Soft decision digital communication method and apparatus
AssigneeMotorola, Inc.
InventorsDariusz Andrzej Blasiak, John William Arens
Life of this patent
Estimating the term…
Abstract
A decoding apparatus (200) decodes a coherent, differentially encoded multi-level phase shift keying (DEPSK) modulated signal. A coherent receiver (101) receives and, subsequently, outputs the coherent DEPSK modulated signal to a metric computer (201). The metric computer (201) generates a soft decision metric .LAMBDA.(s(n)) corresponding to the coherent DEPSK modulated signal which is outputted to a forward error correction (FEC) decoder (107). The FEC decoder (107) decodes the coherent DEPSK modulated signal in accordance with the soft derision metric .LAMBDA.(s(n)) corresponding to the coherent DEPSK modulated signal.
Claims21
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.
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.
A method of decoding a coherent differentially encoded multi-level phase shift keying (DEPSK) modulated signal representing actual transmitted symbols, the method comprising the steps of:
- (a) coherently receiving the coherent DEPSK modulated signal;
- (b) generating a present predetermined symbol from among a set of predetermined symbols and generating a soft decision metric corresponding to the actual transmitted symbols comprising the coherent DEPSK modulated signal;
- and
- (c) outputting the soft decision metric to a forward error correction (FEC) decoder.
A method of decoding a coherent differentially encoded multi-level phase shift keying (DEPSK) modulated signal representing actual transmitted symbols, the method comprising the steps of:
- (a) coherently receiving the coherent DEPSK modulated signal;
- (b) generating a soft decision metric corresponding to the actual transmitted symbols comprising the coherent DEPSK modulated signal, said step (b) of generating a soft decision metric comprising the steps of:
- (b1) combining a present symbol of the coherent DEPSK modulated signal and a previous symbol of the coherent DEPSK modulated signal to form a combined symbol, and
- (b2) determining a maximum likelihood from among different phase angles of the combined symbol;
- and
- (c) outputting the soft decision metric to a forward error correction (FEC) decoder.
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.
Dependencies are inferred from the claim text.