Joint Timing Recovery and Signal Detection for Two-Dimensional Magnetic Recording

Abstract

Two-dimensional magnetic recording (TDMR) is a promising technology for boosting areal densities using sophisticated signal processing algorithms within a systems framework. The channel impairments comprise of 2-D intersymbol interference (ISI), 2-D synchronization errors along with media, and electronic noise sources, making it challenging for designing optimum algorithms and architectures for read/write channels. In this paper, we propose a novel iterative joint timing and signal detection algorithm to handle synchronization errors along with the 2-D ISI for TDMR channels. Our work is novel in two aspects: 1) we develop a discrete timing error model using 2-D random walk by incorporating correlated timing drifts due to phase and frequency offsets and 2) we develop a 2-D joint timing and signal detection engine for handling 2-D ISI constraints along with timing errors toward near maximum likelihood detection. The proposed 2-D joint timing-detection algorithm can be iteratively configured and observed to achieve a significant signal-to-noise ratio gain of > 1.2 dB in bit error rate performance (translating to similar to 10% increase in areal densities around the 1 Tb/in(2) regime with the grain sizes of 10 nm and the bit sizes of 25x25 nm) at the output of 2-D soft-output Viterbi algorithm (SOVA) as compared with a standalone timing loop coupled to a 2-D detector in an open-loop configuration. The efficacy of our proposed algorithm and system architecture is evaluated via simulations for TDMR configurations comprising of a 2-D generalized partial response equalization along the 2-D SOVA with data-dependent noise prediction capability over the Voronoi media model.