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Probability of symbol error for demodulation qpsk-signals in channel with memory


V.G. Kartashevsky

In this paper have considered the problem of estimating the probability of symbol error for QPSK-signalsat a reception in the channel with memory by the algorithm "technique as a whole with elementwise decision", or, other words “processing as whole on a time interval of impulse response with adoption of decision only for first symbol of consider time interval” (this algorithm is based on using of decision feedback and estimation of impulse response).Considered the case of two-beam channel with constant parameters and with correlated Rayleigh fading rays. Properties of the channel with memory described by the coefficients of input impulse response of the channel. Analysis of the error probability based on the use of the additive upper bound for error probability (the inequality Boole) averaged over dependent hypotheses concerning symbols following the analyzed. For a channel with constant parameters, when the memory channel extends only to the two adjacent symbol, using the entered coefficients of the form of the impulse response, shows that the noise immunity of QPSK-signal reception against the background of an additive "white" Gaussian noise on the algorithm used is not significantly different from the noise immunity of the optimum receiver Kotelnikov. The probability of error Energy loss is taking 1dB for the probability of error equally . The article also examined a model two-beam fading communication channel. Immunity analysis shows that in the low signal / noise ratio immunity of the algorithm above the reception in case of correlated fading rays. At high signal / noise ratio – the situation is reversed. However, unlike the error probability is not great (for a signal / noise ratio of 100 the error probability are 0,0002 and 0,00036 respectively).
