Conference Paper
Wireless OFDMOQAM with a Small Number of Subcarriers
Univ. degli Studi di Palermo, Palermo
DOI: 10.1109/WCNC.2008.38 Conference: Wireless Communications and Networking Conference, 2008. WCNC 2008. IEEE Source: IEEE Xplore

Article: Efficient simulation of orthogonal multicarrier transmission over multipath fading channels
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ABSTRACT: Filterbank orthogonal multicarrier transmission schemes, such as OFDM/OQAM, are currently under intense study for their spectral efficiency and suitability for the physical layer of Cognitive Radio. Nonetheless, the mathematical description of the signal is cumbersome, and closed form expressions for performance figures are not available, so performance analysis on fading channels has to be performed by means of simulations. We propose an algorithm for simulating the received signal over multipath frequency selective fading channels, based on Taylor series expansion of the channel transfer function. The proposed method is compared to the stateoftheart FFTbased method in terms of computational complexity.01/2011; 
Conference Paper: Adaptive BLAST decisionfeedback equalizer for MIMOFBMC/OQAM systems.
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ABSTRACT: Filter bankbased multicarrier modulation (FBMC) using offset quadrature amplitude modulation (OQAM), known as FBMC/OQAM, provides an attractive alternative to the conventional cyclic prefixbased orthogonal frequency division multiplexing (CPOFDM), especially in terms of increased robustness to frequency offset and Doppler spread, and high bandwidth efficiency. However, channel equalization in FBMC/OQAM is a nontrivial task, mainly because of the fact that the subchannels are no longer flat, in general. In multipleantenna (MIMO) timevarying systems, equalizing the channel becomes even more challenging. This paper presents an adaptive T/2spaced decisionfeedback equalization (DFE) algorithm for MIMOFBMC/OQAM systems, that is both computationally efficient and numerically stable. Its structure follows the VBLAST idea and the algorithm is applied in a per subcarrier fashion. Simulation results are reported that demonstrate its effectiveness in timevarying MIMO channels with high frequency selectivity.Proceedings of the IEEE 21st International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2010, 2629 September 2010, Istanbul, Turkey; 01/2010  [Show abstract] [Hide abstract]
ABSTRACT: Filter bankbased multicarrier (FBMC) systems based on offset quadrature amplitude modulation (FBMC/OQAM) have recently attracted increased interest due to their enhanced flexibility, higher spectral efficiency, and better spectral containment compared to conventional OFDM. FBMC/OQAM suffers, however, from an imaginary intercarrier/intersymbol interference that complicates signal processing tasks such as channel estimation. Most of the methods reported thus far in the literature rely on the assumption of (almost) flat subchannels to more easily tackle this problem. However, this assumption may be often quite inaccurate, due to the high frequency selectivity of the channel and/or the small number of subcarriers employed to cope with frequency dispersion in fast fading environments. In such cases, severe error floors are exhibited at medium to high signaltonoise ratio (SNR) values. Moreover, the existing methods provide estimates of the subchannel responses, most commonly in the frequency domain. The goal of this paper is to revisit this problem through an alternative formulation that focuses on the estimation of the channel impulse response itself and makes no assumption on the degree of frequency selectivity of the subchannels. The possible gains in estimation performance offered by such an approach are investigated through the design of optimal (in the MSE sense) preambles, of the smallest possible duration of only one pilot FBMC symbol. Existing preamble designs for flat subchannels are then shown to result as special cases. Simulation results are presented, for both mildly and highly frequency selective channels, that demonstrate the significant improvements in performance offered by the proposed approach over both OFDM and the optimal flat subchannelbased FBMC/OQAM method. Most notably, no error floors appear anymore over a quite wide range of SNR values.06/2013;
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