Efficient POPS-OFDM Waveform Design for Future Wireless Communication Systems

Future wireless networks are required to offer new applications and services, which will experience high dispersions in time and frequency, incurred mainly by coarse synchronization. Coarse synchronization is induced by signaling overhead reduction and dictated by the tremendous optimization of the radio interface efficiency. It is expected to dramatically damage waveform orthogonality in conventional orthogonal frequency-division multiplexing (OFDM) systems and to result in oppressive intercarrier interference (ICI). To alleviate the degradation in performance caused by ICI, the concept of nonorthogonal multiplexing has been promoted, as a serious alternative to strict orthogonal multiplexing, for guaranteeing the OFDM benefits without requiring high-level synchronization. Within this nonorthogonal multiplexing framework, ping-pong optimized pulse shaping-OFDM (POPS-OFDM) has been introduced as a powerful tool to efficiently design waveforms, which withstand future multicarrier systems' dispersion impairments. In this paper, we investigate the discrete time version of the POPS-OFDM approach and study its sensitivity and robustness against estimation and synchronization errors. Based on numerical results, we show that POPS-OFDM provides an important gain in the signal-to-interference ratio, typically higher than 5 dB, with respect to conventional OFDM. We also demonstrate that POPS-OFDM brings an increased robustness against synchronization errors and ensures a dramatic reduction in out-of-band emissions, enabling flexible and improved spectrum utilization.