The following questions are salient when assessing the quality of a DVB (digital video broadcasting) system: How high is the available margin of a DVB transmission? Up to what C/N ratio can a settop box still demodulate and decode DVB signals? The answers are obtained through deliberate deterioration of the C/N ratio by superimposing white noise on the DVB signal. Appropriate conversion produces the bit error ratio (BER) as a function of the C/N ratio for QPSK modulation and all QAM modes.
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