EP0134101A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Differentially nonlinear convolutional channel coding with expanded set of signalling alphabets
Assignee: AT&T Inc
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Filing: 1984-07-30
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Granted: —
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Expires: 2004-07-30
Abstract
Abstract A technique for converting a sequence of binary digits into a sequence of signalling alphabets of a modulated carrier signal for data transmission. By differentially encoding incoming data (250), non-linearly encoding (260) the differentially encoded output in a state-dependet sequential manner and mapping the non-linearly encoded output into an expanded set of signalling alphabets having 90, 180 and 270 degree phase ambiguities, enlarged minimum Euclidean distance between possible sequences of signalling alphabets is achieved while the effect of the phase ambiguities of the expanded set of signalling alphabets can be removed in the receiver. This results in a reduced error probalility when maximum likelihood decoding and differential decoding are applied in the receiver.
Inventors
- 👤 Lee-Fang Wei
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 16:30
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/32; H04L27/34; H04L27/3405; H04L27/3416; H04L27/3427; H04L27/3433; H04L1/00; H04L1/004; H04L1/0045; H04L1/0054
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
305 words
A method for transmitting a bit sequence by modulating a carrier signal to sequentially assume one of a plurality of pairs of discrete signal values, CHARACTERIZED BY the steps of: a) differentially encoding bits in each group of r bits in said sequence by rotating the values of bits in the previous differentially encoded r bit group in accordance with the values of bits in the current r bit group, b) expanding each differentially encoded r bit group into a group of r+1 bits by a non-linear convolutional coding process utilizing m internal states, the current state of said convolutional code being determined by p stored bits, where 2 P =m, said p stored bits being functions of the previous bits input to said convolutional encoder and affecting the output of said convolutional encoder, c) selecting one of 2 r+1 signalling alphabets from a signal constellation, each alphabet corresponding to a pair of discrete signal values, said selection being made as a function of the r+1 bit group so that 2 r signalling alphabets correspond to all permitted transitions from each current internal state of said convolutional coding process to m possible next states of said convolutional coding process, and so that the 2 r signalling alphabets have a larger minimum distance from each other than the minimum distance within the complete set of 2 r+1 signalling alphabets, and d) transmitting the pairs of discrete signal values corresponding to the selected signalling alphabets in sequence, wherein said signal constellation is arranged so that the same signal constellation is obtained when the original constellation is rotated by 90, 180 or 270 degrees, and wherein rotation of said constellation by 90, 180 or 270 degrees produces the same effect on said transmitted discrete signal values as rotation of said differentially encoded bits in each r bit group.
Claim 2
Independent Claim
305 words
A method for transmitting a bit sequence by modulating a carrier signal to sequentially assume one of a plurality of pairs of discrete signal values, CHARACTERIZED BY the steps of: a) differentially encoding bits in each group of r bits in said sequence by rotating the values of bits in the previous differentially encoded r bit group in accordance with the values of bits in the current r bit group, b) expanding each differentially encoded r bit group into a group of r+1 bits by a non-linear convolutional coding process utilizing m internal states, the current state of said convolutional code being determined by p stored bits, where 2 P =m, said p stored bits being functions of the previous bits input to said convolutional encoder and affecting the output of said convolutional encoder, c) selecting one of 2 r+1 signalling alphabets from a signal constellation, each alphabet corresponding to a pair of discrete signal values, said selection being made as a function of the r+1 bit group so that 2 r signalling alphabets correspond to all permitted transitions from each current internal state of said convolutional coding process to m possible next states of said convolutional coding process, and so that the 2 r signalling alphabets have a larger minimum distance from each other than the minimum distance within the complete set of 2 r+1 signalling alphabets, and d) transmitting the pairs of discrete signal values corresponding to the selected signalling alphabets in sequence, wherein said signal constellation is arranged so that the same signal constellation is obtained when the original constellation is rotated by 90, 180 or 270 degrees, and wherein rotation of said constellation by 90, 180 or 270 degrees produces the same effect on said transmitted discrete signal values as rotation of said differentially encoded bits in each r bit group.
Claim 3
Dependent Claim
301 words
Apparatus for modulating in-phase and quadrature phase carriers to assume a sequence of discrete values u n and v n , respectively, in accordance with an applied sequence of bits, including: means for expanding each current group of r bits in said applied sequence into a group of r+1 bits in accordance with the state of an m-state convolutional code, means for selecting said discrete values in accordance with the coordinates of the one of 2 r+1 signalling alphabets associated with the values of the bits in each expanded r+1 bit group, said selecting means being arranged so that 2 r signalling alphabets correspond to all permitted transitions from each current one of said m states to m possible next states, and so that the minimum distance between said 2 r signalling alphabets is larger than the minimum distance between the complete set of Z r+1 signalling alphabets, and means for modulating said in-phase and quadrature-phase carriers in accordance with said selected discrete values, CHARACTERIZED IN THAT said apparatus further includes means for differentially encoding at least one pair of bits in each group of r bits applied to said expanding means by rotating the values of a pair of previous differentially encoded bits by a position differential determined by the values of said bits in said at least one pair of bits, said expanding means is arranged to determine bits in said r+1 bit group as a non-linear function of bits in said current and previous r bits groups, and said selecting means is arranged to form said signalling alphabets in a constellation with only 90, 180 and 270 degree symmetry such that rotation of said differentially encoded bits processed in said expanding step has the same effect as rotation of said signalling alphabets by 90, 180 or 270 degrees.
Claim 4
Dependent Claim
301 words
Apparatus for modulating in-phase and quadrature phase carriers to assume a sequence of discrete values u n and v n , respectively, in accordance with an applied sequence of bits, including: means for expanding each current group of r bits in said applied sequence into a group of r+1 bits in accordance with the state of an m-state convolutional code, means for selecting said discrete values in accordance with the coordinates of the one of 2 r+1 signalling alphabets associated with the values of the bits in each expanded r+1 bit group, said selecting means being arranged so that 2 r signalling alphabets correspond to all permitted transitions from each current one of said m states to m possible next states, and so that the minimum distance between said 2 r signalling alphabets is larger than the minimum distance between the complete set of Z r+1 signalling alphabets, and means for modulating said in-phase and quadrature-phase carriers in accordance with said selected discrete values, CHARACTERIZED IN THAT said apparatus further includes means for differentially encoding at least one pair of bits in each group of r bits applied to said expanding means by rotating the values of a pair of previous differentially encoded bits by a position differential determined by the values of said bits in said at least one pair of bits, said expanding means is arranged to determine bits in said r+1 bit group as a non-linear function of bits in said current and previous r bits groups, and said selecting means is arranged to form said signalling alphabets in a constellation with only 90, 180 and 270 degree symmetry such that rotation of said differentially encoded bits processed in said expanding step has the same effect as rotation of said signalling alphabets by 90, 180 or 270 degrees.
Claim 5
Dependent Claim
78 words
Apparatus as claimed in claim 2, CHARACTERISED IN THAT each of said m-states of said m-state convolutional code is defined by p stored bits, where s p =m, said p stored bits being determined by bits in previous r bit groups, and said expanding means includes means for determining said p bits which define said next state as a non-linear function of said p bits which define said current state and bits in said current r bit group.
References Cited (Backward Citations)
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