Mechanism for estimating es/no from pseudo error measurements

Abstract

In a digital data recovery receiver, an optimal (in the Maximum likelihood sense) estimate of Es/No (dB) is obtained by the following mechanism. First, over a prescribed symbol span of N symbols, for each of 2.sup.B-1 -1 quantization bins, respectively associated with 2.sup.B-1 threshold levels used by a B-bit resolution analog-to-digital converter to digitize a received signal, the number of times that the received signal is quantized with respect to that level is counted. Each count total is divided by the number N of symbols in the span, to obtain plural ratios, respectively representative of probalities of symbol pseudo error rate over the symbol span. Using these ratios, respective Es/No (dB) values are derived from stored pseudo error relationships, each of which is associated with a respective one of the 2.sup.B-1 -1 quantization bins and defines the probability of symbol error rate in terms of Es/No (dB). Employing each derived Es/No (dB) value to a maximum likelihood estimate of Es/No (dB), a set of weights, respectively associated with respective Es/No (dB) values, is produced. Each weight is multiplied by its associated Es/No (dB) value and the products are summed, so as to obtain an output signal representative of an estimate of 10log.sub.10 of the ratio of received energy per symbol Es to noise power density spectra No. This output signal may then be used in a feedback loop to the transmitter site to control one or more characteristics of the transmitted signal, so as to attain a prescribed signal quality in the recovered signal.