Channel coding for binary recording with intersymbol interference

The saturation recording channel with fixed-amplitude bipolar inputs, a linear Lorentzian read-back transition response, and additive Gaussian noise is modeled. Linear density increase on such a channel can be achieved only by increasing the clock rate of the written data signal. The authors define a measure of coding gain for the recording channel that compares a coded system with an uncoded system, each at a different clock rate, but with the same linear density (or data rate). This measure can be decomposed into the sum of an equalization gain and a fundamental coding gain. It is shown that good equalization gain can be achieved by choosing multidimensional codewords such that their power spectra are 'matched' to the channel pulse response spectrum, and they have increased minimum distance at the channel output.<>