Storage Media Inter-Track interference Cancellation

Abstract

Described embodiments provide a method of cancelling inter-track interference (ITI) from one or more sectors read from a desired track of a storage medium. A read channel reads sectors in a desired track of the storage medium. A decoder of the read channel decodes the read sectors, and if the read sectors are incorrectly recovered from the storage medium, selected sectors of a first adjacent track and a second adjacent track are read. An ITI canceller of the read channel estimates ITI in the read sectors of the desired track corresponding to the selected sectors of each adjacent track and subtracts the estimated ITI of each adjacent track from the data for the sectors of the desired track, providing updated sector data. The ITI cancelled data is replayed to the decoder, Which decodes the ITT cancelled data and provides the decoded ITI cancelled data as output of the read channel.

What is claimed is: 
     
         1 . A storage media controller for cancelling inter-track interference (ITI) in one or more sectors read from a desired track of a storage medium, the media controller comprising:
 a read channel configured to read one or more sectors in a desired track of the storage medium;   an iterative decoder circuit operable to apply a data decoding algorithm to one or more read sectors derived from a desired track of the storage medium to yield a decoded output;   if the decoded output fails to converge:
 the read channel is configured to read selected sectors of a first adjacent track and a second adjacent track; 
 an ITI canceller of the read channel configured to (i) estimate ITI in the one or more read sectors of the desired track corresponding to the selected sectors of the first adjacent track and the second adjacent track, (ii) subtract the estimated ITI of the first adjacent track and the second adjacent track from the data for the one or more sectors of the desired track to provide updated sector data, and (iii) replay the ITI cancelled data to the iterative decoder; 
 the iterative decoder circuit is configured to (i) decode the ITI cancelled data and (ii) provide the decoded ITI cancelled data as output data of the read channel; 
 otherwise, if the decoded output converges, the iterative decoder of the read channel is configured to provide the decoded one or more read sectors as output data of the read channel. 
   
     
     
         2 . The media controller of  claim 1 , wherein the read channel is configured to read the adjacent tracks in a raw-data mode, wherein the data for the adjacent tracks is non-return-to-zero (NRZ) data. 
     
     
         3 . The media controller of  claim 2 , wherein the read channel is configured to read the one or more desired sectors of the desired track in a retry mode having a corresponding maximum global retry threshold and a corresponding maximum local retry threshold. 
     
     
         4 . The media controller of  claim 2 , wherein:
 the read channel is configured to read the one or more desired sectors of the desired track occurs in a first revolution of the storage medium;   the read channel is configured to read the one or more sectors of the desired track in raw-data mode occurs in a second revolution of the storage medium; and   the read channel is configured to read the corresponding sectors of the first adjacent track occurs in a third revolution of the storage medium.   
     
     
         5 . The media controller of  claim 1 , wherein:
 the storage medium is a shingled magnetic recorded media;   the detected data is provided to a host device by at least one of a Small Computer System Interface (“SCSI”) link, a Serial Attached SCSI (“SAS”) link, a Serial Advanced Technology Attachment (“SATA”) link, a Universal Serial Bus (“USB”) link, a Fibre Channel (“FC”) link, an Ethernet link, an IEEE 802.11 link, an IEEE 802.15 link, an IEEE 802.16 link, and a Peripheral Component Interconnect Express (PCI-E) link; and   the media controller is implemented as an integrated circuit chip.   
     
     
         6 . The media controller of  claim 1 , wherein the media controller is implemented as part of an integrated circuit. 
     
     
         7 . A method for cancelling inter-track interference (ITI), the method comprising:
 decoding one or more read sectors of a desired track of a storage medium;   reading selected sectors of a first adjacent track and a second adjacent track;   estimating ITI in the one or more read sectors corresponding to the selected sectors of the first adjacent track and the second adjacent track;   subtracting, by an ITI canceller, the estimated ITI of the first adjacent track and the second adjacent track from the data for the one or more sectors of the desired track to provide updated sector data;   decoding the updated sector data to provide ITI cancelled data;   based upon a determination that at least one of the one or more read sectors are incorrectly recovered from the storage medium:   providing, by a finite impulse response filter of the read channel, Y-samples corresponding to the read sectors to the ITI canceller; and   providing, by the iterative decoder, detected bits corresponding to the Y-samples to the ITI canceller.   
     
     
         8 . The method of  claim 7 , wherein estimating ITI in the one or more read sectors corresponding to the selected sectors of the first adjacent track and the second adjacent track comprises:
 generating, by the ITT canceller, estimated ideal Y-sample values based on the data read for the desired track;   generating an estimated error signal based on a difference between the estimated ideal Y-sample values and actual Y-sample values corresponding to the data read for the desired track; wherein the steps of generating estimated ideal Y-sample values and generating the estimated error signal are performed prior to the step of reading selected sectors of at least one adjacent track; and   estimating, based on the estimated error signal and sectors read from the adjacent track, ITI in the read sectors of the desired track corresponding to the selected sectors of the adjacent track.   
     
     
         9 . The method of  claim 7 , the method further comprising:
 reading the one or more read sectors of the desired track in a raw-data mode, wherein the data for the desired track is non-return-to-Zero (NRZ) data.   
     
     
         10 . The method of  claim 7 , Wherein:
 reading the one or more read sectors of the desired track occurs in a first revolution of the storage medium;   reading the one or more read sectors of the desired track in raw-data mode occurs in a second revolution of the storage medium;   reading the corresponding sectors of the first adjacent track occurs in a third revolution of the storage medium; and   reading the corresponding sectors of the second adjacent track occurs in a fourth revolution of the storage medium.   
     
     
         11 . The method of  claim 7 , the method further comprising:
 reading the adjacent tracks in raw-data mode, wherein the data for the adjacent tracks is non-return-to-Zero (NRZ) data.   
     
     
         12 . The method of  claim 7 , wherein the one or more read sectors of the desired track are read in a retry mode having a corresponding maximum global retry threshold and a corresponding maximum local retry threshold. 
     
     
         13 . The method of  claim 7 , wherein the storage medium is a shingled magnetic recorded media. 
     
     
         14 . A non-transitory machine-readable storage medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method of cancelling inter-track interference (ITI) from one or more sectors read from a desired track of a storage medium, the method comprising:
 decoding one or more read sectors of a desired track of a storage medium;   reading a selected sectors of a first adjacent track and a second adjacent track;   estimating ITI in the one or more read sectors corresponding to the selected sectors of the first adjacent track and the second adjacent track;   subtracting, by the ITI canceller circuit, the estimated ITI of the first adjacent track and the second adjacent track from the data for the one or more sectors of the desired track to provide updated sector data;   decoding the updated sector data to provide ITI cancelled data;   based upon a determination that at least one of the one or more read sectors are incorrectly recovered from the storage medium:
 providing, by a finite impulse response filter of the read channel, Y-samples corresponding to the read sectors to the ITI canceller; and 
 providing, by the iterative decoder, detected bits corresponding to the Y-samples to the ITI canceller. 
   
     
     
         15 . wherein estimating ITI in the one or more read sectors corresponding to the selected sectors of the first adjacent track and the second adjacent track comprises:
 generating, by the ITT canceller, estimated ideal Y-sample values based on the data read for the desired track;   generating an estimated error signal based on a difference between the estimated ideal Y-sample values and actual Y-sample values corresponding to the data read for the desired track; wherein the steps of generating estimated ideal Y-sample values and generating the estimated error signal are performed prior to the step of reading selected sectors of at least one adjacent track; and   estimating, based on the estimated error signal and sectors read from the adjacent track, ITI in the read sectors of the desired track corresponding to the selected sectors of the adjacent track.   
     
     
         16 . The storage medium of  claim 15 , further comprising:
 reading the one or more read sectors of the desired track in a raw-data mode, wherein the data for the desired track is non-return-to-Zero (NRZ) data.   
     
     
         17 . The storage medium of  claim 15 , wherein:
 reading the one or more read sectors of the desired track occurs in a first revolution of the storage medium;   reading the one or more read sectors of the desired track in raw-data mode occurs in a second revolution of the storage medium;   reading the corresponding sectors of the first adjacent track occurs in a third revolution of the storage medium; and   reading the corresponding sectors of the second adjacent track occurs in a fourth revolution of the storage medium.   
     
     
         18 . The storage medium of  claim 15 , further comprising:
 reading the adjacent tracks in raw-data mode, wherein the data for the adjacent tracks is non-return-to-Zero (NRZ) data.   
     
     
         19 . The storage medium of  claim 15 , wherein the one or more read sectors of the desired track are read in a retry mode having a corresponding maximum global retry threshold and a corresponding maximum local retry threshold. 
     
     
         20 . The storage medium of  claim 15 , wherein the storage medium is a shingled magnetic recorded media.