A communication device and the method thereof are disclosed in embodiments of the present invention. The communication device includes a level determining module, an digital to analog converter and an analog to digital converter. The level determining module determines a plurality of voltage levels and voltage intensity thereof according to an estimating signal to generate a first digital signal. The digital to analog converter converts the first digital signal into a pulse shaped analog signal according to the plurality of voltage levels and voltage intensity thereof. The analog to digital converter converts a first difference signal into a second digital signal wherein the first difference signal equals the result of subtracting the pulse shaped analog signal from a receiving signal.