1. Non-coherent reception process of information symbol sequences, obtained by amplitude and/or phase digital modulation of a carrier, transmitted on a communication channel, affected by additive white gaussian noise, based on a particularly effective use of the Viterbi algorithm applied to a trellis sequential diagram, or trellis, whose branches represent all the possible transitions among states defined by all possible subsequences of information symbols, possibly encoded, having finite length, through which algorithm at each symbol interval, paths are selected on the trellis such that a cumulative path metric, or general metric or sequence metric, of transition metrics, or branch metrics, is maximum; said path metric being indicative of the likelihood degree existing among symbols of a path associated to the same path metric (&lcub;{tilde over (&agr;)} n &rcub;,&lcub;{tilde over (c)} n &rcub;) and a sequence of transmitted symbols (&lcub;&agr; n &rcub;,&lcub;c n &rcub;), characterized in that each said transition metric (&lgr; n (s) ) is calculated through the following steps: a) non-coherent conversion in base band of the signal received, subsequent filtering of the converted signal (r(t)) through a filter (FRIC) matched to the transmitted pulse and symbol frequency sampling of the filtered signal, obtaining a sequence of complex samples (&lcub;x n &rcub;); b) construction of a phase reference through accumulation of N−1 products among said complex sequential samples (x n−1,...,x n−N&plus;1 ), conjugated, and corresponding code symbols ({tilde over (c)} n−1,..., {tilde over (c)} n−N&plus;1 ), also complex, univocally associated to a relevant said branch of the trellis; the number N−1 being the finite length, selected in order to obtain the desired accuracy in the constructed phase, said accuracy increasing as N increases, at the expense of possible increase in the trellis complexity, expressed in terms of number of states; c) normalization of the value of said phase reference, through division by the module itself; d) replacement of a phase reference, or phasor (e −j&thgr; ) of said modulated carrier, present in the known analytical expression of transition metrics used by an optimal coherent receiver, which could replace said non coherent receiver (RIC) whenever said phasor would be known, with said phase reference resulting from said step c), obtaining an analytical expression for the calculation of each of said transition metric (&lgr; n (s) ) used by said non coherent receiver(RIC).