US4713829A — Coded modulation system with a simplified decoder…

Claim 1

Independent Claim 171 words

A receiver for deciding which signal points were sent from a transmitter based on corresponding noise affected signals received via a distorting channel, said noise affected signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible said encoding states, said receiver comprising modifying circuitry for generating a plurality of different modified versions of each said received signal, and a decoder having a finite number of possible decoder states based on said possible encoding states, and for deciding which signal points were sent based on said decoder estimating a particular time sequence of said decoder states corresponding to said particular sequence of encoding states, by storing a number of path histories of previous signal points in said decoder, and using said modified versions to extend said path histories to later time intervals, said different modified versions of each said received signal numbering fewer than said number of said stored path histories.

Claim 2

Dependent Claim 171 words

A receiver for deciding which signal points were sent from a transmitter based on corresponding noise affected signals received via a distorting channel, said noise affected signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible said encoding states, said receiver comprising modifying circuitry for generating a plurality of different modified versions of each said received signal, and a decoder having a finite number of possible decoder states based on said possible encoding states, and for deciding which signal points were sent based on said decoder estimating a particular time sequence of said decoder states corresponding to said particular sequence of encoding states, by storing a number of path histories of previous signal points in said decoder, and using said modified versions to extend said path histories to later time intervals, said different modified versions of each said received signal numbering fewer than said number of said stored path histories.

Claim 3

Dependent Claim 186 words

A receiver for deciding which signal points were sent from a transmitter based on corresponding nosie affected signals received via a distorting channel, said noise affected signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible encoding states, said receiver comprising modifying circuitry for generating a plurality of different modified versions of each said received signal, and a decoder having a finite number of possible decoder states based on said possible encoding states, for deciding which signal points were sent based on said decoder estimating a particular time sequence of said decoder states corresponding to said particular sequence of encoding states by storing a number of path histories of previous signal points in said decoder, and for partitioning a constellation from which said signal points are drawn into decision subsets and associating transitions from a possible decoder state with one of said decision subsets based on signal points stored in said path histories, each said modified version being associated with one of said decision subsets.

Claim 4

Dependent Claim 186 words

A receiver for deciding which signal points were sent from a transmitter based on corresponding nosie affected signals received via a distorting channel, said noise affected signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible encoding states, said receiver comprising modifying circuitry for generating a plurality of different modified versions of each said received signal, and a decoder having a finite number of possible decoder states based on said possible encoding states, for deciding which signal points were sent based on said decoder estimating a particular time sequence of said decoder states corresponding to said particular sequence of encoding states by storing a number of path histories of previous signal points in said decoder, and for partitioning a constellation from which said signal points are drawn into decision subsets and associating transitions from a possible decoder state with one of said decision subsets based on signal points stored in said path histories, each said modified version being associated with one of said decision subsets.

Claim 5

Independent Claim 198 words

A method for deciding which signal points were sent from a transmitter based on corresponding signals received via a noisy distorting channel having an effective memory of K signaling intervals, said received signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible said encoding states, said method comprising storing a plurality of path histories with respect to each said encoder state, said path histories having the property that for each encoder state the sequences of K most recent signal points in the associated said path histories belong to respectively different ones of a number of predefined subsets of the set of all possible sequences of K most recent signal points with respect to said encoder state, said number of predefined subsets being fewer than the number of said possible sequences, said stored path histories satisfying the condition that any sequences of K' (K'<K) most recent signal points in all said path histories with respect to each said encoder state do not all correspond respectively to different ones of all possible sequences of K' most recent signal points.

Claim 6

Independent Claim 198 words

A method for deciding which signal points were sent from a transmitter based on corresponding signals received via a noisy distorting channel having an effective memory of K signaling intervals, said received signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible said encoding states, said method comprising storing a plurality of path histories with respect to each said encoder state, said path histories having the property that for each encoder state the sequences of K most recent signal points in the associated said path histories belong to respectively different ones of a number of predefined subsets of the set of all possible sequences of K most recent signal points with respect to said encoder state, said number of predefined subsets being fewer than the number of said possible sequences, said stored path histories satisfying the condition that any sequences of K' (K'<K) most recent signal points in all said path histories with respect to each said encoder state do not all correspond respectively to different ones of all possible sequences of K' most recent signal points.

Claim 7

Dependent Claim 231 words

A receiver for deciding which signal points were sent from a transmitter based on corresponding signals received via a noisy distorting channel having an effective memory of K signaling intervals, said received signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible said encoding states, said receiver comprising a decoder having means for storing a plurality of path histories with respect to each encoder state, said path histories having the property that for each encoder state the sequences of K most recent signal points in the associated said path histories to respectively different ones of a number of predefined subsets of the set of all possible sequences of K most recent signal points with respect to said encoder state, said number of predefined subsets being fewer than the number of said possible sequences, said stored path histories satisfying the condition that if sequences of K' (K'<K) most recent signal points in all said path histories with respect to each said encoder state always correspond respectively to different ones of all possible sequences of K' most recent signal points, then for at least one said path history, the sequence of next K-K' most recent signal points is not allowed to take all possible values of signal points for that encoder state.

Claim 8

Dependent Claim 231 words

A receiver for deciding which signal points were sent from a transmitter based on corresponding signals received via a noisy distorting channel having an effective memory of K signaling intervals, said received signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state device in said transmitter having a finite number of possible said encoding states, said receiver comprising a decoder having means for storing a plurality of path histories with respect to each encoder state, said path histories having the property that for each encoder state the sequences of K most recent signal points in the associated said path histories to respectively different ones of a number of predefined subsets of the set of all possible sequences of K most recent signal points with respect to said encoder state, said number of predefined subsets being fewer than the number of said possible sequences, said stored path histories satisfying the condition that if sequences of K' (K'<K) most recent signal points in all said path histories with respect to each said encoder state always correspond respectively to different ones of all possible sequences of K' most recent signal points, then for at least one said path history, the sequence of next K-K' most recent signal points is not allowed to take all possible values of signal points for that encoder state.

Claim 9

Dependent Claim 20 words

The receiver of claim 1, 2, or 4 wherein said finite number of encoder states in said transmitter is one.

Claim 10

Dependent Claim 74 words

The receiver of claim 1, 2, or 4 wherein said finite state device comprises an encoder in said transmitter for encoding a stream of information symbols into said signal points, said signal points being drawn from a constellation that is partitioned into encoder subsets, possible transitions from one said possible encoding state in a first time interval to one said possible encoding state in a next time interval being associated with said encoder subsets.

Claim 11

Dependent Claim 55 words

The receiver of claim 4 wherein said decoder further comprises means for selecting, with respect to each encoder state in a next said time interval, those extensions of path histories for which the resulting path histories have the minimum accumulated metrics from among all said extensions associated with a given one of said predefined subsets.

Claim 12

Dependent Claim 32 words

The receiver of claim 1 or 2 wherein said modifying circuitry generates a plurality of alternative decisions for said received signals, said different modified versions being based on different said alternative decisions.

Claim 13

Dependent Claim 42 words

The receiver of claim 8 wherein said decoder generates final decisions about which signal point was sent after a plurality of said time intervals have passed, and said modifying circuitry generates said alternative decisions after fewer said time intervals or no delay.

Claim 14

Dependent Claim 24 words

The receiver of claim 8 wherein said modifying circuitry associates each said alternative decision with a particular decision subset of possible said signal points.

Claim 15

Dependent Claim 21 words

The receiver of claim 10 wherein said decision subsets are formed by partitioning the constellation of all possible said signal points.

Claim 16

Dependent Claim 83 words

The receiver of claim 10 wherein said finite state devices comprises an encoder in said transmitter for encoding a stream of information symbols into said signal points, said signal points being drawn from a constellation that is partitioned into encoder subsets, possible transitions from one said possible encoding state in a first time interval to one said possible encoding state in a next time interval being associated with said encoder subsets, and wherein said decision subsets are the same as said encoder subsets.

Claim 17

Dependent Claim 82 words

The receiver of claim 10 wherein said finite state process comprises an encoder in said transmitter for encoding a stream of information symbols into said signal points, said signal points being drawn from a constellation that is partitioned into encoder subsets, possible transitions from one said possible encoding state in a first time interval to one said possible encoding state in a next time interval being associated with said encoder subsets, and wherein said decision subsets are different from said encoder subsets.

Claim 18

Dependent Claim 81 words

The receiver of claim 10 wherein said finite state device comprises an encoder in said transmitter for encoding a stream of information symbols into said signal points, said signal points being drawn from a constellation that is partitioned into encoder subsets, possible transitions from one said possible encoding state in a first time interval to one said possible encoding state in a next time interval being associated with said encoder subsets, and said decision subsets are unions of said encoder subsets.

Claim 19

Dependent Claim 26 words

The receiver of claim 10 wherein said decision subsets have a dimensionality that is larger than the dimensionality of the signal constellation of said signal points.

Claim 20

Dependent Claim 39 words

The receiver of claim 10 wherein said modifying circuitry generates said alternative decisions by choosing the signal point in each said decision subset which is closest, in the sense of Euclidean distance, to the most recent said received signals.

Claim 21

Dependent Claim 57 words

The receiver of claim 10 wherein said modifying circuitry comprises a plurality of noise predictors, each of which generates one of said modified versions by offsetting each said received signal by a noise prediction value, said noise prediction values for said noise predictors being based on errors between prior said received signals and corresponding said alternative decisions.

Claim 22

Dependent Claim 31 words

The receiver of claim 1, 2 or 4 wherein said time interval spans the period required to transmit a plurality of said signal points in a plurality of successive signaling intervals.

Claim 23

Dependent Claim 15 words

The receiver of claim 18 wherein each said time interval spans two said signaling intervals.

Claim 24

Dependent Claim 47 words

The receiver of claim 1, 2, or 4 wherein said transmitter further comprises a modulator for modulating a carrier in accordance with signal points for transmission over said channel, and said receiver further comprises a demodulator for deriving said noise effected received signal from said modulated carrier.

Claim 25

Dependent Claim 18 words

The receiver of claim 1, 2, or 4 wherein said number of path histories is greater than two.

Claim 26

Dependent Claim 17 words

The receiver of claim 9 wherein there are four said decision subsets and four said modified versions.

Claim 27

Dependent Claim 25 words

The receiver of claim 7 wherein said decoder calculates each said accumulated metric as the sum of a stored path metric plus a branch metric.

Claim 28

Dependent Claim 189 words

The receiver of claim 1 or 2 wherein each said time interval spans a plurality of signaling intervals, said decoder estimates said particular sequence of decoder states based on estimating the most likely of said possible path histories ending in different ones of possible decoder states in a first time interval, and based on extending said path histories for each said possible decoder state in said first time interval to possible decoder states in a next time interval by means of branch metric calculations with respect to state transitions leading to each of said possible decoder states in the next time interval, said decoder defines a group of decision subsets of said possible signal points, said decoder makes said branch metric calculations by finding the Euclidean distance between the modified version associated with a decision subset for the most recent signal points in said path histories and the closest signal point in the said encoder subset of signal points that is associated with the current signaling interval, and said decoder makes said branch metric calculations successively with respect to each of said signal points spanned by said time interval.

Claim 29

Dependent Claim 158 words

The receiver of claim 1 or 2 wherein said decoder estimates said particular sequence of decoder states based on estimating the most likely of said possible path histories ending in different ones of possible decoder states in a first time interval, and based on extending said path histories for each said possible decoder state in said first time interval to possible decoder states in a next time interval by means of branch metric calculations with respect to state transitions leading to each of said possible decoder states in the next time interval, said decoder defines a group of decision subsets of said possible signal points, and said decoder makes said branch metric calculations by finding the Euclidean distance between the modified version associated with a decision subset for the most recent signal points in said path histories and the closest signal point in the said encoder subset of signal points that is associated with the current signaling interval.

Claim 30

Dependent Claim 34 words

The receiver of claim 24 wherein said decoder makes said branch metric calculation by finding the Euclidean distance between each said modified version and the nearest signal point in each of said encoder subsets.

Claim 31

Dependent Claim 24 words

The receiver of claim 4 wherein said decoder further comprises modifying circuitry for generating a plurality of modified versions of each said received signal.

Claim 32

Dependent Claim 22 words

The receiver of claim 1, 2, or 4 wherein said decoder further comprises means for storing path metrics for said path histories.

Claim 33

Dependent Claim 25 words

The receiver of claim 4 wherein said decoder comprises means for extending said path histories to include subsequent signal points by using branch metric calculations.

Claim 34

Dependent Claim 42 words

The receiver of claim 27 wherein said decoder further comprises means for making branch metric calculations by finding the Euclidean distance between the modified version associated with a path history and the signal points which are possible extensions of said path history.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-12-14	1991-06-15	1991-12-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-12-14	1995-06-15	1995-12-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-12-14	1999-06-15	1999-12-15	$7700.00	Window Closed / Lapsed

Coded modulation system with a simplified decoder capable of reducing the effects of channel distortion

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