Les tests en cascade pour la correction des erreurs impulsives et la réduction du PAPR dans le contexte d'Hiperlan2

Dans ce papier, nous proposons une structure en cascade pour améliorer l'algorithme de correction de bruit impulsif que nous avons déjà présenté dans [6]. Cette nouvelle structure permet une implantation facile et plus fiable (plusieurs paramètres peuvent être obtenus théoriquement plutôt que par simulation). Nous prouvons également que cet algorithme de décodage peut être appliqué pour la réduction du niveau de PAPR (Peak Average Power Rate). L'efficacité de cette technique est corroborée par simulations dans le contexte d'Hiperlan2

CGU-frame-based representations and their connection with Reed-Solomon and DCT/DST coding schemes

We investigate the use of overcomplete frame representations to correct errors occurring over burst-based transmission channels or channels leading to isolated errors. We show that when the overcomplete signal representation is based on a class of frames, called cyclic geometrically uniform (CGU) finite frames, the family of frames containing finite harmonic frames (both in C-M and R-M), this representation becomes equivalent to a Reed-Solomon (RS) coding scheme. Hence, introducing an RS decoding procedure at the receiver, leads to remove the errors introduced by the transmission channel and consequently results in a quasi-perfect reconstructed signal. The advantage of this approach is to exploit the RS coding scheme without using it explicitly at the transmitter, which Would lead to a robust and low complexity transmission. Furthermore, we prove that the discrete cosine transform (DCT) coding is a special case of CGU-frame-based representations and this property holds also true for the discrete sine transform (DST) coding scheme. Simulation results are presented to confirm our claims. Copyright (C) 2008 John Wiley & Soils, Ltd

Efficient POPS-OFDM waveform design for future wireless communication systems

WOS: 000459697700017Future wireless networks are required to offer new applications and services, which will experience high dispersions in time and frequency, incurred mainly by coarse synchronization. Coarse synchronization is induced by signaling overhead reduction and dictated by the tremendous optimization of the radio interface efficiency. It is expected to dramatically damage waveform orthogonality in conventional orthogonal frequency-division multiplexing (OFDM) systems and to result in oppressive intercarrier interference (ICI). To alleviate the degradation in performance caused by ICI, the concept of nonorthogonal multiplexing has been promoted, as a serious alternative to strict orthogonal multiplexing, for guaranteeing the OFDM benefits without requiring high-level synchronization. Within this nonorthogonal multiplexing framework, ping-pong optimized pulse shaping-OFDM (POPS-OFDM) has been introduced as a powerful tool to efficiently design waveforms, which withstand future multicarrier systems' dispersion impairments. In this paper, we investigate the discrete time version of the POPS-OFDM approach and study its sensitivity and robustness against estimation and synchronization errors. Based on numerical results, we show that POPS-OFDM provides an important gain in the signal-to-interference ratio, typically higher than 5 dB, with respect to conventional OFDM. We also demonstrate that POPS-OFDM brings an increased robustness against synchronization errors and ensures a dramatic reduction in out-of-band emissions, enabling flexible and improved spectrum utilization.Scientific and Technological Research Council of Turkey through Bideb 2232 Program [115C136]The work of T. Baykas was supported by the Scientific and Technological Research Council of Turkey through Bideb 2232 Program under Grant 115C136

Les Codes Reed-Solomon pour la correction des erreurs impulsives dans les systèmes multiporteuses

PARIS-Télécom ParisTech (751132302) / SudocSudocFranceF

PAPR Reduction Scheme In MIMO-OFDM Systems With Efficient Embedded Signaling

Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) is a promising transmission scheme for high performance broadband wireless communications. However, this technique suffers from a major drawback which is the high Peak to Average Power Ratio (PAPR) of the output signals. In order to overcome this issue, several methods that require the transmission of explicit Side Information (SI) bits have been proposed. In fact, the transmitted bits must be channel-encoded as they are particularly critical to the performance of the considered OFDM system. This channel-encoding highly increases the system complexity and also decreases the transmission data rate. For these reasons, we propose in this paper, two robust blind techniques that embed the (SI) implicitly into the OFDM frame. First, we investigate a new technique referred as Blind Space Time Bloc Codes (BSTBC) that is inspired from the conventional Selected Mapping (SLM) approach. This technique banks on an adequate embedded signaling that mainly consist on a specific Space Time Bloc Codes (STBC) patterns and a precoding sequences codebook. Second, in order to improve the signal detection process and the PAPR gain, we propose a new efficient combined Blind SLM-STBC (BSLM-STBC) method. Both methods have the benefit of resulting in an optimized scheme during the signal estimation process that is based on the Max-Log-Maximum A Posteriori (MAP) algorithm. Finally, the obtained performance evaluation results show that our proposed methods result in a spectacular PAPR reduction and furthermore lead to a perfect signal recovery at the receiver side.Comment: This paper has been withdrawn by the author due to loss of information

How Much FBMC/OQAM Is Better than FBMC/QAM? A Tentative Response Using the POPS Paradigm

A major trend of the current research in 5G is to find well time and frequency localized waveforms, dedicated to non-orthogonal wireless multi-carrier systems. The ping-pong optimized pulse shaping (POPS) paradigm was proposed as a powerful technique to generate a family of waveforms, ensuring an optimal signal to interference plus noise ratio (SINR) at the receiver. In this paper, we derive, for the first time, the analytical expression of the SINR for FBMC/OQAM systems. We then adopt the POPS algorithm in the design of optimum transmit and receive waveforms for FBMC/OQAM, with respect to the SINR criterion. For relatively high dispersions, numerical results show that the optimized waveforms provide a gain of 7 dB, in terms of SINR, compared to the PHYDYAS waveform. They also show that the obtained waveforms offer better out-of-band (OOB) emissions with regard to those of the IOTA waveform. Furthermore, we notice that FBMC/OQAM systems present a gain of 4 dB in SINR, compared to FBMC/QAM systems, when both operate at their time-frequency lattice critical densities. However, FBMC/QAM systems can guarantee, with a reduced computational complexity, a comparable performance to FBMC/OQAM systems, in terms of SINR, when their spectral efficiency is relatively reduced by less than 5%

A Necessary Condition on the Location of Pilot Tones for Maximizing the Correction Capacity in OFDM Systems

International audienc

Codage correcteur d'erreur dans le corps des complexes et systèmes multiporteuses

Ce papier présente une méthode élégante pour la correction des erreurs impulsives dans les systèmes OFDM. Il existe une analogie entre ces systèmes OFDM et les codes Reed Solomon. Ceci montre que si un signal est envoyé sur un canal contenant un bruit gaussien de faible amplitude et un bruit impulsif alors ce bruit impulsif peut être corrigé par une procédure similaire aux techniques de décodage canal classique. Nous expliquons tout d'abord ce résultat dans un cas simple dont l'intérêt est principalement d'ordre théorique. Généralement, on envoie des pilotes utilisés pour la synchronisation ou l'estimation du canal. Ces symboles pilotes sont répartis de façon aléatoire dans la séquence à émettre. Notre apport dans cet article est d'utiliser ces pilotes pour corriger les erreurs impulsives. Nous avons montré que la capacité de correction dépend essentiellement de l'emplacement de ces pilotes dans la séquence. L'efficacité de cette méthode est corroborée par les simulations présentées dans le contexte pratique d'Hiperlan2