Fig. 3

Reduced channel model. A reduced channel model includes input symbols X, output Y, and additive noise Z. Data-dependent noise (i.e., Z dependent on X) is used to capture certain types of distortions in a communication link. A group of equivalent bit channels is defined by including a mapper to convert bits B₁,…,B _m to a symbol and a soft demapper to map a symbol to Lvalues, L₁,…,L _m