Eliminating Media Noise While Preserving Storage Capacity: Reconfigurable Constrained Codes for Two-Dimensional Magnetic Recording

TL;DR

This paper introduces capacity-achieving reconfigurable codes for two-dimensional magnetic recording that eliminate media noise by preventing specific error-prone patterns, enhancing storage reliability as devices age.

Contribution

The paper presents novel OT-LOCO codes that forbid both PIS and IPIS patterns, improving upon previous codes and offering reconfigurability for different device aging stages.

Findings

OT-LOCO codes eliminate media noise at practical densities.

Simulation confirms effectiveness of OT-LOCO in pattern prevention.

A lower-complexity coding scheme also reduces error propagation.

Abstract

Magnetic recording devices are still competitive in the storage density race thanks to new technologies such as two-dimensional magnetic recording (TDMR). Error-prone patterns where a bit is surrounded by complementary bits at the four positions with Manhattan distance $1$ on the TDMR grid are called plus isolation (PIS) patterns. Recently, we introduced optimal plus LOCO (OP-LOCO) codes that prevent these patterns from being written. However, as the device ages, error-prone patterns where a bit is surrounded by complementary bits at only three positions with Manhattan distance $1$ emerge, and we call these incomplete PIS (IPIS) patterns. In this paper, we present capacity-achieving codes that forbid both PIS and IPIS patterns in TDMR systems with wide read heads. We collectively call these patterns rotated T isolation (RTIS) patterns, and we call the new codes optimal T LOCO (OT-LOCO) codes. We analyze OT-LOCO codes and derive their encoding-decoding rule. Simulation results demonstrate that OT-LOCO codes entirely eliminate media noise at practical TD densities. We suggest using OP-LOCO codes early in the device lifetime, then reconfiguring to OT-LOCO codes later on. Moreover, we introduce another coding scheme to remove RTIS patterns which offers lower complexity, lower error propagation, and track separation.