Low-Complexity Constrained Coding Schemes for Two-Dimensional Magnetic Recording

The two-dimensional magnetic recording (TDMR) technology promises a remarkable increase in data storage density using the already-existing magnetic materials. Advanced TD signal processing techniques are required for this technology to fulfill its potential. Constrained coding, which prevents TD error-prone data patterns from being written, is among those techniques. In this paper, we propose lexicographically-ordered constrained (LOCO) coding schemes that offer low complexity, low latency, and low error propagation for TDMR systems with wide read heads, where coding can be applied on groups of 3 down tracks each. In particular, we introduce simple plus LOCO (SP-LOCO) and simple T LOCO (ST-LOCO) coding schemes, where codes defined over GF(2) and GF(4), respectively, are used instead of codes defined over GF (8), allowing the separation of uncoded streams. To better understand the behavior of the constrained-coded system, we derive the probability of transition, both in the horizontal and vertical directions, for the case of SP-LOCO and ST-LOCO coding, and we compare them to the case of optimal, rate-wise, LOCO codes. Moreover, we introduce simulation results on a practical TDMR model that demonstrate the performance gains achieved via the proposed schemes.