KR20020077574A - Method and apparatus of converting a series of data words into a modulated signal - Google Patents

Abstract

PURPOSE: A method and an apparatus for converting sequence data words into modulation signals are provided to further simplify a hardware capable of recording data codes, which suppress a direct current component with abiding by a previously defined (d,k) code regulation, have strings of '0' not to be long and have a minimum d run length not to be long, on an information recording medium such as an optical or an optical-magnetic disk. CONSTITUTION: A method for converting sequence data words into modulation signals includes the steps of: making the number of scrambled sequences to be less than 2¬r by scrambling a plurality of intermediate sequences by appending r bits of digital words different from each other to inputted data words, modulating the scrambled intermediate sequences into sequences matching with the (d,k) condition in proportion of the preset m/n coding rate and selecting one sequence matching with one (d,k) condition among the sequences matched with the modulated (d,k) conditions in response to the result obtained by measuring the contained degree of undesired sub sequences.

Description

Method and apparatus of converting a series of data words into a modulated signal

The present invention relates to a data modulation method for suppressing a DC component while complying with a preset (d, k) code regulation.

Run length restriction codes, generally denoted as (d, k) codes, have been widely and successfully applied to modern magnetic and optical recording systems. The codes and means for implementing the codes are , Codes for Mass Data Storage Systems "(ISBN 90-74249-23-X, 1999), described in detail by KA Schouhamer Immink.

The runlength restriction code is an extension of the initial non return to zero (NRZ) code, where zeros written in binary indicate no (magnetic flux) change in the recording medium, whereas binary 1 ( Ones indicate that the magnetic flux has shifted from one direction to the other in the recording medium.

In the above (d, k) code, in addition to the above-described recording rule, at least '0' must be added between d consecutive data '1' by 'd', and '0' between consecutive data '1'. There is an additional condition that at least d must exist and k must not exceed. The first condition is for eliminating interference between symbols generated by a group of pulses to be reproduced when a series of '1's are continuously recorded. The second condition is for reproducing data by locking the PLL to the transition of the reproduction signal. To recover the clock from.

If the string of consecutive '0's in which' 1 'is not interleaved is too long, the clock reproduction PLL is out of sync.

For example, the (1,7) code must have at least one '0' between the '1's recorded and no more than seven consecutive' 0s' between the '1s' recorded. do. A series of encoded bit strings is converted into a modulated signal consisting of bit cells having a high or low signal value through modulo-2 integration, in which the modulated signal is converted. Bit '1' represents a change from high to low, or vice versa, and bit '0' represents no change in the modulation signal.

In addition, the minimum inversion time Tmin, which can be expressed as (d + 1) T, is equal to 2T corresponding to two times T of a one-bit time interval in the recording waveform, and can be represented by (k + 1) T. The maximum inversion time Tmax is equal to 8T corresponding to eight times the bit time interval T.

On the other hand, in the channel bit string generated by the (1,7) code, the minimum inversion time Tmin appears more frequently than the inversion times such as 3T and 4T. Many edge information appearing at short intervals, such as 2T and 3T, is advantageous for the generation of the clock signal in many cases.

However, as the recording density of the recording medium increases, the minimum inversion time Tmin becomes a problem, which is that if the minimum length of 2T is continuously generated in the recording waveform, the waveform is more likely to be distorted. to be. This is because the output size of the 2T waveform is relatively smaller than the output size of other waveforms, which is easily influenced by factors such as defocus and horizontal tilt.

Furthermore, when the minimum mark 2T is continuously recorded at a high linear density, the disturbances such as noise are more easily affected, so that errors are easily generated even in the data reproduction operation.

In such a case, since the error pattern in data reproduction appears in many cases as the front and rear ends of the minimum mark edge Edge are shifted, the length of the bit error is increased.

When data is transmitted through the transmission line or recorded on the recording medium, as described above, the data is modulated into a code sequence suitable for the transmission line or the recording medium before transmission or recording. If a DC component is included in the modulated code sequence, various error signals such as tracking errors generated in the servo control of the disk driver may be shifted or jitter may be easily generated.

Therefore, a signal without direct current component should be used because the first reason is that the recording channels typically do not respond to low frequency components. Suppressing low frequency components in a signal is an optical recording in which the signal is recorded in a track. This works very advantageously when reading signals from the medium, as it allows the continuous tracking control to be unobstructed by the recording signal.

And, by sufficiently suppressing low frequency components, it is possible to perform improved tracking in which audible noise is reduced. For these various reasons, it is desirable to make a lot of effort to ensure that the modulated sequence does not contain direct current components as much as possible.

As a method for preventing the DC component from being included in the modulated sequence, a DSV (Digital Sum Value) control method has already been proposed. The DSV is the total value obtained by adding the bit string value to the bit string as a result of NRZI modulation of the channel bit string, with 1 assigned to +1 and 0 assigned to 1, the direct current contained in one sequence column. It is an indicator representing a component.

If the value for which you are calculating the DSV is virtually constant, it means that the low frequency component is not included in the frequency spectrum of the signal. DSV control is generally not applied to sequences generated by standard (d, k) codes. DSV control for the standard (d, k) code is achieved by calculating the DSV of the encoded bit string after being modulated for a set time and inserting a preset number of DSV control bits into the encoded bit string. At this time, in order to improve the code efficiency, it is preferable to select the number of the DSV control bits as small as possible.

Advantageously, the encoded signal comprises a sequence of q codewords, and inserts a synchronization signal between the encoded signal portions, wherein the synchronization signal should not be generated within the sequence of encoded signals. do.

Typically, the sync pattern consists of two bits of k bits whose logical '0' contains bits contiguous by s greater than k, or divided by logical '1'. That is, it has two consecutive K length '0' sequences.

On the other hand, the use of such a sync pattern has a disadvantage in that the signal length becomes relatively long and the recording efficiency is lowered. Therefore, it is preferable to use a short sync pattern in which '0' includes two or more consecutive sequences. Do.

An example of using such a signal for recording and reading to an optical or magneto-optical recording medium is described in US Pat. No. 4,501,000, which describes an EFM (Eight to Fourteen Modulation) modulation scheme for recording information on a CD or MD. The EFM modulated signal is obtained by modulating an 8-bit information word into a 14-bit codeword. Three consecutive merging words are inserted between consecutive codewords.

Each 14 bit codeword is between two consecutive '1's. At least two (d = 2) and at least ten (k = 10) '0's must be satisfied. To satisfy this condition, three bit merging words are used between the codewords. do.

The 3-bit merging word will use only four 3-bit merging words, 001,010,000,100, out of the eight possible (= 2 ³ ) merging words, which is the remaining four 3-bit merging words "111", "011". This is because "101" and "110" violate the condition of d = 2.

In the four available merging words, a bit string obtained by concatenating several selectable codewords and merging words satisfies the condition (d, k), and in the corresponding modulo 2 integral signal, the value of DSV is In fact, one is selected that allows the constant to be maintained. When the merging word is selected in this manner, it is possible to minimize the low frequency components in the modulated signal.

On the other hand, the 3-bit merging word selection is selected based on the condition that the channel signal (d, k) must be satisfied without the direct current component present in the channel signal, and the decoding of the EFM signal is very simple. Do. The sync pattern is multiplexed between 33 17-bit strings (3-bit merging word and 14-bit codeword). The 27-bit sync pattern used for the CD format includes 10 consecutive ' It consists of two bit strings of 0's.

The selection of the merging word prevents the synchronization pattern from occurring in the output sequence. In the above recording format, the frequency of the relative synchronization pattern is 4.6% since it is 27 bits out of a total of 588 bits. The decoder ignores the 3-bit merging word and converts the 14-bit codeword into an 8-bit information byte by using a look-up table or a programmable logic array (PLA).

Information recording has a constant need for reading and increasing the speed of writing. However, in order to increase the recording speed, a high servo band width of the tracking mechanism is required, which in turn requires satisfying more stringent restrictions that the low frequency component of the recording signal should be limited.

Improvements to suppressing low frequency components also have the advantage of reducing the generation of audible noise from the tracking mechanisms, and therefore, research and development are required to ensure that the modulated signal does not contain low frequency components.

The present invention suppresses direct current components in recording data while complying with a preset (d, k) code regulation, and records a data code of a sequence in which the string of '0's is not long and the minimum d run length is not long. To provide a coding system to

Another object of the present invention is to provide a method for converting a series of data words into modulated signals, which enables DSV control using simpler hardware.

1 shows a block diagram of an embodiment of a coding system according to the present invention,

FIG. 2 illustrates a schematic diagram of some embodiments of a coding structure that performs scrambling and augmenting of a digital word.

3 illustrates a configuration of a selector used in a coding system according to the present invention.

4 shows a block diagram for explaining a method for determining a selectable sequence;

5 illustrates an embodiment of a method of dividing a data word and using it as an input data word according to the present invention.

6A and 6B are graphs obtained by experimentally obtaining a relationship between the number of intermediate sequences to be generated and the low frequency characteristics of a recording signal.

7 shows the configuration of a demodulation device for demodulating a recorded sequence into data words according to the present invention.

※ Explanation of code for main part of drawing

40: Augmentor 42: Scrambler

50: Encoder 52: Judge

54: selector 101: synchronous detector

102 Decoder 103 Descrambler

104: remover

The method for converting a series of data words into a modulated signal according to the present invention for achieving the above object, generates a plurality of intermediate sequences by adding a different digital word of r-bit to the input data word, Scrambled, wherein the number of scrambled sequences is less than 2 ^r ; Modulating the plurality of scrambled intermediate sequences into a sequence meeting a condition (d, k) according to a preset m / n coding ratio; And measuring the inclusion of an undesirable subsequence in the modulated (d, k) condition matching sequences and selecting one (d, k) condition matching sequence accordingly. do.

1 shows a block diagram of an encoding system according to an embodiment of the present invention, wherein the coding system uses a generator 20 and a selector 22 to generate user data 19, (d, k Is converted into a sequence 23 that satisfies the condition. At this time, a plurality of sub-sequences (Sub Sequence) defined in advance are completely excluded or have a low probability in the converted sequence 23. The (d, k) conditionalized sequence is converted into a run length limited sequence 25 in which low frequency components are suppressed by the precoder 24.

As shown in FIG. 1, the coding system has a generator 20 having a detailed block shown in FIG. 2. The generator 20 includes the data word for each data word 19. An augmentor 40 is included that generates multiple intermediate sequences 41 by combining different digital words together. The intermediate sequence 41 is simply created by placing a digital word in front of the data word 19.

The digital word can also be placed after or in the middle of the data word.

The generator 20 also includes a scrambler 42 that alternately scrambles the intermediate sequence 41 to form a select set of various selectable sequences 21. The inclusion of different digital words in the intermediate sequence 41 preferably has the effect that the self-synchronized scrambler 42 is initialized by each intermediate sequence 41 having a different digital word. Therefore, the selection sequence 21 becomes data having relatively good randomness with respect to one data word 19.

Preferably, the augmenter 40 generates, for each data word 19, two ^r intermediate sequences 41 by combining all possible digital words of length r to the data word 19. In this way, the selection set of selection sequences 21 results in optimal randomization.

3 shows a detailed configuration of the selector 22. The selector 22 comprises a (d, k) encoder 50, which (d, k) encoder 50 assigns each selection sequence 21 to the (d, k) condition matching sequence 51. To. To this end, the selection sequence 21 is partitioned into q m bit length words, which are converted into q n bit length words by the (d, k) encoder. Where n is greater than m and the (d, k) encoder 50 has parameters m = 2, n = 3, d = 1, k = 7, otherwise m = 1, n = 2, d = 2, k Can be a standard type with = 7.

Preferably, in order to increase the encoding efficiency, the encoder 50 is m = 9, n = 13, d = 1 or m = 11, n = 16, d = 1, or m = 13, n = 19, d It may have a parameter defined as = 1, the content of which is described in the unpublished PCT application number PCT / KR00 / 01292 (US application Ser. No. 09 / 707,947). In addition, the encoder 50 may have parameters defined as m = 6, n = 11, d = 2 or m = 11, n = 20, d = 2 or m = 7, n = 13, d = 2. This is also described in PCT application number PCT / KR01 / 00359, which has not yet been published.

In the selector 22, for each of the selectable (d, k) conditional matching sequences 51, a run pattern of a synchronization pattern, a long string of '0's, or an alternating Tmin is set to a long string. Means 52 are included for determining if the same unwanted subsequence is included, and if such an unwanted subsequence is detected, the judging circuit is associated with the corresponding undesired subsequence. Penalties, or deductions, are calculated.

The selector 22 also contains, for each selectable (d, k) conditional matching sequence 51, an undesired negative, such as a sync pattern, a string with long '0's, or a string with a long run of variation Tmin. Means 52 for determining the frequency of the sequence and the degree to which the selected sequence 21 contributes to the low frequency component are included.

According to the penalty algorithm rule, the judging means 52 gives low points for the preferred sequence, high points for the undesired sequence, and the selector 22 has the lowest (d, k) condition. Means 54 for selecting a matching sequence are also included.

Fig. 4 shows a block diagram for explaining a general method used for determining and selecting the lowest deductible selectable (d, k) conditional matching sequence 51 according to the present invention. Reference numeral 52 includes a plurality of calculators, each calculator comprising a '0' run length determination 60, a generation of a preset synchronization pattern 62, a variable Tmin run length 64, and a low frequency content. Each of 66 is measured in parallel.

The '0' runlength is used as a measure of successive '0's (generally referred to as' 0' runlengths) that are detected within one selectable (d, k) condition matching sequence 51. As described above, if a '0' continues in the sequence for a long period of time, recording characteristics such as Pit and Land become very long, which leads to a defect that frequently causes tracking errors and errors. Deduct penalty according to '0' run length.

The Tmin calculator 64 measures the number of run lengths of consecutive Tmins, and the synchronization calculator 62 determines whether there is a predetermined synchronization pattern in the selectable (d, k) condition matching sequence 51. When the sync pattern is actually detected, the sync calculator 12 displays a flag for identifying it in the (d, k) condition sequence, and in the opposite case, does not display the flag.

In addition, the calculator 66 measures the low frequency content of the selectable (d, k) conditional matching sequence 51, and in a preferred embodiment of the present invention the calculator 66 is pre-coded. The device modulates the selectable (d, k) conditional matching sequence 51 and then measures the DSV of the sequence. In this case, preferably, when the sequence becomes a relatively long sequence exceeding 100 bits, the dispersion of the DSV, which is a more suitable measurement method, is measured.

Thereafter, several measured values measured as described above and a flag displayed by the synchronization detection are input to the determination means 52. The selecting means 54 determines the last sequence to be selected and recorded based on the weights associated with the input several measurements. At this time, the sequence having the flag set by the determination means 52 of the front end is excluded from the selection and one is selected from the remaining (d, k) condition matching sequences.

In addition, a synchronous pattern composed of '0' runs shorter than k in a preferred embodiment of the present invention may be used. As a result, an advantage of coding efficiency due to a relatively short synchronization pattern can be obtained.

The (d, k) condition matching sequence 51 selected by the selection means 54 is converted into a modulated signal through an NRZI precoding process, which is shifted at '1' and '0'. Is generated from the selected (d, k) conditional matching sequence integrated into two modules with no transitions, and then recorded on the recording medium by conventional recording methods.

Meanwhile, a method of selecting the length of the r bits added by the augmenter 40 according to the preferred embodiment of the present invention will be described.

The number of bits of r is one of a value in which the value A + r obtained by adding r to the number of bits A of the data word 19 input to the encoder 21 is a multiple of m. Is determined by selecting.

For example, in the coding ratio m / n = 9/13 modulation, if A is 728, r satisfying the above condition may be determined to be 1, 10, 19,. Bit number 728 of the data word shows an example in which one sync frame corresponds to 91 user bytes when using the existing DVD ECC block.

However, if the number of r bits in the augmenter 40 is selected as 1, the number of digital words that can be added to the input data word 19 is two (21). Since only the dogs are present, there may be a case in which the selection means 54 at a later stage fails to obtain the desired (d, k) conditional matching sequence 51.

Therefore, if the number of r bits is determined to be 10 bits, since there are 1024 (210) kinds of intermediate sequences 41, the desired (d, k) condition matching sequence 51 can be selected through sufficient randomization.

Alternatively, as shown in FIG. 56, the 728-bit input data word is divided into two and divided into two, and the data word 19 having a 364-bit size is sequentially input to the audator 40. do. To this end, dividing means for dividing an input data word of 728 bits and sequentially inputting the input data word to the augmenter 40 is required. Then, the augmenter 40 adds 5 (= r) bits of digital words to the 364 bit data word 19 so that 25 (= 32) different intermediate sequences 41 are generated. It is generated and output in parallel from each register.

If, in the coding ratio m / n = 6/11 modulation, A is 728, r may be selected from 4, 10, 16, etc., but the preferred value is 4 as well. If r is 4, 16 (24) intermediate sequences 41 are generated, so that a certain amount of randomization can be obtained, and the required number of registers is also appropriate.

As another example, 728 bits may be divided into eight bits each of 91 bits and sequentially input to the augmentor 40. In this case, 96 bits are a multiple of 6 since 5 different digital words are added to each 91-bit data word 19.

When the size of the input data word 19 is large, it is preferable that the number of bits of the added digital word increases in proportion. On the contrary, if the size of the input data word 19 is small, the number of bits of the digital word can be made smaller than five.

Fig. 6A shows the low frequency of the signal when the number of bits (r = 5) of the added digital word is 5, d = 1 and the coding ratio (m / n) is 9/13 by dividing the input data word. The characteristics were obtained experimentally, which is a case of employing the modulation method described in the prior application PCT / KR00 / 01292.

The lower the 'H' value, the better the low frequency characteristics. FIG. 6A shows that the k condition must be 10 or more in order to have a better characteristic than 25 dB used as a standard ('X1' region). And even if the number of bits r of the actual digital word is selected as 5, the number of scrambles for the actual intermediate sequence may be made smaller than this. The x-axis of FIG. 6A shows the number of scrambles as a variable to know the low frequency characteristics when the generator 20 and the selector 22 are configured with fewer registers than 32 (= 2 ^r ) when r = 5. It is.

In the 'Y1' area of the experimental result graph of FIG. 6A, under the conditions for obtaining low frequency characteristics better than -25 dB, the number of scrambles is 32 to approximately 15 when k = 14 and about 17 when k = 12. It can be seen that when k = 11, the number can be reduced to about 21. Therefore, select only as many numbers as necessary from the maximum number of digital words (= 2 ^r ) that can be added by the value of ^r , and generate as many intermediate sequences 41 therefrom or the middle of 2 ^r generated. Any number of hardware configurations are possible to select as many as necessary in sequence 41 to produce scrambled sequence 21.

This means that the number of scramble sets that can be generated can be reduced, which means that when the registers are parallelized, the complexity of the hardware can be reduced by reducing the number of registers. When the registers are serialized, the processing speed can be increased. it means.

Fig. 6B shows the low frequency of the signal when the number of bits (r = 5) of the added digital words is 5, d = 2 and the coding ratio (m / n) is 6/11 by dividing the input data word. It is a case where the modulation method described in the original application PCT / KR01 / 00359 is adopted as what was obtained experimentally.

In this case, it is shown that the k condition to have better characteristics than 25 dB used as a standard is 13 or more ('X2' region). In the 'Y2' area of the graph, under the conditions for obtaining low frequency characteristics better than -25dB, the number of scramblers from 32 to about 22 at k = 15, and up to about 25 at k = 14, It can be seen that when k = 13, the number can be reduced to about 27.

On the other hand, the data modulated and recorded as described above is performed by a demodulation device which performs the above-described method in reverse, that is, sequentially performs decoding, de-scrambling, and r-bit digital word removal. Can be restored to the original input data word.

A configuration diagram thereof is shown in FIG. 7. In FIG. 7, the sync detector 101 detects and excludes a sync signal added to a sequence (frame size: (A + r) * m / n bits + sync bits) reproduced from a recording medium (d, k) The conditional reproduction sequence 23 (frame size: (A + r) * m / n bits) is applied to the decoder 102. The decoder 102 outputs a frame of (A + r) bits by performing n / m demodulation which inversely modulates m / n. The descrambler 103 restores a frame of (A + r) bits to a sequence before scrambling, and the augment remover 104 removes r bits of digital words inserted at the front, rear, or middle of the descrambled sequence. This outputs the original data word 19 (A bit) before writing.

As mentioned above, preferred embodiments of the present invention are disclosed for the purpose of illustration, and those skilled in the art can improve and change various other embodiments within the spirit and technical scope of the present invention disclosed in the appended claims below. , Replacement or addition would be possible.

The method and apparatus for converting a series of data words according to the present invention as described above into a modulated signal suppresses direct current components while complying with a pre-defined (d, k) code regulation, and whether the string of '0's is long. In addition, it is possible to construct a more simplified form of hardware that enables recording of a data code of a sequence whose minimum d run length is not long to an information recording medium such as an optical or magneto-optical disk.

Claims (24)

Adding a different digital word of r bits to the input data word to generate a plurality of intermediate sequences to scramble them, wherein the number of scrambled sequences is less than 2 ^r ; Modulating the plurality of scrambled intermediate sequences into a sequence meeting a condition (d, k) according to a preset m / n coding ratio; And In the modulated (d, k) condition matching sequences, measuring a degree of inclusion of an undesirable subsequence and selecting one (d, k) condition matching sequence accordingly. A method of converting a series of data words into a modulated signal. The method of claim 1, wherein step 1 is 2 ^r of each other to produce another digital word is one, and select the digital words of a smaller number than 2 ^r, and, in addition to the selected digital word to the input data word can be smaller than 2 ^r A method of converting a series of data words into a modulated signal, characterized by generating an intermediate sequence of scrambling them. The method of claim 1, wherein the step 1 is 2 ^r of each other to generate another digital word adding them to the input data word 2 ^r of generating an intermediate sequence, and select the intermediate sequence of the smaller number than the 2 ^r of the And converting a series of data words into a modulated signal. 2. A method according to claim 1, wherein k is equal to or greater than 10 when d = 1 and coding ratio m / n is 9/13. 5. The method of claim 4, wherein the number less than 2 ^{r is} greater than or equal to 15 when k equals 14. The method of claim 4, wherein the number less than 2 ^r is 17 or more when k is 12. The method of claim 4, wherein the number less than 2 ^r is 21 or more when k is 11. The method of claim 1, wherein when d = 2 and the coding rate m / n is 6/11, the k value is 13 or more. The method of claim 8, wherein the number less than 2 ^r is 22 or more when k is 15. 9. The method of claim 8, wherein the number less than 2 ^{r is} greater than or equal to 25 when k is 14. The method of claim 8, wherein the number less than 2 ^r is 27 or more when k is 13. An apparatus for converting a data word to be recorded on a recording medium into modulated data that meets the (d, k) modulation condition of coding ratio m: n (m <n), Generating means for adding a different digital word of r bits to the input data word to generate a plurality of intermediate sequences and to scramble them, wherein the number of scrambled sequences is less than 2 ^r ; And Modulating the scrambled plurality of intermediate sequences into a sequence meeting a (d, k) condition according to a preset m / n coding ratio, and in the modulated (d, k) condition matching sequences, undesirable And a means for measuring the degree of inclusion of the subsequence and selecting one (d, k) condition matching sequence accordingly. The method of claim 12, wherein the generating means, 2 ^r of each part of this to produce another digital word to the input data words to generate a 2 ^r intermediate sequences, and select the intermediate sequence of the smaller number than the 2 ^r of And a series of data words into a modulated signal. The method of claim 12, wherein the generating means, 2 ^r of each part of this to produce another digital word to the input data words to generate a 2 ^r intermediate sequences, and select the intermediate sequence of the smaller number than the 2 ^r of And converting a series of data words into a modulated signal, characterized by scrambling them. 13. The apparatus according to claim 12, wherein when d = 1 and the coding ratio m / n is 9/13, the k value is 10 or more. 16. The apparatus of claim 15, wherein the number less than 2 ^{r is} greater than or equal to 15 when k is 14. 16. The apparatus of claim 15, wherein the number less than 2 ^r is 17 or more when k is 12. 16. The apparatus of claim 15, wherein the number less than 2 ^r is 21 or more when k is 11. 13. The apparatus according to claim 12, wherein when d = 2 and the coding ratio m / n is 6/11, the value of k is 13 or more. 20. The apparatus of claim 19, wherein the number less than 2 ^r is 22 or more when k is 15. 20. The apparatus of claim 19, wherein the number less than 2 ^{r is} greater than or equal to 25 when k is 14. 20. The apparatus of claim 19, wherein the number less than 2 ^r is 27 or more when k is 13. A recording medium in which data is modulated and recorded according to the method of any one of claims 1 to 11. A demodulation device for demodulating data recorded by being modulated according to the method of any one of claims 1 to 11.