Truyen Hinh Ve Tinh

8/10/2019 Truyen Hinh Ve Tinh

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Mn: Kthut pht thanh truyn hnh.

Nhm 12 :

L Anh Tun

Phm Vn T.

Nguyn V Trng.

ti: Tm hiu vTruyn hnh svtinh.

Ging vin: Ths. Nguyn ThThu Nga.


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Ni dung:

I. Khi nim.

1. Truyn hnh svtinh l g?

2. u nhc im.

II. Cu trc hthng truyn hnh svtinh, cc kthut c sdng trong THVT:

1. Trm pht mt t

2. Vtinh.

3. Trm thu tn hiu vtinh.

4. Kthut truyn dn sdng trong TH-VT

1. DVB-S

2. DVB-S2

III. Truyn hnh svtinh Vit Nam

IV.

Kt lun.


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I. Khi nim

1.

Truyn hnh svtinh l g?

Truyn hnh svtinh l mt hthng cung cp cc chng trnh truyn hnh s

dng tn hiu truyn tvtinh. Cc tn hiu c nhn thng qua mt ng-ten parabol

phn xngoi tri v mt bchuyn i khi c mc nhiu thp (Low-noise block

Converter: LNB). Mt my thu vtinh gii m cc chng trnh truyn hnh mong mun

xem trn TV. Truyn hnh vtinh cung cp mt lot cc knh v dch v, c bit l

khu vc a l m khng c truyn hnh mt t hay truyn hnh cp.

Cc tn hic pht sng trc tip qua vtinh c thl tn hiu tng tc, hoc cc

tn hiu kthut smi hn, chai u i hi thit bthu tng thch.Tn hiu kthut sbao gm truyn hnh nt cao (HDTV). Mt sknh truyn hnh min ph,

cn li nhiu knh khc mt ph i hi thu bao.

2. u, nhc im ca truyn hnh svtinh.

II.

Cu trc hthng truyn hnh svtinh, cc kthut c sdng trong

THVT:

Cc trm pht sng truyn hnhDirect Broadcast Satellte (DBS)Cc trm DBS lm nhim vnhn tn hiu Video/Audio tcc ngun chng trnh

khc nhau nh: Stadio, internet, vtinh cp quang, cp tn hiu sau c s

ha, m ha, nn ghp knh, iu chqua hthng m ha qun l khch hng

ri c pht ln vtinh vi tn sng uplink.

Vtinh: Nhn tn hiu ttrm pht khuch i ri chuyn n cho cc thu

bao vi tn sng downlink.

Ti nh cc thu bao gm Anten cho thu tn hiu vtinh v thit bgii

m tn hiu vtinh (set-top box) Anten v bgii m c ni vi nhau bi cpng trc RG-6


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S khi hthng:

1. Trm pht mt t:

Tn hiu A/V tstudio c chuyn i sang tn hiu s, m ha v nn MPEG-2,thng dng chun MP@ML. y l tiu chun thng nht trong vic truyn dn pht

sng tn hiu video squa vtinh c phn gii tiu chun (SDTV). i vi tiu chun

ting MPEG c cc dng thc mn, stereo, Join stereo, dual mono. Mi chng trnh

A/V sau nn c vn tc trung bnh khong 4Mbps. Sau cc tn hiu A/V qua cc b

Scrambler (xo trn mt m tn hiu) ca hthng truy nhp c iu kin CA

(Conditional Access) theo cc yu cu vqun l thu bao v chng trnh cung cp cho

thu bao. Tn hiu sau kha m c ghp knh tp thnh dng truyn ti a

chng trnh (10-20 chng trnh)

Tn hiu sau ghp knh c qua cc bm ha knh truyn Reed Solomon(RS)

Bsa sai FEC, tng ng vi tc khong 52 Mbps (nu ghp 10 chng trnh) sau

n khi iu chsdng kthut iu chQPSK tn strung tn 70MHz to

sng trung tn c di thng khong 33.8 MHz. Tip theo n bdich tn ln di C hoc


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Ku, khuch i cng sut a ln hthng anten pht ln vtinh. Anten pht thng c

ng knh rt rng t9-12m. ng knh cng rng th chnh xc n vtinh cng

cao. V tng cng sut nhn ti vtinh. Anten pht chhng n vtinh xc nh v

pht trong khong tn sxc nh.

S khi hthng:

2. Vtinh (satellite)

Vtinh c cha cc trm p pht chuyn tip tn hiu (transponder): nhn tn hiu

pht r ttrm mt t sau d dch dn khuch i ri pht trli tri t. Do vtinh

cao rt ln so vi tri t (khong 36000km trn quo a tnh) nn tm bao ph

ca n l rt ln (ti a ln ti 1/3 tri t). Tuy nhin trong truyn hnh vtinh mt v

tinh thng thng c din phsng trong 1 phn chu lc hay 1 phn quc gia no

v c ththay i c vng bao ph(beam sng).

3. Trm thu tn hiu vtinh (Downlink station)

C nhiu dng trm thu khc nhau ty theo mc ch sdng:


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Trm thu dng cho truyn hnh cp

Trm pht li truyn hnh mt t

DTH (Direct to home) kt ni trc tip ti hgia nh

MATV dng cho cc khch sn hay ton chung c

Cc trm thu ny c thng skthut ging nhau. Chkhc nhau vcht lng (ng

knh anten, loi u thu chuyn dng hay dn dng) v slng thit bthu. (sknh

cn thu ca cc trm pht li) ty thuc mc ch ca tng loi trm thu. Mt trm thu

bao gm cc thnh phn:

Thit bbn ngoi (Outdoor)

Anten parabol (cho): l anten dng thu tn hiu cc chng trnh truyn

hnh vtinh, kch thc t0,6m-6m ty loi LNB (Low Noise Block): l bkhuch i tp nhiu thp gn trn anten

parabol nhm tng cng sut tn hiu thu c tanten.

C cu iu khin cho (Positioner) quay theo gc ngng v phng v.

C cu iu khin gc quay phn cc (Polarotor)

Thit bbn trong (Indoor)

Mch in iu khin gc quay ca Polarotor va Positioner

Bgii m a phng tin- IRD (Integrate Recever Decoder) hay cn gi l

Set-top Box (STB) ngoi chc nng l thit bthu v gii m tn hiu truyn

hnh chuyn sang tn hiu AV hay RF m tivi thng thng c thxem c.

N cn c chc nng nhn din ng thu bao, gii m cc chng trnh thu

bao hay dch vthu bao ng k. iu ny thng thc hin thng qua

Smart card (ththng minh). Thit bny trng nh mt thtn dng hay in

thoi. N c dng nh mt vt chng vquyn gii m cc tn hiu m

thu bao ng k{.

Cc dch vtruyn pht tn hiu:


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4. Kthut sdng trong THVT:

Knguyn truyn dn thng tin bng vtinh thc sc hiu quvo

nhng nm 80. Khi , truyn dn qua vtinh tit kim bng thng v gi

thnh khi sdng cc kiu iu chQPSK v BPSK. Nhng nm 90, cng nghpht qung b qua vtinh pht trin rng ri sau khi ETSI cng bchun

DVB-S u tin, kt hp iu chQPSK vi m sa li hng truyn trong v

ngoi (Viterbi v Reed-Solomon).

Cuc cch mng vm sa li kt hp vi cc cu hnh iu chmi v mt

lot cc c tnh mi l nn tng lm nn tiu chun DVB-S2. y l tiu

chun mi nht trong cc tiu chun ca ETSI vtruyn dn thng tin vtinh.

Kiu iu chny cng khp li con ng tim cn gii hn vmt l

thuyt (gii hn shannon).DVB-S2 vi hiu sut sdng bng thng tng t30% n 131% so vi DVB-S

ang c kzvng sem li hiu quto ln khi c ng dng, vi kh

nng truyn dn ng thi nhiu dch vc tc ln nh truyn hnh c

phn gii cao HDTV, Internet tc cao, truyn sliu v cc ng dng


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chuyn nghip trn cng mt bpht p ca vtinh m hthng DVB-S

trc kh c ththc hin c.

a) Chun DVB-S

Ra i nm 1994 c sdng phbin truyn tn hiu truyn hnh qungb vtinh. ng truyn vtinh ngoi nhng u im cn tn ti mt s

nhc im l cly thng tin ln, cn chu nhiu nh hng ca nhiu v tp

m bn thn dng truyn ti MPEG-2 khng c chc nng sa li, chng

nhiu ng truyn do vy khng thtruyn trc tip dng truyn ti..

Tiu chun DVB-S c thit ktrn c sgia tng khnng chng nhiu

cho dng truyn ti MPEG-2. Theo DVB-S qu trnh xl tn hiu vtinh gm

cc bc sau:

-

Thch nghi u vo v phn tch nng lng.- M ha ngoi sdng Reed- Solomon RS (204, 188)

- Xo trn bit lm tng khnng chng li cm.

- M ha trong sdng m xon vi cc tlm khc nhau.

- Lc bng gc v iu chQPSK.

S hthng:


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Cc thng sc bn hthng truyn hnh svtinh DVB-S:

Stt Thng s Yu cu

1 Hthng truyn hnh svtinh DVB-S

2 Di tn s 11/12Ghz

3 Hs 0.35

5 Phng thc iu chs QPSK

6 Tlm sa sai (FEC) 1/2, 2/3, 3/4, 5/6, 7/8

b) Chun DVB-S2

S khi


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y l tiu chun truyn hnh svtinh th2 c ETSI ph duyt 3/2005.

y l tiu chun mi nht trong hthng tiu chun DVB cho cc ng dng v

tinh bng rng. Cuc cch mng vm sa li kt hp vi cu hnh iu chmi

v mt lot cc c tnh mi l nn tng to nn tiu chun DVB-S2.

Cc thng sc bn ca hthng truyn hnh svtinh DVB-S2:


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Stt Thng s Yu cu

1 Hthng truyn hnh sv

tinh

DVB-S2

2 Di tn s 11/12Ghz

3 Kiu m ha v iu ch CCM

4 Hs 0.35, 0.25, 0.20

5 Phng thc iu chs QPSK 8PSK 16APSK 32APSK

6 Tlm sa sai (FEC) 1/2, 3/5,

2/3, 3/4,

4/5, 5/6,

8/9,

9/10

3/5, 2/3,

3/4, 5/6,

8/9, 9/10

2/3, 3/4,

4/5, 5/6,

8/9, 9/10

3/4, 4/5,

5/6, 8/9,

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7 Khung FEC 64 800 (bits)

III. Truyn hnh svtinh Vit Nam.

Ti Vit Nam, truyn hnh squa vtinh chnh thc c i truyn hnh

Vit Nam ng dng tnm 1998 truyn dn cc chng trnh truyn hnh n

cc trm pht li trn phm vi ton quc v n 2002 bt u trin khai pht sng

truyn hnh svtinh dng thc DTH trn bng tn Ku va cung cp dch vtruyn

hnh trc tip va lm chc nng truyn dn.

Theo thng k, nm 2005 slng thu bao truyn hnh trtin ca Vit

Nam khong 2,1 triu, nhng n nm 2010, con sny ln n trn 4,2 triu

thu bao. Tkhi vtinh VINASAT-1 c phng ln quo thng 4/2008, truyn

hnh svtinh c nhng bc pht trin vt bc cvslng cc nh cung

cp dch v, slng thu bao v cslng knh pht thanh, truyn hnh. Thng

1/2010, Tng Cng ty VTC ra mt dch vDTH vi gi knh HDTV u tin pht

sng qua vtinh VINASAT-1.

Ngy 16/2/2009 Thtng Chnh phban hnh Quyt nh 22/2009/Q-TTg

ph duyt Quy hoch truyn dn pht sng pht thanh truyn hnh n nm 2020


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vi nh hng thc hin thnh cng ltrnh chuyn i cng nghtkthut

tng tsang kthut svo thi im cui nm 2020.

n thi im hin nay, truyn hnh svtinh tiu chun DVB-S/S2 c

ng dng phbin ti Vit Nam, hu ht cc i PTTH ln, cc doanh nghip cung

cp dch vtruyn dn pht sng u v ang ng dng cung cp dch vv

tiu chun DVB-S/S2 c a vo nh hng pht trin cng nghnu trong

Quy hoch truyn dn pht sng pht thanh, truyn hnh n nm 2020. C th

im qua mt sn vang ng dng rng ri tiu chun DVB-S/S2 nh sau:

Tng Cng ty truyn thng a phng tin pht sng DVB-S2 trn vtinh

VINASAT-1 v ASIASAT-5 cung cp cc gi dch vni dung SDTV v HDTV tthng

1/2010;

Lin doanh VSTV vi i THVN phtsng DVB-S trn vtinh VINASAT-1

cung cp cc dch vni dung SD v ang trin khai tip hthng pht sng DVB-

S2 ra mt gi ni dung HDTV;

Cng ty cphn Nghe nhn Ton cu c giy php v cung cp dch

vni dung SDTV v HDTV trn vtinh NSS-6 ng dng tiu chun DVB-S2 trong

thi gian sp ti.

Ngoi ra, mt si PTTH nh i TH thnh phHCM, i Ting ni Nhn

Dn TP HCM, i PTTH Hi Phng... c giai on thnghim thnh cng pht

sng truyn hnh squa vtinh v strin khai pht sngn nh chnh thc trong

tng lai gn, ph hp nh hng Quy hoch.

Nhn chung, bc u trin khai Quy hoch, cng tc qun l{ Nh nc v

truyn dn pht sng pht thanh, truyn hnh c nhng tin bng kkhi Quy

hoch truyn dn pht sng pht thanh, truyn hnh c Thtng Chnh ph

ban hnh vi nhng nh hng r rng vtiu chun cng ngh. Trc y, vi

truyn hnh tng tmt t, hthng cc tiu chun kthut c xy dng

kh y tphn pht, truyn dn n phn thu, iu ny gip truyn hnh

tng tti Vit Nam pht trin nhanh chng trong giai on trc nm 2000 v

truyn hnh tng t phsng xp x97% dn c trn cnc.


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Truyen Hinh Ve Tinh