Gaussian multiaccess channels with ISI: Capacity region and multiuser water-filling

Abstract

Abstract-The capacity region of a two-user Gaussian multiac-cess channel with intersymbol interference (ISI), where the inputs pass through respective linear systems and are then superimposed before being corrupted by an additive Gaussian noise process, is found. A novel geometrical method is given to obtain the optimal input power spectral densities and the capacity region. This method can be viewed as a nontrivial generalization of the single-user water-filling argument. We show that as in the traditional memoryless multiaccess channel, frequency-division multiaccess (FDMA), with optimally selected frequency bands for each user, achieves the total capacity of the A--user Gaussian multiaccess channel with ISI. However, the capacity region of the two-user channel with memory is, in general, not a pentagon unless the channel transfer functions for both users are identical. Index Tens-Multiaccess channels, intersymbol interference, channels with memory, Gaussian channels, channel capacity