In
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
s, maximum-ratio combining (MRC) is a method of
diversity combining in which:
#the signals from each
channel are added together,
#the
gain of each channel is made
proportional to the rms
signal level and inversely proportional to the mean square
noise level in that channel.
#different proportionality constants are used for each channel.
It is also known as ratio-squared combining and predetection combining. Maximum-ratio combining is the optimum combiner for independent
additive white Gaussian noise channels.
MRC can restore a signal to its original shape. The technique was invented by American engineer
Leonard R. Kahn in 1954.
MRC has also been found in the field of neuroscience, where it has been shown that neurons in the retina scale their dependence on two sources of input in proportion to the signal-to-noise ratio of the inputs.
Example: Least Squares estimate in the case of Rx diversity
We consider an example of which the receiver is endowed with N antennas. In this case, the received vector
is
where
is noise vector
. Following the ML detection criterion the detection procedure may be written as
where
is the considered constellation of
and
is the least square solution to the above model.
The least square solution in this case is also known as maximum-ratio-combining (MRC). In the case of N antennas the LS can be written as
which means that the signal from each antenna is rotated and weighted according to the phase and strength of the channel, such that the signals from all antennas are combined to yield the maximum ratio between signal and noise terms.
References
*
External links
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Telecommunications techniques
Radio resource management
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