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Browse Prior Art Database

Self Synchronizing Block Code

IP.com Disclosure Number: IPCOM000115047D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Blahut, RE: AUTHOR

Abstract

The purpose of this invention is to provide internal structure to an error-correcting block code to find start of block even if initial symbols are missing. Error-correcting codes are used in many applications, such as magnetic tapes and disks, the compact disk, military communications, mail bar codes, etc. In a stream of data some method must be provided to point to the start of each block of data. This synchronization method is usually designed independent and outside of the error correcting code. However, a powerful ECC creates blocks with many errors and missing symbols. If the synchronization is sensitive to errors and missing symbols, the design is not well balanced.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 66% of the total text.

Self Synchronizing Block Code

      The purpose of this invention is to provide internal structure
to an error-correcting block code to find start of block even if
initial symbols are missing.  Error-correcting codes are used in many
applications, such as magnetic tapes and disks, the compact disk,
military communications, mail bar codes, etc.  In a stream of data
some method must be provided to point to the start of each block of
data.  This synchronization method is usually designed independent
and outside of the error correcting code.  However, a powerful ECC
creates blocks with many errors and missing symbols.  If the
synchronization is sensitive to errors and missing symbols, the
design is not well balanced.

      This invention provides a synchronization procedure that occurs
after error correction is complete.  The message need not and cannot
be synchronized before errors are corrected and erased message
symbols are filled in.  This means that data recovery and
synchronization are equally sensitive to errors, and performance is
not determined by the weaker of the two.

      The method is to define a cyclic block code in the usual way by
choosing an element of order n in the Galois field GF(2m), an
extension
of the symbol field of the code.  A cyclic code is defined in the
usual
way.  Of the codewords, however, only a subset is used.  Thus the
code
is a subcode of another cyclic code defined as follows:

      Choose jo not a zero of the ge...