Ali Dziri

Performance Analysis in the Downlink of Asynchronous OFDM/FBMC Based Multi-Cellular Networks

This paper provides a theoretical performance evaluation of the downlink of asynchronous orthogonal frequency division multiplexing (OFDM) and filter bank based multicarrier (FBMC) cellular radio communication systems. An accurate derivation, for the interference caused by the timing synchronization errors in the neighboring cells, is developed. The multipath effects on the interfering and desired signal are also considered. Based on computing the moment generating functions of the interference power, exact expressions are derived for average error rates of OFDM and FBMC systems considering the frequency correlation fading in the case of block subcarrier assignment scheme.

The Impact of Timing Synchronization Errors on the Performance of OFDM/FBMC Systems

Interference at the radio receiver is a key source of degradation in quality of service of wireless communication systems. In this paper, we address the impact of imperfect inter-cell synchronization on the performance of orthogonal frequency division multiplexing (OFDM) and filter bank based multicarrier (FBMC) multi-cellular networks. Based on computing the moment generating functions of the asynchronous interference power, a useful analytical method for computing the average error rates is derived considering the frequency correlation fading between adjacent interfering subcarriers.

Symbol error probability analysis of the Decode and Forward relaying over the composite fading multipath/shadowing channels

In this paper, we analyze the performance of cooperative diversity using adaptive Decode and Forward (DF) relaying over independent non identical flat composite fading channels which include multipath fading and shadowing simultaneously. We have considered the generalized-K model which is very versatile and accurately approximates many of the commonly used channel models as Nakagami-m, log-normal distribution and the mixture of the two distributions for the composite fading. We give an analytical expression for the symbol error probability of the proposed scenario and analyze its dependence on the channel parameters. We assume in our context, that the relay decides independently whether or not to forward the signal to the destination based on the received signal quality. Simulation results are in good agreement with our theoretical analysis.

A New Theoretical Approach of Wavelet-Based Multifractal Characterization of HF Channel Scattering Function: Theoretical and Physical Interpretations

In high-frequency (HF) ionospheric communications, the dynamic nature of the high-latitude ionosphere creates small-scale ionospheric irregularities capable of scattering HF radio waves. In addition, there are large-scale irregularities which may be identified using some specific methods. However, small-scale irregularities cannot be easily identified and characterized. The aim of this paper is to introduce a new wavelet-based multifractal dimension mapping approach for the identification and the quantification of the small-scale irregularities. Numerical results show the improvement of the proposed methods compared to those obtained by the classical Legendre multifractal analysis. In our analysis, we have used the scattering function as a tool for the HF channel characterization. Our analysis deals with experimental scattering functions measured during the solar eclipse on August 11, 1999.

Outage probability analysis of the decode and forward relaying over the composite fading multipath/shadowing channels

Cooperative diversity is one of the promising solutions to overcome the channel impairments and provide high data rate coverage. It has been studied for different channel fading as Rayleigh, Rice and Nakagami-m. Nevertheless, for a decode and forward relaying over composite fading including simultaneously multipath and shadowing, outage results have ever appeared. Using the Nakagami probability density function (pdf) to model multipath fading and the Gamma pdf to model shadowing has led to the generalized-K model for composite fading. This paper gives an analytical expression of the outage probability of the Decode and Forward cooperative technique over the generalized-K fading channel. Simulation results are in good agreement with our theoretical analysis.

SDR based prototype for filter bank based multi-carrier transmission

This paper investigates the design of a potential Software Defined Radio (SDR) based prototype for Filter Bank based Multi-Carrier Transmission. It allows for implementing and testing transmitter and receiver in real-time on Universal Software Radio Peripheral (USRP) by using two USRP boards. Additionally, an implementation of some classic channel models in a separate USRP board has been used for emulating a propagation channel. The presented prototyping system supports FBMC waveform but also Orthogonal Frequency Division Multi-carriers(OFDM) one using MATLAB routines. With this motivation, we propose a study on real-time decoding of Offset Quadrature Amplitude Modulation FBMC (OQAM-FBMC) radio frames. In this system, data recovery at the receiver is very sensitive to time and frequency synchronization of the frames. This problem was addressed in many theoretical research works. However, considering its practical aspects in the context of a realtime radio transmission, a signal processing block is required to satisfy a trade-off between the accuracy and the latency. We especially recognize different limits, imposed by both hardware and software entities, to the real-time system.

Multi-hop LEACH based cross-layer design for large scale wireless sensor networks

The need for energy-efficient routing and data gathering protocols in large-scale environments becomes very challenging. Hierarchical routing in WSNs is a very important topic. It has been widely investigated relative to energy efficiency based routing protocols. LEACH (Low Energy Adaptive Clustering Hierarchy algorithm) is the pioneering cluster routing protocol in WSNs. However, it is not suitable for large scale network and wireless channel conditions are ignored during packet forwarding. To address this issue, we proposed a novel multi-hop clustering cross layer protocol based on LEACH. It considers both the SNR of different links and the residual energy of sensor nodes. Simulation results in terms of the average energy consumption, the network lifetime and the Packet Delivery Ratio show clearly the outperformance of the proposed algorithm versus the conventional LEACH.

Relevant CIR parameters selection for fingerprinting based location algorithm

This paper investigates the relevance of Channel Impulse Response (CIR) parameters for fingerprint based localization algorithm. We consider in this study a WLAN environment where a Multi-Layer Neural Network (MLNN) learns off-line the location from the location-dependent parameters of the CIR. Then, it calculates on-line the accurate position of a mobile station from given fingerprints. More importantly, an advanced study is conducted to identify the relevant parameters of CIR to be used as fingerprints which offer lower complexity and high location accuracy.

Ultra Wide Band Audio Visual PHY IEEE 802.15.3c for WMSNs

In order to retrieve multimedia content like video and audio at indoor environments, wireless multimedia sensor networks have recently emerged as a good solution. Moreover, Ultra Wide Band technology (UWB) can provide high data rates to transfer the multimedia content in a point-to-point mode. In this paper, we explain the features of UWB technology and investigate the performance of the IEEE 802.15.3c standard in terms of Bit Error Rate (BER) against Signal to Noise Ratio (SNR). The Audio Visual Physical (AV PHY) mode has been implemented and simulated and our results show that encoded AV PHY outperforms the uncoded AV PHY for high and low Convolutional encoder rates. Finally, we emphasized the quality improvements with different UWB standard parameters (coding and modulation) in the context of JPEG image compression.

Performance analysis of AODV and AOMDV over SMAC and IEEE 802.15.4 in Wireless Multimedia Sensor Network

Wireless Multimedia Sensor Networks (WMSNs) have recently gained a great attention of the research community as potential solutions for wide range of applications. However, they are subject to strict constraints due to their limited energy, limited processing capacities in contrast to the huge video data rate to be transmitted. To tackle with this challenge, we investigate in this paper, various protocols dedicated to the WMSNs in each layer aiming to reduce the amount of video data using powerful video encoder or/and reduce the energy consumption by increasing the life cycle of each node and consequently the life cycle of the whole network. Specifically, we consider the protocols of the application, network, and MAC layers. We have used the NS-2 framework, in which we have added the H264 encoder and decoder as application layer protocol. We have used the IEEE 802.15.4 and the SMAC protocols for the MAC layer, and the AODV and the AOMDV for the network layer. The obtained results are evaluated by the dead nodes number, the energy consumption and the Peak Signal to Noise Ratio (PSNR) for the video decoding quality.