This document discusses different types of media used for data transmission and their characteristics. It describes guided media such as twisted pair cables, coaxial cables, and fiber optics, as well as unguided media like VSAT and satellites. It then explains several transmission characteristics including attenuation, noise, signal-to-noise ratio, and propagation delay.

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

2. 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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3. 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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4. 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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5. Types of Twisted Pair
UTP STP
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6. 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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7. 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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8. Coaxial Cable Cut away View 1/19/2015
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9. 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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10. 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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11. 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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12. 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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13. 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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14. 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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15. 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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16. 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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17. 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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18. “
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THANK YOU
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