A general overview of cyclic transmultiplexers with cyclic modulation: Implementation and angular parametrization.

31 pages.This preprint provides a general framework for cyclic transmultiplexers (TMUXs) with cyclic modulation. This TMUX also corresponds to a multicarrier modulation system of the Filtered MultiTone (FMT) type where the linear convolution is replaced by a cyclic one, hence the name Cyclic Block FMT (CB-FMT). In this preprint we present the Perfect Reconstruction (PR) conditions in the time and frequency domains. A duality theorem is proved showing that each PR solution in the frequency domain is connected to a dual PR solution in the time domain. Then, two decomposition theorems are established leading to modular implementations of the cyclic TMUX. For one of this implementation we provide an angular parametrization that only involves angles corresponding to independent parameters. Finally, a procedure to reconstruct the prototype function from all the elementary blocks of the modular implementation is described step-by step

The Alamouti Scheme with CDMA-OFDM/OQAM

This paper deals with the combination of OFDM/OQAM with the Alamouti scheme. After a brief presentation of the OFDM/OQAM modulation scheme, we introduce the fact that the well-known Alamouti decoding scheme cannot be simply applied to this modulation. Indeed, the Alamouti coding scheme requires a complex orthogonality property; whereas OFDM/OQAM only provides real orthogonality. However, as we have recently shown, under some conditions, a transmission scheme combining CDMA and OFDM/OQAM can satisfy the complex orthogonality condition. Adding a CDMA component can thus be seen as a solution to apply the Alamouti scheme in combination with OFDM/OQAM. However, our analysis shows that the CDMA-OFDM/OQAM combination has to be built taking into account particular features of the transmission channel. Our simulation results illustrate the 2×1 Alamouti coding scheme for which CDMA-OFDM/OQAM and CP-OFDM are compared in two different scenarios: (i) CDMA is performed in the frequency domain, (ii) CDMA is performed in time domain

A simple commutativity condition for block decimators and expanders

5 pages.International audienceCommutativity rules are essential for building multirate signal processing systems. In this short and self-contained paper, we focus on theinterchangeability of block decimators and expanders. We, formally, prove that commutativity between these two operators is possible if and only if the data blocks are of an equal length corresponding to the greatest common divisor of the integer decimation and expansion factors

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

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

Allocation de débit à faible complexité dans les systèmes OFDM en présence de contraintes spectrales

National audienceCet article traite de la maximisation du débit dans les systèmes OFDM soumis à des contraintes de limitation de la puissance. Nous proposons un algorithme d'allocation glouton dans lequel le vecteur de bits initial est la discrétisation par arrondi de la solution "Water-Filling" du problème continu associé. Nous montrons théoriquement que ce vecteur est "efficace", c'est-àdire qu'il n'existe pas de mouvement d'un bit d'une sous-porteuse à l'autre qui réduise la puissance totale utilisée. Les résultats de simulation montrent l'efficacité de l'algorithme proposé : le débit réalisable est maximisé avec une réduction significative du coût de calcul par rapport à des algorithmes de référence de la littérature

A Computationally Efficient Discrete Bit-Loading Algorithm for OFDM Systems Subject to Spectral-Compatibility Limits

International audienceThis paper considers bit-loading algorithms to maximize throughput under total power and spectral mask constraints in interference-free OFDM systems. The contribution is twofold. First, we propose a simple criterion to switch between two wellknown algorithms from the literature: the conventional Greedy and Greedy-based bit-removing (with maximum allowable bit loading initialization) algorithms. Second, we present a new lowcomplexity loading algorithm that exploits the bit vector obtained by rounding the water-filling algorithm solution to the associated continuous-input rate maximization problem as an efficient initial bit vector of the Greedy algorithm.We theoretically prove that this bit vector has two interesting properties. The first one states that it is an efficient bit vector, i.e., there is no movement of a bit from one subcarrier to another that reduces the total used power. The second one states that the optimized throughput, starting from this initial bit vector, is achieved by adding or removing bits on each subcarrier at most once. Simulation results show the efficiency of the proposed algorithm, i.e., the achievable throughput is maximized with significant reduction of computation cost as compared to many algorithms in the literature

On the study of faster-than-Nyquist multicarrier signaling based on frame theory

Multicarrier transmissions are classically based on undercomplete or exact Weyl-Heisenberg Riesz (biorthogonal or orthogonal) bases implemented thanks to oversampled filter-banks. This can be seen as a transmission below the Nyquist rate. However, when overcomplete Weyl-Heisenberg frames are used, we obtain a “faster-than-Nyquist” (FTN) system and it is theoretically impossible to recover exactly transmitted symbols using a linear receiver. Various studies have shown the interest of this high density signaling scheme as well as practical implementations based on trellis and/or iterative decoding. Nevertheless, there is still a lack of theoretical justifications with regard to pulse design in the FTN case. In this paper, we consider a linear transceiver operating over an additive white Gaussian noise channel. Using the frame theory and simulation results, we show that the mean squared error (MSE) is minimized when tight frames are used

Influence of Interference in MIMO Power Line Communication Systems

International audienceFor a few years, MIMO technique has been considered as the key to increase the data rate in the next generation of power line communications. The HomePlug AV2 and ITU-T G.9963 technologies exploit the MIMO scheme to increaseboth data rate and coverage. In this paper, an improvement of MIMO-PLC modeling is derived and the analytic formula of the interference is developed. Based on the interference analysis, the signal to interference plus noise ratio (SINR) is calculated and compared to the signal to noise ratio (SNR). Finally, the degradation of system performance in terms of capacity due to the interference is shown

On the high energy proton spectrum measurements

The steepening of the proton spectrum beyond 1000 GeV and the rise in inelastic cross sections between 20 and 600 GeV observed by the PROTON-1-2-3 satellite experiments were explained by systematic effects of energy dependent albedo (backscatter) from the calorimeter