Bidirectional Decision Feedback Modified Viterbi Detection (BD-DFMV) for Shingled Bit-Patterned Magnetic Recording (BPMR) With 2D Sectors and Alternating Track Widths
Shingled bit-patterned media (BPM) recording is a promising candidate to improve the magnetic recording density above 1 Tb/in2 while keeping the conventional writer design. However, shingled magnetic recording (SMR) leads to a narrower track pitch, and thus increased inter-track interference motivating the investigation of array readers and 2-D sectors. In this paper, we investigate SMR on BPM with 2-D sectors at the channel density of 3.71 Tb/in2. Use of 2-D sectors allows the possibility of using either hard or soft information from already detected tracks in that 2-D sector to improve the detection performance on the current track. An important question in this context is whether all tracks in a 2-D sector should be of the same nominal width or if there is a potential benefit to using different widths for adjacent tracks. Based on our investigation, we show that alternating track widths [i.e., one less-trimmed (fat) track followed by one more-trimmed (narrow) track] are beneficial to a bit error rate (BER) perspective. In particular, we propose and investigate the use of a bidirectional decision feedback modified Viterbi (BD-DFMV) detector to improve the BER performance. Our simulations indicate that for a hypothetical 2-D sector with 13 tracks and 5% media noise and at the target BER of 10-2, using alternating track widths and readback with a single reader, the BD-DFMV algorithm can provide about 1.6 dB signal-to-noise ratio (SNR) gain, compared with using the same detection algorithm but on a 2-D sector with uniform track widths. When using a reader array instead of a single reader, this SNR gain improves to about 2.0 dB. The alternating track width structure also appears to provide more robustness to track mis-registration compared with the 2-D uniform track width case.