Patent ID: 6389079
Filing Date: 2002-05-14
Classification: H04B,H04L

Abstract:
A 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 use of the Viterbi algorithm applied to a trellis whose branches represent possible transitions among states defined by possible subsequences of information symbols, having finite length, through which algorithm at each symbol interval, paths are selected on the trellis such that a cumulative path metric of transition metrics is maximum, said path metric being indicative of the likelihood degree existing among symbols of a path associated with the same path metric and a sequence of transmitted symbols, wherein each said transition metric (&lgr;n(s)) is calculated through the following steps:a) non-coherent base band conversion of a received signal, filtering of the converted signal (r(t)) through a filter (FRIC) matched to a transmitted pulse and sampling at symbol frequency of the filtered signal, to obtain a sequence of complex samples ({xn}); b) construction of a phase reference by accumulating N-1 products among said sequential complex samples (xnâˆ’1, . . . , xnâˆ’N+1), conjugated, and corresponding code symbols ({tilde over (c)}nâˆ’1, . . . , {tilde over (c)}nâˆ’N+1), also complex, univocally associated with a relevant 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; c) normalization of the value of said phase reference, through division by its modulus; d) replacement of a phase reference, or phasor (eâˆ’j&thgr;) of said modulated carrier, present in a known analytical expression of transition metrics used by a coherent receiver with the normalized phase reference resulting from said step c), obtaining an analytical expression for the calculation of each of said transition metrics (&lgr;n(s)).