Transmission
impairments:
The signal at the beginning of the medium is not the same as the signal at the
end of the medium. The type of obstacles that can occur in a signal is called
transmission impairments.
The
most significant impairments are:
(i) Attenuation
(ii) Delay distortion
(iii) Noise
(i)
Attenuation: Attenuation
means a loss of energy. The amplitude of strength of a signal is gradually decreased
during the transmission. This problem is called attenuation. Attenuation
decides the signal to noise ratio hence the quality of received signal.
(ii)
Delay distortion: Distortion
means that the signal changes its form or shape. The velocity of propagation of
a signal through a medium varies with frequency is called delay distortion.
(iii)
Noise: For
any data transmission event many unwanted signals that are inserted somewhere
between transmission and reception. These undesirable signals are reoffered to
as noise.
Noise
is a major limiting factor in communication system performance.
Noise
can be categorized into four types as follows:
(a) Thermal noise
(b) Intermediation noise
(c) Crosstalk
(d) Impulse noise
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