Suppressing the out-of-band power radiation in multi-carrier systems: A comparative study

Abstract

As of today, orthogonal frequency-division multiplexing (OFDM) has been the dominant technique in broadband transmission systems. However, for the application in cognitive radios, the sidelobes of rectangularly pulsed OFDM signals must be well suppressed to satisfy the rigorous spectral masks. In this context, filter-bank based multi-carrier (FBMC) transmission, which allows designing prototype filters for signal pulse shaping, is considered to be more effective. In this article, different sidelobe suppression schemes for OFDM and pulse-shaped FBMC are comparatively investigated with respect to their out-of-band power radiation and their demand in computational complexity. Our results reveal that FBMC, thanks to the excellent timefrequency localization of the pulse shape, allows for a superior isolation of the transmit signal in frequency, enabling to achieve the minimal out-of-band power leakage for the operation in both contiguous and non-contiguous spectrum. Moreover, the additional complexity required for FBMC compared to the other schemes is very moderate.

Improved FBMC/OQAM uplink performance using an antenna array in a highly frequency selective fading channel

“…Owing to the increase in the symbol duration by the factor of K , the effect of multipath interference in FBMC/OQAM is negligible in a mild frequency‐selective channel. Hence, the application of pulse shaping filters in FBMC/OQAM sets it free from a redundant CP and provides small side lobes with low levels of OOB emission, high spectral efficiency, and robustness to timing and frequency misalignments …”

“…To evaluate the potential advantages, FBMC/OQAM has been compared with OFDM in terms of power and spectral efficiency, computational complexity, and sensitivity to timing offset (TO) and carrier frequency offset (CFO) . In Reference , the authors presented the results of a comparative analysis of spectral efficiency in OFDM and FBMC/OQAM through power spectral density (PSD). The PSD of OFDM was evaluated for different side lobe suppression schemes and compared with the PSD of FBMC/OQAM for three different overlapping factors, K = 2, 3, and 4.…”

“…The PSD of OFDM was evaluated for different side lobe suppression schemes and compared with the PSD of FBMC/OQAM for three different overlapping factors, K = 2, 3, and 4. The analysis showed that, thanks to the low level of OOB emission and the CP absence, FBMC/OQAM outperforms OFDM with respect to the spectral efficiency with an increased number of subcarriers available for signal transmission . It was shown that FBMC/OQAM with K = 4 provides the best spectral confinement, but at the price of increased complexity.…”

“…That was also verified by the results reported in the PHYDYAS project, with an efficiency gain of more than 20% and adequate rise of the computational complexity . Analysis of the computational complexity for different multicarrier modulation at the transmit (Tx) side was also provided in Reference . It was shown that FBMC/OQAM is of a moderate complexity compared to conventional OFDM and OFDM with side lobe suppression techniques; the latter presented improved spectrum usage comparable to that in FBMC/OQAM.…”

Analysis of an FBMC/OQAM scheme for asynchronous access in wireless communications

“…However, for the cognitive radio context as described above, it lacks flexibility and it is likely to lead to poor spectral efficiency, even with the introduction of additional processing [3]. Therefore, an enhanced multicarrier technique is needed, as pointed out in [4], where it is shown that a filter-bank-based multicarrier (FBMC) physical layer can meet the ACLR requirements [2,4].…”