- Carrier-to-noise ratio
In

telecommunications , the**carrier-to-noise ratio**, often written CNR or "C/N", is thesignal-to-noise ratio (SNR) of a modulated signal. The CNR is the quotient between the average received modulated carrier power "C" and the average receivednoise power "N" after the receiver filters. The aim of the term is to distinguish the CNR of the radio frequencypassband signal from the SNR of an analoguebase band message signal afterdemodulation , for example an audio frequency analogue message signal. If this distinction is not necessary, the term SNR is often used instead of CNR, with the same definition.High "C/N" ratios provide good quality of reception, for example low

bit error rate (BER) of a digital message signal, or high SNR of an analogue message signal."C" and "N" may be measured in watts or in volts squared.

:$CNR\; =\; frac\; \{C\}\{N\}\; =\; left\; (\; frac\; \{V\_mathrm\{carrier\_\{RMS\}\; \{V\_mathrm\{noise\_\{RMS\}\; ight\; )\; ^2$,

where $V\_mathrm\{carrier\_\{RMS$ and $V\_mathrm\{noise\_\{RMS$ are the

root mean square voltage levels in volts of the carrier signal and noise respectively. Engineers often specify the "C"/"N" ratio in decibels (dB) between the power in the carrier of the desired signal and the total received noise power, according to the following::$mathrm\{CNR\; (dB)\}\; =\; 10\; log\_\{10\}\; frac\; \{C\}\{N\}\; =20\; log\_\{10\}\; frac\; \{V\_mathrm\{carrier\_\{RMS\}\; \{V\_mathrm\{noise\_\{RMS\}$

The "C/N" ratio is measured in a manner similar to the way the

signal-to-noise ratio ("S"/"N") is measured, and both specifications give an indication of the quality of a communications channel.In the famous

Shannon–Hartley theorem , the "C/N" ratio is equivalently to the "S"/"N" ratio.The "C/N" ratio resembles the

carrier-to-interference ratio ("C/I",**CIR**), and thecarrier-to-noise-and-interference ratio , "C/(N+I)" or**CNIR**.**See also***

Signal-to-noise ratio (SNR or "S"/"N")

*Carrier-to-interference ratio (CIR or "C"/"I")

*Audio system measurements

*Video quality

*Subjective video quality

*Near-far problem

*Peak signal-to-noise ratio

*SINAD (ratio of signal-plus-noise-plus-distortion to noise-plus-distortion)

*Eb/N0 (energy per bit relative to noise power spectral density)

*Es/N0 (energy per symbol relative to noise power spectral density)

*Carrier-to-receiver noise density "C/"N"_{0}**References****External links**

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