V.G. Kartashevsky, S.V. Shatilov
In this paper have considered the problem of receiving the discrete messages in the channel with memory when a finite impulse response is unknown. It proposed, that symbols have transmit by packets with rate about 100 symbols, channel signals be formed as PM-4 and sampling period has defined.
Estimation of unknown impulse response realize by means of algorithm of blind identification based on maximum likelihood method. Because of small rate of the packet the blind identification algorithm should possess quick convergence solutions to true impulse response. So, this algorithm demands of creation of diversity reception techniques.
Demodulation problem has decided by special algorithm: so-called “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.
Also, method of calculating of scalar factor for estimation of impulse response proposed.
Considered algorithms modeled for PM-4 signals and packets with rate about 100 symbols. Time interval of impulse response was equal 4 sampling period.
Simulation showed that relative error of blind identification method equals 20% for signal-noise ratio of 100. In this situation is possible for the given algorithm of demodulation the probability of error will tend to 0.
So, considered method of processing of PM-4 signals is competitive and wins in the rate of convergence compared to entry for other methods.