Frequencies with wavelengths
greater than 1 mm and less than 1 cm are called millimeter waves, mmWave. Those greater than 1 cm are called centimeter waves, cmWave.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, i.e. wavelengths smaller than one millimeter. Both wavelengths, the centimeter and the millimeter waves belong to themicrowaves
. Millimeter waves are ideally suited for the transmission of 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 by beamforming. For example, the free-space attenuation at 30 GHz at a distance of 10 m is already 82 dB.