PLURAL CHANNEL ERROR CORRECTING METHODS AND MEANS USING ADAPTIVE REALLOCATION OF REDUNDANT CHANNELS AMONG GROUPS OF CHANNELS

摘要

PLURAL CHANNEL ERROR CORRECTING METHODS AND MEANSUSING ADAPTIVE REALLOCATION OF REDUNDANT CHANNELSAMONG GROUPS OF CHANNELSAbstract of the DisclosureWhere data is recorded on logically independent sets ofparallel channels or tracks, the correction of error of verylong (infinite) length cannot be advantageously treated byconventional coding methods unlike finite length error suchas single shot or burst noise. To ensure the correction ofchannels in error from data recovered from a multi-channelstorage medium, a fixed number of channels per set arededicated to error checking bits. In this invention, morethan the usual number of channels in error in any one setare made correctable by adaptively reallocating the unusedredundant channels in the other set. This is accomplishedby encoding and recording in the first redundant channel in.each set vertical parity checks limited to that set whileencoding and recording in the second redundant channel ofeach set, the parity of data taken over both sets of channelsin a predetermined positively or negatively sloped direction.With this type of parity information so recorded, then thedata obtained from up to three known erroneous channels inany one set may be corrected, provided that two sets togetheraggregate not more than four channels in error. Advan-tageously, the vertical and cross-parity checking infor-mation can also be used to generate an internal channel-in-error pointer for the first erroneous track in each set.Additionally, this data can be made to yield a second internalchannel-in-error pointer in at least one of the sets.Lastly, error patterns are identified upon decoding at-1-the intersection of at least two error syndromes one ofwhich is derived from cross-parity checking bits.