In the famous Shannon–Hartley theorem, the C/N ratio is equivalent to the S/N ratio. 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. The carrier-to-noise ratio is defined as the ratio of the received modulated carrier signal power C to the received noise power N after the receiver filters:Ĭ N R = C N Measurements and estimation 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 analog message signal. Therefore, the term carrier-to-noise-ratio (CNR), instead of signal-to-noise-ratio (SNR), is preferred to express the signal quality when the signal has been digitally modulated. It is for this reason that, in the context of digital modulations, digitally modulated signals are usually referred to as carriers. In fact, the information (bits or symbols) is carried by given combinations of phase and/or amplitude of the I and Q components. QAM or PSK) are basically made of two CW carriers (the I and Q components, which are out-of-phase carriers). If this distinction is not necessary, the term SNR is often used instead of CNR, with the same definition.ĭigitally modulated signals (e.g. The term is used to distinguish the CNR of the radio frequency passband signal from the SNR of an analog base band message signal after demodulation, for example an audio frequency analog message signal. In telecommunications, the carrier-to-noise ratio, often written CNR or C/N, is the signal-to-noise ratio (SNR) of a modulated signal. JSTOR ( July 2016) ( Learn how and when to remove this template message).Unsourced material may be challenged and removed.įind sources: 'Carrier-to-noise ratio' – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.

C# convert unix timestamp to datetime