Dispersion of Gaussian channels

The minimum block-length required to achieve a given rate and error probability can be easily and tightly approximated from two key channel parameters: the capacity and the channel dispersion. The channel dispersion gauges the variability of the channel relative to a deterministic bit pipe with the same capacity. This paper finds the dispersion of the additive white Gaussian noise (AWGN) channel, the parallel AWGN channel, and the Gaussian channel with non-white noise and intersymbol interference.