Apparatus and method for detecting bit sequence robustly of a change of dc offset in a ook receiver

Provided are an apparatus and a method for detecting a bit sequence, comprising the steps of selecting survivor states of a present level comprising a relatively high occurrence rate by using selection metrics for state-pairs of the calculated states based on parameters to be used to determine a probability distribution of a present receiving signal estimated in each of the states comprising a present transmission bit and a previous transmission bit; additionally removing any one of the states from the states selected in a previous level based on the latest received bit symbol included in the selected survivor states; and detecting the bit sequence based on the path to the survivor states reflecting the situation of which any one state has been additionally removed.