NON-COHERENT SEQUENCE ESTIMATION RECEIVER FOR DIGITAL MODULATIONS

摘要

It is described a non-coherent receiver for digital modulated radio signals, linear or not, possibly affected by channel coding. In the case of M-PSK, or M-QAM modulations, possibly combined with a channel coding, the signal received is demodulated and filtered by a filter matched to the pulse transmitted. In the case of linear modulations in presence of ISI, and of non-linear M-CPM modulations, the reception filter is a matched and whitened one. The signal is filtered and sampled and the samples are accumulated in a relevant phase reconstruction memory containing N - 1 samples preceding the actual one. Samples are processed making use of a Viterbi processor estimating the sequence of symbols transmitted according to maximum likelihood. The first embodiment calculates the branch metrics using an estimation of the carrier phase in PSP mode (Per-Survivor-Processing). This improves the performance of the receiver. In the second embodiment, the trellis branch metrics are obtained from the expression for the maximum likelihood sequence estimation. The Viterbi algorithm can be applied in this case.