This document discusses different types of transmission media used to transmit signals and data in communication networks. It describes guided media such as twisted pair cable, coaxial cable, and fiber optic cable, which provide a physical path for signal propagation. It also covers unguided or wireless media that transmit signals through air using radio waves, microwaves, or infrared. The key characteristics, applications, and performance of each transmission medium are outlined.

1. BY KINISH KUMAR(www
.kinishcybersec.blogspot.in)
http://www.facebook.com/kinishkumar

2. Transmission media
 Transmission media
are located below the
physical layer
 Computers use signals
to represent data.
 Signals are ransmitted
in form of
electromagnetic
energy.

3. Transmission Media
Transmission Media and Physical Layer

4. Transmission Media
 Guided Media (Wired)
 Twisted-Pair Cable
 Coaxial Cable
 Fiber-Optic Cable
 Unguided Media (Wireless)
 Radio Waves
 Microwaves
 Infrared

5. Classes of transmission media

6. GUIDED MEDIA
Guided media, which are those that provide a conduit
from one device to another, include twisted-pair cable,
coaxial cable, and fiber-optic cable.

7. Overview
 The transmission media that are used to convey information can be
classified as guided or unguided. Guided media provide a physical
path along which the signals are propagated; these include twisted
pair, coaxial cable, and optical fiber. Unguided media employ an
antenna for transmitting through air, vacuum, or water.
 The characteristics and quality of a data transmission are determined
both by the characteristics of the medium and the characteristics of
the signal. In the case of guided media, the medium itself is more
important in determining the limitations of transmission.
 For unguided media, the bandwidth of the signal produced by the
transmitting antenna is more important than the medium in
determining transmission characteristics. One key property of signals
transmitted by antenna is directionality. In general, signals at lower
frequencies are omnidirectional; that is, the signal propagates in all
directions from the antenna. At higher frequencies, it is possible to
focus the signal into a directional beam. In considering the design of
data transmission systems, key concerns are data rate and distance:
the greater the data rate and distance the better.

8. Data Rate and Bandwidth
 Any transmission system has a limited band of
frequencies
 This limits the data rate that can be carried

9. Design Factors
 Bandwidth
 higher bandwidth gives higher data rate
 Transmission impairments
 eg. attenuation
 Interference
 Number of receivers in guided media
 more receivers introduces more attenuation

10. Guided Media – Twisted-pair Cable
Twisted-pair cable

11. Twisted Pair

12. Twisted pair
 One of the wires carries signal, the other is used only as a ground
reference.
 The receiver uses the difference b/w the two levels.
 Twisting increases the probability that both wires are effected by
the noise in the same manner, thus the difference at the receiver
remains same.
 Therefore, number of twists per unit length determines the
quality of the cable.

13. Twisted Pair - Transmission
Characteristics
 analog
 needs amplifiers every 5km to 6km
 digital
 can use either analog or digital signals
 needs a repeater every 2-3km
 limited distance
 limited bandwidth (1MHz)
 limited data rate (100MHz)
 susceptible to interference and noise

14. Unshielded Versus Shielded Twisted-Pair Cable
UTP and STP cables

15. Unshielded Twisted Pair (UTP)
 Ordinary telephone
wire
 Cheapest
 Easiest to install
 Suffers from external
EM interference

16. Shielded Twisted Pair (STP)
 Metal braid or
sheathing that reduces
interference
 More expensive
 Harder to handle
(thick, heavy)

17. Near End Crosstalk
 coupling of signal from one pair to another
 occurs when transmit signal entering the link couples
back to receiving pair
 ie. near transmitted signal is picked up by near
receiving pair

18. Categories of unshielded twisted-pair cables

19. UTP Categories

20. Guided Media – UTP
UTP Connector

21. Guided Media - UTP
 Applications:
 Telephone lines connecting subscribers to
the central office
 DSL lines
 LAN – 10Base-T and 100Base-T

22. Twisted Pair - Applications
 Most common medium
 Telephone network
 Within buildings
 For local area networks (LAN)

23. Twisted Pair - Pros and Cons
 Cheap
 Easy to work with
 Low data rate
 Short range

24. Guided Media – Coaxial Cable
Coaxial Cable

25. Coaxial Cable

26. Coaxial cable
 Inner conductor is a
solid wire outer
conductor serves both
as a shield
 against noise and a
second conductor

27. Coaxial Cable Applications
 Most versatile medium
 Television distribution
 Long distance telephone transmission
 Can carry 10,000 voice calls simultaneously
 Short distance computer systems links
 Local area networks

28. Coaxial Cable - Transmission
Characteristics
 superior frequency characteristics to TP
 performance limited by attenuation & noise
 analog signals
 amplifiers every few km
 closer if higher frequency
 up to 500MHz
 digital signals
 repeater every 1km
 closer for higher data rates

29. Guided Media – Coaxial Cable
Categories of coaxial cables

30. Guided Media – Coaxial Cable
BNC Connectors

31. BNC connectors
 BNC = Bayone-Neill-
Concelman
 BNC Connector is used to
connect the end of the
cable to a device
 BNC T is used in networks
to branch out a cable for
connection to a computer
or other device
 BNC Terminator is used at
the end of the cable to
prevent the reflection of
signal.

32. Coaxial cable performance

33. Guided Media – Coaxial Cable
 Applications:
 Analog telephone networks
 Cable TV networks
 Traditional Ethernet LAN – 10Base2,
10Base5

34. Guided Media – Fiber-Optic Cable
Fiber-optic cable transmit signals in the form of light.
Bending of light ray

35. Bending of light ray
 Angle of Incidence (I): the angle the ray makes
with the line perpendicular to the interface
between the two substances
 Critical Angle: the angle of incidence which
provides an angle of refraction of 90-degrees.

36. Guided Media – Fiber-Optic Cable
Optic Fiber

37. Optical fiber
 Uses reflection to
guide light through a
channel
 Core is of glass or
plastic surrounded by
Cladding
 Cladding is of less
dense glass or plastic

38. Optical Fiber

39. Optical Fiber - Benefits
 greater capacity
 data rates of hundreds of Gbps
 smaller size & weight
 lower attenuation
 electromagnetic isolation
 greater repeater spacing
 10s of km at least

40. Optical Fiber - Benefits
 The following characteristics distinguish optical fiber from twisted pair or coaxial cable:
 Greater capacity: The potential bandwidth, and hence data rate, of optical fiber is
immense; data rates of hundreds of Gbps over tens of kilometers have been
demonstrated. Compare this to the practical maximum of hundreds of Mbps over
about 1 km for coaxial cable and just a few Mbps over 1 km or up to 100 Mbps to 10
Gbps over a few tens of meters for twisted pair.
 Smaller size and lighter weight: Optical fibers are considerably thinner than coaxial
cable or bundled twisted-pair cable. For cramped conduits in buildings and
underground along public rights-of-way, the advantage of small size is considerable.
The corresponding reduction in weight reduces structural support requirements.
 Lower attenuation: Attenuation is significantly lower for optical fiber than for coaxial
cable or twisted pair, and is constant over a wide range.
 Electromagnetic isolation: Optical fiber systems are not affected by external
electromagnetic fields. Thus the system is not vulnerable to interference, impulse
noise, or crosstalk. By the same token, fibers do not radiate energy, so there is little
interference with other equipment and there is a high degree of security from
eavesdropping. In addition, fiber is inherently difficult to tap.
 Greater repeater spacing: Fewer repeaters mean lower cost and fewer sources of
error. The performance of optical fiber systems from this point of view has been
steadily improving. Repeater spacing in the tens of kilometers for optical fiber is
common, and repeater spacings of hundreds of kilometers have been demonstrated.

41. Optical Fiber - Transmission
Characteristics
 uses total internal reflection to transmit light
 effectively acts as wave guide for 1014 to 1015 Hz
 can use several different light sources
 Light Emitting Diode (LED)
 cheaper, wider operating temp range, lasts longer
 Injection Laser Diode (ILD)
 more efficient, has greater data rate
 relation of wavelength, type & data rate

42. Guided Media – Fiber-Optic Cable
Propagation Modes

43. Guided Media – Fiber-Optic Cable
Propagation Modes

44. Optical Fiber Transmission Modes

45. Guided Media – Fiber-Optic Cable
Fiber Construction

46. Guided Media – Fiber-Optic Cable
Fiber-optic Cable Connectors

47. Guided Media – Optical Fiber Cable
 Applications:
 Backbone networks – SONET
 Cable TV – backbone
 LAN
 100Base-FX network (Fast Ethernet)
 100Base-X

48. Transmission Characteristics of
Guided Media
Frequency Typical Typical Repeater
Range Attenuation Delay Spacing
Twisted pair 0 to 3.5 kHz 0.2 dB/km @ 50 µs/km 2 km
(with loading) 1 kHz
Twisted pairs 0 to 1 MHz 0.7 dB/km @ 5 µs/km 2 km
(multi-pair 1 kHz
cables)
Coaxial cable 0 to 500 MHz 7 dB/km @ 10 4 µs/km 1 to 9 km
MHz
Optical fiber 186 to 370 0.2 to 0.5 5 µs/km 40 km
THz dB/km

49. Comparison of Physical Media

50. Electromagnetic Spectrum

51. Wireless Transmission Frequencies
 2GHz to 40GHz
 microwave
 highly directional
 point to point
 satellite
 30MHz to 1GHz
 omnidirectional
 broadcast radio
 3 x 1011 to 2 x 1014
 infrared
 local

52. Unguided Media
Propagation Methods

53. Bands

54. Unguided Media
Wireless transmission waves

55. Broadcast Radio
 radio is 3kHz to 300GHz
 use broadcast radio, 30MHz - 1GHz, for:
 FM radio
 UHF and VHF television
 is omnidirectional
 still need line of sight
 suffers from multipath interference
 reflections from land, water, other objects

56. Unguided Media – Radio Waves
Omnidirectional Antenna
 Frequencies between 3 KHz and
1 GHz.
 are used for multicasts
communications, such as radio and
television, and paging system.

57. Terrestrial Microwave
 used for long haul telecommunications
 and short point-to-point links
 requires fewer repeaters but line of sight
 use a parabolic dish to focus a narrow beam onto a
receiver antenna
 1-40GHz frequencies
 higher frequencies give higher data rates
 main source of loss is attenuation
 distance, rainfall
 also interference

58. Unguided Media – Microwaves
 Frequencies between 1 and 300 GHz.
 Used for unicast communication such as cellular phones, satellite
networks and wireless LANs.
Unidirectional Antenna

59. Satellite Microwave
 satellite is relay station
 typically requires geo-stationary orbit
 height of 35,784km
 spaced at least 3-4° apart
 typical uses
 television
 long distance telephone
 private business networks
 global positioning

60. Unguided Media – Infrared
 Frequencies between 300 GHz to 400 THz.
 Can not penetrate walls.
Used for short-range communication in a
closed area using line-of-sight propagation.

61. Infrared
 modulate noncoherent infrared light
 end line of sight (or reflection)
 are blocked by walls
 no licenses required
 typical uses
 TV remote control
 IRD port

62. Antennas
 electrical conductor used to radiate or collect
electromagnetic energy
 transmission antenna
 radio frequency energy from transmitter
 converted to electromagnetic energy byy antenna
 radiated into surrounding environment
 reception antenna
 electromagnetic energy impinging on antenna
 converted to radio frequency electrical energy
 fed to receiver
 same antenna is often used for both purposes

63. Radiation Pattern
 power radiated in all directions
 not same performance in all directions
 as seen in a radiation pattern diagram
 an isotropic antenna is a (theoretical) point in space
 radiates in all directions equally
 with a spherical radiation pattern

64. Antenna Gain
 measure of directionality of antenna
 power output in particular direction verses that
produced by an isotropic antenna
 measured in decibels (dB)
 results in loss in power in another direction
 effective area relates to size and shape
 related to gain

65. Satellite Point to Point Link

66. Satellite Broadcast Link

67. Wireless Propagation
Ground Wave

68. Wireless Propagation
Sky Wave

69. Wireless Propagation
Line of Sight

70. Line of Sight Transmission
 Free space loss
 loss of signal with distance
 Atmospheric Absorption
 from water vapour and oxygen absorption
 Multipath
 multiple interfering signals from reflections
 Refraction
 bending signal away from receiver

71. Multipath Interference

72. Comparison of Media
 Medium Cost Speed Atten Interfere Security
 UTP Low 1-100M High High Low
 STP Medium 1-150M High Medium Low
 Coax Medium 1M–1G Medium Medium Low
 Fibre High 10M–2G Low Low High
 Radio Medium 1-10M Varies High Low
 Microw High 1M–10G Varies High Medium
 Satellite High 1 M–10G Varies High Medium
 Cellular High 9.6–19.2K Low Medium Low