Patent US4937574A successfully refreshed from Google Patents.
US4937574A
Expired / Lapsed
US
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Data conversion
Assignee: British Broadcasting Corp
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Filing: 1987-04-23
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Granted: 1990-06-26
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Expires: 2007-04-23
Abstract
Abstract In a method for converting n data input bits to n data output bits, groups of m data input bits from an input data buffer (10) are used as address input for a plurality of identical substitution look-up tables (20 to 27). Each look-up table (20 to 27) has a plurality of groups of m data output bits stored at a plurality of locations in the table. The output bits held at each location within the look-up tables (20 to 27) are dependent on a control word taken from a control word register (11).
Inventors
- 👤 Derek T. Wright
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:22
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/06; H04L9/0618; H04L2209/00; H04L2209/08; H04L2209/12
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
133 words
In a method of converting n data input bits to n data output bits which includes the step of applying groups of m data input bits as address input to a substitution look-up table having a plurality of groups of m data output bits stored at a plurality of locations therein and wherein the output bits held at each location within the look-up table are dependent on a control word comprising a plurality of bits applied to the look-up table; the improvement comprising applying groups of the m data bits forming the control word to the look-up table as address input; and varying the contents of the look-up table in dependence on the data bits output by the look-up table following the application of groups of m data bits from the control word.
Claim 2
Dependent Claim
133 words
In a method of converting n data input bits to n data output bits which includes the step of applying groups of m data input bits as address input to a substitution look-up table having a plurality of groups of m data output bits stored at a plurality of locations therein and wherein the output bits held at each location within the look-up table are dependent on a control word comprising a plurality of bits applied to the look-up table; the improvement comprising applying groups of the m data bits forming the control word to the look-up table as address input; and varying the contents of the look-up table in dependence on the data bits output by the look-up table following the application of groups of m data bits from the control word.
Claim 3
Dependent Claim
50 words
In a method according to claim 1 and further comprising the step of re-locating groups of data output bits stored in the look-up table in a manner determined by the data bits output by the look-up table when the control word is applied to the look-up table as address input.
Claim 4
Dependent Claim
43 words
In a method according to claim 2 in which the re-locating step includes exchanging the groups of m data output bits held at one or more pairs of locations within the look-up table determined by the data bits output by the look-up table.
Claim 5
Dependent Claim
61 words
In a method according to claim 2 and further comprising the step of applying the data output bits obtained from the look-up table, following application of the control word, to the input of the look-up table, and re-circulating said data output bits through the look-up table one or more times prior to each change to the contents of the look-up table.
Claim 6
Dependent Claim
29 words
In a method according to claim 1 and further including the step of changing the order of the data input bits prior to being applied to the look-up table.
Claim 7
Dependent Claim
19 words
In a method according to claim 5 wherein said order is changed by means of a bit permutation matrix.
Claim 8
Dependent Claim
14 words
In a method according to claim 1 wherein the control word has n bits.
Claim 9
Dependent Claim
39 words
In a method according to claim 4 wherein the steps of varying the contents of the look-up table and re-circulating the data bits outputs by the look-up table through the look-up table are repeated a predetermined number of times.
Claim 10
Dependent Claim
93 words
A method of converting n data input bits into n data bits for transmission through a data transmission link and for converting the n data bits received following transmission through the link into n data output bits corresponding to the n data input bits, in which the conversion process carried out at the receiving end of the link is in accordance with claim 1, the contents of the look-up table being determined and the inverse look-up table being provided for use in converting the input data bits into the data bits for transmission.
Claim 11
Dependent Claim
90 words
Apparatus for converting n data input bits into n data output bits including a substitution look-up table having a plurality of locations addressable by groups of m data input bits each containing a group of m output bits, means for storing a control word, and means for changing the contents of the look-up table in dependence on the data bits output by the look-up table and in response to the application of groups of the m data bits forming the stored control word as address input to the look-up table.
Claim 12
Dependent Claim
90 words
Apparatus for converting n data input bits into n data output bits including a substitution look-up table having a plurality of locations addressable by groups of m data input bits each containing a group of m output bits, means for storing a control word, and means for changing the contents of the look-up table in dependence on the data bits output by the look-up table and in response to the application of groups of the m data bits forming the stored control word as address input to the look-up table.
Claim 13
Dependent Claim
64 words
Apparatus according to claim 10 including means for storing a plurality of groups of m data bits which are initially fed into the plurality of locations in the look-up table, means for applying the control word to the input of the look-up table, and means for changing the contents of the look-up table in dependence on the data bits output by the look-up table.
Claim 14
Dependent Claim
43 words
Apparatus according to claim 11 in which the means for varying the contents of the look-up table includes means for re-locating the groups of m data bits held in the look-up table in response to the data bits output by the look-up table.
Claim 15
Dependent Claim
33 words
Apparatus according to claim 12 in which the means for re-locating includes means for exchanging the groups of m data bits held at one or more pairs of locations within the look-up table.
Claim 16
Dependent Claim
55 words
Apparatus according to any of claims 10 to 13 including means for applying the data bits output by the look-up table to the input of the look-up table so that the bits can be re-circulated through the look-up table one or more times prior to each change made to the contents of the look-up table.
Claim 17
Dependent Claim
30 words
Apparatus according to claim 10 including means for changing the order of the bits in the group of n data input bits prior to applying them to the look-up table.
Claim 18
Dependent Claim
18 words
Apparatus according to claim 15 in which the means for changing the said order is a bit-permutation matrix.
Claim 19
Dependent Claim
32 words
Apparatus according to claim 11 comprising a plurality of identical look-up tables each of which has locations addressable by a group of m data bits selected from the n data input bits.
Claim 20
Dependent Claim
66 words
In a method according to claim 1 wherein the improvement further comprises the steps of providing an inverse look-up table; applying n pre-transmission data bits to said inverse look-up table to provide n inverted pre-transmission data bits; transmitting said n inverted pre-transmission data bits through a data transmission link and applying said n transmitted data bits as the n data input bits in said converting method.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-06-25 | 1993-12-25 | 1994-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-06-25 | 1997-12-25 | 1998-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-06-25 | 2001-12-25 | 2002-06-26 | $7700.00 | Window Closed / Lapsed |