# millimeter wave (mmWave)

Frequencies with wavelengths greater than 1 mm and less than 1 cm are called millimeter waves, mmWave. Those larger than 1 cm are called centimeter waves, cmWave.

The frequency spectrum for millimeter waves is between 30 GHz and 300 GHz, and that for centimeter waves is between 3 GHz and 30 GHz. Above 300 GHz, the range of sub-millimeter waves begins, which are wavelengths smaller than one millimeter. Both wavelengths, the centimeter and the millimeter waves, belong to the microwaves.

Millimeter waves are ideal for transmitting extremely high data rates in the multi- gigabit range. Limitations include high free- space attenuation, which restricts propagation and allows applications only over short distances. These problems can be compensated for by beamforming. For example, the free-space attenuation at 30 GHz at a distance of 10 m is already 82 dB.