Pattern Dependent Noise Predictive Belief Propagation

Inter-symbol interference (ISI) channels are encountered in many applications, including magnetic recording and wireless communication systems. In general maximum a-posteriori (MAP) or maximum likelihood (ML) algorithms are used for channel detection. Recently, iterative belief propagation (BP) algorithm is proposed for channel detection as well. When factor graph of the ISI channel is length 4 cycle free, BP gives a similar performance with the MAP detector, while it has the advantage of parallel structure leading to advantages in read channel architectures. Unlike ISI channels with white noise, for magnetic recording systems, noise is correlated and data (pattern) dependent. Correlation is a result of partial response (PR) equalization and data dependence is a result of the media noise (jitter).