Z-channel (information theory)

A Z-channel or binary asymmetric channel is a communications channel model used in coding theory and information theory to represent certain data storage systems. In a Z-channel, 0 bits are always transmitted correctly, but 1 bits may be corrupted and received as 0s with some probability.

This asymmetric error pattern, where errors only occur in one direction (1→0 but never 0→1), makes Z-channels particularly relevant for modeling storage technologies with intrinsic recording asymmetries. For example, in some flash memory systems, stored 1s may degrade over time and be read as 0s, but stored 0s remain stable.