Trellis based detection with pattern dependent noise prediction (PDNP) has become standard practice in the HDD industry. In a typical single-track signal processing scheme, the received samples from the read head are first filtered by a linear equalizer with a 1D partial response (PR). The linear filter output flows into a trellis-based (e.g. BCJR) detector that employs a super-trellis based on the PR mask ISI channel and a 1D pattern dependent noise prediction (1D PDNP) algorithm. The effective channel model has a media noise term which models signal dependent noise due to, e.g., magnetic grains intersected by bit boundaries. The media noise can influence two or more bit readback values. The trellis detector sends soft estimates of the coded bits to a channel decoder, which outputs estimates of the user information bits. There are two problems with traditional PDNP. First, when the number of tracks Nt simultaneously processed is greater than one, e.g. in two-dimensional magnetic recording (TDMR), the number of trellis states can become impractically large; this is the state explosion problem. Second, the relatively simple autoregressive noise model and linear prediction used in PDNP is somewhat restrictive and may not accurately represent the media noise, especially at high storage densities; this is the modeling problem. To address the state explosion problem, we separate the ISI detection and media noise prediction into two separate detectors and use the turbo-principle to exchange information between them, thus avoiding use of a super-trellis. To address the modeling problem, we design and train deep neural network (DNN) based media noise predictors. As DNN models are much more general than autoregressive models, they give a more accurate model of magnetic media noise than PDNP; this more accurate modeling results in reduced detector BERs compared to PDNP.
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Turbo-Connected Neural Network Media Noise Cancellation Strategy for Asynchronous Multitrack Detection
Multitrack detection architectures provide throughput and areal density gains over the current industry’s standard of single-track detection architectures. One major challenge of multitrack architectures is the complexity of implementing conventional pattern-dependent media noise prediction (PDNP) strategy within the multitrack symbol detector. In this paper we propose a neural network media noise predictor with manageable complexity that iterates with our rotating target (ROTAR) symbol detector in the turbo equalization fashion to predict and cancel the media noise for multitrack detection of asynchronous tracks. We evaluate the proposed detection strategy on a realistic two-dimensional magnetic-recording channel, and find that the proposed solution can effectively mitigate the media noise and therefore can replace the prohibitively complex PDNP solution for multitrack detection.
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- Award ID(s):
- 2238990
- PAR ID:
- 10509920
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- 2023 IEEE 34th Magnetic Recording Conference (TMRC)
- ISBN:
- 979-8-3503-4015-0
- Subject(s) / Keyword(s):
- Intertrack interference multitrack detection multiple-input multiple-output (MIMO) channel timing recovery turbo equalization two-dimensional magnetic recording (TDMR)
- Format(s):
- Medium: X
- Location:
- Minneapolis, MN, USA
- Sponsoring Org:
- National Science Foundation
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