FTN multicarrier transmission based on tight Gabor frames

A multicarrier signal can be synthesized thanks to a symbol sequence and a Gabor family (i.e., a regularly time-frequency shifted version of a generator pulse). In this article, we consider the case where the signaling density is increased such that inter-pulse interference is unavoidable.Over an additive white Gaussian noise channel, we show that the signal-to-interference-plus-noise ratio is maximized when the transmitter and the receiver use the same tight Gabor frame. What is more, we give practical efficient realization schemes and show how to build tight frames based on usual generators. Theoretical and simulated bit-error-probability are given for a non-coded system using quadrature amplitude modulations. Such a characterization is then used to predict the convergence of a coded system using low-density parity-check codes. We also study the robustness of such a system to errors on the received bits in an interference cancellation context

Performances of Weighted Cyclic Prefix OFDM with Low-Complexity Equalization

International audience—In this paper, we justify low-complexity equalization techniques for weighted cyclic prefix (WCP)-OFDM. This modulation technique refers to filter bank based multicarrier (FBMC) transmission system provided with short filters. It allows the use of non-rectangular waveforms in order to mitigate interference caused by time-frequency selective channels while preserving an efficient implementation. Index Terms—Time-varying multipath channels, filter bank based multicarrier modulations, equalization, efficient realization

Enhanced Multicarrier Techniques for Professional Ad-Hoc and Cell-Based Communications (EMPhAtiC) Document Number D3.3 Reduction of PAPR and non linearities effects

Livrable d'un projet Européen EMPHATICLike other multicarrier modulation techniques, FBMC suffers from high peak-to-average power ratio (PAPR), impacting its performance in the presence of a nonlinear high power amplifier (HPA) in two ways. The first impact is an in-band distortion affecting the error rate performance of the link. The second impact is an out-of-band effect appearing as power spectral density (PSD) regrowth, making the coexistence between FBMC based broad-band Professional Mobile Radio (PMR) systems with existing narrowband systems difficult to achieve. This report addresses first the theoretical analysis of in-band HPA distortions in terms of Bit Error Rate. Also, the out-of band impact of HPA nonlinearities is studied in terms of PSD regrowth prediction. Furthermore, the problem of PAPR reduction is addressed along with some HPA linearization techniques and nonlinearity compensation approaches

Non-rectangular perfect reconstruction pulse shaping based ICI reduction in CO-OFDM

In this paper, we propose to increase residual carrier frequency offset tolerance based on short perfect reconstruction pulse shaping for coherent optical-orthogonal frequency division multiplexing. The proposed method suppresses the residual carrier frequency offset induced penalty at the receiver, without requiring any additional overhead and exhaustive signal processing. The Q-factor improvement contributed by the proposed method is 1.6 dB and 1.8 dB for time-frequency localization maximization and out-of-band energy minimization pulse shapes, respectively. Finally, the transmission span gain under the influence of residual carrier frequency offset is ̃62% with out-of-band energy minimization pulse shape

MIMO signal processing in offset-QAM based filter bank multicarrier systems

Next-generation communication systems have to comply with very strict requirements for increased flexibility in heterogeneous environments, high spectral efficiency, and agility of carrier aggregation. This fact motivates research in advanced multicarrier modulation (MCM) schemes, such as filter bank-based multicarrier (FBMC) modulation. This paper focuses on the offset quadrature amplitude modulation (OQAM)-based FBMC variant, known as FBMC/OQAM, which presents outstanding spectral efficiency and confinement in a number of channels and applications. Its special nature, however, generates a number of new signal processing challenges that are not present in other MCM schemes, notably, in orthogonal-frequency-division multiplexing (OFDM). In multiple-input multiple-output (MIMO) architectures, which are expected to play a primary role in future communication systems, these challenges are intensified, creating new interesting research problems and calling for new ideas and methods that are adapted to the particularities of the MIMO-FBMC/OQAM system. The goal of this paper is to focus on these signal processing problems and provide a concise yet comprehensive overview of the recent advances in this area. Open problems and associated directions for future research are also discussed.Peer ReviewedPostprint (author's final draft

On zero-forcing equalization for short-filtered multicarrier faster-than-Nyquist signaling

Within the context of faster-than-Nyquist signaling, a low-complexity multicarrier system based on short-length filters and zero-forcing turbo equalization is introduced. Short-length filters allow a reduced-size block processing while zero-forcing equalization allows a linear reduced-complexity implementation. Furthermore, rectangular and out-of-band energy minimization pulse shaping demonstrates competitive performance results over an additive white Gaussian noise channel while keeping a lower computational cost than other multicarrier faster-than-Nyquist systems

Analyse du système linéaire optimal pour les communications multiporteuses au-delà de la cadence de Nyquist

Les communications au delà de la cadence de Nyquist permettent une augmentation de l'efficacité spectrale en contre-partie d'une complexité plus élevée. Concernant les communications multiporteuses, les travaux menés jusque là se sont principalement focalisés sur l'étude des systèmes non-linéaires exploitant des techniques de codage et/ou d'égalisation, sans considération ou optimisation particulière de la partie linéaire du système. Dans cet article, nous analysons le compor-tement du système linéaire multiporteuse optimal lorsqu'il est utilisé seul ou avec des structures de réception non-linéaires (décodage itératif et égalisation à retour de décision). Nous nous intéressons également aux limites des hypothèses com-munément utilisées lors de l'implémentation de ces systèmes non-linéaires. L'utilisation du système linéaire optimal permet une expression analytique de la probabilité d'erreur qui peut être utilisée pour prédire les performances et aider la conception de systèmes codés. Ce travail met aussi en avant le bon compromis performances/complexité offert par l'égaliseur à retour de décision dans le contexte des communications au-delà de la cadence de Nyquist

Analysis of a FTN Multicarrier System: Interference Mitigation Based on Tight Gabor Frames

Cognitive radio applications require flexible waveforms to overcome several challenges such as opportunistic spectrum allocation and white spaces utilization. In this context, multicarrier modulations generalizing traditional cyclic-prefix orthogonal frequency-division multiplexing are particularly justified to fit time-frequency characteristics of the channel while improving spectral efficiency.In our theoretical framework, a multicarrier signal is described as a Gabor family the coefficients of which are the symbols to be transmitted and the generators are the time-frequency shifted pulse shapes to be used. In this article, we consider the case where non-rectangular pulse shapes are used with a signaling density increased such that inter-pulse interference is unavoidable. Such an interference is minimized when the Gabor family used is a tight frame. We show that, in this case, interference can be approximated as an additive Gaussian noise. This allows us to compute theoretical and simulated bit-error-probability for a non-coded system using a quadrature phase-shift keying constellation. Such a characterization is then used in order to predict the convergence of a coded system using low-density parity check codes. We also study the robustness of such a system to errors on the received bits in an interference cancellation context

Analysis of the optimal linear system for multicarrier FTN communications

National audienceFaster-than-Nyquist signalization allows for a better spectral efficiency at the expense of an increased complexity. Regarding multicarrier communications, previous work mainly relied on the study of non-linear systems exploiting coding and/or equalization techniques, with no particular optimization regarding the linear part of the system. In this paper, we analyse the behavior of the optimal linear multicarrier system when used with non-linear receiving structures (iterative decoding and direct feedback equalization), or in a standalone fashion. We also investigate the limits of the assumptions commonly made for the implementation of such non-linear systems. The use of this optimal linear system allows for a closed-form expression of the bit-error probability which can be used to predict the performances and help the design of coded systems. Our work also highlights the great performance/complexity trade-off offered by decision feedback equalization in a faster-than-Nyquist context.Les communications au delà de la cadence de Nyquist permettent une augmentation de l'efficacité spectrale en contre-partie d'une complexité plus élevée. Concernant les communications multiporteuses, les travaux menés jusque là se sont principalement focalisés sur l'étude des systèmes non-linéaires exploitant des techniques de codage et/ou d'égalisation, sans considération ou optimisation particulière de la partie linéaire du système. Dans cet article, nous analysons le compor-tement du système linéaire multiporteuse optimal lorsqu'il est utilisé seul ou avec des structures de réception non-linéaires (décodage itératif et égalisation à retour de décision). Nous nous intéressons également aux limites des hypothèses com-munément utilisées lors de l'implémentation de ces systèmes non-linéaires. L'utilisation du système linéaire optimal permet une expression analytique de la probabilité d'erreur qui peut être utilisée pour prédire les performances et aider la conception de systèmes codés. Ce travail met aussi en avant le bon compromis performances/complexité offert par l'égaliseur à retour de décision dans le contexte des communications au-delà de la cadence de Nyquist