Modeling Interference Between OFDM/OQAM and CP-OFDM: Limitations of the PSD-Based Model

To answer the challenges put out by the next generation of wireless networks (5G), important research efforts have been undertaken during the last few years to find new waveforms that are better spectrally localized and less sensitive to asynchronism effects than the widely deployed Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM). One of the most studied schemes is OFDM-Offset Quadrature Amplitude Modulation (OFDM/OQAM) based on the PHYDYAS filter pulse. In the recent literature, spectrum coexistence between OFDM/OQAM and CP-OFDM is commonly studied based on the Power Spectral Density (PSD) model. In this paper, we show that this approach is flawed and we show that the actual interference injected by OFDM/OQAM systems onto CP-OFDM is much higher than what is classically expected with the PSD based model in the literature. We show that though using OFDM/OQAM in secondary systems is still advantageous, it brings limited gain in the context of coexistence with incumbent CP-OFDM systems.Comment: 7 pages, 9 figures, ICT 201

On Spectral Coexistence of CP-OFDM and FB-MC Waveforms in 5G Networks

Future 5G networks will serve a variety of applications that will coexist on the same spectral band and geographical area, in an uncoordinated and asynchronous manner. It is widely accepted that using CP-OFDM, the waveform used by most current communication systems, will make it difficult to achieve this paradigm. Especially, CP-OFDM is not adapted for spectral coexistence because of its poor spectral localization. Therefore, it has been widely suggested to use filter bank based multi carrier (FB-MC) waveforms with enhanced spectral localization to replace CP-OFDM. Especially, FB-MC waveforms are expected to facilitate coexistence with legacy CP-OFDM based systems. However, this idea is based on the observation of the PSD of FB-MC waveforms only. In this paper, we demonstrate that this approach is flawed and show what metric should be used to rate interference between FB-MC and CP-OFDM systems. Finally, our results show that using FB-MC waveforms does not facilitate coexistence with CP-OFDM based systems to a high extent.Comment: Manuscript submitted for review to IEEE Transactions on Wireless Communication

OFDM/OQAM modulation for efficient dynamic spectrum access

19 pagesInternational audienceThe cognitive radio idea consists in the exploitation of spectral resources that are unused by a licensed user within a telecommunication standard. After having detected these available frequency bands by some sensing technique, our work takes a stand on the spectrum access problem. This issue requires some constraints on the modulation that must be taken into account. The flexibility in frequency offered by a multicarrier modulation (MCM) then represents a strong advantage which, in addition, can be fully exploited by the OFDM/OQAM modulation. Indeed, the fact that well localised frequency pulse shapes can be employed makes this modulation attractive for an optimised dynamic spectrum insertion. OFDM/OQAM and OFDM-based solutions are finally tested considering two different transmission scenarios. In both scenarios, it is shown that, for OFDM/OQAM, the time-frequency localisation criterion leads to a short prototype filter, satisfying a good compromise in terms of complexity/performance and also leads at the same time to a better peak-to-average power ratio (PAPR) distribution when compared to an analogue windowed OFDM scheme