Variations on the Gaussian Multiple-Access Channel

This paper studies two models derived from the Gaussian Multiple-Access Channel. In each, information is sent by energy modulation, rather than on the complex signal amplitude. For continuous energy, the model is the additive exponential noise (AEN) channel, whose capacity region equals that of the equivalent Gaussian channel at identical noise and energy levels. Differently from the Gaussian case, its capacity region is not enlarged by using feedback; the source of this discrepancy is linked to a conservation of energy law. The second model is a quantized version of the AEN channel. An outer bound to its capacity region is derived, and shown to be strictly contained in the region for the additive exponential/Gaussian noise channel.