Dr. Morris Liaw Venkata Vijay Durbhakula Mahesh Molakalapalli.
Cable Modem : Technology Venkata C. Majeti 4343 … · Cable Modem : Technology Venkata C. Majeti...
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Transcript of Cable Modem : Technology Venkata C. Majeti 4343 … · Cable Modem : Technology Venkata C. Majeti...
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Cable Modem : TechnologyCable Modem : Technology
Venkata C. MajetiVenkata C. Majeti4343 Commerce Court4343 Commerce CourtLisle, IL 60532Lisle, IL 60532
Tel: (630) 281 - 3152Tel: (630) 281 - 3152Email: [email protected]: [email protected]
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Outline
Cable television network architecture
Migration of cable networks to hybrid fiber-coax networks
Use of cable RF spectrum
Recent changes to the use of RF spectrum
Developments in cable modem technology
Cable modem details:
Physical (PHY) layer specification and design
Media Access Control (MAC) layer specification and design
Data encapsulation
Signaling & Control
Data Over Cable Services Interface Specification (DOCSIS) standard
Other related standards: PacketCable, OpenCable, & EuroDOCSIS
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Cable Television Network Architecture
Summary - headend at a glance
channel lineup
Passivecombiner
Fiber Transmitter
videoreception
CMTS
Cisco 2500
Cisco 2500Ethernet switch
ForeATM
Switch
Scientific AtlantaRF upstream converters
Cisco terminal server
LAN
digital video storage batterybackup
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Migration of CATV Networks to HFC Networks
Community Antenna Television (CATV) network evolution :
( a ) “Tree and Branch” Architecture( b ) Capacity increase via “fiber trunks”( c ) Evolution to “Fiber Serving Areas”
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Migration of CATV Networks to HFC Networks
(a) traditional tree-and-branch architecture
main trunk
Headend/Hub
main trunk
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Migration of CATV Networks to HFC Networks
(b) traditional tree-and-branch with fiber trunks
main trunk
Headend/Hub
Node
Headend/Hub
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Migration of CATV Networks to HFC Networks
main trunk
Headend/Hub
NodeNode
(c) tree-and-branch with fiber-serving-areas
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Use of Cable RF Spectrum
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Use of Cable RF Spectrum
Headend
Cable distribution network has limited (shared) upstreamcapability in 5- 40 MHz range. Most cable systems use50 - 550 MHz range for downstream broadcast video signal.
5-40MHz
Upstreamsignaling
50 MHz - 550 MHz 550 MHz - 750 and up MHz
Downstream
. . .
1 NTSC Video Channel per 6 MHz RF Carrier
Bandwidth Use in CATV Networks
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Recent Changes to the Use of RF Spectrum
5-40MHz
Upstream
50 MHz - 550 MHz 550 MHz -
Downstream
. . .
1 NTSC Video Channel per 6 MHz RF Carrier
. . . .
Encoding schemes assume multiplexing of many DS0/MPEG channels to form one 6 MHz NTSC channel for distribution overexisting facilities.
Increasing the Cable Distribution Capacity
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Developments in Cable Modem Technology
ProductsZenith, LANcity, Hybrid Networks
Proposals
PHY Layer
Scientific AtlantaAmatiAlcatelCORTECStanford TelecomZenithGeneral InstrumentAT&T / LucentMicrounityIBMAware
MAC Layer
TDMAF-TDMAXDQRAPM3ADAPtUPSTREAMSCDMA/S-CDMASEMAPMLAPFPP
Key Issues
Modulation TechniquesUpstream NoiseData Link Layer FormatLoop length – propagation delayPrivacy over shared media
-----Ranging, RegistrationUpstream Frame FormatTiming Source & Uncertainties
Superframe
Frame
Slot
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Cable Data Network architecture
CableModem
O/ENodeFiber
TxRx
upst
ream
rece
iver
s
Demod
Mod
Net
wor
kIn
terf
ace
Telephony,Pay-Per-View...
dow
nstr
eam
com
bine
r
Cable ModemTermination System
Secu
rity
Aut
hent
icat
ion
Loc
al S
erve
rs
Alternativetelephone
return interface
Rou
ter
Inte
rfac
e
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Data Over Cable Service Interface Specifications (DOCSIS)
Cable Modem Termination System - Network Side InterfaceCable Modem - Customer Premise Equipment Interface
Operation Support System InterfaceCable Modem Telephony Return Interface
Radio Frequency InterfaceBaseline Privacy InterfaceSecurity System InterfaceRemovable Security Module Interface
CMTS-NSI OSSI RFICMCI CMTRI BPI
SSIRSMI
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RFI
• 6 MHz spectrum• 64/256 QAM • Reed-Solomon block code and Trellis Code• Variable depth interleaving to support latency• Contiguous serial bit-stream w/ no implied framing
Downstream
Upstream• Frequency agile• QPSK/16 QAM• Multiple symbol rates, data rates• CM programmable by the CMTS• Supports fixed-frame and variable length PDUs• Programmable Reed-Solomon block coding• Time Division Multiple Access (TDMA)
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MAC (media access control) Layer
• CMTS-controlled mix of contention and reservation• Stream of mini-slots in upstream• Fixed and variable-length packets• Extensions to support ATM PDUs• Support for multiple data rates• Support for multiple grades of service
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Routing
DATA FORWARDING THROUGH THE CM AND CMTS
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Summary
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Resources
Albert Azzam, “High-Speed Cable Modems,” McGraw-Hill Series onComputer Communications, Published in 1997.
Venkata Majeti (Executive Editor), “Cable Modems: Current TechnologiesAnd Applications,” Published by the International Engineering ConsortiumAnd the IEEE Press, 1999.
CableLabs: resource for DOCSIS, PacketCable and OpenCable initiatives.URL: www.cablelabs.com
Market Information: www.cabledatcomnews.com
Other market research information from various investment banks.