  Resistive memories are considered a promising memory technology enabling high
storage densities with in-memory computing capabilities. However, the readout
reliability of resistive memories is impaired due to the inevitable existence
of wire resistance, resulting in the sneak path problem. Motivated by this
problem, we study polar coding over channels with different reliability levels,
termed non-stationary polar codes, and we propose a technique improving its bit
error rate (BER) performance. We then apply the framework of non-stationary
polar codes to the crossbar array and evaluate its BER performance under two
modeling approaches, namely binary symmetric channels (BSCs) and binary
asymmetric channels (BSCs). Finally, we propose a technique for biasing the
proportion of high-resistance states in the crossbar array and show its
advantage in reducing further the BER. Several simulations are carried out
using a SPICE-like simulator, exhibiting significant reduction in BER.
