A system comprises an encoder, a precoder, a PRML channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies encoding such that the code string after passing through the precoder has a Hamming distance greater than one to eliminate error events with a small distance at the output of the PRML channel. The present invention also provides codes that after precoding have Hamming distance of 2 and 0 mod 3 number of ones. These codes when used over a PRML channel in an interleaved manner preclude +/-( . . . 010-10 . . . ) error events and error events +/-( . . . 01000-10 . . . ). The code string also has a predetermined minimum number of ones at the output of the PRML channel to help derive a clock from the input signal. The encoder provides a "systematic" encoding scheme in which for many code strings the encoded bits are the same as the input bits used to generate the encoded bits. This systematic approach of the present invention provides an encoder that is easy to implement because a majority of the bits directly "feed through" and non-trivial logic circuits are only needed to generate the control bits. The systematic encoding also dictates a decoder that is likewise easy to construct and can be implemented in a circuit that simply discards the control bit. The encoder preferably comprises a serial-to-parallel converter, a code generator, and a parallel-to-serial converter. The code generator produces a rate 16/18 or 16/17 code. The present invention also includes a method that is directed to encoding bit strings and comprises the steps of: 1) converting the input strings to input bits, and 2) adding at least one bit to produce an encoded string with many ones and a Hamming distance greater than one after precoding.
An encoding circuit for use with a digital signal transmitting apparatus and a digital signal recording/reproducing apparatus encodes a 16-bit information word into a 18-bit code word by trellis encoding method in the condition that the range of the variation of the ADS is limited in such a manner that the 18-bit code word is composed of a combination of 9-bit sub-code words. Thus, while the channel line density and the circuit scale are being suppressed from increasing, the transmission rate of user data can be improved.
A data coding method produces codewords with a scheme that changes for different codewords, and decodes codewords with a scheme that remains constant for all codewords. The coding method receives k user bits, codes the user bits to produce k+r output bits, corrupts any one of the output bits, and accurately reproduces at least k-r-1 user bits. Codewords coded using the appropriate initial conditions are output. For each codeword, the appropriate initial conditions are appended to the codeword coded therefrom.
The present invention pertains to a distance-enhancing coding method that can be applied to digital recording and digital communications. It improves the time-varying maximum transition run method used in a conventional distance-enhancing coding to avoid main error events .+-.(1,-1) from happening. Under the premise of maintaining a code gain of 1.8 dB, the code rate can be increased from 3/4 to 4/5. The invention also provides a method of using an enumeration algorithm and an exhaustive method to search for block codes for distance-enhancing coding, which can find required codes by following specific steps.
A data storage system includes an encoder subsystem comprising an error correction code encoder, a modulation encoder, and a precoder, and a decoder subsystem similarly comprising a detector, an inverse precoder, a channel decoder, and an error correction code decoder. The error correction encoder applies an error correction code to the incoming user bit stream, and the modulation encoder applies so-called modulation or constrained coding to the error correction coded bit stream. The precoder applies so-called precoding to the modulation encoded bit stream. However, this precoding is applied to selected portions of the bit stream only. There can also be a permutation step where the bit sequence is permuted after the modulation encoder before precoding is applied by the precoder. The decoder subsystem operates in the inverse manner.
The inventive mechanism detects wire stuck-at faults, which can be used with any other ECC code. The inventive mechanism determines the number of 1's (or 0's) in the data portion and the ECC code of the data portion. This counted number is then provided with ECC code. The data portion, its ECC, the counted number, and its ECC are transmitted to the destination. At the destination, the message is decoded, and the number of 1's in the received message is compared with the counted number, if there is a discrepancy, then a wire fault is signaled. The mechanism may also detect any number of faults provided the number of 0 to 1 transitions is not the same as the number of 1 to 0 transitions. The mechanism can be reconfigured to work with any transmission wire width.
