On maximum achievable information rates of single-carrier and multi-carrier systems over the ultra wideband channels

In terms of information theory, in this paper, the maximum achievable information rates of modulation systems are investigated over ultra wideband (UWB) multi-path channels where channel state is only known at the receiver. The capacity and mutual information of multi-carrier and single-carrier systems with digital modulation are compared using different UWB channel parameters. Assuming the inputs are i.i.d. equiprobable, the mutual information of SC systems is evaluated with frequency domain equalization (FDE) and with an a posteriori probability (APP) detector, respectively. The capacity of multi-carrier systems is evaluated with orthogonal frequency-division multiplexing (OFDM). Numerical results show the mutual information of SC APP system is better than that of OFDM system over UWB channels, though SC FDE alone causes capacity loss of SC system due to residual ISI of linear MMSE processing. Therefore, a hybrid nonlinear or iterative SC system to eliminate the residual ISI is indispensable.