2 Page 1
..................................................................................................................... 1
.............................................................................. 3
PH L NH .................................................................................................. 4
THUT NG VIT TT ............................................................................................. 6
............................................................................................................... 9
1 NG HFC( Hybrid Fiber Coaxial) ........................................................ 11
1.1. Tng quan v m ng HFC ........................................................................................ 11
1 2 ..................................................................................... 19
1 2 1 .................................................................................. 19
1 2 2 .................................................................... 21
1.2.2.1. B khu i hai chiu .................................................................................... 21
1 2 2 2 p q p ng trc trong m ng ............................................................ 22
1.2.2.3.Cu r (Tap) ....................................................................................................... 23
1.2.2.4.Node quang ........................................................................................................ 24
1.2.2.5. Thi t b k t cui truy STB (Set-Top-Box) ........................................... 24
1 2 2 6 p ( ) ....................................................................... 25
1.2.2.7. H thng k t n p CMTS .............................................................. 26
1.2.2.8. H thng IP Phone ............................................................................................ 27
1.2.2.9. H thng thi t b c d ch v ................................................. 27
1.3. IEEE 802.14 ........................................................................................................... 27
1 .............................................................................................. 28
1 s ......................................................................................................... 29
1 6 .............................................................................. 30
2 Page 2
1 7 ng HFC ............................................................................... 31
1 7 1 ............................................................................................................. 31
1 7 2 t trong m ng HFC ...................................................................... 32
2 E ODE .................................................................................... 36
2 1 m v Cable Modem ................................................................... 36
2.2. L ch s i c Cable Modem ........................................ 36
2.3. C a Cable Modem ..................................................................................... 37
2 3 1 c a Cable Modem ......................................................................... 37
2.3.1.1. Tuner ................................................................................................................ 38
2.3.1.2. Demodulator ..................................................................................................... 39
2.3.1.3. Media Access Control (MAC) ........................................................................... 40
2.3.1.4. Microcessor....................................................................................................... 41
2 k p p cable modem ............................................................... 41
2.5. Ph cable modem .................................................................................................... 42
2 6 x c a cable modem ........................................................................................ 43
2 7 p ............................................................. 44
2 7 1 p CM ................................................................................................ 45
2.7.2. H thng k t cu p CMTS ................................................................ 45
2.7.3. Mt s server trong m p .................................................................. 46
2 s ( )................................ 46
U THAM KH O.............................................................................................. 48
2 Page 3
H tn thnh vin
Ni dung cng vic
Ph Q ( ng)
- u - q
Nguy
- u - Truyn d ng HFC
Nguyn Q
- u - m cu t o - m
- u - Cable Modem
Nguy ng
- u - ng HFC
- u - IEEE 802.14
Tr nh
- u - s
2 Page 4
PH L NH
1 1 n m ng HFC ........................................................................... 11
1 2 h thng headend ................................................................................. 12
1 3 k ............................................................................. 13
1 .................................................................................... 14
1 p ...................................................................... 15
1 6 p ........................................................................ 17
1 7 truyn d ng HFC ................................................................... 19
1 ............................................................. 19
1 khu i 2 chiu .................................................................................... 21
1 1 ng truyn p n d n b p q p
ng trc........................................................................................................................ 22
1 11 p q ....................................................................................... 22
1 12 p ng trc .................................................................................. 23
1 13 u truy p f 1 ....................................... 23
1 1 u r ( p) s ......................................................... 24
1 1 quang .................................................................................................. 24
1 16 Top Box trong truy p ......................................................... 25
1 17 p .................................................................................................. 26
1 1 k O ........................................................ 29
2 1 .................................................................................. 36
2 2 c ......................................................................... 37
2 3 E -CABLE MODEM .............................................................. 38
2 u ch QAM ................................................................................. 40
2 Page 5
2 khi b chuy i D/A ....................................................................... 40
2 6 k p p c a Cable Modem ............................................... 42
2 7 RF c a Cable Modem .............................................................................. 43
2 x ph Headend/station........................................................................... 43
2 p n c a h thng Cable Modem ................................................... 44
2 1 thng chu ................................................. 46
2 Page 6
THUT NG VIT TT
T vit tt gha ting anh gha ting vit
CM Cable Modem p
TV Television Truy
RF Radio Frequency Tn s n
MAC Medium Access Control u khi n truy nhp
ng
QAM Quadrature Amplitude
Modulation u ch c p
CATV Communitty Attenna
Television
Truy q ng
ng
HFC Hybrid Fiber Coaxial M p q p ng
trc
CMTS Cable Modem Terminater
System H thng k t cu p
FN Fiber Node q
LAN Local Area Network M c b
WAN Wide Area Network M ng di n rng
SONET Synchronous Optical
Network Chu n truyn d ng b
DHCP Dynamic Host Configuration
Protocol Giao thc c ng
2 Page 7
FDM Frequency Division
Multiplexing p p n s
VOD Video On Demand Truy u
HDTV High Density Television Truy p i cao
HFC Hybrid Fiber Coaxial
M p q p ng
trc
HFPC Hybrid Fiber Passive Coaxial M p q p ng
trc th ng
SDH Synchronous Digital
Hierarchy p s ng b
STB Set Top Box Thi t b k t cui truy
IF Intermediate Frequency Trung tn
HDTV High Density Television Truy p i cao
IP Internet Protocol
ISP Internet Service Provider p
IEEE Institute of Electrical and
Electronic Engineers
Vi u k thu n
n t
HE Headend x
ATM Asynchronous Transfer Mode Ch truyn kh ng b
DLC Digitar Loop Carrier p s
QPSK Quadrature Phase Shift iu ch pha c p
2 Page 8
MUX Multiplex p ( )
PC Personal Computer
CPU Central Processing Unit x
NTSC National Television System
Committee
PCI Peripheral Component
Interconnect
( )
QoS Quality of Service cht
ng d ch v
PHY Physical
DSL Digital Subscriber Line K s
DSLAM Digital Subscriber Line
Access Multiplexer
Thi t b cung cp d ch v
D p ng
IEEE Institute of Electrical and
Electronic Engineers
Vi u k thu n
n t
2 Page 9
ng cable TV truyn thng s d p ng trc, t n
m c a mt m p ng tr n nhi k i
ng truyn: c kho ng 1km l i cn m k n u m
bao x k 3 k n kho 3 k ng
truyn.
Vi c cn s dng nhi k i d sau:
+ V li m ng: n u m k i g s c
tt c u b ng.
+ Ch ng truyn b ng: sau mi l c khuy i,
u b nhi v xa, ch ng
truyn s b ng.
M ng HFC khc ph p q
n mt lo p p i quang. T p p u quang s
c chuy p ng trc s c s d k t n
m c
+ s ng d ch v.
+ H n ch s c g
+ Chia mt m ng trc l ng trc nh, mi m ng
xu p m m phn ph q ng nh
c lp v c s c thng.
V truy p u tuy s dng hi i Vi
HFC (Hybrid Fiber Coaxial Cable) - p p q
p ng trc.
M ng truy p n th s d t b
p ng tr khuy
hi k p c v p k p c nhu c i xem c v
ch ch v.
2 Page 10
ng truy p s d HFC, vi phn truyn
d n s d p q m c s d
tn c p q suy hao thp khc phc nh m c a
m ng CATV truyn thng. M ng HFC- k p mt lo ch
v OD c bi Internet.
Kh a Truy p p u tuy
thng truy u truy c truyn d n b p n tng h
truyn s li ng truy p ( )
ngh Cable Modem.
x
2
h ng ng id i a ia : s k
k p
s s EEE
2 1
h ng 2 a d m q
Cable Modem, l ch s i c
s s m v, ch a nh p n c
p s p n nh ng chu n hi c
s d DO D EEE 2 1
ng r s cung cp c m
v HFC & Cable Modem. M gng rt nhiu song do th
n, ni dung c k k i nh ng thi s
t mong nh c nh k p ti p tc
chnh s a.
.
H N
hm 5 5- T T2
Kh a T T
T ng i hc in Lc
2 Page 11
NG HFC( Hybrid Fiber Coaxial)
1.1. Tng quan v m ng HFC
HFC (Hybrid Fiber Coaxial) mt m ng gi a p quang p ng
trc t o ra mt m ng rng. s d ng th p q p ng trc
truyn p p u. Vi c truy u t q
p q q p ng trc.
HFC c s p 1 ki
s
nh Kin t c c bn m ng HFC
M ng p quang m rng t headend ch (master headend) n headend
(regional headend), hubsite c a m ng cn sau chuy n i
q n (fiber optic node) phc v t 500 2 bao m i
Master headend ng antenparabol v tinh thu hi u video trong
k gian lung IP. Mt s masterheadend bao gm thi t b
n tho i cung cp d ch v vin n cng ng. Mt regional headend
thu hi u video t master headend k c a ph , k
dc, k cng khi c p p hoc qu ng
h thng h
2 Page 12
nh 1.2: S h thng headend
Headend thu nhn hi u t nhiu ngun k nhau ( hi u qu ng
v tinh, hi u s n xut ). Sau khi qua c x u ch ,
p k , trn... hi u c ra m ng truyn d n p phi n
bao.
Fiber optic node mt b thu p quang rng kh chuy n i
hi u u ch quang chiu xung n t headend ra hi u n gi n
bao, chuy i hi u n n t bao ra hi u quang
cho chiu c l i. hi u n chiu xung gi n bao hi u u ch
RF nm trong d i tn t 50 MHz 1 MHz. p q p n
headend hoc hub theo point-to-point hoc star topology hoc ring topology. Fiber
p s p s g n
headend. M u theo chi c l u ch RF nm trong d i tn t
z 2 z nh ng khu v k z 6 z
Phn p ng trc c a m ng k t ni t 25 2 bao ( ng 500
bao) theo cu d ng b khu ch i RF c s dng
khu ch i hi u, l i suy hao do p suy hao k t
chia p hoc r p p ng trc trung k c k t ni n optical node
d ng c a coaxial backbone p phi p k t ni nh p trung k
t i ngun AC t 60V n 90V. Ngun AC cung cp cho b khu ch
T p trung k , p p phi nh c k t ni n mt cng c a b
khu i trung k t n AC xu t.
2 Page 13
Cng c a b khu i trung k t n AC xu
t. Khi cn thi k khu p
phi nh s khu gi s t c u TV m
chp nh p p c m r nh m r
d r n l i ngun
AC tr k t b n tho i cn thi n d p p t
h thng ngu p ng tr k t cui r m r
bi ng s d u ni lo D n b o
v h thng t nh p t k m q
ng h p q u TV k t n ng
nh c a tt c t xu.
M ng HFC bao gm 3 m (s ) ng truyn d n (Transport
segment), m p p (D s s ) ng truy nhp ( Acess
segment).
nh S in t c m ng
ng t u n d n
ng truyn d
p u tuy ng truyn d p q t hay
mt s p q k t ni gi E s p s p, trong mt s
2 Page 14
ng h p k cp l k t gi s p v
th cp t q c li k t v E s
ng truyn d s l a ch n c a phn l
p d ch v qua m p gii bi nh m ni bt c a
h thng...
M ng truyn d n bao gm h th p q s p, nhi m
v c n d u t h k x s p
/p q / q n ti p u
quang t k
nh ng t u n d n
u t trung q chuy q u quang
s c truyn d q p s i quang t
th t tr p i n p u cho mt ph m vi ln
(gi p ) ch chia quang
hi u quang t q thu a h thng
u t n t i t c thi t k theo c
m ( ) s ( ) u sau n q c chuy n
i t q s s c truyn d p ng tr truyn d n
2 Page 15
n tng h q p ng trc nh khu
hi chia cao tn.
ng h n hi
M p p u bao gm h th p q c Hub th cp
q u quang t s c chuy n
t q truy c l ng h p m ng 2
chi u t m ng truy nhp s c thu t q
q truy n Hub v headend.
ng t u nh :
M ng truy nhp bao gm h th p ng tr t b p
t m v truyn t u cao t q t
b k p c v c a m ng con truy cp t
kho ng 300m.
M ng truy nhp truy u t node quang t ng
2 k
Mng truy nhp kiu HFPC (Hybrid Fiber Pasive Coaxal):
ng lai gi p q p ng tr
thi t b th k k t thi t b
m ng trc.
nh 5 u t c m ng t u nh
2 Page 16
c im ca m ng t u nh
+ p x ng theo m ng 1 chiu hay 2 chiu.
+ S d q s t ln.
+ M ng quang chi m t tr ng l m ng tng th .
+ M ng trc ch n tr p
v t b chia th ng.
+ Kh p c v t 400-600 t / q
u im:
+ Ch u t k s d khu i.
+ D k s d khu i cao t p
t, v
+ t b th k u 2 chi n
nh m ng v n cao khi tri n khai m ng 2 chiu.
+ S / q k p tt d ch
v 2 chiu vi t cao.
+ Gi p p ngu n, b ng, thay th t
b c.
h c im:
+ Kh p c a 1 node quang nh k s dng khu ch
i.
+ Y u node quang s dng ph s t ln, ch ng cao,
nh.
Mng truy nhp kiu HFC (Hybrid Fiber Coaxial)
m ng lai gi a p quang p ng trc trong s dng thi t
b c c ( b khu ch i cao tn ) m ng ng trc.
2 Page 17
nh u t c m ng t u nh
c im ca m ng t u nh HFC:
+ p x ng theo m ng 1 chiu hay 2 chiu.
+ M ng trc chi m t tr ng l m ng tng th .
+ M ng tr 3 p:
- Cp tr p ng trc tr k i
trc, b ng trc.
- Cp tr p ng tr khu i
- Cp m p ng tr
+ Kh p c v t 1500-2 / q
2 Page 18
u im
+ Ph m vi bao ph c a 1 node quang ln nh k ng trc
bi s d k i cao tn.
+ p u thp nh s d q
h c im:
+ Ch u thp k u m ng HFPC.
+ n l i khi tri k ng 2 chiu.
+ Y u cht ch v ngun cp u, n m cp ngu
m n tuy p s u.
+ ng phc t p.
S nh v
q k
q s x k q
p
k k 2
2 Page 19
2 T u n d n t n m ng
1.2.1 T u n d n t n m ng
Truyn d n trong m ng H c ch 1 7
nh 7 S truyn d n t n m ng HFC
nh 8 ng d h ad nd n c c thu a
2 Page 20
s t k p
v tinh, ngun qu s i i
p k q s ( ) u
c truyn t s p. Mi Hub
s p cung cp u ho kho 1 k ng 4 hoc 5 Hub th
cp i h t, mi Hub th cp c s d p p i ph
hi hoc s p k i m m vi p k
Video t s p cp k u chiu ti hoc chiu
xung t i tin tc t / ff i dung video, tho
d li u chiu lui hoc chi i tin tc t n
/ ff u khi n STB, d li i.
k s c c chia s s d
m ng backbone. M k x ng theo ki s d
ngh SONET/SDH hoc mt s c quyn.
m c O E / D p t d li u t t
OC-1(51,84Mb/s)/STM-1 (155,52 Mb/s) t gp n t
Trong m O E / D c s u ch p
k D c truyn k OC-12/STM-4 (622 Mb/s) ti
OC-4/STM-16 (2448 Mb/s). s dng k thu p k k D
r n s d p k k D c hi n cp p k
th th c hi ch v i qua m ng
O E / D n m D q x nh
bi s p q nh vi
kho 1 c c ln vi kho 2
p s Op s ( Os) p p p p gi
ch v b p q p ng tr p p
th truy v n s dng r u
ch k p p p s d truyn
d k q k k chi m
6 z k t tn s s ( k 2
2 Page 21
n s 2 z) k m gi k n k .
k V s t o ra m n video hi u qu
MPEG-2 hoc MPEG- k Q (Q p )
1.2.2 Thit t u n d n t ng m ng
1.2.2.1. B khuch i hai chiu
Trong phn m ng p ng trc, b khu ch i hai chiu c s dng bao
gm hai lo i:
- B khu p p i ( khu 2 u
p k )
- B khu rng Line Extender Amplifier mt h thng
HFC hi n 6 b khu i cho tng khu i RF sau mi
node.
s khu ch t u ch p nh k
nhi s p ng tn s.
nh : B khuch i 2 chiu
2 Page 22
1.2.2 2 quang v c ng trc trong m ng
nh 0: Kin t c m ng truyn h nh c truyn d n bng c quang v c
ng trc
quang
M p q a t 12 n 14 s q k mi lo p
Lo i s p c s dng s - s k ng 0,4
dB/km s ng l=1310 nm hoc suy hao 0,25 dB/km l=1550 nm(mc
s nh trong d i nhi c lp vi d i tn s n).
nh : c i c quang
2 Page 23
ng t c
n xu p n q k n nht (t 7 n
1,09 cm) ch ng tt nht, suy hao 45 dB/km 750 MHz hoc 9dB/km 40 Mhz.
n cui g s k ng 25 cm k , suy
hao kho ng 114 dB/km 40 MHz (m s p thu u
c p)
nh 2 c i c ng trc
1.2.2.3.Cu r (Tap)
Mi cu r 2 p n t ch k p chia
s s s ng cng c a cu r (
th 2 ) k p m v ng 1 s u
x nh.
nh : B chia tn hiu truyn h nh c Pacific 1 v 4 ra
2 Page 24
( p) 1 12:
H nh 1.14: Cu r Ta v t u n d n
1.2.2.4. Node quang
phn t nm ng ranh gii gi a p quang p ng trc, nhi m
v b n chuy n i hi u n cho ng xung ( c l i ) khu
p phi m ng p ng trc vi 3 hoc 4 u ra mi node.
nh 5: Node quang
1.2.2.5. Thit b kt cui truyn h nh STB (Set-Top-Box)
Thi t b k t cu u truy i hai lo s.
k
k p q n m q
p p d ch v x p t s d ch v c bi k c thanh
s d n tho ho
m n 1996 STB s c gii thi u vi mt s ch n:
2 Page 25
+ D k s d ch v t trong d i tn ng xung .
+ Gi i u ch k s thu c. u ch k s p
+ Gi i / k ch n.
+ Qu n hi u bao t Headend.
Cung cp giao di i s dng. G i ti c
tri n khai b / s s kp
p p p p bao s dng d ch v truyn
d ch v p p s
i ti n ho t c RGW.
p giao thc IP n thi t b IP voice, IP
videophone.
Truyn t i, x u truy p i cao HDTV.
nh : Set Top Box trong truyn h nh c
1.2.2 d m c a d m
t b n p p p
( ng ) p n v i
p
+ Lo i khi c k t ni v q k t n E (
th k t n E p
a mt b nh tuy n ) hoc giao di n k t ni USB.
2 Page 26
+ Lo i card cm n ng c i
nht song ch s ph i
s thi t k k x ay.
+ Lo i th ba c p p i
ti
nh 7 d m c
1.2.2.7. H thng kt ni m d m c CMTS
H th m trong Headend, thuc v k a m ng so vi modem
p t b k t ni c ng t p
p n gi p ng
Internet IP.
+ u ch t DSLAM trong h thng DSL.
+ m k
nh tuy k t n ng Internet.
+ Mi CMTS cha mt hoc nhi ( )
CMLC chuy s li ng xu ( n
) s q t k t
k k x p u truyn
c l i v t s server trong m ng modem
p D (D ) x nh bi RF2181.
p a ch IP theo nhu c p t b
s D ( f D ) x nh b 6
nhi m v s ki th
2 Page 27
ch TFP ( Trivial File Protoco ) x nh b 13 k
t i v f p ch v .
1.2.2.8. H thng IP Phone
thng s dng giao th truy u tho i qua m ng vin
c chu n cho lp chuy n m ng
LAN, WAN,... M ng IP m ng s li c lp vi lp v p c h
thng truyn t i tho n trong vi c t o thun l i
HFC th c hi n mt xa l c s truyn m i lo u : voice, data,
video. H th s dng thi t b k t cu n tho i IP phone hoc
n tho i truyn thng POTS phone k t ni vi m p / t STB s.
p t b k k k t n n mt t s h u
k t n n cng Ethernet chu n trong m p / t STB s / mt PC trong
p t thi t b a ch a
k t ni m O p n m p / s ph i
giao di n m p p / s cung cp
ch
1.2.2.9. H thng thit b thu a v tnh c c d ch v
m ct y u nh i v p d ch v truy ti
th qu p c c ch v. M p p p p
u qu nh s d u ( ch nh
p d ch v p p c gi xem ).
H thng qu truy nhp c c g thng truy
nhp u ki n.
1.3. IEEE 802.14
EEE 2 1 11 1 chu n
p v ( Y ) p u khi n truy nhp p n (MAC layer)
cho thng HFC.
2 Page 28
MAC layer:
H tr ch v ss -oriented
H tr QoS.
H tr CBR, VBR, ABR.
H tr ch v unicast, multicast, broadcast.
PHY layer:
m thi t k tham chi u.
H tr sub-sp ( z z ps ) -sp ( z12
z ps ) -sp ( z1 z ps )
S dng l i tn s chi
L a ch u ch QAM 64 cho chiu xung.
QAM-64 vi 6 bit/Hz t o ra 30 Mbps trong 6 MHz.
u ch QPS c ch n cho chi ch ng nhiu ln.
k k u xung.
n k thu u ch s dng 5,12 Msymbols/second cho chiu xu
mt k thu u ch s dng 1,28 Msymbols/second cho chi
Tc bit c a k thut u ch
QPSK: 2 bits/symbol x 5,12 Msymbols/second = 10,24 Mbps.
16 QAM: 4 bits/symbol x 5,12 Msymbols/second = 20,48 Mbps.
64 QAM: 6 bits/symbol x 5,12 Msymbols/second = 30,72 Mbps.
256 QAM: 8 bits/symbol x 5,12 Msymbols/second = 40,96 Mbps.
QPSK: 2 bits/symbol x 1,28 Msymbols/second = 2,56 Mbps.
1.4. Kh n ng ng thng
Ph k u xu z7 z
Ph k z 2 z
Ph z7 z 33 k 6 z
2 Page 29
Ph z 2 z 2 k 1 z
Chiu xung:
Q 33 k D x 1 2 ps/k = 337 ps
16 Q 33 k D x 2 ps/k = 1 13 ps
6 Q 33 k D x 6 ps/k = 13 1 ps
Chiu n
Q 2 k D x 2 6 ps/k = 1 ps
5 t t n
Cu POST HFC c ch ra trong 1.15. Mt b chuy n m ch
hoc DLC (Digitar Loop Carrier: b cung cp s) t t i headend.
B u khi n headend nh k i t t t
q D c b chuy n m ti nh x
DLC k T1 truyn d ch tho i s c k t n n mt t
class 5 g x c g i.
c trang b a t n m ch
class 5, vi kh th c hi n:
nh 8: Headend vi c c h n ng OST v
Chuy n m ch ni h t.
c.
2 Page 30
R t ng truyn t i h p tr c ti p
ng truyn t t ki p p
cho k
c trang b u khi ch v
k t vi m ng internet. B u khi n headend s n giao
x
X ( t chuy n m ) ruy nhp ATM
k t n n d n b chuy n m ch ATM trong m
cng. B u khi p li u,
video ho ch v CBR. Di p
ANI.
u nh c im ca m ng
p q s s
p q s p k D c ln, suy hao
u rt thp nhi n t, ch c tt. V s i
q c s n xu hi s q p p n
n s THz (10145 - 1015 Hz). u
p ng m u d ng truy k t
p n truyn d k c.
u quang truyn s i quang hi n nay ch y u nm trong 2 ca s c
s q 131 1 2 a s s u rt nh 3
/k s 131 2 s 1 k i mt
s p ng trc lo i suy hao thp nh p i mt 43dB/km t i tn s 1 GHz.
u truy s p u quang, v k ng bi
n t t ng d n m b c ch ng
truy c ch t o t s s q t
li k c d c a s i cao.
k p ng h p s i quang b t.
2 Page 31
M m i thi k ch u truy
ng con truy nhp v n s d t b khu u
nh s p truy x k
m p , trc trc c a m ng truy p p n ln x y
khu t b p t b m r i
vi nh v , sa ch k th c hi n nhanh
n ch ng phc v k a m ng. V ng truy
nhp ng trc, khi cung cp d ch v 2 chi khu i c p phn t
khu nh c a m ng gi m. Do
v x gi ang chuy n dn sang s dng m ng truy nhp th ng.
1.7 An t n t ng mi t ng HFC
1.7 ii thiu
t ch rt quan tr ng k t k p n internet. Hu
h t tt c ng d u mt m
cp s
+ Nh i s dng d ch v (Users).
+ Nh q (Op s)
+ q p (Government agencies).
V p i s dng d ch v m b
n d li x k k t d ch v.
V p q n d li u,
c lp, gi i v k x
k n hoc la g m gi
khi d ch v k ng do s c p d ch
v/ q ng cn s gi p d n trong kinh doanh c a
h c a h i v k ng.
2 Page 32
V p q p h p l v
th q p p t, nh m b o l ch v, c
m o v s t.
Vi nh ng v t ra c v an
t b m nh ng ch ng dng
k u khi ch v m:
+ u khi n truy nhp.
+ X
+
+
1.7 2 An t n v m t trong m ng HFC
t trong m k nh ng m k t
n m- m truyn th ng h p c p ng, m
cp k t ni tr c ti p n mt m i t i h t, vi c nghe
trm th c hi k i v
k b s i s dng nh k
mt m p v k k p
v p ng HFC hai chi
n d n nhiu- n-m t- n-nhi t trung k .
c u cu an t n t i lp MAC:
C gng t ng truy nhp p
s s ng truy nhp p k
ch s
X ( ) p i t x p l i vi
m ng truy nhp. p x nh thi t b c
quyn phc v a nh i vi profile c a d ch v. S phc t p c a
q x c ph i thi n ra c
i xng.
2 Page 33
M ( p on): D li n
HFC ph mt.
B o v s p i (Replay protection): M ng truy nhp ph c b o v
n s p l
Qu k ( ) D i s dng
i vi bt k m
S thun l i v i s d u cu (E s )
ch k i s d u cui
th ng h tr i v thng.
su ( sp ) p i ho ng
k p c a d ch v (CoS-Class of Service) cung cp
i s dng.
Kh x t kh (Exp ) ng truy nhp p n
s s s dng world wide. Rt nhiu qu q nh
v s dng, nhp kh x t kh t
p ng tri q nh v xut kh p
kh u.
Truyn d li u tin c (D sp ) ng truy nhp
ph n chia s ph s i bit sao cho ti thi u m
rng l i bit c a m ng truyn d p k
k i bit b n do vi c m rng l n. H
thng ph k p ng b m c s k s n
truyn d n d li u.
( s s ) p p n chia
s ph k thu p n t c i tr
thu i m ng HFC.
p c s ( ) ng truy nhp
p n chia s ph c thi t k s k t lp
l o m ( k )
2 Page 34
Kh p ( p )
m ng truy nhp p n chia s ph p p p hay thay
m
M t m v gii m t m
M i m c th c hi n bng thu DE m s
d ( p k )
t s v v k thut m n bi s
M s dng ph c ch n.
M p c th p n cng hoc phn mm.
M p k u. D li s k
m k
Mt p tr
Gi i m p i gii h n khu i li.
M p i t ng b .
V c EEE 2 1 k t h p k thut m thng
MAC sao cho truy a mt tr x c. Th c
hi u n s bi a ch i nghe tr tht gi
p n d n chia s Q s
k ( x ) EEE 2 1 ngh s dng giao thc
k D ff -Hellman cho HFC.
Provisioning: Trong ch p p k
Chng th c ID c s c s d x
p p p c cn thi truy nhp
d ch v k D p n c bao (certification number or serial
number c a thi t b ) s d k t Diffie-Hellman.
k ( s ) u
ID duy nht c q p
p p ( q p s ) s x k t trao
th k ng th D c s d x
2 Page 35
th p p p k p nh D
k tht b i.
k t Diffie-Hellman: Thu p p i s
d k m
k k m i m
Thu D ff -Hellman d k t ri r c trong
s s i vi ng.
2 Page 36
2 A E ODE
2 Kh i nim v cng ngh Cable Modem
( ) truyn s li ng truyn
p ( ) ng lai gi p q p ng tr cung cp
u mt chiu.
M ng Internet c a truy p ng truy cp q
p
nh 2 h nh a d m
2.2. L ch s v mc ch a i ca cng ngh Cable Modem
p ln cung cp d ch v t 1
hi n nay Vi t Nam d ch v ng d k
D ch v cable- c cung cp m u megabit.
M g cung cp th c s s i ph thu p d ch
v i v k c x p p p O O
D a Cable Modem (CM) s thy
t d ch v rt tuy t, tuy n k s ng
d ch v s gi m xung.
n ch i s dng VN
ng gp ph i hi n nay khi s dng truyn s li u qua h th n tho i
h n v t . Vi chu mi V90, t t 6 ps
c s dng gi a thi t b c k
2 Page 37
cp d ch v tho p p p mt d p ng truyn
thng. M i c ng ngh ng nh p s
dng nh ng ng dng, d ch v m c tr c tuy n, xem phim
tr c tuy u k t ni m ng, truyn s li u t cao...Cable Modem cho
p p p Internet t mt phn nh c a thi
p s n thng dial- p
1) ng m i k t n n m
2) ch v " " k
h mun, khi h mu p p p
gi n tho i m c a h i vi cuc hi tho i bng
gi
2.3. C u t c ca Cable Modem
2 S c u t c ca Cable Modem
Cable Modem gm lo i lp p ng h p
p trong hp thu Set- p i ph i
t b p c chu u khi n khi k t ni Internet. Th c t k
th p ng Digital Cable, hp thu set- p k
k t ni th q ng k t n i s d
nhp Internet hay k
D lo s c t d
sau :
nh 2 2 S c u t c a d m
2 Page 38
Tuner - B u ch u.
Demodulator - B gi u d ng s.
Modulator - B gi u t dng s sang dng tu n t .
Media Access Control(MAC) - Thit b u khin truy nhp
Microprocessor - B x l
2.3.1.1. Tuner
Tuner-B u ch phn ni Modem Cable v p
hi u hoc vi b p k li u Internet ra kh k
ng. T li c Tuner ti p nh i d u s
s n t D p
t thi t b D p x p p s dng m n tn s (trong kho ng
42- z) D w s k ( k ng 5-42
MHz) cho Upstream.
p n c a b p s c thi t
k c s d ng dng trong k t qu c a vi c
p mt b l p
nh 2 h nh T ER-CABLE MODEM
2 Page 39
2.3.1.2. Demodulator
p c s d gi u ch
q ng trong vi c gi c chuy i t d
sang s.
D QAM (Quadrature Amplitude
Modulation) s u tun t g m c s
p i chuy s gi x i A/D Converter
(Analog to Digital Converter). A/D Converter nh u bi i theo
p i s 1
B sa li (Error Correction Module) s c ki n
s s i d li u chu n do v x y ra khi truyn d li
c ki k c phc. Trong hu h ng h p li u hay
w k f E t thi t b ng b E c s d
chc chn rng m i d li m b o truy
Ch th c p s
B nh p thng tin a li:
B nhp sa l (E ) p m
v ki s s d so
s i d li u chu ng v x y ra khi truyn d li u,
n s c s ngay lp t c khc phc.
B iu ch in cu h ng QA
B u ch c p Q (Q p )
n vi nhi m v truyn t u ch
c li u b i c
p s Q t d s t d s
Cosine v p o tn s chuy c giao gi a
s s p p n d li ng th k X x t chu
k s s
2 Page 40
nh 2 h nh iu ch QAM
B chuyn i D/A ( Digital to Analog Convenrter)
Chuy i s s y m c bi u di i
d s ( ) n th ho n t l
v s p p p c s d chuy D/ p
p p n tr p p p n tr
khi c a mt chuy i D/A:
nh 2 5 S khi b chuyn i D/A
2.3.1.3. Media Access Control (MAC)
MAC- u khi n truy nhp ng con giao thc truyn
d li u, mt phn c a t k t d li O p
a ch u khi n truy nhp k p p m cui hoc
c v t m ng.
2 Page 41
t t a vi giao th p
(multiple access protocol), do tng con MAC cung cp. Vi p p u tr m
k t ni t ng v
i vi Cable Modem p p ps
D w s th c ch n gi a phn c p n mm c
thc m k M i thi t b m i vi
p c t p u so v ( )
a MAC s do q nh.
hi ng s d a ch v
t b m ng, p t b v s d ng m ng.
2.3.1.4. Microcessor
ss t b vi x k t h p a mt b x
( ) t m p duy nht , hoc m p t
thi t b lp x nh t s n.
i vi Cable Modem, nhi m v c a b x p thu c Cable
c thi t k vi m s d n hay ch cho m k t
ni Internet ng. ng h p p trong PC, b x p
s t c a MAC.
2.4. h nh in t c h n p cable modem
EEE 2 1 x u khi n
headend. Ki t kh u tng c x nh ki
p p ng ki t d x
thi t b .
k p p / 3 1
g
+ ( )
+ Lp v (p s ( Y) )
+ Lp MAC (MAC layer).
2 Page 42
nh 2 h nh in t c h n p ca Cable Modem
U EEE 2 1 p i
chu p v
+ k
+ k u xung.
+ S hi t k thut.
2.5. Ph cable modem
Ph tn s c a chi u xu k
MHZ t Z Z k u xung,
bao g u ch Z Z n
Z k s chi k rng t 1 Z n 6
Z k s trong tm t 1 6 ps n 10 Mbps khi s
dng k thu u ch Q k c thi t k truy
u khi li n headend. Mt s ng l k u xung
nm trong n 300 MHZ gi Z 7 Z k c
p q li c t n tt c tr m thu.
2 Page 43
nh 2 7 h RF ca Cable Modem
2 nh ca cable modem
Truy c tt nh
3.3. Mt b (x t tr ) c k t n n tt c
k 6 Z u xung (t k 1 k ) a ph. Cable modem ph
kh u chnh b c b k n 6 M Z
nhn d li u t headend. T i k t cu p p k
p k k 1 k trong
2
nh 2 8 nh ph Headend/station
i tho i gi c khi t o khi mt modem lp t
ng b u l k u xu k n thi t b
c p ng l i bi vi c ch k p
truyn d li u c thu c k
2 Page 44
chiu xu k t v k i tho i gi a
s p qu n tr MAC ch m.
Kh s ng v th c
tham chi f q -agile cable modem.
2 7 c thnh hn ca h thng ca m d m
nh 2 c thnh hn ca h thng Cable Modem
Mt h thng CM bao g p n sau:
- B khu i 2 chiu.
- p q p ng trc trong m ng.
- Cu r (Tap).
- Node quang.
- Thi t b k t cui truy -STB.
- p( )
- H thng k t cu p
- Server trong m p
- H thng IP phone.
- H thng qu c d ch v.
2 Page 45
p k 2 p q p
1 p s p p
k p s p
2.7.1 d m c CM
thi t b n p p p n m
( ) p n v 3 i
p
+ Lo i khi c t n q k t n E (
nhi k t n E p
ch a b nh tuy n) hoc giao di n k t ni USB.
+ Lo i card c ng c
nht song ch s ph s
thi t k k x
+ Lo i th ba c p p i ti n
2.7.2. H thng kt cui m d m c CMTS
H th m trong Headend, thuc v p k a m ng so vi
p t b k t cu p
Headend c p n gi
p ng Interrnet IP.
+ u ch t DSLAM trong h thng DSL.
+ m k
nh tuy k t n ng Internet.
+ Mi CMTS cha mt hoc nhi p ( )
CMLC chuy s li ng xu (
) s k k x
p u truy c l i v ng
2 Page 46
2.7.3. Mt s server trong m ng m d m c
D x nh bi RF 21 1 p a ch
IP theo nhu c p t b s
D x nh b 6 m v i gian
s ki thng.
x nh bi RFC 1350 k i v f u
p ch v .
2 8 c chu n c dng t ng cng ngh a d m
nh 2 a h thng chu n a d m in h nh
p h s dng nhi o th c quy k
k s d p a nhiu
k t h th 1 7 3 n ni tr
EEE 2 1 D /D i di i di n cho Bc M vi
2 Page 47
b giao th DO n nay, nh ng chu ng c i ti n
l s c th p
+ DOCSIS g 3 1 DO 1 1 DO 2 DO c
p n b s c chu bi ITU.
+ D p x n m
D /D i D
chu n 1.0(12/1995), 1.1(9/1996), 1.2(12/1996). M y u c p
b tr ng d ch v s li u .
k p n sau (DAVIC 1.3;1.4;1.5) ch y tr
d ch v qu s ch v truy k
+ EEE 2 1 n cho lp v p p MAC cho m ng HFC
s ng. Ph m vi s dng c EEE 2 1 n d q ng
p truy cp Internet t
Bng 2 c tnh ca c c chu n s dng t ng cng ngh Cable Modem
m DOCSIS 1.x Euro-DOCSIS DVB-RC
T ng xung
64-QAM:27Mbps
256-QAM:42Mbps
6 z
64-QAM:38Mbps
256-QAM:52Mbps
z
64-QAM:38Mbps
256-QAM:52Mbps
z
T
320, 640, 1.280,
2.560, 5.120
(Mbps)
QPSK
6 1 280, 2.560, 5.120,10.24
(Mbps)
16-QAM
5-42Mhz
320, 640, 1.280,
2.560, 5.120
(Mbps)
QPSK
640, 1.280, 2.560, 5.120,10.24
(Mbps)
16-QAM
5-65Mhz
1.554Mbps;3.088Mbps
Differential QPSK
5-65Mhz
ch v Truy nhp Internet,
VoIP.
Truy nhp Internet,
VoIP.
Truy nhp Internet,
2 Page 48
T U THAM KH O
[1] D ng truy nhp ng cho h X c vi n CNBCVT,
2007.
[2]. D ng: M truy nhp 6
2010.
[3]. Cablemodem.com
[4]. Internet
[5]. Ph m Th Thu 2 3.
[6]. zz sp s /2
[7]. Cable television technology & operation.
[8] s k