Abstract: Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Abstract: Various embodiments of the present invention provide systems and methods for gain control. For example, some embodiments of the present invention provide variable gain control circuits. Such circuits include a zero forcing loop generating a zero forcing feedback and a least mean square loop generating a least mean square feedback. An error quantization circuit generates a hybrid feedback based upon a threshold condition using the zero forcing feedback and the least mean square feedback. A variable gain amplifier is at least in part controlled by a derivative of the hybrid feedback.

Abstract: Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Abstract: A method of feed-forward DC restoration in a perpendicular magnetic read channel is disclosed. The method generally includes the steps of (A) generating a feed-forward signal by performing a first detection on an input signal, wherein a DC component of the input signal was previously filtered out in the perpendicular magnetic read channel, (B) generating a restored signal by summing the input signal and the feed-forward signal, the summing restoring the DC component previously filtered out and (C) generating an output signal by performing a second detection on the restored signal, wherein the first detection is independent of the second detection.

Abstract: An error correction encoder inserts redundant parity information into a data stream to improve system reliability. The encoder can generate the redundant parity information using a composite code. Dummy bits are inserted into the data stream in locations reserved for parity information generated by subsequent encoding. The error correction code can have a uniform or a non-uniform span. The span corresponds to consecutive channel bits that are within a single block of a smaller parity code that is used to form a composite code. The span lengths can be variant across the whole codeword by inserting dummy bits in less than all of the spans.

Abstract: A method of double detection in a perpendicular magnetic read channel is disclosed. The method generally includes the steps of (A) generating an intermediate signal by performing a first detection on an input signal of the perpendicular read channel, the first detection having a first error rate, (B) generating a statistics signal based on the intermediate signal, the statistics signal conveying noise statistics that depend on data in the input signal and (C) generating an output signal by performing a second detection on the input signal using the noise statistics to reduce a second error rate of the second detection compared with the first error rate, wherein the first detection is independent of the second detection.

Abstract: A method of feed-forward DC restoration in a perpendicular magnetic read channel is disclosed. The method generally includes the steps of (A) generating a feed-forward signal by performing a first detection on an input signal, wherein a DC component of the input signal was previously filtered out in the perpendicular magnetic read channel, (B) generating a restored signal by summing the input signal and the feed-forward signal, the summing restoring the DC component previously filtered out and (C) generating an output signal by performing a second detection on the restored signal, wherein the first detection is independent of the second detection.

Abstract: A system for soft-decoding of Reed-Muller coded information has one or more rows of decoding blocks, each decoding block having a soft-output device and a Reed-Muller message passing device. A first soft-output device of a first decoding block processes a coded signal and a zero value probability vector. Each subsequent soft-output device processes the coded information and a non-zero value probability vector. The system for soft-decoding Reed-Muller coded information decodes a code-bit reliability vector from a soft-output device to generate an updated codeword reliability vector, which is used by a next decoding block in a sequence of decoding blocks to reprocess the coded information using the updated reliability vector. The reliability vector is updated through processing in each decoding block to optimize the reliability vector for extraction of the transmitted information from the received information.

Abstract: Two levels of error correction decoding are performed using first and second level decoders. A composite code formed by combining an inner component code and an outer component code can be used to decode the data and correct any errors. Performing two level decoding using a composite code allows the size of the inner parity block to be reduced to a single Reed-Solomon symbol while keeping a good code rate. The first level decoder generates soft information. The soft information can indicate a most likely error event for each possible syndrome value of the inner component code. The soft information can also include error metric values for each of the most likely error events. The second level decoder generates corrected syndrome values based on the soft information using the outer component code. The most likely trellis path that corresponds to the corrected syndrome values is then selected.

Abstract: An error correction encoder inserts redundant parity information into a data stream to improve system reliability. The encoder can generate the redundant parity information using a composite code. Dummy bits are inserted into the data stream in locations reserved for parity information generated by subsequent encoding. The error correction code can have a uniform or a non-uniform span. The span corresponds to consecutive channel bits that are within a single block of a smaller parity code that is used to form a composite code. The span lengths can be variant across the whole codeword by inserting dummy bits in less than all of the spans.

Abstract: The Turbo decoding architecture has a first soft-input soft-output (SISO) device having a complex trellis structure and a Turbo decoder loop with a second SISO device having a simpler trellis structure. Coded information from a channel is processed by the first SISO device to generate a soft-output based on the coded information. The soft-output is then processed in an iterative loop using the second SISO device. The second SISO device interacts with a decoder device to produce a value representative of the transmitted information.

Abstract: A system for soft-decoding of Reed-Muller coded information has one or more rows of decoding blocks, each decoding block having a soft-output device and a Reed-Muller message passing device. A first soft-output device of a first decoding block processes a coded signal and a zero value probability vector. Each subsequent soft-output device processes the coded information and a non-zero value probability vector. The system for soft-decoding Reed-Muller coded information decodes a code-bit reliability vector from a soft-output device to generate an updated codeword reliability vector, which is used by a next decoding block in a sequence of decoding blocks to reprocess the coded information using the updated reliability vector. The reliability vector is updated through processing in each decoding block to optimize the reliability vector for extraction of the transmitted information from the received information.

Abstract: The Turbo decoding architecture has a first soft-input soft-output (SISO) device having a complex trellis structure and a Turbo decoder loop with a second SISO device having a simpler trellis structure. Coded information from a channel is processed by the first SISO device to generate a soft-output based on the coded information. The soft-output is then processed in an iterative loop using the second SISO device. The second SISO device interacts with a decoder device to produce a value representative of the transmitted information.