The signal-to-interference ratio (SIR or ''S/I''), also known as the carrier-to-interference ratio (CIR or ''C/I''), is the quotient between the average received modulated carrier power ''S'' or ''C'' and the average received
co-channel interference power ''I'', i.e.
crosstalk, from other transmitters than the useful signal.
The CIR resembles the
carrier-to-noise ratio (CNR or ''C/N''), which is the
signal-to-noise ratio (SNR or ''S/N'') of a modulated signal before demodulation. A distinction is that interfering radio transmitters contributing to ''I'' may be controlled by
radio resource management Radio resource management (RRM) is the system level management of co-channel interference, radio resources, and other radio transmission characteristics in wireless communication systems, for example cellular networks, wireless local area networks, ...
, while ''N'' involves noise power from other sources, typically
additive white gaussian noise (AWGN).
Carrier-to-noise-and-interference ratio (CNIR)
The CIR ratio is studied in interference limited systems, i.e. where ''I'' dominates over ''N'', typically in cellular radio systems and broadcasting systems where frequency channels are reused in view to achieve high level of area coverage. The ''C/N'' is studied in noise limited systems. If both situations can occur, the carrier-to-noise-and-interference ratio (CNIR or ''C/(N+I)'') may be studied.
See also
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Carrier-to-noise ratio (CNR or ''C''/''N'')
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Carrier-to-receiver noise density
In telecommunications, the carrier-to-noise ratio, often written CNR or ''C/N'', is the signal-to-noise ratio (SNR) of a modulated signal. The term is used to distinguish the CNR of the radio frequency passband signal from the SNR of an analog b ...
''C/''N''
0
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Co-channel interference (CCI)
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Crosstalk
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Signal-to-noise ratio (SNR or ''S''/''N'')
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SINAD
Signal-to-noise and distortion ratio (SINAD) is a measure of the quality of a signal from a communications device, often defined as
:
\mathrm = \frac,
where P is the average power of the signal, noise and distortion components. SINAD is usually ex ...
(ratio of signal-plus-noise-plus-distortion to noise-plus-distortion)
Engineering ratios
Radio frequency propagation
Radio resource management
Interference
Television terminology
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