Information Capacity of the Mismatched Gaussian Channel.

Information capacity is determined for the additive Gaussian channel when the constraint is given in terms of a covariance different from that of the channel noise. These results, combined with previous results on capacity when the constraint covariance is the same as the noise covariance, provide a complete and general solution for the information capacity of the Gaussian channel without feedback. They are valid for both continuous-time and discrete-time channels, and require only two assumptions the noise energy over the observation period is finite w.p.l., and the constraint is given in terms of a reproducing kernel Hilbert space norm. Applications include channels with ambient noise having unknown covariance, and channels subject to jamming. The results for the mismatched channel differ markedly from those for the matched channel.