Water filling algorithm is a general name given to the ideas in
communication systems
A communications system or communication system is a collection of individual telecommunications networks, transmission systems, relay stations, tributary stations, and terminal equipment usually capable of interconnection and interopera ...
design and practice for
equalization strategies on
communications channels. As the name suggests, just as water finds its level even when filled in one part of a vessel with multiple openings, as a consequence of
Pascal's law
Pascal's law (also Pascal's principle or the principle of transmission of fluid-pressure) is a principle in fluid mechanics given by Blaise Pascal that states that a pressure change at any point in a confined incompressible fluid is transmitted ...
, the amplifier systems in communications network repeaters, or receivers amplify each channel up to the required power level compensating for the channel impairments. See, for example, channel power allocation in
MIMO
In radio, multiple-input and multiple-output, or MIMO (), is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of w ...
systems.
Single channel systems
In a single channel communication system the deamplification and loss present on them can be simplistically taken as attenuation by a percentage ''g'', then amplifiers restore the signal power level to the same value at transmission setup by operating at a gain of 1/ (1 − ''g''). E.g. if we experience 6 dB attenuation in transmission, i.e. 75% loss, then we have to amplify the signal by a factor of 4''x'' to restore the signal to the transmitter levels.
Multichannel systems
Same ideas can be carried out in presence impairments and a multiple channel system. Amplifier nonlinearity, crosstalk and power budgets prevent the use of these waterfilling algorithms to restore all channels, and only a subset can benefit from them.
See also
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Water-pouring algorithm
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Zero-forcing equalizer The zero-forcing equalizer is a form of linear equalization algorithm used in communication systems which applies the inverse of the frequency response of the channel. This form of equalizer was first proposed by Robert Lucky.
The zero-forcing eq ...
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Robert Lucky
Robert Wendell Lucky (January 9, 1936 – March 10, 2022) was an electrical engineer, inventor, and research manager at Bell Labs and Bell Communications Research (Bellcore). He is best known for his writings and speeches about technology, socie ...
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Amplifier system
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EDFA
An optical amplifier is a device that amplifies an optical signal directly, without the need to first convert it to an electrical signal. An optical amplifier may be thought of as a laser without an optical cavity, or one in which feedback from ...
References
* Proakis, Digital Communication Systems, 4th Ed., McGraw Hill, (2001).
Telecommunication theory
Error detection and correction
Information theory
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