Maximal-ratio combining

In telecommunications, maximum-ratio combining (MRC) is a method of diversity combining in which:

  1. the signals from each channel are added together,
  2. 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.
  3. 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[1] 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.[2]

This has the advantage of producing an output with acceptable SNR even when none of the individual signals are themselves acceptable.

  1. ^ Kahn, Leonard (November 1954). "Ratio Squarer". Proc. IRE (Corresp.). 42 (11): 1704. doi:10.1109/JRPROC.1954.274666.
  2. ^ Homann, Jan; Freed, Michael A. (2016-12-30). "A mammalian retinal ganglion cell implements a neuronal computation that maximizes the SNR of its postsynaptic currents". Journal of Neuroscience. 37 (6): 2814–16. doi:10.1523/JNEUROSCI.2814-16.2016. ISSN 0270-6474. PMC 5299566. PMID 28039376.