On information theoretic aspects of single- and multi-carrier communications

In this paper, we investigate the relation between the quadrature amplitude modulation (QAM) input information rates (IRs) of multi-carrier (MC) and single carrier (SC) systems transmitted over inter-symbol interference (ISI) channels with additive white Gaussian noise (AWGN). In particular, considering uniform power spectrum transmission, we conjecture that, for a given channel impulse response, the IR corresponding to an SC input distribution is higher than that corresponding to an MC input distribution. We give an intuitive justification of our conjecture and confirm it, by means of numerical results, considering two sets of randomly generated channels.