On the capacity and normalisation of ISI channels

We investigate the capacity of various ISI channels with additive white Gaussian noise. Previous papers showed a minimum Eb/N0 of −4.6 dB, 3 dB below the capacity of a flat channel, is obtained using the water-pouring capacity formulas for the 1 + D channel. However, these papers did not take into account that the channel power gain can be greater than unity when water-pouring is used. We present a generic power normalization method of the channel frequency response, namely peak bandwidth normalisation, to facilitate the fair 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 normalization, the capacity curves of these ISI channels are shown.