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Discussion Forums : General TV and broadcasting : What is SNR and what is BER, and how are they related?

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By: dudek
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Regular Topic Posted: Aug 04, 2008 - 22:59

Signal to noise ratio (SNR) is a measure of the strength of signal of interest divided by the strength of any noise (interference) being received. There are quite a few ways of defining signal to noise, but in general a high signal-to-noise ratio is good because it means you are getting more signal and you are getting less noise. SNR is usually measured on a logarithmic scale, meaning the SNR value is the logarithm of the actual ratio.

BER stands for the Bit Error Rate and it is a measure of how many incorrect bits are being received as part of a streaming video signal. These errors can be measured in various places during the signal processing chain (see page 105 in the book). Generally a higher BER is bad, because it means more errors are being detected. WHen the noise level is high, it can lead to errors unless the are detected and fixed by error-correcting processes. The precise BER number is not very meaningful when comparing different receivers because it can be measured in at least 4 different ways (before or after error correction, for example).

Generally, high noise (low SNR) leads to higher BER. Moderate SNR can be corrected by smart devices. High BER is bad, and usually leads to observable problems with the signal you are watching.

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