Soft decision digital communication method and apparatus

Claim 2

An assembly for decoding a coherent differentially encoded multi-level phase shift keying (DEPSK) modulated signal representing actual transmitted symbols, the assembly comprising: a coherent receiver for receiving the coherent DEPSK modulated signal; a metric computer, coupled to said coherent receiver, for generating a soft decision metric corresponding to the actual transmitted symbols, the metric computer including a mixer, operatively coupled to said coherent receiver, for combining a present symbol of the coherent DEPSK modulated signal with a present predetermined symbol from a set of predetermined symbols; and a forward error correction (FEC) decoder, coupled to said metric computer, for decoding the coherent DEPSK modulated signal in accordance with the soft decision metric.

Claim 3

An assembly according to claim 1 wherein said metric computer further comprises a delayer, operatively coupled to said coherent receiver, for delaying a present symbol of the coherent DEPSK modulated signal one time interval and generating a previous symbol of the coherent DEPSK modulated signal.

Claim 4

An assembly according to claim 2 wherein said metric computer further comprises a summer, coupled to both said mixer and said delayer, for combining the present symbol of the coherent DEPSK modulated signal and the present predetermined symbol with the previous symbol of the coherent DEPSK modulated signal to form a resultant symbol.

Claim 5

An assembly according to claim 3 wherein said metric computer further comprises a phase rotator, coupled to said summer, for rotating the resultant symbol over each one of the set of predetermined symbols so as to create a set of likelihoods that the present predetermined symbol is the present one of the actual transmitted symbols.

Claim 6

An assembly according to claim 4 wherein said metric computer further comprises a real operator, coupled to said phase rotator, for extracting a real portion of each one of the set of likelihoods that the present predetermined symbol is the present one of the actual transmitted symbols.

Claim 7

An assembly according to claim 5 wherein said metric computer further comprises a maximizer, coupled to said real operator, for determining a maximum likelihood from among the set of likelihoods, the maximum likelihood forming a portion of the soft decision metric.

Claim 8

An assembly for decoding a coherent differentially encoded multi-level phase shift keying (DEPSK) modulated signal representing actual transmitted symbols, the assembly comprising: a coherent receiver for receiving the coherent DEPSK modulated signal; a metric computer, coupled to said coherent receiver, for generating a soft decision metric corresponding to the actual transmitted symbols, the metric computer including a combiner circuit operatively coupled to said coherent receiver to generate a combined symbol, and a maximum phase detector operatively coupled to said combined circuit to determine a maximum likelihood from among different phase angles of the combined symbol; and a forward error correction (FEC) decoder, coupled to said metric computer, for decoding the coherent DEPSK modulated signal in accordance with the soft decision metric.

Claim 9

An assembly for decoding a coherent differentially encoded multi-level phase shift keying (DEPSK) modulated signal representing actual transmitted symbols, the assembly comprising: a coherent receiver for receiving the coherent DEPSK modulated signal; a metric computer, coupled to said coherent receiver, for generating a soft decision metric corresponding to the actual transmitted symbols, the metric computer including a combiner circuit operatively coupled to said coherent receiver to generate a combined symbol, and a maximum phase detector operatively coupled to said combined circuit to determine a maximum likelihood from among different phase angles of the combined symbol; and a forward error correction (FEC) decoder, coupled to said metric computer, for decoding the coherent DEPSK modulated signal in accordance with the soft decision metric.

Claim 10

An assembly according to claim 7 wherein said combiner circuit comprises: a mixer operatively coupled to said coherent receiver to combine a present symbol of the coherent DEPSK modulated signal with a present predetermined symbol from a set of predetermined symbols; a delayer operatively coupled to said coherent receiver to delay the present symbol of the coherent DEPSK modulated signal one time interval and generate a previous symbol of the coherent DEPSK modulated signal; and a summer operatively coupled to said mixer and said delayer to sum the present symbol of the coherent DEPSK modulated signal and the present predetermined symbol with the previous symbol of the coherent DEPSK modulated signal to form the combined symbol.

Claim 11

An assembly according to claim 7 wherein said maximum phase detector comprises: a multiple phase angle circuit operatively coupled to said combiner circuit to provide multiple phase angle representations of the combined symbol over each one of a set of predetermined symbols so as to create a set of likelihoods that a present predetermined symbol is a present one of the actual transmitted symbols; and a maximizer operatively coupled to said multiple phase angle circuit to determine a maximum likelihood from among the set of likelihoods, the maximum likelihood forming a portion of the soft decision metric.

Claim 12

An assembly according to claim 9 wherein said multiple phase angle circuit comprises: a phase rotator operatively coupled to said combiner circuit to rotate the combined symbol over each one of a set of predetermined symbols so as to create a set of likelihoods that a present predetermined symbol is a present one of the actual transmitted symbols; and a real operator operatively coupled to said phase rotator and said maximizer to extract a real portion of each one of the set of likelihoods.

Claim 15

A method according to claim 11 wherein said step (b) of generating further comprises the substep of: (b1) combining the present predetermined symbol with a present symbol of the coherent DEPSK modulated signal.

Claim 16

A method according to claim 12 wherein said step (b) of generating further comprises the substep of: (b2) combining the present symbol of the coherent DEPSK modulated signal with a previous symbol of the coherent DEPSK modulated signal to form a resultant symbol necessary to determine the identity of a present one of the actual transmitted symbols.

Claim 17

A method according to claim 13 wherein said substep (b) of generating further comprises the substep of: (b3) rotating the resultant symbol over each one of the set of predetermined symbols so as to create a set of likelihoods that the present predetermined symbol is the present one of the actual transmitted symbols.

Claim 18

A method according to claim 14 wherein said step (b) of generating further comprises the substep of: (b4) extracting the real portion of each one of the set of likelihoods.

Claim 19

A method according to claim 14 wherein said step (b) of generating further comprises the substep of: (b5) determining a maximum likelihood from among the set of likelihoods, the maximum likelihood forms a portion of the soft decision metric.

Claim 22

A method according to claim 17 wherein said step (b1) comprises the substeps of: (b1i) mixing the present symbol of the coherent DEPSK modulated signal with a present predetermined symbol from a set of predetermined symbols; (b1ii) delaying the present symbol of the coherent DEPSK modulated signal to generate the previous symbol of the coherent DEPSK modulated signal; and (b1iii) summing the present symbol of the coherent DEPSK modulated signal and the present predetermined symbol with the previous symbol of the coherent DEPSK modulated signal to form the combined symbol.

Claim 23

A method according to claim 17 wherein said step (b2) comprises the substeps of: (b2i) generating multiple phase angle representations of the combined symbol over each one of a set of predetermined symbols so as to create a set of likelihoods that a present predetermined symbol is a present one of the actual transmitted symbols; and (b2ii) determining a maximum likelihood from among the set of likelihoods, the maximum likelihood forming a portion of the soft decision metric.

Claim 24

A method according to claim 19 wherein said step (b2i) comprises the substeps of: (b2ia) rotating the combined symbol over each one of the set of predetermined symbols so as to create the set of likelihoods that a present predetermined symbol is the present one of the actual transmitted symbols; and (b2ib) extracting a real portion of each one of the set of likelihoods.

Claim 25

An assembly for decoding a coherent differentially encoded multi-level phase shift keying (DEPSK) modulated signal representing actual transmitted symbols, the assembly comprising: a coherent receiver for receiving the coherent DEPSK modulated signal; a metric computer, coupled to said coherent receiver, for generating a soft decision metric corresponding to the actual transmitted symbols comprising the coherent DEPSK modulated signal, said metric computer further comprising: a mixer for combining a present symbol of the coherent DEPSK modulated signal with a present predetermined symbol from a set of predetermined symbols to form a rotated symbol; a delayer for delaying a present symbol of the coherent DEPSK modulated signal one time interval so as to generate a previous symbol of the coherent DEPSK modulated signal; a summer, coupled to said mixer and said delayer, for summing the rotated symbol and the previous symbol of the coherent DEPSK modulated signal to form a resultant symbol to identify a present one of the actual transmitted symbols; a phase rotator, coupled to said summer, for rotating the resultant symbol over each one of the set of predetermined symbols so as to create a set of likelihoods that the present predetermined symbol is the present one of the actual transmitted symbols; a real operator, coupled to said phase rotator, for extracting the real portion of each one of the set of likelihoods that the present predetermined symbol is the present one of the actual transmitted symbols; and a maximizer, coupled to said real operator, for determining a maximum likelihood from among the set of likelihoods, wherein the maximum likelihood forms a portion of the soft decision metric; and a forward error correction (FEC) decoder, coupled to the metric computer, for decoding the coherent DEPSK modulated signal in accordance with said soft decision metric corresponding to the coherent DEPSK modulated signal.

Claim 26

An assembly for decoding a coherent differentially encoded multi-level phase shift keying (DEPSK) modulated signal representing actual transmitted symbols, the assembly comprising: a coherent receiver for receiving the coherent DEPSK modulated signal; a metric computer, coupled to said coherent receiver, for generating a soft decision metric corresponding to the actual transmitted symbols comprising the coherent DEPSK modulated signal, said metric computer further comprising: a mixer for combining a present symbol of the coherent DEPSK modulated signal with a present predetermined symbol from a set of predetermined symbols to form a rotated symbol; a delayer for delaying a present symbol of the coherent DEPSK modulated signal one time interval so as to generate a previous symbol of the coherent DEPSK modulated signal; a summer, coupled to said mixer and said delayer, for summing the rotated symbol and the previous symbol of the coherent DEPSK modulated signal to form a resultant symbol to identify a present one of the actual transmitted symbols; a phase rotator, coupled to said summer, for rotating the resultant symbol over each one of the set of predetermined symbols so as to create a set of likelihoods that the present predetermined symbol is the present one of the actual transmitted symbols; a real operator, coupled to said phase rotator, for extracting the real portion of each one of the set of likelihoods that the present predetermined symbol is the present one of the actual transmitted symbols; and a maximizer, coupled to said real operator, for determining a maximum likelihood from among the set of likelihoods, wherein the maximum likelihood forms a portion of the soft decision metric; and a forward error correction (FEC) decoder, coupled to the metric computer, for decoding the coherent DEPSK modulated signal in accordance with said soft decision metric corresponding to the coherent DEPSK modulated signal.