4.1 | Background for Studying Frequency-Based Cable Testing | |||
4.1.7 | Noise in time and frequency |
Noise is an important concept in
communications systems, including LANS.
While
noise usually refers to undesirable sounds, noise related to
communications refers to undesirable signals. Noise can
originate from natural and technological sources, and is added to the
data signals in communications systems.
All communications systems have some amount of noise. Even though noise cannot be eliminated, its effects can be minimized if the sources of the noise are understood. There are many possible sources of noise:
Noise that affects all transmission frequencies equally is called white noise. Noise that only affects small ranges of frequencies is called narrowband interference. When detected on a radio receiver, white noise would interfere with all radio stations. Narrowband interference would affect only a few stations whose frequencies are close together. When detected on a LAN, white noise would affect all data transmissions, but narrowband interference might disrupt only certain signals. If the band of frequencies affected by the narrowband interference included all frequencies transmitted on the LAN, then the performance of the entire LAN would be compromised.
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