Coding for Multilevel Heterogeneous Memories

We consider the problem of information storage in multilevel heterogeneous memories, where different cells can support different data level-sets. Such heterogeneity arises due to variability in the physical cell characteristics in emerging technologies such as Phase Change Memory (PCM) technology, which is our specific motivation. We show that the heterogeneous memory problem can be formulated in terms of the information-theoretic `Channel Coding with Side-Information at Transmitter´ (CSIT) paradigm. We present a binary decomposition of the problem, and show that this decomposition allows for simple binary code constructions. We discuss one such code-construction based on binary Luby Transform (LT) code matrices. We present simulation results using cell variability data collected from a PCM test array, and show that the proposed approach can yield a significant advantage in storage capacity.