Uplink FBMC/OQAM-based Multiple Access Channel: Distortion Analysis under Strong Frequency Selectivity

This paper computes the distortion power at the receiver side of an FBMC/OQAM-based OFDMA uplink channel under strong frequency selectivity and/or user timing errors. More precisely, it provides a distortion expression that is valid for a wide class of prototype pulses (not necessarily perfect-reconstruction ones) when the number of subcarriers is sufficiently large. This result is a valuable instrument for analyzing how users interfere to one another and to justify, formally, the common choice of placing an empty guard band between adjacent users. Interestingly, the number of out-band subcarriers contaminated by each user only depends on the prototype pulses and not on the channel nor on the equalizer. To conclude, the distortion analysis presented in this paper, together with some simulation results for a realistic scenario, also provide convincing evidence that FBMC/OQAM-based OFDMA is superior to classic circular-prefix OFDMA in the case of asynchronous users.