Unguided media
An unguided media does not make use of
wired channel, in-fact it uses wireless channel for transmission. These include
radio waves, microwaves, infrared waves etc.
Radio waves
Frequencies in the range 3 kHz and 1
GHz are considered as radio waves. Radio waves are omnidirectional. By
omnidirectional we mean receiving or sending signals in all directions. These
can penetrate walls. Radio waves are used for multicasting e.g. in AM and FM
radio, television etc.
Microwaves
Frequencies in the range 1 GHz and 300
GHz are considered as microwaves. These are unidirectional and thus are used
for unicast communication. These make use of unidirectional antennas.
Microwaves are used for satellite communication, in wireless LANs etc.
Infra-red waves
Frequencies in the range 300 GHz and
400 THz are considered as infrared waves. These cannot penetrate walls. Thus
they are used in television sets at our homes. These cannot be used in sunlight
outside of a room since sunlight consists of infrared waves.
