Error Control in Duobinary Data Systems by Means of Null Zone Detection

It is shown that duobinary data system performance can be improved at least 0.7 dB in the presence of Gaussian noise by using a null zone detection procedure. Most nulls can be replaced by correct values using the analog signal redundancy information. Nulls which cannot be replaced using the analog redundancy are restored to their most probable values on the basis of the received sample levels.