EP0485108A2
Expired / Lapsed
EP
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Coded modulation with unequal levels of error protection
Assignee: AT&T Inc
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Filing: 1991-10-30
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Granted: —
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Expires: 2011-10-30
Abstract
Abstract Digital signals, such as digitized television signals, are subjected to a source coding step in which a class of "most important" data elements represents a proportionately greater amount of the information to be communicated than the rest of the data elements. This is followed by a constellation mapping step which is carried out in such a way that those data elements have a lower probability of being erroneously detected at the receiver than the others. The constellation mapping step uses coded modulation in order to provide enhanced noise immunity for the "most important" data element class.
Inventors
- 👤 Lee-Fang Wei
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 23:52
CPC Classifications
H; H03; H03M; H03M13/00; H03M13/35; H04; H04N; H04N7/00; H04N7/12; H04L; H04L27/00; H04L27/32; H04L27/34; H04L27/3405; H04L27/3416; H04L27/3422; H04L27/3488; H04N21/00; H04N21/40; H04N21/41; H04N21/426; H04N7/08; H04L1/00; H04L2001/0098
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
126 words
A method CHARACTERIZED BY the steps of encoding a first group of data elements to generate a first expanded group of data elements, identifying one of a plurality of supersymbols of a predetermined channel symbol constellation in response to the first expanded group of data elements, each supersymbol being comprised of a respective plurality of symbols of the constellation, selecting an individual one of the symbols of the identified supersymbol at least in response to a second group of data elements, and applying to a communication channel a signal representing the selected symbol, the minimum distance between at least ones of the symbols of at least one of the supersymbols being the same as the minimum distance betweeen the symbols of the constellation as a whole.
Claim 2
Dependent Claim
46 words
The invention of claim 1 CHARACTERIZED IN THAT the selecting step includes the steps of encoding said second group of data elements to generate a second expanded group of data elements, and selecting said individual symbol in response to the second expanded group of data elements.
Claim 3
Dependent Claim
23 words
The invention of claim 1 CHARACTERIZED IN THAT said encoding step includes the step of trellis coding said first group of data elements.
Claim 4
Dependent Claim
54 words
The invention of claim 1 CHARACTERIZED BY the further step of generating said data elements by source coding input information in such away that said first group of data elements represents a portion of said information that is more important than the portion of said information represented by said second group of data elements.
Claim 5
Dependent Claim
13 words
The invention of claim 4 CHARACTERIZED IN THAT said information is television information.
Claim 6
Dependent Claim
24 words
The invention of claim 1 CHARACTERIZED BY the further step of rearranging the first expanded group of data elements prior to said identifying step.
Claim 7
Dependent Claim
24 words
The invention of claim 1 CHARACTERIZED IN THAT at least one of said supersymbols is comprised of at least two non-contiguous groups of symbols.
Claim 8
Independent Claim
241 words
A method for use in a receiver which receives intelligence communicated to said receiver by a transmitter, said transmitter being adapted to channel code successive groups of m+k data bits associated with respective symbol intervals via the steps, performed for each said interval, of a) encoding m of the bits of one of the groups using a first predetermined code to generate an expanded group of r bits, r > m; b) identifying a particular one of 2 τ supersymbols of a predetermined channel symbol constellation as a function of the values of said r bits, each of said supersymbols being comprised of a plurality of symbols of said constellation assigned thereto and the minimum distance between the symbols of each supersymbol being the same as the minimum distance between the symbols of the constellation as a whole; c) generating a signal representing a selected one of the channel symbols of the identified one supersymbol, the selection being performed as a function of the values of the other k bits of said one group; and d) communicating said signal to said receiver over a communication channel; said method CHARACTERIZED BY the steps of receiving said signal from said channel, and recovering said intelligence from the received signal, said recovering being carried out in response to information stored in said receiver about said first predetermined code, about said constellation, and the manner in which said symbols are assigned to their respective supersymbols.
Claim 9
Dependent Claim
89 words
The invention of claim 8 CHARACTERIZED IN THAT the signal generating step in the transmitter includes the steps of a) encoding the other k bits of said one of the groups using a second predetermined code to generate a second expanded group of p bits, p > k; and b) selecting said individual symbol in response to the second expanded group of data bits, and FURTHER CHARACTERIZED IN THAT said recovering step is carried out further in response to information stored in said receiver about said second predetermined code.
Claim 10
Dependent Claim
13 words
The invention of claim 9 CHARACTERIZED IN THAT said intelligence is television information.
Claim 11
Dependent Claim
31 words
The invention of claim 10 CHARACTERIZED IN THAT said recovering step includes the step of decoding the received signal to recover said successive groups of data bits using maximum likelihood decoding.
Claim 12
Dependent Claim
149 words
Apparatus operative during each of a successsion of symbol intervals for channel coding respective groups of m+k data bits, said apparatus CHARACTERIZED BY means for encoding m of the bits of one of the groups to generate an expanded group of r bits, r > m, means for identifying a particular one of 2 τ supersymbols of a predetermined channel symbol constellation as a function of the values of said r bits, each of said supersymbols being comprised of a plurality of symbols of said constellation, and means for generating a signal representing a selected one of the channel symbols of the identified one supersymbol, the selection being performed as a function of the values of the other k bits of said one group, the minimum distance between the symbols of each supersymbol being the same as the minimum distance between the symbols of the constellation as a whole.
Claim 13
Dependent Claim
14 words
The invention of claim 12 CHARACTERIZED IN THAT said data bits represent television information.
Claim 14
Dependent Claim
48 words
The invention of claim 13 FURTHER CHARACTERIZED BY means for generating said data bits by source coding input information in such a way that said m bits represent a portion of said information that is more important than the portion of said information represented by said k bits.
Claim 15
Dependent Claim
52 words
The invention of claim 14 CHARACTERIZED IN THAT said generating means includes means for encoding the other k bits of said one of the groups to generate an expanded group of p bits, p > k, and means for selecting said individual symbol in response to said expanded group of p bits.
Claim 16
Dependent Claim
25 words
The invention of claim 15 CHARACTERIZED IN THAT said m-bit and k-bit encoding means include means for trellis coding said m and k bits, respectively.
Claim 17
Dependent Claim
25 words
The invention of claim 15 CHARACTERIZED IN THAT at least ones of said supersymbols are each comprised of at least two non-contiguous groups of symbols.
Claim 18
Dependent Claim
22 words
The invention of claim 16 FURTHER CHARACTERIZED BY means for rearranging said expanded group of r bits prior to said identifying step.
Claim 19
Dependent Claim
221 words
An arrangement for use in a receiver which receives intelligence communicated to said receiver by a transmitter, said transmitter including apparatus for a) encoding a first stream of the data elements using a first predetermined code to generate a first expanded stream of data elements; b) identifying a sequence of supersymbols of a predetermined channel symbol constellation in response to the first expanded stream of data elements, the minimum distance between at least ones of the symbols of at least one of the supersymbols being the same as the minimum distance betweeen the symbols of the constellation as a whole; c) encoding a second stream of data elements using a second predetermined code to generate a second expanded stream of data elements; d) selecting an individual one of the symbols of each supersymbol of said sequence at least as a function of the second expanded stream of data elements; and d) means for applying to a communication channel a signal representing the selected symbols, said arrangement CHARACTERIZED BY means for receiving the signal from the communication channel, and means for carrying out a maximum likelihood decoding operation on the received signal to recover said first stream of data elements and for carrying out a second maximum likelihood decoding operation on the received signal to recover said second stream of data elements.
Claim 20
Dependent Claim
16 words
The invention of claim 19 CHARACTERIZED IN THAT said first and second codes are trellis codes.
Claim 21
Dependent Claim
13 words
The invention of claim 19 CHARACTERIZED IN THAT said intelligence is television information.
References Cited (Backward Citations)
No citation records indexed.
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