Transmission Medium

Guided Media
Unguided Media

1. TRANSMISSION MEDIUM
Session 3

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. Classes of transmission media

5. FACTORS TO BE CONSIDERED WHILE
CHOOSING TRANSMISSION MEDIUM
Transmission Rate
Cost and Ease of Installation
Resistance to Environmental Conditions
Distances

6. GUIDED MEDIAGUIDED 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. TWISTED PAIR CABLE
This cable is the most commonly used and is
cheaper than others. It is lightweight, cheap, can
be installed easily, and they support many
different types of network
Twisted Pair is of two types :
Unshielded Twisted Pair (UTP)
Shielded Twisted Pair (STP)

10. UNSHIELDED VERSUS SHIELDED TWISTED-
PAIR CABLE
UTP and STP cables

11. UNSHIELDED TWISTED PAIR (UTP)
Adv:
•Ordinary telephone wire
•Cheapest
•Easiest to install
•It has high speed capacity
•100 meter limit
Dis adv:
•Bandwidth is low when compared
with Coaxial Cable
•Provides less protection from
interference.

13. SHIELDED TWISTED PAIR (STP)
Adv:
•Metal braid or sheathing that
reduces interference
•Easy to install
•Eliminates crosstalk
•Higher capacity than
unshielded twisted pair
•Increases the signaling rate
Disadv:
•More expensive
•Harder to handle
(thick, heavy)
•Difficult to manufacture

14. GUIDED MEDIA - UTP
Applications:
Telephone lines connecting subscribers to the
central office
DSL lines
LAN – 10Base-T and 100Base-T

15. TWISTED PAIR - APPLICATIONS
Most common medium
Telephone network
Within buildings
For local area networks (LAN)

16. TWISTED PAIR - PROS AND CONS
Cheap
Easy to work with
Low data rate
Short range

17. GUIDED MEDIA – COAXIAL
CABLE
Coaxial Cable

19. COAXIAL CABLE

20. COAXIAL CABLE
Inner conductor is a
solid wire outer
conductor serves both
as a shield
against noise and a
second conductor

21. TYPES OF COAXIAL CABLES 
Baseband : Which is used for digital transmission. It is
mostly used for LAN’s. Baseband transmits a single
signal at a time with very high speed.
Broadband : This uses analog transmission on standard
cable television cabling. It transmits several
simultaneous signal using different frequencies.

22. COAXIAL CABLE PROS
Bandwidth is high
Used in long distance telephone lines.
Television distribution
Can carry 10,000 voice calls simultaneously
Short distance computer systems links
Local area networks
Data transmission without distortion.

23. CONS
Single cable failure can fail the entire network.
Difficult to install and expensive when compared
with twisted pair.

24. GUIDED MEDIA – COAXIAL
CABLE
Applications:
Analog telephone networks
Cable TV networks
Traditional Ethernet LAN – 10Base2, 10Base5

25. FIBER OPTICS
•Higher bandwidth
•Less expensive
•Immune to electrical noise
•More secure – easy to notice an attempt to
intercept signal
•Physical characterizes
–Glass or plastic fibers
–Very thin (thinner than human hair)
–Material is light

27. OPTICAL FIBER - PROS
•greater capacity
–data rates of hundreds of Gbps
•smaller size & weight
•lower attenuation(Reduction in signal)
•Used for both analog and digital signals.

28. CONS
It is expensive.
Difficult to install.
Maintenance is expensive and difficult

29. GUIDED MEDIA – OPTICAL FIBER
CABLE
Applications:
Backbone networks – SONET
Cable TV – backbone
LAN
100Base-FX network (Fast Ethernet)
100Base-X

30. UNGUIDED MEDIA
Wireless transmission waves

31. BROADCAST RADIO
Its frequency is between 10 kHz to 1GHz.
 It is simple to install and has high attenuation.
FM radio
UHF and VHF television
still need line of sight
suffers from multipath interference
reflections from land, water, other objects

32. 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.

33. INFRARED
are blocked by walls
no licenses required
typical uses
TV remote control
IRD port

34. MICROWAVE TRANSMISSION
Line-of-site
High speed
Cost effective
Easy to implement
Weather can cause interference

35. STRAIGHT THROUGH AND
CROSSOVER WIRING
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Wiring within a twisted pair cable is configured as
either
Straight through, where each wire (or pin) is attached to the
same contact point at each end
Crossover, where transmit contacts on each end of the cable
are connected to the receive contact at the other end

36. STRAIGHT THROUGH WIRING
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37. CROSSOVER WIRING
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38. UTP STRAIGHT-THROUGH CABLE
The cable that connects from the switch port to the
computer NIC port is called a straight-through cable.
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Host or RouterHub or Switch

39. UTP STRAIGHT-THROUGH CABLE
Host or RouterHub or Switch

40. UTP CROSS-OVER CABLE
The cable that connects from one switch port to another
switch port is called a crossover cable.
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41. UTP CROSS-OVER CABLE
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42. UTP ROLLOVER CABLE
The cable that connects the RJ-45 adapter on the com
port of the computer to the console port of the router or
switch is called a rollover cable.
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