Media Concept and
classification of Media
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Presenter:
Purushottam Dahal
https://www.facebook.com/puru.BIM

Contents
 Guided Media
 Twisted pair overview
 Coaxial cable overview
 Fiber optics overview
 Unguided Media
 VSAT
 Satellite
 Transmission Characteristics
 Attenuation
 Noise
 Signal to Noise Ratio
 Propagation Delay 1/19/2015
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Guided Transmission Media
 Purpose is to transfer raw bit stream
 Related with physical layer
 Various physical medias can be used
 Magnetic media, removable medias
 Transfer rate, depends upon distance and media
used. Same media may contain various transfer
rates with high degree of variation.
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Twisted Pair
 Bandwidth characteristics of Magnetic tape and other removable
media is excellent, the delay characteristics is very poor.
 Transmission time is measured in minutes or hours, not milliseconds.
 One of the oldest and still most common transmission media is twisted
pair
 A cable made by intertwining two separate insulated wires together
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Types of Twisted Pair
UTP STP
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Name Type Bandwidth Applications
Level 1 0.4 MHz Telephone and modem lines
Level 2 4 MHz Older terminal systems, e.g. IBM 3270
Cat3 UTP 16 MHz 10BASE-T and 100BASE-T4 Ethernet
Cat4 UTP 20 MHz 16 Mbit/s Token Ring
Cat5 UTP 100 MHz 100BASE-TX & 1000BASE-T Ethernet
Cat5e UTP 100 MHz 100BASE-TX & 1000BASE-T Ethernet
Cat6 UTP 250 MHz 10GBASE-T Ethernet
Cat6a 500 MHz 10GBASE-T Ethernet
Class F S/FTP 600 MHz
Telephone, CCTV, 1000BASE-TX in the
same cable. 10GBASE-T Ethernet.
Class Fa 1000 MHz
Telephone, CATV, 1000BASE-TX in the
same cable. 10GBASE-T Ethernet. 1/19/2015
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Co-axial Cable
 It has better shielding than twisted pairs, so it can span longer
distances at higher speeds.
 Two kinds of coaxial cable are widely used.
 One kind, 50-ohm cable, is commonly used when it is intended for
digital transmission from the start. The other kind, 75-ohm cable, is
commonly used for analog transmission and CATV, but is becoming
more important with the advent of Internet over cable.
 The construction and shielding of the coaxial cable give it a good
combination of high bandwidth and excellent noise immunity.
 The bandwidth possible depends on the cable quality, length, and
signal-to-noise ratio of the data signal.
 Modern cables have a bandwidth of close to 1 GHz.
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Coaxial Cable Cut away View 1/19/2015
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Fiber Optics
 A technology that uses glass (or plastic) threads (fibers) to transmit data. A
fiber optic cable consists of a bundle of glass threads, each of which is
capable of transmitting messages modulated onto light waves.
 An optical transmission system has three key components: the light source,
the transmission medium, and the detector.
 Conventionally, a pulse of light indicates a 1 bit and the absence of light
indicates a 0 bit.
 The transmission medium is an ultra-thin fiber of glass. The detector
generates an electrical pulse when light falls on it.
 By attaching a light source to one end of an optical fiber and a detector
to the other, we have a unidirectional data transmission system that
accepts an electrical signal, converts and transmits it by light pulses, and
then reconverts the output to an electrical signal at the receiving end.
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CONT……..
 Fiber optics has several advantages over traditional metal
communications lines:
 Fiber optic cables have a much greater bandwidth than metal
cables. This means that they can carry more data.
 Fiber optic cables are less susceptible than metal cables to
interference.
 Fiber optic cables are much thinner and lighter than metal wires.
 Data can be transmitted digitally (the natural form for computer
data) rather than analogically.
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A Bundle of Optical Fibers
The structure of a typical
single-mode fiber.
1. Core: 8 µm diameter
2. Cladding: 125 µm dia.
3. Buffer: 250 µm dia.
4. Jacket: 400 µm dia
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VSAT
 A very small aperture terminal (VSAT), is a two-way satellite ground
station or a stabilized maritime VSAT antenna with a dish antenna that
is smaller than 3 meters.
 The majority of VSAT antennas range from 75 cm to 1.2 m.
 Data rates range from 4 Kbit/s up to 4 Mbit/s; some upgraded
modules can even reach a max downlink of up to 16 Mbit/s.
 VSATs access satellites in geosynchronous orbit to relay data from
small remote earth stations (terminals) to other terminals (in mesh
topology) or master earth station "hubs" (in star topology).
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Satellite
 A satellite is an artificial object which has been intentionally placed
into orbit.
 Such objects are sometimes called artificial satellites to distinguish
them from natural satellites such as the Moon.
 Satellite is a specialized wireless receiver/transmitter that is launched
by a rocket and placed in orbit around the earth.
 There are hundreds of satellites currently in operation. They are used
for such diverse purposes as weather forecasting, television broadcast,
amateur radio communications, Internet communications, and the
Global Positioning System(GPS).
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Attenuation
 Attenuation is a general term that refers to any reduction in the
strength of a signal.
 Attenuation is a general term that refers to any reduction in the
strength of a signal.
 Attenuation occurs with any type of signal, whether digital or
analog.
 Sometimes called loss, attenuation is a natural consequence of
signal transmission over long distances.
 The extent of attenuation is usually expressed in units called
decibels (dBs).
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Noise
 Noise is unwanted electrical or electromagnetic energy that degrades
the quality of signals and data.
 Noise occurs in digital and analog systems, and can affect files and
communications of all types, including text, programs, images, audio,
and telemetry.
 In a hard-wired circuit such as a telephone-line-based Internet hookup,
external noise is picked up from appliances in the vicinity, from electrical
transformers, from the atmosphere, and even from outer space.
 Normally this noise is of little or no consequence. However, during severe
thunderstorms, or in locations were many electrical appliances are in
use, external noise can affect communications.
 In an Internet hookup it slows down the data transfer rate, because the
system must adjust its speed to match conditions on the line. In a voice
telephone conversation, noise rarely sounds like anything other than a
faint hissing or rushing.
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Signal-to-Noise Ratio
 In analog and digital communications, signal-to-
noise ratio, often written S/N or SNR, is a measure of
signal strength relative to background noise.
 The ratio is usually measured in decibels (dB).
 Communications engineers always strive to
maximize the S/N ratio.
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Propagation Delay
 Propagation delay is the amount of time it takes for the head of the
signal to travel from the sender to the receiver.
 Propagation delay refers to the time lag between the departure of
a signal from the source and the arrival of the signal at the
destination.
 It can be computed as the ratio between the link length and the
propagation speed over the specific medium.
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“
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THANK YOU
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