Trellis coding system for disc storage systems

A sampled amplitude read channel for reading data from a sequence of discrete time sample values generated by sampling an analog read signal emanating from a read head positioned over a storage medium, comprising:

• (a) a sampling device for sampling the analog read signal to generate the sequence of discrete time sample values;
• (b) an equalizer for equalizing the read channel according to an EEPR4 partial response;
• (c) a sequence detector that operates according to a time varying trellis state machine such that d.sub.min.sup.2 .gtoreq.8, the sequence detector for detecting the data from the sample values;
• and
• (d) an encoder/decoder for encoding/decoding the data according to a code constraint which allows runs of X consecutive storage medium transitions to occur only if started at a predetermined periodic data index k, wherein:
• (i) x is an integer greater than one;
• (ii) the periodic data index k is defined over a predetermined number of data indices as
• k modulo N=P
• where P is an integer constant and N is an integer greater than one;
• and
• (iii) the encoder/decoder encodes m bits of user data into n bits of codeword where the code rate m/n is greater than 1/2.

A sampled amplitude read channel for reading data from a sequence of discrete time sample values generated by sampling an analog read signal emanating from a read head positioned over a storage medium, comprising:

• (a) a sampling device for sampling the analog read signal to generate the sequence of discrete time sample values;
• (b) interpolated timing recovery for generating a sequence of interpolated sample values substantially synchronized to a data modulation rate;
• and
• (c) a sequence detector that operates according to a time varying trellis state machine, the sequence detector for detecting the data from the interpolated sample values.

A sampled amplitude read channel for reading data from a sequence of discrete time sample values generated by sampling an analog read signal emanating from a read head positioned over a storage medium, comprising:

• (a) a sampling device for sub-sampling the analog read signal at a rate of less than 91% of a data modulation rate to generate the sequence of discrete time sample values;
• (b) timing recovery for synchronizing the sample values to a data modulation rate, thereby forming substantially synchronous sample values;
• and
• (c) a sequence detector that operates according to a time varying trellis state machine, the sequence detector for detecting the data from the substantially synchronous sample values.

A sampled amplitude read channel for reading data from a sequence of discrete time sample values generated by sampling an analog read signal emanating from a read head positioned over a storage medium, comprising:

• (a) a sampling device for sampling the analog read signal to generate the sequence of discrete time sample values;
• (b) interpolated timing recovery for generating a sequence of interpolated sample values substantially synchronized to a data modulation rate;
• (c) a sequence detector for detecting the data from the interpolated sample values;
• and
• (d) an encoder/decoder for encoding/decoding the data according to a code constraint which allows runs of X consecutive storage medium transitions to occur only if started at a predetermined periodic data index k, wherein:
• (i) X is an integer greater than one;
• (ii) the periodic data index k is defined over a predetermined number of data indices as
• k modulo N=P
• where P is an integer constant and N is an integer greater than one;
• and
• (iii) the encoder/decoder encodes m bits of user data into n bits of codeword where the code rate m/n is greater than 3/4.