Cable Basics

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Cable Basics

• Week 14

ICS 620
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CABLE BASICS
ICS 620 Week 14
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Overview Cable TV Systems

• History
• Two-Way vs. Broadcast
• HFC Digital Systems

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History

• 1948
• Rebroadcast of basic TV channels
• Premium Channels (HBO)
• Pay per View (WWF, Rock Concerts)
• Local Origination (PEG Channels)
• Data (ISP IP telephony IP video))

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Frequency Allocation
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Cable TV Frequencies
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Cable TV Frequency Allocation
5 - 50 MHz Sub band Upstream Cable 54 -
88 MHz VHF-Lo Ch. 2 6 88 108 MHz FM
Radio FM radio 90 174 MHz Mid
band Downstream Cable 174 216
MHz VHF-Hi Ch. 7-13 216 300 MHz Super
band Downstream Cable 300 1002 MHz Hyper
band Downstream Cable 470 - 806 MHz UHF Ch.
14-69
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Cable System Architecture

• Antenna Systems
• Off-air microwave, satellite
• Headend
• Signal reception, processing and conditioning,
  scrambling (analog) or encryption (digital)
• Distribution Plant
• Amplifiers, Traps, Trunk, Feeder, Multi-taps and
  Drop
• Subscriber Equipment The Box
• De-scrambling or de-encryption

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Cable TV Tower
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Cable System
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CATV Headend
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Analog CATV Headend
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Spectrum Allocation with Sub band Reverse
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Basic Coaxial CATV System
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CATV Distribution Map
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Strand Map
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Distribution Cables
Trunk Lines - 3/4 to 1
in diameter Feeder Lines - 1/2
in diameter Drop Lines - 1/4 in diameter Trunk
Amplifiers - Every 2000 feet Bridger Amplifiers -
Every .35 to .5 miles
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Coaxial Cable Signal Loss
The principal negative of coaxial cable is its
relatively high loss over distance. Coaxial
cable signal loss is a function of its diameter,
dielectric construction, temperature, and
operating frequency. A ballpark figure is 1 dB
of loss per 100 feet.
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Coaxial Cable Signal Loss
Ch. 2
Ch. 13
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Coaxial Cable Signal Loss
Example The logarithm of the attenuation of cable
(in dB) varies with the square root of the
frequency. The attenuation at 216 MHz (Ch. 13)
is twice that of 54 MHz (Ch. 2) since the
frequency is four times as great. Thus, if Ch. 2
is attenuated 10 dB in 1,000 feet, Ch. 13 will be
attenuated 20 dB.
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Two-Way vs. One-Way

• Splits (sub band v. mid band)
• Change in perspective by user
• New services
• Digitization

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CATV Multiplexing
f2 f1
Time Division Multiplexing
FREQUENCY
t1 t2 t3 t4
TIME
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Feeder Network
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CATV Trunk Station
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CATV Trunk Station
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Code Operated Switch
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Two Way Distribution Network
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Subscriber Pedestal
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Multi-Tap
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CATV Set-Top Box
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Problems with Broadband Tree and Branch

• Most Cost Effective with Broadcast
• Limited Serving Area
• Amplifier Cascades Limit Performance
• Serial String Reliability
• Serving Area Shrinks as Bandwidth Increases
• Reliability of Local Powering
• Security (traps scrambling)

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BREAK
10- minute break
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Modern Cable Plant Architecture
Hybrid Fiber Coax (HFC)
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Analog Headend with AM Fiber
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AM Fiber to the Bridger
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From Analog to Digital

• 1989 (General Dynamics)
• MPEG Compression
• 10 channels of video in the 6 MHz bandwidth
• Amplifier cascades reduced from 30 to six or
  fewer.
• Given 550 MHz of bandwidth, nearly 1,000
  channels of digital video are possible.

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Todays Typical CATV System

• Fiber/Coax Fiber to the Bridger Architecture
• Serving Nodes 500 - 2000 House holds passed
• Downstream Bandwidths 550 - 750MHz, a few 1GHz -
  Actives
• Most use or consider 1GHz passives and spacing of
  apparatus. The media is capable of transmitting
  frequencies up to 3 GHz.
• Upstream Capability in 5 - 50 MHz band
• Some systems have High reverse

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Fiber Optics
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Fiber Optic
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Total Internal Reflection
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CATV Fiber Network
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CATV Digital Headend
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Digital CATV Spectrum Allocation(ANSI/EIA-542-199
7)
Analog Channels Ch. 2-78 55 MHz to 547
MHz Digital Channels Ch. 79-136 553 MHz to 865
MHz
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Digital CATV Spectrum Allocation
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Fiber in the CATV Network

• Fiber Optic will increase quality, reliability,
  and operational savings.
• Fiber Optic is economically competitive in
  comparison with coaxial cable.
• Fiber Optic offers the opportunity of two-way
  services, fact that will increment revenues for
  the company.
• Fiber Optic networks are fully expandable, with
  large capacities to provide countless services.

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What about data?
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Inside the Cable Modem

• Tuner
• Demodulator
• Modulator
• Media Access Control (MAC) device
• Microprocessor

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Cable Modems Whats Inside?
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DOCSIS
Developed by Cable Labs and approved by the ITU
in March 1998, Data Over Cable Service Interface
Specification defines interface standards for
cable modems and support equipment.
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Cable Modems
DOCSIS specifies downstream traffic rates between
27 and 36 Mbps over RF paths in the 50 MHZ to 750
MHz range, and upstream traffic at between 320
Kbps and 10 Mbps over an RF path between 5 and 42
MHz.
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Cable Modems What is Downstream?

• What the Cable Modem receives
• Frequency 50-750 MHz
• Bandwidth 6 MHz (USA) or 8 MHz (EU)
• Modulation 64-QAM (or 256 QAM)
• Data-rate 27-56 Mbit/s (4-7 Mbyte/s)
• Continuous stream of data
• Received by all modems

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Cable Modems What is Upstream?

• What the Cable Modem transmits
• Frequency 5-42 MHz (5-42 MHz)
• Bandwidth e.g., 2 MHz
• Modulation QPSK or 16-QAM
• Data-rate e.g., 3 Mbit/s (400 KB/s)
• Transmit bursts of data in timeslots (TDM)
• Reserved and contention timeslots

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What does Cable Modem mean?

• CABLE is short for Cable TV (CATV) Network
• MODEM is MOdulator-DEModulator
• Actually more like a network adapter than a modem

CMTS (Head-End)
Cable Modem
Upstream Demodulator QPS K/16-QAM F 5-65 MHz BW
eg 2 MHz Rate eg. 3 Mbit/s
Upstream Modulator QPS K/16-QAM F 5-65 MHz BW
eg 2 MHz Rate eg. 3 Mbit/s
Downstream Modulator 64-QAM/256-QAM f65-850 MHz
BW 6/8 MHz Rate 27-56 Mbit/s
Downstream Demodulator 64-QAM/256-QAM f65-850
MHz BW 6/8 MHz Rate 27-56 Mbit/s
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What is a CMTS?
A CMTS is a Cable Modem Termination System, or
router, which is a device located in the cable
head-end that allows cable television operators
to offer high-speed Internet access to home
computers.
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CMTS The Cable Modem Termination System
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Cables Future

• Integrated Carrier (Voice, Data, Video)
• High Bandwidth (Ultra Wideband)
• HDTV (Next Week)
• IP Telephone (VoIP)
• PCS Provider (Wireless)

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Ultra Wideband
Previously classified military technology, Ultra
Wideband radio broadcasts digital pulses that are
timed very precisely, on a signal occupying a
very wide spectrum at the same time. UWB can
peacefully co-exist with broadband cable
technology without interference.
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Ultra Wideband
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Ultra Wideband
Experiments have achieved 1.2 Gb/s downstream and
120 Mb/s upstream per node. UWB technology could
easily double the capacity of existing copper or
hybrid fiber-coax systems today.
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Ultra Wideband
UWB signals are injected into existing cable
systems. Because these pulse code transmissions
are very low amplitude, the signals ride below
but do not interfere with existing digital or
analog cable signals. A typical 500 MHz UWB
signal can easily propagate throughout a cable TV
network, both copper and hybrid fiber-coax.
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UWB in Cable TV
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Ultra Wideband
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Voice over IP (VoIP)
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VoIP Business Case
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VoIP Models
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Video Phones
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Questions and Answers