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Séminaire ICI : Rostom Zakaria

Titre et orateur

Intrinsic interference cancellation in MIMO filter-bank based multicarrier (FBMC) systems.
Rostom Zakaria, Cnam.

Date et lieu

Jeudi 24 avril 2014, 14h.
ENSEA, salle 384 [Plan d'accès à l'ENSEA].

Abstract

Multicarrier (MC) Modulation attracts a lot of attention for high speed wireless transmissions because of its capability to cope with frequency selective fading channels turning the wideband transmission link into several narrowband subchannels whose equalization, in some situations, can be performed independently and in a simple manner. Nowadays, orthogonal frequency division multiplexing (OFDM) with the cyclic prefix (CP) insertion is the most widespread modulation among all the MC modulations, and this thanks to its simplicity and its robustness against multipath fading using the cyclic prefix. Nevertheless, CP-OFDM technique causes a loss of spectral efficiency due to the CP which contains redundant information. Moreover, the rectangular prototype filter used in CP-OFDM has a poor frequency localization. This poor frequency localization makes it difficult for CP-OFDM systems to respect stringent specifications of spectrum masks.

To overcome these drawbacks, filter-bank multicarrier (FBMC) with offset QAM was proposed as an alternative approach to CP-OFDM. Indeed, FBMC does not need any CP, and further it offers the possibility to use different time-frequency well-localized prototype filters which allow much better control of the out-of-band emission. The orthogonality constraint for FBMC/OQAM is relaxed being limited only to the real field while for OFDM it has to be satisfied in the complex field. Consequently, one of the characteristics of FBMC/OQAM is that the demodulated transmitted symbols are accompanied by interference terms caused by the neighboring transmitted data in time-frequency domain. The presence of this interference is an issue for some MIMO schemes and until today their combination with FBMC remains an open problem.

We have focused our research work on Alamouti coding scheme and spatial multiplexing system with maximum likelihood detection. We have proposed different receivers based on interference cancellation. We have shown that these kind of receivers suffer from error propagation, and the performance strongly depends on the interference power. Hence, we have also proposed some transceiver structures aiming to reduce the intrinsic interference at the receiver side in order to avoid error propagation.

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