Blind Carrier Phase Recovery for General 2{\pi}/M-rotationally Symmetric Constellations

This paper introduces a novel blind carrier phase recovery estimator for general 2{\Pi}/M-rotationally symmetric constellations. This estimation method is a generalization of the non-data-aided (NDA) nonlinear Phase Metric Method (PMM) estimator already designed for general quadrature amplitude constellations. This unbiased estimator is seen here as a fourth order PMM then generalized to Mth order (Mth PMM) in such manner that it covers general 2{\Pi}/M-rotationally symmetric constellations such as PAM, QAM, PSK. Simulation results demonstrate the good performance of this Mth PMM estimation algorithm against competitive blind phase estimators already published for various modulation systems of practical interest.Comment: 14 pages, 12 figures, International Journal of Wireless & Mobile Networks (IJWMN

Analysis of Joint Source Channel LDPC Coding for Correlated Sources Transmission over Noisy Channels

In this paper, a Joint Source Channel coding scheme based on LDPC codes is investigated. We consider two concatenated LDPC codes, one allows to compress a correlated source and the second to protect it against channel degradations. The original information can be reconstructed at the receiver by a joint decoder, where the source decoder and the channel decoder run in parallel by transferring extrinsic information. We investigate the performance of the JSC LDPC code in terms of Bit-Error Rate (BER) in the case of transmission over an Additive White Gaussian Noise (AWGN) channel, and for different source and channel rate parameters. We emphasize how JSC LDPC presents a performance tradeoff depending on the channel state and on the source correlation. We show that, the JSC LDPC is an efficient solution for a relatively low Signal-to-Noise Ratio (SNR) channel, especially with highly correlated sources. Finally, a source-channel rate optimization has to be applied to guarantee the best JSC LDPC system performance for a given channel

CONCEPTION DES ONDELETTES NON LINEAIRES ET CORRESPONDANCE DU SCHEMA DE LIFTING AVEC LES ONDELETTES DE SECONDE GENERATION POUR UN CODEUR VIDEO SCALABLE

Cet article s'inscrit dans le cadre de la transmission de données vidéo sur réseaux. Dans ce contexte, les standards de codage vidéo doivent fournir une compression efficace du signal vidéo ainsi que la fonctionnalité de scalabilité permettant d'adapter le flux compressé aux ressources disponibles.Les progrès récents sur les schémas de codage vidéo ont permis l’apparition d’une nouvelle génération de codeurs vidéo scalables par ondelettes dont l’efficacité est comparable à celle des meilleurs codecs hybrides. Ces schémas sont qualifiés de « t + 2D » et reposent sur l’utilisation d’une transformée en ondelettes appliquée le long du mouvement des images afin d’exploiter leur redondance temporelle.L'objectif de cet article est de démontrer la méthodologie de correspondance du schéma de lifting avec les ondelettes de seconde génération pour un codeur vidéo scalable.C'est-à-dire on va expliquer comment ce schéma de lifting permet la construction des bases d’ondelettes et des bancs de filtres associés, adaptés aux signaux définis sur un domaine quelconque.Pour cela, on va définir une analyse multirésolution associée aux ondelettes de seconde génération tout en respectant les caractéristiques de base d’un tel schéma de lifting à savoir : la faible complexité, la capacité à générer des transformations adaptatives prenant en compte la structure du signal et la garantie d'inversibilité de la transformation, indépendamment de la nature des opérateurs de prédiction et de mise à jour utilisés

A generalised wideband space-time MIMO channel simulator based on the geometrical multi-radii one-ring model

International audienceThis paper extends the geometrical one-ring multi- input multi output (MIMO) channel model for a frequency flat fading process in a land mobile radio system with respect to frequency-selectivity. Our approach enables the design of efficient simulation models for space-time MIMO channels under isotropic scattering conditions for any numbers of transmit and receive antennas. A simulation study is performed into the space- time cross correlation to gain understanding of the modification of some relevant parameters. A conventional four transmit four receive 4 x 4 MIMO radio channel is analyzed

Adaptive quasi-orthogonal space time block codes using partial feedback in MIMO HSDPA

International audienceHigh Speed Downlink Packet Access (HSDPA) aims to provide peak data rates up to 10.8 Mbps in downlink. This goal is reached by introduction of sophisticated technologies such as adaptative modulation and coding (AMC), Hybrid Automatic Request (HARQ), fast scheduling, and transmit diversity with multiple transmit antennas and receive antennas (MIMO) schemes. In this paper the impact of adaptive HARQ and MIMO space-time block code on the HSDPA system performance is considered. Quasi-orthogonal space-time block codes (QSTBC) for multiinput multi-output (MIMO) fading channels for more than two transmit antennas is proposed. It has been shown that these codes can not achieve full diversity at full rate. We present a simple feedback scheme for rich scattering MIMO channels that improves the coding gain and diversity of a QSTBC for 2n transmit antennas with n = 3, 4,L. The case of n = 2 is studied in details. The relevant channel state information is sent back from the receiver to the transmitter quantized one or two bits per code block. In this way, signal transmission with an improved coding gain diversity order is achieved

MIMO Spectral Efficiency over Energy Consumption Requirements: Application to WSNs

International audienceThis paper presents the evaluation of the "capacity to the total energy consumption per bit ratio" of multiple antennas systems with distributed fashion. We propose an adequate geometric channel modeling for the wireless communication system which operates in indoor propagation environment with scatterers. The channel model is derived in function of both the line of sight (LOS) and the non line of sight (NLOS) components. The aim of this paper is to study the limits in the gain concerning the capacity to the total energy consumption ratio when additional antennas are implemented in the communication system. To do so, we have evaluated by simulations both the capacity and the total energy consumption per bit. Then, we have determined the capacity to the total energy consumption ratio. Finally, the computational capac- ity to the total energy ratio is obtained for different system configurations. We have shown that the gain in capacity in- creases with the number of antennas but it stills be limited by the total energy consumption. The limits for increasing the number of transmit antennas are determined in function of the separation distances between the transmitter and the receiver sides of the communication system. Optimal power allocation strategy via water-filling algorithm has been carried out for evaluating the capacity to energy ratio. We find by simulation that optimal power allocation brings a gain in the addressed metric reaching a level of about 1.7 at transmit signal to noise ratio of 8 dB if comparing to the case when transmit energy is equally split among transmit antennas

Inter-node compression with LDPC joint source–channel coding for highly correlated sources

This paper investigates a new communication system where two nodes want to disseminate highly correlated contents to a single destination and can be applied for densely deployed wireless sensors networks applications. Motivated by their capacity-achieving performance and existing practical implementations, the proposed communication scheme is fully based on Low-Density Parity-Check (LDPC) codes for data compression and channel coding. More specifically, we consider a network of two correlated binary sources with two orthogonal communication phases. Data are encoded at the first source with an LDPC channel code and broadcast in the first phase. Based on the first source received data, the second source computes the correlation vector and applies a Joint Source–Channel (JSC) LDPC code, which output is communicated in the second phase. At the receiver, the whole network is mapped on a joint factor graph over which an iterative message-passing joint decoder is proposed. The aim of the joint decoder is to exploit the residual correlation between the sources for better estimation. Simulation results are investigated and compared to the theoretical limits and to an LDPC-based distributed coding system where no inter-node compression is applied

Low-complexity chase-like decoding of variable-length codes

International audienceMost source coding standards (voice, audio, image and video) use Variable-Length Codes (VLCs) for compression. However, the VLC decoder is very sensitive to transmission errors in the compressed bit-stream. Previous contributions, using a trellis description of the VLC codewords to perform soft decoding, have been proposed. Significant improvements are achieved by this approach when compared with prefix decoding. Nevertheless, for realistic VLCs, the complexity of the trellis technique becomes intractable. In this paper, we propose a soft-input VLC decoding method using an a priori knowledge of the lengths of the source-symbol sequence and the compressed bit-stream with Maximum A Posteriori (MAP) sequence estimation. Performance in the case of transmission over an Additive White Gaussian Noise (AWGN) channel is evaluated. Simulation results show that the proposed decoding algorithm leads to significant performance gain in comparison with the prefix VLC decoding besides exhibiting very low complexity. A new VLC decoding method generating additional information regarding the reliability of the bits of the compressed bit-stream is also proposed. We consider the serial concatenation of a VLC with two types of channel code and perform iterative decoding. Results show that, when concatenated with a recursive systematic convolutional code (RSCC), iterative decoding provides remarkable error correction performance. In fact, a gain of about 2.3 dB is achieved, in the case of transmission over an AWGN channel, with respect to tandem decoding. Second, we consider a concatenation with a low-density parity-check (LDPC) code and it is shown that iterative joint source/channel decoding outperforms tandem decoding and an additional coding gain of 0.25 dB is achieved