US5457704A
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Post processing method and apparatus for symbol reliability generation
Assignee: AT&T Inc
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Filing: 1993-05-21
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Granted: 1995-10-10
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Expires: 2013-05-21
Abstract
Abstract A method for a post-processors provides reliability information about every decoded data symbol at the output of an arbitrary decoder. This reliability information is generated by comparing the decoded sequence to a small list of alternative sequences which differ from the decoded sequence at least in the symbol for which the reliability is being evaluated. It is shown that this algorithm is a simplification of the optimal symbol-by-symbol detector (OSSD).
Inventors
- 👤 Peter Hoeher
- 👤 Nambirajan Seshadri
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 19:45
CPC Classifications
H; H03; H03M; H03M13/00; H03M13/37; H03M13/39; H03M13/41; H03M13/4138; H03M13/4146
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
164 words
A method for generating a signal comprising reliability information for a given symbol in a first signal in a decoding system wherein said decoding system comprises a first decoder, wherein said first decoder decodes a received signal to generate said first signal, said method comprising the steps of: determining the likelihood of the received signal given the first signal, said received signal having been received over a communications channel corrupted by noise; selecting a set of L nearest neighbors to said first signal wherein each nearest neighbor differs from said first signal in the given symbol; determining a set of L likelihoods each representing the likelihood of the received signal given a respective nearest neighbor in the selected set of nearest neighbors; selecting the nearest neighbor with the greatest likelihood; generating a signal representing a reliability value for the given symbol in said first signal wherein said reliability value is a function of said received signal, said first signal and said selected nearest neighbor.
Claim 2
Independent Claim
164 words
A method for generating a signal comprising reliability information for a given symbol in a first signal in a decoding system wherein said decoding system comprises a first decoder, wherein said first decoder decodes a received signal to generate said first signal, said method comprising the steps of: determining the likelihood of the received signal given the first signal, said received signal having been received over a communications channel corrupted by noise; selecting a set of L nearest neighbors to said first signal wherein each nearest neighbor differs from said first signal in the given symbol; determining a set of L likelihoods each representing the likelihood of the received signal given a respective nearest neighbor in the selected set of nearest neighbors; selecting the nearest neighbor with the greatest likelihood; generating a signal representing a reliability value for the given symbol in said first signal wherein said reliability value is a function of said received signal, said first signal and said selected nearest neighbor.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein said first signal is a maximum likelihood sequence estimate generated by a Viterbi decoder.
Claim 4
Dependent Claim
18 words
The method of claim 1 wherein said signal representing said reliability value is input to a second decoder.
Claim 5
Dependent Claim
42 words
The method of claim 1 wherein said set of L nearest neighbors is generated from knowledge of a code, said code having distance properties, and from the distance properties of said code wherein said code was used to encode said received signal.
Claim 6
Dependent Claim
31 words
The method of claim 1 wherein said set of L nearest neighbors is generated by selecting an alternative set of symbol values for symbols within a window around said given bit.
Claim 7
Dependent Claim
78 words
The method of claim 1 wherein said first decoder is a suboptimal decoder and further comprising the steps of: selecting a set of k symbols in said first signal; determining the likelihood of each second signal in a set of second signals wherein each second signal is formed by substituting for said set of k symbols in said first signal an alternative set of k symbols; and replacing said first signal by the second signal having maximum likelihood.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-10-09 | 1999-04-10 | 1999-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-10-09 | 2003-04-10 | 2003-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-10-09 | 2007-04-10 | 2007-10-10 | $7700.00 | Window Closed / Lapsed |