Non-coherent sequence estimation receiver for modulations

Non coherent reception process of information symbol sequences obtained through phase and/or amplitude 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 sequence trellis diagram, or trellis, whose branches represent all the possible transitions among states defined by all possible sub-sequences of information symbols, possibly encoded, of finite length, through which algorithm, at each symbol interval, paths are selected on the trellis such that a cumulative path metric, of transition metrics, or branch metrics, is maximum, said path metric being indicative of the likelihood degree existing among the symbols of the path associated to the same path metric ({{tilde over (α)}n},{{tilde over (c)}n}) and a sequence of transmitted symbols 84 i η ,

• characterized in that each said transition metric (λn(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 sampling at symbol frequency of the filtered signal, obtaining a sequence of complex samples ({xn});
• b) identification of a function to maximize equal to the known expression for maximum likelihood sequence estimation of a non-coherent receiver, as expression of a general metric associated to said complex sample sequence ({xn});
• c) expression of a partial metric, obtained considering said general metric up to a current n-thsample of said sequence of complex samples ({xn});
• d) expression of an incremental metric, of unlimited memory, obtained from the difference between the expression of said partial metric at a current signalling interval and at an immediately preceding interval;
• e) truncation of the length of said unlimited memory at N−1 samples of said sequence {xn} preceding the current sample, obtaining the analytical expression of a said branch metric (λn(s)) of said trellis diagram, built on the basis of all the possible symbol subsequences ({{tilde over (α)}n},{{tilde over (c)}n}) having length N;
• f) calculation of said general metric through recurrent updating of said sequence partial metric.

Non coherent receiver of sequences of coded symbols ({cn}) obtained by amplitude and/or phase digital modulation of a carrier, transmitted on a communication channel, affected by additive white gaussian noise, including:

• a non coherent converter in base band of the signal received, followed by a filter (FRIC) matched to the transmission pulse, followed in its turn by a sampler (CAMP) at symbol frequency, which obtains a sequence of complex samples {xn};
• a phase reconstruction memory (SHF1) in which N−1 samples (xn−1, . . . ,xn−N+1) of said sequence {xn} preceding a current sample (xn) are stored;
• calculation means (METRICTOT) of transition metrics (λn(s)), or branch metrics, of a trellis sequential diagram, or trellis, whose branches represent all possible transitions among states defined by all possible subsequences of information symbols ({cn}) of finite length;
• a Viterbi processor adapted to select paths on the trellis such that a cumulative path metric of transition metrics, or branch metrics, is maximum, said path metric indicating the likelihood level existing among symbols ({{tilde over (c)}k}) of a relevant path and a sequence of transmitted symbols ({cn}), characterized in that said calculation means (METRICTOT) of the transition metrics (λn(s)), are subdivided into a plurality of identical sub-means (METRIC(s)), each of them being adapted to calculate a relevant transition metric (λn(s)), including:
• a memory for N code symbols ({tilde over (c)}n−1, . . . ,{tilde over (c)}n−N+1) univocally associated to a relevant branch of the trellis;
• construction means of a phase reference controlled by said N−1 samples (xn−1, . . . ,xn−N+1) stored in said phase reconstruction memory (SHF1) and by N−1 said code symbols ({tilde over (c)}n−1, . . . ,{tilde over (c)}n−N+1) corresponding to said samples;
• first product means (PROD) adapted to multiply said current sample (xn) by the conjugate of a said code symbol ({tilde over (c)}n) corresponding to said current sample;
• second product means (PROD) adapted to multiply the value coming out from said first product means by the conjugate of said reconstructed phase reference;
• means (REAL) adapted to extract the real part of the value coming out from said second product means;
• means (MOD) adapted to calculate the modulus of said constructed phase reference;
• normalization means (DIV) adapted to divide said real part by said modulus;
• first adder means (4) of the quotient coming out from said normalization means (DIV) with the square modulus, changed in sign and divided by two, of said code symbol ({tilde over (c)}n) corresponding to said current sample (xn), obtaining a said relevant transition metric (λn(s)).

Non-coherent receiver of symbol sequence ({αn}), obtained impressing M phase discrete values to a carrier transmitted on a communication channel, affected by white gaussian noise, including:

• a non-coherent converter in base band of the signal received, followed by a filter (FRIC) matched to the transmission pulse, followed in its turn by a sampler (CAMP) at symbol frequency, that obtains a sequence of complex samples {xn};
• a phase reconstruction memory (SHF1) where N−1 samples (xn−1, . . . ,xn−N+1) of said sequence {xn} preceding a current sample (xn) are stored;
• calculation means (METRICTOT) of transition metrics, or branch metrics, (λn(s)) of a trellis sequential diagram, or trellis, whose branches represent all possible transitions among states defined by all possible subsequences of information symbols ({cn}) of finite length;
• a Viterbi processor adapted to select paths on the trellis such that a cumulative path metric of transition metrics, or branch metrics, is maximum, said path metric indicating the likelihood degree existing among the symbols ({{tilde over (c)}n}) of a relevant path and a transmitted sequence symbols ({cn}), characterized in that said calculation means (METRICTOT) of the transition metrics (λn(s)), are subdivided into a plurality of identical sub-means (METRIC(s)), each of them calculating a relevant transition metric (λn(s)), including:
• a memory for N code symbols ({tilde over (c)}n−1, . . . ,{tilde over (c)}n−N+1) univocally associated to a relevant branch of the trellis;
• phase reference construction means controlled by said N−1 samples (xn−1, . . . ,xn−N+1) stored in said phase reconstruction memory (SHF1) and by N−1 said code symbols ({tilde over (c)}n−1, . . . ,{tilde over (c)}n−N+1) corresponding to said samples;
• first product means (PROD) adapted to multiply said current sample (xn) by the conjugate of a said code symbol ({tilde over (c)}n) corresponding to said current sample;
• second product means (PROD) adapted to multiply the value coming out from said first product means by the conjugate of said constructed phase reference;
• means (REAL) adapted to extract the real part of the value coming out from said second product means, obtaining a said relevant transition metric (λn(s)).