Effect of delay constraint and causal feedback on the wideband performance of multiaccess block-fading channels

We consider a multiaccess Gaussian block fading channel where transmitters have causal state information and must deliver their message within a finite delay. Variable-rate coding, with input power constraint enforced on a per-codeword basis, is examined. We characterize the average capacity region and average capacity region per unit energy, the limiting behavior for large delay and the wideband slope of the spectral efficiency versus (E/sub b//N/sub 0/) dB.