In magnetic recording (MR) systems, data is typically recorded on concentric circular tracks on a magnetic media as a sequence of small magnetic domains. Data written onto the tracks that neighbor a given track will affect the signal read back from the media of the given track. The signal induced during the read of the given track as a result of one or more neighboring tracks is referred to as crosstalk or inter-track interference (ITI). The mitigation of the ITI noise caused by the neighboring tracks in the read back signal of the given track typically relies on information about the data pattern from the neighboring tracks supplied to an ITI mitigation circuit or process.
ITI is of particular concern in hard disk drives (HDD) where concentric or spiral tracks of data are recorded on the media in close proximity to one another, relative to the size of the head. The capacity of the disk drive is increased by placing the tracks closer together. ITI is known to increase with technology scaling, however, and becomes a significant source of noise as track separation distances become smaller. As the tracks are placed closer together, the neighboring tracks are more likely to influence the signal of the given track when it is read back from the media, reducing the overall signal-to-noise ratio. ITI thus limits the number of tracks that can reliably be stored in a given area of a magnetic medium. ITI is of even greater concern in Shingled Magnetic Recording (SMR) systems, where the tracks are placed close enough that the tracks touch one another in some cases, and in other cases can even overlap one another when written with data.
A number of techniques have been proposed for mitigating the effect of ITI in magnetic recording systems. In existing SMR implementations, for example, the mitigation process is typically performed by software in the hard disk controller (HDC). It has been found, however, that when ITI mitigation is enabled, the HDC cannot process data fast enough to recover more than a few sectors (and typically only one sector) for every 3-6 revolutions of the disk. Each revolution of the disk, however, may contain, for example, 500 or more sectors (depending on, e.g., the particular disk drive that is employed, the size of the platter and the radial position of each track on the disk).
A need therefore exists for improved techniques for mitigating the effect of ITI. A further need exists for hardware-based techniques for mitigating the effect of ITI. Yet another need exists for hardware-based techniques for mitigating the effect of ITI that do not require a hard disk controller to perform the ITI computations.