CN117059134B - Classification compensation method for nonlinear transition offset in disk data writing process - Google Patents
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Abstract
The invention belongs to the technical field of magnetic recording, and particularly relates to a classification compensation method for nonlinear transition shift in a disk data writing process, which comprises the following steps: determining a compensation level number N of a disk data writing process; in the actual disk data writing process, identifying and determining a local transition pattern taking the current transition bit to be written as the last bit; matching the local transition pattern with N types of local transition patterns corresponding to the compensation level number N, if the local transition pattern belongs to one type of the N types of local transition patterns, adopting a preset compensation value of the type of local transition pattern to carry out nonlinear transition offset compensation on the current transition bit to be written, and if the local transition pattern does not belong to any type, not carrying out nonlinear transition offset compensation on the current transition bit to be written; the method and the device repeatedly execute the step when the next transition bit is needed to be written until the disk data needed to be written is written, and effectively relieve the writing position error caused by nonlinear transition offset while not increasing the writing complexity.
Description
Technical Field
The invention belongs to the field of magnetic recording, and particularly relates to a classification compensation method for nonlinear transition shift in a disk data writing process.
Background
Data play an increasingly critical role in various aspects of human life. Over the last 30 years, the world information technology industry has experienced a subversion of the digital evolution and data storage requirements have grown dramatically. Magnetic recording hard disks remain important in mainstream storage media because of their significant advantages in terms of capacity to price ratio. However, due to the superparamagnetic effect problem, the magnetic storage density has approached a physical limit, and further improvement of areal density faces a three-difficult dilemma (Trilemma), i.e., thermal stability of magnetic recording, writability of magnetic heads, and signal quality are mutually restricted. Medium noise is a central factor affecting signal quality, and its main component is magnetization transition noise caused by nonlinear transition shift (Nonlinear Transition Shift, NLTS). As the recording density increases, the bit size and the grain size become smaller, whereby the influence of media Noise on the Signal-to-Noise Ratio (SNR) of the disk becomes larger. As a primary medium noise source that reduces system performance, NLTS can reduce or eliminate its effects by using write compensation techniques.
NLTS results from the influence of the demagnetizing field of the previous write transition, as shown in FIG. 1. The ideal transition position is determined by the write head magnetic field and the interacting static magnetic field, and the current transition position that should be written should be the ideal transition position, whereas the actual written transition position deviates from the ideal transition position due to NLTS. As the bit length decreases, the interaction between the current actual transition position and the previous actual transition position becomes more and more strong. Therefore, the shift in the transition writing position causes the sampling signal during the read-back to be misaligned with each recording bit, resulting in an error in the detection result.
In high density magnetic recording, the mixed magnetic field cannot be simply superimposed linearly, and nonlinear transition shift effect caused by the nearest two transitions in the recording process is dominant. When the distances between two transition bits are different, the previous transition causes the NLTS value generated by the current transition to be as shown in FIG. 2, naturally, as the recording density increases, NLTS caused by the latest transition also increases, so that at high density, a more effective compensation scheme should be formulated to reduce the influence of NLTS.
To study and eliminate the effect of NLTS occurring during writing, it is first necessary to obtain specific values of NLTS for each magnetization transition position and then compensate. Regarding specific numerical value acquisition of NLTS, the current mode includes two modes of theoretical modeling calculation and actual measurement, the existing theoretical modeling calculation model calculates according to an equivalent magnetic charge method (reference [1 ]), errors exist in calculation of transition shifts in complex transition patterns, and the assumption based on a linear superposition principle does not accord with nonlinear characteristics of NLTS under a high density condition. In addition, the NLTS measurement method is relatively complex and is mainly divided into two types: one is called spectral cancellation or harmonic cancellation; another is a set of methods based on pseudo-random sequences, such as frequency domain double pulse extraction and time domain time correlation methods. However, these methods require that a special series of sequences be written to disk first in order to obtain the value of the nonlinear offset. The measured value of NLTS is the average of NLTS corresponding to all recorded patterns. The distortion caused by NLTS can be mitigated by a simple and common compensation scheme.
With respect to the compensation method, the optimal writing compensation is generally performed on the NLTS according to the recording pattern, and the related method is very few. Based on analysis of Bit Error Rate (BER) after detection of a perpendicular magnetic recording system with NLTS caused by a specific transition pattern, zheng Wu proposed a two-Bit one-level compensation strategy in its paper "Nonlinear Transition Shift and Write Precompensation in Perpendicular Magnetic Recording", which considers only one pair of adjacent transitions, and furthermore, a two-level compensation and a more complex multi-level compensation method (reference [2 ]). However, both the two-stage and multi-stage compensation schemes exist to reduce NLTS for a particular pattern. Due to the complexity of nonlinear distortion, these methods are inefficient and too complex to be practically implemented. Worse still, the number of compensation levels will increase exponentially because of the number of bits involved in the transition pattern.
Since cancellation of transition noise plays an increasingly important role in improving magnetic storage density, it is urgent to search for new effective methods to suppress transition noise.
Disclosure of Invention
Aiming at the defects and improvement demands of the prior art, the invention provides a classification compensation method for nonlinear transition shift in the writing process of disk data, which aims to compensate as many local transition patterns as possible under the condition of not increasing the complexity of a compensation scheme in the writing process.
To achieve the above object, according to one aspect of the present invention, there is provided a classification compensation method for nonlinear transition shift in a disk data writing process, comprising:
determining a compensation level number N of a disk data writing process;
in the actual disk data writing process, identifying and determining a local transition pattern with the window length w taking the current transition bit to be written as the last bit; matching the local transition pattern with N types of local transition patterns corresponding to the compensation level number N, if the local transition pattern belongs to one type of the N types of local transition patterns, adopting a preset compensation value of the type of local transition pattern to carry out nonlinear transition compensation on a current transition bit to be written, and if the local transition pattern does not belong to any type of the N types of local transition patterns, not carrying out nonlinear transition compensation on the current transition bit to be written; and repeatedly executing the step when the next transition bit is required to be written until the disk data required to be written is written, and finishing the classification compensation method of the nonlinear transition offset in the disk data writing process.
Further, the determination mode of the N types of local transition patterns corresponding to the compensation level number N is as follows:
sequentially writing local transition patterns with window length w in an exhaustive manner, wherein the value of the window length w is determined according to the accuracy requirement of actual calculation;
determining the nonlinear transition offset of the current to-be-written transition bit in each of the exhausted partial transition patterns in a theoretical calculation mode, or measuring the nonlinear transition offset of the current to-be-written transition bit in each of the exhausted partial transition patterns in an actual writing mode;
the nonlinear transition offset of the current transition bit to be written in all the exhaustive partial transition patterns is arranged in a descending order, and the partial transition patterns with similar nonlinear transition offset are classified; setting a compensation value for each type of offset;
and taking the first N types of local transition patterns as N types of local transition patterns corresponding to the compensation series N.
Further, when the nonlinear transition offset of the transition bit currently to be written in each of the partial transition patterns that are exhausted is determined by adopting a theoretical calculation manner, the theoretical calculation manner is as follows:
where τ represents the nonlinear transition shift amount of the currently to-be-written transition bit, H demag Representing the demagnetizing field generated by the previous transition bit for the current transition bit to be written, HFG representing the head gradient of the write point, T representing the thickness of the recording medium, M r Representing the remanent magnetization, L representing the distance between the current ideal transition position and the position of the nearest previous actual transition, y representing the depth of the calculated point in the recording layer of the medium from the lower surface of the recording layer, the calculated point being generally taken as the center of the thickness of the recording layer.
Further, the compensation value is set in the following manner:
taking the calculated or measured nonlinear transition offset value as a compensation value;
alternatively, the optimum compensation value is selected according to the detected error rate by trying different compensation values in a violent search mode.
Further, searching common characteristics of each type of local transition patterns in the first N types of local transition patterns, and recording the common characteristics as the characteristics of the type of local transition patterns;
and in the matching process, matching the local transition pattern to be matched with the characteristics of N types of local transition patterns corresponding to the compensation series N, and if the local transition pattern to be matched has the characteristics of a certain type of local transition pattern, considering that the local transition pattern to be matched belongs to the type, and carrying out nonlinear transition compensation on the current transition bit to be written by adopting the preset compensation value of the type of local transition pattern.
The present invention also provides a magnetic recording system comprising: a computer readable storage medium and a processor;
the computer-readable storage medium is for storing executable instructions;
the processor is configured to read executable instructions stored in the computer readable storage medium and perform a classification compensation method for nonlinear transition shifts in a disk data writing process as described above.
The invention also provides a computer readable storage medium comprising a stored computer program, wherein the computer program when run by a processor controls a device in which the storage medium is located to perform a method of classification compensation of nonlinear transition shifts in a disc data writing process as described above.
In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:
(1) The invention provides a method for carrying out similarity matching on a local transition pattern with the window length w taking the current transition bit to be written as the last bit and various local transition patterns, determining which type of local transition pattern the local transition pattern to be matched belongs to, and compensating nonlinear transition offset of the current transition bit to be written by using a compensation value corresponding to the corresponding type. When the same compensation level is adopted, the classification method can compensate more transition patterns in the disc data writing process than the traditional method, so that the disc achieves better bit error rate performance as a whole. Compared with the existing compensation method, each type of local transition pattern comprises more patterns which are required to be compensated in the writing process, the writing complexity is not increased, and the writing position error caused by NLTS is effectively relieved.
(2) The invention provides a classification compensation method for nonlinear transition offset in the process of writing magnetic disk data, which is implemented by determining the type of local transition patterns to be compensated and the nonlinear transition offset compensation value of the current transition bit to be written under each local transition pattern. The invention provides a method for determining N types of local transition patterns corresponding to the compensation series N, namely enumerating the local transition patterns, classifying the local transition patterns according to different nonlinear transition offset amounts, and endowing each type with a compensation value, thereby ensuring the compensation precision and effectively relieving the writing position errors caused by the nonlinear transition offset.
(3) In order to improve the matching efficiency, the invention also provides that after N types of local transition patterns corresponding to the compensation series N are determined, common characteristics of each type of local transition patterns in the previous N types of local transition patterns are searched and recorded as the characteristics of the type of local transition patterns; and in the matching process, matching the local transition pattern to be matched with the characteristics of N types of local transition patterns corresponding to the compensation series N, and if the local transition pattern to be matched has the characteristics of a certain type of local transition pattern, considering that the local transition pattern to be matched belongs to the type, and carrying out nonlinear transition compensation on the current transition bit to be written by adopting the preset compensation value of the type of local transition pattern.
In general, the window size and compensation level of the local transition pattern are predetermined with reference to the data written to the disk; obtaining a local transition pattern according to the size of the window, and calculating the offset of the current transition bit relative to the ideal transition bit, namely nonlinear transition offset; the NLTS obtained by calculation is arranged in a descending order; obtaining distribution after NLTS sequencing, and classifying patterns with similar NLTS values; obtaining a classification result and taking the first N classes for classification compensation; each type of pattern is compensated separately. The invention can carry out writing classification compensation on nonlinear transition shift in the magnetic storage system, and effectively relieves writing position errors caused by nonlinear transition shift.
Drawings
FIG. 1 is a schematic diagram of a nonlinear transition shift effect;
FIG. 2 is a graph of the effect of the distance between the current transition bit and the previous offset bit on NLTS;
FIG. 3 is a flow chart of a method for classifying and compensating nonlinear transition shifts in a disk data writing process according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a perpendicular magnetic recording channel with NLTS write precompensation;
FIG. 5 is a diagram of a representation of magnetic recording data provided by an embodiment of the present invention;
FIG. 6 is a schematic diagram of NLTS obtained by calculating the current transition in different transition patterns and a descending order of the NLTS according to the embodiment of the present invention;
fig. 7 is a schematic diagram showing BER performance comparison using unclassified and classified compensation methods according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Example 1
A sort compensation method for nonlinear transition shift in the disk data writing process is shown in FIG. 3, and comprises the following steps:
determining a compensation level number N of a disk data writing process;
in the actual disk data writing process, identifying and determining a local transition pattern with the window length w taking the current transition bit to be written as the last bit; matching the local transition pattern with N types of local transition patterns corresponding to the compensation level number N, if the local transition pattern belongs to one type of the N types of local transition patterns, adopting a preset compensation value of the type of local transition pattern to carry out nonlinear transition compensation on a current transition bit to be written, and if the local transition pattern does not belong to any type of the N types of local transition patterns, not carrying out nonlinear transition compensation on the current transition bit to be written; and repeatedly executing the step when the next transition bit is required to be written until the disk data required to be written is written, and finishing the classification compensation method of the nonlinear transition offset in the disk data writing process so as to achieve the aim of relieving or eliminating the nonlinear transition offset.
It should be noted that, the present embodiment provides a method for classifying and compensating nonlinear transition shifts in a disc data writing process, and the method is implemented on the premise that the type of the local transition pattern to be compensated and the nonlinear transition shift compensation value of the current transition bit to be written under each local transition pattern need to be determined. Preferably, the method of this embodiment determines the N types of local transition patterns corresponding to the compensation level number N in the following manner:
sequentially writing local transition patterns with window length w in an exhaustive manner, wherein the value of the window length w is determined according to the accuracy requirement of actual calculation; determining the nonlinear transition offset of the current to-be-written transition bit in each of the exhausted partial transition patterns in a theoretical calculation mode, or measuring the nonlinear transition offset of the current to-be-written transition bit in each of the exhausted partial transition patterns in an actual writing mode; the nonlinear transition offset of the current transition bit to be written in each of the partial transition patterns is arranged in a descending order, the partial transition patterns with similar nonlinear transition offset are classified, for example, the partial transition patterns are divided according to the stepping value which is 20% of the maximum offset in all the partial transition patterns, and the specific dividing method is adjusted according to the compensation precision; setting a compensation value for each type of offset; and taking the first N types of local transition patterns as N types of local transition patterns corresponding to the compensation series N.
When the recording medium parameters and the recording bit size B change, the method needs to be re-executed to re-determine the N types of local transition patterns corresponding to the compensation level number N.
According to the classification compensation method provided by the embodiment, enumeration is carried out on local transition patterns, the local transition patterns with different nonlinear transition offset are classified according to the local transition patterns with different nonlinear transition offset, and a compensation value is assigned to each type, when the classification compensation method is applied, the local transition patterns with the window length w taking the current to-be-written transition bit as the last bit are subjected to similarity matching with the local transition patterns of each type, which type of local transition pattern to be matched belongs to is determined, and the nonlinear transition offset of the current to-be-written transition bit is compensated by using the compensation value corresponding to the corresponding type.
In order to improve the matching efficiency, preferably, after determining the N types of local transition patterns corresponding to the compensation level number N, common features of each type of local transition patterns in the first N types of local transition patterns are searched and recorded as features of the type of local transition patterns; and in the matching process, matching the local transition pattern to be matched with the common characteristics of each type of transition pattern in the N types of local transition patterns corresponding to the compensation level number N, and if the local transition pattern to be matched has the characteristics of a certain type of local transition pattern, considering that the local transition pattern to be matched belongs to the type, and adopting the preset compensation value of the type of local transition pattern to carry out nonlinear transition compensation on the current transition bit to be written.
In addition, in the process of determining the N types of local transition patterns corresponding to the compensation level number N, preferably, when determining the nonlinear transition offset of the current transition bit to be written in each of the exhaustively used local transition patterns by adopting a theoretical calculation manner, the theoretical calculation manner is as follows:
where τ represents the nonlinear transition shift amount of the currently to-be-written transition bit, H demag Representing the demagnetizing field generated by the previous transition bit for the current transition bit to be written, HFG representing the head gradient of the write point, T representing the thickness of the recording medium, M r Representing the remanent magnetization, L representing the distance between the current ideal transition position and the position of the nearest previous actual transition, y representing the depth of the calculated point in the recording layer of the medium from the lower surface of the recording layer, the calculated point being generally taken as the center of the thickness of the recording layer.
The theoretical calculation mode mainly focuses on the influence of the nearest neighbor written transition of the transition to be written in the local transition pattern, simplifies the calculation flow, and avoids the linear approximation of the nonlinear transition shift by the existing linear superposition method, so that the method is more practical and accurate.
Further preferably, the setting manner of the compensation value is as follows:
taking the calculated or measured nonlinear transition offset value as a compensation value;
alternatively, the optimum compensation value is selected according to the detected error rate by trying different compensation values in a violent search mode.
To verify the validity of the compensation method, a perpendicular magnetic recording channel model was constructed. Namely, the influence of the NLTS effect of the perpendicular magnetic recording channel on the readback performance is researched, the compensation effects of different NLTS compensation methods are compared, and the compensation values of various transition patterns are optimally designed to achieve the optimal data reading and writing performance.
Wherein the perpendicular magnetic recording channel model is shown in fig. 4. The binary data bit sequence of the input channel, i.e., the 0, 1 sequence, corresponds to the non-return-to-zero modulation (Non Return Zero Code, NRZ) sequence in fig. 5, after the modified inverse non-return-to-zero modulation (Non Return Zero Inverted Code, NRZI) transition, the two polarities in the NRZI sequence correspond to the two write current directions through the write head coil, and the two opposite magnetic fields cause the two opposite magnetizations in the perpendicular direction of the medium, resulting in the recorded information a (k) having two opposite recording states in the perpendicular direction, a (k) e { -1, +1}, the information thus being written to the recording medium. The read-back signal is formed by the read head by inducing a change in magnetization, which can be represented by a signed transition sequence d (k),if d (k) =0, indicating that the current position has no written transition, if d (k) = +1, the direction of the write current will be switched to register a forward transition, otherwise, a reverse transition is registered. The unsigned transition sequence t (k) is the absolute value of the signed transition sequence Representing an exclusive or operation. The local unsigned transition sequence with limited length is the transition pattern in the patent.
The discrete-time readback samples r (k) can be simply expressed as:
where N is the length of the entire signed transition sequence and B is the bit length along the recording track direction. When d (i) noteq0, i.e. t (i) =1, τ i For transition shift of the current writing transition position relative to its ideal position, J i Jitter noise for the current written transition position. s (·) is the isolated transition response. Jitter noise compliance mean of 0 and variance sigma j 2 Normal distribution of (J) i ～N(0,σ j 2 ) Wherein sigma j =p×b, p being the transition position accuracy. Using n (k) to model electronic noise, such electronic noise can be modeled as a mean of 0 and variance of σ 2 Additive white gaussian noise of (c).
To compensate for the transition bit at the appropriate write time, a net offset delta is defined i ＝τ i +δ i To replace τ in equation (1) i Wherein delta i Is the compensation value of the ith transition bit during writing, theoretically delta i May be a positive or negative value but opposite in sign to the transition shift.
The invention uses a truncated 2-order taylor expansion model shown in formula (2) to simulate the read-back signal, the sector size of each pseudo-random sequence a (k) in the embodiment shown in fig. 4 is 512 bytes, and the specific writing sector size can be other general sector size standards. After sampling each recorded information bit, the noisy read-back signal is equalized using a partial response equalizer, and the detection is completed.
Further, when calculating the nonlinear transition shift NLTS generated by the current transition, the calculation of NLTS in this embodiment is by a new theoretical model based on the transition sequence.
Since the position offset of the current transition is caused by the demagnetizing field generated by the written transition preceding the current written transition, the offset is determined by the write field in which the current transition was written and the demagnetizing field of the previous transition pattern.
The parameters of the media and head are as follows: t represents the thickness of the recording medium, t=10 nm; s represents the distance between the medium and the soft underlayer (SoftUnderlayer, SUL), s=10 nm;wherein M is r For the remanent magnetization, HFG is the head gradient (HeadFieldGradient, HFG) of the write spot. It should be appreciated that the media and head parameters shown in this embodiment may be adjusted in connection with the actual application.
Assuming that the distance between the current ideal transition position and the position of the nearest previous actual transition is L, the demagnetizing field generated by the previous actual transition to the current transition is:
the transition shift generated by the current actual transition position relative to the ideal transition position is:
in theory, the offset of the current transition to be written is mainly influenced by the demagnetizing field of the previous transition, and the farther the position of the last actual transition is from the ideal position of the current transition to be written, the weaker the offset of the demagnetizing field of the previous transition to be written has on the position of the current transition to be written. The present embodiment uses a finite length local transition pattern in the unsigned transition sequence t (k) to analyze the NLTS of each current transition to be written. For example: the unsigned transition sequence t (k) is … 01001000100 (1) …, consider a partial transition pattern 00100 (1) with a window length of 6, where (1) represents the transition currently to be written.
It should be noted that the transition pattern (i.e., transition sequence) refers to a sequence of exclusive or calculations of adjacent bits in the recording sequence, and is composed of "0" and "1", wherein "1" indicates that magnetization transition occurs, and "0" indicates that the magnetization state remains unchanged. A transition bit refers to each bit in the transition sequence. Transition refers to a change in magnetization state that occurs in the recorded pattern.
Further, regarding the compensation scheme, the conventional unclassified compensation method is to compensate the position of the current transition to be written with a corresponding value delta for a plurality of local transition patterns including the current transition to be written, so that the offset generated at the position of the transition to be written in each local transition pattern is relieved or counteracted. However, in practical implementation, the method of determining a compensation value for each local transition pattern is simple and low-efficiency, and because the local transition pattern with a certain window length contains a plurality of transition arrangement modes, the positions of the current transitions to be written in all the local transition patterns are compensated, so that the compensation difficulty is greatly increased. In order to balance the computational complexity and the recording performance, the existing method only selects some local transition patterns with larger influence on the current position to be transitioned, corresponding compensation values are pre-assigned to the patterns to compensate, the types of the covered transition patterns are not more, and the influence of NLTS can not be completely eliminated by the compensation scheme.
In the process of compensating the transition shift, in order to compensate more transition bits in the process of writing magnetic disk data, the invention effectively relieves the writing position error caused by NLTS, and simultaneously maintains a limited writing complexity, firstly, the shift amounts of the current transition positions to be written in different local transition patterns are enumerated and calculated according to a theoretical model of the transition shift, or the shift amounts of the current transition bits to be written in the medium are actually written in different local transition patterns, and the nonlinear transition shift amounts of the current transition bits to be written in each enumerated local transition pattern are determined; then, the offsets, namely NLTS values, generated at the current transition positions in different local transition patterns are arranged in a descending order, and the transition patterns are classified according to descending order arrangement results, as shown in FIG. 6, the pattern numbers on the horizontal axis in FIG. 6 refer to the numbers of the enumerated patterns. Each type of local transition pattern contains more transition patterns generated during writing that should be compensated.
Assuming that the recording bit length B is 10nm, table 1 lists the NLTS values of the currently written transition bit in the classified finite transition length patterns, specifically the NLTS values of the currently to be written transition bit in the different classes of unsigned transition patterns of finite length, where X may be "1" or "0", where "1" indicates that a magnetization transition has occurred, "0" indicates that no magnetization transition has occurred, and in particular, "(1)" indicates that a current transition has occurred. The normalized NLTS (tau/B) is used for representing NLTS offset of the transition bit to be written currently in each group of local transition patterns, the offset is classified into one class, then a proper compensation value can be set according to the distribution condition of the offset in each class, the two ways of determining the compensation value are two, the first way is to directly compensate according to the NLTS value obtained by calculation, and the second way is to adopt a violent search way to select the best compensation value according to the detection error rate by trying different compensation values.
The compensation values for the multiple types of local transition patterns with common characteristics are represented as follows:
as described in table 1, each of the behaviors is a type of local transition pattern, which is arranged in descending order according to the degree of transition shift. For a perpendicular magnetic recording system, when primary compensation is employed, only the current transition bit to be written "(1)" of the local transition pattern "X1 (1)" needs to be compensated at the time of writing; when two-stage compensation is adopted, only the first two types of transition patterns need to be compensated; similarly, the use of multi-level compensation requires compensation for the corresponding multi-class transition pattern. When the local transition patterns of multiple types have no common characteristics as described above, a reasonable compensation value is still set for each local transition pattern, and transition patterns in the local transition pattern types are sequentially matched and compensated according to the local transition pattern types to be compensated during writing. The invention is not limited to the number of compensation stages employed by an actual perpendicular magnetic recording system, and in particular, the number of classification compensation stages can be determined based on actual performance and cost requirements. The significance of the invention is that the proposed classification compensation scheme can eliminate the shift of transitions in more patterns at the same compensation level.
Meanwhile, in order to verify the advantages of the classification compensation strategy based on transition pattern classification, which is provided by the invention, compared with the traditional compensation strategy, BER performances of two compensation modes are compared. Under the condition that the jitter precision is 0.01, fig. 7 compares the BER performance of the perpendicular magnetic recording system by adopting the unclassified traditional compensation method and the classification compensation method proposed by the present invention, and the result shows that the classification compensation method of the present invention significantly improves the BER performance of the system.
Example two
A magnetic recording system, comprising: a computer readable storage medium and a processor;
the computer-readable storage medium is for storing executable instructions;
the processor is configured to read executable instructions stored in the computer readable storage medium and execute a classification compensation method for nonlinear transition shifts during writing of disk data according to the first embodiment.
The related technical solution is the same as the first embodiment, and will not be described herein.
Example III
A computer readable storage medium comprising a stored computer program, wherein the computer program, when executed by a processor, controls a device in which the storage medium resides to perform a method of classification compensation of a non-linear transition shift of a disc data writing process as described above.
The related technical solution is the same as the first embodiment, and will not be described herein.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (6)
1. A classification compensation method for nonlinear transition shift in the disk data writing process is characterized by comprising the following steps:
determining a compensation level number N of a disk data writing process;
in the actual disk data writing process, identifying and determining a local transition pattern with the window length w taking the current transition bit to be written as the last bit; matching the local transition pattern with N types of local transition patterns corresponding to the compensation level number N, if the local transition pattern belongs to one type of the N types of local transition patterns, adopting a preset compensation value of the type of local transition pattern to carry out nonlinear transition compensation on a current transition bit to be written, and if the local transition pattern does not belong to any type of the N types of local transition patterns, not carrying out nonlinear transition compensation on the current transition bit to be written; repeatedly executing the step when the next transition bit is required to be written until the disk data required to be written is written, and finishing the classification compensation method of nonlinear transition offset in the disk data writing process;
the N types of local transition patterns corresponding to the compensation series N are determined in the following manner:
sequentially writing local transition patterns with window length w in an exhaustive manner, wherein the value of the window length w is determined according to the accuracy requirement of actual calculation;
determining the nonlinear transition offset of the current to-be-written transition bit in each of the exhausted partial transition patterns in a theoretical calculation mode, or measuring the nonlinear transition offset of the current to-be-written transition bit in each of the exhausted partial transition patterns in an actual writing mode;
the nonlinear transition offset of the current transition bit to be written in all the exhaustive partial transition patterns is arranged in a descending order, and the partial transition patterns with similar nonlinear transition offset are classified; setting a compensation value for each type of offset;
and taking the first N types of local transition patterns as N types of local transition patterns corresponding to the compensation series N.
2. The classification compensation method of claim 1, wherein when determining the nonlinear transition shift amount of the transition bit currently to be written in each of the partial transition patterns that are exhausted by theoretical calculation, the theoretical calculation is:
where τ represents the nonlinear transition shift amount of the currently to-be-written transition bit, H demag Representing the demagnetizing field generated by the previous transition bit for the current transition bit to be written, HFG representing the head write field gradient at the write point, T representing the thickness of the recording medium, M r The remanent magnetization is represented by L, the distance between the current ideal transition position and the position of the nearest previous actual transition, and y, the depth of the calculated point in the recording layer of the medium from the lower surface of the recording layer, the calculated point being taken as the center of the thickness of the recording layer.
3. The classification compensation method according to claim 1, wherein the compensation value is set in the following manner:
taking the calculated or measured nonlinear transition offset value as a compensation value;
alternatively, the optimum compensation value is selected according to the detected error rate by trying different compensation values in a violent search mode.
4. A classification compensation method according to any one of claims 1 to 3, characterized in that the common features of each type of local transition pattern in the first N types of local transition patterns are found and recorded as the features of that type of local transition pattern;
and in the matching process, matching the local transition pattern to be matched with the characteristics of N types of local transition patterns corresponding to the compensation series N, and if the local transition pattern to be matched has the characteristics of a certain type of local transition pattern, considering that the local transition pattern to be matched belongs to the type, and carrying out nonlinear transition compensation on the current transition bit to be written by adopting the preset compensation value of the type of local transition pattern.
5. A magnetic recording system, comprising: a computer readable storage medium and a processor;
the computer-readable storage medium is for storing executable instructions;
the processor is configured to read executable instructions stored in the computer readable storage medium and perform a classification compensation method for non-linear transition shifts during disk data writing as set forth in any one of claims 1-4.
6. A computer readable storage medium, characterized in that the computer readable storage medium comprises a stored computer program, wherein the computer program, when being executed by a processor, controls a device in which the storage medium is located to perform a classification compensation method of a non-linear transition shift of a disc data writing process according to any one of claims 1 to 4.
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| CN101211568A (en) * | 2006-12-28 | 2008-07-02 | 富士通株式会社 | Servo pattern writing apparatus, servo pattern reading apparatus and servo pattern reading method |
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| CN1239296A (en) * | 1998-06-12 | 1999-12-22 | 国际商业机器公司 | By-pass write drivers for high-performance data recording |
| CN1427992A (en) * | 2000-05-10 | 2003-07-02 | 西加特技术有限责任公司 | Compression and storage of written-in error compensation tables in embedded servo disc drive |
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