On Power/Bandwidth Efficient Clipped-OFDM and SC/FDE Transmission Schemes with Reduced CP Overhead

In this paper, we consider two reduced-PMEPR (peak to mean envelope power ratio), reduced-CP (cyclic prefix) block transmission alternatives, having in mind an application to the uplink of future mobile broadband systems: clipped (and filtered) OFDM (orthogonal frequency division multiplexing) and SC/FDE (single carrier/frequency-domain equalization). In both cases, we adopt advanced receivers with space diversity and a similar structure, where an iterative cancellation of unavoidable interferences is carried out: interference due to a CP length below the channel memory order, in both cases; deliberate nonlinear interference, in the clipped-OFDM case; residual linear ISI, in the SC/FDE case. Performance results, when a 16-QAM (quadrature amplitude modulation) constellation is adopted in both cases, are reported and discussed, with the help of selected performance bounds. These results show that we can add the benefits of a reduced CP to those of a reduced PMEPR, through the use of the proposed iterative receiver techniques, thereby providing a highly power/bandwidth efficient block transmission, with both clipped-OFDM and SC/FDE schemes. The proposed OFDM receiver technique is shown to ensure the feasibility of a clipping effort strong enough to reduce the OFDM PMEPR to a level below that of the corresponding SC/FDE scheme; however, it is not able to prevent an overall advantage for the SC/FDE side, namely under a strongly reduced CP overhead.