Mitigation
Fading can cause poor performance in a communication system because it can result in a loss of signal power without reducing the power of the noise. This signal loss can be over some or all of the signal bandwidth. Fading can also be a problem as it changes over time: communication systems are often designed to adapt to such impairments, but the fading can change faster than the adaptations can be made. In such cases, the probability of experiencing a fade (and associated bit errors as the signal-to-noise ratio drops) on the channel becomes the limiting factor in the link's performance.
The effects of fading can be combated by using diversity to transmit the signal over multiple channels that experience independent fading and coherently combining them at the receiver. The probability of experiencing a fade in this composite channel is then proportional to the probability that all the component channels simultaneously experience a fade, a much more unlikely event.
Diversity can be achieved in time, frequency, or space. Common techniques used to overcome signal fading include:
- Diversity reception and transmission
- MIMO
- OFDM
- Rake receivers
- Space–time codes
Read more about this topic: Fading
Famous quotes containing the word mitigation:
“Law is a thing which is insensible, and inexorable, more beneficial and more profitious to the weak than to the strong; it admits of no mitigation nor pardon, once you have overstepped its limits.”
—Titus Livius (Livy)