What are the various
transmission media available? State advantage and disadvantages of each
Ans
Types
of Transmission Media
Transmission
media is broadly classified into two groups.
1.
Wired or Guided Media or Bound Transmission Media
2.
Wireless or Unguided Media or Unbound Transmission Media
Wired
or Guided Media or Bound Transmission Media:
Bound transmission media are the cables that are tangible or have physical
existence and are limited by the physical geography. Popular bound transmission
media in use are
twisted
pair cable, co-axial cable and fiber optical cable. Each of them has its own
characteristics like transmission speed, effect of noise, physical appearance,
cost etc.
Wireless
or Unguided Media or Unbound Transmission Media: Unbound transmission media are the ways of
transmitting data without using any cables. These media are not bounded by
physical geography. This type of transmission is called Wirelesscommunication. Nowadays
wireless communication is becoming popular. Wireless LANs are being installed
in office and college campuses. This transmission usesMicrowave, Radio wave,
Infra red are some of popular unbound transmission media.
COAXIAL
CABLE:
Coaxial
cable is very common & widely used commutation media. For example TV wire
is usually coaxial.
Coaxial
cable gets its name because it contains two conductors that are parallel to
each other. The center conductor in the cable is usually copper. The copper can
be either a solid wire or stranded martial.
Outside
this central Conductor is a non-conductive material. It is usually white,
plastic material used to separate the inner Conductor form the outer Conductor.
The other Conductor is a fine mesh made from Copper. It is used to help shield
the cable form EMI.
Outside
the copper mesh is the final protective cover. (as shown in Fig)
The
actual data travels through the center conductor in the cable. EMI interference
is caught by outer copper mesh. There are different types of coaxial cable vary
by gauge & impedance.
ADVANTAGES
COAXIAL CABLE
·
Inexpensive
·
Easy to wire
·
Easy to expand
·
Moderate level of
EMI immunity
DISADVANTAGE
COAXIAL CABLE
·
Single cable
failure can take down an entire network
The
most popular network cabling is Twisted pair. It is light weight, easy to
install, inexpensive and support many different types of network. It also
supports the speed of 100 mps. Twisted pair cabling is made of
pairs of solid or stranded copper twisted along each other. The twists are done
to reduce vulnerably to EMI and cross talk. The number of pairs in the cable
depends on the type. The copper core is usually 22-AWG or 24-AWG, as measured
on the American wire gauge standard. There are two types of
twisted pairs cabling
1.
Unshielded twisted pair (UTP)
2.
Shielded twisted pair (STP)
Advantages
·
Shielded
·
Faster than UTP
and coaxial
Disadvantages
·
More expensive
than UTP and coaxial
·
More difficult
installation
·
High attenuation
rate
Fiber
Optics
Fiber
optic cable uses electrical signals to transmit data. It uses light. In fiber
optic cable light only moves in one direction for two way communication to take
place a second connection must be made between the two devices. It is actually
two stands of cable. Each stand is responsible for one direction of
communication. A laser at one device sends pulse of light through this cable to
other device. These pulses translated into “1’s” and “0’s” at the
other end.
In the
center of fiber cable is a glass stand or core. The light from the laser moves
through this glass to the other device around the internal core is a reflective
material known as CLADDING. No light escapes the glass core because
of this reflective cladding.
Advantages
Of Fiber Optic Cable:
·
Fast
·
Low attenuation
·
No EMI
interference
Disadvantages
Fiber Optics:
·
Very costly
·
Hard to install
The data transmission
capabilities of various Medias vary differently depending upon the various
factors. These factors are:
1. Bandwidth.
It refers to the data carrying capacity of a channel or medium. Higher
bandwidth communication channels support higher data rates.
2. Radiation.
It refers to the leakage of signal from the medium due to undesirable
electrical characteristics of the medium.
3. Noise Absorption.
It refers to the susceptibility of the media to external electrical noise that
can cause distortion of data signal.
4. Attenuation.
It refers to loss of energy as signal propagates outwards. The amount of energy
lost depends on frequency. Radiations and physical characteristics of media
contribute to attenuation
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