Reference : Frequency Bands
Frequency describes how many wave cycles there are in a period
of 1 (one) second.
Frequency of a wave is inverse proportional with its Period.
Frequency is denoted in cycle per second or Hertz (Hz).
f = 1/T where f is frequency in Hertz and T
is period in second. 
Figure: Wave. The time it takes for the wave to travel from point "a" to point "b" is called a Period (T).
Frequency discussion has always been an integral part of any telecommunication subject be it
wired or wireless because telecommunication is about
sending and receiving electromagnetic (EM) waves.
Another parameter of an EM wave is wavelength. The relation
between frequency and wavelength of an EM wave is illustrated in
this equation:
c = λf where c is the speed of light
(= 3x10^{8} m/s),
λ is wavelength in meter, f is frequency in Hertz. 
Frequency band designation is given by standard bodies
and the telecom industry based on characteristic of each frequency range. The following tables
list frequency bands that are publicly known and often
mentioned in telecommunication literature.
