Modulating apparatus and method, demodulating apparatus and...

Details Modulating apparatus and method, demodulating apparatus and... Modulating apparatus and method, demodulating apparatus and...

1998-11-06

2002-04-09

Decady, Albert (Department: 2133)

Coded data generation or conversion

Digital code to digital code converters

To or from run length limited codes

C341S067000, C714S779000

Reexamination Certificate

active

06369724

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a modulating apparatus and method, demodulating apparatus and method, and a transmission medium and in particular to a modulating apparatus and method, demodulating apparatus and method, and a transmission medium which are suitable for modulating data for data transmission or recording on a recording medium, and demodulating the modulated code obtained by this modulation so as to reproduce the data.
2. Description of the Related Art
This block coding converts a data sequence to blocks of m×i bit units (referred to hereafter as data words), and this data word is converted to a code word comprising n×i bits according to a suitable code rule. When i=1, this code word is a fixed length code. A plurality of values for i can be selected. Thus, a predetermined i may be selected from the range of 1 to imax (maximum of i). The selected value is indicative of a variable length code. This block encoded code is represented by a variable length code (d, k; m, n; r).
Here, i is known as a restriction length, and imax is r (the maximum restriction length). The minimum run d shows the minimum number of consecutive “0”s in repeated “1”s in a code sequence. The maximum run k shows the maximum number of consecutive “0”s in repeated “1”s in a code sequence.
In compact discs or mini-discs (trademark) etc., NRZI (Non Return to Zero Inverted) modulation, wherein “1” means inversion and “0” means non-inversion, is performed on the variable length code obtained above. The NRZI modulated variable length code (hereafter, referred to as a recorded waveform sequence) is then recorded.
Various modulation techniques have been proposed. If the minimum inversion interval of the recorded waveform sequence is Tmin, and the maximum inversion interval is Tmax, to record at a high density in a linear velocity direction, the minimum inversion interval Tmin should be long, that is, the minimum run d should be large. From the clock reproduction aspect, moreover, the maximum inversion interval Tmax should be short, that is, the maximum run k should be small.
For example, one modulation technique used by magnetic disks or magneto-optical disks, etc., is RLL(1-7) code. The parameters of this modulating technique are (1, 7; 2, 3; 2). The minimum inversion interval Tmin is 2(=1+1)T(=(2/3)×2 Tdata=1.33 Tdata). The maximum inversion interval Tmax is 8(=7+1) (=(2/3)×8 Tdata=5.33 Tdata). In addition, a detection window width Tw is 0.67(=2/3) Tdata. For example, the variable length conversion table for the RLL(1-7) code is as follow.
TABLE 1
RLL (1, 7; 2, 3; 2)
Data
Code
i = 1
1 1
0 0 x
1 0
0 1 0
0 1
1 0 x
i = 2
0 0 1 1
0 0 0  0 0 x
0 0 1 0
0 0 0  0 1 0
0 0 0 1
1 0 0  0 0 x
0 0 0 0
1 0 0  0 1 0
The symbol x in the conversion table is 1 when the next channel bit is 0, and 0 when the next channel bit is 1 (this is also true in the following explanation).
The table 2 is a demodulation table of Table 1 of the RLL (1-7) code.
TABLE 2
DEM-RLL (1, 7; 2, 3; 2)
Demodulated
Code sequence
data sequence
i = 1
0 0 1
1 1
0 0 0 1
1 1
0 1 0
1 0
1 0 1
0 1
1 0 0 1
0 1
i = 2
0 0 0  0 0 -
0 0 1 1
0 0 0  0 1 -
0 0 1 0
1 0 0  0 0 1
0 0 0 1
1 0 0  0 0 0 1
0 0 0 1
1 0 0  0 1 -
0 0 0 0
In this table, a hyphen (-) means a desired bit (
1
or
0
, as desired)(this is also true in the following explanation)
In the Table 2, the third code sequence “100 001” and the fourth code sequence “100 0001” of i=2 are combined to obtain “100 00-” for the demodulation. However, in this case, worst error propagation during the bit shift error is 6 bits and the worst error propagation during the bit shift error is 5 bits according to Table 2.
However, the RLL(1-7) code can also be produced from the fixed length code. Parameters of the fixed length RLL (
107
) code is (1, 7; 2, 3; 1) and the minimum inversion interval Tmin becomes 2(=1+1)T when the bit interval of the recording waveform sequence is T. Thereby, the minimum inversion interval Tmin becomes 1.33 (=(2/3)×2) Tdata when the bit interval of data sequence is assumed as Tdata. Moreover, the maximum inversion interval Tmax is 8T(5.33Tdata). In addition, the detection window width Tw is expressed by (m
)×T and its value is 0.67 (=2/3)T. Table 3 shows the table of the fixed length RLL (1-7) code. This table is the ISO standard table. An example of the demodulation table of Table 3 is shown in Table 4.
TABLE 3
F-RLL (1, 7; 2, 3; 1)
Immediately
Current
Next
preceding
data
data
Converted
code word
word
word
code word
x
0 0
0 x
0 0 1
0
0 0
1 x
0 0 0
1
0 0
1 x
0 1 0
0
0 1
0 x
0 0 1
0
0 1
1 x
0 0 0
1
0 1
0 0
0 1 0
1
0 1
not 0 0
0 0 0
0
1 0
0 x
1 0 1
0
1 0
1 x
0 1 0
0
1 1
0 0
0 1 0
0
1 1
not 0 0
1 0 0
TABLE 4
DEM-F-RLL (1, 7; 2, 3; 1)
Immediately
Current
Next
preceding
code
code
Converted
code word
word
word
data word
x 1 0
0 0 0
x x x
0 0
not x 1 0
0 0 0
x x x
0 1
x 0 O
0 0 1
x x x
0 1
not x 0 0
0 0 1
x x x
0 0
x x 0
0 1 0
0 0 x
1 1
x x 0
0 1 0
not 0 0 x
1 0
x x 1
0 1 0
0 0 x
0 1
x x 1
0 1 0
not 0 0 x
0 0
x x x
1 0 0
x x x
1 1
x x x
1 0 1
x x x
1 0
In this table not x
00
means any code word of x
11
, x
10
, x
01
, while not x
10
means any code word of x
11
, x
01
, x
00
and not
00
x means any code word of 1x, 10x, 01x (this is also true in the following explanation).
This RLL(1-7) code enables replacement of the data words to be converted as shown in Table 5. In this case, the demodulation can be realized on the 1:1 basis as in the case of the Table 3. An example of the demodulation table of table 5 is shown in Table 6.
TABLE 5
F-RLL (1, 7; 2, 3; 1)
Immediately
Current
Next
preceding
data
data
Converted
code word
word
word
code word
0
0 0
1 1
0 1 0
0
0 0
not 1 1
1 0 0
0
0 1
0 x
0 1 0
0
0 1
1 x
1 0 1
0
1 0
0 x
0 0 0
0
1 0
1 x
0 0 1
1
1 0
1 1
0 1 0
1
1 0
not 1 1
0 0 0
0
1 1
0 x
0 0 0
1
1 1
0 x
0 1 0
x
1 1
1 x
0 0 1
In this table, not
11
means any data word of 00, 01, 10 (this is also true in the following explanation).
TABLE 6
DEM-F-RLL (1, 7; 2, 3; 1)
Immediately
Current
Next
preceding
code
code
Converted
code word
word
word
data word
x 1 0
0 0 0
x x x
1 1
not x 1 0
0 0 0
x x x
1 0
x 0 0
0 0 1
x x x
1 0
not x 0 0
0 0 1
x x x
1 1
x x 1
0 1 0
0 0 x
1 0
x x 1
0 1 0
not 0 0 x
1 1
x x 0
0 1 0
0 0 x
0 0
x x 0
0 1 0
not 0 0 x
0 1
x x x
1 0 0
x x x
0 0
x x x
1 0 1
x x x
0 1
When the code limiting the repetition of the minimum run is given to the above variable length RLL (1-7) code as indicated below. Here, the table adding the code to control the minimum run sequence is called the RML (Repeated Minimum run-length Limited Code). The RML (1-7) code shown in Table 7 is generated for the Table 1. An example of the conversion table of Table 7 is shown in Table 8.
TABLE 7
RML (1, 7; 2, 3; 3)
Data
Code
i = 1
1 1
0 0 x
1 0
0 1 0
0 1
1 0 x
i = 2
0 0 1 1
0 0 0 0 0 x
0 0 1 0
0 0 0 0 1 0
0 0 0 1
1 0 0 0 0 x
0 0 0 0
1 0 0 0 1 0
i = 3
1 0 0 1 1 0
1 0 0 0 0 0 0 1 0
“x” in the table 7 is determined by a complementary number of the sequential code bits. In this case, the minimum run is repeated up to five times.
TABLE 8
DEM-RML (1, 7; 2, 3; 3)
Demodulated
Code sequence
data sequence
i = 1
0 0 1
1 1
0 0 0 1
1 1
0 1 0
1 0
1 0 1
0 1
1 0 0 1
0 1
i = 2
0 0 0  0 0 -
0 0 1 1
0 0 0  0 1 -
0 0 1 0
1 0 0  0 0 1
0 0 0 1
1 0 0  0 0 0 1
0 0 0 1
1 0 0  0 1 -
0 0 0 0
i = 3
1 0 0  0 0 0  0 1 -
1 0 0 1 1
Similarly, when the code limiting the repetition of the minimum run can be added as follow to the fixed length RLL (1-7) code. The RML (1-7) code of Table 9 is generated to Table 3 and the RML (1-7) code of Table 11 is generated to Table 5. An example of the conversion table of Table 9 becomes as Table 10, while the conversion table of Table 11 becomes as Table 12. Moreover, the maximum restriction length in Table 10 and Table 12 is 1 or 3.
TABLE 9
F-RML (1, 7; 2, 3; -)
Immediately
Current
N

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