On the capacity and normalisation of ISI channels

We investigate the capacity of various ISI channels with adaptive white Gaussian noise. Previous papers showed a minimum E_b/N₀ of -4.6 dB, 3 dB below the capacity of a flat channel, is obtained using water pouring capacity formulas for the 1 + D channel. However, these papers did not take it into account that the channel power gain can be greater than one when water pouring is used. We present a generic power normalisation method of the channel frequency response, namely peak bandwidth normalisation, to facilitate the pair capacity comparison of various ISI channels. Three types of ISI channel, i.e., adder channels, RC channels and magnetic recording channels, are examined. By using our channel power gain normalisation, the capacity curves of these ISI channels are shown.