Coded data generation or conversion – Digital code to digital code converters – To or from run length limited codes
Reexamination Certificate
2000-03-09
2001-07-31
Tokar, Michael (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
To or from run length limited codes
C341S079000, C341S058000, C341S106000
Reexamination Certificate
active
06268810
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 99-7723, filed Mar. 9, 1999, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to modulation of a series of m-bit information words into a modulated signal and demodulation of the modulated signal, and more particularly, to a method of generating a run length limited (RLL) code which uses the less number of bits for a code word and efficiently suppresses the DC component of a code word stream, and a method of modulating/demodulating the RLL code for use in optical recording and/or reproducing devices requiring high density recording and/or reproducing.
2. Description of the Related Art
In optical recording and/or reproducing devices, a run length limited (RLL) code represented by (d, k, m, n) is widely used for modulating original information into a signal appropriate for an optical disk and demodulating the signal reproduced from the optical disk into the original information.
In the RLL code represented by (d, k, m, n), main conversion of data is carried out using the main conversion table of FIG.
1
A. The code groups 1 and 4 in the main and sub conversion tables of
FIGS. 1A and 1B
are divided by the number of lead zeros (LZ), while the code groups 2 and 3 are also exclusively divided by referring to a predetermined bit of the code word and determining whether the bit is “0”, or “1”. That is, no code words in the code groups 1 and 4 are the same, and no code words in the code groups 2 and 3 are the same. The main and sub conversion tables of
FIGS. 1A and 1B
are suggested in U.S. Pat. No. 5,790,056, “Method of converting a series of m-bit information words to a modulated signal, method of producing a record carrier, coding device, device, recording device, signal, as well as a recorded carrier.”
The RLL code uses a (d, k)-constraint method in which code words of a code group select a next code group in compliance with the (d, k) constraint. Using the sub conversion table of
FIG. 1B
, suppression of the DC component in a code word stream can be carried out when data less than or equal to 87 is input. The code words of the code groups in the sub conversion table are allocated by using code words not included in the main conversion table, each of the code words of the code groups in the sub conversion table having a code word sum value (CSV), a parameter representing the direct current (DC) value in a code word, which is opposite in sign to CSVs of corresponding code words having the same decoded value in the main conversion table, in order to suppress the DC component.
In the code groups 1 and 4 in the main conversion table and the sub conversion table of
FIGS. 1A and 1B
, a code group advantageous to suppression of the DC component can be selected if the (d, k) constraint of the run length is not violated. However, the code words are allocated without considering the CSV signs of code words which are included in the code groups 1 and 4 and the characteristics of an INV parameter, proposed by the present invention, which predicts the transition direction of a next code word by determining whether the number of “1”s in a code word is an odd number or an even number. Therefore, it is not appropriate to generate a code conversion table to convert an 8-bit information word into a 15-bit code word, separately from the conventional code (2, 10, 8, 16) of
FIGS. 1A and 1B
, which converts an 8-bit information word into a 16-bit code word.
In addition, for data less than or equal to 87, a code word can be selected from both the main conversion table and the sub conversion table in order that their CSV signs are opposite, so that the DC component can be suppressed. However, because the code words of the sub conversion table are newly allocated code words which are not included in the main conversion table, as much code words as the code words in the sub conversion table are additionally required after all, which imposes a limitation in reducing the number of bits of a code word.
Also, the code words in the sub conversion table are allocated to have opposite signs to those of corresponding code words having the same decoded value in the main conversion table, but the characteristics of INV which is a code word parameter proposed by the present invention are not considered for allocation, which causes a problem in that the possibility of DC suppression cannot be maximized when a modulated code with a smaller number of code words is used in DSV control which is carried out in a predetermined look-ahead method.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a method of generating an RLL code capable of efficient DC suppression of a code word stream, in which method code words having a smaller number of bits are delivered, by generating a main conversion table using the maximum CSV and INV which are the code word characteristic parameters of the main conversion table while using some of the code words already used in the main conversion table as code words for a sub conversion table for DC suppression.
It is another object to provide a modulation method of modulating the RLL code having an improved DC suppression capability.
It is still another object to provide a demodulation method of demodulating a modulated code word stream using the RLL code having an improved DC suppression capability.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To accomplish the above object and other objects of the present invention, there is provided a method of generating a run length limited (RLL) code which is represented by (d, k, m, n), in which d, k, m, and n denote the minimum run length, the maximum run length, the length of data bits, and the length of code word bits, respectively, the method comprising (a) generating a code word which satisfies the (d, k) run length constraint; and (b) allocating main code groups, in which a code word can be duplicated and allocated in a main code group depending on the characteristics of the generated code word, and code words of each main code group are allocated in consideration of a code word sum value (CSV) parameter, which represents the direct current (DC) value in a code word, and the characteristic of an INV parameter, which predicts the transition direction of a digital sum value (DSV) of a next code word, and allocating decision code groups for differentiating duplicated code words.
To accomplish another object and other objects of the present invention, there is provided a method of modulating data input to optical disc recording and/or reproducing devices into a run length limited (RLL) code which is represented by (d, k, m, n), in which d, k, m, and n denote the minium run length, the maximum run length, the length of data bits, and the length of code word bits, respectively, the modulating method comprising (a) modulating m-bit input data into a code word after selecting the code word in a code group among main code groups in which a code word can be duplicated and code words of each main code group are allocated in consideration of code word sum value (CSV) parameter which represents the direct current (DC) value in a code word and the characteristic of an INV parameter which predicts the transition direction of a digital sum value (DSV) of a next code word, and decision code groups for differentiating the duplicated code words.
To accomplish still another object and other objects of the present invention, there is provided a method of demodulating a run length limited (RLL) code into original data, the RLL code which is represented by (d, k, m, n) in which d, k, m, and n denote the minium run length, the maximum run length, the length of data bits, and the length of code word bits, respectively, in which t
Shim Jae-seong
Won Yong-kwang
Nguyen John
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
Tokar Michael
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