Filter Bank-based Multicarrier Modulation for Multiple Access in Next Generation Satellite Uplinks: A DVB-RCS2-based Experimental Study

In the context of the ongoing evolution of satellite communication systems to their next generation, involving higher data rates and increased flexibility, it is of interest to study in depth the applicability of multiple access (MA) multi-carrier modulation (MCM) schemes that have shown promise to meet the requirements of the future terrestrial networks. A comparative study of MA schemes employing offset quadrature amplitude modulation (OQAM)-based filter bank multicarrier (FBMC/OQAM) and classical orthogonal frequency division multiplexing (OFDM) is presented in this paper. The considered air-interface follows the latest Digital Video Broadcasting (DVB) family of standards for the satellite return link. Considering a high-power amplifier (HPA) of a very small aperture terminal (VSAT), the performance of the two MA schemes is evaluated in an asynchronous multiuser satellite environment involving time and frequency synchronization errors. Our results indicate that while FBMC-based MA (FBMA) is more sensitive near saturation and in the presence of timing errors, it is more robust to frequency offset errors not only in terms of the Total Degradation (TD) but also in terms of the Spectral Efficiency (SE), since it only needs minimal guard bands among the different users. This is a preliminary study of the potential gains from the integration of the FBMA technology in the satellite infrastructures and standards. Future work will include results on single-carrier modulation (SCM) FBMA as well

Preamble-Based Channel Estimation for CP-OFDM and OFDM/OQAM Systems: A Comparative Study

In this paper, preamble-based least squares (LS) channel estimation in OFDM systems of the QAM and offset QAM (OQAM) types is considered, in both the frequency and the time domains. The construction of optimal (in the mean squared error (MSE) sense) preambles is investigated, for both the cases of full (all tones carrying pilot symbols) and sparse (a subset of pilot tones, surrounded by nulls or data) preambles. The two OFDM systems are compared for the same transmit power, which, for cyclic prefix (CP) based OFDM/QAM, also includes the power spent for CP transmission. OFDM/OQAM, with a sparse preamble consisting of equipowered and equispaced pilots embedded in zeros, turns out to perform at least as well as CP-OFDM. Simulations results are presented that verify the analysis

Assisted Dictionary Learning for fMRI Data Analysis

Extracting information from functional magnetic resonance (fMRI) images has been a major area of research for more than two decades. The goal of this work is to present a new method for the analysis of fMRI data sets, that is capable to incorporate a priori available information, via an efficient optimization framework. Tests on synthetic data sets demonstrate significant performance gains over existing methods of this kind.Comment: 5 pages, 2 figure