Randomly varying channel gains such as fading are taken into account by adding some margin depending on the anticipated severity of its effects.
The amount of margin required can be reduced by the use of mitigating techniques such as antenna diversity or multiple-input and multiple-output (MIMO).
Additionally losses are incurred in most radio links, including atmospheric attenuation by gases, rain, fog and clouds.
These alternative forms can be derived by substituting wavelength with the ratio of propagation velocity (c, approximately 3×108 m/s) divided by frequency, and by inserting the proper conversion factors between km or miles and meters, and between MHz and (1/s).
[citation needed] Actual propagation losses may vary significantly depending on building construction and layout.
Guided media such as coaxial and twisted pair electrical cable, radio frequency waveguide and optical fiber have losses that are exponential with distance.
The Voyager program spacecraft have the highest known path loss (308 dB as of 2002[4]: 26 ) and lowest link budgets of any telecommunications circuit.