  An algorithm that performs joint equalization and decoding for channels with
nonlinear two-dimensional intersymbol interference is presented. The algorithm
performs sum-product message-passing on a factor graph that represents the
underlying system. The two-dimensional optical storage (TwoDOS) technology is
an example of a system with nonlinear two-dimensional intersymbol interference.
Simulations for the nonlinear channel model of TwoDOS show significant
improvement in performance over uncoded performance. Noise tolerance thresholds
for the TwoDOS channel computed using density evolution are also presented.
