Coded data generation or conversion – Digital code to digital code converters – To or from run length limited codes
Reexamination Certificate
2000-04-21
2001-08-28
Young, Brian (Department: 2819)
Coded data generation or conversion
Digital code to digital code converters
To or from run length limited codes
C341S058000, C341S106000
Reexamination Certificate
active
06281815
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Applications Nos. 99-14284, 99-22574, and 99-42032, filed Apr. 21, Jun. 16, and Sep. 30, 1999, respectively, in the Korean Patent Office, the disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to modulation of m-bit information words into a signal and demodulation of the modulated signal, and more particularly, to a method of generating and allocating a (1, 8, 8, 12) code having effective DC suppression in a code word stream, a modulation and demodulation method, a demodulation apparatus therefor, in a run length limited (RLL) code to be used in optical disc recording and/or reproducing apparatuses which require particularly high density recording and/or reproducing.
2. Description of the Related Art
In optical recording and/or reproducing apparatuses, 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 disc and demodulating the signal reproduced from the optical disc into the original information. Types of optical discs currently in use include a compact disc (CD), and a digital versatile disc (DVD), and, at present, a high density disc (HD-DVD) which will have a higher density recording than that of the DVD is under development.
Among RLL codes which can be used in the HD-DVD, the characteristic of a (1, 7, 2, 3) code is the fact that its run length is restricted since the minimum run length is 2T(d=1), and the maximum run length is 8T(k=7). Its code rate R is R=m
=2/3. T is an interval between each bit in a code word.
As shown in
FIG. 1A
, 2 bits of data are converted into 3 channel bits. When the run length is violated , that is, when user data “00” is followed by user data “00” or “01”, or when user data “10” is followed by user data “00” or “01”, the channel bits are replaced by using the conversion table of FIG.
1
B.
Since a code word by itself cannot suppress the DC component of the code word in the conventional (1, 7, 2, 3) code, the variation of the Digital Sum Value (DSV) does not converge with DC value “0”, as shown in
FIG. 2
which illustrates the DSV variation curve of the (1, 7, 2, 3) code, when synchronization signals are not added. When this code is used in an optical disc system, a data slicer (also referred to as a data digitizing circuit) which converts a radio frequency signal picked up from the disc into a binary signal cannot properly operate. In addition, the lower frequency component of the code signal flows in a servo unit, which includes a tracking control unit and a focusing control unit, to create a bad influence, and lowers the reliability of the system.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a method of allocating an RLL code which is appropriate for a high-density disc system and is capable of effectual DC suppression in a code word stream.
It is another object of the present invention to provide a modulation method of modulating an RLL code which is capable of effectively suppressing DC in a code word stream.
It is still another object of the present invention to provide a modulation method using a code conversion table for DSV control at DSV control points, and otherwise using the main code conversion table.
It is still further another object of the present invention to provide a modulation method in which the number of code word bits is reduced by using some or all of the code words, already used in the main conversion table as code words of the code conversion table for DSV control for DC suppression.
It is still yet further another object of the present invention to provide a modulation method capable of effectively suppressing DC by using a sub conversion table for DSV control, which is separate from the main conversion table, the sub conversion table using to the maximum the sign of a code word sum value (CSV), which indicates the DC value within a code word, and the characteristic of an INV parameter, which predicts the transition of the DSV in the next code word.
It is still yet further another object of the present invention to provide a demodulation method capable of effectively suppressing DC in code word streams.
It is still yet further another object of the present invention to provide a demodulation method of demodulating code words of the conversion table for DSV control for DC suppression, which are modulated using some or all of the code words already used in the main conversion table.
It is still yet further another object of the present invention to provide a demodulation method of demodulating code words modulated using the sub conversion table for DSV control, which is separate from the main conversion table, the sub conversion table using to the maximum the characteristics of the code words of the main conversion table, that is the characteristics of a code word sum value (CSV) and an INV parameter.
It is still yet further another objective of the present invention to provide a demodulation apparatus for demodulating the RLL code appropriate for a high density disc system.
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 and other objects of the present invention, there is provided an allocating method of allocating code groups grouped by the characteristics of code words after generating a run length limited (RLL) code which is represented by (d, k, m, n), in which d means the minimum run length, k means the maximum run length, m means the length of data bits, and n means the length of code word bits, the allocating method comprising allocating a pair of code groups for controlling direct current (DC) suppression in a code word stream; and allocating code words to the pair of code groups, the code words corresponding to the same source code, in order that the corresponding code words of each of the code groups have opposite signs of a 1
st
parameter, a code word sum value (CSV), which represents the DC value in a code word and opposite characteristics of a 2
nd
parameter INV which predicts the transition direction of the digital sum value (DSV) of the succeeding code word.
To accomplish the above and other objects of the present invention, there is provided a modulation method of modulating data input to optical disc recording/reproducing apparatuses to a run length limited (RLL) code which are represented by (d, k, m, n) in which d means the minimum run length, k means the maximum run length, m means the length of data bits, and n means the length of code word bits, the modulation method comprising (a) at a point of DSV control, modulating m-bit data input while inserting a code word for DSV control, and otherwise, modulating m-bit data input while selecting a code word of one code group in main code groups, in which code words have duplicated code words and code words of each code group are allocated to have the opposite signs of a 1
st
parameter code word sum value (CSV) which represents direct current (DC) value in a code word and the opposite characteristics of a 2
nd
parameter (INV) which predicts the transition direction of a digital sum value (DSV) of the succeeding code word, and decision code groups for determining whether a code word is the duplicated code word.
To accomplish the above and other objects of the present invention, there is provided a demodulation method of demodulating a code word stream received in optical disc recording/reproducing apparatuses using a Run Length Limited (RLL) code into original data, in which at a point of DSV control, m-bit input data is modulated to a code word for DSV control, and when it is not at a point of DSV control, m-bit input data is modulated to a code word in one code group among main code groups and decision
Ko Jung-wan
Shim Jae-seong
Won Yong-kwang
Nguyen John B
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
Young Brian
LandOfFree
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