc (CMMB).

1.4 Ti nguyn pht trin truyn hnh di ng

i vi MobileTV, mt ngun ti nguyn chung quan trng l ph tn s.

Anh v M ph tn s dnh cho truyn hnh truyn thng nm trong di VHF


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v UHF. Anh, cng ty BT Movio s dng ph tn s dnh cho qung b m

thanh s(DAB) pht tn hiu truyn hnh di ng s dng tiu chun DAB-

IP. Hn Quc, ph tn DAB dnh cho cc d ch v vtinh c s dng

pht dch v truyn hnh di ng theo khun dng tn hiu qung b a phngtin s qua v tinh (DMB-S). Hn Quc cng cho php s dng ph tn s VHF

cung cp dch v truyn hnh di ng s dng cng ngh qung b a phng

tin s mt t (DVB-T). Cng ngh qung b a phng tin s cho my cm

tay (DVB-H) l mt tiu chun c thit k s dng cc mng DVB-T pht

cc dch v DVB-H v s dng chung ph tn s ca DVB-T. M, Modeo,

nh khai thc DVB-H thit lp mt mng hon ton mi da trn DVB-H s

dng bng tn L 1670 MHz; cn HiWire, mt nh khai thc khc s dng ph

tn 700 MHz pht dch v DVB-H.

1.5 Gii thiu cc cng ngh truyn hnh di ng

1.5.1 MobileTV s dng cc mng t bo

S trin khai cc cng ngh 2,5G vi tc d liu cao hn cho php

cc nh khai thc mng di ng cung cp cc dch va phng tin nh video,

m thanh ging nh truyn ti dng IP qua mng Internet. Tuy nhin, do cc

iu kin truyn dn v mng, tn hiu clip video b tr v cht lng tn hiu

khng cao do tc khung thp. S pht trin t2,5G n 3G tng tc d

liu, s pht trin ca cc giao thc m thanh v video cng vi k thut m ha

ngun hiu qu MPEG-4 dn ti mng 3G c th cung cp cc knh video trc

tip tc 128 kbps hoc cao hn. Cc mng 3G c thit k c th cungcp tc d liu cao ln ti 384 kbps, do cc mng 3G c thc s dng

cung cp cc dch v truyn hnh di ng. Mng 3G c trin khai bi

mt s nh cung cp dch v nhiu nc trn th gii : M (Sprint, Alltel,

Verizon), Mexico (Telcel), Peru (Moviestar), Canada (Bell, Rogers), Anh

(Orange, Three)


17/88



Hip hi Vin thng Quc t(ITU) thng nht cc mng 3G vi tn

gi IMT-2000 da trn 2 cng nghli c bn l UMTS v CDMA2000. Cng

ngh UMTS (WCDMA) c pht trin i vi cc nc ang khai thc mng

GSM, cc tn s 3G UMTS c phn b ri rc trong ph tn ca UMTS.Trong khi cng ngh CDMA2000 c thit k tng thch vi cc mng

CDMA One. Cc dch v MobileTV da trn mng 3G c th cung cp dng

truyn ti d liu di ng chp nhn c tc 300 kbps, tng ng 10

cuc gi trong mng. iu ny ngha l cung cp 1 dng truyn ti video,

mng 3G b tn tht 10 cuc gi. Do bng thng kh dng b hn ch, cc mng

3G khng ti u pht tn hiu truyn hnh di ng ti slng ln ngi s

dng ng thi. Dn 3GPP ang pht trin cc cng ngh mi tng tc ,

mrng vng ph v cc loi hnh dch v c th cung cp trn cc mng 3G. V

dnh cng ngh truy nhp gi ng xung tc cao (HSDPA) v cng ngh

Broadcast v Multicast a phng tin (MBMS) c pht trin h trcc

dch v m thanh v video.

Trong iu kin bnh thng, mng HSDPA c th pht tc 384 kbps

ti 50 ngi s dng trong mt cell, HSDPA c thtng tc bit ln ti 10

Mbps hoc cao hn (ng xung) trn cc mng 5MHz 3G nh s dng m

ha v iu chthch nghi, nh hnh gi nhanh v k thut chn t bo nhanh.

u im chnh ca HSDPA l c xy dng trn c sh tng mng 3G hin

ti, do cc nh khai thc c th s dng giy php mng 3G m khng cn

u t xin thm cc tn s mi.

Vi mng 3G cng nghbroadcast v unicast a phng tin (MBMS)

c tiu chun ha pht tn hiu ch qung b. Cng ngh MBMS c 2

ch cung cp dch v ti s lng ln ngi s dng. Phin bn th su

3GPP nh ngha MBMS c cc ch cung cp dch v :

- Ch multicast truyn tn hiu t ngun pht ti tt c cc thit b trongmt nhm multicast. Cc thit b ny c th nm cc cell khc nhau hoc ang


18/88



di chuyn. Do truyn dn multicast khng pht d liu ti tt c ngi s

dng trong mt vng nht nh m s phn pht d liu ny c tnh chn lc.

- Ch pht broadcast truyn tn hiu ti tt cngi s dng trong mtvng nht nh.

1.5.2 MobileTV s dng truyn dn s mt t v v tinh

l cc cng ngh nh : DVB-H, DMB-T, ISDB-T, DAB-IP,

MediaFLO, DVB-SH, DMB-S, ISDB-S, ATSC-M/H.

1.5.2.1 Cng ngh qung b a phng tin s cho cc my cm tay (DVB-

H)

Cng ngh ny da trn tiu chun qung b video s mt t (DVB-T),

c ti u cho cc my u cui cm tay, s dng chung ph tn s ca DVB-

T. DVB-H s dng khun dng m ha ngun MPEG-4 hoc Window Media 9

i vi video v m ha ngun AAC. DVB-H s dng dng truyn ti IP qua

MPEG-2 TS, v s dng k thut ct lt thi gian (time slicing) gim cng

sut tiu th v h trchuyn giao gia cc t bo. DVB-H s dng iu ch

COFDM vi cc s khc nhau nh QPSK, 16QAM, 64QAM khc phc

nh hng ca nhiu a ng i vi cc my thu di ng. H thng DVB-H

cng h tr ch iu ch OFDM 4K ph hp vi mi trng di ng bn

cnh cc ch 2K v 8K. DVB-H c thit k hot ng cc bng thng 5,

6, 7 v 8MHz, y l cc bng thng c s dng cho cc d ch v qung b

trn th gii. K thut m ha knh c s dng trong DVB-H l m xon kt

hp vi m Reed Solomon. DVB-H hot ng bng tn UHF hoc bng tn L(M). DVB-H c s dng chu u, M v mt snc chu .

1.5.2.2 Cng ngh qung b a phng tin s qua mt t (DMB-T)

Cng ngh ny pht trin t h thng Eureka-147 cho qung b m thanh

s(DAB) cung cp cc dch va phng tin gm video, m thanh v cc

dch vtng tc. DMB l s m rng ca tiu chun DAB nh thm vo lp

sa li nhm truyn cc dch va phng tin. DMB s dng di ph c


19/88



phn b cho DAB nn vic trin khai DMB trnn d dng v thnh cng. C 2

phin bn DMB l DMB-T v DMB-S (qung b a phng tin s qua v tinh).

i vi DMB-T, bng tn VHF v UHF c s dng. DMB-T chia khe VHF 6

MHz thnh 3 sng mang, mi song mang c bng thng 1,54 MHz, c th truynti 4 knh video v cc knh m thanh ph. DMB-T s dng k thut m ha

ngun H.264 MPEG-4 i vi video v m ha ngun BSAC, MPEG-2 i vi

m thanh, dng truyn ti l MPEG-2 TS. DMB-T thc hin ghp knh theo tn

s FDM, s dng iu chDQPSK, m ha knh c s dng l m xon kt

hp Reed Solomon. DMB-T khng h trk thut tit kim ngun nn y l

vn quan trng i vi cc my di ng cm tay c cng sut pin thp. DMB

c trin khai u tin Hn Quc v cc nc chu u nh c, Anh.

1.5.2.3 Cng ngh qung b a phng tin s qua v tinh (DMB-S)

DMB-S l phin bn ghp lai ca cng ngh qung b a phng tin s

DMB. S dng bng tn L (1452 1492 MHz) v bng tn S (2170 2200

MHz) ca IMT v phn pht khong 18 knh truyn hnh tc 128 kbps

bng thng 15 MHz. DMB-S tch hp mt v tinh a tnh cng sut cao.

m bo thu c tn hiu trong nh, cc ta nh c trang b them cc b lp

bng tn S pht lp tn hiu trn mt t. Hn Quc l nc u tin khai

trng dch v DMB-S vo nm 2005. Cc knh video DMB-S c khong 20

knh v m thanh c khong 13 knh. Cht lng m thanh t xp x cht

lng CD vi m ha AAC tc 128 kbps.

1.5.2.4 Cng ngh qung b s dch v tch hpmt t (ISDB-T)Khuyn ngh ITUR BT1833 m t 2 h thng ISDB-T ring bit. H

thng th nht da trn cng ngh ISDB-T 1 segment (s dng 1/13 bng thng

ca truyn dn s mt t), hot ng bng thng 429 kHz, 500 kHz hoc 571

kHz. H thng th hai l h thng mt t kt hp v tinh hot ng bng

thng 25 MHz. ISDB-T s dng k thut m ha ngun H.264 MPEG-4/AVC

i vi video, m ha ngun MPEG-2 AAC i vi m thanh, dng truyn ti l

MPEG-2 TS, s dng iu ch COFDM (QPSK, DQPSK, 16QAM, 64QAM), h


20/88



tr iu ch OFDM 4K ngoi 2K v 8K. ISDB-T c s dng Nht Bn,

Brazil v Peru.

1.5.2.5 Cng ngh ch lin kt hng i a phng tin (MediaFLO)

y l mt h thng end-to-end cho php pht qung b cc dng truyn

ti video, m thanh, cc file phng tin sti my thu di ng. H thng ny

c pht trin bi hng Qualcomn, c thit k ti u vng ph, dung

lng v cng sut tiu th ca my thu. H thng hot ng bng tn 700

MHz (M), bng tn UHF hoc bng tn L, MediaFLO c th hot ng tn

s bt k t 300MHz1,5GHz v c thit k ti u trong bng UHF vi cc

bng thng 5, 6, 7, 8 MHz. Nh s dng my pht c cng sut cao nnMediaFLO c th pht ti khong cch xa ti 50km. Ch cn 3, 4 my pht

MediaFLO c th ph song ton b mt vng thnh ph. MediaFLO c trin

khai Mv c th nghim Anh v c.

1.5.2.6 Cng ngh cc h thng truyn hnh tin tin ti my di ng cm

tay (ATSCM/H)

L mt tiu chun c s dng M pht qung b cc knh truynhnh ti cc thit bthu di ng. ATSC M/H s dng cc s m ha knh

mi chng li nh hng ca Doppler v a ng. ATSC-M/H s dng m

ha bn ngoi l m Reed Solomon v m xon. Khnng sa li c ci thin

bng cch s dng k thut kim tra tng CRC v k thut gii m ty. D liu

c bo v bi m sa li hng i FEC. ci thin cht lng tn hiu

my thu, ATSC-M/H s dng cc chui san bng knh cho php sc lngknh my thu. ATSC-M/H s dng k thut time slicing tit kim pin cho

my thu.

1.5.2.7 Cc cng nghMobileTV khc ang trong giai on tiu chun ha

hoc c trin khai

Cng ngh MobileTV qung b m thanh s da trn nn IP (DAB-IP)

c tiu chun ha bi ETSI nm 2006. DAB-IP c th cung cp cc dch vMobileTV vi cc khe ph tn s 1,5 MHz kh dng cho cng ngh DAB.


21/88



DAB-IP s dng lp IP truyn ti cc dng d liu m thanh, video v IP.

DAB-IP s dng nhiu k thut m ha ngun i vi video v m thanh. Lp

IP c th c truyn ti qua nhiu loi mng qung b v unicast nh DAB,

DVB-H hoc mng 3G (UMTS). Cng ngh ny c s lng knh hn ch sovi DVB-H v MediaFLO v c trin khai thng mi Anh nm 2006.

Cng ngh qung b a phng tin di ng Trung Quc (CMMB) l h

thng qung b v tuyn kt hp mt tv tinh. H thng ny hot ng

bng thng 2MHz hoc 8MHz, s dng iu ch OFDM v h trcc dch v

tng tc.

1.5.3 MobileTV s dng cng ngh v tuyn bng rng

1.5.3.1 MobileTV sdng cng ngh WiFi

Cc mng WiFi (802.11x) trnn ph bin trong vic cung cp d ch v

truy nhp Internet. Cc mng WiFi ngy nay ang c s dng nhiu trong cc

khu vc cng cng nh cc ta nh, qun caf, bnh vin, khch sn, sn bay

WiFi cho php truyn dn tc cao hn cc mng di ng. Tiu chun WiFi

802.11b c th cung cp tc ln ti 11Mbps, trong khi tiu chun WiFi

802.11g tng thch vi 802.11b c th c cung cp ln ti 54 Mbps. Do

truyn dn d liu tc cao, WiFi c xem l mt phng thc truyn dn

tn hiu truyn hnh di ng. Vi WiFi, ngi s dng di ng c th ti cc ni

dung truyn hnh qua Internet s dng my di ng cm tay. WiFi c chi ph

hiu qu v khng yu cu giy php mng v tng i r trin khai. Tuy

nhin vn tn ti cc vn cn gii quyt nh chuyn vng gia mng WiFi

vi cc mng cell, vng ph hp, vn tnh cc,

1.5.3.2 MobileTV sdng cng ngh WiMAX

WiMAX l cng ngh cho php truyn dn cc dch v d liu trong mt

vng ph rng hn so vi WiFi. WiMAX c th cung cp dung lng cao hn

v do t hn so vi WiFi. WiMAX rt ph hp truyn dn video v ni

dung a phng tin. WiMAX c th cung cp dch v truy nhp Internet v


22/88



tuyn tc cao khi my thu ang chuyn ng thm ch ln ti tc 60km/h.

Cc ng dng in hnh ca WiMAX l m thanh v video theo yu cu. Vi

WiMAX, ngi s dng di ng c th ti v hoc xem video trc tip khi ang

di chuyn trn tu hay tWiMAX h trchuyn vng gia n v cc mngdi ng, cc my cm tay di ng c th chuyn t mng di ng ti cc kt ni

v tuyn. Tuy nhin, nhc im ca WiMAX l s dng ph tn s cn c

cp php, khng ging nh WiFi. WiMAX c th cung cp tc cao hn 20

Mbps v vng ph rng trong ton thnh ph vi mt s t my pht.

WiMAX c c t bi 2 tiu chun : WiMAX truy nhp v tuyn c

nh (IEEE 802.16d) c th cung cp tc d liu trong khong 70 100Mbps. IEEE 802.16d s dng cng ngh iu ch OFDM a sng mang (256

sng mang) v k thut truy nhp OFDMA vi 2048 sng mang khc phc

cc nh hng ca fading a ng v fading chn lc tn s. WiMAX truy

nhp cnh c trin khai chu u, M, Singapore, Hng Kng v nhiu

nc khc. WiMAX di ng (IEEE 802.16e) s dng iu ch OFDM c th

cung cp tc d liu ln ti 15 Mbps trong phm vi 10km, cho php my cm

tay di chuyn tc ln ti 150km/h.

u im ca WiMAX cng nh WiFi l chng u cung cp ch

unicast im ti im cng nh pht ni dung qung b trong mt mng.

iu ny lm cho WiMAX v WiFi ph hp cung cp cc dch v qung b

truyn hnh di ng, truyn ti dng video v video theo yu cu vi stng

tc i vi ngi s dng di ng.


23/88



CHNG 2 CC CNG NGH TRUYN HNH DI NG C BN

2.1 Mobile TV s dng mng 3G

2.1.1 Gii thiu

Cc mng 2,5G v 2,75G nh GPRS, CDMA 1xRTT v EDGE c pht

trin bi cc nh mng 2G c th cung cp cc ng dng d liu v truyn ti

dng m thanh, video Cng ngh 3G-UMTS c th cung cp cc kt ni

chuyn mch knh ln ti tc hn 384kbps v cung cp cc kt ni chuyn

mch gi ln ti tc 2Mbps bng cch s dng cc sng mang 5MHz, ci tin

cc giao din v tuyn v cc cu trc mng li. Cng ngh CDMA2000 EV-DOc th cung cp cc dch v vi tc t 400 700kbps, v c th ln ti

2Mbps.

Do khnng cung cp tc truyn dn cao ca cc mng di ng 3G

nn vic trin khai cung cp tn hiu truyn hnh di ng MobileTV qua cc

mng 3G l hon ton kh thi. Nhng nm trc, nhiu nh khai thc mng t

bo bt u cung cp cc dch v MobileTV trn mng 3G v 2,5G s dngcng ngh truyn ti dng chuyn mch gi (PSS). Ngy nay, PSS c h tr

bi cc nh sn xut thit b u cui v cung cp cc dch v truyn ti dng c

cht lng chp nhn c. Cht lng c ci thin nh s dng b m

ha/gii m video H.264 v s dng cc phn mang truyn ti dng c h tr

QoS. Cht lng v dung lng cng c ci thin nhs dng cng ngh truy

nhp gi ng xung tc cao HSDPA.

Nhc im chnh ca cng nghunicast l dung lng mng gim khi c

nhiu ngi xem cng mt chng trnh truyn hnh ng thi. Khi cng

ngh broadcast l cng ngh truyn ti thch hp hn. D n hip hi th h ba

3GPP hon thnh c t cng ngh dch vbroadcast v multicast a phng

tin (MBMS) phin bn UMTS 6. D n 3GPP2 c t cng ngh dch v

broadcast v multicast (BCMCS) i vi CDMA2000. 3GPP MBMS v 3GPP2BCMCS c nhiu im tng ng, cMBMS v BCMCS u yu cu s thay


24/88



i nhi vi cc giao thc mng li v v tuyn hin ti. iu ny lm gim

chi ph thc hin cc thit bu cui v mng, lm cho cng ngh qung b t

bo c chi ph tng i r so vi cc cng nghkhc nh DVB-H, DMB (cc

cng ngh ny yu cu phn cng my thu mi thit b u cui v u tng kvo c sh tng mng).

2.1.2 MobileTV s dng cc tiu chun 3GPP Dch v truyn ti dng

chuyn mch gi (PSS)

HTTP

SDP

RTSP

TCP

IP

UDP

RTCP RTP

PayloadFormats

Scene description

Images, Graphics,

Text

Session Setup,

Control Quality FeedbackMedia Delivery

Video Audio

Hnh 2.1 Gi giao thc dch v truyn ti dng gi 3GPP

Vic cung cp tn hiu MobileTV hoc tn hiu video qua truyn ti dng

streaming l mt trong nhng phng php ph bin nht phn pht tn hiu

video. Tiu chun PSS c pht trin bi 3GPP l tiu chun ch yu c s

dng truyn ti dng unicast trong cc mng t bo. Mc tiu chnh ca PSS

l nh ngha mt ng dng cung cp truyn ti dng ng b cc tn hiu media

nh m thanh, video v vn bn. PSS nh ngha ng dng ti v cc file 3GP

v cng nh ngha ng dng da trn ngn ng tch hp a phng tin ng

b(SMIL) biu din tn hiu a phng tin.


25/88



3GPP-PSS ch yu da trn cc giao thc c pht trin bi IETF (y

ban nhim v k thut Internet). 3GPP-PSS nh ngha gi giao thc cho vic

thit lp v truyn ti d liu s dng lp IP (Hnh 2.1). Cc khun dng file m

thanh, video, ha, m t hnh nh v biu din thng tin cng c m t. Gigiao thc 3GPP-PSS thng nht vic thit lp cuc gi v truyn ti d liu a

phng tin qua cc mng khc nhau thm ch khi cc mng ny c giao din v

tuyn khc nhau.

Cc giao thc chnh gm giao thc truyn ti dng thi gian thc (RTSP)

iu khin phin, giao thc m tphin (SDP) m t phn biu din v

giao thc truyn ti thi gian thc truyn ti tn hiu media. Ngoi ra giaothc HTTP c s dng ti v cc m t biu din v hnh nh.

PSS bao gm mt stnh nng nhm ci thin cht lng truyn ti dng

qua mng. Mt trong nhng tnh nng ny l truyn ti dng thch nghi, cho

php dch v truyn ti dng thch nghi vi cc iu kin ca mng. iu ny l

cn thit v xem mt dng truyn ti a phng tin th mng truyn ti phi

cung cp c thng lng t nht cao hn tc ni dung c m ha.Mc d cc mng c nng lc cao nht c th cung cp tc bit yu cu nhng

cc mng ny khng thm bo tnh kh dng ca tc bit yu cu trong sut

thi gian tn ti ca phin, c bit l trong cc ng truyn v tuyn di ng

khi m thng lng thay i do tnh cht ca knh v tuyn.

Mt trong nhng vn tiu chun PSS hin nay l PSS khng h trs

chuyn knh nhanh (zapping) nh truyn hnh thng thng, PSS thng mt t8 n 10s chuyn t knh ny sang knh khc. S chuyn knh trong PSS yu

cu ngt phin truyn ti dng ang tip din, thit lp mt phin mi v in

y d liu vo bm client trc khi xem trli. iu ny c khc phc

bng cch chia s mt phin truyn ti dng i vi tt c cc knh c s

dng trong sut mt phin MobileTV. Nu mt ngi s dng chn mt knh

no , s ca knh c chn s c thng bo ti Streaming Sever.Streaming Sever lp tc chuyn tip d liu media ca knh mi ti client.


26/88



Mt v d in hnh v truyn ti tn hiu 3GPP MobileTV c m t

trong hnh 2.2. Trong gm 2 server :

- Broadcast Server thc hin m ha ni dung m thanh, video v ng githnh cc gi IP UDP/RTP

- Streaming Server cung cp nhiu dng truyn ti RTP unicast ti nhiumy di ng cm tay.

Video/ Audio

Sources

Mobile Network

Mobiles with

3GPP Players

RTP/UDP

RTP/U

DP

RTSP/TCP

Unicast RTP

Broadcasting Server

H.263 Video Enc

AMR Audio Enc

RTP Encapsulation

.3gp

.mp4

Hnh 2.2 Truyn ti tn hiu MobileTV theo chun 3GPP

Cc ngun m thanh v video c th l cc my quay phim video hoc

my thu/gii m tn hiu t v tinh hoc ni dung video bng video c lu

tr. Broadcast Server m ha video s dng chun H.263 v m ha m thanh

theo chun AMR v cung cp gi IP truyn qua RTP/UDP. phn gii video

ca dng c m ha gii hn bi 3GPP, v dkch thc QCIF c tc

chung l 1530fps. M ha m thanh c th l AMR c tc 4.7 kbps n 12.3

kbps.

Streaming server thit lp cc kt ni unicast imtiim ti cc my

di ng mun thu tn hiu video theo ch streaming. D liu m thanh, video

c gii m my thu di ng s dng chng trnh 3GPP player c tch

hp.


27/88



2.1.3 Cng ngh MBMS

Vi s pht trin ca cc ng dng yu cu bng thng cao, c bit vi

slng ln cc thit bngi s dng mun thu cng mt ni dung dch v,

broadcast v multicast l phng thc phn pht d liu hiu quhn unicast.Cc phng php ny lm gim lng d liu c pht trong mng, do gim

chi ph ng k.

Cng ngh dch vbroadcast v multicast a phng tin (MBMS) v

cng ngh dch vbroadcast v multicast (BCMCS) c c t bi 3GPP v

3GPP2 tng ng. MBMS v BCMCS bsung cc tnh nng sau vo mng di

dng :

- Tp cc chc nng iu khin dch v phn pht broadcast/multicast MBMS gi l trung tm d ch v broadcast/multicast (BM-SC) cn

BCMCS l biu khin BCMCS.

- nh tuyn broadcast/multicast cc lung d liu trong mng li.- Cc phn mang v tuyn (bear) hiu qui vi truyn dn v tuyn t

imtia im trong mt t bo.

Ngoi ra, MBMS v BCMCS cng c t cc giao thc v cc b m

ha/gii m i vi vic phn pht d liu a phng tin. MBMS v BCMCS

h trhai kiu kt ni imtia im :

- Ch broadcast : mng pht d liu ti tt cngi s dng trong mtvng qung b xc nh.

- Ch multicast : mng pht d liu ch ti nhng ngi s dng yu cud liu ny.


28/88



2.1.3.1 Kin trc MBMS

UE

GERA

NUE

HLR

GGSN

TPFSGSNUTRAN BM-SC

OSA

SCS

Uu

Um

Iu

Gr

Gb

Gmb

Gi

Gn/Gp

PDN

Vd : InternetNgun cung cpni dung/

multicast/broadcast

Ngun cungcp

ni dung/multicast/

broadcast

Hnh 2.3 Kin trc MBMS

Hnh 2.3 m t kin trc MBMS. MBMS kh dng vi c mng truy nhp

v tuyn GSM/EDGE (GERAN) v mng truy nhp v tuyn mt t UMTS

(UTRAN). Trung tm dch v broadcast/multicast (BM-SC) c b sung vo

mng. BM-SC thc hin vic cung cp v phn pht cc dch v qung b di

ng. BM-SC ng vai tr lm im vo vi cc dch v phn pht ni dung

mun s dng BM-SC. BM-SC thit lp v iu khin cc phn mang truyn ti

ti mng li di ng v c thc s dng nh trnh v phn pht cc knh

truyn dn MBMS.

BM-SC cng cung cp cc thng bo dch v ti cc thit bu cui. Cc

thng bo ny bao gm tt c cc thng tin cn thit (nh m t dch v

multicast, cc a ch multicast IP, thi gian truyn dn, cc m tmedia) m

thit b u cui cn c th tham gia vo mt d ch v MBMS. BM-SC c th

c s dng to ra cc bn tin tnh cc i vi d liu c pht t nh

cung cp ni dung v qun l cc chc nngbo mt c c t bi 3GPP cho

ch multicast.


29/88



BM-SC cung cp hai giao din ti mng li. Qua giao din GmB, BM-SC

trao i thng tin iu khin vi node h trGateway GPRS (GGSN). Giao din

Gi truyn ti d liu ni dung ti GGSN. Cc nh cung cp ni dung phn pht

cc ni dung ca mnh ti BM-SC (nh cung cp ni dung khng pht ni dungti tt cngi s dng qua cc knh ginh ring m ch pht ni dung ti BM-

SC). BM-SC s phn pht cc ni dung ny ti ngi s dng. Giao din gia

BM-SC v content server c th c t trong mng di ng hoc ngoi

mng.

Mt tnh nng c bit ca MBMS l MBMS cho php cc nh khai thc

nh ngha dch vbroadcast v multicast i vi cc vng a l c th. Ccvng a l ny c cu hnh qua cc vng dch v MBMS. Mi node trong

mng li s dng danh sch cc node downstream xc nh node no nn

c s dng chuyn tip d liu dch v MBMS. mc GGSN, danh sch

bao gm mi node serving GSN (SGSN) m d liu sc chuyn tip. mc

SGSN, danh sch bao gm mi node biu khin mng v tuyn (RNC) ca

mng truy nhp v tuyn mt t WCDMA hoc trong trng hp ca mng

truy nhp v tuyn GSM s bao gm mi biu khin trm gc (BSC) cn thu

d liu. i vi cc dch v hot ng ch multicast, mng li qun l cy

phn b d liu ng bng cch gim st nhng ngi s dng ng k s dng

dch v. Ging nh IP multicast, mi node mng li chuyn tip d liu MBMS

ti cc node downstream ang phc v nhng ngi s dng ng k s dng

dch v.

2.1.3.2 Cc ch ca MBMS

Dch v MBMS cung cp ba ch phn pht d liu : broadcast,

broadcast tin tin v multicast. S khc nhau gia cc ch ny l mc qun

l nhm trong mng li v mng v tuyn.

ch MBMS broadcast, BM-SC xc nh vng qung b khi kch hot

cc phn mang phn phi. Mng khng c bt k thng tin g v cc my thu


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kch hot trong vng qung b v khng th ti u ngun ti nguyn c s

dng.

Ch MBMS broadcast tin tin cho php s dng hiu qu hn vic

phn pht ti nguyn so vi ch broadcast. Ngi s dng dch v ch th

joining ti mng v tuyn. Mng v tuyn c th thc hin th tc counting

hoc re-counting xc nh slng ngi s dng trong mi tbo. C ch

ny da trn bn tin p ng counting MBMS c gi bi ngi s dng UE

khi UE thu c yu cu counting. Sm ngi s dng ny c s dng

xc nh kiu truyn ti c s dng. Nu c t ngi s dng yu cu d ch

v MBMS trong mt t bo th vic phn pht d liu MBMS theo cc knhdnh ring imtiim hoc cc knh c chia s ca HSDPA s hiu qu

hn, v truyn dn trn cc knh ny c thc ti u theo iu kin thu v

tuyn ca thit b u cui tng ng. Phn pht d liu MBMS imtia

im trnn hiu quhn nu c slng ln ngi s dng yu cu dch v

trong cng mt t bo.

ch MBMS multicast, ngi s dng dch v ch th joining timng li. Mng gim st trng thi joning ny cc node GGSN, SGSN v

cc biu khin mng v tuyn RNC. Khi thit bu cui ngi s dng di

chuyn t vng ny sang vng khc, trng thi joining vi tt c cc dch v

c tham gia bi ngi s dng c chuyn ti mt node phc v mi.

Cc RNC c th s dng th tc counting hoc re-counting xc nh s

lng ngi s dng yu cu dch v MBMS multicast thc s. Do mnggim st c ngi s dng dch v v thit lp cy phn phi i vi mt

phng ngi s dng MBMS rt hiu qu.

2.1.3.3 Truy nhp ti cc dch v MBMS

Hnh 2.4 m t lung in hnh cc phin MBMS. Ch broadcast cho

php truyn dn d liu a phng tin theo mt chiu timti-a im. Ch

broadcast khng yu cu ngi s dng phi ng k trc hoc joining.Tt cngi s dng trong mt vng dch v qung b c nh ngha bi nh


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khai thc mng u c th thu thp c d liu. Tuy nhin, ngi s dng

khng mun thu d liu ny c th cu hnh thit bu cui UE ca mnh ch

khng thu d liu. Ch multicast yu cu ngi s dng phi ng k

thu c cc dch vMBMS. Ngi s dng gim st cc bn tin thng bo dchv v quyt nh tham gia s dng mt hoc nhiu dch v. Tnh cc c thc

hin da trn vic ng k trtrc hoc da trn vic mua cc kha cho php

truy nhp ti d liu c pht.

Tham gia

Thng bo dch v

Bt u phin

Thng bo MBMS

Truyn ti d liu

Kt thc phin

Ri mng

ng k

Broadcast Multicast

Mng

Thng tin vdch v c

cung cp

M u phin

Pht d liu

Kt cuiphin

Quyt nhkt thc s

dng dch v

Quyt nh sdng mtdch v

ng k

thng tin

MBMS v cc

dch v

Khch hng

(Client)

Hnh 2.4 Lung phin MBMS

Khi u, thng tin v mt dch vMBMS c bit c gi ti servercung cp dch v. Thng tin ny c gi l thng bo dch v. Cc thng bo

dch v cung cp thng tin v dch v v bng cch no cc thit bu cui

c th truy nhp ti dch v. C nhiu cch phn pht cc thng bo d ch

v ti ngi s dng, nh lu gi cc thng bo ny web server m t

chng c th c ti v bng giao thc HTTP hoc giao thc truy nhp v

tuyn WAP hoc phn pht cc thng bo d ch v bng bn tin SMS hoc MMS

hoc s dng mt knh thng bo dch vMBMS c bit.


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Nu dch v l broadcast, thit bu cui ch cn iu chnh ti knh c

cc tham sc m t trong thng bo dch v. Nu dch v l multicast, mt

yu cu tham gia phin (session join) phi c gi ti mng vi cc tham s

c tch ra t thng bo dch v. Thit bu cui ngi s dng trthnh mtthnh vin ca nhm dch vMBMS tng ng v thu tt c d liu c pht

bi dch v.

Trc khi truyn dn d liu bt u, BM-SC phi gi mt yu cu khi

u phin (session start) ti GGSN trong mng li. GGSN xc nh cc ngun

ti nguyn ni b cn thit v chuyn tip yu cu ti cc SGSN lin quan. Cc

SGSN li yu cu phn b ngun ti nguyn v tuyn cn thit cung cp chtlng dch v QoS yu cu. Cui cng cc thit bu cui ca nhm dch v

MBMS tng ng c thng bo rng dch vl phn pht ni dung.

Sau server c th gi d liu a phng tin ti BM-SC. BM-SC

chuyn tip d liu ti MBMS bearer. ch multicast, d liu c mt m

ha v c pht ti mi thit bu cui tham gia phin MBMS.

Sau cng, server gi mt thng bo kt thc phin (session stop) ch th

rng pha truyn dn d liu kt thc.

Ngi s dng mun ri khi mt dch v multicast MBMS gi mt yu

cu ri khi d ch v (service leave) ti mng. Mng sau s loi bngi s

dng t nhm MBMS lin quan.

Truy nhp v tuyn Broadcast/Multicast G

cc h thng GSM, MBMS s dng cc s m ha v iu ch

GPRS v EDGE. MBMS cng s dng knh d liu gi (PDCH) GPRS v

EDGE truyn dn t im ti a im, v s dng cc giao thc iu

khin lin kt v tuyn/iu khin truy nhp mi trng (RLC/MAC). i vi

truyn dn im tia im, MBMS h trcha khe thi gian. Trong


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trng hp ny, mng v tuyn c th s dng ti 4 khe thi gian trn mt phin

MBMS.

Cc thit bu cui MBMS c th da trn phn cng EDGE hin ti vi

nng cp phn mm h trcc th tc bo hiu MBMS. GSM, phn mang

v tuyn MBMS c th c ghp knh vi cc lung d liu GPRS/EDGE

thm ch trn cc khe thi gian ging nhau. Mt kch bn trin khai c th l

kch hot MBMS trong mt vng c mt ngi s dng cao trong EDGE

c trin khai; cc vng cha c EDGE, MBMS c th cung cp theo ch

imtia im.

Truy nhp v tuyn broadcast/multicast UMTS

mng UMTS, MBMS ti s dng cc knh vt l v cc knh logic hin

ti. Thc t UMTS yu cu ba knh logic mi v mt knh vt l cho MBMS,

l:

- Knh iu khin im-ti-a im MBMS (MCCH): Knh logic truynti thng tin v cc phin MBMS hin ti v cc phin MBMS mi;

- Knh lu lng im-ti-a im MBMS (MTCH): Knh logic truyn tid liu ng dng MBMS thc s;

- Knh nh trnh im-ti-a im MBMS (MSCH): Knh logic cung cpthng tin v d liu c nh trnh trn knh MTCH;

- Knh ch th thng bo MBMS (MICH): Knh vt l c s dng thng bo cho thit bu cui v thng tin MBMS kh dng trn knh

MCCH.

Ba knh logic MCCH, MSCH, v MTCH ti s dng knh truyn ti

FACH (knh truy nhp hng i) v knh S-CCPCH (knh vt l iu khin

chung th cp). Lp RLC v MAC ti s dng phn ln cc gi giao thc hin

ti ca UMTS.


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Tc d liu MBMS c th ln ti 128 kbps i vi mi phn mang

GPRS v 256 kbps i vi UMTS. MBMS trong mng truy nhp GERAN c th

s dng ti 5 khe thi gian trong ng xung cho mt knh MBMS n. Ph

thuc vo s iu ch v vic nh cmng, tc knh c tht c t32 kbps ti 128 kbps. Hai su ghp xen (TTI) c s dng trong MBMS cho

knh MTCH l: 40 ms v 80 ms. S la chn su ghp xen TTI di cung cp

tng ch phn tp ln trong min thi gian, do ci thin cht lng tn hiu

thu v tng tc truyn dn. Vi cng ngh UMTS MBMS, mt sng mang 5

MHz c th h tr16 knh MBMS im-ti-a im tc bit ngi s dng

64 kbps trn mi knh. K thut phn tp thu anten, k thut thu tin tin nh G-

RAKE ci thin ng kdung lng knh trn mi sng mang t bo.

Truy nhp v tuyn broadcast/multicast CDMA2000

Ging nh UMTS, CDMA2000 s dng cc knh vt l hin ti c

nh ngha cho IS-2000 (1x) v IS-856 (1xEV-DO). b li vic khng c giao

thc truyn dn li lin kt v tuyn trong chim-ti-a im (khng c

PDAN), CDMA2000 s dng thm mt lp m sa li bn trn lp m hin ti,v c p dng trong mng truy nhp v tuyn, cho php kt hp ti u hai lp

gii m my thu. M l mt m trn c cc hng cu thnh nn cc khung hin

ti v kiu m l m Turbo, mt tp cc m Reed-Solomon tri di cc ct, mi

ct c rng 1 octet. Ma trn c k hng mang thng tin, m Reed-Solomon tri

di cc ct thm vo n-k hng. Tt ccc hng c m ho ring l bng m

Turbo v c pht ti my thu, my thu s kt hp mm cc tn hiu BCMCSt nhiu trm gc. phc tp thm vo ca lp m mi v phc tp lin

quan n vic x l dng d liu media c th lm gim tc bit. Do , tc

bit ngi s dng u cui BCMCS tng tnh tc bit MBMS UMTS.


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2.1.4 Kin trc in hnh h thng Mobile TV qua mng 3G

Hnh 2.5 Kin trc h thng cung cp tn hiu Mobile TV qua mng 3G.

Hnh 2.5 m t kin trc in hnh h thng truyn tn hiu Mobile TV

qua mng 3G. Trung tm dch v broadcast/multicast (BM-SC) l mt phn t

logic c nh ngha bi 3GPP. Trong thc t, chc nng ca BM-SC c

phn chia bi mt s phn t vt l. TV server l im giao tip u tin gia

thit b u cui v n viu khin trung tm ca dch v truyn hnh di ng.

Khi ESG (hng dn dch vin t) phin dch v kt hp thng tin chng

trnh t cc nh cung cp ni dung v chn thng tin ny vo ESG.

Biu khin media phn phi cc dng ni dung ti cc thit bngis dng UE theo ch unicast v broadcast. B mt m ho thc hin mt m

cc dng broadcast di s gim st ca chc nng bo v truy nhp dch v

SAP. Cc dng unicast khng yu cu chc nng bo v truy nhp ny, v cc c

ch bo mt unicast theo chun 3G c p dng.

B iu khin broadcast thit lp v gii phng cc phn mang MBMS

qua mng li v mng v tuyn.


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B m ho tn hiu trc tip, podcast TV, v cc server pht tn hiu TV

theo yu cu s thc hin m ho ni dung TV theo khun dng ph hp vi cc

thit b di ng v ng gi khun dng ny theo cc giao thc c thng dng

thc hin phn phi. Server tng tc to ra cc ti liu tng tc. Bsu tpphn hi s x l cc phn hi tngi s dng.

2.2 MobileTV s dng cng ngh DVB-H

2.2.1 Khi nim DVB-H

DVB-H l tiu chun cng ngh truyn hnh k thut s cho cc thit b

cm tay c ra i ti chu u vo nm 2002. Cng ngh ny cho php truynti ng thi nhiu chng trnh truyn hnh, pht thanh hay d liu IP (Internet

Protocol) khc nhau ti nhng thit b cm tay di ng nh: in thoi di ng,

PDA,....

DVB-H c xem nh l mt phn m rng ca DVB-T bi v tiu

chun DVB-H c xy dng da trn tiu chun truyn hnh k thut s mt

t DVB-T hay ni cch khc chun DVB-T c thm vo mt sc imcn thit h trchdi ng v ch tit kim ngun cho cc thit b s

dng ngun nui l pin m bo thu tn hiu tt trong mi trng di ng.

DVB-H tp trung vo cng ngh lp vt l, ng gi c s dng ti lp

lin kt d liu v k thut IP c s dng ti lp mng. C th lp vt l s

dng cng ngh OFDM cho giao din khng gian v cng ngh tit kim ngun

cho my thu. OFDM l s la chn ng n cho giao din khng gian truynhnh di ng v cng ngh ny gip min nhim vi cc ngun nhiu a ng

v s dng ph tn s hiu qung thi lm vic hiu qu trong mng n tn.

DVB-H s dng ct lt thi gian biu chnh c th tt trong hu ht thi

gian v ch bt trong cc cm truyn ngn. iu ny cho php biu ch nh lm

vic trn bng thng u vo nhv cng tit kim ngun tiu th ln ti 90-

95%.


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2.2.2 Cu trc v hot ng ca h th ng DVB-H

DVB-H da trn c s truyn ti c s IP. Video c truyn ti s

dng tn hiu m ho video MPEG-4/AVC (H.264), c th cung cp tn hiu m

ho QCIF 384kb/s hoc t hn. C nhiu b gii m c th hot ng trn tnhiu truyn hnh thi gian thc v cung cp tn hiu m ho MPEG-4/AVC

u ra di nh dng IP. V da trn truyn ti IP, DVB-H c th h trm ho

m thanh v hnh nh khc ngoi MPEG-4/AVC. Vc bn l mt truyn ti IP,

n c th h tr mi loi lung AV. Ngoi MPEG-4, nh dng m ho

Microsoft VC-1 l c sp t trong tiu chun DVB-H. phn gii v kch

ckhung c thc la chn bi nh cung cp dch v tho mn cc mctiu tc bit. D liu sau c pht i bng mt IP datacast (Hnh 2.6).

Hnh 2.6 H thng truyn dn truyn hnh di ng DVB-H

Trong mi trng DVB-H in hnh mt slng cc dch v m thanh

v truyn hnh c thc m ho bi mt dy cc b m ho. Tt c cc b m

ho c kt ni bi b chuyn mch ti bng gi IP(IP encapsulator), sau

c kt hp tt c cc dch v m thanh v video cng nh tn hiu PSI v SI


38/88



v d liu EPG thnh cc khung IP. Bng gi IP cng cung cp d liu knh

c sp xp vo cc khe thi gian sao cho my thu c th vn tch cc trong

sut thi gian d liu la chn knh tch cc truyn vo khng gian (Hnh

2.7).

Hnh 2.7 DVB-H IP Datacasting

Bng gi IP cng cung cp nhiu m sa li, cc m ny c th cung

cp cc tn hiu ng tin cy trong mi trng di ng tiu chun. Tc d liu

ti u ra ca mt bng gi IP trong DVB-H ni chung ph thuc vo kiu

iu ch cng nh s sn sng bng thng. Thng thng th mt knh ghp

DVB-H s c th c tc d liu l 11Mb/s, khi c iu ch s to thnhmt di sng mang rng 7-8MHz. So snh vi mt knh ghp 21Mb/s cho dch

v DVB-T trong bng VHF. Tc truyn dn ca DVB-H c hiu sut thp

hn v l do chp nhn sa li mc cao truyn dn mnh hn trong mi

trng cc thit b cm tay.

u ra ca bng gi IP nh dng ASI, sau c iu ch bi b

iu ch COFDM vi 4K (hoc 8K) sng mang. Biu ch COFDM cung cp


39/88



sn hi cn thit chng li fading chn lc (selective), v cc iu kin lan

truyn khc. Tiu chun DVB-T cung cp cho sng mang 2K n 8K trong iu

ch COFDM. Ch 4K c d nh dng cho DVB-H v 2K sng mang

khng a ra ch bo v thong chng li fading chn lc tn s v ncng cung cp kch thc nhhn bi v yu cu khong bo v trong mng

n tn (SFN). ng thi ch 8K sng mang c slng sng mang dy c

v cc tn s qu gn i vi dch tn Doppler, chng rt quan trng i vi cc

my thu dch chuyn. Do , ch mi 4K sng mang kt hp cht chnh l

phn thit yu trong tiu chun DVB-H. Ch4K dung ho tt hn gia cc

kch thc v hiu ng Doppler do di chuyn. Mt b chn k hiu 4 K cng

c s dng trong qu trnh iu ch. Tuy nhin, cn nhn bit rng ch

sng mang thc t c ph thuc vo bng tn trin khai, v dbng UHF

hoc bng L. iu ch cho mi sng mang trong tp hp cc sng mang c th

vi iu ch QPSK, 16QAM, hoc 64QAM.

Tiu chun DVB-H khuyn nghcho iu ch COFDM, n ph hp cho

cc SFN. H thng s dng cc ng h thi gian da trn GPS v nhn thi

gian m bo rng tt c cc my pht trong mt vng c th vn hnh duy tr

c chng b thi gian, rt cn cho SFN. iu cng bao hm ngha l cc

b lp c thc s dng trong vng ph ti cng tn s v cc b lp cung

cp thm cng tn hiu ti cc my thu ti my di ng.

2.2.3 Cc cng ngh ca DVB-H

2.2.3.1 Thnh phn chc nng ca m hnh pht dliu DVB-IP

DVB-H dng pht d liu IP (tham chiu ti IPDC). Qu trnh bao hm

ng gi ni dung svo cc gi IP v sau chuyn cc gi ny trong mt b

th tc ng tin cy. Nn tng IP khng hn ch cc kiu ni dung do n c

th ti v v vy IPDC ph hp cho video trc tip, ti video xung (qua truyn

file), cc file nhc, lung m thanh v video (theo nh dng lung), trang web,

tr chi hay nhiu loi ni dung khc.


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So vi cc mng unicast IP th IPDC cung cp cc u im ni bt v cc

mng qung b c thvn ti hng nghn u cui (khng hn ch sngi

dng) v tc c nng cao, lun sn sng cho tt cngi dng.

Dng IP nh cng ngh c sc u im l d liu trong ni dung c

thc gim st cng chung cc giao thc ph bin trn Internet, cc thit b

khng t v cc k thut qun l sn sng. Mi trng truyn dn cng c

lp vi kiu ni dung ang c vn chuyn. Cc kiu ni dung c th l truyn

hnh trc tip, cc file m thanh v video hoc cc trang Web HTML/XML.

D liu c pht qung b bao gm hai loi ni dung qung b v

m t dch v, nh d liu PSI/SI v hng dn dch vin t. Ngoi ra d liu

cng bao gm thng tin qun l bn quyn truy cp v thu bao ni dung.

Lp IP cung cp cc socket m qua thng tin ca mi loi c pht i.

2.2.3.2 Ct lt thi gian (Time Slicing)

Mt trong nhng c im phn bit DVB-H vi DVB-T l c

im ct lt thi gian ca cc d liu knh trn on ghp cui cng. Trong

trng hp DVB-T, nhiu knh sc ghp vi nhau (v d 6 hoc 8 dch v

trong mt knh ghp 8MHz). Tuy nhin mc ghp knh, cc gi cho cc knh

khc nhau lin tip nhau. V kt qu ca tc b bt rt cao, my thu cho mi knh

cn hot ng trong ton b thi gian v cc gi s ti lin tc.

Trong trng hp DVB-H, b ng gi IP a ra kh nng y ca

vic ghp knh trong mt thi gian gii hn cho mt knh duy nht. Do cc

gi cho knh ny c th ti theo tng chm, chm ny sau chm kia, trong sut

thi gian ny. Trong khi khe ny c cp pht cho knh ny th khng c gi t

cc knh khc. iu ny cho php my thu, nu n ch cn mt knh, hot ng

trong sut thi gian cc gi cho knh ny c nhm li vi nhau (v d trong

sut khe thi gian c ch nh cho mt knh ring c th). Vo nhng thi

im khc, my thu (tuner) c thc tt duy tr ngun. N phi c bt

ngun tr li trc khi khe c chnh ti theo chu trnh (trong thc t cn


41/88



200ms cho ng b). Cho php my thu di ng trong ch tit kim nng

lng thi gian thu tn hiu ln ti 95% ph thuc s lng dch v c

ghp. Trong hng mc thi gian, d liu c khong thi gian t 1-5s c vn

chuyn bng mt chm duy nht. Nu tc knh d liu l 1Mb/s (ly lm vd) my thu s phi cn 5Mbit b nhm cho thi gian 5s khng hot ng.

Nh mt s la chn, cho mt dch v TV chy 25 khung hnh/s, my thu cn

b nhm 125 khung d liu. Cc khung c lu trong b nhm ny c

hin thbnh thng v ngi dng khng nhn bit c my thu ang khng

hot ng (Hnh 2.8).

Hnh 2.8 Ct lt thi gian trong DVB-H

Tng s d liu c truyn trong mt chm bng mt khung FEC, c th

t 1-5 Mbit. Khi my thu khng thu cc chm mong mun ca d liu, thit b

iu hng nm trong my cm tay s khng hot ng v v th s dng t nng

lng hn.

Tuy nhin c nhiu s la chn dng cc khong thi gian khng hot

ng. V d my thu c tho ln tn hiu t cc b lp gn ti cc b lp

khng phc v chuyn giao ti cc my pht hoc b lp thch hp hn.


42/88



N c th xp cc dch v c ct lt thi gian (v d: DVB-H) v khng c

ct lt thi gian (v d: DVB-T) trong cng mt b ghp knh.

2.2.3.3 Thi gian chuyn gia cc knh v cc bit bo hiu tham s my

pht (TPS)

Mt trong nhng vn ny sinh do my thu ang ch tit kim

nng lng l thi gian cn chuyn knh truyn hnh trn my di ng.

gim thi gian tm kim v cho php "pht hin dch v nhanh", cc bit bo hiu

ca lung DVB-T cng mang thng tin v lung DVB-H. Khung bo hiu

DVB-T bao gm 68 bit TPS trong ch c 23 bit dng cho cc tham s DVB-

T. Khi DVB-H c ti trn cng mt knh ghp, mt sbit TPS khng c sdng c dng mang thng tin v DVB-H.

Cc bit TPS thm vo trong lung bo hiu gip tr li knh mi c

chn nhanh hn cng nh chuyn giao trong trong mi trng di ng, my thu

DVB-H hiu c trng thi ca ton b lung pht.

2.2.3.4 MPEFEC

Qu trnh thu cc thit b cm tay rt khc vi qu trnh ny cc ng

ten thu sng mt t cnh:

- Th nht, t bn thn ng ten rt nh v c h stng t thp.- Th hai, thit b cm tay trong mi trng di ng, tn hiu thu c c

th tri qua sdao ng mnh v cng sut thu.

Mc d lp vt l mnh s dng truyn dn OFDM lm fading chnlc gim bt nh hng, v d s dng cc mng n tn v cc tn hiu thu

c tng cng t tt c cc ngun phn x v trc tip th vn cn ti mt qu

trnh bo v bsung di dng chun ho li chuyn tip.

D liu m thanh v hnh nh trong mt mi trng DVB-H c pht i

bng IP datacasting. C ngha rng d liu c ng gi vi cc tiu IP v

c pht ging nh n c truyn qua qua Internet. Tuy vy, mi trng v


43/88



tuyn khng thn thin nh Internet v phi chu mt t l li cao do sthay i

cc mc tn hiu, nhiu v cc hiu ng truyn dn khc. Do d liu cn c

bo v tt.

Bo v d liu c thc hin trong trng hp DVB-H s dng cng

ngh sa li chuyn tip. Cc bng gi IP thc hin thm cc chc nng ca

MPE-FEC. FEC c thc hin mc lin kt (v dtrc khi d liu c m

ho). Cn bit rng DVB-H s dng lp vt l ca DVB-T (c ngha iu ch

COFDM). COFDM rt vng chc v cung cp thu tt ngay c di iu kin

truyn dn a ng. MPE-FEC cung cp mc bo v xa hn v trn c

COFDM.

Hnh 2.9 Cu trc khung MPE-FEC

D liu n t bm ho c t vo khung FEC, khung FEC sn sng

vi s dng m RS(255,191). Khung bao gm 1024 hng. Mi hng c 191 ct

(mi ct l mt byte) d liu IP v 64 ct d liu FEC t cc mu tng ng

cc byte. Nh vy mi hng i din cho 191 byte d liu IP, d liu ny c

chuyn i b sung thnh phn sa li chuyn tip thnh 255 byte. Nu 1024

hng c dng trong khung, th mt khung bao gm 191KB d liu IP v


44/88



255KB d liu c pht. N cng c biu din nh 1,528 Mbit d liu IP v

2,040Mbit d liu pht.(Hnh 2.9)

Vi mt b m ho chy tc 384kb/s (48kByte/s), mt khung FEC c

th mang 3,97s d liu, n c pht nh mt chm. N bo gm khong 100

khung tc m ho 25fps. Vic s dng FEC lm gim t s tn hiu trn

nhiu cn thit thu tn hiu vi h s ln ti 7dB, a ra khnng phc hi

ng k cho cc thit b cm tay trong vic thu tn hiu truyn dn DVB-H.

2.2.4 Kin trc mng

Tiu chun DVB-H c thit k mt mc cho php khai thc h

thng truyn hnh qung b mm do vi nhiu cu hnh c th cng vi cc

mng truyn hnh sang c sn hoc lp t mi. Khi truyn dn DVB-T i

km vi cc ng ten tng i ln trn mi nh th DVB-H li cn phi tip cn

ti cc ng ten rt nhtrong mi trng di ng. C mt yu cu na l

truyn dn c bn trong cc to nh. Bi v cc yu t ny, cng sut pht x

ng hng c ch (EIRP) cn phi cao hn rt nhiu cho h thng DVB-H.

Cng sut pht cng ph thuc vo chiu cao ng ten.

V d, nu EIRP yu cu cho mt my di ng vi ngng cng sut ti

thiu -47dB trong phm vi 5km l 46dBm (P=20W) cho ng ten c chiu cao

120m, th vi ng ten c chiu cao l 25m s yu cu xp x 70dBm EIRP

(P=10kW).

2.2.5 Truyn dn DVB-HCng ngh DVB-H c thit k dng chung h tng DVB-T c sn,

h tng ny c trin khai cho truyn hnh s. Hn na vic dng chung

mng DVB-T dn n xem xt c bit trong khung c s cc yu cu k

thut.

DVB-H c thc vn hnh di 3 cu hnh mng sau:


45/88



- Mng dng chung DVB-H (dng chung b ghp MPEG-2): Trong mtmng dng chung DVB-H cc knh truyn hnh di ng sau IPE (bng gi

IP) chia s b ghp DVB-T vi cc chng trnh TV mt t s khc. Cc

chng trnh truyn hnh s mt t sc m ho dng MPEG-2, trong khicc chng trnh truyn hnh di ng c m ho MPEG-4 v IPE. B ghp

knh kt hp chng vo mt lung pht duy nht, sau lung ny c pht i

sau iu ch (Hnh 2.10).

Cc b m haMPEG-4/AVC

MPEMPE

FECTime

Slicing

MPEG-4

AVC

MPEG-2

MPEG-2

MUX

2

K

4

K

8

KB ng gi IPDVB-H

My ch lungVideo, m

thanh

Truyn hnhtrc tip

IP

Dch vMPEG-2 TV

MPEG-4 TV

Ghp DVB-T

My pht

B iu ch DVB-T

DVB-H

TPS

Hnh 2.10 DVB-H trong ghp knh dng chung

- Mng phn cp DVB-H (chia s mng DVB-T theo phn cp): Trong mtmng phn cp, iu ch phn cp vi 2 lung: DVB-T v DVB-H, chng to

thnh mt phn ca u ra biu ch (Hnh 2.11 miu t chia s mng theo

phn cp). DVB-T c iu chnh lung c quyn u tin thp, DVB-H l

lung c quyn u tin cao. Trong trng hp quyn u tin cao, iu ch vng

chc hn (chng hn nh QPSK) v i lp vi u tin thp hn c th l

16QAM. Phng thc iu ch "mt " thp hn mang li khnng bo v cao

hn chng li li v iu ch mt cao hn mang li khnng chng li thp

hn.


46/88



- Mng chuyn dng (dnh ring) DVB-H: Sng mang DVB-T c sdng dnh ring cho truyn dn DVB-H. Trong mt mng chuyn dng, sng

mang COFDM sc dng ring bi truyn hnh di ng, cc knh m thanh

nh l mt IP datacast vi v bc MPEG-2. Cc mng chuyn dng thngc s dng bi cc nh khai thc mi-nhng nh khai thc khng c mng

qung b mt t (Hnh 2.11).

Hnh 2.11 Cc mng n tn sDVB-H

2.2.6 Mng my pht DVB-H

Cc hng dn thc thi DVB-H cho mt my thu tham chiu (ETSI 102

377) v phc v cho thit k h thng. Thit k quy nh t s C/N l 16dB.

Vng phtrong nh thng thng cn xem xt suy hao truyn dn l 11dB hochn. p dng cc tham s thit k, mt thnh phc rng nh Paris hay New

Delhi thng s yu cu 17-20 my pht.

Ph thuc vo yu cu vng ph sng, cc h thng DVB-H c thc

thit k theo mng n tn s hoc mng a tn s.

Cc vng rng ln (mt thnh ph hay vng xung quanh 50 km theo bn

knh) c thc ph sng bng cch s dng mt SFN. SFN bao gm mt s


47/88



cc DVB-H, mi c mt my pht v mt s b lp. My pht thu tn hiu

dng mt lung pht MPEG-2, ngun gc t IPE (Hnh 2.18). Mt mng IP

c dng phn phi tn hiu ti cc my pht trong vng quy nh. Tt c v

tr my pht nhn c cng mt tn hiu, vi thi gian c gn tem ng hGPS. Ti mi v tr my pht biu chCOFDM ng b tn hiu bng vic

tham chiu thi gian GPS sao cho tt c cc my pht pht tn hiu ng nht

v thi gian m khng quan tm ti v tr a l ca chng. Slng b lp

c thtng ln dng cho thu tn hiu trong nh, t dn n thut ng SFN

dy c. Hnh 2.12 m t cc khong cch tng i SFN in hnh.

100km

(8K

Mod

e)

50km(4

KMode

)

23km (2K mode)

DVB-H

Hnh 2.12 Khong cch tng i SFN. Tt c khong cch trn c siu ch

16QAM vi khong bo v cho COFDM

Khi yu cu vng ph sng rng (v d c mt vng lnh th, kch thc

vi trm km2), ngun tn hiu t mt IPE duy nht l khng thc t do c thi

gian tr trong vic cung cp tn hiu cho tt cmy pht. Trong trng hp nh

vy, cc my pht ngoi mt khong cch nht nh s dng cc tn s khc.

Da trn cu hnh ny, cn ti nm hoc su khe tn s ph sng quc gia.

Trong trng hp ny, thng phn pht tn hiu thng qua mt v tinh sao cho

hng trm my pht c thc ph sng, k c cc vng xa xi.


48/88



2.2.7 u cui v cc thit b cm tay

DVB-H cung cp mt cng ngh qung b thnh cng tn hiu truyn

hnh trc tip bng vic m ho ni dung v pht cc gi IP sau khi p dng

FEC. Tuy vy, thit bu cui thu l in thoi di ng (chng hn Nokia N92),chng cn h trng ten thu cn thit thu tn hiu. Biu ch nh cng hng

mt chip v b m ho DVB-H cung cp mt cch thc hiu qu thu TV di

ng trn my cm tay vi iu kin cc my cm tay c trang b thm mt

ng dng TV ngoi cc chc nng thng thng thoi v d liu s dng trong

mng 3G. DVB-H v vy khng phi l mt cng nghtrong bng nh MBMS.

Cc my thu DVB-H trong hu ht cc in thoi di ng c mt knh hi

tip qua cc mng 2G hoc 3G, y l im khc bit so vi cc my thu qung

b thng thng khc. C ngha cc nh khai thc qung b c th s dng cc

thuc tnh ny c thm iu khin qua vic bn cc chng trnh qung b,

bo v ni dung v qun l bn quyn s. S cn thit kt hp nhng thuc tnh

ny dn ti cc cch tip cn khc nhau i cht phm vi bo v ni dung hoc

gim st tng tc knh hi t ip. Cc tip cn khc nhau ny c phn nhtrong cc hs ghi nhv l mt vng ca hi t cc tiu chun trong tng lai.

2.3 MobileTV s dng cng ngh T-DMB

2.3.1 Gii thiu

Cng ngh qung b a phng tin s mt t (T-DMB) l ng dng ca

DMB cho mng mt t. T-DMB c pht trin da trn cng ngh qung b

m thanh s (DAB) ca EUREKA-147. So vi EUREKA-147 DAB, T-DMB c

s ci t in bng ng dng MPEG-4 phn phi cc dch v truyn hnh cht

lng cao ngay ctrong trng hp ngi dng di chuyn vi tc ln. Hn

na, T-DMB nng cp hon thin cc tiu chun d ch v d liu ca EUREKA-

147 v b sung cc cng ngh mi nh l MPEG-4 BIFS, Middleware, cng

ngh t hp ca mng qung b v khng dy


49/88



T-DMB c trin khai u tin Hn Quc vo nm 2005. i vi

nhiu ngi, DMB l cng nghu tin c thng mi ha, c s hi t

ca cc dch v vin thng v qung b di ng. T-DMB c s dng pht

qung b cc dch v pht thanh, truyn hnh v d liu. M hnh dch v truynhnh di ng trin khai trn nn cng ngh T-DMB c m tnh trong hnh

2.13.

B mha m

thanh ER- BSAC

M xonan xenthi gian

B mha RS

(204,188)

B mha hnh

nhH.264

MUSICAM

MOT, BWS

Dch v pht thanh

Dch v d liu

Ch lung hocch gi

Pht sng T-DMB

D liu tng tc

m thanh

Hnh nh

Bghptheothigian

MUXDAB

iuch

OFDM

Hnh 2.13 M hnh dch v truyn hnh di ng trn nn cng ngh T-DMB

Cc lung tn hiu hnh nh, s liu v m thanh c m ha thnh cc

lung d liu, a v bghp knh DAB, iu ch ghp knh v gi ti anten

pht qung b ti thu bao ngi dng. Cc chng trnh c pht tc 1

1,5 Mbps trn cc knh tn sc rng bng tn 1,536MHz. DMB dng cng

ngh truyn dn DAB do tn hiu c pht trong di phin t rng ln t30MHz n 3GHz. Tuy nhin trong thc t th phn ln cc h thng T-DMB

ch s dng tn s trong bng III (174 240 MHz) v bng L (1452 1492

MHz). Trong chun T-DMB, t lBER c khuyn co l 2.10-8m bo

cht lng thu hnh nh mi gi truyn ti MPEG-2 TS c b sung thm m

sa li vo tn hiu video trc khi truyn i.


50/88



Mng truyn hnh di ng DMB bao gm mng cc my pht, chng hot

ng hoc nh mt mng n tn hoc nh mt mng a tn. Hu ht cc mng

n tn DMB chim gi cc knh tn strong bng III v mt my pht sng c

tht c bn knh ph sng ln ti 100km.

2.3.2 M ha knh T-DMB

Trong h thng T-DMB, tt c cc lun d liu s c m ha theo

phng thc m ha xon (convolutional coding). M ha xon thc hin nh x

n bit u vo thnh m bit u ra (m > n). Cc bit u ra c to thnh bng cch

tnh tch chp cc u ra ca cc thanh ghi dch phn hi tuyn tnh theo mt

cch no . My thu s dng thut ton Viterbi gii m dng d liu vo. T

l gia sbit u vo v u ra bm ha c gi l t l m (R=n/m). T l

m cng thp th khnng sa li cng cao, nhng khi tc d liu knh li

thp. Do cc tiu chun DAB/DMB s dng mt t l m ph hp vi mc

nhiu ca mi trng truyn dn.

C th thy b gii m Viterbi rt hiu qu trong vic pht hin v sa li

bit n. Tuy nhin, mi trng truyn dn v tuyn thng xuyn chu nh

hng ca li cm (li chm) tc c nhiu bit lin tip b li. Do , h thng

DAB/DMB thc hin ghp xen theo thi gian phn tn li. Dng d liu c

chia thnh cc tm c di cnh, cc bit lin tip ca mt tm c hon

i vi cc bit ca cc tm ng trc v c tm ng sau theo mt thut

ton no . my thu, dy bit ban u c khi phc nhqu trnh gii ghp

xen.

Nhc im ca ghp xen theo thi gian l gy trmy thu v my thu

phi i ti khi thu c tt c cc bit cn thit thc hin gii ghp xen nhm

khi phc li dy d liu ban u. Tr ny c th ln ti hng trm ms. Mc d

tr ny khng l vn vi hu ht cc dch vDAB/DMB nhng tr l qu ln

i vi vic truyn dn thng tin iu khin nhy cm vi thi gian c truyn


51/88



ti trn knh thng tin nhanh (FIC) khng s dng ghp xen theo thi gian. Knh

ny s dng s m xon c khnng chng li tt hn cc knh khc.

Ngoi ra trong m ha T-DMB cn a ra mt phng thc sa li

c chun ha. Cc dng d liu ca dch v DMB video s dng thm m ha

khi (m ngoi) trc khi m ha xon my pht v gii m khi sau khi gii

m xon my thu tng khnng chng li trn knh nhm phc vngi s

dng di chuyn tc cao vi cht lng chp nhn c. C th dng d liu

video MPEG-2 c chia thnh cc khi c di 187 byte. i vi mi khi,

mt m Reed Solomon c to ra v c gn km khi tng ng nh l mt

t m chn lc di 16 byte. Phng php ny cho php sa c ti 8 byteb li trn mt khi. Cc khi lin tip v cc t m chn l kt hp sau c

ghp xen theo thi gian phn tn li cm.

2.3.3 Ghp knh

B iukhin ghp

knh

B to tnhiu

OFDM

Ghp xentn s

Ghp xenthi gian

Ghp xenthi gian

Ghp xenthi gian

M xon

M xon

M xon

M xonGhp xenthi gianM khi

Dch vvideoDMB

m thanhDAB

Dch vd liu

BghpknhMSC

Bghpknh

khungtruyn

dn

A/D v

M ha ngun

M ha knh Ghp knh

Thng tin cu hnh ghp knh(MSC)

iu khin

iu ch v truyn dn

Hnh 2.14 Chui truyn dn DAB/DMB

C dng d liu c ghp xen theo thi gian ca cc dch vc kt

hp thnh dng truyn ti chung nhqu trnh ghp knh. Ghp knh c t

chc thnh cu trc khung nh Hnh 2.14.


52/88



Trc tin cc dng d liu c lp c kt hp b ghp knh MSC.

Sau b ghp knh MSC thc hin ghp knh d liu knh thng tin nhanh

FIC vi knh d liu chnh MSC. Thng tin ca biu khin ghp knh cng

c m ha xon mt cch c lp vi mi dng d liu chn mt tc mph hp.

V tr ca mt knh con trong khung truyn dn c thng bo ti my

thu bng thng tin cu hnh ghp knh MCI. Do my thu ch cn thu v gii

m cc knh con m n quan tm v khng kch hot trong thi gian thu cc

knh con khc, iu ny lm gim cng sut tiu th ca my thu (my thu s

dng k thut ct lt thi gian nhm tit kim pin). V dnh khung truyn dngm 4 knh truyn hnh di ng m ngi s dng ch quan tm ti 1 knh no

, th my thu ch kch hot trong thi im thu knh truyn hnh v khng

kch hot trong 3/4 thi gian cn li.

2.3.4 iu ch v ghp xen tn s

Hnh 2.15 iu chmt sng mang sdng DQPSK trong DMB

Cc khung truyn dn c to ra nhqu trnh ghp knh c iu ch

trn cc sng mang con ca knh v tuyn OFDM. H thng DAB/DMB s

dng s iu ch kha dch pha vung gc vi sai (DQPSK), trong pha ca

mi sng mang con c dch ph thuc vo k hiu c pht. Bn k hiu

00, 01, 11 v 10 c nh x cho cc dch pha 0o, 90o, 180o v -90o. i


53/88



vi mt k hiu c pht, pha ca mi sng mang con c thay i theo dch

pha tng ng v ph thuc vo pha ca k hiu trc (Hnh 2.15)

khc phc nh hng ca li cm xy ra khi nhiu tri ra qua mt s

sng mang con ln cn, h thng DAB/DMB s dng k thut ghp xen theo tn

s, tng tnh ghp xen theo thi gian. Cc khung truyn dn c chia thnh

cc k hiu OFDM, mi k hiu gm N sng mang con, tng ng vi N k

hiu DQPSK. Cc k hiu DQPSK khng c nh x thnh chui ti cc sng

mang con m c trn theo mt thut ton no theo cch m cc k hiu

DQPSK lin tip khng c pht trong cc sng mang con ln cn. Hnh 2.22

m t trng hp ghp xen theo tn s i vi mt knh v tuyn OFDM sdng N=8 sng mang con.

Hnh 2.16 Ghp xen theo tn s

2.3.5 Cc ch truyn ti ca DMB

Nh trn, knh v tuyn DAB/DMB c bng thng 1,536MHz v t tc

d liu t 15 Mbps ty thuc vo cc t l m xon c s dng cho cc

dng d liu khc nhau, bn knh ph sng ca mt my pht DAB/DMB n c

th ln ti 100km. Vn ch yu khi pht d liu tc cao qua khong cch

ln l tn hiu d btc ng ca nhiu. Cc nh hng quan trng khi truyn

dn tn hiu trong mi trng v tuyn di ng gm : hiu ng a ng, tnhao, tp m, bng rm gy bi cc ta nh v d ch tn Doppler khi my thu


54/88



chuyn ng. Mt trong nhng nguyn nhn quan trng gy ra li truyn dn i

vi DAB/DMB l hin tng xuyn nhiu gia cc k hiu (ISI). khc phc

nh hng ca ISI v s dng bng tn hiu qu, DMB s dng k thut ghp

knh phn chia theo tn s trc giao (OFDM).

H thng DMB cung cp 4 ch truyn dn, khc nhau v s sng mang

con trong knh c bng thng 1,536 MHz, v khong thi gian tn ti cc k

hiu v di khung truyn dn. Vic la chn s dng ch no ph thuc

vo loi truyn dn (mt t hay v tinh), di tn sc phn b v loi hnh

khu vc ph sng (nng thn hay thnh th). Nu truyn dn mt t T-DMB

c s dng th cn phn bit gia cc mng n tn SFN v cc mng a tnMFN. Bng 2.1 m t cc tham stng ng vi 4 ch truyn dn.

Bng 2.1 Cc tham svi 4 ch truyn dn T-DMB

Ch I Ch II Ch III Ch IV

Mng SFN MFNCp hoc v

tinh

Mt t hoc

v tinh

Di tn s174216

MHz

14521467

MHz< 3GHz

T : 1452

1467 MHz

S : 1467

1492 MHz

Khong cch 96 km 24 km 12 km 48 km

S sng mang

con 1536 384 192 768

Khong cch

gia cc sng

mang con

1 kHz 4 kHz 8 kHz 2 kHz

Thi gian

symbol1ms 250s 125s 500s


55/88



Thi gian

khong bo

v

246s 62s 31s 123s

S bit/symbolOFDM

3072 768 384 1536

Thi gian tn

ti khung96ms 24ms 24ms 48ms

Cc ch c s sng mang con nhiu v di k hiu ln c la

chn cho cc mng bao gm cc my pht DAB/DMB c khong cch ph sngln, v trong cc mng ny tn hiu c tri tr ln v b ISI ln. Cc ch ny

c bit ph hp vi cc mng SFN, trong my thu cn thu c c tn hiu

t cc my pht ln cn. Trong nhng trng hp , h thng DAB/DMB nn

s dng ch truyn dn I c 1536 sng mang con, khong cch gia cc sng

mang con l 1kHz, di k t l 1ms. Trong cc mng m tn hiu c tri tr

nhhn, cc ch c ssng mang con t hn v di k hiu nhhn nnc s dng, v dnh truyn dn v tinh c th s dng ch II, 192 sng

mang con v di k hiu l 125s. ISI c khc phc hn na bng cch s

dng cc khong bo v gia cc k hiu lin tip.

2.4 Cng ngh MediaFLO

2.4.1 Gii thiu

Cng ngh MediaFLO (ch c lin kt hng i t mng ti thit b) l

h thng multicast a phng tin di ng mt t c pht trin bi hng

Qualcomm. MediaFLO c thit k c th pht multicast hiu qu v kinh t

ni dung a phng tin ti hng triu ngi s dng ng thi. Cng ngh

MediaFLO khng h trstng thch vi cc h thng khc. C th lp vt l

FLO truyn dn cc bng tn VHF/UHF/L vi cc bng thng 5,6,7 v 8 MHz.

Do c sh tng mng v my thu FLO l hon ton ring r vi cc mng di


56/88



ng t bo. Lp vt l FLO c thit km bo c ch tit kim cng sut

tiu th, gim thiu thi gian chuyn knh trong khi li t c tng ch phn

tp thi gian v tn sthit bu cui di ng. Hn na, FLO cng c thit

km bo tnh linh ng trong vic trin khai h thng v t c hiu qus dng ph cao.

Cng nghMediaFLO c trin khai M(bng 700 MHz) v l cng

ngh qung b di ng cho cc dch v truyn hnh di ng trc tip ca hng

AT&T v Verizon Wireless.

2.4.2 Kin trc h thng FLO

2.4.2.1 M t h thng

text

text

1xEv

-DO

1xEv-DO

Multicast

3G

FLO

Server

H.264

WMV9

REAL

MPEG-4Near User 30 Fps

Encoders

Satellite

Distribution

Radio

AccessNetworks

Radio Networks Enhancement layer 30 fps

Basic Layer 15 fps

MediaFLO

clients

Far User 15 fps

Return Channel

Video

text

text

Hnh 2.17 Mng MediaFLO

Mt h thng FLO bao gm 4 phn : trung tm iu hnh mng, cc my

pht FLO, mng 3G v cc thit bu cui FLO.

Trung tm iu hnh mng bao gm trung tm iu hnh quc gia (NOC)

v cc trung tm iu hnh a phng (LOC). NOC thc hin tnh cc, phn

pht v qun l ni dung. NOC qun l cc phn t khc nhau ca mng v ng


57/88



vai tr l im truy nhp. NOC c th gm nhiu LOC phc vnh l im truy

nhp m t cc nh cung cp ni dung a phng phn pht cc ni dung a

phng ti thit bu cui di ng.

Cc my pht FLO thc hin pht tn hiu dng sng FLO ti cc thit b

u cui di ng trong vng phc v.

Cc mng 3G h trcc dch vtng tc cho php cc thit b u cui

di ng giao tip vi NOC ng k dch v v phn pht kha mt m

Cc thit bu cui c th thu cc dng sng FLO bao gm cc dch v

ni dung v thng tin hng dn chng trnh. FLO c thit k ti u cngsut tiu th qua s tch hp thng minh trn thit b v sphn pht c ti u

qua mng.

2.4.2.2 Phn pht ni dung

Trong mng FLO, ni dung biu din knh thi gian thc tuyn tnh (dng

truyn hnh thng thng) c thu trc tip t cc nh cung cp ni dung, in

hnh qua v tinh bng C vi khun dng MPEG-2 s dng thit bc shtng sn c. Mng FLO cng h tr phn gii QVGA (320240 pixel), s

dng nhiu kiu m ha ngun hiu qunh H.264, MPEG-4, Windows Media

v Real Video.

Ni dung phi thi gian thc c thu bi content server in hnh qua

ng lin kt IP, sau c to khun dng thnh cc dng gi FLO v c

phn pht li qua mng n tn SFN. Ni dung phi thi gian thc c phnpht theo mt lch trnh nh trc.

Ch c cc thit bu cui di ng ng k s dng dch v mi thu

c ni dung, ni dung c thc lu gi trn thit b xem sau . Ni

dung c th l cc file m thanh, video cht lng cao (QVGA) hoc cc dng

IP. Mng 3G cung cp chc nng iu khin, h trstng tc gia ngi s

dng v h thng FLO.


58/88



2.4.3 Kin trc phn lp ca MediaFLO

M hnh tham chiu giao thc MediaFLO c m thnh 2.24. c t

giao din khng gian FLO gm cc giao thc v cc dch vtng ng vi 2 lp

ca m hnh OSI l lp vt l v lp lin kt d liu. Lp lin kt d liu cchia thnh 2 lp con l lp con iu khin truy nhp mi trng (MAC) v lp

con Stream.

Hnh 2.18 Kin trc phn lp FLO

2.4.3.1

DATN (MobileTV)

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