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Tiu lun
MNG TRUYN HNH CP
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LI NI U
Nn kinh t nc ta hin nay ang trong thi k pht trin, i i vi n l s
bng n v thng tin v truyn thng, trong c bit l ngnh Mng Vin Thng
v ang ngy cng khng nh vai tr ca mnh l mt phng tin thng tin i
chng c sc thuyt phc cao mang thng tin v hnh nh v m thanh n vi con
ngi. Thng qua cc chng trnh pht sng hng ngy, truyn hnh mang thng tin
v ng li chnh sch ca ng v Nh nc, tnh hnh kinh t, chnh tr, x hi,
gip ngi dn th hin c ting ni v thng tin ca mnh. L sn chi gii tr rt
b ch ca mi ngi. Bn cnh Mng Vin Thng cn gp phn vo vic m
rng quan h i ngoi ca t nc, giao lu vi cc nc trong khu vc v trn
th gii.
Nhng nm gn y, do nhu cu thng thc cc chng trnh truyn hnh cht
lng cao, ni dung phong ph ca con ngi ngy cng tng, cng vi s tin b
vt bc trong khoa hc cng ngh, cc mng truyn hnh cp c bit l truyn hnh
cp hu tuyn c nhng bc pht trin mnh m. Gi y truyn hnh cp khng
ch cung cp chng trnh truyn hnh cht lng cao m cn cung cp cc dch v
truyn s liu, truy nhp Internet tc cao v cc dch v tng tc.
Cng vi s i ln ca cng ngh truyn hnh th gii, truyn hnh Vit Nam
cng c nhng bc pht trin. Mt s dch v truyn hnh mi xut hin nh
truyn hnh cp v tuyn MMDS v truyn hnh qua v tinh phn no tho mn
nhu cu xem truyn hnh nhiu knh ca ngi dn. Cc chng trnh do MMDS
cung cp kh phong ph v hp dn, tuy nhin MMDS cng gp mt s hn ch ln
v vn ph sng, cht lng tn hiu v kh nng cung cp dch v. Truyn hnh
qua v tinh cng gp mt s vn nh: ng k dch v phc tp, chi ph thu bao
cao. V nhng l do ny m s ngi xem truyn hnh qua v tinh Vit Nam rt t.
V vy, c th p ng mt cch tt nht nhu cu xem truyn ca ngi dn,
ch c th l xy dng mt mng truyn hnh cp hu tuyn dn thng si cp tn
hiu t trung tm chng trnh n cc h dn. Nh , ngi dn c th xem cc
chng trnh c cht lng cao m khng cn phi nng cao cc ct anten thu tn
hiu, s khng cn hnh nh cc dn anten ln xn, cao thp trn cc nc nh, m
quan th s c ci thin.
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PHN I: L THUYT
CHNG I: TM HIU TNG QUAN V MNG TRUYN HNH
CP
1.1
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+ Nm 2004, H thng mang cap CATV ngay cang c m rng, vic s dung
h thng cap quang ngay cang phat huy tac dung tt, tao tin cho vic m rng
mi quan h hp tac va trin khai h thng truyn hinh tra tin vi pham vi ln.
Ngay 01/11/2004, trin khai truyn hinh s v tinh DTH hoan tt v chinh thc phat
song trn pham vi toan quc.
+ Nm 2005, VCTV thanh lp 4 chi nhanh trn ia ban Thnh Ph Ha Ni,
ngoai ra VCTV con hp tac vi 3 n vi khac trin khai nhanh chng mang cap
CATV khu vc Ha Ni. DTH tng trng manh me ca v doanh s ban thit bi va
thu bao, thanh lp c h thng phn phi trn ton quc tai 64 tinh thanh.
+ Nm 2006, VCTV tip tuc phat trin CATV tai cac tinh, thanh ph nh: Thai
Binh, Ninh Binh, Vung tau, Tin Giang, Phu tho. Ln u tin, VCTV ban ban quyn
cho i tac My va Canada 02 knh VCTV2 va VCTV4. Ngay 15/09/2006, VCTV
chinh thc c ai THVN giao quyn t chu tai chinh nhn s, tao iu kin tt
nht VCTV phat trin. Cung thi gian nay, ai THVN quyt inh giao nhim vu
kinh doanh quang cao trn truyn hinh tra tin cho VCTV.
+ Nm 2007 vi c ch qua ly va tai chinh thng thoang, quyn t chu cao, y
la nm bt pha cua VCTV. VCTV theo ui cac chin lc nng cao cht lng dich
vu va chinh sach u ai hp ly nht cho khach hang. Ngay 06/03/2007, Info TV
knh thng tin tai chinh kinh t knh truyn hinh chng khoan trc tip u tin tai
VN, do VCTV ky kt trin khai cung i tac Ocean Media chinh thc phat song.
VCTV nghin cu va chun bi cac an a ra cac goi san phm cng ngh cao
nh: IP TV, Mobile TV u t manh m cho DTH, xuc tin lin doanh vi i tac
nc ngoai nhm phat trin DTH ca v ni dung va ky thut.
+ Nm 2008 n u s kin Vinasat 1, VCTV d kin tip tc u t cho
DTH, xc tip lin doanh vi i tc nc ngoi nhm pht trin DTH c v ni
dung v k thut. Mng CATV tip tc c m rng thm cc chi nhnh ti H Ni
v mt tnh, thnh ph khc trn ton quc.
+ Nm 2010 Tuyn hnh cp thc hin mt cuc cch mng ngn ngi khi pht
sng Animax, knh chiu hot hnh anime 24/7 duy nht ti Chu . Tuy nhin v
sau knh ny b ct.
+ Nm 2011, 3 knh truyn hnh c sc : SCTV14, SCTV9, Truyn hnh an
ninh c gp mt trong h thng ca Truyn Hnh Cp Vit Nam
Thng 11/2011, Truyn hnh Cp Vit Nam chnh thc trin khai cung cp
dch v Truyn Hnh nt tiu chun mng Cp VCTV ti a bn H Ni.
+ Thng 2/2012, trn c s t chc, sp xp li Trung Tm K Thut Truyn
Hnh Cp Vit Nam, Tng Gim c i THVN c quyt nh s 189//Q-
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THVN thnh lp cng ty TNHH mt thnh vin Truyn Hnh Cp Vit Nam
(VIETNAM CABLE TELEVISION CORPORATION).
Nm 2012, vi s xut hin ca knh VCTV 14-Lotte t Vit Home Shopping.
Knh mua sm trc tuyn ln nht ti Vit Nam nng tng s knh ln 64 knh
trn mng cp cng vi gn 100 knh truyn hnh trn h thng truyn hnh nt
tiu chun SD v nt cao HD.
Thng 5/2012, Truyn Hnh Cp Vit Nam m rng a bn cung cp dch v HD
VCTV ti a bn Thi Nguyn v Ph Th sau khi trin khai ti a bn H Ni.
Ngy 26/06/2012, nhn giy ng k kinh doanh.
Ngy 10/07/2012, Cng ty TNHH MTV Truyn Hnh Cp Vit Nam chnh thc lm
l ra mt ti khch sn Deawoo H Ni.
Thng 11/2012 Truyn Hnh Cp Vit Nam ng lot trin khai dch v HD trn
nhiu tnh thnh trong c nc (Qung Ninh, Hi Phng, Thi Bnh, Ngh An, H
Tnh, Qung Tr, Bnh Thun, An Giang, Tin Giang... ) v d kin s tip tc m
rng phm vi phc v thm nhiu tnh thnh trong c nc trong thi gian ti.
Vi nhng thnh tch t c, Truyn Hnh Cp Vit Nam nhn c nhiu
bng khen, c lun lu ca Th Tng Chnh Ph, ca Tng Gim c i THVN.
1.2 Khi nim v truyn hnh cp
Truyn hnh cp ra i nhm khc phc nhng hn ch ca truyn hnh sng, p
ng tt hn na nhng nhu cu, dch v ring l mi m m truyn hnh sng khng
lm ni. Truyn hnh cp thc hin theo nguyn tc tn hiu c truyn hnh trc
tip qua cp ni t u pht n u my thu hnh. Do c im m Truyn hnh cp
c th chuyn i nhiu chng trnh mt lc c th p ng nhu cu c th ca tng
ngi s dng. Ngoi ra, truyn hnh cp cn c th gii quyt mt lot dch v ca
x hi hin i m truyn hnh sng khng th thc hin.
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Cp nhnh
Hp thit b
thu bao
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+ Cu trc trc chnh bao gm : cp ng trc chnh, khuch i trc, b chia tin
hiu trc
+ Cp trc nhnh bao gm: Cp ng trc nhnh, b khuch i nhnh, b chia trc
nhnh
+ Cp mng thu bao: cp ng trc thu bao. TV
+ C th phc v t 1500 2000 thu bao/node quang
- u im ca HFC
+ Cht lng tn hiu tt do khng s dng cc b khuch i
+ Do khng s dng cc b khuch i cao tn nn vic thi cng lp t, vn hnh
d dng hn.
+ Cc thit b t ng c kh nng truyn hai chiu nn n nh mng vn cao khi
trin khai mng hai chiu.
+ S lng thu bao/node quang nh nn c kh nng cung cp tt dch v hai chiu
vi tc cao.
+ Gim chi ph cp ngun cng t in, bo dng, thay th cc thit b tch cc.
- Nhc im ca HFC:
+ Kh nng bao ph ca mt node quang nh do khng s dng khuch i.
+ Yu cu node quang s dng phi c cng sut ln, cht lng cao, n nh.
+ Ph hp vi khu vc c quy hoch tp trung, khng ph hp vi a hnh Vit
Nam.
+ Yu cu v chi ph cao.
1.9.2 Thit b truyn dn trong HFC
1. B khuch i hai chiu.
Trong phn mng cp ng trc, cc b khuch i hai chiu c s dng bao gm
hai loi.
- B khuch i phn phi ( khuch i tn hiu RF v t vo 2 hoc 4 u cp ra
khc nhau)
- B khuch i ng dy m rng Line Extender Amplifier mt h thng HFC
hin i thng c t 4 n 6 b khuch i cho tng khuch i RF sau mi node.
a s cc b khuch t iu chnh b p nhng thay i khc nhau theo nhit
suy hao v p ng tn s
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Hnh 1.13 Kin trc mng truyn hnh cp truyn dn bng cp quang v cp
ng trc
3. Cp quang.
Mi cp quang c cha t 12 n 14 si quang ty theo kch c mi loi cp.
Loi si cp c s dng y thng l si n mode-SM c suy hao khong 0,4
dB/km bc sng hot ng l=1310 nm hoc suy hao 0,25 dB/km l=1550 nm
(mc suy hao ny n nh trong di nhit thng v c lp vi di tn s v
tuyn).
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Hnh:
1.19 Modem cp
Hnh: 1.19 Modem cp
9. H thng kt ni modem cp CMTS
H thng ny nm trong Headend, thuc v bn kia ca mng so vi modem
cp. L thit b kt ni cho ng t pha thu bao n ch l cc Headend ca cc
cng ty cp, do CMTS cng c coi l giao din gia cc modem cp v mng
Internet IP.
+ CMTS c nhiu chc nng ging nh mt DSLAM trong h thng DSL.
+ CMTS n lng ng ln t mt nhm thu bao trn mt knh n v nh
tuyn n n ISP kt ni vo mng Internet.
+ Mi CMTS cha mt hoc nhiu card ng dy modem ( CMLC ). Cc CMLC
chuyn cc dng s liu IP thnh cc tn hiu RF ng xung ( n nh thu bao )
sau a qua b nng tn a cc knh tn hiu vo mt knh tn hiu vo
mt knh xc nh v ghp chng vi cc tn hiu truyn hnh v trnh t ngc li
vi ng ln. Mt s server trong mng modem cp my ch DHCP (Dynamic
Hort Protocol) c xc nh bi RF2181. Server ny cung cp cc a ch Ip theo
nhu cu cho modem cp v cc thit b PC theo sau n. My ch ToD ( Time of Day)
c xc nh bi RFC 868, c nhim v l gn cc tem thi gian cho cc s kin
SV: Nguyn xun V
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2- T sa cha.
Kim tra cc thit b khi hng hc, tm v pht hin nhng li xy ra trong cc
thit b ngng hot ng, sa cha cc thit b...
3.2 H thng sa cha ca phng K Thut.
3.2.1 S Tivi mu.
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B knh v trung tn: B knh l thu tn hiu song mang t i pht thng qua
Anten, sau i tn v tn hiu chung IF dng khuch i. Trung tn l khuch
i tn hiu IF ln bin ln sau tch sng ly ra tn hiu Video tng hp.
Cuyn mach AV: L tip nhn thm tn hiu Video t bn ngoi nh tn hiu ca
u VCD.
Mch x l tn hiu chi: L khuch i tn hiu Y, thay i bin v in p
thm (thnh phn mt chiu) ca tn hiu Y
sng ca nh, khi mch chi khng hot ng s sinh hin tng mt hnh, mt
nhiu.
Mch gii m mu: L gii m tn hiu song mang C ( Choma ) ly ra 3 tn
hiu mu thiu chi R-Y, B-Y, G-Y, cung cp cho mch ma trn khi phc li ba
tn hiu mu a vo n hnh, nu hng khi gii m th ch c tn hiu Y (en
trng) i vo n hnh.
Mch ma trn v K cng xut sc: thng thng mch ma trn kim lun K
cng xut sc, ma trn l mch trn tn hiu chi Y vo cc tn hiu mu R-Y, B-Y,
G-Y l cc tn hiu mu thiu chi to tn hiu mu y l R, G, B. Mch K
cng xut sc , khuch i ba tn hiu R, G, B ln bin ln cung cp cho n
hnh, trong qu trnh khuch i tn hiu sc, mch K cng xut sc kim lun vic
xa tia qut ngc.
Khi ng ting: L tch tn hiu FM ra khi tn hiu Video tng hp, sau
khuch i trung tn ting v tch song iu tn ly ra tn hiu m tn, tip tc
khuch i tn hiu m tn qua mch cng xut ri a ra loa.
Mch vi x l: L to ra cc in p iu khin ton b cc hot ng ca my
nh: iu khin tt m ngun t xa, iu khin thay i sang, tng phn,
mu sc ca nh, iu khin thay i qu trnh d knh v nh knh
n hnh mu: l linh kin chim ti 50% gi thnh ca Tivi, n hnh mu c
nhim v ti to li hnh nh ban u.
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3.2.2 My vi tnh
1.S my vi tnh
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Card Video: L thit b hin th thng tin ca my tnh gip ngi s dng giao
tip vi my. rng c tnh bng Inch. Mn hnh ng phng in t CRT (li,
phng) mn hnh tinh th lng LCD, mn hnh Plasma.
a cng: hay cn gi l cng (Hard Disk Drive, HDD) l thit b dng
lu tr d liu trn b mt cc tm a hnh trn ph vt liu t tnh.
L loi b nh khng thay i (non-volatile), c ngha l chng khng b mt d
liu khi ngng cung cp ngun in cho chng.
L thit b rt quan trng trong h thng bi chng cha d liu thnh qu ca mt
qu trnh lm vic ca nhng ngi s dng my tnh. Nhng s h hng ca cc
thit b khc trong h thng my tnh c th sa cha hoc thay th c, nhng d
liu b mt do yu t h hng phn cng thng rt kh ly li c.
Card Net: hay l NIC Card (Adapter Card) l thit b ni kt gia my tnh v
cp mng. Chng thng c giao tip vi my tnh qua cc khe cm nh: ISA,
PCI hay USB Phn giao tip vi mng thng thng theo cc tiu chun nh:
AUI, BNC, UTP,
- Chun b d liu a ln mng: trc khi a ln mng, d liu phi c chuyn
t dng byte, bit sang tn hiu in c th truyn trn cp.
- Gi d liu n my tnh khc.
- Kim sot lung d liu gia my tnh v h thng cp.
Card Sound: (bo mch m thanh) trong my tnh l mt bo mch m rng cc
chc nng v m thanh (v mt s chc nng khc v gii tr, kt ni...) trn my
tnh, thng qua cc phn mm n cho php ghi li m thanh (u vo) hoc trch xut
m thanh (u ra) thng qua cc thit b chuyn dng khc. Mi hot ng ca bo
mch m thanh phi c iu khin bng phn mm hoc
trnh iu khin
(driver) trn my tnh. Cc hot ng ca bo mch m thanh c th l:
- Trch xut cc tn hiu m thanh dng tn hiu tng t (analog) hoc tn hiu s
(digital) ti cc loa pht ra m thanh m con ngi nghe c.
- Ghi li v m thanh lu tr (hoc phc v x l) m thanh trong: ting ni, m
thanh t nhin, m nhc, phim...thng qua cc ng u vo.
- X l v pht li m thanh t cc thit b khc: Pht m thanh trc tip t cc a
quang, thit b pht MIDI.
- Kt ni vi cc b iu khin game (joytick).
- L thit b kt ni trung gian: (Cng IEEE-1394).
Keyboard: (bn phm) l thit b nhp. Ngoi nhng chc nng c bn, bn c
th tm thy nhng loi bn phm c nhiu chc nng m rng nghe nhc, truy
cp Internet, hoc chi game. Bn phm cm cng PS/2, bn phm cm cng USB,
bn phm khng dy.
SV: Nguyn xun V
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LI KT
Truyn hnh cp l mt c th ring bit do n chim mt v tr rt quan
trng trong i sng ca ngi dn Vit nam ni ring v tt c mi ngi dn trn
ton th gii ni chung. V th hin nay Truyn hnh c coi nh l mt tri tim, l
mt lnh vc truyn thng c th p ng tt c mi nhu cu xem truyn hnh ca
mi ngi vi danh hiu mang c th gii n ngi nh ca bn.
Tm li truyn hnh cp l mt knh thng tin khng th thiu trong i sng
ca mi ngi.
Mt ln na em xin chn thnh cm Thy gio Nguyn C Vn Thanh v cc
thy c trong khoa k thut ca trng C PT-THI, cn b Cng Ty C Phn in
T Tin Hc HEREVN v c bit l anh Trnh Ngc Thoi ph phng k thut
truyn dn pht sng gip , ch bo tn tnh cho em v gip em hon thnh tt
bi bo co ny!
Em xin chn thnh cm n!
H Nam, thng 04 nm 2013
Sinh vin
Nguyn Xun V
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MC MC
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