Study of OFDM Precoded Filter-Bank Waveforms

Forthcoming wireless systems will have to cope with heterogeneous and dense traffic. High demands in terms of bandwidth use efficiency and increased flexibility are therefore required for the related air-interface technology. In this context, Filter-Bank MultiCarrier with Offset QAM (FBMC/OQAM) waveform has been recognized as an enabling technology providing strong assets with a well-confined spectrum and enhanced spectral efficiency with respect to cyclic prefix orthogonal frequency-division multiplexing (OFDM). Nonetheless, FBMC-OQAM presents a few challenges to overcome: the intrinsic interference must be taken into consideration in the channel estimation processes and multiple antenna schemes’ design. Those challenges are induced by the reduction of the orthogonality property to the real field. In this paper, OFDM precoding/decoding is proposed as an alternative to the OQAM signaling for filter-bank-based waveforms. The OFDM precoding makes the waveforms near-complex orthogonal, which enables a straightforward adaptation to channel estimation techniques and MIMO scheme design. Two waveforms based on this precoding, namely fast Fourier transform FBMC and block-filtered OFDM, have been proposed. A common framework is proposed to study the two waveforms. This paper also investigates changing the time structure of the transmitted signal by introducing the rate factor parameter. It is shown that intrinsic interference can be greatly reduced at the price of a slight side-lobe increase.