Asynchronous Multitrack Detection with a Generalized Partial-Response Maximum-Likelihood Strategy

The industry standard for single-track detection in magnetic recording is partial-response equalization followed by a trellis-based sequence detector. We extend for the first time the partial-response paradigm to the case of multitrack detection when the multiple tracks being jointly detected were written asynchronously, with different bit phases and bit rates. We propose a multiple-input multiple-output (MIMO) partial-response equalizer that equalizes the unsynchronized samples of the multiple readback waveforms to a time-varying MIMO target, thereby enabling a trellis-based rotating-target (ROTAR) detector that accounts for the asynchrony. We evaluate the proposed equalization strategy on a two-dimensional magnetic-recording channel, and find that the proposed receiver outperforms a conventional receiver that detects one track at a time, by a 30% reduction in the bit-error rate, and that it closely matches the performance of a fictitious system in which the tracks are perfectly synchronous.