Abstract: Methods and apparatus are provided for improved physical re-read operations in a hard disk drive. The disclosed methods and apparatus selectively retain data in a hard disk drive. A signal is read in an iterative read channel by assigning a reliability metric to each of a plurality of segments in a read signal; repeating the assigning step for a plurality of read operations; and selectively retaining the segments based on the assigned reliability metric. The read signal can be obtained by positioning a transducer over a storage media. The reliability metric may be based on soft bit decisions; log likelihood ratios or a noise estimation of a given segment.

Abstract: A decoding system includes a timing loop for use in error recovery mode operations, in which “fast decode” bit values that are used for timing recovery purposes in the normal modes of operation are replaced, at an appropriate iteration in the error recovery mode, with detected bit values from an iterative detector. The replacement occurs after a reread operation in which the timing loop maintains lock.

Abstract: A device and process to compensate for asymmetrical qualities of an analog input signal, if present, and generate a timing signal. The timing signal is then used for analog to digital conversion.

Abstract: Aspects of the disclosure provide a method for detecting land pre-pits. The method can adaptively adjust a threshold for detecting the land pre-pits in order to improve the correctness of detecting. The method for detecting land pre-pits can include extracting a land pre-pit data stream from a reading signal based on a land pre-pit threshold, the reading signal corresponding to land pre-pits of an optical medium, comparing the land pre-pit data stream with format information of the optical medium to obtain an error signal, and adjusting the land pre-pit threshold based on the error signal.

Abstract: Methods are disclosed for detecting a thermal asperity condition of a head that is configured to generate a read signal by reading data on a rotatable data storage disk in a disk drive. The read signal includes a data component and a thermal component. The read signal is compared to a thermal asperity threshold to detect occurrence of an excessive level of the thermal component of the read signal as a thermal asperity condition of the head. The thermal asperity threshold is varied in response to a rate of occurrence of data value transitions in the data component of the read signal. The thermal asperity threshold can be increased in response to a decrease in the rate of occurrence of data value transitions, and can be decreased in response to an increase in the rate of occurrence of data value transitions. By varying the thermal asperity threshold, the sensitivity of the thermal asperity detector may be improved to allow lower level thermal asperity conditions to be detected with increased accuracy.

Abstract: Methods of compensating for radial incoherence in servo information that is read from adjacent servo tracks that have a phase offset relative to one another on a data storage disk of a disk drive are provided. While a transducer is seeking to a target track, the transducer generate a servo information signal that has a first component from servo information read from a first servo track on the disk and a second component from servo information read from a second servo track that is radially adjacent to the first servo track. The servo information in the first and second servo tracks are offset by a non-zero phase error relative to one another and are in a same servo sector on the disk. The servo information signal is sampled to generate a series of sampled servo values. A phase error of a group of the sampled servo values is determined. The sampled servo values are compensated in response to the determined phase error to generate compensated servo values with at least reduced phase error.

Abstract: Tracking methods and systems for providing timing recovery of continuous signals is presented. According to one embodiment, the method includes: sampling a continuous signal; estimating a timing disturbance of the sampled continuous signal; generating a timing adjustment signal in accordance with the estimated timing disturbance; and adjusting a sampling signal associated with a sampling device based on the timing adjustment signal.

Abstract: A method and apparatus for modulating multilevel data arrays to make them suitable for storage in multidimensional storage media, such as in holographic storage. In order to get a uniform signal of constant energy at the recording plane, first the multilevel data array, Vout, displayed on a spatial light modulator, has frequent transitions between symbols of different levels, and second it has constant energy. The energy is defined as the summation of the values of the symbols in the data array. The first constraint is achieved using V?in=Vin?qM(q, ZO), where ?q stands for the modulo-q addition operation; M(q, Zo) is a data array with randomly distributed symbols of q levels, where q is the number of levels and ZO is the seed used to generate the random multilevel data array.

Abstract: A method for communicating binary data and a digital communication system are presented. According to one embodiment, the method includes encoding a message word by multiplying the message word with a generator matrix, wherein the generator matrix multiplied by the transpose of a parity check matrix for a low density parity check code yields a null set, and wherein the parity check matrix has a column weight of two. Additionally disclosed is an encoding scheme based on a three-tier Tanner graph having a girth of twelve.

Abstract: A majority detector for error recovery provides hard and soft majority detection.

Abstract: Recording/reproducing methods and apparatuses for a magneto-optical recording medium are disclosed. The magneto-optical recording medium may include a recording layer in which information can be recorded and a reproducing layer to which information in the recording layer can be transferred. According to one embodiment, the method includes encoding the data to be recorded/reproduced with a low-density parity check code, writing the encoded data to the recording layer of the magneto-optical recording medium, transferring the encoded data from the recording layer to the reproducing layer, and decoding the encoded data from the reproducing layer.

Abstract: A method for communicating binary data and a digital communication system are presented. According to one embodiment, the method includes encoding a message word by multiplying the message word with a generator matrix, wherein the generator matrix multiplied by the transpose of a parity check matrix for a low density parity check code yields a null set, and wherein the parity check matrix has a column weight of two. Additionally disclosed is an encoding scheme based on a three-tier Tanner graph having a girth of twelve.

Abstract: Tracking methods and systems for providing timing recovery of continuous signals is presented. According to one embodiment, the method includes: sampling a continuous signal; estimating a timing disturbance of the sampled continuous signal; generating a timing adjustment signal in accordance with the estimated timing disturbance; and adjusting a sampling signal associated with a sampling device based on the timing adjustment signal.

Abstract: A method and apparatus for modulating multilevel data arrays to make them suitable for storage in multidimensional storage media, such as in holographic storage. In order to get a uniform signal of constant energy at the recording plane, first the multilevel data array, Vout, displayed on a spatial light modulator, has frequent transitions between symbols of different levels, and second it has constant energy. The energy is defined as the summation of the values of the symbols in the data array. The first constraint is achieved using V′in=Vin⊕qM (q, ZO), where ⊕q stands for the modulo-q addition operation; M(q, ZO) is a data array with randomly distributed symbols of q levels, where q is the number of levels and ZO is the seed used to generate the random multilevel data array.